Intelligent robotic machining with force control.

摘要

The research deals with robot force control for material removal applications. Critical issues and methodologies to improve robotic machining performance with industrial robots were introduced. For existing robotic systems, the inherent lower stiffness of articulated robots resulted in a lower productivity, unacceptable quality and instability of the machining process. In this study, an effective force control strategy, including material removal rate (MRR) control and real-time deformation compensation, was initiated and implemented on industry robots.; This research was the first attempt to address robotic machining process from both robotic control and machining process point of view. The designed robot force controller functioned as an implicit hybrid position/force controller, which can control the process force in a certain direction while maintaining the position accuracy in other directions.; An adaptive PI controller was developed to regulate the machining force considering the force model nonlinearities. As a result, a much higher feed speed, instead of a conservative feed speed based on maximal depth-of-cut and width-of-cut position, can be adopted. Based on the robot stiffness model, a real-time deformation compensation algorithm was created to achieve better surface finish. Experimental results showed that higher productivity as well as better surface accuracy can be achieved, indicating a promising and practical use of industrial robots for machining applications that was not possible at present.; Chatter phenomena in robotic machining process were also investigated. The robot structure and cutting process were treated as a closed loop system. Theoretical analysis and experimental results showed that due to the coupling of robot structure and inherent low structure stiffness, the mode coupling chatter was very often the most stringent limitation for the robotic machining process. Guidelines for process configuration and cutting parameter selection were proposed to avoid vibration.