Observer-compensator for an electric motor system

Apparatus for compensating for unmeasurable disturbance forces in a positioning motor system of the type which comprise:

• a computer controller for generating a plurality of command signals indicative of desired motor positions,
• an encoder coupled to the motor in said motor system for generating actual motor position signal signals,
• said actual motor position signal being coupled to said computer controller for indicating an actual motor position and velocity, and
• an observer-compensator coupled in a feed forward loop between the command signal output of said computer controller and the actual motor system,
• said observer-compensator comprising an ideal motor simulator coupled to the command signal output for simulating the actual motor system without said unmeasurable disturbance forces, and
• a disturbance force reconstruction device having an output coupled to the input of said actual motor system for compensating for said unmeasurable disturbance forces.

A method of compensation for unmeasurable disturbance forces in a high speed motor system of the type which includes a computer controller programmed to generate a plurality positioning command signals that are coupled as drive signals to a motor having an encoder for indicating its actual position, the output of the encoder is coupled through a feedback loop to the computer controller that calculates the next command signal, comprising the steps of:

• connecting an observer compensator in a feed forward loop between the command signal output of said computer controller and the input to said motor system for modifying said command signal,
• reciprocating said motor in a limited operable range of positions where negligible disturbance forces occur,
• adjusting an ideal motor simulator (43, 49) in said observer-compensator to closely equal the actual motor when negligible disturbance forces occur,
• reciprocating said motor in a limited operable range of positions where very high unmeasurable cogging forces occur,
• adjusting a disturbance reconstruction device (51,55) in said observer-compensation to closely equal the unmeasurable disturbance forces when high disturbance forces occur,
• subtracting the output (@ 34) of said disturbance reconstruction device (51,55) from the positioning command signal that are coupled as drive signals to motor system.