| Assembly robot has been widely used in recently years.Precision is a significant technical characterization of assembly robot, which is the robot's capability of precisely placing the end-effector at the predefined pose, which not only including position and carriage precision but also including position and carriage repeatability. As a summary of the SCARA assembly robot design, three aspects are including in this paper,.First of all, the paper presented the whole system of the SCARA assembly robot and the organization of the SCARA assembly robot in detail.Secondly, a error model for robots at large has been set up based on Denavit-Hartenberg parameters in the paper. Because the DH parameters is abstract and isn't convenient for error control, so utilizing space decentralization translate the joint clearance into DH parameters error. With the error model, we deduce a DH parameters error calibrating model based on distance error which avoid the transition between the robot coordinate and the survey coordinate. Thirdly, Basing on the result of coordinate, we use two methods to increase the precision of the robot.: the directly modifying method and the compensating method .Finally, we make use of the matrix principium optimized distribute the tolerance of the DH parameters.In the end,We analysed the SCARA assembly robot which we designed by programming emulator with the kinematics equation and the above theory, which including several step. First step is analysing and comparing the markedness of every parameter error, which affects the robot precision. Second step is distributing the optimum tolerance of the DH parameters. Then basing on the analyse of the markedness and the optimum tolerance, we adjust the tolerance to convenient for manufacture. Third step is using modifying method and the compensating method to increase the SCARA assembly robot precision. The emulator testified that the error model and the correlative theory is legitimacy. |
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