Dynamic optimization of speed pattern for efficiency improvement in elevator systems

Elevator systems have become an essential part of the current urban society. This paper tries to minimize the losses in an elevator system, thereby increasing the overall system efficiency. The system considered in this paper uses induction machine to drive the elevator. The losses in induction machine are dependent on the rotor speed so, they are minimized by optimizing the instantaneous values of rotor speed. Since rotor speed varies with time, a dynamic optimization technique has to be used. A loss equation is formulated and it is minimized by Pontryagin´s Minimum Principle with state variable constraints. The methodology followed and equations obtained are discussed in different sections of this paper. The initial analysis and simulation results are presented in the paper.