Digital servo employing switch mode lead/lag integrator
AssigneeHughes Aircraft Company
InventorDaniel D. Evans, Jr.
Life of this patent
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Abstract
A digital servo system for causing a mechanical element (48) to track a desired path and hold various positions along the path and employing a lead/lag integrator (18) in parallel with a feedback control loop. The input to the integrator (18) is switched between velocity (V.sub.EK) error during pathtracking and position error (E.sub.K) during holding to increase the resistance of the mechanical element (48) to position changes caused by outside forces during both pathtracking and holding. The integrator function employed uses a term (U.sub.integrator(k-1)) representing a previous integrator output value to assist in smoothing perturbations caused by switching between position and velocity error.
Claims26
Servo positioning apparatus for use in moving and holding a mechanical element comprising:
- means for outputting a desired position signal representative of a desired position of said element;
- means for generating a velocity error signal representing departure of the velocity of said element during movement from a desired velocity;
- a feedback loop including means for generating a position error signal related to the difference between the actual position of said element and the desired position of said element represented by said desired position signal, said feedback loop further including means for applying a transfer function to said error signal to generate a feedback control signal;
- and
- means receiving said position error signal as an input for generating an integrator error signal, said integrator error signal being determined in accordance with said velocity error signal during movement of said element and said position error signal during holding of said element, and for integrating said integrator error signal to generate an integrator control signal for combination with said feedback control signal.
A method of generating a control signal for controlling moving and holding of a mechanical element comprising the steps of:
- generating path data representing a desired path of travel of said mechanical element, said path data comprising a series of successive desired path position signals;
- generating successive actual path position signals representing the actual position of said element;
- generating a succession of position error signals representative of the difference between successive pairs of the actual position signals and the desired position signals;
- generating a succession of feedback control signals from said error signals;
- generating a succession of velocity error signals;
- generating a succession of integrator control signals, said integrator control signals being generated utilizing an integrator error signal comprising a velocity error signal when the velocity of said element is nonzero and a position error signal when the velocity of said element is zero;
- and
- combining said feedback control signals and integrator control signals to generate an output control signal for controlling movement of said element.
Dependencies are inferred from the claim text.