Papers by Keyword: Variable-Pitch

Abstract: in this work, a model for variable-pitch wind power generation controller system is set up. The model is simulated under MATLAB / Simulink environment. The simulation result shows that adding adjustable variable-pitch wind turbine can significantly improves the stability of the generator speed and output power. This work can provide a reference for correlative study on wind power generation system.

Abstract: A reverse analysis method for determining the stiffness characteristics of nonlinear suspension spring with variable pitch and wire diameter is developed by introducing the ideas of dispersion. Meanwhile, the reverse analysis of a nonlinear suspension spring used in truck is completed as an example, and the progressive force-displacement curves obtained by theoretical and experimental analysis are compared in order to verify the validity of the reverse analysis method used for nonlinear suspension spring.

Abstract: A FLC-PID controller is designed to solve parameter time changing and nor-linear problems of variable-pitch syetem. The FLC-PID control metod can improve the derivation responses of system. Control simulation are carried out to indicates that it is superior to the traditional PID and FLC controller.

Abstract: Active power smoothing of wind generator is very important to the utilization of wind energy. One-step ahead prediction of wind speed with the inverse-system is proposed in this paper. Wind generator is simplified as first order dynamic model. An inverse-system is designed to cascade with the model. Kalman filter and ARIMA models are used to predict the wind speed one-step ahead. The predicted wind speed is the input to the cascade system. The simulation shows that the fluctuations of the torque, the active power and the pitch angle are decreased effectively.

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: The strong demand for increasing productivity and workpiece quality in milling process makes the machine-tool system operate close to the limit of its dynamic stability. Milling cutters with variable pitch angles can be very effective in improving stability against chatter for certain speed ranges, which will be predicted by the model presented here. The present paper deals with the design of structural geometry of variable pitch end mills in detail. Based on the analysis of tooth engagement factor, which is expressed and extended in the paper, an approach is proposed to design variable pitch end mill with high milling stability. The certain speed ranges with high milling stability are given.

Abstract: In order to solve the problems of wind power generation system model uncertainty, we designed a robust tracking controller according to the robust control theories and the method of linear matrix inequality (LMI). For ensuring the stability and dynamic characteristics of robust, we gave the calculating method of proportion and integral gains, researched the robust control strategy with pole constraint that is based on minimal power tracking controller. The results of the simulation show the controller can realize the steady close-loop and possess good disturbance rejection and dynamic characteristic in some disturbances and uncertainties existed in system.

Abstract: This paper reviews the principle of power production, and analyses the influnece on aerodynamic load and output power due to the variation of pitch angle. For three-bladed upwind horizontal axis wind turbine, the blade pitch control is used primarily to adjust the power coefficient and obtain the optimal power at high wind speed, but it also make aerodynamic load, such as edgewise, flapwise and torsion moment, change during variable pitch control. Hydraulic mechanism is used in a process requiring large driving forces and torques, fast response and high stiffness. Therefore, the variable pitch mechanism is operated using electro-hydraulic proportional technology in this paper. Simulation results are presented and analysed to show that aerodynamic load and output power are sensitivity to pitch angle for wind turbine blade. These works lay foundation for the further studying of individual pitch, power control, fatigue and dynamical stability for wind turbine.

Abstract: The article introduces three design techniques of variable pitch & groove depth & groove width screw. We found parameterized mathematical model of the type of heterotypic screw by analyzing and computing. Then it can realize to CNC machining of variable pitch & groove depth & groove width screw on lathe.

Abstract: Chatter is one of the main factors that affects the manufacturing quality and limits the productivity during milling. If properly selecting mills with variable pitch distribution, the chatter may be reduced. If mills have sufficient rigidity, its vibration resistance will be improved extremely. The paper summarizes the effects of helix angles, pitch angles distribution on the maximum stress, the maximum strain based on FEM simulation, the result of simulation can offer theoretical instructions to optimize and select the optimal mills based on intensity and rigidity.