A force control structure based on the concept of virtual plant

In force control applications where a robot end-effector is required to interact with the environment or the workpiece, the dynamic of the environment plays an important role. The environment dynamic may influence the performance of the controlled system, especially the performance in transient period. In order to avoid tuning the controller constantly with the changing environment, a robust control algorithm is proposed. A virtual stiffness is implemented in parallel with the actual environmental stiffness and forms a “virtual plant”. In this paper, different algorithms to control the virtual plant are proposed. Simulation results show an improved performance in reducing the influence of the changing environmental stiffness, as well as the ability of rejecting disturbance.