Force sensorless control in a flexible link arm based on estimated reaction torque

This paper describes a nobel method of force/torque sensorless control for a single link flexible arm. The flexible arm includes multiple oscillation modes and its dynamical behavior is generally described as multiple mass spring system. In such a system, it is necessary to suppress the vibrations induced by the multiple oscillation modes. To address the above issue, first, this paper shows that the system stability increases by a feedback of reaction torque. In the proposed approach, the reaction torque is identified by using disturbance observer. Furthermore it is possible to estimate the position where the flexible link arm contacts with target environment. These features make it easy to realize the force/torque sensorless control. Second, the analytical comparison between the sensor-based approach and sensorless approach is described. These analyses show that sensorless approach is effective for a realization of stable force control in the flexible link arm system. The validity of the proposed method is confirmed in several experimental results.