Dual RST-control of an inverted pendulum with Simulink S-functions implementation

This paper has a two-fold pedagogical goal. First it describes the use of RST controllers in a cascaded-loop structure. Second it gives the student the tools to design such a control structure for a real-time application and to implement it on a real experimental setup, all in one single lab session. The dual-loop cascaded control involving two discrete-time RST-controllers is applied to an inverted pendulum. The inner loop stabilizes the angle of the pendulum around its unstable (upwards) equilibrium, whereas the outer loop controls the cart position by giving to the inner loop the proper angle reference required to make the cart move on its rail. The burden of programming these two control loops for a real-time experiment is simplified for the students by the use of S-functions in a SIMULINK diagram. The writing of such S-functions for a real-time use alleviates indeed his programming task while obliging him to concentrate on the real-time control task itself. This control scheme is then applied directly to the pendulum by means of the Real Time Windows Target toolbox from MATLAB.