Constant temperature hot-wire anemometer (CTA) is a key instrument for turbulence measurement in compressible flow, requiring both high dynamic response and rapid overheat ratio switching capability. However, non-ideal factors such as phase delay in the variable overheat ratio control circuit and parasitic circuit parameters can easily destabilize the thermal feedback loop, posing significant challenges to CTA system design. This paper presents a close-loop response analysis method based on open-loop frequency characteristics. By introducing an in-situ open-loop testing technique that employs a 10 Hz low-pass filter to block the AC feedback path while injecting a swept-frequency excitation signal near the DC operating point, this approach overcomes the limitation of conventional ex-situ open-loop testing, where the hot-wire operates outside its normal working state. This approach enables accurate analysis of system stability and bandwidth. Based on this analysis, circuit parameters can be effectively configured to optimize dynamic performance while ensuring stability. Experimental results demonstrate that the CTA system designed using this method operates stably, with a bandwidth of up to 49 kHz.

该文提出了一种利用开关阀实现气缸输出力伺服控制的新方法.基于高速开关阀自身的体积流量特性,通过对4个高速开关阀开关时序的优化配置,实现气缸输出力的精确快速控制.首先研究开关阀体积流量、PWM占空比和阀进出口压差三者之间的关系,并将其与模糊控制器相结合,建立输出力伺服控制的闭环算法.在此基础上再结合将充放气阀同时打开,调节充放气阀关闭的时间差的错时方法与模式切换设计实现输出力的伺服控制.最后搭建了气缸输出力伺服控制试验平台,开展了试验验证.结果 表明,该文所提出的方法能实现准确快速的阶跃控制且稳态误差低于0.5％,并能够较好地跟踪上0.4 HZ的高频正弦和0.1 HZ的低频正弦指令信号.

In this paper, a fuzzy logic based volume flow control method is proposed to precisely control the force of a pneumatic actuator in an electro-pneumatic system including four on-off valves. The volume flow feature, which is the relationship between the duty cycle of the pulse width modulation (PWM) period, pressure difference, and volume flow of an on-off valve, is based on the experimental data measured by a high-precision volume flow meter. Through experimental data analysis, the maximum and minimum duty cycles are acquired. A new volume flow control method is introduced for the pneumatic system. In this method, the raw measured data are innovatively processed by a segmented, polynomial fitting method, and a newly designed procedure for calculating the duty cycle is adopted. This procedure makes it possible to combine the original data with fuzzy logic control (FLC). Additionally, the method allows us to accurately control the minimum and maximum opening pulse width of the valve. Several experiments are performed based on the experimental data, instead of the traditional theoretical models. Only 0.141 N (1.41%) overshoot and 0.03 N (0.03%) steady-state error are observed in the step response experiment, and 0.123 N average error is found while tracking the sine wave reference.

In this paper, a mode-switching sliding controller with the nonlinear gain generated by a fuzzy logic controller is put forward to enhance the tracking performance in an electro-pneumatic position control system which includes four solenoid ON-OFF valves and a double rod-end cylinder. The proposed method is designed to increase the response speed and reduce the overshoots by utilizing the nonlinear gain which is determined by a fuzzy logic controller. In addition, several improvements are made in the mode-switching sliding controller originally from previous works. The mode-switching strategy is totally redesigned and a hysteresis control scheme is introduced to the new mode-switching sliding controller. Moreover, the improved controller is properly combined with the fuzzy nonlinear gain. Simulation and experiments with various kinds of input are carried out to verify the effectiveness of the proposed method. All the experiments are conducted on a field programmable gate array platform, and the experimental results validate the reliability of the novel scheme.

This paper presents an intelligent phase-change PWM strategy for a position tracking system which includes four solenoid on–off valves and a double-acting double-rod-end cylinder. The proposed technique is designed to minimize the tracking errors and improve the position tracking performance. For an electro-pneumatic system with four valves, only seven switching modes are considered valid. We initially set two switching modes in a pulse width modulation (PWM) period, and this method can also be regarded as a PWM method with changeable phases. In the complete strategy, the operating mode of the system will be selected according to the pressure state and the sliding function. All the switching modes are applied properly in the strategy. A sliding mode controller is designed to utilize the phase-change PWM strategy, and stability of the system is proved. The performance of the proposed strategy is experimentally verified on a field programmable gate array platform. All simulations and experiments verify the effectiveness of the proposed scheme.

Hotwire measurement system under constant-voltage control loop(CVCL) is one of the ideal tools for hypersonic flow field measurement. The static sensitivity coefficient and dynamic frequency response are the two main performance indexes. During development of hotwire measurement system under CVCL,a great deal of flow field tests must be conducted to make static sensitivity coefficient and dynamic frequency response of the system into the optimal state by adjusting the parameters in control loop. In the paper,the joint model of hotwire probe and CVCL was built,and the numerical simulation and analysis were conducted for the influence on the systemu0027s dynamic and static characteristics in terms of circuit parameters in CVCL and flow velocity with MATLAB. Through the simulation and analysis,the law about the effect of flow velocity,compensation network,input voltage and resistances in control loop on system performance can be achieved. CVCL must be used to improve the system response. The above results of simulation and analysis can provide a guidance in the optimization design for control loop of hotwire probe.

To optimize the design of hotwire flow_velocity measurement system under constant voltage control loop ( CVCL) ,circuit simulation model of the system is established based on Multisim,in which,hotwire probe characteris-tics are simulated by using PSpice model,T-Shape dynamic compensation network is adopted into CVCL to improve frequency response of the system. Dynamic and static characteristics of hotwire flow_velocity measurement system un-der CVCL are simulated and analyzed regarding to flow_velocity and components’ parameters in CVCL,and in situ measurement simulation of hotwire probe time constant is also conducted. The simulation results show that the laws obtained in Multisim about the effect of flow_velocity,compensation network,input voltage and resistances in CVCL on system characteristics are in accordance with numerical calculation,and also demonstrates the feasibility of this meth-odology. At the same time,the simulation and analysis for actual circuit parameters could provide important guidance in the optimization design and preparation of hotwire flow_velocity measurement system under CVCL.

为测量不同工况下流场的脉动流速,恒温型热线风速测量系统在满足稳定性要求的同时,必须具备宽频带的动态特性.分别对热线探头工作过热比、放大器增益、惠斯通桥臂电阻、流场稳定流速、补偿电感和偏置电压等参量对热线测量系统动态特性的影响效果进行了仿真分析,结果表明:增大热线探头工作过热比、放大器增益和流场稳定流速及减小桥臂电阻均能提高系统的频响;补偿电感与热线探头连接电缆电感及电路寄生电感匹配时,系统频响最佳;在上述参量配置不当时,系统频响降低,系统振荡加剧甚至不能正常工作,而提高偏置电压能消除振荡并使系统恢复稳定,同时获得平稳的动态频响.因此,提出了基于偏置电压的动态特性调节方法.方波试验结果表明,基于偏置电压的频响调节方法能使系统在不同的脉动流速测量中均能获得较为平坦的频响,且调节过程简便.

A flowmeter calibration rig is chosen as an example to present several teaching experiments, and the application meth-ods of late research-based discipline platform in the teaching are studied. Framework of information sources is proposed for data-bank construction of teaching research combination discipline platform, in which function and interrelation of staff at different levels are described.

利用LabVIEW与Multisim的模拟与数字联合仿真功能,基于频率校正法开发了控制系统串联校正实验软件平台.首先通过LabVIEW的Control Design&Simulation模块实现校正前后控制系统幅值裕度和相角裕度的数值计算,同时采用有源校正网络在Multisim中实现相应模拟电路的仿真,仿真过程中校正网络的电阻和电容值由LabVIEW前面板控件实时改变,直到仿真结果满足设计要求.最后,根据得到的Multisim仿真电路,在自动控制综合综合实验仪上加以实现,验证串联校正环节设计的正确性.此实验平台界面设计直观、操作简单、易学易用,允许学生自行设计、仿真、测试并验证设计效果,有效地缩短了实验时间、提高了实验效率,同时增强了学生参与设计性实验的积极性.

在恒温型热线风速测量系统中,当放大器增益,热线工作过热比,惠斯通桥臂电阻和偏置电压等参量配置不当时,恒温型控制回路会进入失效状态使系统不能正常工作.本文分别对上述参量引起热线风速测量系统失效的机理进行了仿真研究,结果表明:惠斯通桥臂电阻确定了系统固有稳定工作区的大小,当热线工作过热比和放大器增益配置点进入固有稳定工作区时,系统在任何工况下均能稳定工作,否则在其他参量配置不当时就会失效;提高偏置电压能使系统脱离失效状态恢复正常工作.因此,提出了基于偏置电压的恒温型热线风速测量系统稳定性控制方法.试验结果表明,基于偏置电压的稳定性控制方法能有效避免系统失效,且调节过程简单,便于提高恒温型热线风速测量系统的测量性能.更多还原

以Labview为开发工具、基于NI的myDAQ数据采集卡开发了自动控制原理中控制系统时域特性测定和频率特性测试两个实验的软件平台.myDAQ采集卡实现激励模拟信号的给定和实验数据的采集,Labview工具实现实验数据曲线实时绘制和显示、被控对象时域和频域参数在线测量和计算以及实验数据曲线打印.便于学生及时发现和纠正实验过程中错误、深入理解理论知识、提高综合分析能力.My-DAQ和Labview易于学习和掌握,利用二者开发自动控制原理实验软件平台,开发周期短,其程序接口维护和移植方便,可以为其他控制类课程相关实验项目的自主设计开发和扩展提供借鉴.

Lumped and distributed dynamic/static models of constant temperature hot-wire probe are established according to heat balance principle. Dynamic and static characteristics of hot-wire probe are analyzed in terms of hot-wire probe sizes, control circuit parameters and flow velocity.Simulation results show that reliability and stability of the hot-wire probe depend on bias voltage.The dynamic and static characteristics of hot-wire probe refly on the ratio of length to diameter ratio crucially.Once the ratio exceeds 300, heat conduction terminal loss can be ignored. When over-heating ratio of hot- wire or flow velocity increases, heat conduction terminal loss can be omitted as well .Besides frequency response of hot-wire probe can be improved simultaneously.The above conclusions can provide guidance in the improved design for hot-wire probe and its control-circuits.

Advantages and successful experiences of the foreign universities in experiment teaching and management are analyzed and summarized. Combined with the intimate understanding of engine control course experiment teaching and the current status and common problems of experiment teaching and management in domestic universities,it is pointed out that professional experimental teaching /management reform is imperative. And some feasible ideas and suggestion in the professional experimental teaching and management reform are put forward,which make the professional experimental teaching better service and contribute in the course teaching,scientific research and fostering high level talents.

To the optimization designs of hot wire probe and its control circuit,control-loop models of hot-wire probe in constant temperature model were established and verified based on PSpice in Multisim.The simulation studies were conducted for the influent on the dynamic/static characteristics of hot-wire probe in terms of bias voltage,flow-velocity,sizes and over-heating ratio based on the Pspice model.The simulation results are in accord with theoretical calculation and published analysis data of constant-temperature hot-wire probe,which show that establishing model and simulation of hot wire probe in multisim can reduce the preparation cost and improve the design efficiency.

In terms of the requirements for hot-wire/film anemometry in hypersonic airflow measurement,the recent research and development of hot-wire/film anemometry are summarized.The key problems and technical features are discussed for hypersonic hot-wire/film anemometry based on probe manufacture,control circuit design and probe calibration.The effects on thermal testing system are analyzed form hot-wire/film material,geometry and control-circuit mode,and several calibration methods are compared.Finally,some approaches have been proposed as reference to the research of hypersonic anemometry in China.

Web-based Code Management System (WCMS) is an essential tool for realizing information exchange in distant collaborative product design and manufacturing among global-based enterprises. A framework for WCMS is built up on a three-tier client/server system and the WCMS is developed utilizing JAVA and J2EE technologies. The developed WCMS mainly uses servlets and JSP to handle user inputs and manage and retrieve code data from the database through the JDBC driver, with the server components stored on a middleware program called Tomcat. The WCMS developed in this work has been successfully implemented in an enterprise.

This paper gives out a kind of method in designing three-tiered client/server Heterogeneous Multi-Database Accessing Based on Component Technology,and uses this method to administrate and realize information integrating and data accessing of distributed- Heterogeneous- Multi-Database,encapsulate the system function's modules and send them to application server,and make the Heterogeneous system have good recomposation. It also develops a Heterogeneous- Multi-Database's Universal Integrative Environment based on simulation systems by using PowerBuilder 8.0 as developing tools and EAServer as application server.