Finish Processing Support System via Grinding Force Control Based on Hand Stiffness Estimation

Compared with machining by automation, handwork is suitable for high-variety low-volume manufacturing, because such manufacturing requires a lower cost and shorter lead time. However, high-concentration machining should be implemented in handwork. Furthermore, any mistake generated by disturbance from tool rotation results in useless products and wasted materials. Our goal was to develop a finish machining support system that can realize high-accuracy machining in the case of tool rotational direction orthogonal to the feed direction without any machining mistakes. Specifically, in this study we developed a fixture-type machining support robot with a parallel link system to achieve good usability and highly accurate machining. We estimate the operator’s hand stiffness from the machining force and end effector position during grinding, and then the grinding force is controlled based on estimation of the worker’s hand stiffness. As a result, the influence of grinding force on the worker’s hand is suppressed, and the problems with machining accuracy in handwork are lessened. Finally, the effectiveness of the proposed method is shown by grinding experiments.