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US 4,537,077 AGranted
Load dynamics compensation circuit for servohydraulic control systems
AssigneeMTS Systems Corporation
InventorsAllen J. Clark, Dale N. Maue
Life of this patent
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AssigneeMTS Systems Corporation
InventorsAllen J. Clark, Dale N. Maue
Estimating the term…
A load dynamic compensation circuit for a servohydraulic control system for fixtures and specimens being tested operating in various degrees of freedom, for example in an environment to simulate earthquakes to test building specimens, or to provide road profile simulation for rail and automobile vehicles, or wind buffet loads for aircraft. A compensation circuitry compensates for specimen displacement disturbances in the control loop that are a function of the force exerted from the specimen and the acceleration of the test mass. This specimen disturbance factor may be provided by adding only a differential pressure transducer to measure the force on the actuator, and an accelerometer to measure the mass acceleration, to obtain the necessary electrical signals, which after being modified by factors including the oil column compliance spring factor, the piston area and the servovalve flow gain, is differentiated to compensate for the piston integration, and is then added in a summing junction into the servovalve command signal loop. The compensation signal is an anticipatory signal compensating for load dynamics on the specimen.
In a servo controlled displacement generating apparatus having control means for generating an error signal representing the desired displacement of a servovalve that will provide a desired displacement of a heavy dynamically operated load, said load being driven by an actuator having an area and a displacement, said actuator being provided with hydraulic oil through said servovalve, the improvement comprising:
A test apparatus having a table movable under control of an actuator, said table having a mass, and said actuator being operated with hydraulic oil under pressure, a servovalve for actuating said actuator, control means for providing an error signal to control the displacement of said servovalve including feedback stabilization circuitry for closed loop control, a summing junction on the input side of said servovalve, and means for providing an electrical component signal to said servovalve comprising means for providing a first signal proportional to the mass acceleration of said fixture, means for providing a second signal proportional to the force of the actuator, and differential amplifier means for receiving a third signal representing the second signal minus the first signal and differentiating said third signal and including scaling means for scaling the third signal as a function of the area of the actuator, and for dividing the signal by a factor which is a product of compliance factor of the oil and the flow gain of the servovalve.
Dependencies are inferred from the claim text.