Research On Active Magnetic Suspension Bearings

Now,high-speed machine tool is an important development direction of modernmanufacturing technology .The high-speed machine tool requires the bearing has excellentperformance. Generally, the bearing using for high-speed machine tool are hydrostaticbearings, air bearings, ceramic bearings and magnetic bearings. The magnetic bearings areusing the electromagnetic force to suspend the rotating parts in space, and it has someadvantages, such as no mechanical friction, no lubrication, small vibration, and adjustablestiffness damping. Therefore, the magnetic suspension bearings have attracted muchattention. Magnetic bearings are electromechanical products whose performance isdetermined by its control system. With development of computer technology, automaticcontrol technology, microelectronics technology, its applications have become morewidespread.This paper describes the development of magnetic bearings and its main applications.Then basing on the basic principle of magnetic bearings, magnetic bearings are describedon the detail work process, the using sensors, controllers and power amplifiers. Accordingto the magnetic circuit analysis, we obtain magnetic bearing capacity formula. Using theformula, the structure of the axial and radial magnetic bearings, parameterized respectively.According to the application example of CK520 vertical NC lathe, and we propose anoptimization method for the radial magnetic bearings, optimal calculation are carried out.Taking into account the complexity of the five degrees of freedom model, thisresearch will decoupling control for a single degree of freedom (axial) and a four degreeof freedom (radial) control discussed respectively. In based of the detailed analysis ofaxial magnetic bearings, we establish a mathematical model of the axial magnetic bearing.Through linear magnetic force, the system's transfer function is derived, and the numericalsimulations are carried out using SIMULINK and PID control system, the responsecharacteristics of the vertical magnetic suspension bearing are examined. The four degreesof freedom model of the radial magnetic suspension bearings are analyzed, and the mathematical model and the state-apace equation are established. Finally through thedistributed control system and centralized control system simulation, and the simulationresults meet the requirements. It explains that decentralized control is feasible, and it'svaluable for the follow-up on magnetic bearings.