A linearized model for control of automated polishing process

Automation of polishing process requires control of tool pressure and tool speed. Due to friction between the tool and the part, the tool speed is affected when the tool pressure is changed, and this coupling relationship is nonlinear. In this paper, a linearized model is presented for control of automated polishing process. To do so, first, the contact stress model is introduced based on a Hertzian contact model, which relates the tool pressure to the contact stress of the contact area on the part. Second, the friction torque resulting from the contact area is derived, which relates the tool pressure to the tool speed. Then, the nonlinear coupling system is linearized with respect to the control voltages of the control valves, one for pressure and another for speed. Simulations are carried out to verify the linearized model against the original nonlinear model