LuGre-Model-Based Friction Compensation in Direct-Drive Inertially Stabilized Platforms

A Trajectory tracking problem for direct-drive inertially stabilized platforms suffered from nonlinear friction was considered in this paper. The dynamic characteristics of the system was study. A parameter identification method for LuGre model based on multilevel coordinate search algorithm was presented. Furthermore, nonlinear friction observer was designed to estimate the unmeasurable internal state of LuGre model. The comparative trajectory tracking experiments were conducted on a simulator of direct-drive systems between the single proportional–derivative (PD) control and the PD with LuGre model-based compensation. The experimental results revealed that the control scheme based on LuGre-model-based friction compensation reduced 3δ tracking error to 0.2mrad which is improved almost 66.7% compared with the PD control. At last, the ‘fake non-dissipativity phenomenon’ of LuGre in simulation and the digital implementation of LuGre friction compensation were discussed.