Experimental analysis of the disturbances affecting contact force in industrial robots

This paper describes the results of an experimental research on the disturbances acting on the measured force during contact motion of industrial robots. Two phenomena have been found to be mainly responsible for these disturbances, namely the arm structural elasticity due to the torsional flexibility of the joints and the torque ripple of the brushless motors. The structural elasticity is characterized by a resonance frequency function of the arm configuration, while the torque ripple has a principal harmonic of frequency proportional to the motor velocity. Though obtained on a particular experimental setup, these results should be of general interest, since both joint flexibility and torque ripple are common drawbacks of most industrial robots