Nonlinear dynamics in servo positioning loops

This paper describes a novel dynamic model for servo positioning systems. Nonlinear representations of friction, backlash, controllers and process dynamics are integrated in a model having a closed loop configuration where unwanted oscillations such as hunting and resonant frequencies are reproduced. A case of study consisting in a gun mount driven by hydraulic actuators is analyzed. Real data is used for identification and validation of the mathematical representation. Empirical static friction values are used for tuning the model at low speeds. An excellent matching is accomplished between the calibrated model and the real response. The model also reproduces the dependence of resonant frequencies to rotating speed that is generally found in this type of systems.