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.

Abstract: A power drive unit for thrust reverser structure includes a reversible motor in a hydraulic circuit and has normal stow and deploy cycles of operation. In a deploy cycle, the load on the motor is aiding and, in the event the deploy cycle is inadvertent, the load on the motor can be substantially higher. In order to avoid this increased loading on the motor in an inadvertent deploy cycle, the hydraulic circuit has an auto-restow valve which senses the high aiding load in the event of an inadvertent deploy operation and changes the operation of the power drive unit to operate the motor in a stow cycle to prevent continued high loading on the motor and thrust reverser structure.

Abstract: This invention relates to a motor control unit and a feedback arrangement to minimize the effects of backlash in a rotary output system. The system includes a source of energy. The motor control has a directional control element moveable from a null position. The motor control unit is coupled to the source of energy and to a motor which in turn is coupled to the rotary output and to a second input of a differential harmonic drive that has first and second inputs and an output. The first input of the differential harmonic drive is coupled to a rotational command input unit and the differential harmonic drive output is drivingly coupled to the moveable direction control element. In response to a given rotational command input when the second input is in an initial static position, whereupon the motor is coupled to the source of energy through the motor control unit, the rotary output is driven a precise number of revolutions dependent upon the given rotational command input.