Research On Sliding Mode Variable Structure Control Of Linear Compressor

Linear motor driving compressors have many advantages than traditional rotating motor driving compressors, since there is no crank and connecting rod mechanism which can change rotation movement into linear movement, they can change electric energy into linear motion mechanical energy directly, and the compressor mechanical efficiency increased greatly, simplified mechanical structure and reduced the energy transmission link. Because of linear compressor have characteristics of small in size, compact structure, low energy consumption and high energy efficiency, in current society which the environmental requirements are higher and higher, the application prospect of linear compressor will be very broad.Based on the analysis of the current linear compressor control method, focus on the speed of piston unstable, resistance to disturbance weak and control inaccurate, research suitable control intelligence method for linear compressor piston speed.Based on analyzing the moving magnet linear compressor internal structure and working principle, and through equivalent magnetic circuit model, this thesis deduces the motor magnetic circuit and electromagnetic thrust, establishes electromagnetic system mathematical model; meanwhile, the motor machinery system is equivalent to a single quality single-degree-of-freedom spring damping vibration system, and establishes mechanical system model, completes the overall mathematical model of linear compressor.Based on the controlled plant mathematical model, in order to improve the system performance and anti-interference ability, this thesis uses traditional PID control, by using two engineering design method to design PID controller, and uses Simulink to analysis the simulation curve. Under the condition of existing external constant value disturbance in system, the response curve will wave and recover slowly, indicating that the traditional PID controller’s robustness is not strong; this thesis introduces the sliding mode variable structure control theory, and designs a sliding mode variable structure controller. Through the simulation analysis, the anti-interference ability of the system in certain scope has been greatly improved, and the response to disturbance is insensitive, but the system exists chattering phenomena; To restrain the influence of chattering phenomena, this thesis studies the fuzzy control theory, combines the fuzzy control and sliding mode variable structure control, and designs a fuzzy sliding mode controller, through the adjustment of system’s parameters, the anti-interference ability of the system increases, and the chattering phenomena also has been restrained, making the system achieving a satisfactory static and dynamic response characteristics.