Coordinated Insertion Control for Inclined Precision Assembly

This paper proposes a hybrid control strategy to coordinate inclined insertion for precision assembly, in order to increase the capability of dealing with disturbances. Precision assembly requires accurate manipulation, while due to perturbations, objects may be initiated with deviated posture and hold this deviation during insertion. To improve the assembly robustness to inclination, we develop a coordination structure: compensational motions for the mismatch between inclined posture and insertion direction by using kinematics and image Jacobian matrix methods; contact force acquisition to handle the indirect posture measurement between force sensor and inclined object, by taking advantage of the microimaging characteristics; and a hybrid coordinated insertion strategy to deal with the insufficient degree-of-freedom (DOF) allocation on each arm, applicable for assemblies in interference fit or clearance fit. Experiments are carried out to demonstrate the effectiveness of the proposed methods.