Modelling for Contact Stress Control in Automated Polishing

This research pertains to the initial steps in designing an end-effector for automated polishing, and focuses on: (1) controlling the contact stress on the work-piece surface, and (2) controlling the torque or the spindle speed to overcome the friction torque (hence, preventing the tool from stalling) and maintain a desired polishing rate. By forming a contact stress model, parameter planning is achieved and then augmented to already existing tool path data. A dynamic model for the particular end-of-arm tooling used is derived. The dynamic model clearly shows a coupling effect between the pressure and spindle speed of the system. A closed-loop control scheme, designed to eliminate the coupling is then introduced. The effectiveness of parameter planning is assessed through open loop testing. The parameter planning method allows polishing without significantly changing the part profile, whereas, without the parameter planning, the part profile is changed considerably.