A method for determining the layout of a yaw system based on the Delphi method and the analytic hierarchy process

Wind power technology has been widely used due to its characteristics of environmental protection,sustainability and low cost.The yaw system plays a vital role in improving the energy capture efficiency of a wind turbine.However,the method of layout determination is lacking in the yaw system.To solve this problem,a method that combines the Delphi method and the analytic hierarchy process was proposed in this study.Twelve evaluation indexes,including transmission efficiency,ratio range,operating temperature range and others,were identified by screening 18 technical indicators using the Delphi method.Subsequently,the evaluation system of the yaw system was established.Then,six configuration schemes were selected.Experts’scores of schemes were collected according to the evaluation system and the score matrix of evaluation indexes was obtained.The hierarchical model of the evaluation indexes of the yaw system was established and the comprehensive weight was obtained by using the analytic hierarchy process.After calculating the comprehensive evaluation score,the comprehensive evaluation result was obtained.The 2Z-X(A)negative mechanism,which achieved the highest score of 0.9227,is the optimal scheme.A new method and specific process are provided for designers.The research gap in the scheme selection method for yaw systems is filled.

On the effect of pitch and yaw angles in oblique impacts of smallcaliber projectiles

A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.

Impact of Blade-Flapping Vibration on Aerodynamic Characteristics of Wind Turbines under Yaw Conditions

Although the aerodynamic loading of wind turbine blades under various conditions has been widely studied,the radial distribution of load along the blade under various yaw conditions and with blade flapping phenomena is poorly understood.This study aims to investigate the effects of second-order flapwise vibration on the mean and fluctuation characteristics of the torque and axial thrust of wind turbines under yaw conditions using computational fluid dynamics(CFD).In the CFD model,the blades are segmented radially to comprehensively analyze the distribution patterns of torque,axial load,and tangential load.The following results are obtained.(i)After applying flapwise vibration,the torque and axial thrust of wind turbines decrease in relation to those of the rigid model,with significantly increased fluctuations.(ii)Flapwise vibration causes the blades to reciprocate along the axial direction,altering the local angle of attack and velocity of the blades relative to the incoming wind flow.This results in the contraction of the torque region from a circular shape to a complex“gear”shape,which is accompanied by evident oscillations.(iii)Compared to the tangential load,the axial load on the blades is more sensitive to flapwise vibration although both exhibit significantly enhanced fluctuations.This study not only reveals the impact of flapwise vibration on wind turbine blade performance,including the reduction of torque and axial thrust and increased operational fluctuations,but also clarifies the radial distribution patterns of blade aerodynamic characteristics,which is of great significance for optimizing wind turbine blade design and reducing fatigue risks.

Adaptive Model Predictive Control for Yaw System of Variable-speed Wind Turbines

Due to varying characteristics of the wind condition, the performance of the wind turbines can be optimized by adapting the parameters of the control system. In this letter, an adaptive technique is proposed for the novel model predictive control(MPC) for the yaw system of the wind turbines. The control horizon is adapted to the one with the best predictive performance among multiple control horizons. The adaptive MPC is demonstrated by simulations using real wind data, and its performance is compared with the baseline MPC at fixed control horizon. Results show that the adaptive MPC provides better comprehensive performance than the baseline ones at different preview time of wind directions. Therefore, the proposed adaptive technique is potentially useful for the wind turbines in the future.

Debris cloud structure and hazardous fragments distribution under hypervelocity yaw impact

This study investigates how the debris cloud structure and hazardous fragment distribution vary with attack angle by simulating a circular cylinder projectile hypervelocity impinging on a thin plate using the finite element-smoothed particle hydrodynamics(FE-SPH)adaptive method.Based on the comparison and analysis of the experimental and simulation results,the FE-SPH adaptive method was applied to address the hypervelocity yaw impact problem,and the variation law of the debris cloud structure with the attack angle was obtained.The screening criterion of the hazardous fragment at yaw impact is given by analyzing the debris formation obtained by the FE-SPH adaptive method,and the distribution characteristics of hazardous fragments and their relationship with the attack angle are given.Moreover,the velocity space was used to evaluate the distribution range and damage capability of asymmetric hazardous fragments.The maximum velocity angle was extended from fully symmetrical working conditions to asymmetrical cases to describe the asymmetrical debris cloud distribution range.In this range,the energy density was calculated to quantitatively analyze how much damage hazardous fragments inflict on the rear plate.The results showed that the number of hazardous fragments generated by the case near the 35°attack angle was the largest,the distribution range was the smallest,and the energy density was the largest.These results suggest that in this case,debris cloud generated by the impact had the strongest damage to the rear plate.

The Application of Moving Base Systems in Driving Simulators with Special Regard to the Sensation of Yaw Movements

Driving simulators involve the capability of simulating critical and dangerous driving situations up to the limits of active safety. They are employed for investigating the interactions of the driver-vehicle system under reproducible and non-dangerous conditions. Because of their flexibility they are well established in scientific research. They are mainly used in current automotive fields of research like driver assistance and autonomous driving systems. The development of assistance systems makes the human being as the directly concerned component irreplaceable in the development process. Here the use of driving simulators has become an essential element, because they offer the possibility to integrate the human being as a real part into the simulation environment. It must be considered that the circuit of information has to be the same as under real driving conditions. Otherwise the results are not transferable. This paper deals with the possibilities of presenting all information to the driver, which are necessary to give him a realistic impression of driving. A main subject is the sensation of yaw-movements, which could be of interest when novel kinds of moving base systems are designed.

A data-driven machine learning approach for yaw control applications of wind farms

This study proposes a cost-effective machine-learning based model for predicting velocity and turbulence kineticenergy fields in the wake of wind turbines for yaw control applications.The model consists of an auto-encoderconvolutional neural network(ACNN)trained to extract the features of turbine wakes using instantaneous datafrom large-eddy simulation(LES).The proposed framework is demonstrated by applying it to the Sandia NationalLaboratory Scaled Wind Farm Technology facility consisting of three 225 kW turbines.LES of this site is performedfor different wind speeds and yaw angles to generate datasets for training and validating the proposed ACNN.It is shown that the ACNN accurately predicts turbine wake characteristics for cases with turbine yaw angleand wind speed that were not part of the training process.Specifically,the ACNN is shown to reproduce thewake redirection of the upstream turbine and the secondary wake steering of the downstream turbine accurately.Compared to the brute-force LES,the ACNN developed herein is shown to reduce the overall computational costrequired to obtain the steady state first and second-order statistics of the wind farm by about 85%.

风力发电机组偏航系统运行与模拟故障实训平台设计

为便于学习风力发电机组运行方式和故障工况,参照实际兆瓦级机组偏航系统,设计风力发电机组偏航系统运行与模拟故障实训平台。该平台分设偏航执行平台和偏航控制系统人机交互操作平台,可精确实现偏航系统制动、偏航对风和解缆,也可通过设置故障验证学员对偏航系统的掌握程度。适用于国内高校风电专业学员、风电行业培训基地运维人员实操与培训考核。

Study on damage mechanism and damage distribution of the rear plate under impact of debris cloud

The debris cloud generated by the hypervelocity impact(HVI)of orbiting space debris directly threatens the spacecraft.A full understanding of the damage mechanism of rear plate is useful for the optimal design of protective structures.In this study,the hypervelocity yaw impact of a cylindrical aluminum projectile on a double-layer aluminum plate is simulated by the FE-SPH adaptive method,and the damage process of the rear plate under the impact of the debris cloud is analyzed based on the debris cloud structure.The damage process can be divided into the main impact stage of the debris cloud and the structural response of the rear plate.The main impact stage lasts a short time and is the basis of the rear plate damage.In the stage of structure response,the continuous deformation and inertial motion of the rear plate dominate the perforation of the rear plate.We further analyze the damage mechanism and damage distribution characteristics of the rear plate in detail.Moreover,the connection between velocity space and position space of the debris cloud is established,which promotes the general analysis of the damage law of debris cloud.Based on the relationship,the features of typical damage areas are identified by the localized fine analysis.Both the cumulative effect and structural response cause the perforation of rear plate;in the non-perforated area,cratering by the impact of hazardous fragments is the main damage mode of the rear plate.

大型风电机组滑动式偏航系统制动过程机电耦合特性规律

偏航系统是连接风电机组叶轮与塔筒承载部件,其偏航运动受气-机-电-液耦合作用,通过对偏航系统机电特性分析,开展了偏航力矩载荷力学分析计算,基于4种典型的极限工况,对工况发生历程中偏航力矩变化规律进行分析,重点对偏航运行制动及偏航静止制动特性进行研究,研究表明:电机制动速度控制阀值、制动响应时长、尾部制动时长是滑动式偏航系统制动特性主要考虑因素,确定滑动系统配合以变频控制偏航方式,采用失电制动模式为最优选择,制动电机速度可降低至35%。而在偏航静止制动状态下,相比于驱动个数的增加,制动力矩增大对改善偏航滑移最为明显,产生偏航瞬时发生转动角度更小,但输出小齿冲击受载更大。

基于风力发电机组偏航控制策略关键参数的测试与分析

风电机组偏航控制策略中,各偏航动作之间状态的切换需依靠液压夹钳、电磁刹车与偏航驱动电机共同控制实现,所需4个关键时间点需通过样机测试得出。针对此,以某机型液压系统厂内测试为例,获取液压系统泄压-建压测试曲线;并增设多组对比测试,深入分析影响系统性能的因素;通过多领域融合的系统仿真软件进行仿真分析,为系统快速优化提供更多途径。结果表明:3台液压站所测泄压-建压曲线一致性较高,可准确得到4个时间点;单、双蓄能器对系统泄压-建压速度影响不大;不同回路背压值对系统建压时长影响较大,对泄压时长影响较小;串联制动器总出口压力响应滞后于总入口响应。可利用仿真手段设置更多系统变量组合,进一步快速优化系统策略,降低机组运行故障率。

一种带压力控制的风机偏航制动器设计与应用

为提高风机偏航液压制动系统的响应性能和环境适应性,在常规偏航制动器的基础上改进得到一种带压力控制功能的新型制动器。以2 MW和8 MW风机为例,阐述了带压力控制的偏航制动器用于偏航液压制动系统设计时的主要方法及有益效果,并对使用和未使用该制动器的偏航液压制动系统进行了全压制动和阻尼制动工况的仿真分析与对比。结果表明,带压力控制的偏航制动器可显著提高制动系统的响应速度和低温稳定性,为风机偏航制动器及偏航液压制动系统的优化设计提供了参考。

风电机组偏航刹车系统液压回路优化

部分风电机组的偏航阻尼器采用偏航液压卡钳,北方地区风电场风电机组运行中出现偏航减速器卡死、偏航刹车盘严重磨损等问题,严重影响风电机组安全稳定运行,且造成风电机组长期停运及产生高昂的维修费用。文章通过研究风电机组偏航系统液压回路工作原理,进行数据分析查找故障原因,并提出了优化方案,可有效解决现场存在的问题。

基于Maxwell-LSTM的抗蛇行减振器混合建模方法研究

列车车轮踏面在实际服役环境下的磨损,会提高抗蛇行减振器的工作频率。传统动力学仿真使用的Maxwell模型在模拟高频状态下的抗蛇行减振器动态特性存在挑战。而能够准确拟合高频状态下的抗蛇行减振器动态特性的物理参数模型存在计算效率低下、无法在多体动力学仿真中运用的问题。文中提出一种Maxwell等效参数模型和LSTM神经网络耦合的减振器混合建模方法,在传统Maxwell模型基础上,通过LSTM神经网络捕捉输入变量自身变化特性,间接考虑外部激励的频变与幅变以应对上述挑战。为证明该混合建模方法的可行性,将使用该方法训练好的混合模型与台架试验结果、非线性的刚度阻尼分段Maxwell模型进行对比。结果表明:相较于分段Maxwell模型,LSTM混合模型在计算效率基本一致的前提下,高频激励下混合模型误差平均降低22.31%,高幅值激励下混合模型误差平均降低26.89%,动态刚度误差平均降低26.35%,动态阻尼误差平均降低21.01%。可以得出结论,LSTM混合模型在表征减振器高频高幅值下的动态特性具有优势,基于Maxwell-LSTM的抗蛇行减振器混合建模方法可以解决传统动力学模型计算效率和计算精度之间的矛盾,更适合用于各类工况下的车辆系统动力学仿真。

客车横摆稳定性预设性能PID控制

针对客车转向横摆稳定性控制问题,提出了一种预定性能PID控制方法。首先,构建了车辆二自由度模型和电液复合转向系统(EHCSS)模型的集成模型。然后,设计了用于客车主动转向控制的预设性能PID控制器,该控制器能够预先设定误差收敛时间和收敛精度。最后,利用硬件在环设备,对所提控制方法进行验证。实验结果表明:预设性能PID可以精准地跟踪期望值,并且误差都收敛于预设性能范围内,有效地提高了客车在转向时的横摆稳定性。

Road Friction Estimation under Complicated Maneuver Conditions for Active Yaw Control

Road friction coefficient is a key factor for the stability control of the vehicle dynamics in the critical conditions. Obviously the vehicle dynamics stability control systems, including the anti-lock brake system（ABS）, the traction control system（TCS）, and the active yaw control（AYC） system, need the accurate tire and road friction information. However, the simplified method based on the linear tire and vehicle model could not obtain the accurate road friction coefficient for the complicated maneuver of the vehicle. Because the active braking control mode of AYC is different from that of ABS, the road friction coefficient cannot be estimated only with the dynamics states of the tire. With the related dynamics states measured by the sensors of AYC, a comprehensive strategy of the road friction estimation for the active yaw control is brought forward with the sensor fusion technique. Firstly, the variations of the dynamics characteristics of vehicle and tire, and the stability control mode in the steering process are considered, and then the proper road friction estimation methods are brought forward according to the vehicle maneuver process. In the steering maneuver without braking, the comprehensive road friction from the four wheels may be estimated based on the multi-sensor signal fusion method. The estimated values of the road friction reflect the road friction characteristic. When the active brake involved, the road friction coefficient of the braked wheel may be estimated based on the brake pressure and tire forces, the estimated values reflect the road friction between the braked wheel and the road. So the optimal control of the wheel slip rate may be obtained according to the road friction coefficient. The methods proposed in the paper are integrated into the real time controller of AYC, which is matched onto the test vehicle. The ground tests validate the accuracy of the proposed method under the complicated maneuver conditions.

An Adaptive Nonsingular Fast Terminal Sliding Mode Control for Yaw Stability Control of Bus Based on STI Tire Model

Due to the bus characteristics of large quality,high center of gravity and narrow wheelbase,the research of its yaw stability control(YSC)system has become the focus in the field of vehicle system dynamics.However,the tire nonlinear mechanical properties and the effectiveness of the YSC control system are not considered carefully in the current research.In this paper,a novel adaptive nonsingular fast terminal sliding mode(ANFTSM)control scheme for YSC is proposed to improve the bus curve driving stability and safety on slippery roads.Firstly,the STI(Systems Technologies Inc.)tire model,which can effectively reflect the nonlinear coupling relationship between the tire longitudinal force and lateral force,is established based on experimental data and firstly adopted in the bus YSC system design.On this basis,a more accurate bus lateral dynamics model is built and a novel YSC strategy based on ANFTSM,which has the merits of fast transient response,finite time convergence and high robustness against uncertainties and external disturbances,is designed.Thirdly,to solve the optimal allocation problem of the tire forces,whose objective is to achieve the desired direct yaw moment through the effective distribution of the brake force of each tire,the robust least-squares allocation method is adopted.To verify the feasibility,effectiveness and practicality of the proposed bus YSC approach,the TruckSim-Simulink co-simulation results are finally provided.The co-simulation results show that the lateral stability of bus under special driving conditions has been significantly improved.This research proposes a more effective design method for bus YSC system based on a more accurate tire model.

CFD Based Determination of Dynamic Stability Derivatives in Yaw for a Bird

Dynamic yaw stability derivatives of a gull bird are determined using Computational Fluid Dynamics（CFD） method. Two kinds of motions are applied for calculating the dynamic yaw stability derivatives CNr and CNβ. The first one relates to a lateral translation and, separately, to a yaw rotation. The second one consists of a combined translational and rotational motion. To determine dynamic yaw stability derivatives, the simulation of an unsteady flow with a bird model showing a harmonic motion is performed. The flow solution for each time step is obtained by solving unsteady Euler equations based on a finite volume approach for a small reduced frequency. Then, an evaluation of unsteady forces and moments for one cycle is conducted using harmonic Fourier analysis. The results of the dynamic yaw stability derivatives for both simulations of the model show a good agreement.

Direct Yaw Moment Control for Distributed Drive Electric Vehicle Handling Performance Improvement

For a distributed drive electric vehicle（DDEV） driven by four in-wheel motors, advanced vehicle dynamic control methods can be realized easily because motors can be controlled independently, quickly and precisely. And direct yaw-moment control（DYC） has been widely studied and applied to vehicle stability control. Good vehicle handling performance： quick yaw rate transient response, small overshoot, high steady yaw rate gain, etc, is required by drivers under normal conditions, which is less concerned, however. Based on the hierarchical control methodology, a novel control system using direct yaw moment control for improving handling performance of a distributed drive electric vehicle especially under normal driving conditions has been proposed. The upper-loop control system consists of two parts： a state feedback controller, which aims to realize the ideal transient response of yaw rate, with a vehicle sideslip angle observer; and a steering wheel angle feedforward controller designed to achieve a desired yaw rate steady gain. Under the restriction of the effect of poles and zeros in the closed-loop transfer function on the system response and the capacity of in-wheel motors, the integrated time and absolute error（ITAE） function is utilized as the cost function in the optimal control to calculate the ideal eigen frequency and damper coefficient of the system and obtain optimal feedback matrix and feedforward matrix. Simulations and experiments with a DDEV under multiple maneuvers are carried out and show the effectiveness of the proposed method： yaw rate rising time is reduced, steady yaw rate gain is increased, vehicle steering characteristic is close to neutral steer and drivers burdens are also reduced. The control system improves vehicle handling performance under normal conditions in both transient and steady response. State feedback control instead of model following control is introduced in the control system so that the sense of control intervention to drivers is relieved.