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附 錄A
A. multi-purpose vehicle chassis dynamometer
With the rapid development of the automotive industry, traffic accidents and environmental pollution on the growing threat to human life, thus increasing the importance of vehicle detection technology stand out a variety of testing equipment have emerged. As a large-scale laboratory equipment, automobile chassis dynamometer can simulate vehicle road test a variety of conditions, the completion of the car's economy test, power test, evaluation and analysis of emissions performance, reliability test and drive the car on the special test . It is in the automotive testing research, product development and quality testing new cars and the car is essential. Use complete chassis dynamometer test and the type of vehicle quality inspection and road test compared with the usual test speed, high precision, low cost, data stability, comparability and good.
In view of chassis dynamometers these advantages, many domestic manufacturers have developed a series of dynamometer products, these products are mainly used to detect the following auto axle load 10 t chassis power output, the maximum absorption power of 150 kW. Test items mainly: chassis power output, the driving force, speed, acceleration, glide performance and the accuracy of the speedometer and odometer, and so on.
But domestic dynamometer products there are many imperfections, must be resolved. For example: car in different conditions, different load and other conditions, the dynamic performance can not be achieved continuous measurement and control system, control method is relatively backward. This article is for these deficiencies, the control system, control method has been improved to achieve the different conditions and different load conditions, the car's dynamic performance for accurate and reliable continuous measurement and continuous measurement of emissions to increase functionality. In addition, the light of foreign advanced technology and experience, the use of computer technology for vehicle-related transmission loss, rolling resistance, altitude, temperature and other parameters of simulation and correction.
Multi-purpose vehicle chassis dynamometer (hereinafter referred to as dynamometer) is a new chassis dynamometer. Aircraft measurement and control system is the key to achieve its power equipment.
Dynamometer testing computer control system to control the use of high performance industrial control computer, the entire control system including computer, monitor, keyboard, mouse, printers, input and output terminal blocks, multi-PC bus interface card, SCR and its control circuit, all components have been installed in the 1.8 m high of the standard 19-inch industrial control cabinet. Dynamometer control system coupled with the mechanical part of the (bench) constitute the entire dynamometer. Bench control system by the pressure sensor, speed sensor, pneumatic lift, and eddy current machines and other equipment to complete the dynamometer measurement and control.
PC bus interface board is a multi-computer interfaces and measurement equipment, control channel, on-site analog signal amplification and analog-digital conversion, digital signal measurement done by it, the interface card can also control multiple actuator movements, other The card also provides a counter for frequency measurement of the interface.
Wheel drive car in the bench rotating drum, drum rotation by the optical pulse output of the decoder, access multi-function card counter, measuring speed and distance traveled. Car driving in the bench, the driving force can drum machine by the eddy current coupling the pressure sensor, the input channel signal sent to the computer, combined with the speed signal measurable car's dynamic performance. In the actual measurement process, the measured speed signal and set the speed comparison, according to a certain algorithm to adjust bias resistance (eddy current excitation current), so that speed can be stabilized at a given value, complete constant speed under the conditions of the various data measurements.
Dynamometer applications from the measurement control program, the login program and database service program structure, program design using advanced C / S (Client / Server) design. Measurement control program and the login program is a client application, they exchange data with the database is a database service procedures are completed, the database structure is transparent to users, to facilitate the system and other motor vehicle testing equipment or manage network connections. User login process is complete the basic information on the vehicle, the initial set of test items; measurement control program is the core of the system program, its main function is to complete the measurement and control hardware signals, according to testing requirements set by the login program to complete the detection task, the program also provides another parameter setting, test results query, print and other auxiliary functions.
Eddy current machines, also known as eddy current dynamometer, is based on the eddy current (also known physics Foucault current) work equipment. It consists of two parts, the stator and rotor. The stator frame and the stator part including the exciting coil mounted on top. The stator frame around the hole, the excitation coils installed in the hole. The framework of the central part of the stator hub, with two bearing supports the rotor shaft. Including the rotor shaft and the rotor part fixed on the axis of the two rotors, two rotors are located at both ends of the stator part of the rotor shaft can be driven by external forces and free rotation. The inside of the rotor and the stator end face to maintain a small gap, the gap is called electromagnetic air gap. The inner side of the rotor is a very smooth surface, eddy current is generated in the smooth plane.
Eddy current machine field winding access current, flux through the stator, eddy current ring, the air gap, rotor constitute a closed magnetic circuit. When the car wheel and drive roller rotates the rotor eddy current machines, due to changes in magnetic flux density of the surface of the rotor eddy current, the eddy current and magnetic field interact to produce the reverse braking torque, the stator swing around the spindle axis. Pass through the leverage of the brake torque to the pressure sensor, pressure sensor gives the corresponding electrical signals, processed by the calculation, the instantaneous power can be drawn vehicle parameters. Adjust the excitation current size, you can change the eddy current machine braking torque, with a corresponding change in vehicle speed, changing the excitation current and speed the formation of a closed loop, constant speed or constant force and, ultimately, the power measurement.
Eddy current machine has a maximum speed and load range. In addition, its small size, low cost, more suitable for control automation. AC motors (induction motors) with a minimum speed (800 ~ 1500r/min) and load range, less stable, with a little hard to load features. DC Braking device with high performance, easy operation, stable working conditions, the transition easy and smooth, but its test-bed high cost, low-speed braking torque is small, thus limiting the application.
This system was chosen as the eddy current unit load device, because of its external features and cost, reliability, accuracy decision.
Currently, the majority of domestic water vortex machine dynamometer, eddy current machine has a small amount of several major water-cooled, easy-to leakage, resulting in corrosion of the bearing parts, easy to magnetic flux leakage, constant speed control accuracy, and the volume weight, need a water cooling system and lubrication system inside the vortex, very easy to use, in northern China, especially in winter does not apply. More importantly, domestic water eddy current machine for almost all the engine power measurement of high-speed power absorption unit (maximum power absorption range of 1500 ~ 4000 r / min), does not apply to vehicle chassis dynamometer, which is the maximum power absorption range of 500 ~ 1000 r / min. The international production of this special low speed, high torque eddy current machine only company in Spain and France TELMA FRENELSA company, their product mix to air-cooled.
As the dynamometer torque and power measurement of the speed and load requirements to a large extent, considering cost, reliability, accuracy in the case we have chosen FRENELSA's F16-160-type air-cooled eddy current machine group 16, the absorption maximum torque speed of 750 r / min, vortex machine voltage is DC96V, current is 35A, the maximum absorption torque of 160 kg. The vortex machine constant high precision, volume weight, simple structure, easy to operate, do not need cooling water, and built-in thermocouple 160 ℃, can overheat when the automatic power-off, to avoid eddy current machine was burned.
Eddy current machine is a constant speed control accuracy of the dynamometer test one of the key factors, most of the domestic dynamometer does not really solve the problem. According to standard, constant accuracy should reach ± ??2 km / h (such as China GB86-94), but because of large mechanical movement of the system inertia, and inertia of different models is different from the same time, there are dead out of control, non-linear, lag reaction speed feedback in the difficulty of making the design of constant speed control has become one of the key.
Currently, we are to be addressed in several ways, one direct drive as far as possible, reducing the dead zone and hysteresis control response, and digital speed control and adaptive control to solve the different moment of inertia effects. In addition, two large closed-loop speed and current use of different sampling frequency in order to effectively control the vortex dynamics and the feedback current machine. Test proved to be stable to ± 0.5 km / h, is a standard 1 / 4.
Control process is as follows: the car began to accelerate, due to the speed difference between running speed and a larger set, using the experience of the control algorithm that is according to certain rules and gradually increase the resistance; Once the vehicle speed close to the set speed, adaptive control work. Because in the start-up phase, the running speed as soon as possible close to the set speed is the primary goal, and the last way in which speed is not stable in the set under consideration, the experience of control is simple and works well in control. The speed close to the set speed, the speed and stability the only objective, experience, control can not do anything at this time. The actual vehicle operating conditions is very complex, and the speed variation is difficult to predict, and thus the control of any form pre-set parameters are not always achieve the best control action, the effect of operating conditions and with the pros and cons of changing. Adaptive control is to adapt to similar conditions and developed, it can under the conditions and adjust the control parameters in order to achieve real-time optimal control.
Car in idle state, the different load conditions, different speeds and different road conditions in the case of the emissions are different, the measured data for vehicle maintenance is important, but more important is to determine whether emissions from vehicles qualified to provide a basis for the environmental protection departments to provide accurate detection and rich data material. The dynamometer with the exhaust gas analyzer can be in different working conditions under the conditions of vehicle emissions testing, testing standards fully in line with the introduction of a new national standard (GB14761-1999).
The following chassis dynamometer at constant speed, for example, analysis of measurement results.
Experimental conditions: the initial speed of 60 km / h, the termination rate of 80 km / h, speed step of 5 km, constant and stable point 5. Test vehicle for the Santana sedan.
In constant speed mode with exhaust gas analyzer, we carried out the engine output power, wheel torque and power output, transmission loss of power, CO, CO2, HC, O2, eight parameters were measured, and the speed, power, torque for real-time monitoring.
In this experiment, the wheel and experience the power output values ??match, the engine output power wheel power output of power and transmission losses and. Maximum power output of the corresponding wheel speed of 75 km / h. Transmission loss of power to test the vehicle drive power is an important parameter passing, it is directly related to the car's dynamic performance.
Multi-function chassis dynamometer is a motor transport and maintenance industry, comprehensive performance inspection stations, environmental protection, transportation (cars scrapped in the future will be according to their dynamic performance and emissions performance may be) and other necessary test equipment industry, with broad market prospects. By computer-controlled eddy current dynamometer load to achieve resistance simulation, different conditions can be measured vehicle dynamic performance and environmental performance (emissions performance), and has correction, the actual measurement data closer to the car when driving data. The dynamometer speed control through the adaptive control algorithm to improve the car's constant stability and achieve a dynamic performance and environmental performance of continuous measurement.
附 錄B
多功能汽車底盤測功機(jī)
隨著汽車工業(yè)的迅猛發(fā)展，交通事故及環(huán)境污染對人類生命的威脅越來越大，因而汽車檢測技術(shù)的重要性日益突出出來，各種檢測設(shè)備也應(yīng)運而生。作為大型實驗設(shè)備，汽車底盤測功機(jī)可以模擬汽車道路試驗的各種工況，完成汽車的經(jīng)濟(jì)性試驗、動力性試驗、排放性能評價與分析、可靠性試驗以及與汽車傳動系統(tǒng)有關(guān)的專項試驗。它在汽車試驗研究、產(chǎn)品開發(fā)和新車及在用車質(zhì)量檢測中是不可或缺的。使用汽車底盤測功機(jī)完成汽車試驗及各類型的質(zhì)量檢測與通常的道路試驗相比具有試驗速度快、精度高、費用低、數(shù)據(jù)穩(wěn)定、可比性好等優(yōu)點。
鑒于汽車底盤測功機(jī)的以上優(yōu)點，國內(nèi)許多廠家先后研制開發(fā)了一系列測功機(jī)產(chǎn)品，這些產(chǎn)品主要用于檢測軸重10 t以下的汽車底盤輸出功率，最大吸收功率為150 kW。檢測項目主要是：汽車底盤的輸出功率、驅(qū)動力、車速、加速性能、滑行性能、以及車速表和里程表的準(zhǔn)確性等等。
但是國內(nèi)測功機(jī)產(chǎn)品還有許多不完善的地方，亟待解決。例如：汽車在不同工況、不同負(fù)載等狀態(tài)下，其動力性能不能實現(xiàn)連續(xù)測量，控制系統(tǒng)、控制方法比較落后。本文正是針對這些不足，在控制系統(tǒng)、控制方法上進(jìn)行了改進(jìn)，實現(xiàn)了不同工況、不同負(fù)載的狀態(tài)下，對汽車動力性能進(jìn)行準(zhǔn)確可靠的連續(xù)測量，并且增加了排放的連續(xù)測量功能。此外，參照國外先進(jìn)技術(shù)及經(jīng)驗，利用計算機(jī)技術(shù)對汽車有關(guān)傳動損耗、滾動阻力、海拔高度、氣溫等參數(shù)進(jìn)行模擬和修正。
多功能汽車底盤測功機(jī)（以下簡稱測功機(jī)）是一種新型底盤測功機(jī)。該機(jī)的測量和控制系統(tǒng)是實現(xiàn)其強(qiáng)大功能的關(guān)鍵設(shè)備。
測功機(jī)檢測控制系統(tǒng)中的控制微機(jī)采用高性能的工業(yè)控制計算機(jī)，整個測控系統(tǒng)包括計算機(jī)、顯示器、鍵盤、鼠標(biāo)、打印機(jī)，輸入輸出端子板，多功能PC總線接口卡、可控硅及其控制電路，所有部件全部安裝在1．8 m高的標(biāo)準(zhǔn)19寸工業(yè)控制柜中。測控系統(tǒng)加上測功機(jī)的機(jī)械部分（臺架）構(gòu)成了整個測功機(jī)。測控系統(tǒng)通過臺架上的壓力傳感器、速度傳感器、氣動舉升機(jī)和電渦流機(jī)等裝置，完成對測功機(jī)的測量和控制。
多功能PC總線接口板是計算機(jī)和測量控制通道的接口設(shè)備，現(xiàn)場模擬信號的放大和模數(shù)轉(zhuǎn)換、開關(guān)量信號的測量都由它完成，該接口卡還能控制多個執(zhí)行機(jī)構(gòu)的動作，另外該卡還提供了用于頻率測量的計數(shù)器接口。
在臺架上汽車驅(qū)動輪帶動滾筒轉(zhuǎn)動，滾筒轉(zhuǎn)動經(jīng)光電解碼器產(chǎn)生脈沖輸出，接入多功能卡的計數(shù)器，測量速度和行駛距離。汽車在臺架上行駛時，其驅(qū)動能對滾筒的作用力經(jīng)電渦流機(jī)耦合在壓力傳感器上，由輸入通道將信號送入計算機(jī)，與速度信號結(jié)合可測量汽車的動力性能。在實際測量過程中，實測的速度信號與設(shè)定速度比較，根據(jù)偏差按一定的算法調(diào)整阻力（電渦流機(jī)勵磁電流），使車速能穩(wěn)定在給定值，完成恒速條件下各種數(shù)據(jù)的測量。
測功機(jī)的應(yīng)用軟件由測量控制程序、登錄程序和數(shù)據(jù)庫服務(wù)程序構(gòu)成，程序設(shè)計采用先進(jìn)的C/S（客戶/服務(wù)器）設(shè)計方法。測量控制程序和登錄程序是客戶端程序，它們與數(shù)據(jù)庫的數(shù)據(jù)交換是通過數(shù)據(jù)庫服務(wù)程序完成，數(shù)據(jù)庫結(jié)構(gòu)對用戶是透明的，方便本系統(tǒng)與其他機(jī)動車檢測設(shè)備或管理網(wǎng)絡(luò)連接。登錄程序完成用戶對車輛的基本信息、檢測項目的初始設(shè)定；測量控制程序是該系統(tǒng)的核心程序，其主要功能是完成對硬件信號的測量和控制、按登錄程序設(shè)定的檢測要求完成各項檢測任務(wù)，另外該程序還提供參數(shù)設(shè)定、檢測結(jié)果查詢、打印等輔助功能。
電渦流機(jī)又稱電渦流測功器，是基于渦流電流（物理學(xué)上也稱傅科電流）進(jìn)行工作的設(shè)備。它由定子和轉(zhuǎn)子兩部分組成。定子部分包括定子架和裝在上面的勵磁線圈。定子框架周圍有孔，勵磁線圈裝在孔內(nèi)。定子框架中心部分輪轂，借助兩個滾動軸承支撐在轉(zhuǎn)子軸上。轉(zhuǎn)子部分包括轉(zhuǎn)子軸和固定在該軸上的兩個轉(zhuǎn)子，兩個轉(zhuǎn)子分別位于定子部分的兩端，轉(zhuǎn)子軸可以被外力帶動而自由轉(zhuǎn)動。轉(zhuǎn)子的內(nèi)側(cè)端面與定子的端面保持很小的間隙，該間隙電磁學(xué)上稱為氣隙。該轉(zhuǎn)子的內(nèi)側(cè)面是十分光滑的平面，渦流電流就產(chǎn)生在這個光滑平面上。
電渦流機(jī)的勵磁繞組通入電流時，磁通經(jīng)定子、渦流環(huán)、氣隙、轉(zhuǎn)子構(gòu)成閉合磁路。當(dāng)汽車驅(qū)動輪帶動滾筒及電渦流機(jī)轉(zhuǎn)子旋轉(zhuǎn)時，由于磁通密度發(fā)生變化使轉(zhuǎn)子表面產(chǎn)生渦流電流，該渦流電流與磁場相互作用，產(chǎn)生反向制動力矩，使定子繞主軸軸線擺動。該制動力矩通過杠桿傳遞給壓力傳感器，由壓力傳感器給出相應(yīng)的電信號，經(jīng)計算處理后，可得出汽車瞬時的動力參數(shù)。調(diào)節(jié)勵磁電流大小，即可改變電渦流機(jī)的制動力矩，同時相應(yīng)改變汽車車速，不斷變化的勵磁電流與車速形成閉合環(huán)，并最終實現(xiàn)恒速或恒力下的功率測量。
電渦流機(jī)具有最大的速度和載荷范圍。此外它體積小，造價低，更適合于操縱自動化。交流電機(jī)（異步電機(jī)）具有最小的速度（800～1500r/min）和載荷范圍，穩(wěn)定性較差，小負(fù)荷具有很硬的特性。直流電機(jī)制動裝置具有很高的使用性能，操作方便，工況穩(wěn)定，過渡簡易且平穩(wěn)，但它的試驗臺造價高，低速制動扭矩小，因而限制了應(yīng)用。
本系統(tǒng)之所以選擇電渦流機(jī)作為加載裝置，是由于它的外特性及造價、可靠性、測量精度決定的。
目前，國產(chǎn)渦流機(jī)大部分為水力測功機(jī)，少量幾種電渦流機(jī)也主要為水冷式的，易漏水，導(dǎo)致軸承機(jī)件銹蝕，容易漏磁，恒速控制精度差，且體積重量大，需要一套供水冷卻循環(huán)系統(tǒng)及渦流機(jī)內(nèi)部潤滑系統(tǒng)，使用很不方便，在我國北方，冬季尤為不適用。更為重要的是，國產(chǎn)水力電渦流機(jī)幾乎全部用于發(fā)動機(jī)功率測量的高轉(zhuǎn)速功率吸收裝置（最大功率吸收范圍1500～4000 r/min），不適用于汽車底盤測功，后者最大功率吸收范圍為500～1000 r/min。國際上專門生產(chǎn)這種低轉(zhuǎn)速，大扭矩電渦流機(jī)只有西班牙的FRENELSA公司和法國的TELMA公司，他們的產(chǎn)品結(jié)構(gòu)為風(fēng)冷式。
由于測功機(jī)的扭矩和功率測量對速度和載荷范圍要求要大，在考慮造價、可靠性、測量精度的情況下我們選擇了FRENELSA公司的F16—160型風(fēng)冷16組電渦流機(jī)，其最大扭矩吸收轉(zhuǎn)速為750 r/min，渦流機(jī)電壓為DC96V，電流為35A，最大吸收扭矩為160 kg。該渦流機(jī)恒速精度高，體積重量小，結(jié)構(gòu)簡單，操作方便，勿需冷卻水，且內(nèi)置160℃熱電偶，可在過熱時自動斷電，避免渦流機(jī)被燒壞。
電渦流機(jī)的恒速控制是測功機(jī)測試精度的關(guān)鍵因素之一，國內(nèi)大部分測功機(jī)未真正解決好這一問題。按標(biāo)準(zhǔn)規(guī)定，恒速精度應(yīng)達(dá)到±2 km/h（如中國GB86—94），但由于機(jī)械系統(tǒng)運動慣量較大，且不同車型慣量不同，同時，存在失控死區(qū)、非線性、滯后反應(yīng)等調(diào)速反饋方面的難度，使得恒速控制成為設(shè)計中的重點之一。
目前，我們通過幾種途徑予以解決，一是盡量采用直接傳動，減小失控死區(qū)及滯后反應(yīng)，同時采用數(shù)字調(diào)速和自適應(yīng)控制等解決不同轉(zhuǎn)動慣量的影響。此外，大轉(zhuǎn)速及電流兩個閉環(huán)中采用不同的采樣頻率以便有效的控制渦流機(jī)動態(tài)及反饋電流。測試證明可以穩(wěn)定達(dá)到±0．5 km/h，是標(biāo)準(zhǔn)的1/4。
控制過程如下：汽車在開始加速時，由于運行速度與設(shè)定速度相差較大，采用經(jīng)驗控制算法即按一定的規(guī)律逐步增加阻力；一旦汽車運行速度接近設(shè)定速度，自適應(yīng)控制開始工作。因為在啟動階段，使運行速度盡快接近設(shè)定速度是首要目的，而最后以何種方式穩(wěn)定在設(shè)定速度則不在考慮之內(nèi)，經(jīng)驗控制是簡單易行且效果很好的控制方式。在運行速度接近設(shè)定速度之后，速度的穩(wěn)定成為唯一目的，此時經(jīng)驗控制就無能為力了。汽車的實際運行工況十分復(fù)雜，其速度變化規(guī)律難以預(yù)測，因而任何預(yù)先設(shè)定參數(shù)的控制形式都不可能一直發(fā)揮最佳控制作用，其效果的優(yōu)劣隨運行工況而不斷變化。自適應(yīng)控制正是為適應(yīng)類似的工況而發(fā)展起來的，它能夠根據(jù)工況而調(diào)整控制參數(shù)，以實現(xiàn)實時最佳控制。
汽車在怠速狀態(tài)下，不同負(fù)載狀態(tài)下，不同車速狀態(tài)下以及不同路況的情況下的排放都是不同的，測量到這些數(shù)據(jù)對于汽車維修保養(yǎng)很重要，但更為重要的是為判斷汽車排放是否合格提供依據(jù)，為環(huán)保檢測部門提供精確而豐富的數(shù)據(jù)材料。本測功機(jī)可以配合尾氣分析儀在不同工況的條件下進(jìn)行汽車排放的檢測，檢測標(biāo)準(zhǔn)完全符合新出臺的國家標(biāo)準(zhǔn)（GB14761—1999）。
下面以恒速底盤測功為例，分析一下測量結(jié)果。
實驗條件：起始速度60 km/h，終止速度80 km/h，速度步長5 km，恒速穩(wěn)定點為5個。試驗車為桑塔那轎車。
在恒速狀態(tài)下配合尾氣分析儀，我們進(jìn)行了發(fā)動機(jī)輸出功率、輪輸出扭矩及功率、傳動損耗功率、CO、CO2、HC、O2等8個參數(shù)的測量，并對速度、功率、扭矩進(jìn)行了實時監(jiān)控。
在本試驗中，輪輸出功率與經(jīng)驗數(shù)值相符，發(fā)動機(jī)輸出功率為輪輸出功率與傳動損耗功率之和。輪輸出最大功率對應(yīng)的速度為75 km/h。傳動損耗功率是檢驗汽車驅(qū)動功率是否合格的重要參數(shù)，它直接關(guān)系到汽車的動力性能。
多功能汽車底盤測功機(jī)是汽車運輸維修業(yè)、綜合性能檢測站、環(huán)境保護(hù)、交通（今后在用車報廢將按其動力性能及排放性能而定）等行業(yè)所必需的測試設(shè)備，具有廣闊的市場前景。通過計算機(jī)控制電渦流測功器加載實現(xiàn)阻力模擬，可以測量不同的工況下汽車動力性能和環(huán)保性能（排放性能），并具有修正功能，測量數(shù)據(jù)更接近汽車實際行駛時的數(shù)據(jù)。本測功機(jī)通過自適應(yīng)控制算法控制車速，提高了汽車的恒速穩(wěn)定性，并且實現(xiàn)了動力性能和環(huán)保性能的連續(xù)測量。