Patent ID: 6037735
Filing Date: 2000-03-14
Classification: G05B

Abstract:
A slow-speed servomechanism, comprising:a) a motor for driving a load;b) a direct drive transmission between the motor and the load;c) an incremental optical encoder connected to the load, the encoder having analog sine and cosine outputs;d) an analog to digital converter for converting the sine and cosine analog values to digital values; ande) a digital controller, connected to the motor and the analog to digital converter, for controlling the motor, the digital controller includingi) angle decoder means responsive to the sine and cosine digital values from the analog to digital converter to produce a relative position count indicating a position within one sine and cosine signal pair,ii) cycle counter means responsive to the relative position count for producing an absolute position count within the operating range of the servomechanism by determining which sine cosine pair is being measured, the angle decoder and cycle counter performing at least four angle decodes within each encoder sine and cosine cycle,iii) a command generator responsive to a user defined desired motion of the load to output a desired count,iv) a phase detector responsive to the absolute position count from the cycle counter and the desired count from the command generator to produce an error signal, andiv) a compensation filter responsive to the error signal for generating a motor driving command.