Modeling and simulation of a complex mechanical load using the multi-mass approach

The study and control of industrial electrical drive systems become a great challenge for scientists because of their complexity. In order to facilitate this task, the multi-mass model has been established recently. In fact, for certain industrial drive systems (rolling mills, compressors, etc.), it is necessary to take into consideration the non infinite rigidity of the mechanical link elements which causes mechanical vibrations. These vibrations are a major problem in industry because they harm the system dynamic performances and may end with the deterioration of the system structures. For this purpose, it is useful to dissociate the mechanical part into several masses in order to elaborate the correspondent multi-mass system. This paper presents a linearized model for complex mechanical load based on a two-mass system driven by a DC servomotor and connected together by an elastic link. The first step of the study consists of determining the appropriate transfer functions of the model. Then, linear regulation loops for velocity and load position control are elaborated using PI or PID regulators. As a final step, numerical simulations for different load torques are performed with Matlab/Simulink using the set of parameters of a drive system model. The simulation results show that the regulated system responds conveniently. Further more, these simulations are used to compare the dynamic performances of the different implemented control strategies.