High precision force control by multi-sensor based disturbance observer

Motion control has been widely used in industry applications. One of the key technologies of motion control is a disturbance observer, which estimates a disturbance torque of a motion system and realizes a robust acceleration control. The disturbance observer can observe and suppress the disturbance torque within its bandwidth. Recent motion systems begin to spread in the society and they are required to have ability to contact with unknown environment. Such a haptic motion requires much wider bandwidth. However, since the conventional disturbance observer attains the acceleration information by the second order derivative of position response, the bandwidth is limited due to the derivative noise. This paper proposes a novel structure of a disturbance observer. An acceleration sensor is implemented to enlarge the bandwidth in the proposed multi-sensor based disturbance observer (MSDO). Thus, control performance of the MSDO is superior to the conventional one. In this paper, the MSDO is applied to force control and the viability of the proposed method is confirmed by fast Fourier transformation (FFT) analyses.