水轮机转轮前来流的计算

本文介绍一种采用Ｓ１，Ｓ２两类流面迭代计算确定转轮进口前轴面速度及环量分布的方法．与实测结果相比，此法计算结果比采用传统设计方法计算所得结果更为合理，它有助于改进水轮机转轮的水力设计．

正反转双转轮水轮机水力性能研究

研究用于低水头的反转双转轮、双转子小型水力发电设备,探讨反转双转轮的基本原理与水轮机转轮的水力特性,确认了在流量一定的运转工况时反转前转轮转速与正转后转轮转速相等条件下可以得到最高效率、且出力为两转轮之和(单转轮的2倍)。通过模型实验,确认了正反转两转轮的水力性能基本满足一般的相似准则,可以进行实际转轮设计时的换算。

Yaw stability control using the fuzzy PID controller for active front steering

In order to improve the yaw stability of the vehicle with active front steering system, an adaptive PID-type fuzzy control scheme is designed to make the yaw rate tracking the desired values as close as possible. A 2-DOF vehicle model with active front steering is built firstly, and then the fuzzy PID controller is designed in detail. The simulation investigations of the yaw stability with different steering ma- neuvers are performed. The simulation results show the effectiveness of the fuzzy PID controller for improving the vehicle＇s yaw stability.

Path planning and stability control of collision avoidance system based on active front steering

Vehicle collision avoidance system is a kind of auxiliary driving system based on vehicle active safety,which can assist the driver to take the initiative to avoid obstacles under certain conditions,so as to effectively improve the driving safety of vehicle.This paper presents a collision avoidance system for an autonomous vehicle based on an active front steering,which mainly consists of a path planner and a robust tracking controller.A path planner is designed based on polynomial parameterization optimized by simulated annealing algorithm,which plans an evasive trajectory to bypass the obstacle and avoid crashes.The dynamic models of the AFS system,vehicle as well as the driver model are established,and based on these,a robust tracking controller is proposed,which controls the system to resist external disturbances and work in accordance with the planning trajectory.The proposed collision avoidance system is testified through CarSim and Simulink combined simulation platform.The simulation results show that it can effectively track the planning trajectory,and improve the steering stability and anti-interference performance of the vehicle.

A modified structure internal model robust control method for the integration of active front steering and direct yaw moment control

Taking into account the nonlinearity of vehicle dynamics and the variations of vehicle parameters,the integrated control strategy for active front steering(AFS)and direct yaw control(DYC)that can maintain the performance and robustness is a key issue to be researched.Currently,the H∞method is widely applied to the integrated control of chassis dynamics,but it always sacrifices the performance in order to enhance the stability.The modified structure internal model robust control(MSIMC)obtained by modifying internal model control(IMC)structure is proposed for the integrated control of AFS and DYC to surmount the conflict between performance and robustness.Double lane change(DLC)simulation is developed to compare the performance and the stability of the MSIMC strategy,the PID controller based on the reference vehicle model and the H∞controller.Simulation results show that the PID controller may oscillate and go into instability in severe driving conditions because of large variations of tire parameters,the H∞controller sacrifices the performance in order to enhance the stability,and only the MSIMC controller can both ensure the robustness and the high performance of the integrated control of AFS and DYC.

Robust control of hand wheel torque for active front steering system

Active front steering(AFS)system has been used as a promising technology which improves the steering portability and handing stability of vehicles.It employs a steering motor to realize the functions of variable steering ratio and vehicle stability control.However,it has a serious problem of unexpected reaction hand wheel torque caused by the additional steering angle.In this paper,the optimum hand wheel torque is designed based on the linear tire model.Considering the uncertainty and disturbance of the steering system and vehicle,an H∞controller is developed to make sure the hand wheel torque follows the reference torque accurately and quickly.The simulation shows that the proposed controller can compensate the unnatural reaction torque and provide a good steering feel for the driver.

读者信箱

问:为什么气瓶式气枪多以二氧化碳气体为动力源发射铅弹? 上海 区俊泉 答:利用二氧化碳气体作为发射气枪铅弹的动力源,主要原因有两个方面:二氧化碳具有在常温下化学性能稳定的特点,在正常条件下使用不会影响射弹散布;二氧化碳具有无色无臭,不可燃也不助燃的特点,在正常条件下使用不会对人体健康造成影响,也不会燃烧造成事故。