Liu Chun-fang

Design of second-order sliding mode controller for Electromagnetic Levitation Grip used in CNC

A novel second-order sliding model controller aiming at the inherent chattering of classical sliding mode control for high-precision air gap control of Electromagnetic Levitation Grip used in CNC(Computerized Numerical Control) was proposed, and the control strategies based on super-twisting algorithm was designed. Electromagnetic Levitation Grip is a very complex system with real parameter uncertainties and external disturbances in the process of air gap control. This method can eliminate the chattering which may excite high frequency chattering, keep the robustness of system, and effectively improve the dynamic response of system. Simulation results demonstrate that the design of Second-order sliding mode controller can achieve the better stability of suspension, strong immunity and high stiffness.

A Novel DSP Based Current Controller with Fuzzy Variable-Band hysteresis for Active Power Filters

Conventional hysteresis current controller with fixed-band for active power filter (APF) has a high maximum switching frequency (MSF). To limit the MSF within the limit of inverter switches, a novel fuzzy hysteresis band current controller for active power filter is proposed in this paper. The band height, based on fuzzy control principle, is changed with the value of the error current and the rate of change of the error current, consequently the switching frequency is controllable. The fuzzy hysteresis band current control and harmonics compensation algorithm are both based on digital signal processor (DSP), which reduce the analogue circuitry and enhances the systems immunity to noise. The simulation results by MATLAB show that control strategy proposed is feasible

Sliding mode control of cnc electromagnetic levitation system based on feedback linearization

The levitation rigidity for the levitated crossbeam of the gantry numerical control machine tool which can eliminate friction and increase machining precision is discussed. The feedback linearization and sliding mode control methods are presented in this paper in order to achieve steady levitation. The nonlinear electromagnetic levitation system is transformed into linear system by using feedback linearization method. The sliding mode control method is adopted for improving the robustness of the levitation system. Simulation results show that the system has more powerful ability of suppressing disturbance and high rigidity compared with that using conventional PI control method.

Robust Loop-shaping Power Oscillation Damping Control of FACTS Devices in Large Power Systems

This paper presents the FACTS robust loop-shaping Power Oscillation Damping (POD) controller design in large power systems. By applying the model reduction and modern robust loop-shaping control technique, the FACTS robust loop-shaping controller is realized. This robust loop-shaping controller exploits the advantages of both conventional loop-shaping and modern H∞robust control techniques. Moreover, it is a decentralized approach and suitable for FACTS controller design in real large power systems. The performance of the proposed control has fulfilled the robust stability and robust performance criteria. Furthermore, the simulation has proved that using the proposed controller, the power oscillation damping behavior is also satisfactory under large disturbances.

Simulation of robot localization based on virtual sensors

A flexible simulation frame based on concept of component is presented. An indoor robots localization simulation environment based on virtual sensors RoboSimer is built with OpenGL. The parameters here are easily adjusted and controlled by customs and the simulation module is easy to integrate. It can integrate any sensors, environment and robot shape into the simulation software. The interfaces of simulation software are coincided with the real hardware platform. It provides a convenient condition for the further study on robot localization.

Dynamic robust compensation based fuzzy-coordinated low speed control of NC gantry-moving type milling machining centers

The synchrodrive is the important part in the gantry moving type milling machining centers. First, robust compensation are designed for linear servo systems with parameter variations, friction disturbance and no linearity at low speed. Then, a synchronization control strategy is presented based on fuzzy-coordinated control according to the double position synchronized drive of numerical control (NC) gantry-moving type milling machining centers. By the designed fuzzy-coordinated controller between the two synchro-driven passages, the output error between two synchro-driven systems is overcome. And the purpose of synchronization control could be realized. The simulation results show that the proposed scheme have both high synchronization accurate and strong robustness, and while low speed the demand of synchro-driven of NC machining centers can be satisfied.