Optimal actuator stiffness distribution for robotic manipulators based on local dynamic criteria

Current industrial robots deflect as much as 25 times their specified accuracy due to their capacity load. This paper presents the local optimization criteria for the distribution of actuator stiffness (or compliance) of a given manipulator configuration to enhance the overall stiffness of the structure and to guarantee a specified level of precision under a known magnitude of machining load resulting from drilling, routing, riveting, etc. Position dependent kinematic influence coefficients [2] form a convenient basis for the compliance matrix for demonstration of the role of significant physical parameters and efficient computation in the analysis and design process. Specific examples dealing with optimal distribution of actuator compliance are presented. The techniques developed in this paper and the previous work [6,7] can greatly reduce the design cycle time for accurate, reliable manipulators, and makes adjustment of the distribution of system parameters to enhance controllability more feasible, especially when precision control under external disturbance is required.