Patent Application
20090299525
This application claims priority under 35 U.S.C. 119 to Japanese Patent Application No. 2008-139236, filed on May 28, 2008, which application is hereby incorporated by reference in its entirety.
1. Technical Field
The present disclosure relates generally to a movement control of an autonomous moving body.
2. Description of Related Art
Recently, there has been proposed and developed a robot capable of providing various services in actual circumstances where a human body exists such as in offices, factories, and the like. Such a robot needs to have many functions, but one of the important functions required for such a robot is the ability to move autonomously to a destination.
The robot is required to move to the destination in a shorter period of time while avoiding collisions with obstacles such as a human body on the way to the destination. Known as an obstacle avoidance control applicable to a robot is a virtual potential method. In this virtual potential method, an attractive potential field with respect to a certain destination point and a repulsive potential field with respect to an obstacle to be avoided are generated and combined together, whereby a route to the destination point without accompanying collisions with the obstacles is generated.
When such service robot is actually operated, external circumstances such as surrounding obstacles can be detected by using, for example, a suitable detecting unit such as, but not limited to, a laser range finder, a stereo camera, or the like. Therefore, if the posture of the robot body is frequently changed in order to, for example, avoid the obstacles, the direction of the detecting unit is also changed resultantly. As a result, it takes a certain period of time for the robot to analyze the external circumstances, so that the robot may not promptly cope with the change of the external circumstances.
Furthermore, the service robot may transport objects such as loads or the like by hauling them. In such case, however, if the direction of the robot body is changed, the objects to be transported may be shaken greatly, and this may cause the objects to collide with the surroundings.
In accordance with one aspect by way of non-limiting example, there is provided an autonomous moving body having a configuration as follows. That is, the autonomous moving body includes: an omnidirectional moving mechanism; a detecting unit; and a movement control unit. The omnidirectional moving mechanism moves the moving body. The detecting unit can detect an obstacle. The movement control unit generates a movement instruction signal for avoiding the obstacle detected by the detecting unit while maintaining a frontal direction of the moving body to be substantially constant and transmitting the generated signal to the omnidirectional moving mechanism.
With this configuration, even in case that the moving body moves, for example, transversely to avoid the obstacle, the moving body is allowed to move without changing its frontal direction by using the omnidirectional moving mechanism. Accordingly, since there can be omitted a mechanism or various processes which would be necessitated if the frontal direction of the moving body were changed, a prompt and accurate movement control and a simple structure can be achieved.
In the autonomous moving body, the movement control unit may include, for example, a route calculating unit and a posture control unit. The route calculating unit may calculate a moving route along which the moving body is to move. The posture control unit may control a posture of the moving body. The posture control unit makes the frontal direction of the moving body substantially coincident with a direction of the moving route in any of a case where the moving body moves along the moving route and a case where the moving body moves in deviation from the moving route to avoid the obstacle detected by the detecting unit.
With this configuration, even in case that the moving body is deviated from the original moving route and moves, for example, transversely to avoid the obstacle, it is hardly necessary to correct the direction of the moving body after avoiding the obstacle. Therefore, the movement to the destination can be resumed promptly.
In the autonomous moving body, the moving body may transport, for example, an object to be transported, which is disposed at a rear side and/or a front side thereof.
With this configuration, even if the moving body is deviated from the original moving route and moves, for example, transversely to avoid the obstacle, the object to be transported is not much shaken from side to side because the frontal direction of the moving body is not changed. Accordingly, the object to be transported can be prevented from being shaken and colliding with the wall. Furthermore, in comparison with a conventional case where an independent two-wheel drive mechanism is employed, the sharp turn ability of the moving body can be remarkably improved, so that the moving body can move in any direction in any posture. Therefore, the moving body and the object to be transported can be easily prevented from interfering with a nearby moving body (obstacle), so that a smart movement control without obstructing a way of the nearby moving body can be achieved.
In the autonomous moving body, the detecting unit faces toward the frontal direction of the moving body, for example.
With this configuration, for example, the obstacle approaching the moving body from the front side thereof during the forward movement of the moving body can be successfully detected by the detecting unit, and the avoidance operation can be appropriately and securely performed while keeping the detecting unit facing forward.
In another aspect, there is provided a method for controlling a movement of an autonomous moving body. That is, the autonomous moving body, which is controlled by the movement control method, may include, for example, an omnidirectional moving mechanism and a detecting unit. The omnidirectional moving mechanism may move the moving body. The detecting unit can detect an obstacle. Further, the movement control method of the autonomous moving body may include, for example, a first step and a second step. In the first step, the obstacle can be detected by the detecting unit. In the second step, when it is necessary to avoid the detected obstacle, a movement instruction signal for avoiding the detected obstacle while maintaining a frontal direction of the moving body to be substantially constant is generated and the generated signal is transmitted to the omnidirectional moving mechanism.
In accordance with this method, even in case the moving body moves, for example, transversely to avoid the obstacle, the moving body is allowed to move without changing its frontal direction by using the omnidirectional moving mechanism. Accordingly, since there can be omitted a mechanism or various processes which would be necessitated if the direction of the moving body were changed, a prompt and accurate movement control and a simple structure can be achieved.
Other features, elements, processes, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description with reference to the attached drawings.
Hereinafter, illustrative embodiments will be described.
By way of example, but not limitation, the service robot 11, as an autonomous moving body shown in
The main body 12 has, for example, a thinly elongated shape in a vertical direction, and the omni-wheel mechanism 13 for allowing the robot to be self-propelled can be installed at a position such as a lower end portion of the main body 12. Examples of the omni-wheel mechanism 13 that can be used herein include, but are not limited to, four omni-wheels 21 arranged at an angular interval of about 90° along the circumferential direction thereof and four motors 22 installed to correspond to the respective omni-wheels 21.
Now, an example configuration of the omni-wheel mechanism 13 will be described in detail with reference to
An illustrative example of the omni-wheel mechanism 13 has four wheel driving units 23 arranged at a bottom surface of the main body 12, as shown in
In an illustrative example, the motor 22 can include a housing 26 for rotatably supporting a non-illustrated rotor, and the housing 26 can be disposed inside the motor supporting frame 24. An example of an output shaft 27 of the motor 22 may protrude outwardly from the motor supporting frame 24, and the omni-wheel 21 is installed at, for example, an end portion of the output shaft 27. In some embodiments, the omni-wheel 21 in each wheel driving unit 23 may be arranged such that its rotation shaft lies at an angle of about 45° or 135° with respect to the frontal direction of the robot 11.
In an illustrative example, each omni-wheel 21 may include a roller-shaped main body 31 fixed to the output shaft 27 of the motor 22 and a plurality of free rollers 32 arranged at the outer periphery of the main body 31. The free rollers 32 can be rotatably supported by the main body 31, and the outer peripheral surface of each free roller 32 can be configured to make contact with a ground surface. Further, a rotation axis of the free roller 32 can be approximately perpendicular to a rotation axis of the main body 31.
With this configuration, if the motor 22 is driven and the main body 31 is resultantly rotated, the free rollers 32 are rotated integrally with the main body 31, so that their driving forces are transferred to the ground surface. Meanwhile, as the free rollers 32 in contact with the ground surface are rotated, the omni-wheel 21 can easily move along a direction parallel to the rotation axis of the main body 31. With the above-described configuration, omnidirectional movements of the robot 11 can be achieved.
In some embodiments, the motors 22 of the four wheel driving units 23 may independently control rotational directions and rotational speeds of the four omni-wheels 21 based on a travel instruction (movement instruction) from the travel controller 15, whereby a control for moving the robot 11 in any direction (omnidirectional movement control) can be carried out.
In an illustrative example, the laser range finder 14 shown in
A cart 17, which is an object to be transported (i.e., an object to be hauled), is disposed, for example, behind the main body 12 of the robot 11. In some embodiments, the cart 17 can be provided with casters 18 at its bottom portion and can be connected to a rear portion of the main body 12 via a connecting member 19. Further, the connecting member 19 may fix the cart 17 integrally to the main body 12, and a so-called variable joint-type connecting member or the like need not be used in some embodiments.
Now, the travel controller 15 will be described in conjunction with
In certain embodiments, the travel controller 15 can be implemented in a microcomputer and include, though not illustrated in the drawing, a CPU as an operating unit, a ROM and a RAM as storage units, and so forth. Further, a control program for implementing autonomous movements of the robot 11 can be stored in the ROM, for example.
As shown in
The map storage unit 51 may store therein a map showing stationary obstacles (obstacles which do not disappear or do not change their positions) within the moving range of the robot 11. To create this map, the ambient surroundings may be scanned by, e.g., the laser range finder 14 while moving the robot 11 in a state where all moving obstacles such as a human body or the like are removed. The robot 11 may recognize the position and the shape of the stationary obstacle, and then automatically create the map and store the map in a suitable memory.
The destination position storage unit 52 may store therein information on a destination position which the robot 11 is to reach. For example, the destination position is designated by manipulating the robot 11 by an operator and is stored as coordinates on the map.
The robot body information obtaining unit 53 may calculate and obtain the position and the speed of the robot body, and also calculate and obtain which direction the frontal side of the robot body is facing toward (i.e., posture angle). In one embodiment by way of non-limiting example, the robot body information is decided after collectively considering a result of collating the surrounding obstacle information obtained by the laser range finder 14 with the map and rotational angle information of the output shaft 27 of each motor 22 of the omni-wheel mechanism 13. Further, the rotational angle of the output shaft 27 of the motor 22 can be obtained by a non-illustrated encoder installed at the output shaft 27.
The obstacle information obtaining unit 54 may detect a stationary or moving obstacle, which is not shown on the environment map of the robot, by means of the laser range finder 14 during the operation of the robot, and obtains the position and the speed of the detected obstacle.
The route calculating unit 61 may calculate a route to the destination position based on the position of the robot body, which is obtained by the robot body information obtaining unit 53, and the map. Further, in case that an obstacle is detected by the obstacle information obtaining unit 54 and it is determined that the robot needs to avoid the obstacle, the route calculating unit 61 calculates a direction and a speed for moving the robot body in order to avoid the obstacle. Further, such calculation can be performed based on a well-known virtual potential method.
The frontal direction control unit 64 may receive the route information obtained by the route calculating unit 61 and the current robot body posture angle information obtained by the robot body information obtaining unit 53, and then it may calculate a rotation amount of the robot body necessary to make a front surface of the robot 11 face toward the direction of the route.
The travel instruction transmitting unit 65 may generate a travel instruction for moving and rotating the robot body based on the route (or direction and speed for avoiding the obstacle) obtained by the route calculating unit 61 and the rotation amount obtained by the frontal direction control unit 64. Then, by transmitting the travel instruction to the omni-wheel mechanism 13, the robot 11 is allowed to travel.
Now, the movement control and the posture angle control of the robot 11 will be described in detail with reference to
As illustrated in
In an illustrative embodiment, the robot 11 can be moved in a designated direction θ and rotated at a designated angle dφ by transmitting a driving signal to the motors 22 so as to obtain the moving amount ci of each omni-wheel 21 as shown in the equation (2) of
Now, an obstacle avoidance control will be described in detail with reference to
In
Assume that the robot 11 detects the obstacle 16 at a position A in
By this control, the robot 11 in accordance with an illustrative embodiment can avoid the obstacle 16 while hardly changing the frontal direction of the robot body, as illustrated in
Furthermore, in case of a conventional robot 91 having a travel unit of an independent two-wheel mechanism type as shown in
As stated above, in some embodiments, the robot 11 includes the omni-wheel mechanism 13, the laser range finder 14 and the travel controller 15. The omni-wheel mechanism 13 allows the robot body to move. The laser range finder 14 is configured to detect the obstacle 16. The travel controller 15 generates a movement instruction signal for avoiding the obstacle 16 detected by the laser range finder 14 without changing the frontal direction of the robot body and transmits the signal to the omni-wheel mechanism 13.
Furthermore, in some embodiments, the robot 11 performs a movement control by a method including, but not limited to, the following steps. In a first step, the obstacle 16 is detected by the laser range finder 14. In a second step, if it is necessary to avoid the detected obstacle 16, a movement instruction signal for avoiding the obstacle 16 without changing the frontal direction of the robot body is generated and it is transmitted to the omni-wheel mechanism 13.
With this control, even in case the robot body moves, for example, transversely to avoid the obstacle, the robot body is allowed to move without changing its frontal direction by using the omni-wheel mechanism 13. Accordingly, since there can be omitted a mechanism (e.g., the above-mentioned detector direction control mechanism) or various processes (e.g., a re-recognition process required as a result of a great variation in the angle of the laser range finder 14) which would be necessitated if the direction of the robot body were changed, a prompt and accurate movement control and a simplification of robot structure can be achieved.
Furthermore, in the robot 11 of an illustrative embodiment, the travel controller 15 includes the route calculating unit 61 and the frontal direction control unit 64. The route calculating unit 61 calculates the moving route R1 along which the robot body should move. The frontal direction control unit 64 controls the posture of the robot body. The frontal direction control unit 64 controls the frontal direction of the robot body such that it substantially coincides with the direction of the moving route R1 in any of a case where the robot body moves along the moving route R1 and a case where the robot body moves in deviation from the moving route R1 to avoid the obstacle 16 detected by the laser range finder 14.
Accordingly, even in case that the robot body is deviated from the original moving route R1 and moves, for example, transversely to avoid the obstacle 16, it is hardly necessary to correct the direction of the robot body after avoiding the obstacle. Therefore, the movement to the destination can be resumed promptly.
Further, in some embodiments, the robot 11 is configured to haul and transport the cart 17 disposed at the rear side of the robot body.
Accordingly, even in case that the robot body is deviated from the original moving route R1 and moves, for example, transversely to avoid the obstacle 16, the cart 17 is not much shaken from side to side because the frontal direction of the robot body is not changed. Accordingly, the cart 17 can be prevented from being shaken and colliding with the wall, as illustrated by the dashed line B of
Furthermore, in the robot 11 of an illustrative embodiment, the laser range finder 14 is disposed to face toward the frontal direction of the robot body.
With this configuration, the obstacle 16 approaching the robot body from the front side of the robot body during the forward movement of the robot body can be successfully detected by the laser range finder 14, and the avoidance operation can be appropriately and securely performed while keeping the laser range finder 14 facing forward.
Though the illustrative embodiments have been described so far, the above-described configuration can be modified as follows, for example.
The direction of the laser range finder 14 is not limited to the frontal direction of the robot 11. For example, it may be possible to set up a configuration in which a pair of laser range finders are provided on left and right sides of the robot so as to face toward the left and right outer sides thereof. Furthermore, in case that the autonomous moving body such as the robot has an appearance of which the frontal direction is difficult to define, the direction in which the robot moves in response to a straightforward movement instruction may be defined as the frontal direction.
Moreover, in lieu of or in addition to the laser range finder 14, the robot 11 may be provided with a stereo camera, a monocular camera, an ultrasonic sensor, an infrared sensor or the like, to detect the obstacle 16 with such device.
The configuration of the omni-wheel mechanism 13 for moving the robot 11 can be modified such that six or three omni-wheels are arranged thereat instead of four omni-wheels 21.
Furthermore, the cart 17 can be disposed at the front side of the robot 11 instead of the rear side thereof. In such case, by controlling the frontal direction of the robot body not to be changed when the robot body avoids the obstacle, it is also possible to prevent the collision of the cart with its surrounding environment which may be caused by the shaking of the cart. In addition, other types of objects to be transported can be employed instead of the cart 17, or the cart 17 can be omitted.
The control described in the above embodiment is not limited to the service robot 11, but it can be applied to the autonomous movement control of, for example, a self-propelled transportation carriage equipped with an omnidirectional moving mechanism such as, but not limited to, an omni-wheel mechanism.
While various aspects and embodiments have been described herein, it will be apparent to those skilled in the art that the disclosed embodiments may be modified in numerous ways and may assume many embodiments other than those specifically set out and described above. Accordingly, it is intended by the appended claims to cover all modifications of the invention that fall within the true spirit and scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-139236 | May 2008 | JP | national |
