WORKING ROBOT

Abstract

A working robot may be configured to move and work autonomously. The working robot may include a robot body including a base and a bumper supported by the base, a working unit supported by the base, a movement mechanism configured to move the base, a movement motor configured to drive the movement mechanism, a first detection unit configured to detect a force that the bumper receives or displacement of the bumper relative to the base, a second detection unit configured to detect an angular velocity of the base or a state of the movement motor, and a control unit. The control unit may be configured to determine, based on a detection result detected by the first detection unit and a detection result detected by the second detection unit, whether the movement of the working robot is hindered by an obstacle.

Description

REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2023-175348 filed on Oct. 10, 2023. The entire content of the priority application is incorporated herein by reference.

TECHNICAL FIELD

The technology disclosed herein relates to a working robot.

BACKGROUND ART

Japanese Patent Application Publication No. H09-325812 describes a working robot configured to move and work autonomously. The working robot includes a robot body including a base and a bumper supported by the base; a working unit supported by the base; a movement mechanism configured to move the base; a movement motor configured to drive the movement mechanism; a first detection unit configured to detect a force that the bumper receives or displacement of the bumper relative to the base; and a control unit. The control unit is configured to determine, based on a detection result detected by the first detection unit, whether movement of the working robot is hindered by an obstacle.

SUMMARY

A control unit of a working robot may cause the working robot to perform, in response to determining that the movement of the working robot is hindered by an obstacle, a circumvention action to circumvent the obstacle. If accuracy of this determination on whether the movement of the working robot is hindered by an obstacle or not is low, it would be harder for the working robot to circumvent the obstacle. For example, the working robot may take longer to circumvent the obstacle. This may hinder a smooth progress of work performed by the working robot. The disclosure herein provides a technology that allows for a smooth progress of work performed by a working robot.

A working robot disclosed herein may be configured to move and work autonomously. The working robot may comprise a robot body including a base and a bumper supported by the base, a working unit supported by the base, a movement mechanism configured to move the base, a movement motor configured to drive the movement mechanism, a first detection unit configured to detect a force that the bumper receives or displacement of the bumper relative to the base, a second detection unit configured to detect an angular velocity of the base or a state of the movement motor, and a control unit. The control unit may be configured to determine, based on a detection result detected by the first detection unit and a detection result detected by the second detection unit, whether movement of the working robot is hindered by an obstacle.

According to the configuration above, the control unit of the working robot determines whether the movement of the working robot is hindered by an obstacle, not only based on the force that the bumper receives or the displacement of the bumper relative to the base, but also based on the angular velocity of the base or the state of the movement motor. This improves the accuracy of the determination on whether the movement of the working robot is hindered by an obstacle, and thus the working robot can easily circumvent the obstacle. The configuration above allows for a smooth progress of work performed by the working robot.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an exemplary use of a robotic mower 2 according to a first embodiment.

FIG. 2 shows a left side view of the robotic mower 2 according to the first embodiment.

FIG. 3 shows a rear view of the robotic mower 2 according to the first embodiment.

FIG. 4 schematically shows a configuration of the robotic mower 2 according to the first embodiment.

FIG. 5 schematically shows a configuration near a collision detection sensor 66 of the robotic mower 2 according to the first embodiment.

FIG. 6 schematically shows a configuration near a lift detection sensor 68 of the robotic mower 2 according to the first embodiment.

FIG. 7 shows a flowchart of an autonomous operation executed by a control unit 8 of the robotic mower 2 according to the first embodiment when an automatic height adjustment function is enabled.

FIG. 8 schematically shows a threshold table TT stored in a memory 36 of the control unit 8 of the robotic mower 2 according to the first embodiment.

FIG. 9 shows a flowchart of the autonomous operation executed by the control unit 8 of the robotic mower 2 according to the first embodiment when the automatic height adjustment function is disabled.

FIG. 10 shows a flowchart of a process executed by the control unit 8 while the robotic mower 2 according to the first embodiment is in autonomous operation.

FIG. 11 shows a flowchart of a process executed by a control unit 8 while a robotic mower 202 according to a second embodiment is in autonomous operation.

FIG. 12 shows a flowchart of a process executed by a control unit 8 while a robotic mower 302 according to a third embodiment is in autonomous operation.

FIG. 13 shows a flowchart of an autonomous operation executed by a control unit 8 of a robotic mower 402 according to a fourth embodiment when the automatic height adjustment function is enabled.

DESCRIPTION

Representative, non-limiting examples of the present disclosure will now be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing aspects of the present teachings and is not intended to limit the scope of the present disclosure. Furthermore, each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved working robots as well as methods for using and manufacturing the same.

Moreover, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the present disclosure in the broadest sense, and are instead taught merely to particularly describe representative examples of the present disclosure. Furthermore, various features of the above-described and below-described representative examples, as well as the various independent and dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

In one or more embodiments, the control unit may be configured to execute a first hindrance determination process of determining, based on at least the detection result detected by the first detection unit, whether the movement of the working robot is hindered by the obstacle, a circumvention process of controlling the movement motor such that the working robot performs a circumvention action to circumvent the obstacle after the control unit has determined that the movement of the working robot is hindered by the obstacle in the first hindrance determination process, and a second hindrance determination process of determining, based on at least the detection result detected by the second detection unit, whether the movement of the working robot is hindered by the obstacle while the working robot is performing the circumvention action.

According to the configuration above, in response to the working robot (specifically, the bumper) bumping into an obstacle, the control unit determines that the movement of the working robot is hindered by the obstacle and then causes the working robot to perform the circumvention action. While the working robot is performing the circumvention action, a part of the working robot other than the bumper may bump the obstacle and the working robot may thereby be hindered from moving. In this case, the detection result from the first detection unit (the force received by the bumper or displacement of the bumper relative to the base) does not show any particular indication that the movement of the working robot is hindered by the obstacle. That is, if the control unit determines whether the movement of the working robot is hindered by an obstacle or not based only on the detection result from the first detection unit while the working robot is performing circumvention action, the determination result may be erroneous. By contrast, according to the configuration above, the control unit determines, based on at least the detection result from the second detection unit, whether the movement of the working robot is hindered by the obstacle while the working robot is performing the circumvention action. This prevents the erroneous result of the determination on whether the movement of the working robot is hindered by an obstacle. Thus, the configuration above allows for accurate determination on whether the movement of the working robot is hindered by an obstacle.

In one or more embodiments, the circumvention action may include a turning action in which the working robot turns.

The configuration above can make the circumvention action relatively complex.

In one or more embodiments, the circumvention action may include a straight action in which the working robot moves straight.

If the circumvention action includes only the turning action, the working robot may not move away from an obstacle at all after having bumped it. In this case, the working robot takes time to circumvent the obstacle, which may interrupt smooth progress of the work performed by the working robot. According to the configuration above, the circumvention action includes the straight action, and thus the working robot can move away from an obstacle after bumping it. This reduces the time the working robot takes to circumvent the obstacle and facilitates smooth progress of the work performed by the working robot.

In one or more embodiments, the state of the movement motor may include a current flowing in the movement motor. The second detection unit may include a motor current detector configured to detect the current flowing in the movement motor.

The movement motor experiences a larger load than usual when running while the movement of the working robot is hindered by an obstacle, due to the blocking by the obstacle. In this case, a current flowing in the movement motor is expected to be larger than usual. In the configuration above, the control unit can estimate a load on the movement motor based on a current flowing in the movement motor while the movement motor is in operation and determine whether the movement of the working robot is hindered by an obstacle or not.

In one or more embodiments, in a case where a detection value detected by the motor current detector remains at or above a predetermined current value for a predetermined duration or longer, the control unit may determine that the movement of the working robot is hindered by the obstacle.

In response to determining that the movement of the working robot is hindered by an obstacle, the control unit may cause the working robot to perform the circumvention action to circumvent the obstacle, but sometimes the working robot can circumvent the obstacle just by operating normally without performing the circumvention action. Thus, if the control unit determines that the movement of the working robot is hindered by an obstacle upon when the detection value of the motor current detector reaches the predetermined current value or above, the circumvention action may be performed unnecessarily. According to the configuration above, in the case where the detection value detected by the motor current detector remains at or above the predetermined current value for the predetermined duration or longer, the control unit determines that the movement of the working robot is hindered by an obstacle. That is, the circumvention action is performed only if the working robot remains hindered from moving by an obstacle for a certain period of time. This prevents the circumvention action from being performed unnecessarily. This allows for smooth progress of the work performed by the working robot.

In one or more embodiments, the working unit may comprise a blade configured to mow a lawn. The working robot may function as a robotic mower.

According to the configuration above, the work performed by the robotic mower can progress smoothly.

First Embodiment: Robotic Mower 2

As shown in FIG. 1, a working robot according to this embodiment is for example a robotic mower 2 used within premises 100 where lawn is growing. Within the premises 100, for example, a house 102, a pond 104, and a path 106 are located. Within the premises 100, a charging station 110 connected to an external power supply (e.g., a commercial power supply) and a wire 112 defining a working region WA for the robotic mower 2 are also located. The working region WA herein is a region surrounded by the wire 112. The robotic mower 2 can detect the position of the wire 112 and autonomously move not to go out of the working region WA in which the robotic mower 2 is present. Thus, the robotic mower 2 can mow the lawn while moving thereon and avoiding the house 102, the pond 104, and the path 106.

As shown in FIGS. 2, 3, and 4, the robotic mower 2 comprises a robot body 4, a power unit 6, a control unit 8, an input unit 10, a communication unit 12, a display unit 14, an alarm unit 16, a movement unit 18, a working unit 20, a height adjustment unit 22, and a detection unit 24. The power unit 6, the control unit 8, the input unit 10, the communication unit 12, the display unit 14, the alarm unit 16, the movement unit 18, the working unit 20, the height adjustment unit 22, and the detection unit 24 are all supported by the robot body 4.

As shown in FIG. 2, the robot body 4 comprises a base frame 26 and a body 28 supported by the base frame 26. The body 28 covers the base frame 26 from above. The body 28 is supported by the base frame 26 such that the body 28 is movable relative to the base frame 26 in a front-rear direction, an up-down direction, and a right-left direction. Usually, the body 28 is retained in the position shown in FIG. 2 by a spring, etc.

The power unit 6 shown in FIG. 4 is configured to supply electric power to the units of the robotic mower 2 via a power supply circuit 38 of the control unit 8. The power unit 6 comprises a rechargeable battery 30 such as a lithium-ion battery and a charging interface 32 electrically connected to the battery 30. The nominal capacity of the battery 30 is for example 5.0 Ah. The nominal voltage of the battery 30 is for example 18 V. The robotic mower 2 is configured to dock with the charging station 110 (see FIG. 1) via the charging interface 32. When the robotic mower 2 is docked with the charging station 110, the battery 30 is recharged with electric power supplied from the charging station 110. The battery 30 may be charged in a wired manner. Specifically, a terminal of the charging station 110 and a terminal of the charging interface 32 may be connected to each other to charge the battery 30. Alternatively, the battery 30 may be charged in a wireless manner. Specifically, a transmitting coil of the charging station 110 may generate an induced electromotive force in a receiving coil of the charging interface 32 to charge the battery 30.

The control unit 8 comprises a processor 34, a memory 36, and the power supply circuit 38. The memory 36 comprises a ROM, a RAM, etc. A program to autonomically control the robotic mower 2 is stored in the ROM. Various signals inputted to the control unit 8 and various data (e.g., flag) created during processes executed by the processor 34 are temporarily stored in the RAM. The processor 34 is configured to control the robotic mower 2 by executing processes according to information stored in the memory 36. Settings related to the robotic mower 2 are also stored in the memory 36. The settings related to the robotic mower 2 include for example a setting related to a working time slot of the robotic mower 2. The working time slot of the robotic mower 2 here means a time slot in which the robotic mower 2 is allowed to work. By setting a working time slot, the robotic mower 2 is prevented from working in a time slot in which the user does not want the robotic mower 2 to work (e.g., during the night). The settings related to the robotic mower 2 also include a setting related to height adjustment for a blade 46. The setting related to height adjustment for the blade 46 includes enablement/disablement of an automatic height adjustment function to automatically adjust a height level h (see FIG. 2) of the blade 46 during an autonomous operation, which will be described later. The setting related to height adjustment for the blade 46 further includes settings on an initial height level of the blade 46, a target height level of the blade 46, and an area of the working region WA (see FIG. 1), which are required when the automatic height adjustment function is enabled, as well as a setting on a fixed height level of the blade 46, which is required when the automatic height adjustment function is disabled.

The input unit 10 is located on the outer surface of the body 28 (see FIG. 2) and comprises switches, etc. that are manipulatable by the user. The user can perform various input manipulations related to the robotic mower 2 to the input unit 10. The input manipulations here may include, for example, manipulations to switch the main power of the robotic mower 2 between on and off, manipulations to input instructions to the robotic mower 2, manipulations to change the settings related to the robotic mower 2, etc.

The communication unit 12 is an interface for connection to the internet for example via a base station (not shown) for mobile communications (3G, 4G, 5G, etc.) or a router (not shown) installed in the house 102. The control unit 8 is wirelessly communicable with a user's communication terminal (e.g., smartphone) via the communication unit 12. The control unit 8 can thus inform the user of an occurrence of abnormality in the robotic mower 2 through the user's communication terminal. Further, the user can perform various input manipulations related to the robotic mower 2 to the communication terminal as if he/she performed them to the input unit 10.

The display unit 14 is located on the outer surface of the body 28 (see FIG. 2). The display unit 14 comprises for example a display (not shown) configured to display letters and images and/or a light configured to display a state of the robotic mower 2 using chromaticity and/or blinking patterns of light. The state of the robotic mower 2 herein includes for example a state where the battery 30 is being charged, a state where an abnormality is occurring in the robotic mower 2, etc.

The alarm unit 16 comprises for example a buzzer (not shown). The alarm unit 16 is configured to emit a sound to inform an occurrence of abnormality in the robotic mower 2.

The movement unit 18 comprises a pair of a left caster 40L and a right caster 40R, a pair of a left drive wheel 42L and a right drive wheel 42R, and a pair of a left movement motor 44L and a right movement motor 44R. The movement motors 44L, 44R are for example brushless DC motors. The output shafts (not shown) of the movement motors 44L, 44R are coupled to the drive wheels 42L, 42R, respectively. As shown in FIGS. 2 and 3, when the robotic mower 2 is on a ground G, the casters 40L, 40R and the drive wheels 42L, 42R are in contact with the ground G. The movement unit 18 is configured to move the robotic mower 2 forward and rearward as well as turn the robotic mower 2 by driving the movement motors 44L, 44R (see FIG. 4) to rotate the drive wheels 42L, 42R. In this embodiment, regarding the up-down direction perpendicular to the ground G, the direction from the ground G toward the robot body 4 is termed an up direction, and the direction from the robot body 4 toward the ground G is termed a down direction; regarding the right-left direction perpendicular to the up-down direction, the direction from the drive wheel 42R toward the drive wheel 42L is termed a left direction and the direction from the drive wheel 42L toward the drive wheel 42R is termed a right direction; regarding the front-rear direction perpendicular to the up-down direction and the right-left direction, the direction from the drive wheels 42L, 42R toward the casters 40L, 40R is termed a front direction and the direction from the casters 40L, 40R toward the drive wheels 42L, 42R is termed a rear direction.

As shown in FIG. 2, the working unit 20 comprises the blade 46 and a working motor 48. The blade 46 is a substantially circular plate-shaped rotary blade. The working motor 48 is for example a brushless DC motor. The working motor 48 is arranged such that the upper end of its output shaft 50 is located forward of the lower end thereof. The output shaft 50 of the working motor 48 is coupled to the blade 46. The working unit 20 is configured to mow the lawn by driving the working motor 48 to rotate the blade 46.

The height adjustment unit 22 comprises a height adjustment mechanism 52 and a height adjustment motor 54. The height adjustment mechanism 52 comprises an outer tube 58 in which an internal thread is defined and an inner tube 62 in which an external thread 60 is defined. The external thread 60 of the inner tube 62 is screwed with the internal thread 56 of the outer tube 58. The outer tube 58 is supported such that the outer tube 58 is immovable in the up-down direction relative to the base frame 26 and is rotatable about an axis extending in the up-down direction relative to the base frame 26. The inner tube 62 is supported such that the inner tube 62 is movable in the up-down direction relative to the base frame 26 and is nonrotatable relative to the base frame 26. The working unit 20 is fixed to the inner tube 62. The height adjustment motor 54 is for example a brushless DC motor. The output shaft (not shown) of the height adjustment motor 54 is coupled to the outer tube 58 via gear(s), etc. The height adjustment unit 22 is configured to change the position of the inner tube 62 in the up-down direction by driving the height adjustment motor 54 to rotate the outer tube 58. In this, way, the height adjustment unit 22 changes the height level h of the blade 46. In this embodiment, the height level h of the blade 46 is expressed as a distance from the lower end of the blade 46 to the ground G. The height level h of the blade 46 is for example in a range from 10 mm to 80 mm, and in this embodiment, it can vary within a range from 20 mm to 60 mm.

As shown in FIG. 4, the detection unit 24 comprises a wire detection sensor 64, a collision detection sensor 66, a lift detection sensor 68, an angular velocity detection sensor 70, a motor current detection circuit 72, and a battery voltage detection circuit 74.

The wire detection sensor 64 is configured to detect the wire 112 (see FIG. 1). The wire detection sensor 64 is for example a Hall sensor. In this embodiment, a predetermined electric signal is applied to the wire 112 from the charging station 110 (see FIG. 1). Thus, a magnetic signal corresponding to the predetermined electric signal is generated around the wire 112. The wire detection sensor 64 detects this magnetic signal and outputs it to the control unit 8. Based on the signal pattern and/or signal intensity of the magnetic signal detected by the wire detection sensor 64, the control unit 8 determines whether the robotic mower 2 is approaching the wire 112 and/or whether the robotic mower 2 is positioned on the wire 112.

The collision detection sensor 66 is configured to detect a collision of the robotic mower 2 against an obstacle. The collision detection sensor 66 is for example a Hall sensor. As shown in FIG. 5, the collision detection sensor 66 is located on the base frame 26. A magnet 76 is located on a portion of the body 28 that faces the collision detection sensor 66 in the up-down direction. The collision detection sensor 66 detects the intensity of a magnetic field generated by the magnet 76 on the body 28. When the detected magnetic field intensity is high, the collision detection sensor 66 outputs an H signal to the control unit 8 (see FIG. 4), whereas when the detected magnetic field intensity is low, the collision detection sensor 66 outputs an L signal to the control unit 8. When the body 28 is in the position shown in FIG. 2, the horizontal position of the collision detection sensor 66 coincides with the horizontal position of the magnet 76. In this case, the magnetic field intensity detected by the collision detection sensor 66 is high, and thus the collision detection sensor 66 outputs the H signal to the control unit 8. When the body 28 moves horizontally from the position shown in FIG. 2, the horizontal position of the collision detection sensor 66 is thereby offset from the horizontal position of the magnet 76. In this case, the magnetic field intensity detected by the collision detection sensor 66 is low, and thus the collision detection sensor 66 outputs the L signal to the control unit 8.

The lift detection sensor 68 is configured to detect a lift of the robotic mower 2 from the ground G. The lift detection sensor 68 is for example an inductive sensor. As shown in FIG. 6, the lift detection sensor 68 is located on the base frame 26. A metal plate 78 is located on a portion of the body 28 that faces the lift detection sensor 68 in the up-down direction. The lift detection sensor 68 detects whether the metal plate 78 on the body 28 is nearby. When detecting that the metal plate 78 is nearby, the lift detection sensor 68 outputs the H signal to the control unit 8 (see FIG. 4), whereas when detecting that the metal plate 78 is not nearby, the lift detection sensor 68 outputs the L signal to the control unit 8. When the body 28 is in the position shown in FIG. 2, the metal plate 78 is near the lift detection sensor 68, and thus the lift detection sensor 68 outputs the H signal to the control unit 8. When the body 28 moves upward from the position shown in FIG. 2, the metal plate 78 is distanced from the lift detection sensor 68, and thus the lift detection sensor 68 outputs the L signal to the control unit 8.

The angular velocity detection sensor 70 shown in FIG. 4 is located on/in the base frame 26 (see FIG. 2). The angular velocity detection sensor 70 is configured to detect an angular velocity of the base frame 26 and output it to the control unit 8.

The battery voltage detection circuit 74 is configured to detect a voltage value of the battery 30 (i.e., amount of remaining power in the battery 30) and output it to the control unit 8.

The motor current detection circuit 72 is configured to detect values of current supplied to the movement motors 44L, 44R and the working motor 48 and output them to the control unit 8.

Autonomous Operation

Hereinafter, an autonomous operation executed by the control unit 8 (specifically, the processor 34) will be described. In this embodiment, the autonomous operation varies depending on whether the automatic height adjustment function is enabled or disabled.

Autonomous Operation With Automatic Height Adjustment Function Enabled

With the automatic height adjustment function enabled, the robotic mower 2 changes the height level h of the blade 46 (see FIG. 2) from an initial height level to a target height level in stages. In this embodiment, the initial height level is larger than the target height level. For example, the initial height level is 50 mm and the target height level is 30 mm. That is, the robotic mower 2 lowers the height level h of the blade 46 from the initial height level to the target height level in stages. Hereinafter, referring to FIG. 7, the autonomous operation with the automatic height adjustment function enabled will be described in detail.

The process shown in FIG. 7 is started in response to an instruction to start the autonomous operation being inputted via the input unit 10 (see FIG. 4) or the user's communication terminal when the automatic height adjustment function is enabled.

• • In S2, the control unit 8 controls the height adjustment motor 54 (see FIG. 2) to set the height level h of the blade 46 to the initial height level preset by the user. After S2, the process proceeds to S4.
  • In S4, the control unit 8 determines whether the current time is within a working time slot. When the current time is not within the working time slot (NO in S4), the process proceeds to S6.
  • In S6, the control unit 8 keeps the robotic mower 2 at the charging station 110 (see FIG. 1). If the robotic mower 2 is not at the charging station 110 at the start of S6, the control unit 8 returns the robotic mower 2 to the charging station 110. Specifically, the control unit 8 stops the working motor 48 (see FIG. 4) and controls the movement motors 44L, 44R (see FIG. 4) such that the robotic mower 2 can reach the charging station 110 following the wire 112. Then, the control unit 8 stops the movement motors 44L, 44R and keeps the robotic mower 2 at the charging station 110. After S6, the process returns to S4.

When the control unit 8 determines in S4 that the current time in within the working time slot (YES in S4), the process proceeds to S8. In S8, the control unit 8 causes the robotic mower 2 to start mowing work. Specifically, the control unit 8 controls the working motor 48 to cause the robotic mower 2 to mow the lawn using the blade 46 while controlling the movement motors 44L, 44R to move the robot body 4 around. Thereby, the lawn is cut to a height substantially equal to the height level h of the blade 46. After S8, the process proceeds to S10.

• • In S10, the control unit 8 determines whether a lawn height uniformity condition is satisfied. The lawn height uniformity condition is for example a condition under which the lawn within the working region WA (see FIG. 1) is expected to have been cut to the height level h of the blade 46 as a whole. The lawn height uniformity condition includes a first lawn height uniformity condition that a cumulative total of mowing work periods without a change in the height level h of the blade 46 exceeds a first working duration threshold. The mowing work periods hereof means periods within the total time period from the start to the end of the mowing work excluding periods during which the mowing work was suspended. The mowing work periods include for example a period during which the working motor 48 was in operation during the mowing work. The cumulative total of mowing work periods hereof means a sum of mowing work periods where the mowing work is performed multiple times without a change in the height level h of the blade 46. The first working duration threshold here is a duration threshold determined depending on the area of the working region WA. In the memory 36 of the control unit 8, the threshold table TT shown in FIG. 8 is stored. In the threshold table TT, areas of the working region WA are associated with corresponding first working duration thresholds. Thus, the control unit 8 can determine a first working duration threshold corresponding to the area of the working region WA preset by the user. In the threshold table TT, each area range is associated with its corresponding first working duration threshold. The lawn height uniformity condition further includes a second lawn height uniformity condition that a cumulative total of mowing work periods without charging of the battery 30 (see FIG. 4) exceeds a second working duration threshold. The second working duration threshold is for example 2 hours or longer, and in this embodiment, it is 2.5 hours. Typically, as a larger part of the lawn is cut to the height level h of the blade 46, the working motor 48 which drives the blade 46 experiences a smaller load, i.e., the battery 30 lasts longer. Since the battery 30 lasts longer, the cumulative total of mowing work periods without charging of the battery 30 becomes larger. Therefore, the lawn within the working region WA can be assumed to have been cut to the height level h of the blade 46 as a whole based on cumulative total of mowing work periods without charging of the battery 30 being large. When any one of the above-mentioned conditions is satisfied, the control unit 8 determines that the lawn height uniformity condition is satisfied (YES in S10). After the lawn height uniformity condition is satisfied (YES in S10), the process proceeds to S12.
  • In S12, the control unit 8 switches a lawn height uniformity flag to on. In other words, the control unit 8 stores in the memory 36 information indicating that the lawn height uniformity condition has been satisfied in S10.

When the lawn height uniformity condition is not satisfied in S10 (NO in S10) or after S12, the process proceeds to S14. In S14, the control unit 8 determines whether a predetermined return condition is satisfied. The return condition includes a first return condition that an amount of remaining power in the battery 30 is low. Specifically, the first return condition is a condition that the voltage value of the battery 30 detected by the battery voltage detection circuit 74 (see FIG. 4) is equal to or less than a predetermined voltage value (e.g., 17.5 V). The return condition further includes a second return condition that the lawn height uniformity flag is on. When any one of the above-mentioned conditions is satisfied, the control unit 8 determines that the return condition is satisfied (YES in S14). When the control unit 8 determine that the return condition is not satisfied (NO in S14), the process returns to S10. After the return condition is satisfied (YES in S14), the process proceeds to S16.

• • In S16, the control unit 8 causes the robotic mower 2 to stop the mowing work which was started in S8 and returns the robotic mower 2 to the charging station 110. Specifically, the control unit 8 stops the working motor 48 and controls the movement motors 44L, 44R such that the robotic mower 2 can reach the charging station 110 following the wire 112. After S16, the process proceeds to S18.
  • In S18, the control unit 8 docks the robotic mower 2 to the charging station 110 and starts charging the battery 30. The control unit 8 keeps charging the battery 30 until a predetermined charging termination condition is satisfied. The charging termination condition is for example that the voltage value of the battery 30 detected by the battery voltage detection circuit 74 reaches a predetermined value (e.g., 20 V) or more. When the charging of the battery 30 terminates in S18, the process proceeds to S20.
  • In S20, the control unit 8 determines whether the lawn height uniformity flag is on. When the control unit 8 determines that the lawn height uniformity flag is off (NO in S20), the process returns to S4. When the control unit 8 determines that the lawn height uniformity flag is on (YES in S20), the process proceeds to S22.
  • In S22, the control unit 8 determines whether the current height level h of the blade 46 is equal to the target height level preset by the user. When the control unit 8 determines that the height level h of the blade 46 is not equal to the target height level (i.e., the height level h of the blade 46 is higher than the target height level) (NO in S22), the process proceeds to S24.
  • In S24, the control unit 8 controls the height adjustment motor 54 (see FIG. 2) to lower the height level h of the blade 46 by a predetermined distance (e.g., 5 mm). During S24, the robotic mower 2 is at the charging station 110. Thus, the height level h of the blade 46 is lowered at the relatively safe place. The control unit 8 switches the lawn height uniformity flag to off in response to lowering the height level h of the blade 46. After S24, the process proceeds to S4.

When the control unit 8 determines in S22 that the height level h of the blade 46 is equal to the target height level (YES in S22), the process proceeds to S26. In S26, the control unit 8 informs the user that the lawn within the working region WA has been cut to the target height level as a whole. For example, the control unit 8 communicates with the user's communication terminal via the communication unit 12 (see FIG. 4) to cause the communication terminal to inform the user that the lawn within the working region WA has been cut to the target height level as a whole. After S26, the process shown in FIG. 7 terminates.

The process shown in FIG. 7 also terminates in response to an instruction to terminate the autonomous operation being inputted via the input unit 10 or the user's communication terminal. The process shown in FIG. 7 also terminates in response to the main power of the robotic mower 2 being switched to off via the input unit 10 or the user's communication terminal.

Autonomous Operation With Automatic Height Adjustment Function Disabled

When the automatic height adjustment function is disabled, the robotic mower 2 maintains the height level h of the blade 46 (see FIG. 2) at a fixed height level preset by the user. Hereinafter, referring to FIG. 9, the autonomous operation with the automatic height adjustment function disabled will be described.

The process shown in FIG. 9 is started in response to an instruction to start the autonomous operation being inputted via the input unit 10 (see FIG. 4) or the user's communication terminal when the automatic height adjustment function is disabled.

• • In S32, the control unit 8 controls the height adjustment motor 54 (see FIG. 2) to set the height level h of the blade 46 to the fixed height level. After S32, the process proceeds to S34.
  • In S34, the control unit 8 determines whether the current time is within a working time slot. When the control unit 8 determines that the current time is out of the working time slot (NO in S34), the process proceeds to S36.
  • In S36, the control unit 8 keeps the robotic mower 2 at the charging station 110 (see FIG. 1). If the robotic mower 2 is not at the charging station 110 at the start of S36, the control unit 8 returns the robotic mower 2 to the charging station 110. Specifically, the control unit 8 stops the working motor 48 (see FIG. 4) and controls the movement motors 44L, 44R (see FIG. 4) such that the robotic mower 2 can reach the charging station 110 following the wire 112. Then, the control unit 8 stops the movement motors 44L, 44R and keeps the robotic mower 2 at the charging station 110. After S36, the process returns to S34.

When the control unit 8 determines that the current time is within the working time slot (YES in S34), the process proceeds to S38. In S38, the control unit 8 causes the robotic mower 2 to start mowing work. Specifically, the control unit 8 controls the working motor 48 to cause the robotic mower 2 to mow the lawn using the blade 46 while controlling the movement motors 44L, 44R to move the robot body 4 around. After S38, the process proceeds to S40.

• • In S40, the control unit 8 determines whether a predetermined return condition is satisfied. This return condition is for example a condition that the voltage value of the battery 30 detected by the battery voltage detection circuit 74 (see FIG. 4) becomes equal to or less than a predetermined voltage value (e.g., 17.5 V). When the control unit 8 determines that the return condition is not satisfied (NO in S40), the process repeats S40. When the control unit 8 determines that the return condition is satisfied (YES in S40), the process proceeds to S42.
  • In S42, the control unit 8 causes the robotic mower 2 to stop the mowing work which was started in S38 and returns the robotic mower 2 to the charging station 110. Specifically, the control unit 8 stops the working motor 48 and controls the movement motors 44L, 44R such that the robotic mower 2 can return to the charging station 110 following the wire 112. After S42, the process proceeds to S44.
  • In S44, the control unit 8 docks the robotic mower 2 to the charging station 110 and starts charging the battery 30. The control unit 8 keeps charging the battery 30 until a predetermined charging termination condition is satisfied. This charging termination condition is for example a condition that the voltage value of the battery 30 detected by the battery voltage detection circuit 74 becomes a predetermined value (e.g., 20 V) or more. When the charging of the battery 30 terminates in S44, the process returns to S34.

The process shown in FIG. 9 terminates in response to an instruction to terminate the autonomous operation being inputted via the input unit 10 or the user's communication terminal. The process shown in FIG. 9 also terminates in response to the main power of the robotic mower 2 being switched to off via the input unit 10 or the user's communication terminal.

Behavior of Robotic Mower 2 Upon Bump Against Obstacle

During the autonomous operation, the control unit 8 repeats the process shown in FIG. 10 regardless of whether the automatic height adjustment function is enabled or disabled.

• • In S52, the control unit 8 determines whether movement of the body 28 (see FIG. 2) relative to the base frame 26 (see FIG. 2) is detected. Specifically, the control unit 8 determines whether at least one of the collision detection sensor 66 (see FIG. 4) and the lift detection sensor 68 (see FIG. 4) outputs the L signal. When the control unit 8 determines that movement of the body 28 relative to the base frame 26 is not detected (NO in S52), the process proceeds to S54.
  • In S54, the control unit 8 determines that the robotic mower 2 is not hindered from moving. After S54, the process returns to S52.

When the control unit 8 determines in S52 that movement of the body 28 relative to the base frame 26 is detected (YES in S52), the process proceeds to S56. In S56, the control unit 8 determines that the robotic mower 2 is hindered from moving by an obstacle. In response, the control unit 8 stops the movement motors 44L, 44R (see FIG. 4) and the working motor 48 (see FIG. 4) to suspend a normal action. The normal action here means the mowing work performed by the robotic mower 2 or the returning of the robotic mower 2 during the autonomous operation. After S56, the process proceeds to S58.

• • In S58, the control unit 8 controls the movement motors 44L, 44R to cause the robotic mower 2 to start performing a circumvention action. The circumvention action here is for example any one of a forward action in which the robotic mower 2 moves forward, a rearward action in which the robotic mower 2 moves rearward, a left turning action in which the robotic mower 2 turns left, and a right turning action in which the robotic mower 2 turns right. The turning actions here include actions in which the robotic mower 2 turns on the spot but also actions in which the robotic mower 2 turns while moving forward or rearward. In this embodiment, the control unit 8 specifies the moving direction of the robotic mower 2 prior to the suspension of the normal action in S56. Then, the control unit 8 determines the circumvention action to be started in S58 as an action in which the robotic mower 2 moves in the opposite direction to the moving direction prior to the suspension of normal action in S56. As an example, if the robotic mower 2 was moving forward before the normal action was suspended in S56, the circumvention action to be started in S58 is the rearward action. As another example, if the robotic mower 2 was turning left before the normal action was suspended in S56, the circumvention action to be started in S58 is the right turning action. After S58, the process proceeds to S60.
  • In S60, the control unit 8 determines whether movement of the body 28 relative to the base frame 26 is detected during the circumvention action started immediately before S60 (i.e., the circumvention action started in S58 or S62). Specifically, the control unit 8 determines whether the signal(s) from at least one of the collision detection sensor 66 and the lift detection sensor 68 change from the H signal to the L signal during the circumvention action. It should be noted that if at least one of the sensors keeps outputting the L signal from the start of the circumvention action, this L signal from the sensor(s) is not considered as the L signal changed from the H signal during the circumvention action. Thus, the answer YES is not produced to the determination in S60 based on such L signal(s) from the sensor(s). In this regard, the answer YES/No to the determination in S60 is different from the answer YES/NO to the determination in S52. When the control unit 8 determines that movement of the body 28 relative to the base frame 26 is detected during the circumvention action (YES in S60), the process proceeds to S62.
  • In S62, the control unit 8 causes the robotic mower 2 to start a circumvention action different from the previous circumvention action. For example, if the previous circumvention action was the forward action, the control unit 8 causes the robotic mower 2 to start the rearward action, the left turning action, or the right turning action. After S62, the process returns to S60.

When the control unit 8 determines in S60 that movement of the body 28 relative to the base frame 26 is not detected during the circumvention action (NO in S60), the process proceeds to S64. In S64, the control unit 8 determines whether an overload on the movement motors 44L, 44R is detected during the circumvention action started prior to the answer NO to the determination in S60. Specifically, the control unit 8 determines whether values of current flowing in the movement motors 44L, 44R detected by the motor current detection circuit 72 (see FIG. 4) remain at or above a predetermined current value (e.g., 3.0 A) for a predetermined duration (e.g., 0.1 seconds) or longer. When the control unit 8 determines that an overload on the movement motors 44L, 44R is detected during the circumvention action (YES in S64), the process proceeds to S66.

• • In S66, the control unit 8 determines that the robotic mower 2 is hindered from moving (performing the circumvention action) by an obstacle. For example, if a part of the robotic mower 2 other than the body 28 (e.g., the drive wheel 42L or 42R) bumps an obstacle, the robotic mower 2 is hindered from moving by the obstacle despite movement of the body 28 being not detected (despite the answer to the determination in S60 being NO). In this case, however, the movement motors 44L, 44R are expected to experience a larger load than usual due to the blocking of the obstacle. Thus, the robotic mower 2 according to this embodiment determines that the robotic mower 2 is hindered from moving by an obstacle when detecting an overload on the movement motors 44L, 44R (in case of YES to the determination in S64). In S66, the control unit 8 further increments by 1 the number of times the robotic mower 2 has been hindered from moving by an obstacle (this number may be termed “count number” hereinafter). Since the count number is reset to zero at the end of the process shown in FIG. 10, it is zero at the start of the process shown in FIG. 10. After S66, the process proceeds to S68.
  • In S68, the control unit 8 determines whether the count number is equal to or more than a predetermined number (e.g., 2). When the control unit 8 determines that the count number is less than the predetermined number (NO in S68), the process proceeds to S62. When the control unit 8 determines that the count number is equal to or more than the predetermined number (YES in S68), the process proceeds to S70.
  • In S70, the control unit 8 determines that an abnormality is occurring in the robotic mower 2 and stops the robotic mower 2. Specifically, the control unit 8 stops the movement motors 44L, 44R and the working motor 48 to keep the robotic mower 2 on the spot. The control unit 8 further controls the display unit 14 (see FIG. 4) and/or the alarm unit 16 (see FIG. 4) to inform the user of the occurrence of abnormality by light and/or sound. Alternatively, the control unit 8 communicates with the user's communication terminal (e.g., smartphone) via the communication unit 12 (see FIG. 4) to inform the user of the occurrence of abnormality through the communication terminal. After S70, the process shown in FIG. 10 terminates.

When the control unit 8 determines in S64 that an overload on the movement motors 44L, 44R is not detected during the circumvention action (NO in S64), the process proceeds to S72. In S72, the control unit 8 determines whether the circumvention action started in S58 or S62 has terminated. In this embodiment, the control unit 8 presets how many times the output shafts of the movement motors 44L, 44R are to be rotated for a circumvention action, and monitors the numbers of rotations of the output shafts of the movement motors 44L, 44R using rotation detection sensors (e.g., resolvers) for the movement motors 44L, 44R. Thus, the control unit 8 determines that the circumvention action has terminated for example in response to the numbers of rotations of the output shafts of the movement motors 44L, 44R from the start of the circumvention action reaching the preset numbers of rotations (YES in S72). When the control unit 8 determines that the circumvention action has not terminated yet (NO in S72), the process proceeds to S60. When the control unit 8 determines that the circumvention action has terminated (YES in S72), the process proceeds to S74.

• • In S74, the control unit 8 determines that the robotic mower 2 is not hindered from moving (specifically, performing the circumvention action). This is because movement of the robotic mower 2 is thought to terminate without a hitch since an overload on the movement motors 44L, 44R was not detected. The control unit 8 further resumes the normal action suspended in S56 (the mowing work or returning). After S74, the process shown in FIG. 10 terminates.

Second Embodiment: Robotic Mower 202

A robotic mower 202 has substantially the same configuration as that of the robotic mower 2 according to the first embodiment (see FIGS. 1 to 10). The robotic mower 202 is different from the robotic mower 2 according to the first embodiment only in that the control unit 8 (see FIG. 4) executes the process shown in FIG. 11 instead of the process shown in FIG. 10. Thus, hereinafter, only the process shown in FIG. 11 is described, and other descriptions are omitted.

• • In S102, the control unit 8 determines whether movement of the body 28 (see FIG. 2) relative to the base frame 26 (see FIG. 2) is detected. Specifically, the control unit 8 determines whether at least one of the collision detection sensor 66 (see FIG. 4) and the lift detection sensor 68 (see FIG. 4) is outputting the L signal(s). When the control unit 8 determines that movement of the body 28 relative to the base frame 26 is not detected (NO in S102), the process proceeds to S104.
  • In S104, the control unit 8 determines that the robotic mower 202 is not hindered from moving. After S104, the process returns to S102.

When the control unit 8 determines in S102 that movement of the body 28 relative to the base frame 26 is detected (YES in S102), the process proceeds to S106. In S106, the control unit 8 determines that the robotic mower 202 is hindered from moving by an obstacle. Then, the control unit 8 stops the movement motors 44L, 44R (see FIG. 4) and the working motor 48 (see FIG. 4) to suspend the normal action (the mowing work or returning). After S106, the process proceeds to S108.

• • In S108, the control unit 8 controls the movement motors 44L, 44R to cause the robotic mower 202 to perform a straight action (i.e., the forward action or the rearward action). In this embodiment, the control unit 8 determines whether the moving direction of the robotic mower 202 prior to the suspension of normal action in S106 was the front direction or rear direction. Then the control unit 8 determines the straight action to be performed in S108 as an action in which the robotic mower 202 moves in the opposite direction to the moving direction thereof prior to the suspension of normal action in S106. For example, if the robotic mower 202 was moving in the front direction before the normal action was suspended in S106, the straight action to be performed in S108 is the rearward action. When the straight action terminates, the process proceeds to S110.
  • In S110, the control unit 8 controls the movement motors 44L, 44R to cause the robotic mower 202 to start a turning action (i.e., the left turning action or the right turning action). At this time, the control unit 8 randomly sets a turning direction of the robotic mower 202 and a target turning angle of the robotic mower 202. The target turning angle is for example within a range from 10 degrees to 180 degrees. The control unit 8 controls the movement motors 44L, 44R to turn the robotic mower 202 in the set turning direction and by the set target turning angle. After S110, the process proceeds to S112.
  • In S112, the control unit 8 determines whether the angle by which the robotic mower 202 has turned from the start of the turning action is equal to the target turning angle. The control unit 8 uses the angular velocity detection sensor 70 (see FIG. 4) located on the base frame 26 to measure an angle by which the robotic mower 202 has turned from the start of the turning action. When the control unit 8 determines that the angle by which the robotic mower 202 has turned from the start of turning action is less than the target turning angle (NO in S112), the process proceeds to S114.
  • In S114, the control unit 8 determines whether a period elapsed from the start of turning action in S110 reaches a predetermined period (e.g., 6.0 seconds) or longer. When the control unit 8 determines that the period elapsed is less than the predetermined period (NO in S114), the process returns to S112. When the control unit 8 determines that the period elapsed is longer than the predetermined period (YES in S114), the process proceeds to S116.
  • In S116, the control unit 8 determines that the robotic mower 202 is hindered from moving (performing the circumvention action) by an obstacle. For example, if a part of the robotic mower 202 other than the body 28 (e.g., the drive wheel 42L or 42R) bumps an obstacle, the robotic mower 202 is thereby hindered from moving despite movement of the body 28 being not detected (the answer to the determination in S102 being NO). In this case, the turning angle of the robotic mower 202 is expected not to change at all due to the blocking of the obstacle despite the movement motors 44L, 44R being driven. Thus, the robotic mower 202 according to this embodiment determines that the robotic mower 202 is hindered from moving by an obstacle when the turning angle of the robotic mower 202 remains less than the target turning angle for a certain period of time (in case of YES in S114). In S116, the control unit 8 further increments by 1 the number of times the robotic mower 202 has been hindered from moving by an obstacle (this number may be termed “count number” hereinafter). Since the count number is reset to zero at the end of the process shown in FIG. 11, it is zero at the start of the process shown in FIG. 11. After S116, the process proceeds to S118.
  • In S118, the control unit 8 determines whether the count number is equal to or more than a predetermined number (e.g., 2). When the control unit 8 determines that the count number is less than the predetermined number (NO in S118), the process proceeds to S120.
  • In S120, the control unit 8 causes the robotic mower 202 to start a turning action which is opposite in direction to the previous turning action. For example, if the previous turning action was the left turning action, the control unit 8 causes the robotic mower 202 to start the right turning action. After S120, the process returns to S112.

When the control unit 8 determines in S118 that the count number is equal to or more than the predetermined number (YES in S118), the process proceeds to S122. In S122, the control unit 8 determines that an abnormality is occurring in the robotic mower 202 and stops the robotic mower 202. Specifically, the control unit 8 stops the movement motors 44L, 44R and the working motor 48 to keep the robotic mower 202 on the spot. The control unit 8 further controls the display unit 14 (see FIG. 4) and/or the alarm unit 16 (see FIG. 4) to inform the user of the occurrence of abnormality by light and/or sound. Alternatively, the control unit 8 communicates with the user's communication terminal (e.g., smartphone) via the communication unit 12 (see FIG. 4) to inform the user of the occurrence of abnormality through the communication terminal. After S122, the process shown in FIG. 11 terminates.

When the control unit 8 determines in S112 that the angle by which the robotic mower 202 has turned from the start of turning action is equal to the target turning angle (YES in S112), the process proceeds to S124.

• • In S124, the control unit 8 determines that the robotic mower 202 is not hindered from moving (specifically, performing the circumvention action) by an obstacle. This is because movement of the robotic mower 202 is thought to have terminated based on the fact that the turning angle of the robotic mower 202 became equal to the target turning angle. Further, the control unit 8 resumes the normal action suspended in S106 (the mowing work or returning). After S124, the process shown in FIG. 11 terminates.

Third Embodiment: Robotic Mower 302

A robotic mower 302 has substantially the same configuration as that of the robotic mower 2 according to the first embodiment (see FIGS. 1 to 10). The robotic mower 302 is different from the robotic mower 2 according to the first embodiment only in that the control unit 8 (see FIG. 4) executes the process shown in FIG. 12 instead of the process shown in FIG. 10. The process shown in FIG. 12 is different from the process shown in FIG. 10 in that S60 and S64 are replaced with S160 and S164. Thus, hereinafter, only S160 and S164 in FIG. 12 are described, and other descriptions are omitted.

• • S160 is executed after S58 or after S62. In S160, the control unit 8 determines whether movement of the body 28 relative to the base frame 26 is detected during the circumvention action started immediately before S160 (started in S58 or S62). Specifically, the control unit 8 determines whether the signal(s) from at least one of the collision detection sensor 66 (see FIG. 4) and the lift detection sensor 68 (see FIG. 4) change from the H signal(s) to the L signal(s) during the circumvention action. It should be noted that if at least one of the sensors keeps outputting the L signal(s) from the start of the circumvention action, this L signal is not considered as the L signal changed from the H signal during the circumvention action. Thus, the answer YES is not produced to the determination in S160 based on such L signal(s) from the sensor(s). In this regard, the answer YES/NO to the determination in S160 is different from the answer YES/NO to the determination in S52. When the control unit 8 determines that movement of the body 28 relative to the base frame 26 is not detected during the circumvention action (NO in S160), the process proceeds to S72. When the control unit 8 determines that movement of the body 28 relative to the base frame 26 is detected (YES in S160), the process proceeds to S164.
  • In S164, the control unit 8 determines whether an overload on the movement motors 44L, 44R is detected during the circumvention action started immediately before the answer YES was produced to the determination in S160. Specifically, the control unit 8 determines whether values of current flowing in the movement motors 44L, 44R detected by the motor current detection circuit 72 (see FIG. 4) remain at or above a predetermined current value (e.g., 3.0 A) for a predetermined duration (e.g., 0.1 seconds) or longer. When the control unit 8 determines that an overload on the movement motors 44L, 44R is not detected during the circumvention action (NO in S164), the process proceeds to S62. When the control unit 8 determines that an overload on the movement motors 44L, 44R is detected during the circumvention action (YES in S164), the process proceeds to S66.

When movement of the body 28 is detected (YES in S160), the robotic mower 302 is probably hindered from moving by an obstacle but that is not totally certain unless an overload on the movement motors 44L, 44R is detected (NO in S164). In this case, the robotic mower 302 according to this embodiment does not determine whether the robotic mower 302 is hindered from moving by an obstacle or not and performs a different circumvention action. In response to movement of the body 28 being detected (YES in S160) and an overload on the movement motors 44L, 44R being detected (YES in S164), the control unit 8 determines that the robotic mower 302 is hindered from moving by an obstacle. This prevents the control unit 8 from making an erroneous determination (determining that the robotic mower 302 is hindered from moving by an obstacle despite the robotic mower 302 being not hindered from moving actually).

Fourth Embodiment: Robotic Mower 402

A robotic mower 402 has substantially the same configuration as that of the robotic mower 2 according to the first embodiment (see FIGS. 1 to 10). The robotic mower 402 is different from the robotic mower 2 according to the first embodiment only in that the control unit 8 (see FIG. 4) executes the process shown in FIG. 13 instead of the process shown in FIG. 7. Thus, hereinafter, only the process shown in FIG. 13 is described, and other descriptions are omitted.

• • In S202, the control unit 8 controls the height adjustment motor 54 (see FIG. 2) to set the height level h of the blade 46 (see FIG. 2) to the initial height level preset by the user. After S202, the process proceeds to S204.
  • In S204, the control unit 8 determines whether the current time is within a working time slot. When the control unit 8 determines that the current time is out of the working time slot (NO in S204), the process proceeds to S206.
  • In S206, the control unit 8 keeps the robotic mower 402 at the charging station 110 (see FIG. 1). If the robotic mower 402 is not at the charging station 110 at the start of S206, the control unit 8 returns the robotic mower 402 to the charging station 110. Specifically, the control unit 8 stops the working motor 48 (see FIG. 4) and controls the movement motors 44L, 44R (see FIG. 4) such that the robotic mower 402 can reach the charging station 110 following the wire 112. The control unit 8 then stops the movement motors 44L, 44R to keep the robotic mower 402 at the charging station 110. After S206, the process returns to S204.

When the control unit 8 determines in S204 that the current time is within the working time slot (YES in S204), the process proceeds to S208. In S208, the control unit 8 causes the robotic mower 402 to start mowing work. Specifically, the control unit 8 controls the working motor 48 to cause the robotic mower 402 to mow the lawn using the blade 46 (see FIG. 2) while controlling the movement motors 44L, 44R to move the robot body 4 around. The lawn is thereby cut to the height level h of the blade 46. After S208, the process proceeds to S210.

• • In S210, the control unit 8 determines whether a predetermined lawn height uniformity condition is satisfied. The lawn height uniformity condition here is substantially the same as the one described in connection with the first embodiment and thus the description is not repeated here. When the control unit 8 determines that the lawn height uniformity condition is satisfied (YES in S210), the process proceeds to S212.
  • In S212, the control unit 8 determines whether the current height level h of the blade 46 is equal to the target height level preset by the user. When the control unit 8 determines that the height level h of the blade 46 is not equal to the target height level (i.e., the height level h of the blade 46 is higher than the target height level) (NO in S212), the process proceeds to S214.
  • In S214, the control unit 8 controls the height adjustment motor 54 to lower the height level h of the blade 46 by a predetermined distance (e.g., 5 mm).

When the control unit 8 determines in S212 that the height level h of the blade 46 is equal to the target height level (YES in S212), the process proceeds to S216. In S216, the control unit 8 switches a target height level flag to on. The target height level flag indicates that the lawn within the working region WA has been cut to the target height level as a whole.

When the control unit 8 determines in S210 that the lawn height uniformity condition is not satisfied (NO in S210), after S214, or after S216, the process proceeds to S218. In S218, the control unit 8 determines whether a predetermined return condition is satisfied. The return condition here is substantially the same as the one described in connection with the first embodiment and thus the description is not repeated here. When the control unit 8 determines that the return condition is not satisfied (NO in S218), the process returns to S210. When the control unit 8 determines that the return condition is satisfied (YES in S218), the process proceeds to S220.

• • In S220, the control unit 8 causes the robotic mower 402 to stop the mowing work which was started in S208 and return to the charging station 110. Specifically, the control unit 8 stops the working motor 48 and controls the movement motors 44L, 44R such that the robotic mower 402 can reach the charging station 110 following the wire 112. After S220, the process proceeds to S222.
  • In S222, the control unit 8 docks the robotic mower 402 to the charging station 110 and starts charging the battery 30 (see FIG. 4). The control unit 8 keeps charging the battery 30 until a predetermined charging termination condition is satisfied. The charging termination condition is for example that the voltage value of the battery 30 detected by the battery voltage detection circuit 74 (see FIG. 4) becomes equal to or more than a predetermined value (e.g., 20 V). When the charging of the battery 30 terminates in S222, the process proceeds to S224.
  • In S224, the control unit 8 determines whether the target height level flag is on. When the control unit 8 determines that the target height level flag is off (NO in S224), the process returns to S204. When the control unit 8 determines that the target height level flag is on (YES in S224), the process proceeds to S226.
  • In S226, the control unit 8 informs the user that the lawn within the working region WA has been cut to the target height level as a whole. For example, the control unit 8 communicates with the user's communication terminal via the communication unit 12 (see FIG. 4) to inform the user that the lawn within the working region WA has been cut to the target height level as a whole through the communication terminal. After S226, the process shown in FIG. 13 terminates.

Variants

The working robot may be a robot other than the robotic mowers 2, 202, 302, 402. For example, the working robot may be a robot cleaner comprising a brush and/or a suction mechanism for collecting debris such as dust. In this case, the working motor 48 may be used to drive the brush and/or the suction mechanism. Alternatively, the working robot may be a rebar tying robot comprising a rebar tying mechanism configured to tie multiple rebars at their intersections. In this case, the working motor 48 may be used to drive the rebar tying mechanism.

A power cable connected to an external power supply (e.g., a commercial power supply) may be connected to each of the robotic mowers 2, 202, 302, 402. In this case, the robotic mowers 2, 202, 302, 402 may be configured to operate using electric power supplied from the external power supply through the power cable.

The robotic mowers 2, 202, 302, 402 each may not comprise the battery 30. Instead, a rechargeable battery pack such as a lithium-ion battery may be detachably attached to the robot body 4. In this case, the robotic mowers 2, 202, 302, 402 may be configured to operate using electric power supplied from the battery pack.

The movement unit 18 may comprise, instead of the casters 40L, 40R and the drive wheels 42L, 42R, another movement mechanism (e.g., a crawler, a side stepper). The side stepper here comprises a mechanism configured to move the robot body 4 in the right-left direction. If the movement unit 18 comprises the side stepper, the circumvention action may include actions in which the robot body 4 is moved leftward and rightward.

The return condition used in S14 shown in FIG. 7 may not include the second return condition. Instead, the return condition used in S14 shown in FIG. 7 may include a third return condition that the lawn height uniformity flag is on and the amount of remaining power in the battery 30 is relatively large (e.g., the voltage value of the battery 30 is equal to or more than 19 V).

The distance by which the height level h of the blade 46 is to be lowered in S24 shown in FIG. 7 (or in S214 shown in FIG. 13) may not be predetermined. For example, the control unit 8 may randomly determine the distance. Alternatively, the control unit 8 may set the distance such that a distance by which the height level h of the blade 46 is to be lowered when S24 (or S214) is executed for the first time during the autonomous operation is greater than a distance by which the height level h of the blade 46 is to be lowered when S24 (or S214) is executed next time. Alternatively, the user may change the distance by which the height level h of the blade 46 is to be lowered using the input unit 10 or the user's communication terminal.

The robotic mowers 2, 202, 302, 402 each may have a mapping function to create map information of the working region WA. For example, the control unit 8 may create the map information by acquiring movement history of the robotic mower 2, 202, 302, 402 through an GPS. The map information of the working region WA may include the area of the working region WA. This allows the control unit 8 to acquire the area of the working region WA without the user setting it.

In the process shown in FIG. 10, after S58 or after S62, the process may skip S60 and proceeds to S64. That is, while the robotic mower 2 is performing the circumvention action, the control unit 8 may determine whether the robotic mower 2 is hindered from moving by an obstacle not based on detection results from the collision detection sensor 66 and the lift detection sensor 68 but only based on detection result from the motor current detection circuit 72.

When the control unit 8 determines in S60 shown in FIG. 10 that movement of the body 28 relative to the base frame 26 is detected (YES in S60), the process may proceed to S66. That is, the control unit 8 may determine that the robotic mower 2 is hindered from moving by an obstacle when movement of the body 28 is detected during the circumvention action.

• • In S60 shown in FIG. 10 (or in S160 shown in FIG. 12), the control unit 8 may determine whether the L signal(s) are outputted from at least one of the collision detection sensor 66 and the lift detection sensor 68, instead of determining whether the signal(s) from at least one of the collision detection sensor 66 and the lift detection sensor 68 change from the H signal(s) to the L signal(s) during the circumvention action. That is, the control unit 8 may answer YES to the determination in S60 (or in S160) when the L signal(s) are outputted from at least one of the sensors, even without the change from the H signal to the L signal.
  • In S64 shown in FIG. 10 (or in S164 shown in FIG. 12), the control unit 8 may determine whether values of current flowing in the movement motors 44L, 44R detected by the motor current detection circuit 72 are equal to or more than the predetermined current value, instead of determining whether values of current flowing in the movement motors 44L, 44R detected by the motor current detection circuit 72 remain at or above the predetermined current value for the predetermined duration. That is, the control unit 8 may answer YES to the determination in S64 (or in S164) upon when values of current flowing in the movement motors 44L, 44R detected by the motor current detection circuit 72 become equal to or more than the predetermined current value.

The robotic mowers 2, 202, 302, 402 each may further comprise an inclination angle detection sensor (e.g., a gyroscope sensor) configured to detect an inclination angle of the base frame 26 to the horizontal direction. In this case, in S52 and S60 shown in FIG. 10 (or in S102 shown in FIG. 11, in S52 and S160 shown in FIG. 12), the control unit 8 may determine whether an inclination angle of the base frame 26 detected by the inclination angle detection sensor is greater than a predetermined angle threshold (e.g., 90 degrees). Alternatively, the control unit 8 may determine whether the L signal(s) is outputted from at least one of the collision detection sensor 66 (see FIG. 4) and the lift detection sensor 68 (see FIG. 4) and whether an inclination angle of the base frame 26 detected by the inclination angle detection sensor is greater than the predetermined angle threshold. In S64 shown in FIG. 10 (or in S164 shown in FIG. 12), the control unit 8 may determine whether an inclination angle of the base frame 26 detected by the inclination angle detection sensor is greater than a predetermined angle threshold (e.g., 90 degrees). Alternatively, the control unit 8 may determine whether an overload on the movement motors 44L, 44R is detected and whether an inclination angle of the base frame 26 detected by the inclination angle detection sensor is greater than the predetermined angle threshold. The control unit 8 may determine that the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle when the inclination angle of the base frame 26 is excessively large.

Features of Embodiments

As described, in one or more embodiments, the robotic mowers 2, 202, 302, 402 (examples of working robot) are configured to move and work autonomously. The robotic mowers 2, 202, 302, 402 each comprise the robot body 4 including the base frame 26 (an example of base) and the body 28 (an example of bumper) supported by the base frame 26, the working unit 20 supported by the base frame 26, the drive wheels 42L, 42R (an example of movement mechanism) configured to move the base frame 26, the movement motors 44L, 44R configured to drive the drive wheels 42L, 42R, the collision detection sensor 66 and/or the lift detection sensor 68 (an example of first detection unit) configured to detect a force that the body 28 receives or displacement of the body 28 relative to the base frame 26, the motor current detection circuit 72 configured to detect the states of the movement motors 44L, 44R (or (or the angular velocity detection sensor 70 configured to detect an angular velocity of the base frame 26 (an example of second detection unit), and the control unit 8. The control unit 8 is configured to determine, based on detection result(s) detected by the collision detection sensor 66 and/or the lift detection sensor 68 and a detection result detected by the motor current detection circuit 72 (or the angular velocity detection sensor 70), whether the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle.

According to the configuration above, the control unit 8 of the robotic mower 2, 202, 302, 402 determines whether the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle or not, not only based on the force that the body 28 receives or displacement of the body 28 relative to the base frame 26 but also based on the state of the movement motors 44L, 44R (or the angular velocity of the base frame 26. This improves the determination accuracy on whether the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle, and thus the robotic mower 2, 202, 302, 402 can easily circumvent the obstacle. The configuration above allows for a smooth progress of work by the robotic mower 2, 202, 302, 402.

In one or more embodiments, the control unit 8 is configured to execute a first hindrance determination process of determining, based on at least the detection result(s) detected by the collision detection sensor 66 and/or the lift detection sensor 68, whether the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle (S52, S54, S56 in FIG. 10) (or S102, S104, S106 in FIG. 11) (or S52, S54, S56 in FIG. 12), a circumvention process of controlling the movement motors 44L, 44R such that the robotic mower 2, 202, 302, 402 performs a circumvention action to circumvent the obstacle after the control unit 8 has determined that the robotic mower 2, 202, 302, 402 is hindered from moving by the obstacle in the first hindrance determination process (S58, S62 in FIG. 10) (or S108, S110, S120 in FIG. 11) (or S58, S62 in FIG. 12), and a second hindrance determination process of determining, based on at least the detection result detected by the motor current detection circuit 72 (or the angular velocity detection sensor 70), whether the robotic mower 2, 202, 302, 402 is hindered from moving by the obstacle while the robotic mower 2, 202, 302, 402 is performing the circumvention action (S60, S64, S66, S72, S74 in FIG. 10) (or S112, S114, S116, S124 in FIG. 11) (or S160, S164, S66, S72, S74 in FIG. 12).

According to the configuration above, in response to the robotic mower 2, 202, 302, 402 (specifically, the body 28) bumping an obstacle, the control unit 8 determines that the robotic mower 2, 202, 302, 402 is hindered from moving by the obstacle and then causes the robotic mower 2, 202, 302, 402 to perform the circumvention action. While robotic mower 2, 202, 302, 402 is performing the circumvention action, a part of the robotic mower 2, 202, 302, 402 other than the body 28 may bump the obstacle and the robotic mower 2, 202, 302, 402 may thereby be hindered from moving. In this case, the detection result(s) from the collision detection sensor 66 and/or the lift detection sensor 68 (the force received by the body 28 or displacement of the body 28 relative to the base frame 26) does not show any particular indication that the robotic mower 2, 202, 302, 402 is hindered from moving by the obstacle. That is, if the control unit 8 determines whether the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle or not based only on the detection result(s) from the collision detection sensor 66 and/or the lift detection sensor 68 while the robotic mower 2, 202, 302, 402 is performing circumvention action, the determination result may be erroneous. By contrast, according to the configuration above, the control unit 8 determines, based on at least the detection result from the motor current detection circuit 72 (or the angular velocity detection sensor 70), whether the robotic mower 2, 202, 302, 402 is hindered from moving by the obstacle while the robotic mower 2, 202, 302, 402 is performing the circumvention action. This prevents an erroneous determination result on whether the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle. Thus, the configuration above allows for accurate determination on whether the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle.

In one or more embodiments, the circumvention action includes the turning actions in which the robotic mower 2, 202, 302, 402 turns.

The configuration above can make the circumvention action relatively complex.

In one or more embodiments, the circumvention action includes the straight actions in which the robotic mower 2, 202, 302, 402 moves straight.

If the circumvention action includes only the turning actions, the robotic mower 2, 202, 302, 402 may not move away from an obstacle at all after having bumped it. In this case, the robotic mower 2, 202, 302, 402 takes longer to circumvent the obstacle, and thus the work performed by the robotic mower 2, 202, 302, 402 may not smoothly progress. According to the configuration above, the circumvention action includes the straight actions, and this allows the robotic mower 2, 202, 302, 402 to move away from an obstacle after having bumped it. The time the robotic mower 2, 202, 302, 402 takes to circumvent the obstacle is thereby reduced, and thus the work performed by the robotic mower 2, 202, 302, 402 can progress smoothly.

In one or more embodiments, the state of the movement motors 44L, 44R includes a current flowing in the movement motors 44L, 44R. The second detection unit includes the motor current detection circuit 72 (an example of motor current detector) configured to detect the current flowing in the movement motors 44L, 44R.

The movement motors 44L, 44R experience a larger load than usual when running while the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle due to the blocking of the obstacle. In this case, current flowing in the movement motors 44L, 44R is expected to be larger than usual. In the configuration above, the control unit 8 can estimate a load on the movement motors 44L, 44R based on current flowing in the movement motors 44L, 44R while the movement motors 44L, 44R are in operation and determine whether the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle or not.

In one or more embodiments, in a case where detection values detected by the motor current detection circuit 72 remain at or above a predetermined current value for a predetermined duration or longer, the control unit 8 determines that the robotic mower 2, 202, 302, 402 is hindered from moving by the obstacle.

In response to determining that the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle, the control unit 8 may cause the robotic mower 2, 202, 302, 402 to perform the circumvention action to circumvent the obstacle, but sometimes the robotic mower 2, 202, 302, 402 can circumvent the obstacle just by operating normally, without performing the circumvention action. If the control unit 8 determines that the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle upon when the detection values of the motor current detection circuit 72 reach the predetermined current value or above, the circumvention action may be performed unnecessarily. According to the configuration above, in the case where the detection values detected by the motor current detection circuit 72 remain at or above the predetermined current value for the predetermined duration or longer, the control unit 8 determines that the robotic mower 2, 202, 302, 402 is hindered from moving by an obstacle. That is, the circumvention action is performed only if the robotic mower 2, 202, 302, 402 remains hindered from moving by an obstacle for a certain period of time. This prevents the circumvention action from being performed unnecessarily. Thus, the work by the robotic mower 2, 202, 302, 402 can progress smoothly.

In one or more embodiments, the working unit 20 comprises the blade 46 configured to mow the lawn. The working robot functions as the robotic mower 2, 202, 302, 402.

According to the configuration above, the work by the robotic mower 2, 202, 302, 402 can progress smoothly.

Claims

1. A working robot configured to move and work autonomously, the working robot comprising: a robot body including a base and a bumper supported by the base;a working unit supported by the base;a movement mechanism configured to move the base;a movement motor configured to drive the movement mechanism;a first detection unit configured to detect a force that the bumper receives or displacement of the bumper relative to the base;a second detection unit configured to detect an angular velocity of the base or a state of the movement motor; anda control unit,whereinthe control unit is configured to determine, based on a detection result detected by the first detection unit and a detection result detected by the second detection unit, whether movement of the working robot is hindered by an obstacle.

2. The working robot according to claim 1, wherein the control unit is configured to execute: a first hindrance determination process of determining, based on at least the detection result detected by the first detection unit, whether the movement of the working robot is hindered by the obstacle;a circumvention process of controlling the movement motor such that the working robot performs a circumvention action to circumvent the obstacle after the control unit has determined that the movement of the working robot is hindered by the obstacle in the first hindrance determination process; anda second hindrance determination process of determining, based on at least the detection result detected by the second detection unit, whether the movement of the working robot is hindered by the obstacle while the working robot is performing the circumvention action.

3. The working robot according to claim 2, wherein the circumvention action includes a turning action in which the working robot turns.

4. The working robot according to claim 2, wherein the circumvention action includes a straight action in which the working robot moves straight.

5. The working robot according to claim 1, wherein the state of the movement motor includes a current flowing in the movement motor, andthe second detection unit includes a motor current detector configured to detect the current flowing in the movement motor.

6. The working robot according to claim 5, wherein in a case where a detection value detected by the motor current detector remains at or above a predetermined current value for a predetermined duration or longer, the control unit determines that the movement of the working robot is hindered by the obstacle.

7. The working robot according to claim 1, wherein the working unit comprises a blade configured to mow lawn, andthe working robot functions as a robotic mower.

8. The working robot according to claim 3, wherein the circumvention action further includes a straight action in which the working robot moves straight,the state of the movement motor includes a current flowing in the movement motor,the second detection unit includes a motor current detector configured to detect the current flowing in the movement motor,in a case where a detection value detected by the motor current detector remains at or above a predetermined current value for a predetermined duration or longer, the control unit determines that the movement of the working robot is hindered by the obstacle,the working unit comprises a blade configured to mow a lawn, andthe working robot functions as a robotic mower.