THE EFFECT OF TIME-DELAY AND DISCRETE CONTROL ON THE CONTACT STABILITY OF SIMPLE POSITION CONTROLLERS

By analysis of the driving-point admittane, it is shown how time delay s and discrete control can create instabilities for a simple position controller in contact with the environment. The lowest frequency of co ntact instability due to time delay or sampling is determined analytic ally. It is shown bow mechanical compliance between the motor and poin t of contact can eliminate these instabilities. To achieve the best re lative stability when contacting arbitrary environments, the mechanica l/control design of manipulators should maintain a critical relationsh ip between the frequency of the compliant mode and a frequency associa ted with contact instability.