Research On Linear Motion Of Magnetic Supporting Based On Sliding-mode Control

Magnetic suspension has been paid more and more attention because of its many merits such as no mechanical contact, no wear, low power loss, no need of lubrication and long service life, etc. The performance of magnetic suspension is determined mainly by its control system. The performance of Controller will have a direct impact on the dynamic performance of system. Most control systems in use today are linear control systems. The most common type is the PID Controller, which is adequate in many applications. This article take maglev coasters as the research object, the author works on the study of sliding mode variable structure control which is a kind of nonlinear controller. If linear control systems are so well understood and adequate, then why do we use non-linear control systems? According to this problem, this article makes a comparative study on the dynamic performance of system under the PID and sliding mode control.Firstly, this dissertation introduces the structural design of coaster simply, and analyzes the supporting principles of coaster Besides this, build the mathematical model of coaster based on it. Exactly check the controllability and observation of system by establishing state equation.Secondly, according the definition of sliding model control, the author proposes two key issues which should be paid attention when we design the sliding model controller-switching function and design of control law. Furthermore, according to the chattering problem which exists in sliding model control, the author brings up reaching law method. The chattering not only affects the accuracy and increase the capacity of consumption, even such high-frequency input very easily give rise to systematic unmolded characteristics, thereby undermining the performance of the system. This paper based on the magnetic levitation coasters design a kind of sliding mode controller based on exponential rate reaching law, which is simple in design, easy to implement.Thirdly, according to the Mathematical model of the system, the author make a dynamic simulations contrast of control system by using matlab/simulink tool. The results indicate system can get much better dynamic performances with the sliding mode controller compared with the traditional PID controller. And it avoids repeatedly selecting the three parameters under PID control. However, the superiority of the sliding mode control embodies more obvious in the complex working conditions. For example, when the parameters of the controlled system will change as the working conditions and components aging, the existence of noise and interference and so on., sliding mode control showed more robust in this case. This is verified by simulation.