Design of a Torsion Torque Estimator that Includes a Backlash Model for a Load-Side Angle Control System that Consists of a Motor, a Reduction Gear, a Spring, and Motor/Load-Side Encoders

In order to reduce the weight of industrial and collaborative robots and also improve force control performance, the tip of the motor output shaft and reducer output shaft may be configured with low-rigidity mechanical parts. The problem with this, however, is that the mechanical resonance frequency decreases, and, as a result, vibration is more likely to occur during high-speed operation. To solve this problem, a method of suppressing vibration by feeding back the torsional torque of the low-rigidity mechanical parts, but this leads to excitation of vibration and steady deviation due to estimation error occur. Therefore, in this paper, we propose a torsional torque estimator with a backlash model that uses both motor angle and load angle through low-rigidity machine parts. The effectiveness of the proposed method is illustrated through simulations and experiment.