| The competition among the advanced industrial countries in the world is mainly on the manufacturing technology. Because sixty-percent to ninety-percent products in the industrial field such as manufacturing industry,automobile industry,aeronautics and astronautics industry are die and mold, all the industrial countries pay much attention to the industry of die and mold. However, at present the machining depending on the handwork of skilled mechanists has such drawbacks as wasting a lot of energy and time and being hard to maintain consistency of the surface quality of die and mold, we gradually find that the automation of this machining can bring us less cost and better machining quality, at the same time, the robot's structure and performance have all the advantages of automatic apparatus, so much work being carried out to replace the manual task by a robotic polishing system for die and mold with free-form surfaces is prospective.When machining die and mold with free-form surfaces, We not only require the movement of the technical apparatus can guarantee the polishing tool finish machining the workpiece according to the scheduled lines or the technological requirement, but also require the force between the polishing tool and the workpiece is compliant to the change of curvature radius of die and mold with free-form surfaces. So the study on the compliant control problems of uncertain robot has very important theoretical and practical meanings.This paper establishes a system for sampling polishing compression force as is shown in Fig.1. In this EDM polishing system, a computer controls the motion and the attitude of a multi-joint robot based on equations of the polished surfaces, and the robot makes the polishing tool move along the surface of the workpiece and carry out polishing. With the elastic polishing tool compensating for its motion errors to some extent, the robot is able to imitate the polishing machinist's actions and to polish free-form surfaces smoothly and reliably. An RV-M1 industrial robot, a force sensor of three degrees of freedom and other devices form the integrated robotic polishing system. This sensor and an IBM PC/586 are interfaced with the RV-M1 controller for communication and control.Fig.1. A robotic polishing systemBefore polishing, we calibrate the force sensors of y direction and z direction separately and the force calibrating curves are shown in Fig.2, we can see from Fig.2 that the linearity of the dynamometers are fine. So for two-dimensional curved surfaces, the polishing forces can be obtained after sampling, which is the basis for the force control in robotic polishing.Based on the movement and control of polishing robot, this paper studies the movement programming method for polishing tool, introduces the principle and characteristics of both transverse movement programming method and longitudinal movement programming method systematically, demonstrates that, transverse movement programming makes polishing tool move in a 3-D space of two line movements and a writhe movement, longitudinal movement programming makes polishing tool move in a 2-D space of one line movements and a writhe movement, so longitudinal movement programming needs less number of degree of freedom, and then, reaches the conclusion that the performance of longitudinal movement programming method is better than that of transverse movement programming method in polishing free-form surfaces by robot.In the course of polishing such special objects as die and mold with free-form surfaces, we not only assure the movement of the polishing tool is according to the scheduled lines, but guarantee the polishing tool keep specific posture and stable pressure when machining. However, the robot is a very complicated non-linear system with many inputs and outputs, it has time-variable,strong coupling and non-linear dynamic characteristic, so the control of the robot is very complicated and it is difficult to solve the problem completely with the existing theo...
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