Method and apparatus for controlling a work implement

• US 6,140,787 A
• Filed: 03/23/1999
• Issued: 10/31/2000
• Est. Priority Date: 07/23/1997
• Status: Expired due to Fees

• Current Assignee: Horton Trading Ltd.
• Original Assignee: RSI Video Technologies Incorporated (Resideo Technologies, Inc.)
• Inventors: Fedoruk, James David, Lokhorst, David M., Halwas, Angela R.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US09/274,864
• Time in Patent Office: 588 Days
• Field of Search: 318/567, 318/568.1, 318/568.11, 318/568.16, 318/568.17, 318/568.18, 318/568.2, 318/590, 701/50, 74/471 R, 74/471 XY, 414/685, 414/697, 414/699
• US Class Current: 318/568.18
• CPC Class Codes: E02F 3/435 for dipper-arms, backhoes or the like
• CPC Class Codes: E02F 3/437 providing automatic sequences of movements, e.g. linear excavation, keeping dipper angle constant
• CPC Class Codes: E02F 9/2012 Setting the functions of the control levers, e.g. changing assigned functions among operations levers, setting functions dependent on the operator or seat orientation
• CPC Class Codes: E02F 9/2203 Arrangements for controlling the attitude of actuators, e.g. speed, floating function
• CPC Class Codes: E02F 9/26 Indicating devices E02F5/145 takes precedence
• CPC Class Codes: Y10T 74/20201 Control moves in two planes

Abstract

A controller for a work implement, such as the arm of a backhoe, a feller buncher, an excavator or the like provides a number of advantages over previous controllers and control methods. The controller responds to an operator'"'"'s inputs to a joystick control such that the work implement moves parallel to the direction in which the joystick is deflected at a speed which is proportional to the amount of deflection of the joystick. The controller used the joystick position to generate a path and attempts to cause the work implement to move along the path. The controller computes a maximum available speed in the direction of motion specified by the joystick and is self calibrated so that full deflection of the joystick selects the maximum available speed. The controller has a self calibration mode which compensates for variability in the motion produced by the various actuators in response to given control signals. In a hydraulically operated machine the self calibration feature involves measuring actual fluid flow rates by measuring changes in the position of actuators and comparing the measured and actual flow rates to yield an error sample. The controller allows the maximum speeds of various parts of a controlled machine to be limited.

Claims

1. A method for controlling a work implement (41) the method including

a) receiving an input signal (j) from a control (70),

b) computing a desired trajectory from the input signal, by repeatedly:

i) determining an actual position (p_act) of the work implement;

ii) from the actual position computing a path point (p_path) which is on, but not at an end of, a previously computed portion of the trajectory; and

,

iii) adding a continuation of the trajectory to the path point; and

,

c) controlling the work implement to move along the trajectory.

2. The method of claim 1 wherein the path point is a point on the previously computed trajectory nearest to the actual position.

3. The method of claim 2 wherein the work implement comprises an articulated arm (41) comprising a boom (40) having a first end pivotally mounted to a machine by a first pivotal coupling (42) and a second end coupled to a stick (48) by a second pivotal coupling (52) and the step of determining the actual position comprises measuring an angular position of each of the first and second couplings and computing the actual position by the forward kinematics for the articulated arm.

4. The method of claim 1 wherein the continuation of the trajectory comprises a vector (δ

p) having a length proportional to the magnitude of the control signal (j).

5. The method of claim 4 wherein the vector (δ

p) has a length proportional to a maximum velocity of the work implement.

6. The method of claim 5 including computing the maximum velocity (ν

_max) from a measured actual position of the work implement (41).

7. A method for controlling a work implement, the method comprising:

a) providing a control member accessible to an operator of the work implement, the control member controllably displaceable by an operator from a neutral position to produce control signals indicating a first direction and a first magnitude;

b) displacing the control member from the neutral position;

c) providing the control signals to an input of a controller,

d) providing to the controller one or more transducer signals identifying a current configuration of the work implement;

e) in the controller;

i) computing a desired path for the work implement, the desired path comprising a sequence of desired positions by;

A) periodically sampling the control signal and the transducer signal;

B) for each sample computing a desired direction and a desired velocity of the work implement from the control signal; and

,

C) for each sample extending the desired path by computing a new desired position, the new desired position obtained by determining on the desired path a path point which is closest to an actual position of the work implement and adding a vector to the path point, the vector having the desired direction and a length proportional to the desired velocity; and

,

ii) generating controller output signals at a processor output to operate actuators so as to move the work implement in a direction from the actual position to the new desired position with a velocity proportional to the distance between the actual position and the new desired position; and

,

f) applying the controller output signals to actuators on the work implement to actuate the actuators to move the work implement.

8. A method for controlling a work implement, the method comprising:

a) providing a control member (71) accessible to an operator of the work implement (41), the control member controllably displaceable by an operator from a neutral position (73);

b) displacing the control member (71) from the neutral position (73) in a first direction relative to a reference axis (75) through a distance equal to a first fraction of a distance between the neutral position and a maximum displacement of the control member (71) in the first direction;

c) providing an output signal (j) representing the displacement of the control member (71) at an input of a controller (80), the output signal identifying at least the first direction and the first fraction;

d) providing to the controller (80) one or more transducer output signals (θ

_act) identifying a current configuration of the work implement;

e) in the controller,

i) computing a maximum velocity (ν

_max) of the work implement (41) in a desired direction of motion corresponding to the first direction;

ii) computing a desired velocity of the work implement, the desired velocity proportional to the first fraction multiplied by the maximum velocity; and

,

iii) generating controller output signals at a processor output corresponding to the desired direction and the desired velocity, and,

f) applying the controller output signals to actuators on the work implement (41) to cause the actuators to move the work implement in the desired direction at the desired velocity.

9. The method of claim 8 wherein the desired direction is generally parallel to the first direction.

10. The method of claim 8 wherein the control member comprises a handle (71) of a joystick (70), the handle displaceable in "X" "Y" and "Z" directions in a Cartesian coordinate system having an origin at neutral position (73).

11. The method of claim 10 wherein the work implement comprises an articulated arm (41) having a plurality of pivoting joints (42, 52, 58) wherein an endpoint of the arm (41) may be moved in a plane parallel to an X-Z plane of the Cartesian coordinate system.

12. A method for tuning the performance of a control system for a hydraulically operated work implement (41), the implement comprising one or more actuators (44,50,60) and one or more controlled valves (81) associated with each actuator, the method comprising repeatedly in subsequent periods (Δ

t) generating control signals to open one or more of the valves (81) by amounts computed to achieve a desired flow rate in each valve, the method characterized by;

a) measuring an actual flow rate at each valve during a period (Δ

t);

b) for each valve, comparing the actual flow rate to the desired flow rate for the period to yield an error value;

c) using the error values to correct the calculation of control signals in subsequent periods (Δ

t).

13. The method of claim 12 wherein measuring the actual flow rate in each valve comprises monitoring a signal from a position transducer coupled to the actuator associated with that valve and computing a flow rate at the valve from a change in the output signal.

14. The method of claim 12 wherein generating the control signals comprises, for each valve, maintaining a look up table (92), the look up table comprising a plurality of data values for the valve, the data values relating a magnitude of the control signal for the valve to flow in the valve and using the look up table to provide a control signal magnitude corresponding to a desired flow rate.

15. The method of claim 14 wherein using the look up table (92) to provide a control signal magnitude comprises interpolating between data values corresponding to flow rates near the desired flow rate.

16. The method of claim 15 comprising separately accumulating error values in each of a plurality of ranges of flow rates, each range of flow rates including a flow rate corresponding to at least one data value.

17. The method of claim 16 wherein using the error values comprises calculating an average error value for each range and updating the at least one data value in the range by subtracting all or a fraction of the calculated error value from the at least one data value in the range.

18. The method of claim 17 comprising accumulating at least a threshold number of error values in a range before updating the at least one data value.

19. The method of claim 18 comprising grouping two or more of the ranges into a group and accumulating at least a threshold number of error values in each range in the group before updating the at least one data value in each range of the group.

20. The method of claim 14 wherein error values are derived by subtracting from the control signal magnitude a correct control signal magnitude obtained by using the look up table (92) to determine a corresponding to the measured flow rate.

21. The method of claim 20 including monitoring the transducer signal and discarding error values whenever the transducer signal indicates that the actuator is near an end of its range of motion.

22. The method of claim 21 including discarding error values whenever the actual flow is opposite in direction to the desired flow.

23. A control system for a work implement comprising an articulated arm (41) the system comprising:

a) a control member accessible to an operator of the work implement (41), the control member controllably displaceable by an operator from a neutral position (73) in a desired direction through a desired fraction of a maximum displacement distance to produce a control signal (j);

b) two or more angular position transducers, one of the transducers coupled to each of two or more pivoting joints on the articulated arm, the transducers producing transducer signals representing a current configuration of the articulated arm;

c) a controller connected to receive the control signals and the transducer signals, the controller comprising;

i) means (1310) for computing a desired velocity from the control signal;

ii) vector computation means (1314) for computing from the desired velocity a vector (δ

p) to be added to a previously computed trajectory;

iii) path point computation means (1316,

     1318) for computing from the transducer signal a path point (p_path) on the previously computed trajectory closest to an actual position of the arm (41);

iv) vector addition means for extending the previously computed trajectory by adding the vector (δ

p) to the path point (p_path); and

,

v) control means for operating actuators (44,50,60) associated with the joints (42,52,58) to move an endpoint (65) of the arm along the extended trajectory.

24. The control system of claim 23 wherein the path point computation means comprises forward kinematic computation means (1318) for computing a signal (p_act) representing an actual position of a reference point (65) on arm (41).

25. The control system of claim 23 wherein the means (1310) for computing a desired velocity from the control signal computes a maximum available velocity (ν

_max) in the desired direction from the transducer signals.

26. A control system for a work implement comprising two or more movable coupled members (40,48,56) and a number of actuators (44,50,60) for moving the coupled members relative to one another, the control system comprising:

a) one or more operator controls collectively having at least two degrees of freedom, the controls manipulable by an operator of a work implement to produce first and second output signals indicating a degree of displacement of the controls from a neutral position toward a maximum displacement;

b) one or more transducers coupled to the work implement, the transducers producing transducer output signals representing relative positions of the coupled members;

c) a processor connected to receive the first and second output signals and the transducer output signal, the processor having an output and adapted to;

i) compute a desired direction of motion from the first and second output signals;

ii) compute a maximum velocity of the work implement in the desired direction of motion from the transducer output signals; and

,

iii) generate controller output signals at the processor output to actuate the actuators to move the work implement in the desired direction at a calculated velocity wherein the ratio of the calculated velocity to the maximum velocity is generally proportional to a ratio between the displacement of the controls to the maximum displacement;

wherein the processor output is coupled to apply the controller output signals to the actuators (44,50,60).

27. A controller for a work implement, the controller comprising:

a) a set of one or more control inputs for receiving a control signal from one or more operator controls, the control signal representing;

b) a set of one or more transducer inputs for receiving transducer signals representing a current configuration of a work implement;

c) a processor connected to the control inputs and the transducer inputs, the processor having one or more controller outputs, the processor adapted to

i) compute a desired direction of motion from the control signal;

ii) compute a maximum speed of the work implement in the desired direction of motion from the transducer output signals; and

,

iii) generate controller output signals at the processor output to actuate the actuators to move the work implement in the desired direction at a calculated speed wherein the ratio of the calculated speed to the maximum speed is proportional to the ratio between the displacement of the controls to the maximum displacement.