H∞ robust two-degree-of-freedom control for high rise elevator driven by permanent magnet linear synchronous motor

The vertical motion control system and robust two-degree-of-freedom (2DOF) control for high rise/high speed elevators were discussed. The control aim is to realize robust tracking and re-leveling and let the system have good robustness for uncertainties under desirable control performances. A kind of robust 2DOF control method is proposed for elevators on the basis of vertical motion control. The proposed method can effectively reject the effect of parameter variation on system performances. And the good tracking, disturbance rejection, robustness and high precision re-leveling characteristics are achieved. Firstly, the speed controller design is converted into a standard H_infin control problem. Secondly, with the help of linear matrix inequality (LMI) approach, an output feedback suboptimal H_infin controller is obtained. Finally, an H_infin optimal controller is designed by solving a convex optimization problem so as to guarantee system robustness. The simulation results show that the present method is effective.