Implementation of RST controllers for a flexible servo considering practical limitations

In positioning systems, complex control structures are necessary to properly reject disturbances while correctly following reference laws. However, the higher the dynamics, the more important flexion problems are. In the paper, the authors focus on the control of a system with elasticity between the actuator and the load. Flexible servo tuning methods have been widely presented in the literature. This paper only considers the case when limitations occur on the control variable. The approach is based on poles and zeros placement design. It compares the behaviour of different structures of RST controllers in a view of practical implementation (theoretical R, S, T structure, S/R controller and (T-S)/R feedforward term, controller with the addition of an integration antiwindup loop, controller with fully controlled state in the limitation mode)