Globoidal cam indexing servo drive control by IVSMFC with load torque estimator

This paper introduces an integral variable-structure model-following control (IVSMFC) incorporated with a load torque estimator based on variable-structure technique for a globoidal cam indexing system. IVSMFC features excellent robustness and performance properties under certain disturbances and parameter variations. However, heavy time-varying load may influence expected performance. In a cam system, when it is in motion, the load produced by inertia forces deflects the driving motor speed and, as a result, degrades the indexing precision. To fulfill the constant driving speed assumption, a load torque estimator is employed and fed forward to compensate the load torque variations. A digital-signal-processor-based globoidal cam indexing servo drive is presented and the experimental results show the effectiveness of the proposed scheme.