Implement pressure control for hydraulic circuit

Details Implement pressure control for hydraulic circuit Implement pressure control for hydraulic circuit

2001-12-28

2004-02-17

Look, Edward K. (Department: 3745)

Motors: expansible chamber type

With motive fluid valve

Both inlet and exhaust controlled by motive fluid pressure...

C091S454000

Reexamination Certificate

active

06691603

ABSTRACT:

TECHNICAL FIELD
The invention relates generally to a fluid control system and, more particularly, to a control algorithm that provides pressure control of an implement for a hydraulic circuit.
BACKGROUND
Conventional hydraulic systems, for example, those implemented in large excavators, typically include an open center hydraulic system for implements because a closed center system may not provide the operator with as much of a “feel” for how much of a load is resisting movement of an implement, as an open center system does. This loss of “feel” results from the closed center system having pressure compensated flow control that keeps the flow to the working cylinder substantially constant. However, the open center system is generally less efficient than a closed center system because some or all fluid flow in the open center system usually gets to tank without performing any work, depending on the flow request from the operator.
A hydraulic circuit may include a pressure sensor or an implement position sensor associated with an actuator, for example, a cylinder. The sensor provides signals to an electronic controller so that fluid flow to the actuator is controlled with the control algorithm that uses sensor feedback signals. One typical hydraulic circuit, as shown in U.S. Pat. No. 5,737,993, includes cylinder pressure sensors associated with hydraulic cylinders. The sensors deliver cylinder pressure signals to a controller, which uses the signals to generate cylinder force signals, for example, current commands, usable by a valve assembly to provide hydraulic fluid flow to the cylinders. The circuit does not control fluid flow from the hydraulic cylinders to the tank.
A fluid control system for effectively and efficiently controlling pressures of working and non-working chambers of an actuator is desired. It is also desired to provide an open center feel to a closed center hydraulic system for operating an implement. The present invention is directed to solving one or more of the problems set forth above.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a method is provided for controlling a hydraulic system. The method may include receiving an input command from an input device, generating a desired working pressure value relating to a working chamber of an actuator based on the input command, and generating a desired pressure value relating to a non-working chamber of the actuator based on the input command. The method may also include operating a valve assembly to control a fluid flow condition of the working chamber and to control fluid flow from the non-working chamber.
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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