Abstract: A closed loop servo operated digital control system in which a dynamically operable moveable member can be effectively and accurately controlled during movement from an initial position to a command position by compensating for both velocity error and for position error. A differential between a present measured position of the moveable member and a command position provides a position error signal. Present velocity is determined by computing position differential as a function of time. A velocity error signal is obtained by subtracting the determined velocity from a velocity command which is stored as a velocity command profile. The total error is the resultant sum of the position error and a velocity error and this sum is converted to an analog signal in order to power an amplifier/motor which, in turn, provides power for the control system.

Abstract: A digital positioning system having high accuracy is disclosed, which employs an incremental position optical encoder as the position transducer. In response to the output signal from the encoder, the system provides coarse and fine position signals which are combined to form a composite digital signal representing the absolute position of a moveable control member. The composite position signal has a resolution of greater than one part in one million. Trigonometric conversion techniques are used to derive high resolution incremental position information from the encoder output signals.