Research on the Suspension Rigidity Control of the Movable Beam Used in Machining Centre with Fixed Gantry

　　Research on the Suspension Rigidity Control of the Movable Beam Used in Machining Centre with Fixed Gantry
　　This thesis is supported by Liaoning province educational department’s project "The Research on Electromagnetic suspension Linear Motor and Its Control Strategy in Machine Tools Feeding system" and Shenyang City NSF’s project "The Research on Drive Ball Neodymium Magnets System of Electromagnetic suspension Linear Motor in Machine Tools Feeding system". Advising the practical characteristics of the machining centre with fixed gantry, and aiming at that the movable beam requires more strictly on suspension rigidity than the maglev train, this thesis does research mainly on the control algorithms of electromagnetic suspension system to improve the maglev rigidity.
　　As hybrid magnets combined with permanent material and electrical magnet can solve the problem that the traditional electromagnetic suspension system consumes too much power, this thesis adopts the hybrid electromagnetic suspension technology.Firstly, in order to resolve the rigidity effect caused by the current changes of electromagnet coils, double loop control system is adopted. Then the thesis introduces some common controllers, and chooses PI controller after comparing them. The current inner loop not only improves the dynamic characteristics, but also offsets uncertainty and change. The main work of the thesis is to choose and design outer loop controller by analyzing characteristics of traditional PID algorithm and Fuzzy algorithm, Fuzzy-PID algorithm is proposed. http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php    The composted control model based on the conventional PID regulator employs fuzzy reasoning and accomplishes PID parameters self-tuning according to different error and change rate of error, thus perfect performance can be reached. Considering the tediousness of determination of fuzzy rules and other parameters of Fuzzy-PID controller, the thesis adopts genetic algorithm (hereafter GA) to optimize those rules and parameters.At last, this thesis simulates the above control systems, and analyzes the feasibility and advantage of GA fuzzy-PID controller according to the practical applications. The simulation results have proved that the Fuzzy-PID controller not only improves the suspension rigidity of hybrid magnets system, but also offsets the error, so it is suitable for large-scale machine tool’s requirements, and the optimal effect of GA is perfect, and GA makes the determination of Fuzzy-PID controller’s Parameters more systematical and more scientific.