Analysis And Design Of Magnetic Levitation Control System

Magnetic levitation is a type of automatic control technique using magnetic force to let an object stay in a contactless levitation state. It belongs to mechanotronics and has the characteristics of zero friction, zero wear, long service life, low power consumption, low noise, etc. Within more than half a century, magnetic levitation technique is rapidly developed and widely applied. In this dissertation, a mathematical model of system is established on the basis of the experimental facility of unidirection magnetic levitation ball manufactured by Googol company, a variable parameter PID controller and two kinds of single neuron PID controllers are designed respectively based on traditional PID controller, and a robust Hx controller is also designed according to system uncertainties.First of all, the operating principle and structure of magnetic levitation system are analyzed; a nonlinear system model is built and linearized respectively by a linearization method expanded on the basis of balance point and a direct feedback linearization method so as to obtain two linear models. The research object of the thesis is the linear model expanded on the basis of balance point.On the basis of traditional PID controller, a variable parameter PID controller is designed according to a certain parameter variation rule. Because artificial neurons have the characteristics of self-learning capability, self-adaptive capability, simple structure, easy calculation, etc., a single neuron PID controller based on the supervised Hebb learning rule is designed. In order to limit control quantity of single neuron controller, a quadratic performance index is introduced during adjustment of weighting coefficients, and a single neuron PID controller based on the quadratic performance index is also designed. Simulation results indicate that, compared with traditional PID controller, both the variable parameter PID controller and the single neuron PID controllers designed here have better control effect, improved dynamic performance of system and enhanced adaptability.The mixed sensitivity method of H∞control theory is utilized, appropriate weighting functions are selected in accordance with a certain selection principle of weighting functions, and finally, a H∞controller which enables the system to be stable and have good robustness is designed. Through computer simulation, the control effect of the H∞controller is compared with that of the previously designed PID controllers. Simulation results show that the ball levitates stably, dynamic performance of system is further improved, and anti-jamming capability is also enhanced.