纯电动城市客车EMB执行机构驱动电机制动性能分析

传统气压制动系统存在压缩机、制动油箱和空气管路,占据较大空间,而采用电子机械制动(EMB)系统代替,不但可以减小空间,还能实现对夹紧力的快速响应和精确控制。以纯电动城市客车为目标车型,讨论了EMB执行机构方案,根据传统气压盘式制动器最大夹紧力推导出电机的堵转转矩和空载转速。据此设计了永磁无刷直流驱动电机,堵转转矩为10 N·m,空载转速为370 r/min。在Maxwell 2D中搭建驱动电机有限元模型,分析电机在消除间隙阶段和夹紧力增加阶段的制动性能。结果表明所设计的驱动电机制动性能可满足要求。

自动紧急制动(AEB)技术的研究与进展

为了促进汽车自动紧急制动(AEB)技术朝着更加安全与高效的方向发展,该文从AEB系统的工作原理、发展历程、应用现状、法规标准等方面,综述了AEB技术的研究进展,总结了与AEB系统综合性能密切相关的关键技术,包括AEB系统避撞策略、制动执行机构和环境感知机构。研究表明:自动紧急制动系统能够有效避免或者缓解追尾碰撞,可提高车辆主动安全性能;受制于目前制动执行技术和前端感知技术水平,AEB系统无法实现汽车在更高车速范围以及更复杂多交通场景下的完全避撞。自动紧急制动系统未来研究的重点在于:复杂多交通场景下避撞策略综合性能优化;基于更快响应时间目标的制动执行机构研发;危险行驶工况下与多种主动安全技术的深度融合及协调控制。

A Kind of PWM Pneumatic Servo Control System——Modulation Methods and Dynamic Responses

Vibrations or dither's are features of the PWM servo control system in their steady outputs. On the grounds of analyses and experiments of a PWM pneumatic servo control system, the paper puts forward four varieties of PWM modulation methods, and concludes on the relationship between dithers and the different methods, and then discusses the influence of friction to the dithers. Results from experiments regarding the dynamic and static responses on the given system support the theories presented.

Development and control of flexible pneumatic wall-climbing robot

A new kind of flexible pneumatic wall-climbing robot,named WALKMAN-I,was proposed. WALKMAN-I is basically composed of a flexible pneumatic actuator (FPA),a flexible pneumatic spherical joint and six suction cups. It has many characteristics of low-cost,lightweight,simple structure and good flexibility. Its operating principle was introduced. Then three basic locomotion modes,which are linear motion,curvilinear motion and crossing the orthogonal planes,were presented. The safety conditions of WALKMAN-I were discussed and built. Finally,the control system was designed and experiments were carried out. Experimental results show that WALKMAN-I is able to climb on the vertical wall surface along a straight line or a curved path,and has the ability of crossing orthogonal planes and obstacles. The maximum rotation angle reaches 90°,the maximum velocity reaches 5 mm/s,and the rotation angle and the moving velocity of WALKMAN-I can be easily controlled.

Control Strategies and Mechanisms for Active Control of Sound Transmission into a Vibro-acoustic Enclosure

An analytical study was presented on active control of sound transmission into a vibro-acoustic enclosure comprising two flexible plates. Two types of actuators were used, i.e. acoustic actuator and distributed lead zirconate titanate piezoelectric (PZT) actuator instead of point force actuator. Using the modal acoustic transfer impedance-mobility matrices, the excitation and interaction in the coupled sound transmission system can be described with clear physical significance. With the control system designed to globally reduce the sound field, different control system configurations were considered, including the structural actuator on the incident plate, actuator on the receiving plate, acoustic actuator on the cavity, and their combinations. The effectiveness and performance of the control strategy corresponding to each system configuration were compared and discussed. The role and control mechanism of each type of actuator were of particular interest. It was shown that the incident plate actuator is effective in controlling the cavity-dominated modes and the structural modes dominated by the incident plate and receiving plate. Two main control mechanisms are involved in this control configuration, i.e., modal suppressing and modal rearrangement. For control system configuration with only acoustic actuator in the enclosure, the mechanism involved in this arrangement is purely modal suppression. Desirable placements of structural actuators in terms of total potential energy reduction were also discussed.

Theory and experiment of observer based magnetostrictive self-sensing actuator

Giant magnetostrictive actuators (GMAs) often work in a close-loop feedback system. This system needs independent sensors which may be difficult to be fixed, besides, excessive sensors may cause more unpredicted problems in a large system. This paper aims to develop a self-sensing GMA. An observer based on piezomagnetic equations is constructed to estimate the stress and strain of the magnetostrictive material. The observer based self-sensing approach depends on the facts that the magnetic field is controllable and that the magnetic induction is measurable. Aiming at the nonlinear hysteresis in magnetization, a hys- teresis compensation observer based on Preisach model is developed. Experiment verified the availability of the observer approach, and the hysteresis compensation observer has higher tracking precision than linear observer for dynamic force sensing.

Review of actuators for high speed active flow control

Actuators are one of the key points for the development of active flow control technology.Efficient methods of high speed flow control can provide enhanced propulsive efficiency and at the same time enable safe and maneuverable high speed flight.The development of high speed flight technology promotes the emergence of novel and robust actuators.This review introduces the state of the art in the development of actuators that can be used in high speed active flow control.The classification and different operation criteria of the actuators are discussed.The specifications,mechanisms and applications of various popular actuator types including fluidic,mechanical,and plasma actuators are described.Based on the realistic need of high speed flow control and the existing results of actuators,a new actuator design method is proposed.At last,the merits and drawbacks of the actuators are summarized and some suggestions on the development of active flow control technology are put forward.

Study of flow induced by sine wave and saw tooth plasma actuators

The effect of plasma actuator that uses saw-tooth or sine-wave shape electrodes on boundary layer flows is experimentally investigated.The measurement results are compared with a corresponding standard configuration (conventional design using two rectangular strip electrodes)-the actuator that produces a nearly two-dimensional horizontal wall jet upon actuation.PIV measurements are used to characterize the actuators in a quiescent chamber.Operating in a steady manner,the new actuators result in the formation of streamwise and spanwise vortices.That is to say,the new actuators render the plasma actuators inducing three-dimensional variations in the shear layer,offering significant flexibility in flow control.The affected flowfield with the new actuators is significantly larger than that with the conventional linear actuators.While the conventional linear actuators affect primarily the boundary layer flow on a scale of about 1 cm above the wall,the new actuators affect the near wall region at a significantly larger scale.This new design broadens the applicability and enhances the flow control effects and it is potentially a more efficient flow control device.

Lift enhancement method by synthetic jet circulation control

A novel circulation control technique is proposed to overcome the shortcomings of blowing jet circulation control, which uses the synthetic jet as the actuator and avoids the limitation about air supply requirement. The effectiveness of synthetic jet circulation control to enhance lift of NCCR1510-7067N airfoil is confirmed by solving the 2-D unsteady Reynolds-averaged Na- vier-Stokes equations. The aerodynamic characteristics and the flow structure （especially close to the trailing edge） of NCCR 1510-7067N airfoil at zero angle of attack are also presented to discuss the mechanism of lift enhancement of the airfoil with synthetic jet circulation control. The results indicate that the synthetic jet can effectively delay the separation point on the airfoil trailing edge and increase the circulation and lift of the airfoil by Coanda effect. The numerical simulation results demonstrate that the lift augmentation efficiency with synthetic jet circulation control reaches △C1/Cμ,=114 in the present study, which is much higher than the value 12.1 in the case with steady blowing jet circulation control.