Force Disturbance Observer-based Force Control for Compliant Interaction with Dynamic Environment

Disturbances are one of the major challenges that should be dealt with when designing high performance force control systems for robots that interact with unknown environments. To achieve high performance dynamic interaction, this paper presents a robust force control system that implements a force disturbance observer (FDOB). Dynamic compliance with the environment is greatly improved with this control technique. The whole force control structure consists of a servo system with a force sensor, the proposed FDOB, feedforward and feedback controllers, and the low-pass filter for attenuating measurement noises of the force sensor feedback signal. The nominal model of the proposed FDOB is obtained by nonparametric system identification method. The FDOB then estimates disturbances by utilizing the motor torque and force sensor measurement signals as its inputs. Theoretical analyses of the FDOB and the overall force control system are conducted. To validate the proposed control structure, experiments are conducted while considering various scenarios from where it is found out that it shows superior performance over the conventional force control method.