Robust compliant assembly automation using an industrial robot

Industrial robots used to perform assembly tasks are still a small portion of total robot sales each year. One of the main reasons is that it is difficult for conventional industrial robots to adjust to any sort of change. This paper describes the development and implementation of a robotic system to perform an assembly task of inserting a printed circuit board (PCB) into an edge connector socket using a robust control strategy. Because the task involves compliant manipulation in which a substantial force is needed to accomplish the insertion operation and there are some dynamic constraints from the environment, this task is quite challenging. A variable structure impedance control algorithm is used to perform the assembly process. The dynamic model of the robotic system is developed and the dynamic parameters are identified. Experiments were performed to validate the methodology. Experimental results shows that the robust control algorithm can deal with parameter uncertainties in the dynamic model, thus achieve better performance than the model based control method. An abnormal case is also investigated to demonstrate that the robust impedance control method can deal with the abnormal situation without damaging the system and part, while pure position control method may cause damage. This strategy can also be used in other similar assembly processes with compliant manipulation.