Modeling of assembly operations for robot compliance control

Abstract

The assembly modeling system is proposed to automatically generate the compliance control strategies for generic assembly operations in a systematic way. Based on the unique geometric relationship between two mating parts, twenty eight constraint configurations are identified. Each constraint configuration is represented by combinations of six motion components $T\sb xT\sb yT\sb zR\sb xR\sb yR\sb z$ before, during and after the assembly. Furthermore, due to the geometric similarities, the above twenty eight constraint configurations can be classified into seventeen unique part mating types. To determine the proper part mating types for unknown assembly operations, a coding system called SACS is developed. This coding system provides a mechanism with which various unknown assembly operations can be identified. From the input CAD descriptions about the assembly operation, the coding system determines the part mating type, and then the corresponding SACS code is assigned. Using the SACS code, corresponding constraint subgoals can be obtained from the formal part mating model. These subgoals in turn provide a set of compliance control strategies and terminating configurations for the desired assembly operation. To counterbalance incorrect force conditions during the execution of compliance control strategies, error correction rules are proposed. Algorithms for the recognition of the part mating type, the generation of compliance control strategies, and the corrective action are also included. The generated active compliance control strategies can then be used for robot compliance control.