Abstract: Stiffness and compliant motion characteristics of a manipulator are investigated, an evaluation model for coupling level of manipulating stiffness is proposed. Based on the analyses of time variety items in a Jacobian transformation matrix of manipulator’s kinematics, a mean square deviation based model of the items in Jacobi is constructed to describe characters of velocity transform relation between joint space and manipulating space, and an evaluation matrix for kinematics characters is presented. The meaning of those items on the cross is obviously, which describes the deviation range of linearity transform factor variation from average value, and coupling level of velocity transform between joint and manipulating space accordingly. A mean square deviation based model of the items in stiffness matrix in manipulation space is constructed, a capability index is presented to evaluate the coupling items in a linear transform between joint stiffness and manipulation stiffness. The velocity variety range and coupling level of manipulating stiffness for a kind of manipulator are computed and figured as the relation surfaces, an evaluation of the compliant motion performance is conducted with Matlab based software program. Kinematics optimization model of the manipulator mechanism is established and the kinematics is approximately decoupled at the optimized position in the design parameters space. The kinematics performance index and compliance motion performance index are evaluated with optimized kinematics parameters, the comparison data are listed as the optimized mechanism parameters vs. the original manipulator parameters. The optimization results of the manipulator compliance stiffness demonstrate that it is an effective analysis and evaluation method for manipulator design.

Key words: Compliance, Decoupling design, Forging manipulator, Parameter optimization, Stiffness