Power plants – Pressure fluid source and motor – Condition responsive control of pump or motor displacement
Patent
1985-05-07
1987-01-13
Croyle, Carlton R.
Power plants
Pressure fluid source and motor
Condition responsive control of pump or motor displacement
60911, 91506, F16D 3102
Patent
active
046354417
ABSTRACT:
A power drive unit and control system therefor avoiding performance degradation which can occur in control of the variable displacement hydraulic motor of the power drive unit by measurement of the angle of a displacement-setting wobbler of the motor and the speed of the motor. This is avoided by sensing flow through the motor which provides an indirect measure of wobbler position and speed of motor operation. The power drive unit and control system therefor has a variable displacement hydraulic motor with a displacement-setting wobbler positioned by pressure applied to a servo piston by an electro-hydraulic servo valve. The control system responds to a speed command having a value dependent upon a position loop which determines the relation between the actual position of a load and a commanded position, with the control providing for a maximum possible speed of motor operation under a particular load condition with a substantially constant rate of fluid flow through the motor. As the load varies, the flow through a flow-regulator valve varies and flow is sensed by a linear variable differential transformer associated with the valve member of the flow regulator. The linear variable differential transformer outputs a control voltage indicative of a variation in either direction from the desired rate of fluid flow through the motor which is used to adjust the angle of the wobbler to bring the flow to the desired rate and the motor is caused to operate at a maximum possible speed. The control, by using a speed command responsive to a position loop, provides a controlled snubbing action to reduce the speed of the motor as the load approaches the commanded position.
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Beneditz Bruce D.
Ebbing Steven J.
Hermans Robert J.
Vicari John J.
Croyle Carlton R.
Neils Paul F.
Sundstrand Corporation
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