| Summary: | 碩士 === 國立臺北科技大學 === 機電整合研究所 === 99 === Experimental study on friction model identification and feedforward compensation.The characteristics of static friction in a mechanical system are investigated through the construction of friction compensation lookup tables based on slow-velocity friction experiments in order to develop improved friction models for computer numerical control (CNC) machining. Friction in the feed drive servomechanisms of CNC milling machines can degrade the accuracy of tool motion. Although friction compensation has been applied with good results in CNC tool motion control, the simplified model of friction used for such schemes limits the ultimate motion accuracy of feed drives. As an alternative to the time-consuming and tedious breakaway experiments that are generally used to identify static friction in a mechanical system, an experimental methodology based on slow-velocity measurements and a friction compensation lookup table is proposed. Analysis of the measured friction using a spatial fast Fourier transformation algorithm shows the feasibility of the experiments for constructing accurate friction models. Integration of the friction compensation lookup table with a velocity-dependent friction model reduces the adverse effects induced by both static and velocity-dependent friction. On this basis, an integrated friction model that considers the position dependence of friction developed for friction compensation, and a feedforward friction compensation structure is presented for the control of motion in mechanical systems. Experiments and motion tests using an axial servomechanism illustrate the feasibility of the proposed friction compensation method.
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