Motors: expansible chamber type – With motive fluid valve – Both inlet and exhaust controlled by motive fluid pressure...
Reexamination Certificate
2002-01-08
2003-10-28
Look, Edward K. (Department: 3745)
Motors: expansible chamber type
With motive fluid valve
Both inlet and exhaust controlled by motive fluid pressure...
C074S4710XY
Reexamination Certificate
active
06637311
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a feedback system for an electro-hydraulically controlled system. More particularly, the invention relates to a system that provides an operator with sensory feedback corresponding to a force applied to an electro-hydraulically controlled system.
BACKGROUND
Work machines, such as, for example, wheel loaders, track loaders, backhoes, excavators, and bulldozers, often use hydraulic systems to power a work implement to perform work. These work machines also typically include an operator interface, such as, for example, a control lever or joystick, that an operator may manipulate to control the movement of the work implement. During operation of the work machine, the operator may desire feedback from the work machine regarding the magnitude of the force required by the work implement to perform a particular work task. Given this feedback, the operator may modify the work being performed by the work implement to more efficiently perform the work task. For example, if the work machine is excavating material from a work site and the feedback indicates that the work machine is having to exert a great force to lift the material, the operator may alter the motion of the work implement to excavate less material or to adjust the position of the work implement to avoid an impediment, which may be a large rock or other obstacle.
The work machine may include a feedback system to provide the operator with information regarding the amount of work being performed by the work implement. The feedback may include an indication of how much force the hydraulic system is exerting to move the work implement. The feedback system may present the feedback to the operator in a variety of forms.
The recent trend in work machine control systems is towards electronic control systems that provide the operator with a better control of the machine. These electronic control systems may be operated, for example, by turning on a switch or by touching a keypad. However, these electronic control systems are not typically capable of providing a tactile feedback to the operator. When operating the electronic controls, the operator must determine the force exerted on the hydraulic system through other means, such as, for example, closely observing the response time of the work implement.
One feedback system is described in U.S. Statutory Invention Registration H1,850, issued Jun. 6, 2000, to Daniel E. Zimmerman. In this system, a cable is wound around the pivotal position of a joystick. Both ends of the cable are attached to plungers that are pulled toward each other when an electrical current is applied to a solenoid. This system, however, is intended to center the joystick and does not provide an operator with a tactile sense (or “feel”) that is indicative of the work done being performed by the work machine.
The present invention is directed to solving one or more of the problems set forth above.
SUMMARY OF THE INVENTION
One aspect of the present invention is directed to an apparatus for providing feedback to an operator relative to a force applied to a system. The apparatus includes a first magnet configured to receive a signal indicative of the force applied to the system and to generate a first magnetic field in response to the signal. A second magnet is disposed adjacent the first magnet and is configured to generate a second magnetic field that interacts with the first magnetic field to generate a magnetic force. An operator interface is operatively engaged with one of the first magnet and the second magnet such that the magnetic force acts on the operator interface.
Another aspect of the invention is a method of controlling a hydraulic actuator having a first chamber and a second chamber. An operator interface is operated to generate a flow of pressurized fluid to at least one of the first and second chambers. A pressure representative of the pressure of the fluid in at least one of the first and second chambers is sensed. A signal based on the sensed pressure is generated. The signal is transmitted to at least one of a first and second magnets to generate a magnetic force that acts on the operator interface.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
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Caterpillar Inc
Finnegan Henderson Farabow Garrett & Dunner
Lazo Thomas E.
Look Edward K.
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