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The positioning accuracy problem of robot manipulators has long been one of the principal concerns of robot design and control. In a previous work, a linear model that described the robot positioning accuracy due to kinematic errors was developed. However, the previous work considered only the small errors by ignoring the higher order terms and did not address the special case of two consecutive parallel joints. In this work a more detailed model is given that applies to consecutive parallel joints and includes the second-order terms. By comparing the results of the linear model and the second-order model, the accuracy of the linear model can be evaluated for a given manipulator and range of input kinematic errors. The error envelopes obtained using the linear model and the developed second order model for the Puma 560 are plotted and compared for various sets of input kinematic errors. A comparison of the computation complexity for the two models is also given.
Date of Publication: Sep 1986