Information
-
Patent Grant
-
6374153
-
Patent Number
6,374,153
-
Date Filed
Wednesday, March 31, 199925 years ago
-
Date Issued
Tuesday, April 16, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Grant; William
- Bahta; Kidest
Agents
-
CPC
-
US Classifications
Field of Search
US
- 700 69
- 700 71
- 700 58
- 700 245
- 700 188
- 701 50
- 701 26
- 414 700
- 414 713
- 414 699
-
International Classifications
-
-
Disclaimer
Terminal disclaimer
Abstract
An apparatus and method for providing coordinated control of a work implement of a work machine. The implement includes a boom having a first end portion and a second end portion, with the first end portion pivotally connected to the frame and the second end portion pivotally connected to a load-engaging member. The apparatus includes a position sensor adapted for providing a position signal, and an input device adapted for delivering a desired velocity signal indicative of the desired velocity of the load-engaging member. The desired velocity includes a desired angular velocity and a desired linear velocity. The apparatus receives the position signal and the desired velocity signal, and determines an actual path of travel of the load-engaging member, and a desired path of travel of the load-engaging member. The apparatus further modifies the desired angular velocity and the desired linear velocity in response to a deviation between the actual and desired paths of travel.
Description
TECHNICAL FIELD
This invention relates generally to an apparatus and method for controlling a work implement of a work machine and, more particularly, to an apparatus and method for providing coordinated control of the work implement to produce linear movement of the work implement.
BACKGROUND ART
Work machines, such excavators, backhoe loaders, wheel loaders, telescopic material handlers, and the like, are adapted for digging, loading, pallet-lifting, etc. These operations usually require the use of two or more manually-operated control levers for controlling the position and orientation of the work implement.
As an example, a telescopic material handler includes a telescoping boom having a load-engaging member, e.g., pallet lifting forks, connected at one end of the boom. Two control levers are used to independently actuate hydraulic cylinders adapted for controlling the angle of the boom with respect to a reference plane, and the length of the boom, respectively.
Frequently, linear or straight-line movement of the forks are required, e.g., when the forks of the telescopic material handler are to be driven under a pallet in order to lift the pallet. In order to effect such linear movement, the angle of the boom and the length of the boom must be simultaneously controlled. Extensive operator skill is required for coordinating control of the levers while performing these complex operations, thus increasing operator fatigue for skilled operators, and the training time required for lesser skilled operators.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, an apparatus for providing coordinated control of an implement of a work machine having a frame, the implement includes a boom having a first end portion and a second end portion, with the first end portion pivotally connected to the frame and the second end portion connected to a load-engaging member. The apparatus includes a position sensor adapted for providing a position signal, and an input device adapted for delivering a desired velocity signal indicative of the desired velocity of the load-engaging member. The desired velocity includes a desired angular velocity and a desired linear velocity. The apparatus receives the position signal and the desired velocity signal, and determines an actual path of travel of the load-engaging member, and a desired path of travel of the load-engaging member. The apparatus further modifies the desired angular velocity and the desired linear velocity in response to a deviation between the actual and desired paths of travel.
In another aspect of the present invention, a method for providing coordinated control of an implement of a work machine having a frame is disclosed. The implement includes a boom having a first end portion and a second end portion, with the first end portion pivotally connected to the frame and the second end portion connected to a load-engaging member. The method includes the step of sensing a position of the load-engaging member, and responsively delivering a position signal. The method also includes the steps of delivering a desired velocity signal indicative of a desired velocity of the load-engaging member, the desired velocity including a desired angular velocity and a desired linear velocity. The method further includes the steps of determining an actual path of travel of the load-engaging member as a function of the position signal, determining a desired path of travel of the load-engaging member as a function of the desired velocity signal, and modifying the desired angular velocity and the desired linear velocity in response to a deviation between the actual and desired paths of travel.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a diagrammatic illustration of a work machine suitable for use with an embodiment of the present invention;
FIG. 2
is a block diagram illustrating an embodiment of the present invention;
FIG. 3
is a block diagram illustrating an embodiment of a control system of the present invention;
FIG. 4
illustrates examples of a plurality of velocity ratio vectors associated with an embodiment of the present invention; and
FIG. 5
is a flow diagram illustrating an embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
With reference to
FIGS. 1-5
, the present invention provides an apparatus and method for providing coordinated control of a work implement
160
of a work machine
100
. For purposes of discussion, the following description will be directed to a telescopic material handler
100
. However, it is to be realized that any number of other types of work machines, such as backhoe loaders, wheel loaders, excavators, and the like, may be substituted without departing from the spirit of the invention.
With particular reference to
FIG. 1
, an illustration of a telescopic material handler
100
is shown. The telescopic material handler
100
includes a machine frame
130
which can be driven on wheels
120
a,
120
b
or other ground-engaging supports, such as tracks. The telescopic material handler
100
further includes a boom
160
having a first end portion
162
and a second end portion
164
. The boom
160
is pivotally connected to the frame
130
at the first end portion
162
of the boom
160
.
The boom
160
includes a telescopic member
170
movable between a fully retracted length and a fully extended length. A load-engaging member
180
is pivotally connected to the telescopic member
170
at the second end portion
164
of the boom
160
. In the preferred embodiment, the load-engaging member
180
includes a fork
180
. However, other kinds and types of load-engaging members
180
may be used, such as a bucket or other material handling device, without deviating from the scope of the invention.
The angle of the boom
160
with respect to the frame
130
is controlled by a first actuator
140
connected between the frame
130
and the boom
160
. The extension and retraction of the telescopic member
170
is controlled by a second actuator
150
connected between the boom
160
and the telescopic member
170
. Preferably, the first and second actuators
140
,
150
include a fluid-operated cylinder, for example a hydraulic cylinder.
For illustrative purposes, only two actuators
140
,
150
are shown. However, it is to be understood, that any number of actuators may be used in the present invention as desired. For example, a third actuator may be provided for maintaining the attitude of the fork
180
in a level condition.
With reference to
FIG. 2
, the first and second actuators
140
,
150
are controlled in accordance with input commands provided by an input device
270
located on the work machine
100
. The input device
270
operates hydraulic valves (not shown) that control the delivery of pressurized fluid to the first and second actuators
140
,
150
.
In the preferred embodiment, the input device
270
includes a joystick. However, other types of input devices
270
, such as hand-operated control levers, foot pedals, a keypad, and the like, may be substituted without departing from the scope of the invention.
The operator-controlled joystick
270
delivers a desired velocity signal to a control system
240
located on the work machine
100
, in response to movement of the joystick
270
along predefined axes. In the preferred embodiment, the joystick
270
has two degrees of movement. Left and right movement of the joystick
270
along a first axis (x axis) provides linear horizontal motion of the load-engaging member
180
at the pivoted connection
164
. Likewise, forward and backward movement of the joystick
270
along a second axis (y axis) perpendicular to the first axis, provides linear vertical motion of the load-engaging member
180
at the pivoted connection
164
.
The control system
240
also receives position signals indicative of the position of the load-engaging member
180
from a position sensor
210
located on the work machine
100
. The position sensor
210
includes an angle sensor
220
adapted for sensing the angle of the boom
160
relative to the frame
130
, and responsively delivering a boom angle signal. The position sensor
210
also includes a length sensor
230
adapted for sensing the length or extension of the telescopic member
170
of the boom
160
, and responsively delivering a boom length signal. The position sensor
210
further includes an inclination sensor
280
adapted for sensing an angle of inclination of the frame
130
relative to a reference plane
110
, and responsively delivering an inclination signal. The specific operation of the control system
240
will be discussed in more detail below.
It can be appreciated by those skilled in the art that other types of sensors and combinations thereof may be included in the position sensor
210
without deviating from the present invention. As an example, a fork sensor may be included for sensing the inclination or attitude of the fork
180
, relative to the telescopic member
170
, and responsively delivering a fork position signal.
In the preferred embodiment, the control system
240
includes a processor
250
, and both read only and random access memory. The processor
250
receives and processes inputs from the boom angle signal, the boom length signal, and the inclination signal, as well as the desired velocity signal provided by the input device
270
. Through execution of control routines, such as software programs stored in memory, the processor
250
generates and delivers a command signal to a controller
260
. The controller
260
automatically coordinates the flow of hydraulic fluid to both the first and second actuators
140
,
150
, in response to the command signal.
Although the input device
270
and control system
240
have been described as being located on the work machine
100
and electrically connected together, one or both elements may be stationed remotely from the work machine
100
. For example, the control system
240
may be located at a central site office, and adapted to communicate with the position sensor
210
, the input device
270
, the first actuator
140
, and the second actuator
150
through a wireless communication link.
Referring now to
FIG. 3
, a block diagram of the control system
240
is shown. The input commands, which are generated by the input device
270
, are shown as desired velocity requests. The input commands are in Cartesian coordinates, and represent the desired x and y velocity of the boom
160
corresponding to the desired speed and direction of movement of the fork
180
.
Based on the inclination of the machine
100
relative to the reference plane
110
, the desired velocity is transformed or adjusted at control box
310
.
An actual position of the load-engaging member
180
is determined at control box
320
as a function of the boom angle signal, the boom length signal, and the inclination signal.
The actual position of the load-engaging member
180
is transformed at control box
330
into an actual angular velocity and an actual linear velocity. More specifically, the actual angular velocity is determined by computing the derivative of the boom angle signals, as sensed by the angle sensor
220
. Similarly, the actual linear velocity is determined by computing the derivative of the boom length signals, as sensed by the length sensor
230
.
The adjusted desired velocity requests are transformed at control box
340
into a desired path of travel of the load-engaging member
180
, and the actual angular velocity and the actual linear velocity are transformed at control box
350
into an actual path of travel of the load-engaging member
180
.
The deviation between the actual and desired paths of travel, and the difference between the actual and desired velocities are computed at control box
360
, and a compensating error is generated.
The compensating error is used to modify the adjusted desired velocity requests at control box
360
.
The desired velocity requests, represented in Cartesian coordinates, are transformed at control box
370
into corresponding polar coordinates based on the position and orientation of the boom
160
. The output of the Cartesian to polar transform control box
370
is the desired angular velocity of the boom
160
, which is controlled by the first actuator
140
, and the desired linear velocity of the boom
160
, which is controlled by the second actuator
150
.
The desired velocity commands are transformed into a desired velocity ratio at control box
375
, and the actual velocity commands are transformed into an actual velocity ratio at control box
380
. More specifically, the actual and desired velocity ratios, represented as percentages, are calculated in accordance with the following equations:
It is to be understood that the units for angular velocity and linear velocity in the above equation have been adjusted in order to provide common units.
Together, the combined angular velocity ratio and linear velocity ratio represent a velocity ratio vector
400
.
FIG. 4
shows examples of a plurality velocity ratio vectors
400
.
Preferably, the desired and actual velocity ratios represent the desired and actual velocities of the first actuator
140
, relative to the desired and actual velocities of the second actuator
150
.
The desired velocity ratio vector is compared to the actual velocity ratio vector at control box
385
, and an error is generated. This error value is used to modify the desired velocity ratio vector, i.e., the desired angular velocity ratio and the desired linear velocity ratio.
As an example, a desired angular velocity ratio of 60% and a desired linear velocity ratio of 40% is requested by the input device
270
. However, the actual angular velocity ratio is 65%, while the actual linear velocity ratio is 35%. Thus, the error is 5%. Therefore, the desired angular velocity ratio is decreased by 5% and the desired linear velocity ratio is increased by 5%, resulting in a desired angular velocity ratio of 55% and a desired linear velocity ratio of 45%.
The desired angular velocity and the desired linear velocity ratios are converted to desired flows to the respective actuators in a velocity to flow transform control box
390
. Preferably, a look-up table or map is used to convert the desired velocity ratio values to desired flows to the first and second actuators
140
,
150
.
The desired flows are scaled in control box
395
by a gain factor, K, and mapped to current values for output to the first and second actuators
140
,
150
by a flow to current map
396
. The current values are then delivered to electro-hydraulic control valves which control the fluid flow to the respective actuators.
With reference to
FIG. 5
, a flow diagram is shown illustrating the operation of an embodiment of the present invention.
In a first control box
510
, the angle of the boom
160
relative to the frame
130
is sensed by the angle sensor
220
, and the actual angular velocity of the boom
160
is responsively determined.
In a second control box
520
, the length of the boom
160
is sensed by the length sensor
230
, and the actual linear velocity of the boom
160
is responsively determined.
Control then proceeds to a third control box
530
in which the desired velocity of the boom
160
is commanded by the input device
270
. The inclination of the machine frame
130
relative to the reference plane
110
is sensed by the inclination sensor
280
in a fourth control box
540
, and the desired velocity of the boom
160
is responsively modified.
In a fifth control box
550
, a desired angular velocity and a desired linear velocity is determined by the control system
240
as a function of the desired velocity of the boom
160
commanded by the input device
270
, the angle of the boom
160
relative to the frame
130
, and the length of the boom
160
.
Control then proceeds to a sixth control block
560
and a seventh control block
570
. An actual velocity ratio and a desired velocity ratio is determined in the sixth control block
560
. The actual velocity ratio represents the actual angular velocity relative to the actual linear velocity. Similarly, the desired velocity ratio represents the desired angular velocity relative to the desired linear velocity.
The actual velocity ratio is compared to the desired velocity ratio, and the desired velocity ratio is responsively modified in the seventh control block
570
.
In an eighth control block
580
, the first and second actuators
140
,
150
are actuated as a function of the desired velocity ratio.
Industrial Applicability
As one example of an application of the present invention, telescopic material handlers are used generally for loading various types of material. In such applications, linear movement of the boom is often required. For example, when the forks of the telescopic material handler are to be driven under a pallet in order to lift the pallet, linear movement of the fork in the horizontal plane is required. Similarly, when the pallet is to be lifted in the vertical direction, linear movement of the fork in the vertical plane is required. In both situations, the length and angle of the boom must be simultaneously coordinated to effect such movement.
The control system of the present invention receives a desired velocity request from an operator via an input device, e.g., a joystick. The desired velocity includes a desired angular velocity of the boom, and a desired linear velocity of the boom. The desired angular velocity and the desired linear velocity represents the desired velocities of the respective hydraulic cylinders. The desired velocities are converted to desired flows to the respective cylinders.
However, in some situations, one or more of the cylinders does not receive the desired flow due to the increased demand of another cylinder. As a result, the cylinders do not operate in proportion to operator demand. Operators frequently experience fatigue attempting to avoid or overcome such situations.
The control system of the present invention attempts to eliminate problems of this type, by calculating a compensating error as a function of a comparison between the actual velocity of the boom, and the desired velocity of the boom. This compensating error is used to modify the desired angular velocity and the desired linear velocity, which in turn are used to simultaneously coordinate the flow to the respective hydraulic cylinders to provide linear movement of the fork, thus reducing operator fatigue and improving efficiency.
Other aspects, objects, and features of the present invention can be obtained from a study of the drawings, the disclosure, and the appended claims.
Claims
- 1. An apparatus for providing coordinated control of an implement of a work machine having a frame, the implement comprising a boom having a first end portion and a second end portion, with the first end portion pivotally connected to the frame and the second end portion pivotally connected to a load-engaging member, comprising:a position sensor adapted for delivering a position signal; an input device adapted for delivering a desired velocity signal indicative of a desired velocity of the load-engaging member, the desired velocity including a desired angular velocity and a desired linear velocity; and a control system adapted for receiving the position signal and the desired velocity signal, and responsively determining an actual path of travel of the load-engaging member, a desired path of travel of the load-engaging member, a desired velocity ratio, and an actual velocity ratio, the control system being further adapted for modifying the desired angular velocity and the desired linear velocity as a function of the actual and desired velocity ratios in response to a deviation between the actual and desired paths of travel.
- 2. An apparatus, as set forth in claim 1, wherein the control system is adapted for determining an actual velocity of the load-engaging member as a function of the position signal.
- 3. An apparatus, as set forth in claim 2, wherein the control system is adapted for modifying the desired angular velocity and the desired linear velocity in response to both the deviation between the actual and desired paths of travel, and a difference between the desired and actual velocities of the load-engaging member.
- 4. An apparatus for providing coordinated control of an implement of a work machine having a frame, the implement comprising a boom having a first end portion and a second end portion, with the first end portion pivotally connected to the frame and the second end portion pivotally connected to a load-engaging member, comprising:a position sensor adapted for delivering a position signal; an input device adapted for delivering a desired velocity signal indicative of a desired velocity of the load-engaging member, the desired velocity including a desired angular velocity and a desired linear velocity; and a control system adapted for receiving the position signal and the desired velocity signal, and responsively determining an actual path of travel of the load-engaging member, a desired path of travel of the load-engaging member, an actual velocity of the load-engaging member as a function of the position signal, and an actual angular velocity ratio and an actual linear velocity ratio, the control system being further adapted for modifying the desired angular velocity and the desired linear velocity in response to a deviation between the actual and desired paths of travel, wherein the actual angular velocity ratio is computed by dividing the actual angular velocity by a summation of both an absolute value of the actual angular velocity and an absolute value of the actual linear velocity; and wherein the actual linear velocity ratio is computed by dividing the actual linear velocity by a summation of both an absolute value of the actual angular velocity and an absolute value of the actual linear velocity.
- 5. An apparatus, as set forth in claim 4, wherein the control system is adapted for determining an actual velocity ratio as a function of the actual angular velocity ratio and the actual linear velocity ratio.
- 6. An apparatus, as set forth in claim 5, wherein the control system is adapted for determining a desired angular velocity ratio and a desired linear velocity ratio;wherein the desired angular velocity ratio is computed by dividing the desired angular velocity by a summation of both an absolute value of the desired angular velocity and an absolute value of the desired linear velocity; and wherein the desired linear velocity ratio is computed by dividing the desired linear velocity by a summation of both an absolute value of the desired angular velocity and an absolute value of the desired linear velocity.
- 7. An apparatus, as set forth in claim 6, wherein the control system is adapted for determining a desired velocity ratio as a function of the desired angular velocity ratio and the desired linear velocity ratio.
- 8. An apparatus, as set forth in claim 7, wherein the desired angular velocity ratio and the desired linear velocity ratio are responsively modified based on a difference between the desired velocity ratio and the actual velocity ratio.
- 9. An apparatus, as set forth in claim 1, wherein the input device is adapted for commanding a desired velocity of the boom along a first axis, and a desired velocity of the boom along a second axis, wherein the first axis is perpendicular to the second axis.
- 10. An apparatus, as set forth in claim 1, further comprising:a first actuator associated with the boom; a second actuator associated with the boom; and wherein the control system is adapted for actuating the first actuator and the second actuator as a function of the desired angular velocity and the desired linear velocity, respectively.
- 11. An apparatus, as set forth in claim 10, wherein the first actuator is adapted for controlling an angle of the boom relative to the frame.
- 12. An apparatus, as set forth in claim 10, wherein the second actuator is adapted for controlling a length of the boom.
- 13. An apparatus, as set forth in claim 10, wherein each of the first and second actuators includes a hydraulic cylinder.
- 14. An apparatus, as set forth in claim 1, wherein the position sensor includes at least one of an angle sensor adapted for sensing an angle of the boom relative to the frame, a length sensor adapted for sensing a length of the boom, and an inclination sensor adapted for sensing an angle of inclination of the frame relative to a reference plane.
- 15. An apparatus, as set forth in claim 14, wherein the boom includes a telescopic member movable between a fully retracted length and a fully extended length, wherein the length sensor is adapted for sensing a length of the telescopic member.
- 16. An apparatus, as set forth in claim 1, wherein the input device includes a control lever.
- 17. An apparatus, as set forth in claim 1, wherein the input device includes a joystick.
- 18. An apparatus, as set forth in claim 1, wherein the input device is located on the work machine.
- 19. An apparatus, as set forth in claim 1, wherein the input device is located remote from the work machine.
- 20. An apparatus, as set forth in claim 1, wherein the control system is located remote from the work machine, the control system being adapted for receiving the boom position signal and the desired boom velocity signal through a wireless communication link.
- 21. An apparatus, as set forth in claim 1, wherein the load-engaging member includes a fork.
- 22. An apparatus, as set forth in claim 1, wherein the load-engaging member includes a bucket.
- 23. A method for providing coordinated control of an implement of a work machine having a frame, the work implement comprising a boom having a first end portion and a second end portion, with the first end portion pivotally connected to the frame and the second end portion pivotally connected to a load-engaging member, comprising the steps of:sensing a position of the load-engaging member, and responsively delivering a position signal; delivering a desired velocity signal indicative of a desired velocity of the load-engaging member, the desired velocity including a desired angular velocity and a desired linear velocity; determining a desired velocity ratio as a function of said desired velocity; determining an actual path of travel of the load-engaging member as a function of the position signal; determining a desired path of travel of the load-engaging member as a function of the desired velocity signal; and modifying the desired angular velocity and the desired linear velocity as a function of said desired velocity ratio in response to a deviation between the actual and desired paths of travel.
- 24. A method, as set forth in claim 23, further including the step of determining an actual velocity of the load-engaging member as a function of the position signal.
- 25. A method, as set forth in claim 24, further including the step of modifying the desired angular velocity and the desired linear velocity in response to both the deviation between the actual and desired paths of travel, and a difference between the desired and actual velocities of the load-engaging member.
- 26. A method, as set forth in claim 24, further including the steps of:determining an actual angular velocity ratio and an actual linear velocity ratio; and determining a desired angular velocity ratio and a desired linear velocity ratio.
- 27. A method for providing coordinated control of an implement of a work machine having a frame, the work implement comprising a boom having a first end portion and a second end portion, with the first end portion pivotally connected to the frame and the second end portion pivotally connected to a load-engaging member, comprising the steps of:sensing a position of the load-engaging member, and responsively delivering a position signal; delivering a desired velocity signal indicative of a desired velocity of the load-engaging member, the desired velocity including a desired angular velocity and a desired linear velocity; determining an actual path of travel of the load-engaging member as a function of the position signal; determining an actual velocity of the load-engaging member as a function of the position signal; determining a desired path of travel of the load-engaging member as a function of the desired velocity signal; determining an actual angular velocity ratio by dividing the actual angular velocity by a summation of both an absolute value of the actual angular velocity and an absolute value of the actual linear velocity and an actual linear velocity ratio by dividing the actual linear velocity by a summation of both an absolute value of the actual angular velocity and an absolute value of the actual linear velocity; determining a desired angular velocity ratio by dividing the desired angular velocity by a summation of both an absolute value of the desired angular velocity and an absolute value of the desired linear velocity and a desired linear velocity ratio by dividing the desired linear velocity by a summation of both an absolute value of the desired linear velocity and an absolute value of the desired angular velocity; and modifying the desired angular velocity and the desired linear velocity in response to a deviation between the actual and desired paths of travel.
- 28. A method, as set forth in claim 27, further including the steps of:determining an actual velocity ratio as a function of the actual angular velocity ratio and the actual linear velocity ratio; and determining a desired velocity ratio as a function of the desired angular velocity ratio and the desired linear velocity ratio.
- 29. A method, as set forth in claim 28, further including the step of modifying the desired angular velocity ratio and the desired linear velocity ratio in response to a difference between the desired velocity ratio and the actual velocity ratio.
- 30. A method, as set forth in claim 23, further comprising the step of actuating a first actuator and a second actuator as a function of the desired angular velocity and the desired linear velocity, respectively.
- 31. A method, as set forth in claim 23, wherein sensing the position of the load-engaging member includes the steps of:sensing an angle of the boom relative to the frame; sensing a length of the boom; and sensing an angle of inclination of the frame relative to a reference plane.
US Referenced Citations (10)