WORK MACHINE STEERING CONTROL SYSTEM AND WORK MACHINE STEERING CONTROL METHOD

TECHNICAL FIELD

This disclosure relates to a steering control system and a steering control method for work machines.

BACKGROUND ART

The motor grader is a work machine equipped with multiple control levers. Such a work machine may demand considerable skills and experiences to be handled and controlled. During the ongoing work, the vehicular body of this work machine may be likely to wobble from side to side under the impact of biased blade load, which may often require the skill generally called, “meeting rudder”, to keep the machine's straight forward movement.

In the meantime, automated steering systems using satellite positioning systems such as GNSS (Global Navigation Satellite System) are growingly developed and commercialized mostly for agricultural machines. U.S. Pat. No. 8,060,299 (patent literature 1) describes an example of motor graders installed with such systems.

CITATION LIST
Patent Literature

- Patent literature 1: U.S. Pat. No. 8,060,299

SUMMARY OF INVENTION
Technical Problem

In such automated steering systems as described in the mentioned literature, an operator may want to make fine adjustments of the course of motor grader 100 upon his/her preference or due to any deviation of the course resulting from possible detection errors of sensors. In these or similar situations, such course adjustments may desirably be performed as easily and finely as possible.

This disclosure is directed to providing a steering control system and a steering control method for work machines that can successfully facilitate fine course adjustments.

Solution to Problem

A steering control system of this disclosure is a system for a work machine including: a steering mechanism; a directional correction input device; and a controller. The steering mechanism is for control of a direction of travel of the work machine. The directional correction input device is operated by an operator. The controller, during automatic control of a steering operation by the steering mechanism, controls the steering mechanism in a manner that the direction of travel is adjustable through a certain angle toward one of lateral sides based on an operation command inputted through the directional correction input device.

A work machine steering control method of this disclosure is a method for a work machine including: a steering mechanism used for control of a direction of travel of the work machine; and a directional correction input device operated by an operator. The method includes the following steps.

One of the steps is executing automatic control of a steering operation by the steering mechanism. The other step is controlling the steering mechanism during the automatic control in a manner that the direction of travel is adjustable through a certain angle toward one of lateral sides based on an operation command inputted through the directional correction input device.

Advantageous Effects of Invention

The work machine steering control system and the work machine steering control method of this disclosure may successfully facilitate fine course adjustments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view that schematically illustrates a work machine according to an embodiment of this disclosure.

FIG. 2 is a lateral view of the work machine of FIG. 1.

FIG. 3 is a block diagram that illustrates exemplified structural features of a steering control system for the work machine of FIG. 1.

FIG. 4 is a block diagram that illustrates functional blocks of the steering control system for the work machine of FIG. 1.

FIG. 5 is a flow chart of an exemplified steering control method for the work machine in a first mode (steering stabilizer mode) according an embodiment of this disclosure.

FIG. 6 is a drawing that illustrates a steering control in the first mode performed in a manner that a direction of travel is maintainable.

FIG. 7 is a drawing that illustrates a direction of travel being adjusted through a certain angle either rightward or leftward based on an operation command inputted through a directional correction input device.

FIG. 8 is a drawing that illustrates pseud offset of a travel course during the steering control in the first mode.

FIG. 9 is a flow chart of an exemplified steering control method for the work machine in a second mode (auto-steering mode) according an embodiment of this disclosure.

DESCRIPTION OF EMBODIMENTS

Embodiments of this disclosure are hereinafter described in detail referring to the accompanying drawings. In the description below and the accompanying drawings, identical or similar structural elements are simply illustrated with the same reference signs, redundant description of which may be skipped. For illustration purpose, a structural or technical feature(s) may be illustrated in a simplified manner or may be left unillustrated.

This disclosure may also be applicable to other work machines including hydraulic excavators, wheel loaders, crawler dozers and forklifts in addition to motor graders. In the description below, directional terms that indicate “upper side”, “lower side”, “rear side”, “front side”, “left side” and “right side”, refer to directions based on an operator seated in an operator's seat 11S in an operator's cab 11 illustrated in FIG. 1.

First, a motor grader; an example of the work machine used in this embodiment, is hereinafter described with reference to FIGS. 1 and 2.

FIGS. 1 and 2 are respectively a perspective view and a lateral view that schematically illustrate a work machine according to an embodiment of this disclosure. As illustrated in FIG. 1, a motor grader 100 is a work machine driven to travel, while performing, for example, land grading or snow clearing.

Motor grader 100 includes a front frame 14, a rear frame 15, a pair of left and right articulate cylinders 28, an operator's cab (cab) 11, an engine cover 13, front wheels 16, rear wheels 17, and a work implement 12.

Front frame 14 and rear frame 15 form a body frame 18 of motor grader 100. Front frame 14 is disposed on the front side relative to rear frame 15.

Front frame 14 is pivotally coupled to rear frame 15 with center pins, not illustrated in the drawings, fitted on an axis 121 which is the pivotal center. The pivotal center; axis 121, extends along the vertical direction.

Articulate cylinders 28 are disposed in a pair on lateral sides across front frame 14. Articulate cylinders 28 are hydraulic cylinders extendable and contractible under hydraulic pressure. The telescopic motion of articulate cylinders 28 allow front frame 14 to pivot around the pivotal center; axis 121, relative to rear frame 15.

Engine cover 13 is used to cover an engine compartment and is supported by rear frame 15. In the engine compartment are disposed, for example, a transmission, torque converter, engine, and structure for exhaust treatment.

Front wheels 16 and rear wheels 17 are running wheels. Front wheels 16 are pivotally attached to front frame 14. Front wheels 16 are steering wheels and are attached to front frame 14 in a steerable manner. Rear wheels 17 are pivotally attached to rear frame 15. A driving force transmitted from the engine is conveyed to rear wheels 17.

Work implement 12 is disposed at a position in the fore/aft direction between front wheels 16 and rear wheels 17. Work implement 12 is supported by front frame 14. Work implement 12 is equipped with a blade 21, a drawbar 22, a swing circle 23, and a pair of lift cylinders 25.

Drawbar 22 is disposed at a position below front frame 14. The front end of drawbar 22 is coupled in a swingable manner to a distal end of front frame 14. Paired lift cylinders 25 are disposed on lateral sides across front frame 14. The rear end of drawbar 22 is supported by front frame 14 through paired lift cylinders 25.

In response to the telescopic motion of paired lift cylinders 25, the rear end of drawbar 22 is allowed to move upward and downward relative to front frame 14. The height of blade 21 relative to front frame 14 and front wheels 16 is adjustable to a greater height in response to contraction of paired lift cylinders 25. The height of blade 21 relative to front frame 14 and front wheels 16 is adjustable to a smaller height in response to extension of paired lift cylinders 25.

As paired lift cylinders 25 are extendable and contractible in different manners, drawbar 22 is allowed to swing upward and downward around an axis extending in the fore/aft direction.

Swing circle 23 is disposed at a position below drawbar 22. Swing circle 23 is coupled to drawbar 22 in a swingable manner. Swing circle 23 is allowed to swing clockwise and counterclockwise around an axis extending in the vertical direction.

Blade 21 is disposed at a position below swing circle 23. Blade 21 is disposed so as to face the ground. Blade 21 is supported by swing circle 23. Blade 21 is allowed to swing in response to the swing motion of swing circle 23, with the angle of blade 21 relative to the fore/aft direction (blade propulsive angle) being changeable when viewed from the upper side. The axis of swing of blade 21 is an axis extending in the vertical direction.

As illustrated in FIG. 2, motor grader 100 further has a handle sensor 31, a lever sensor 32, an automatic control device 33, a direction sensor 34, a directional correction input device 36, and an FNR/vehicle speed sensor 37.

Handle sensor 31 detects the handling operation of steering handle 41 (FIG. 3) by an operator. Handle sensor 31 may be, for example, an axis displacement sensor that detects angle changes of the steering handle's axis that occur in response to the rotation of steering handle 41.

Lever sensor 32 detects the handling operation of a steering lever 42 (FIG. 3) by an operator. Lever sensor 32 may be, for example, a position sensor that detects the angular position of steering lever 42.

Automatic control device 33 may be disposed, for example, in operator's cab 11. Automatic control device 33, an example of which is a switch(es), is controllable by an operator. Automatic control device 33, when controlled by an operator, generates a signal for start of automatic steering control of motor grader 100 (hereinafter, may be referred to as “start signal”) or a signal for stoppage of automatic steering control of motor grader 100 (hereinafter, may be referred to as “stoppage signal”). This automatic steering control will be described later.

Direction sensor 34 detects a direction in which body frame 18 of motor grader 100 is turned and currently positioned. Direction sensor 34 may be, for example, one of an IMU (Inertial Measurement Unit) 34a, a steering angle sensor 34b, an articulate angle sensor 34c and an imaging device 34d, or may include two or more of these sensors and/or device optionally selected and combined.

IMU 34a may be attached to, for example, front frame 14. IMU 34a, an example of which is a hexaxial IMU, may also be a nine-axis IMU. The hexaxial IMU is a combined sensor installed with a triaxial accelerator and a triaxial gyroscope (angle, angular rate or angular acceleration). This IMU is attachable to front frame 14 so that these three axes respectively extend along the fore/aft direction, lateral direction and vertical direction of the work machine. In this instance, the hexaxial IMU is operable to detect positional changes along the axes in the fore/aft direction, lateral direction and vertical direction, and angular changes around these axes (i.e., work machine's rolling, pitching and yawing). The nine-axis IMU is a combined sensor installed with a triaxial accelerator, a triaxial gyroscope and a triaxial magnetometer. The nine-axis IMU, which measures geomagnetism using the triaxial magnetometer, may more effectively control any gyroscopic drift than the hexaxial IMU.

Changes in the current direction of motor grader 100 may be accurately known based on the acceleration and gyroscopic data detected by IMU 34a. IMU 34a may be attached to rear frame 15 or operator's cab 11.

Steering angle sensor 34b may be attached to, for example, a steering cylinder 74. Steering angle sensor 34b detects the steering angle of front wheels 16 (angle made by front wheels 16 to the fore/aft direction of front frame 14).

Articulate angle sensor 34c may be attached to, for example, articulate cylinder 28. Articulate angle sensor 34c detects the articulate angle (angle of joint) of front frame 14 and rear frame 15.

Imaging device 34d may be disposed, for example, in operator's cab 11. Imaging device 34d captures images of, for example, motor grader 100 in part and of its surroundings. The images captured by imaging device 34d may also help to know changes in the current direction of motor grader 100.

Directional correction input device 36 may be disposed, for example, in operator's cab 11. Directional correction input device 36 may be, for example, a switch pressed by an operator, an example of which is a push-button switch including a pair of left and right buttons. In a first mode described later (steering stabilizer mode), directional correction input device 36, every time when used (pressed) by an operator, adjusts the direction of travel of motor grader 100 through a certain angle leftward or rightward. In a second mode described later (auto-steering mode), directional correction input device 36 offsets a predefined travel course leftward or rightward by a predetermined amount relative to the direction of travel of motor grader 100.

FNR/vehicle speed sensor 37 may be attached to, for example, a transmission (not illustrated in the drawings). FNR/vehicle speed sensor 37 detects the statuses of motion; forward (F), reverse (R) and neutral (N) and also detects the vehicle speed of traveling motor grader 100.

Motor grader 100 may utilize the satellite positioning system. The GNSS, for example, may be employed as the satellite positioning system. When the GNSS is employed as the satellite positioning system, motor grader 100 may be further equipped with a GNSS receiver 35 and a mode selector 38.

GNSS receiver 35 may be, for example, a receiver for GPS (Global Positioning System). The antenna of GNSS receiver 35 may be, for example, installed in the ceiling of operator's cab 11. GNSS receiver 35 obtains, from the satellite, a positioning signal. Then, the position of the antenna of GNSS receiver 35 is calculated based on the positioning signal to generate position data of the vehicular body. Thus, the satellite positioning system may be useful for knowing, as well as changing positions of motor grader 100, the current position and current direction (current orientation) of motor grader 100 in the earth-based global coordinate system.

Mode selector 38 may be disposed, for example, in operator's cab 11. Mode selector 38 is operated by an operator to allow the automatic steering control (automated steering) to shift to and from the first mode (steering stabilizer mode) and the second mode (auto-steering mode).

The first mode is a mode in which the steering action of motor grader 100 is automatically controlled (automated steering) to keep the direction of travel straight forward. In this mode, the satellite positioning system is not used. The second mode is a mode in which the steering action of motor grader 100 is automatically controlled (automated steering) to follow a predefined travel course using the satellite positioning system. The first mode may be a relatively simple mode as compared with the second mode. In case the vehicular body happen to wobble from side to side under the impact of biased blade load, straight forward movement may be maintained without such an additional labor as meeting rudder. This may greatly reduce an operator's burden during the work.

When, in the first mode selected and set, an operator presses the right button of directional correction input device 36, the direction of travel of motor grader 100 is adjustable toward the right side through a certain angle. When an operator presses the left button of directional correction input device 36, the direction of travel of motor grader 100 is adjustable toward the left side through a certain angle.

In the second mode selected and set, directional correction input device 36 functionally operate as an offset switch. Specifically, when the right button of directional correction input device 36 is pressed, a predefined travel course is offset toward the right side by a predetermined amount. When the left button of directional correction input device 36 is pressed, on the other hand, a predefined travel course is offset toward the left side by a predetermined amount.

Next, a steering control system according to this embodiment is hereinafter described with reference to FIG. 3.

FIG. 3 is a block diagram that illustrates exemplified structural features of a steering control system for the work machine of FIG. 1. As illustrated in FIG. 3, the steering control system includes a controller 40, a steering mechanism 66, a steering controller 67, and an electrofluid pressure control valve 73.

Steering controller 67 is handled and controlled by an operator to activate a steering mechanism 66. Steering controller 67 includes handle sensor 31, lever sensor 32, steering handle 41, steering lever 42, and a steering pilot valve 71.

Steering handle 41 may have, for example, a wheel-like shape and is held and rotated by an operator. Handle sensor 31 detects steering handle 41 being rotated by the operator. Handle sensor 31 may be, for example, an axis displacement sensor that detects angle changes of the steering handle's axis that occur in response to the rotation of steering handle 41. Sensing signals of handle sensor 31 are outputted, as electrical signals, to controller 40.

Steering lever 42 may be, for example, a joystick, which is leaned in different directions by an operator. Lever sensor 32 detects the operator's handling operation of steering lever 42. Lever sensor 32 may be, for example, a position sensor that detects the angular position of steering lever 42. Sensing signals of lever sensor 32 are outputted to controller 40 as electrical signals.

Steering pilot valve 71 feeds a steering valve 72 with a pressurized oil in response to the pivotal motion of steering handle 41.

Steering mechanism 66 is used to control the direction of travel of motor grader 100. Steering mechanism 66 has steering valve 72, steering cylinder 74, and steering angle sensor 34b.

Steering valve 72 is controllable depending on the pressurized oil fed from electrofluid pressure control valve 73 and steering pilot valve 71. Steering valve 72 controls the pressurized oil to be fed to steering cylinder 74.

Steering cylinder 74 is extendible and contractible by the pressurized oil from steering valve 72. The angle of front wheels 16 relative to the fore/aft direction changes in response to the telescopic motion of steering cylinder 74.

Controller 40 controls electrofluid pressure control valve 73 based on sensing signals from handle sensor 31 and lever sensor 32. Thus, steering cylinder 74 is extendable and contractible in response to the control of steering handle 41 or steering lever 42 by an operator, and the angle of front wheels 16 relative to the fore/aft direction accordingly changes.

When front wheels 16 are leaned rightward relative to the fore/aft direction, motor grader 100 changes its direction of travel, starting to move forward toward the right side. When front wheels 16 are leaned leftward relative to the fore/aft direction, motor grader 100 changes its direction of travel, starting to move forward toward the left side.

As described thus far, steering mechanism 66 is driven to operate manually in response to the operation of steering controller 67 by an operator. During the manual operation, motor grader 100 travels exactly as handled and operated by an operator.

Controller 40 automatically controls electrofluid pressure control valve 73 based on electrical signals. The electrical signals are inputted to controller 40 from automatic control device 33, direction sensor 34, GNSS receiver 35, directional correction input device 36, FNR/vehicle speed sensor 37, and mode selector 38. Controller 40 controls electrofluid pressure control valve 73 based on these electrical signals to enable automated steering of motor grader 100.

Next, functional blocks of the steering control system for the work machine are hereinafter described with reference to FIG. 4.

FIG. 4 is a block diagram that illustrates functional blocks of the steering control system for the work machine of FIG. 1. As illustrated in FIG. 4, controller 40 includes a lever sensor measurement value obtainer 40a, a handle sensor measurement value obtainer 40b, and a steering command signal generator 40d.

Lever sensor measurement value obtainer 40a outputs sensing signals obtained from lever sensor 32 to steering command signal generator 40d. Handle sensor measurement value obtainer 40b outputs sensing signals obtained from handle sensor 31 to steering command signal generator 40d.

Steering command signal generator 40d controls electrofluid pressure control valve 73 based on the sensing signals obtained from lever sensor measurement value obtainer 40a or the handle sensor measurement value obtainer 40b.

Thus, steering mechanism 66 is driven to operate in response to the operation of steering controller 67 by an operator; manual operation.

Controller 40 further includes a directional signal obtainer 40c, a start/stoppage signal obtainer 40e, a start/stoppage determiner 40f, and a current direction identifier 40g. Directional signal obtainer 40c outputs, to current direction identifier 40g, a signal indicating the current direction (hereinafter, may be referred to as “directional signal”) obtained from direction sensor 34. The directional signal obtained by directional signal obtainer 40c from direction sensor 34 (34a, 34d) is a signal indicating any change of the current direction relative to a direction at a certain time point (reference direction, i.e., a signal indicating a relative directional change). This directional signal is irrelevant to orientations in the global coordinate system obtained by GNSS receiver 35 (i.e., absolute directions, e.g., north, south, east, west).

Start/stoppage signal obtainer 40e obtains, from automatic control device 33, an automated steering start signal or an automated steering stoppage signal in the first, second mode and then outputs the obtained signal to start/stoppage determiner 40f. Lever sensor measurement value obtainer 40a and handle sensor measurement value obtainer 40b output the sensing signals to start/stoppage determiner 40f.

Start/stoppage determiner 40f, based on the obtained start signal, stoppage signal or sensing signal, determines whether the automated steering of motor grader 100 should start or stop.

Specifically, start/stoppage determiner 40f determines that the automated steering of motor grader 100 should start in response to receipt of the start signal from start/stoppage signal obtainer 40e. Specifically, start/stoppage determiner 40f, in response to receipt of the stoppage signal from start/stoppage signal obtainer 40e, determines that the automated steering of motor grader 100 should discontinue.

When the operation of handle steering lever 42 by an operator is detected as being suspended for a predetermined period of time based on the sensing signal from lever sensor 32, start/stoppage determiner 40f determines that the automated steering should start. Start/stoppage determiner 40f determines that the automated steering should discontinue in response to receipt of the sensing signal indicating that lever sensor 32 has been used by an operator during the automated steering.

When the operation of steering handle 41 by an operator is detected as being suspended for a predetermined period of time based on the sensing signal from handle sensor 31, start/stoppage determiner 40f determines that the automated steering should start. Start/stoppage determiner 40f determines that the automated steering should discontinue in response to receipt of the sensing signal indicating that handle sensor 31 has been used by an operator during the automated steering.

In the first mode selected and set, start/stoppage determiner 40f outputs, to current direction identifier 40g, a signal indicating the result of determination; start or stoppage of automated steering. In response to receipt of, from start/stoppage determiner 40f, the result of determination requesting the start of automated steering, current direction identifier 40g identifies the current direction of motor grader 100 based on the directional signal obtained from directional signal obtainer 40c.

Current direction identifier 40g, when obtaining a signal from IMU 34a serving as direction sensor 34, identifies the current direction of motor grader 100 based on gyroscopic information and an acceleration rate detected by IMU 34a.

Current direction identifier 40g, when obtaining a signal from imaging device 34d serving as direction sensor 34, identifies the current direction of motor grader 100 based an image(s) captured by imaging device 34d.

Current direction identifier 40g outputs a signal indicating the identified current direction to steering command signal generator 40d. In response to receipt, from start/stoppage determiner 40f, of the result of determination requesting the stoppage of automated steering, current direction identifier 40g generates a signal indicating the obtained result and outputs the generated signal to steering command signal generator 40d.

Steering command signal generator 40d, based on the signal indicating the current direction obtained from current direction identifier 40g, controls electrofluid pressure control valve 73 so that motor grader 100 travels along the current direction identified as its target direction.

Then, automated steering in the first mode (steering stabilizer mode) during the travel is started based on one of the following events as a trigger; the control of automatic control device 33 by an operator is confirmed, or the control of steering lever 42 or steering handle 41 by an operator is suspended for a predetermined period of time. During the automated steering in this first mode, the current direction of motor grader 100 when the automated steering was started is maintained as its target direction. In case the vehicular body of motor grader 100 wobbles from side to side under the impact of biased blade load, automated steering may allow motor grader 100 to travel straight forward along the target direction.

In response to receipt of the result of determination requesting the stoppage of automated steering from current direction identifier 40g, steering command signal generator 40d discontinues the automated steering based on the received signal. In this instance, steering command signal generator 40d controls electrofluid pressure control valve 73 based on the sensing signal from handle sensor 31 or lever sensor 32. Steering command signal generator 40d accordingly discontinues the automated steering. When the automated steering is thus stopped, motor grader 100 starts to be manually driven as described below.

To enable automated steering in the second mode, controller 40 may further include a GNSS signal obtainer 40j and a position/orientation obtainer 40k. GNSS signal obtainer 40j obtains the position data and orientation data of motor grader 100 from GNSS receiver 35 and outputs the obtained data to position/orientation obtainer 40k.

The position data of motor grader 100 obtained by position/orientation obtainer 40k represents the position of motor grader 100 defined in the global coordinate system. The orientation data of motor grader 100 obtained by position/orientation obtainer 40k may represent, for example, a direction forward of motor grader 100.

In the second mode selected and set, start/stoppage determiner 40f outputs, to position/orientation obtainer 40k, a signal indicating the result of determination; start or stoppage of automated steering. In response to receipt of the result of determination requesting the start of automated steering from start/stoppage determiner 40f, position/orientation obtainer 40k outputs, to steering command signal generator 40d, the position data and orientation data of motor grader 100 obtained from GNSS signal obtainer 40j.

Based on the position data and orientation data obtained from position/orientation obtainer 40k and a travel course previously set and stored in storage 40n (target course), steering command signal generator 40d controls electrofluid pressure control valve 73 so that motor grader 100 travels along this travel course previously set and stored.

Then, automated steering in the second mode (auto-steering mode) during the travel is started based on one of the following events as a trigger; the control of automatic control device 33 by an operator is confirmed, or the control of steering lever 42 or steering handle 41 by an operator is suspended for a predetermined period of time. During the automated steering in this second mode, motor grader 100 is navigated to follow the travel course generated using the satellite positioning system.

Whether automated steering in the first mode or automated steering in the second mode is carried out may be selected through mode selector 38. When the first mode is selected through mode selector 38, steering command signal generator 40d obtains a signal indicating the current direction from current direction identifier 40g. Steering command signal generator 40d controls electrofluid pressure control valve 73 so that automated steering in the first mode is carried out based on the signal indicating the current direction obtained from current direction identifier 40g.

When the second mode is selected through mode selector 38, steering command signal generator 40d obtains a signal indicating position data and orientation data from position/orientation obtainer 40k and a travel course-indicating signal from storage 40n. Steering command signal generator 40d controls electrofluid pressure control valve 73 so that motor grader 100 travels along the indicated travel course indicated under automated steering in the second mode.

Controller 40 further includes a direction corrector 40h, a directional correction command obtainer 40i, and a storage 40n. Directional correction command obtainer 40i obtains signals from directional correction input device 36 and FNR/vehicle speed sensor 37 and then outputs these signals to current direction identifier 40g and direction corrector 40h.

Current direction identifier 40g identifies whether the current direction is forward or backward based on the signal obtained from directional correction command obtainer 40i.

In the first mode, direction corrector 40h calculates a corrected direction. The corrected direction is the direction of travel of motor grader 100 (target direction) that has been corrected leftward or rightward through a certain angle based on the signal obtained from directional correction command obtainer 40i. Direction corrector 40h, at the time of calculating the corrected direction, may consult angle-related information (for instance, angle value) stored in storage 40n. The angle-related information stored in storage 40n may include, for example, a tabulated list of corrected angles suitable for vehicle speeds in the forward and backward movements. Direction corrector 40h outputs a signal indicating the corrected direction thus calculated to steering command signal generator 40d.

In the second mode, direction corrector 40h offsets the travel course of motor grader 100 leftward or rightward relative to the direction of travel through a certain angle based on the signal obtained from directional correction command obtainer 40i. Direction corrector 40h, for offset of the travel course, consults travel course-related information previously set and stored in storage 40n. In response to receipt of a signal indicating the right button being pressed through directional correction input device 36, direction corrector 40h offsets the travel course rightward relative to the direction of travel of motor grader 100. In response to receipt of a signal indicating the left button being pressed through directional correction input device 36, direction corrector 40h offsets the travel course leftward relative to the direction of travel of motor grader 100. Direction corrector 40h outputs a signal indicating the offset travel course to steering command signal generator 40d.

Directional correction input device 36 serve two different functional features in the first and second modes with one button. Specifically, directional correction input device 36 has two features available in two modes; correction of the direction of travel of motor grader 100 in the first mode, and offset of the travel course in the second mode.

In the first mode, steering command signal generator 40d, based on the signal indicating the current direction obtained from direction corrector 40h, controls electrofluid pressure control valve 73 so that motor grader 100 changes its direction of travel; currently the target direction, to the corrected direction and travels along the corrected direction.

During the automated steering in this first mode, steering command signal generator 40d calculates a difference between the corrected direction obtained from direction corrector 40h and the target direction (current direction) obtained from current direction identifier 40g and then controls electrofluid pressure control valve 73 based on the calculated difference.

In the second mode, steering command signal generator 40d, based on the signal indicating the offset travel course obtained from direction corrector 40h, controls electrofluid pressure control valve 73 so that motor grader 100 travels along the offset travel course.

During the automated steering in this second mode, steering command signal generator 40d calculates a difference between the offset travel course obtained from direction corrector 40h and the preset travel course obtained from storage 40n and then controls electrofluid pressure control valve 73 based on the calculated difference.

When an operator manipulates directional correction input device 36 under automated steering in both of the first and second modes, controller 40 controls steering mechanism 66 based on an operation command inputted through directional correction input device 36 so that the direction of travel is adjusted leftward or rightward through a certain angle or the target course is offset by a certain amount. By thus controlling the steering mechanism, an operator may be allowed to make fine course adjustments of motor grader 100 under automated steering in the first or second mode.

Controller 40 may consist of different controllers; a controller C1 for control of the whole vehicular system, a controller C2 for steering stabilizer mode, and a controller C3 for auto-steering mode. Controller C1 may include lever sensor measurement value obtainer 40a, handle sensor measurement value obtainer 40b, directional signal obtainer 40c and steering command signal generator 40d. Controller C2 may include start/stoppage signal obtainer 40e, start/stoppage determiner 40f, and current direction identifier 40g. Controller C3 may include GNSS signal obtainer 40j and position/orientation obtainer 40k.

Direction corrector 40h, directional correction command obtainer 40i and storage 40n may be installed in one of controllers C1 to C3 or may be installed in any other controller(s).

Next, a work machine steering control method according to this embodiment is hereinafter described with reference to FIGS. 4 to 9. The work machine steering control method is hereinafter described in two modes; first mode (steering stabilizer mode), and second mode (auto-steering mode).

(First Mode)

The description of the steering control method starts with the first mode operation.

FIG. 5 is a flow chart of an exemplified, work machine steering control method in the first mode according an embodiment of this disclosure. FIG. 6 is a drawing that illustrates a steering control in the first mode performed in a manner that the direction of travel is maintainable. FIG. 7 is a drawing that illustrates the direction of travel being adjusted through a certain angle either rightward or leftward based on an operation command inputted through the directional correction input device.

In the description of the steering control method given below, motor grader 100 moves from a position illustrated with 100A and then sequentially to positions illustrated with 100B, 100C and 100D (hereinafter, “position 100A”, “position 100B”, “position 100C, “position 100D”), as illustrated in FIG. 6.

As illustrated in FIGS. 4 and 5, first, the first mode (steering stabilizer mode) is selected through mode selector 38. Then, the first mode is set (step S1).

When steering handle 41 or steering lever 42 is controlled by an operator in the first mode, the travel of motor grader 100 is operated manually by the operator. From position 100A to position 100B, for example, motor grader 100 travels, following the operator's manual operation. Specifically, motor grader 100 travels from position 100A to position 100B according to the manual operation of steering handle 41 or steering lever 42 by the operator.

In case the control of steering controller 67 (FIG. 3) is suspended for a predetermined period of time or automated steering is prompted to start by automatic control device 33 during the manual operation in the first mode, automated steering in the first mode is triggered and started by the event, as illustrated in FIG. 6. Position 100B may be a position at which the automated steering in the first mode starts.

As illustrated in FIGS. 4 and 5, whether the control of steering controller 67 (FIG. 3) is suspended for a predetermined period of time is determined by start/stoppage determiner 40f (step S2). Specifically, start/stoppage determiner 40f determines whether the control of steering lever 42 or steering handle 41 by an operator is suspended for a predetermined period of time based on a sensing signal transmitted from lever sensor 32 or handle sensor 31.

When start/stoppage determiner 40f determines that the control of steering controller 67 is suspended for a predetermined period of time, automated steering in the first mode starts (step S3).

In step S2, whether the start of control is requested by an operator may be determined by determining whether start/stoppage determiner 40f obtains a start signal for start of automated steering from automatic control device 33.

In this instance, automated steering in the first mode starts when start/stoppage determiner 40f determines that the start of control has been requested by the operator through automatic control device 33 (step S3).

The start of automated steering in the first mode is triggered by the output of the start signal for start of automated steering in the first mode from start/stoppage determiner 40f to current direction identifier 40g. In response to receipt of the start signal from start/stoppage determiner 40f, current direction identifier 40g identifies the current direction of motor grader 100 based on the directional signal obtained from directional signal obtainer 40c (step S4).

Current direction identifier 40g outputs a signal indicating the identified current direction to steering command signal generator 40d. Steering command signal generator 40d, based on the signal indicating the current direction obtained from current direction identifier 40g, controls electrofluid pressure control valve 73 so that motor grader 100 continues to travel along the current direction identified as its target direction. Then, steering mechanism 66 is thus controlled (step S5).

When the control of steering controller 67 by an operator is suspended for a predetermined period of time or the start of control is requested by an operator using automatic control device 33, automated steering in the first mode is thereby triggered and started.

During the automated steering in this first mode, motor grader 100 is controlled so as to keep its direction of travel (target direction), as illustrated in FIG. 6. Motor grader 100, therefore, basically moves straight forward from position 100B along the direction of travel; target direction, at the time of start of automated steering in the first mode.

A detection error(s) of direction sensor 34, for example, any drift of IMU 34a, however, may cause displacement of the course of motor grader 100 from its target direction. An operator may want to make fine adjustments of the course of motor grader 100 upon his/her preference. In this embodiment, an operator is allowed to make fine adjustments of the course of motor grader 100 under automated steering in the first mode.

As illustrated in FIG. 7, an operator, who wants to make fine adjustments of the course, manipulates directional correction input device 36. Directional correction input device 36 may be, for example, a switch to be pressed by an operator, an example of which is a push-button switch including a pair of right and left buttons 36a and 36b. When the operator presses one of right button 36a and left button 36b, a signal indicating directional correction is generated by directional correction input device 36.

As illustrated in FIGS. 4 and 5, directional correction input device 36 outputs the directional correction-indicating signal to directional correction command obtainer 40i. Directional correction command obtainer 40i determines whether an input of correction of the direction of travel has been received by determining whether the directional correction-indicating signal is obtained from directional correction input device 36 (step S6).

When directional correction command obtainer 40i determines as receiving no input of directional correction, direction corrector 40h keeps the current direction (target direction) (step S7b). In this instance, steering mechanism 66 is controlled by steering command signal generator 40d so that motor grader 100 continues to travel along the current direction (step S8).

When directional correction command obtainer 40i determines as having received an input of directional correction, direction corrector 40h calculates the corrected direction of motor grader 100 based on the directional correction-indicating signal obtained from directional correction command obtainer 40i (step S7a). Direction corrector 40h, at the time of calculating the corrected direction, may consult angle-related information stored in storage 40n. Direction corrector 40h outputs a signal indicating the corrected direction thus calculated to steering command signal generator 40d. In this instance, steering mechanism 66 is controlled by steering command signal generator 40d so that motor grader 100 starts to travel along the corrected direction (step S8).

As illustrated in FIG. 7, when the input of directional correction is received through directional correction input device 36, motor grader 100 changes its course to follow a corrected direction displaced through a predetermined angle from the direction of travel (target direction) at position 100E at which the input was received. In FIG. 7, for example, right button 36a of directional correction input device 36 is pressed, and motor grader 100 accordingly changes its course to follow a corrected direction displaced rightward from the direction of travel through a predetermined angle.

Then, whether steering controller 67 has been controlled is determined (step S9), as illustrated in FIGS. 4 and 5.

Whether steering controller 67 has been controlled (step S9) is determined by determining whether either one of steering lever 42 or steering handle 41 has been controlled by an operator. This is determined by start/stoppage determiner 40f based on the sensing signals from lever sensor 32 and handle sensor 31.

When start/stoppage determiner 40f determines that steering controller 67 has been controlled, automated steering in the first mode ends (step S10).

In step S9, whether the stoppage of automated steering has been requested may be determined when start/stoppage determiner 40f obtains a stoppage signal for stoppage of automated steering from automatic control device 33.

In this instance, automated steering in the first mode ends when start/stoppage determiner 40f determines receipt of the stoppage signal of automated steering from automatic control device 33 (step S10).

In case automated steering in the first mode ends at position 100C, motor grader 100 travels as manually operated by an operator using steering lever 42 or steering handle 41, as illustrated in FIG. 6. When automated steering in the first mode ends at position 100C, motor grader 100 starts to travel at and beyond position 100C as manually operated by an operator. Then, automated steering in the first mode may restart at and beyond position 100D.

Automated steering in the first mode allows pseud offset of the direction of travel through inputs to directional correction input device 36. This pseud offset is hereinafter described with reference to FIG. 8.

FIG. 8 is a drawing that illustrates pseud offset of a travel course during steering control in the first mode. As illustrated in FIG. 8, right button 36a of directional correction input device 36 is pressed at, for example, position 100F. Motor grader 100 accordingly changes its direction of travel rightward through a predetermined angle.

Then, left button 36b of directional correction input device 36 is pressed at, for example, position 100G. Motor grader 100 accordingly changes its direction of travel leftward through a predetermined angle. This may allow motor grader 100 to travel a course; pseud-offset result of its original travel course, at and beyond position 100G.

(Second Mode)

Next, the steering control method in the second mode operation is hereinafter described.

FIG. 9 is a flow chart of an exemplified, work machine steering control method in the second mode according an embodiment of this disclosure.

As illustrated in FIGS. 4 and 9, the second mode (auto-steering mode) is selected through mode selector 38. Then, the second mode is set (step S11).

In case the control of steering controller 67 (FIG. 3) is suspended for a predetermined period of time or automated steering is prompted to start by automatic control device 33 during manual operation in the second mode, automated steering in the second mode is triggered and started by the event.

Whether the control of steering controller 67 is suspended for a predetermined period of time is determined by start/stoppage determiner 40f (step S12). Specifically, start/stoppage determiner 40f determines whether the control of steering lever 42 or steering handle 41 by an operator is suspended for a predetermined period of time based on a sensing signal transmitted from lever sensor 32 or handle sensor 31.

When start/stoppage determiner 40f determines that the control of steering controller 67 is suspended for a predetermined period of time, automated steering in the second mode starts (step S13).

In step S12, whether the start of control is requested by an operator may be determined by determining whether start/stoppage determiner 40f obtains the start signal for start of automated steering from automatic control device 33.

In this instance, automated steering in the second mode starts when start/stoppage determiner 40f determines that the start of control has been requested by the operator through automatic control device 33.(step S13).

The start of automated steering in the second mode is triggered by the output of the start signal for start of automated steering in the second mode from start/stoppage determiner 40f to position/orientation obtainer 40k.

GNSS signal obtainer 40j obtains the position data and orientation data of motor grader 100 from GNSS receiver 35 and outputs the obtained data to position/orientation obtainer 40k. Position/orientation obtainer 40k identifies the position and orientation of motor grader 100 based on the obtained position data and orientation data of motor grader 100 (step S14). Position/orientation obtainer 40k outputs a signal indicating the identified position and orientation to steering command signal generator 40d.

During automated steering in this second mode, the steering action of motor grader 100 is automatically controlled so as to travel along a predefined travel course. Motor grader 100, therefore, basically travels along the predefined travel course.

The travel course of motor grader 100, however, may be displaced from a travel course previously set due to a possible detection error(s). An operator may want to make fine adjustments of the travel course of motor grader 100 upon his/her preference. In this embodiment, an operator is allowed to make fine adjustments of the travel course of motor grader 100 under automated steering in the second mode.

An operator manipulates directional correction input device 36 when he/she wants to make fine adjustments of the travel course under automated steering in the second mode. When the operator presses one of right button 36a and left button 36b of directional correction input device 36, a signal indicating offset of the travel course is generated by directional correction input device 36.

Directional correction input device 36 outputs an offset-indicating signal to directional correction command obtainer 40i. Directional correction command obtainer 40i determines whether an input of offset has been received by determining whether the offset-indicating signal is obtained from directional correction input device 36 (step S16).

When directional correction command obtainer 40i determines as receiving no offset input, direction corrector 40h keeps the preset travel course (target direction) (step S17b). In this instance, steering mechanism 66 is controlled by steering command signal generator 40d so that motor grader 100 continues to travel along the travel course previously set (step S18).

When directional correction command obtainer 40i determines as having received an offset input, direction corrector 40h offsets the travel course of motor grader 100 based on the offset-indicating signal obtained from directional correction command obtainer 40i (step 17a).

Direction corrector 40h, for offset of the travel course, consults information on the travel course previously set and stored in storage 40n. In response to receipt of a signal indicating that the right button was pressed through directional correction input device 36, direction corrector 40h offsets the travel course stored in storage 40n rightward relative to the direction of travel of motor grader 100. In response to receipt of a signal indicating that the left button was pressed through directional correction input device 36, direction corrector 40h offsets the travel course stored in storage 40n leftward relative to the direction of travel of motor grader 100. Direction corrector 40h outputs a signal indicating the offset travel course to steering command signal generator 40d. In this instance, steering mechanism 66 is controlled by steering command signal generator 40d so that motor grader 100 continues to travel along the offset travel course (step S18).

During the second mode selected and set, as illustrated in FIG. 8, the direction of travel of motor grader 100 is adjusted toward the right or left side through a certain angle from the pre-offset direction of travel, so that motor grader 100 starts to follow the post-offset travel course.

The steering control method according to this embodiment thereafter perform steps S9 to S10 which are similar to the steps S9 to S10 of FIG. 5. Then, automated steering in the second mode ends (step S10).

Next, operational effects exerted by this embodiment are described.

In this embodiment, the direction of travel of motor grader 100 is adjusted leftward or rightward through a certain angle based on an operation command inputted through directional correction input device 36 under automated steering in the first or second mode. In this manner, an operator is allowed to make fine adjustments of the course to be traveled by motor grader 100. Possibly, any displacement occurs in the course under automated steering due to a detection error(s) of, for example, direction sensor 34, or an operator wants to make fine adjustments of the course of motor grader 100 upon his/her preference. This embodiment, in such events, may facilitate fine adjustments of any course to be traveled by motor grader 100.

Further advantageously, no satellite positioning system is required of such fine adjustments of the direction of travel. This may allow cost reduction in the system development and production and may also eliminate the need to previously set any target course. The system may be used in environments where satellite positioning is difficult, for example, inside tunnels. Thus, fine course adjustments may be achievable inexpensively and easily.

In this embodiment, controller 40 controls steering mechanism 66 using, as the target direction, the direction of travel of motor grader 100 when automated steering starts and thereby enables automated steering in the first or second mode, as illustrated in FIGS. 4 and 6. Thus, the target direction setting may be facilitated.

In this embodiment, controller 40 starts automated steering based on that the control of steering controller 67 is suspended for a predetermined period of time, as illustrated in FIGS. 4 and 6. This may save an operator's labor of maneuvering the system to start automated steering.

In this embodiment, controller 40 starts automated steering in response to receipt of a start requesting command from the automatic control device for start of automated steering, as illustrated in FIGS. 4 and 6. Thus, automated steering may be started upon the operator's clear intension.

In this embodiment, controller 40 controls steering mechanism 66 using the satellite positioning system and thereby enables automated steering in the second mode, as illustrated in FIGS. 4 and 6. Thus, the work machine may be allowed to travel along curved courses as well as straight course under automated steering in the second mode with a higher traveling accuracy.

This embodiment provides mode selector 38 for shifting to and from the first mode and the second mode, as illustrated in FIG. 4. Through this device, an operator may be able to select and set one of the first and second modes.

In this embodiment, when the second mode is selected through mode selector 38, directional correction input device 36 functionally operates as an interface used for offset travel of motor grader 100. The offset travel is thus available through mode selector 38.

Controller 40 illustrated in FIG. 3 may be installed in work machine 100 or may be remotely installed outside of work machine 100. In case controller 40 is remotely installed outside of work machine 100, controller 40 may be wirelessly connected to sensors 31, 32, 34 and 37, GNSS receiver 35, and control devices 33, 36 and 38. The controller may be a processor or CPU, a specific example of which may be CPU (Central Processing Unit).

All of the embodiments are disclosed herein by way of illustration and example only and should not be construed as limiting by any means the scope of this disclosure. The scope of this disclosure is solely defined by the appended claims and is intended to cover the claims, equivalents, and all of possible modifications made without departing the scope of this disclosure.

REFERENCE SIGNS LIST

11: operator's cab, 11S: operator's seat, 12: work implement, 13: engine cover, 14: front frame, 15: rear frame, 16: front wheel, 17: rear wheel, 18: body frame, 21: blade, 22: drawbar, 23: swing circle, 25: lift cylinder, 28: articulate cylinder, 31: handle sensor, 32: lever sensor, 33: automatic control device, 34: direction sensor, 34a: IMU, 34b: steering angle sensor, 34c: articulate angle sensor, 34d: imaging device, 35: GNSS receiver, 36: directional correction input device, 36a: right button 36b: left button, 37: FNR/vehicle speed sensor, 38: mode selector, 40, C1, C2, C3: controller, 40a: lever sensor measurement value obtainer, 40b: handle sensor measurement value obtainer, 40c: directional signal obtainer, 40d: steering command signal generator, 40e: stoppage signal obtainer, 40f: stoppage determiner, 40g: current direction identifier, 40h: direction corrector, 40i: directional correction command obtainer, 40j: GNSS signal obtainer, 40k: position/orientation obtainer, 40n: storage, 41: steering handle, 42: steering lever, 66: steering mechanism, 67: steering controller, 71: steering pilot valve, 72: steering valve, 73: electrofluid pressure control valve, 74: steering cylinder, 100: work machine (motor grader), 121: axis

WORK MACHINE STEERING CONTROL SYSTEM AND WORK MACHINE STEERING CONTROL METHOD

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