Feedback control of systems with parasitic effects

The state-dependent algebraic Riccati equation (SDARE) method is used for the design of control systems with the parasitic effects of friction and backlash. In the case of friction, the SDARE method results in treating the friction as an exogenous variable for which the linear quadratic control theory has already been developed. The effect of backlash is treated by representing the backlash nonlinearity by a two-level gain function, which leads to a control law that switches between two sets of gains. The performance of a hypothetical control system for a plant comprising a belt-driven robot arm was simulated and it was found that the proposed techniques promise considerably improvement in system performance.