In the assembly process using industrial robots, many difficulties stem from the fact that assembly operation is impossible or the parts to be assembled can be damaged by reaction forces due to even a little misalignment during part mating and that robots can not adapt themselves to some unexpected phenomena in assembly.
In this paper a flexible and sensible wrist is redesigned and manufactured with the consideration of practical applicabilities in industry, and the control algorithm for the force feedback controller using the wrist is developed. The flexibility of the wrist and the control algorithm were evaluated both analytically and experimentally in actual inserting process by a computer interfaced milling machine. The results show that without the use of the feedback control, the wrist is capable of doing inserting operation under the easy condition of assembly. When the condition of assembly is hard the assembly operation becomes very difficult. But with the force feedback control by the algorithm, insertion can be performed with much less maximum inserting force. The reaction forces due to only the position error can be controlled near to zero by the position control of the wrist. Also the algorithm can extend the range of an allowable initial position error and protect assembly system from dangerous situations.