Modeling machine tool feed servo drives using simulation techniques to predict performance

A method is described for predicting servo drive performance for a machine tool having the nonlinearities of backlash and stiction (stick-slip) in the machine system or servo plant. The simulation of these nonlinearities produces computed servo performance that agrees with what actually occurs on a machine tool feed axis when backlash or stiction is present. The transient response is used for the analysis. This type of analysis closely agrees with what an observer would see on a machine in response to a step input in position or velocity. The servo simulation techniques are used to construct a very accurate model of the servo drive, allowing the effect on performance of changing the drive parameters such as load inertia, backlash, stiction, viscous friction, load thrust, current limit, servo loop gains, machine resonance, and acceleration to be observed. Assuming the model is correct, the simulation program allows the machine designer to observe the feed drive performance without having the drive available. This simulation procedure makes it possible to anticipate machine design problems affecting servo performance and correct them before the machine is built.<>