Power plants – Pressure fluid source and motor – Condition responsive control of or by input to input pump...
Reexamination Certificate
1999-12-15
2002-03-19
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Condition responsive control of or by input to input pump...
C074S512000
Reexamination Certificate
active
06357232
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to operator interface systems for controlling the movement and operation of a work machine and, more particularly, to a differential pedal interface system for controlling the locomotion of a work machine.
BACKGROUND ART
Currently, when driving a work machine such as a wheel loader, the machine operator is faced with simultaneously controlling machine speed, jerk, acceleration, deceleration, direction, steering and implements. In fact, control of some of these parameters is achieved indirectly. For example, when driving a conventional wheel loader, the operator controls the operation and performance of the machine through a conventional interface system which includes operating and controlling a plurality of interface devices such as a throttle pedal, impeller clutch/brake pedal, brake pedals, toggle and other types of switches, steering wheel or joystick, implement levers or joystick, and other interface controls. Typically, a combination of operator control inputs to a plurality of the above-identified control inputs are necessary in order to achieve a specific control function such as speed, acceleration, deceleration, forward or reverse movement, steering and implements. Conventional interface speed control functions in the forward or reverse direction likewise involve use of both feet, while low speed operation is further complicated by machine-to-machine variations associated with the impeller-brake pedal adjustment. In order to achieve desired speed on certain wheel loaders, the operator controls engine torque by varying the throttle setting. In order to maneuver the machine at slow speeds, the operator must control both the throttle setting and the impeller clutch pedal. Also, acceleration of the machine involves control inputs different from the inputs necessary to achieve deceleration of the machine. In addition, often times switches such as a forward/reverse direction switch needs to be actuated and coordinated with movements of the operator's feet while steering and otherwise controlling the machine. To effectively control all of these parameters, while simultaneously manipulating the plurality of interface devices, requires that the operator have extensive experience in operating and controlling the particular machine.
In this regard, it would be beneficial to control machine parameters in a direct fashion so as to reduce the total number of control inputs which must be exercised by the operator. This can be accomplished by consolidating intuitively associated variables with a particular input. However, this puts a greater emphasis on the operator's ability to precisely control the particular input. Therefore, while it is possible for an inexperienced operator to adequately control a particular machine, the operator will normally not be able to take advantage of the machine's full potential or capability until after some operator time has been achieved. It is therefore desirable to have an operator interface system which is simple, intuitive, predictable, precise and easy to learn.
Additionally, terrain irregularities have the potential to be transferred into undesirable control inputs. Uneven terrain and other irregularities are common in the work environment where these types of machines are routinely used and, often times, such uneven terrain affect the various operator inputs to control the operation of the machine. As a result, it is often necessary for the operator to operate the machine at a substantially lower speed when encountering irregular terrain. Operating the machine at lower speeds reduces the ability to complete a particular task.
Irregular terrain therefore translates into unwanted mechanical disturbances which may be inputted to the machine via the operator input system. Consider, for example, a single pedal whose position is mapped into desired machine speed. As the operator varies the pedal's displacement, the machine accelerates or decelerates to match the speed setting marked by the pedal's position. The operator's ability to precisely control such input may be satisfactory on a smooth highway, but will degrade substantially when the machine travels over rough terrain or engages in a cycling application such as truck loading. In fact, when the machine travels over bumps, the operator's foot will bounce, resulting in abrupt changes in the requested speed, causing sudden acceleration and deceleration of the machine, or jerk, with the potential for self-excitation to occur in the operator-machine interface system.
Since conventional interface systems are complicated and cumbersome to control, particularly for an inexperienced operator, it is desirable to design an operator-machine interface system which not only allows inexperienced operators to easily utilize the machine's full potential, but which allows the speed, acceleration, deceleration and jerk of the machine to be controlled through a minimum number of operator inputs. It is also desirable to provide an interface system which will effectively cancel unwanted mechanical disturbances due to travel over irregular terrain.
Accordingly, 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 operator-machine differential pedal interface system is disclosed wherein a pedal arrangement is positioned and located in the operator compartment, the present pedal system being symmetrically located to the left and right of the steering column such that the operator can comfortably deflect such pedals with the left and right foot respectively. The present pedals are linked in such a way that if one pedal is deflected in a certain direction, the other pedal moves an equal amount in the opposite direction. Also, one pedal controls movement in the forward direction and the other pedal controls movement in the reverse direction. For example, the right pedal can be configured to control movement in the forward direction whereas the left pedal can be configured to control movement in the reverse direction. In the absence of control input from an operator, the present pedal system includes a mechanism for self-centering the respect pedals to a neutral position.
Importantly, several embodiments of the present pedal system include at least one sensor positioned and located so as to output a signal indicative of the relative position or displacement of the pedals in either the fore or aft direction relative to a centered
eutral position. This position sensor is coupled to an electronic control module (ECM), or other processing or controller means, and continuously outputs signal(s) to the ECM indicative of pedal displacement. Based upon both pedal position and the rate of movement of such pedals, the ECM, or other control means, is programmed to output appropriate signals to appropriate machine control systems to control the speed, acceleration, deceleration, and jerk of the machine in either the forward or reverse directions. For example, if the right pedal is configured to control forward movement of the machine and the left pedal is configured to control reverse movement of the machine, movement of the right pedal in a forward direction away from a centered or neutral position will be interpreted by the ECM as an operator input command requesting that the machine accelerate to and achieve a desired machine speed in the forward direction. The acceleration of the machine to the desired speed is a function of the rate of movement and/or position of the right pedal in the forward direction, and the requested final speed of the machine is a function of the final position or displacement of the right pedal relative to the centered or neutral pedal position. The rate of movement of the right pedal can be determined by the ECM based upon the relative change of the displacement of the pedal over time. The same correlation is likewise true with respect to movement of the machine in the reverse direction, the accelerati
Caterpillar Inc.
Lazo Thomas E.
Look Edward K.
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