Compensation of motor torque disturbances in industrial robots

Permanent magnet AC motors generate parasitic torque pulsations, owing to several electromagnetic phenomena. Excitation of the mechanical resonances on the load side is generally the worst consequence of these disturbances. Speed oscillations arise which may dramatically limit the performances in high precision applications. In the paper a control scheme which autonomously identifies the parameters of the disturbance model, through simple closed loop motion experiments, is outlined. Experiments carried out on an industrial robot demonstrate the effectiveness of the control scheme in suppressing oscillations, both on the motor and on the load side.