Sensor-based force decouple controller design of macro–mini manipulator

Abstract

A robotic polishing system includes a force-controlled end-effector (mini manipulator) and a position-controlled industrial robot (macro manipulator). This combination mode has a fast response and a large workspace. However, the force-controlled axis component of the macro motions and the geometric of the workpiece surfaces will affect the contact force response rate and tracking accuracy due to the coupling dynamics between the macro and mini, limiting system performance. A new dynamic decoupling method employing dual force sensors (DFSs) is proposed to address these problems. One of the force sensors installed between the endpoint of the macro and the fixed platform of the mini realizes the dynamic decoupling of the macro and mini. The other one is added at the endpoint of the mini to obtain the interaction force in contact with the environment and feed it back to the control loop. When the disturbances produced by the macro trajectories and the uncertainties coming from the workpiece are introduced into the system, the proposed method can improve force response rate and tracking accuracy without knowing the dynamic models and parameters of the macro and the geometric of the workpiece surface. Several experiments are carried out under various conditions. Experimental results indicate that the contact force response rate and tracking error of DFSs are better than those of the conventional force-controlled and impedance matching methods, proving the proposed method’s effectiveness. In addition, the last comparison experiment verifies that the DFSs method applies to different kinds of end-effectors with various dynamics. • This paper proposes a new dynamic decoupling method based on force sensors. • It can obtain the coupling force to realize dynamic decoupling regardless of models. • It can reduce the disturbance effects of the macro and the workpiece on the force. • The proposed method can improve contact force response rate and tracking accuracy.