We design a fuzzy system to compensate the delays due to backlash nonlinearity. The fuzzy compensator is constructed from some common-sense rules. We consider the general case of the unknown backlash parameter and develop an adaptation algorithm to estimate the backlash parameter online. We prove that under certain conditions the fuzzy compensator with the adaptation algorithm guarantees that the backlash output converges to the desired trajectory. Simulation and hardware implementation results show that the fuzzy compensator is robust to the estimation errors in the backlash parameters. Application to an industrial CNC machine tool is described.

Workpiece localization, with novel applications such as workpiece setup, refixturing and dimensional inspections, is a problem of permanent importance in manufacturing. Using the popular least square formulation, several geometric algorithms have been developed for workpiece localization over the last few years. In this paper, we analyze and compare the performance of three localization algorithms based on the following criteria: (a) robustness with respect to variations in initial conditions; (b) accuracy of computed results; and (c) computational efficiency. We develop an approach for improving the robustness of the algorithms for workpieces with sculptured surfaces for which the region of convergence is typically small. Based on simulation results, we also discuss sensitivity of the algorithms with respect to the number of measurement points and give a lower bound on this number for recovering a Euclidean transformation with certain accuracy.

A deadzone compensator is designed for industrial positioning systems using a fuzzy logic (FL) controller. The classification property of FL systems makes them a natural candidate for the rejection of errors induced by the deadzone, which has regions in which it behaves differently. A tuning algorithm is given for the FL parameters, so that the deadzone compensation scheme becomes adaptive, guaranteeing small tracking errors and bounded parameter estimates. The adaptive FL deadzone compensator is implemented on an actual industrial CNC machine tool to show its efficacy.