Advanced Materials Research Vols. 383-390

Abstract: Focusing on energy-saving issues of boiler, this paper finds out the combustion conditions inside boiler furnace by monitoring and analysis on oxygen content of flue gas, carbon content of fly ash, CO and CO2 contents. The intelligent control of boiler combustion was achieved and combustion efficiency was rosen. Using neural network controlling model, automatic optimization of oxygen delivery volume,coal delivery volume, the total wind pressure of primary air, the secondary air-door opening degree and furnace negative pressure were achieved, and the boiler efficiency increasing by 5 ~ 7%.

Abstract: On PID control and fuzzy control in permanent magnet synchronous linear motor (PMLSM) there is some shortage. Control for linear motor characteristics of vulnerable parameter perturbation is proposed based on fuzzy self-optimizing control algorithm to reduce the dependence on the model. GA algorithm using the parameters of fuzzy algorithm self-optimizing tuning, the motor can be reduced to some extent the impact of changes in their model, and improve the control effect. Finally, Matlab simulation of the PMLSM traditional PID speed control with fuzzy parameters self-optimizing speed control comparison, the results show that the fuzzy parameters self-optimizing control is better than traditional PID control.

Abstract: This paper proposes a flux observer of voltage-current model based on PI regulator .Flux estimator value of current model at low speed is convergent gradually, so we adopt the current model. On the basis of traditional voltage model, we adopt improved model which substitute pure integral part with first-order inertia part and a compensation part, and it can solve DC drift and initial value with this method. Two models can be switched smoothly without concussion by setting appropriate PI parameter. The performance of the model is investigated and verified experimentally.

Abstract: Based on the working characteristics of air spring, vehicle active rollover control system is studied. First , vehicle rollover forecast algorithm is designed by using the vehicle rollover forecast technique TTR. Then vehicle active rollover control system is designed with air spring inflation/deflation characteristics. Simulation results show that the design of vehicle active rollover control system can predict rollover risk, achieve the timely warning of vehicle rollover, and can adjust the air spring stiffness timely, improve vehicle lateral stability, reduce vehicle rollover accident under the condition of rollover risk.

Abstract: In the rotating machinery, rolling bearing is used widespread in many places. Due to various reasons, there is great dispersion in the life of bearing. Therefore, it is very important to have fault diagnosis of rolling bearing, especially the small fault diagnosis of rolling bearing. According to the characteristics of rolling bearing defect signals and the features integrated with wavelet transform, Hilbert transform and envelope spectrum detailed analysis, this text proposed a method to judge the bearing failure. At first, bearing vibration signals are reconstructed from wavelet filter and envelope signals are obtained by Hilbert transform and then vibration spectrum is obtained from the refining envelope spectrum. Bearing failure is judged from the refining frequency spectrum. Bearing failure is also estimated by experiment to verify the correctness of theoretical analysis.

Abstract: Direct torque control (DTC) has been widely used due to its advantages of less parameter dependence and faster torque response. However, in conventional DTC, there are obvious torque and flux ripples. This paper studies the influence of zero space voltage vectors on DTC system of permanent magnet synchronous motor (PMSM). The control model is established with Matlab/Simulink software. The simulation results show that the ripple torque can be reduced significantly when zero space voltage vectors are used. Meanwhile, the use of zero space voltage vectors can evidently decrease the switching frequency of the power switches as well as the switching loss. The achievements in this paper can provide a reference to improve DTC performance of PMSM.

Abstract: In view of the high-order, nonlinear, strong coupling, multivariable and time varying character of wind energy conversion system, the fuzzy-logic control strategy is introduced in this paper. First, this thesis analyzes and establishes the mechanism model for each component element of the megawatt class variable-speed variable-pitch wind turbines as well as the wind speed model. Second, for the goal of maximum wind power extraction under rated wind and peak power output maintaining above rated speed wind, PID controllers as well as fuzzy-logic controllers are designed respectively by different wind velocity condition. The simulation results demonstrate that no matter for the following up performance or the anti-interference capability, the fuzzy controllers which are devised in the paper have a better control effect than PID controllers. The fuzzy controllers can reduce system’s overshoot and regulation time more effectively, offset the negative impacts of nonlinearity, and they have better robustness too.

Abstract: A novel Detent-force-based Magnetic Suspension System (DMSS) is presented. The topological structure and operating principle of DMSS are analyzed. The characteristics of the axial, radial force and magnetic field and torsion moment are studied with FEA method respectively. Simulation results show that the DMSS can generate larger levitation force than common levitation systems, and its levitation mode is a passive suspension in the axial direction and torsion without external control.

Abstract: With the non-linear load being used in great quantities, a large number of harmonics and inter-harmonics exist in electrical system. However, lacking of local information, traditional Fourier transform is not suitable for inter-harmonic analysis. In the method of time-frequency analysis, WVD is a joint distribution of energy time-frequency which provides a method for inter-harmonic analysis, but the influence of the cross terms limits application. W-H transform can effectively reduce the impact of cross terms and then extract effective information of inter-harmonic.

Abstract: In this paper, the dynamic model of a two-link rigid-flexible manipulator was established by using the theory of Lagrange equation. Due to the model is a distributed-parameter system, we present a simple, efficient method for model reduction based on spectral approximation method such that a model-based scheme can be implemented. The method was illustrated by comparing with the simulation results of the reduced-order model and the virtual reduced model based on finite element method.