Huachun Wu

Fuzzy Control of a Semi-active Multiple Degree-of-freedom Vibration Isolation System

Semi-active isolation systems fill the gap between passive and active systems, delivering the versatility and adaptability of fully active systems, by expending a small amount of energy to change system parameters such as stiffness and damping. Magnetic suspension vibration isolation provides an excellent active isolation technology, and has shown useful characteristics including noncontact isolation, fast response, high reliability and long lifespan. However, because it is highly nonlinear and time variant, the control of magnetic suspension vibration isolation is an area that still requires further exploration. This paper presents a fuzzy control algorithm for a semi-active multi-degree-of-freedom vibration system. The fuzzy control is based on the minimization of the weighted sum of squared output forces. The output force response of the fuzzy, PID control semi-active vibration isolation system and passive system under the same excitation are simulated. The simulation results show that the fuzzy control system has much better performance in vibration isolation. An experimental platform is developed to test the performance of the magnetic suspension vibration isolation system and the proposed fuzzy control algorithm. The experimental results are found to be in good agreement with simulation.

Research on Forces and Dynamics of Maglev Wind Turbine Generator

Maglev wind turbine generator (MWTG) technology has been widely studied due to its low loss, low maintenance cost, and high reliability. However, the dynamics of the magnetic bearing system differ fromthe those of the traditional mechanical bearing system. A horizontal axial MWTG supported with a permanent magnetic bearing is designed in this research and the radial forces and the natural frequencies of the rotor system are studied. The results show that the generatorhas a cyclical magnetic forceand an unreasonable bearing stiffness may mean that the rotor system needs to work in the resonance region; the bearing stiffness is the key factor to avoid this problem. This is the main rule of the bearing stiffness design in the MWTG, and this rule can also be used in other maglev permanent magnet motors.

Co-simulation of magnetic suspended rotor system: Research and application

Based on the electromagnetic model of magnetic suspended rotor system and virtual prototyping technique, we propose a co-simulation model of ADAMS and MATLAB/Simulink for the active magnetic bearing system. The suspending simulation experiments are given on the proposed model. If both left and right radical magnetic bearing control systems have the same control parameters, simulations show that the axis of the rotor is not horizontal. This coupling can be reduced or eliminated by adjusting system control parameters. The proposed co-simulation can play a good help for parameter tuning and dynamic analysis of magnetic suspended rotor control system, and its an effective tool for the research and design of magnetic suspended rotor system.

Study on structural optimization design and cascade PID control of maglev actuator for active vibration isolation system

In view of the nonlinear output characteristics of actuators, and due to necessary large strokes for low-frequency vibration isolation platforms in microgravity environment, a method for structural optimization design and cascade PID control of maglev actuators was put forward based on the principle of Lorentz force. Furthermore, the method was utilized to design a magnetic circuit in accordance with the self-demagnetization effect and to multi-objectively optimize the structure parameters of a coil. A mathematical model was established of the remarkably nonlinear output force, due to the nonuniform magnetic fields to optimize its output force and current, so that the time-varying output requirements of controllers may be satisfied. System identification was performed to obtain the mathematical model of its control channel and design cascade PID controllers. This method was applied to lower the phase lag and equivalent time constant of a closed secondary circuit system so that not only the system stability and response rate may be improved, but also the growth of the gain of the controller may lead to growth of the damped natural frequency of the cascade control system; thus, the system settling time may fall and the system control quality may be improved. Simulation was also carried out to the cascade PID control corresponding to the mathematical model so that the cascade PID controller may have a relatively good control effect on disturbing acceleration signals. Experiments were carried out to cascade PID control of maglev actuators to further verify vibration control performances. Comparisons of the measured and simulated acceleration transmissibility data are basically consistent within the band 1–25 Hz. Measured and simulated results indicate that application of the cascade PID control method may attenuate the control object in the range −22.522 to −2.189 dB within the band 1–25 Hz and perform effective vibration control.

STRUCTURAL DESIGN AND NUMERICAL SIMULATION OF THE DIFFUSER FOR MAGLEV AXIAL BLOOD PUMP

Hydraulic performance is an especially important factor for maglev axial blood pumps that have been used in patients with heart disease. Most maglev axial blood pumps basically consist of a straightener, an impeller and a diffuser. The diffuser plays a key role in the performance of the maglev axial blood pump to provide an adequate pressure head and increase the hydraulic efficiency. Maglev axial blood pumps with various structural diffusers exhibit different hydraulic performance. In this study, computational fluid dynamics (CFD) analysis was performed to quantify hydrodynamic in a maglev axial blood pump with a flow rate of 6 L/min against a pressure head of 100 mmHg to optimize the diffuser structure. First, we design the prototype of diffuser structure based on traditional design method, establish blood flow channel models using commercial software ANSYS FLUENT. Specifically, compare the performance of pump with the diffusers of different parameters, such as the leading edge blade angle, blade-thickness and blade-number. The results show that the diffuser structures with the thickening blade by arc airfoil law, blade-number of 6, leading edge blade angle of 24°, and trailing edge blade angle of 90° exhibited the best hydraulic performance which could be utilized in the optimization design of maglev axial blood pumps.