Automatic steering system and method

• US 7,142,956 B2
• Filed: 06/24/2004
• Issued: 11/28/2006
• Est. Priority Date: 03/19/2004
• Status: Expired

• Current Assignee: Agjunction LLC (Kubota Corporation)
• Original Assignee: Hemisphere GPS LLC (Kubota Corporation)
• Inventors: McClure, John A., Collins, Dennis M., Heiniger, Richard W., Funk, Kent D., Timm, John T. E.
• Primary Examiner(s): Tran, Dalena
• Application Number:
  US10/875,776
• Publication Number:
  US 20050288834A1
• Time in Patent Office: 887 Days
• Field of Search: 701/23, 701/41, 701/50, 701/24, 701/213, 701/300, 180/9.1, 180/9.21, 180/168, 180/6.7, 180/6.2, 318/587
• US Class Current: 701/23
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: G05D 1/0278 using satellite positioning signals, e.g. GPS

Abstract

An automatic steering system and method are provided for a vehicle including an hydraulic primary steering system. The automatic steering system includes a guidance module with a GPS receiver and a microprocessor adapted to process and store GPS data defining travel paths, which can be associated with a cultivated field in an agricultural vehicle application. An automatic steering module is connected to the guidance module and to a steering valve control block, which provides pressurized hydraulic fluid in parallel with the vehicle'"'"'s primary hydrostatic steering system. The automatic steering system utilizes a constant factor, such as steering rate, for predictability and simplicity in the operation of the automatic steering system. A feedback loop from the vehicle hydrostatic steering system uses the vehicle'"'"'s actual turning rate for comparison with a desired turning rate. The system is adapted for original equipment installation and retrofitting on vehicles, such as farm tractors, with various primary hydrostatic steering system configurations. An automatic steering method includes the steps of: initializing the system; adjusting the steering with an hydraulic valve to provide a constant steering rate; providing feedback corresponding to the vehicle'"'"'s actual turning rate and combining the feedback with other input signals to provide automatic steering.

Claims

1. An automatic steering control system for a vehicle, which comprises:

a GPS receiver;

a guidance controller connected to the GPS receiver;

a vehicle steering system including a steering actuator and a steering power source connected to the steering actuator;

a steering input device connected to the steering power source and the steering actuator;

the guidance controller being operably connected to the steering input device;

a loop for feeding back an operating parameter to the guidance controller, said operating parameter corresponding to a GPS-derived actual turning rate for comparison to a desired turning rate and automatic correction to a desired guide pat initiated automatically by said guidance controller in response to a discrepancy between said desired turning rate and said actual turning rate determined utilizing GPS-derived vehicle position, around speed, steering rate and course information item said GPS receiver and said guidance controller, and

said correction to said desired guide path occurring automatically in response to said actual turning rate parameter based on GPS-derived vehicle position, ground speed, steering rate and course information without operator intervention.

2. The system according to claim 1, which includes:

said steering actuator and said power source being hydraulic;

said steering input device including an hydraulic steering valve control and providing a constant steering factor; and

said guidance controller providing a steering input signal to said steering input device from among an input signal set including signals corresponding to left and right turns.

3. The system according to claim 2, which includes:

said constant steering factor comprising a constant steering rate;

said feedback loop providing to said guidance controller a feedback signal corresponding to a vehicle actual turning rate; and

said actual turning rate comprising a function of factors including vehicle ground speed and steering rate.

4. The system according to claim 3, which includes:

said vehicle steering actuator providing said feedback signal; and

an inertial based yaw rate gyro sensor in said feedback loop.

5. The system according to claim 4, which includes:

a proportional integral derivative (PID) compensator with an input connected to said guidance controller and an output;

adjustable gain inputs to said PID compensator corresponding to a computed error, an integral of said error and a time derivative of said error corresponding to an error rate; and

a deadband filter with an input connected to said PID compensator output and a deadband filter output connected to said hydraulic steering valve control.

6. The system according to claim 5, which includes:

said guidance controller including a path planner;

a position/speed signal output from said GPS receiver and input to said guidance controller;

a yaw rate filter including a first input connected to and receiving a differential heading signal from said GPS receiver and an output connected to and providing a smooth heading signal to said guidance controller; and

said yaw rate filter including a second input connected to said yaw rate gyro and receiving a signal corresponding to the gyroscopically-corrected actual turning rate.

7. The system according to claim 6, which includes:

a low pass noise filter wit an adjustable time constant, an input connected to said yaw rate gyro output and receiving a corrected actual turning rate signal therefrom, and an output representing an observed turning rate;

a summer with an observed turning rate input connected to said noise filter output and a desired turning rate input connected to said guidance controller and adapted to receive a desired turning rate signal therefrom; and

said summer providing an output signal corresponding to a differential between said desired and observed turning rate signals to said PID compensator.

8. The system according to claim 2, which includes:

said steering actuator comprising an hydraulic piston-and-cylinder steering unit connected to said vehicle steering;

said steering input device including a steering valve control block with left and right solenoid-actuated steering valves each having an hydraulic output connected to said steering unit, an hydraulic input and an electrical input connected to said guidance controller and receiving an on-off input signal therefrom whereby each said valve is selectively movable between respective on and off positions; and

said steering valve control block including a steering rate control comprising an adjustable hydraulic flow valve with an input connected to said hydraulic power source and an output connected to said steering valve hydraulic inputs.

9. The system according to claim 8, which includes:

said adjustable hydraulic flow valve comprising a needle valve with a user-accessible steering control rate adjustment knob and variable settings corresponding to a vehicle steering aggressiveness factor;

said vehicle including an existing hydrostatic steering system; and

said steering valve control block including said solenoid steering valves end said needle valve, said steering valve control block being adapted for connection in parallel with the existing hydrostatic steering system.

10. The system according to claim 8, which includes:

said steering input device including an adjustable flow, pressure compensating hydraulic valve;

a directional control; and

a steering cylinder displacement sensor;

a desired flow rate and an hydraulic system disturbance inputs to said pressure compensating hydraulic valve, which includes an output corresponding to an actual flow rate;

said actual flow rate and a left/right/none steering signal comprising inputs to said directional control, which provides an output with a corresponding cylinder flow rate;

said steering cylinder displacement sensor providing an output corresponding to a steering angle; and

an actual turning rate for said vehicle comprising a function of said steering angle, a ground speed of said vehicle and an external disturbance factor.

11. The system according to claim 2 wherein said vehicle is a track vehicle with differential steering including a track drive pump and said steering input device includes:

a desired pressure associated with said hydraulic system;

a directional control receiving an actual pressure as an input and providing an output differential pressure to said track drive pump;

a gain value G associated with the differential steering and comprising a ratio of differential RPM to signal (pressure); and

the actual turning rate being a function of the differential steering gain value G, the vehicle ground speed and an external disturbance factor.

12. The system according to claim 2 wherein said guidance controller includes a mapping module, which module includes:

a memory adapted to receive and store data corresponding to the area covered by said vehicle;

a visual display of said covered area; and

an area calculation function adapted for calculating the area covered based on the GPS coordinates of the area perimeter.

13. The system according to claim 2, which includes:

said vehicle including a motive component with an hydraulic system, a working component and an articulated, hydraulically-actuated hitch interconnecting said motive and working components;

said hitch having left end right lateral displacement positions adapted for respectively displacing said working component left and right of said motive component path to compensate for motive component crosstrack deviations from a predetermined desired guide path of said working component;

a hitch control module including an input connected to said guidance controller and adapted to receive hitch displacement signals therefrom; and

said hitch control module including an output connected to said articulated hitch and adapted for causing said articulated hitch to move between its lateral displacement positions.

14. The system according to claim 13, which includes:

a working component GPS receiver and guidance controller mounted on said working component; and

said working component guidance controller including an output for signals corresponding to GPS positions of said working component;

said motive component guidance controller including en input for said working component GPS position signals; and

said motive component guidance controller displacing said articulated hitch in response to said GPS position signals from said working component to compensate for course deviations of said motive component.

15. The system according to claim 2 wherein said guidance controller includes an auto-disengage feature activated by one or more of the disengage conditions from the set consisting of:

excessive current position error;

vehicle speed too slow;

vehicle speed too fast;

excessive turning rate;

manual steering by operator; and

operator absent.

16. The system according to claim 15 wherein said guidance controller includes an auto-engage feature activated by said vehicle being in proximity to a guide path within a predetermined period of time after auto-disengagement.

17. The system according to claim 1, which includes:

a primary vehicle steering system including said steering actuator and said steering power source;

an auxiliary steering system including said steering input device;

said auxiliary steering system being connected in parallel with the primary steering system to the steering power source and the steering actuator in parallel with said primary vehicle steering system; and

said primary steering system including a primary steering device.

18. The system according to claim 17 wherein said vehicle includes a hydrostatic steering system comprising one type from among the group consisting of:

closed-center, load-sensing, non-reactive;

closed-center, pressure-compensating, non-reactive;

open-center, non-reactive;

reactive; and

dual-path, differential track drive.

19. The system according to claim 1, which includes:

a straight-line (A–

B) operating mode;

a contour operating mode for guidance along curved lines;

said guidance controller having a memory adapted for storing multiple straight-line and contour guide paths;

said guidance controller automatically steering said vehicle along straight and curved guide paths in said straight-line and contour operating nodes respectively; and

said guidance controller including a switching function adapted for switching between said straight-line and contour operating modes while said automatic steering system is automatically steering said vehicle.

20. An automatic steering control system for an agricultural vehicle, which system comprises:

a GPS receiver;

a guidance controller connected to the GPS receiver;

a primary vehicle hydrostatic steering system including an hydraulic steering actuator, an hydraulic power source connected to the steering actuator and a primary steering input device directing hydraulic power from said power source to said steering actuator;

an auxiliary steering input device connected to said guidance controller, said steering power source and said steering actuator, said auxiliary steering input device including an hydraulic steering valve control and providing a constant steering rate;

said guidance controller providing a steering input signal to said auxiliary steering input device from among the input signal set consisting of left, right and none;

a feedback loop from the vehicle steering system to the guidance controller;

an inertial based yaw rate gyro sensor in said feedback loop correcting said feedback signal by smoothing the effects of course deviations associated with vehicle yaw;

a proportional integral derivative (PID) compensator with an input connected to said guidance controller and an output;

adjustable gain inputs to said PID compensator corresponding to a computed error, an integral of said error and a time derivative of said error corresponding to an error rate;

said guidance controller including a path planner;

a position/speed signal output from said GPS receiver and input to said guidance controller;

a yaw rate filter including a first input connected to and receiving a differential heading signal from said GPS receiver and an output connected to and providing a smooth heading signal to said guidance controller;

said yaw rate filter including a second input connected to said yaw rate gyro sensor and receiving a signal corresponding to the gyroscopically-corrected actual turning rate;

a low pass noise filter with an adjustable time constant and including an input connected to said yaw rate gyro sensor output and receiving a corrected actual turning rate signal therefrom and an output providing an observed turning rate output signal;

a summer with an observed turning rate input connected to said noise filter output and a desired turning rate input connected to said guidance controller and adapted to receive a desired turning rate signal therefrom;

said summer providing an output signal corresponding to a differential between said desired and observed turning rate signals to said PID compensator;

said steering actuator comprising an hydraulic piston-and-cylinder steering unit connected to said vehicle steering;

said steering input device including a steering valve control block with left and right solenoid-actuated steering valves each having an hydraulic output connected to said steering unit, an hydraulic input and an electrical input connected to said guidance controller and receiving an on-off input signal therefrom whereby each said valve is selectively movable between respective on and off positions;

said steering valve control block including a steering rate control comprising an adjustable hydraulic flow valve with an input connected to said hydraulic power source and an output connected to said steering valve hydraulic inputs;

a straight-line (A–

B) operating mode;

a contour operating mode for guidance along curved lines;

said guidance controller having a memory adapted for storing multiple straight-line and contour guide paths;

said guidance controller automatically steering said vehicle along straight and contour guide paths in said straight-line and contour operating modes respectively;

said guidance controller including a switching function adapted for switching between said straight-line and contour operating modes while said automatic steering system is automatically steering said vehicle; and

said guidance controller including an auto-disengage feature activated by one or more predetermined auto-disengage conditions and an auto-engage feature activated by one or more predetermined auto-engage conditions.

21. An automatic steering method for a vehicle, which comprises the steps of:

defining a guide pat pattern wit GPS locations;

storing said guide path pattern electronically in a guidance controller computer memory;

defining a desired turning rate;

storing said desired turning rate in said guidance controller computer memory;

operating said vehicle in proximity to said guide path pattern

receiving GPS signals corresponding to current vehicle locations;

comparing said stored guide path GPS locations with current GPS locations;

steering said vehicle to said guide path;

deriving with GPS a vehicle operating parameter comprising an actual turning rate for said vehicle utilizing GPS-derived vehicle position, ground speed, steering rate and course information from said GPS receiver and guidance controller;

providing a feedback signal corresponding to said actual turning rate vehicle operating parameter to said guidance controller;

comparing said desired turning rate to said actual turning rate; and

automatically without operator intervention correcting the course of said vehicle to said guide pat pattern in response to said feedback signal indicating a discrepancy between said desired turning rate by said guidance controller in response to said actual turning rate parameter based on GPS-derived vehicle position, ground speed, steering rate and course information.

22. The method according to claim 21, which includes the additional steps of:

providing said vehicle with a hydrostatic steering system;

using a constant steering rate as a factor in calculating steering corrections for said vehicle; and

adjusting an hydraulic flow in said steering system to establish said constant steering rate.

23. The method according to claim 22, which includes the additional steps of:

providing a steering valve control block with an hydraulic control valve for adjusting said hydraulic flow in said steering system;

providing said steering valve control block with first and second solenoid-activated hydraulic valves; and

activating said hydraulic valves with left and right turn commands from said guidance controller.

24. The method according to claim 23, which includes the additional steps of:

providing an inertial yaw rate gyro sensor in said feedback loop; and

providing a feedback signal corresponding to vehicle yaw from said gyro sensor to said guidance controller.

25. The method according to claim 23, which includes the additional steps of:

providing a proportional integral derivative (PID) compensator and connecting an input of same to en output of said guidance controller;

modifying a guidance signal from said guidance controller with said proportional integral derivative compensator and providing said modified guidance signal as an output therefrom;

providing a deadband filter between said proportional integral derivative compensator and said steering valve control block; and

providing a steering command from said deadband filter from among the set consisting of left, right and none.

26. The method according to claim 22, which includes the additional steps of:

providing en auxiliary steering system in parallel with said vehicle primary hydrostatic steering system; and

assisting the operation of said vehicle primary steering system with said auxiliary steering system.

27. The method according to claim 26, which includes the additional step of automatically disengaging said auxiliary steering system in response to a predetermined condition from among the set consisting of:

excessive current position error;

vehicle speed too slow;

vehicle speed too fast;

excessive turning rate;

operator manually steering; and

operator absent.

28. The method according to claim 26, which includes the additional step of automatically reengaging said auxiliary steering system in response to said vehicle being in proximity to said course within a predetermined auto-engage period.

29. The method according to claim 22, which includes the additional steps of:

calibrating said steering rate factor by manually adjusting said hydraulic flow control valve and timing the operation of said steering actuator;

providing a deadband filter between said guidance controller and said valve control block; and

adjusting the sensitivity of said system by calibrating said deadband filter.

30. The method according to claim 21, which includes the additional steps of:

providing a feedback signal corresponding to an actual turning rate of said vehicle as a function of a steering command, a steering speed and external disturbances;

feeding back said actual turning rate to said guidance controller; and

comparing said actual turning rate wit said desired turning rate and deriving a steering command from said comparison.

31. The method according to claim 21, which includes the additional steps of:

providing a mapping module and connecting same to said guidance controller;

displaying an area covered by said system on said mapping module; and

calculating a coverage area from a perimeter thereof defined by GPS locations.

32. The method according to claim 21, which includes the additional steps of:

providing motive and working components;

hitching said motive component to said working component with an articulated hitch; and

laterally, automatically shifting the working component wit respect to the motive component in response to working component deviation from a predetermined GPS guide path.

33. The method according to claim 21, which includes the additional steps of:

installing said auxiliary steering system in a vehicle wit a reactive primary steering system; and

installing a reactive steering isolation circuit in said primary steering system.