Power feedback control in cylindrical plunge grinding with an inner repetitive position control loop

This paper describes the design of a power controller for cylindrical plunge grinding, which controls the power consumed by the grinding wheel by regulating the plunge feed. A mathematical model relating the power to the plunge feed has also been developed and quantified herein with machining data. Based on this model, a proportional plus integral (PI) controller has been designed and tuned to fulfill time response specifications. An inner position loop was also designed and implemented inside the power close loop to guarantee a stable power response. The commanded position is generated by sending small steps for the servo to follow. In this way, the stiction can be treated as a perturbation with constant period, and its effect can be mitigated using repetitive controller - a subclass of learning control. Both controllers were implemented and tested on an open architecture cylindrical grinding machine. The repetitive controller was shown to be effective by repeated learning to eliminate the periodic friction effect. The grinding controller showed a robust response to changes in the width of cut, by adjusting the feed to maintain constant grinding power.