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1VIRTUAL INSTRUMENT AND FREQUENCY CONVERSIONTECHNOLOGY-BASED BRAKE TEST SYSTEMBrake is widely useful and very important safety assuring equipment. The aim of Brake test system， which is based on visual instrument and frequency changing technology， is to integrative measure and analyze the performance and quality of the brake.This paper mainly introduces the principle， composing，function and features of the brake test system. And from the point of view of the principle of Visual Instrument （VI ） technology， a test system， based on the VI and frequency changing technologies and consist of frequency changing drive and control sub-system and measuring sub-one， is constructed. With the test system the performances and braking course could be auto controlled and measured to the brakes which includes disc and drum ones. And the measuring and control software is programmed with the LabVIEW published by American NI Corporation， USA.Then data real time acquisition， processing， displaying and recording will be realized. The test system also has the functions of voltage adjusting， rotating speed control， load regulating， JC value setting， temperature measuring， and braking route and time memorizing and analyzing. It will be very important for meaning and exciting boosting effect to advance quality and capabilities of the brakes and the security of equipments and system which have adopt the brakes.1 Operating principlesAccording to the principle of work and power， the change of kinetic energy in the moving of objects equals to the full power of the force act on the object in that process.The energy obtained by brake to be tested：Therefore， it is feasible to use combined inertial flywheels to simulate rotating inertia of crane hoist and its transmission components to test the performance and quality of the brake.According to the moment of momentum theorem：Tb·t =Ji·ω （1）When Tb is fixed， tb can be controlled through combinations between Ji and ω differently. Brake drum or plate， which will be measured， and combined inertial flywheels for loading on are driven to rotate by AC frequency conversion motor （or DC one， which will not bedealt with in this article carefully）. According to the principles shown in the formula 2（1） ， we can simulate actual processes of brakes fitted on lifting and transport machineries， engineering ones， mining ones and construction ones by changing the technical specification duty JC， the flywheel's inertial moment Ji and motor's rotational speed ni.When detected brakes work in simulation cycle and brake repeated， infrared thermoscopes and torque sensors， and other sensors will record braking shown in the heat， braking torque，braking time and brake speed parameters.2The composition and structure of the brake test systemThis test system is intended to achieve the performances of drum and disc brakes and has following functions：（1） Brake replacementAccording to different type of brakes the corresponding base will be chosen and brake position could be adjusted using electric slide test-bed；（2） Multi-level loadingWe can simulate the actual loading on brakes in a crane with different combined flywheels. The test system adopts manual hydraulic system composed by a three-position four-way hand-operated direction valve， a relief one and their accessories， and it is operation saving and convenient to replace flywheels.（3） Regulation the rotational speed n （or ω）It can be realized by changing frequency supplied to the AC motor. When braking torque is very large， such as 10000Nm， it should be appropriate for regulating initial brake speed upward 1000r/min to minimize rotating inertia possibly.（4） Braking frequency adjustmentBased on actual needs braking frequency can be confined in a range of 1~4 times per minute.（5） Braking torque measurementThere are three methods：a） Direct measurement via torque sensors：Rotational speed and torque sensor will be installed between the detected brake drum or plate and inertial flywheel plates.Dynamic braking torque of detected brake will be directly measured， shown in Fig.1 and Fig.2. According to the scope of braking torque of detected brakes， two or three rotational speed and torque sensors should be prepared for testing torque to meet the accuracy requirements；b） Indirect parameter measurement：3Based on the rotating inertia and braking time we can get brake torque using mathematical relationship between these parameters， as shown in Fig. 2.c） Indirect measurement by pedestal-force：The pressure sensors are installed under the base where detected brake are fixed to feel the forces given by brake， and then to obtain brake torque.The second approach has small investment， simple structure and no torque sensors which mean not considering related troubles of changing torque sensors. But the procedure tocalculate torque is complex， and accumulating total errors would be larger and then the result accuracy will be low.The third way has the advantage of the replacement of sensors is easier and no special requirements for sensors installing precision. It is still an indirect measurement but the procedure is less than that in the second method and that means the cumulative errors relatively is smaller. And visible shortcoming is poor dynamic response.（6） Automatic controlExcept to manual operation test system is also programmed control.（7） MonitoringBraking frequency， initial braking speed， the aggregate braking number， moment， time and so on will be shown automatically.（8） Automatically data acquisition and processingThe curve describing braking torque， time and speed could be drawn automatically by means of computer software while detected brake is measured in dutycycle operation. Therefore， in response to the way to test braking torque the system can be divided into three ones of that with torque sensor such as Fig.1 and 2 above， that without torque sensor such as shown in Fig.3 and that of pedestal-power measurement without torque sensor， as shown in Fig.4. The test system is mainly composed of AC frequency conversion transmission system， flywheels loading system， rotational speed and torque sensors， base which to fix drum or plate brakes， adjustable DC power supply， detected brakes and test and control system.In addition to the above functions， the system could test following performances of the brakes：a） Release performance：This is tested under the conditions of 85%Ve and rated load，adjusting voltage via booster 4devices；b） Close performance：This is tested under the conditions of rated voltage Ve and 50% of rated loading；Otherwise， the following performances could also be tested：1） Structural performances：a） Ability of brake shoe's position following drum；b） Assembly for keeping gaps between drum and shoes equalling；c） Lubricating.2） Other items：a） Contact area；b） Spring testing；c） Braking linings and shoes gap；d） Pin's hardness.3 AC frequency conversion adjusting speed systemCompared with DC motor， the AC motor has simple and compact structure， little maintenance workload， high efficiency， small rotating inertia and quick dynamic response，and it could be made of high-voltage， large capacity and high speed. Currently， AC motor has trend to replace DC one in the field of adjusting speed transmission.Generally speaking， there are many kinds of motors which could be applied to diverse types of converter-driven， and which are roughly divided into ordinary AC motor， special one and dedicated one. The frequency conversion adjusting speeding system is composed of frequency converter anddedicated lift motor. To the ordinary asynchronous motor， the following factors should be considered while to determine their capacity：（1） Chosen motor capability should be greater than the power load needed；（2） Compared with needed load pull-in torque the greatest torque that motor exports should have sufficiently surplus volume；（3） Even supply voltage is lower 10% than rated value， motors can export needed torque also； （4） Considering the life length of motor it should running in the specified temperature scope；5（5） Because of transmission rate of the transmission system，efficiency and load fluctuation， the motor power should have enough surplus volume；（6） Against load nature， it is necessary to choice a suitablemotors operating modes such as continuous service system， short-term operation and duplication system. In the AC adjusting speed control system with frequency converter motor's slowdown is achieved by reducing the output frequency of the converter. When motors need slow down faster than the rate of free deceleration， underspeed of converter output frequency might be ran-up and the speed which is corresponding to that frequency is lower than the actual rotational speed of motor， and motor will be regenerative braking. In such cases， asynchronous motor will be an asynchronous generator， and load mechanical energy will be converted to electrical energy and then feedback to the converter. However， when the back feed is overload， overvoltage protection circuit of converter will work to cut converter's output and motors will be freely slowdown instead a rapid speed-down. To avoid above phenomenon， that is， to consume the energy in other parts of the DC circuit without causing voltage rise in the voltage-fed converter， regenerating braking circuits （braking resistors） are normally used and the energy fed back to the DC circuit will consumed in the form of heat. For the test system， it is apparently that braking resistances are not necessary because of the usage of brake for braking deceleration. It is necessary to define surplus capacity of motor or converter on the basis of practical situation. And on the case of ensuring to meet requirements of driving system performance， energy consumption or economic factors should be considered， and overall system has a smaller investment and maximum benefits.6基于制動試驗臺的虛擬儀器與變頻技術(shù)制動器是廣泛有益的和非常重要的安全保障設(shè)備。制動測試系統(tǒng)的目的是綜合衡量和分析制動試驗系統(tǒng)的性能和質(zhì)量的剎車，組成，功能。從目視儀器理論的角度來看，基于 VI 和頻率不斷變化的技術(shù)和包括頻率變化的驅(qū)動和控制子系統(tǒng)和測量分之一構(gòu)成的。隨著測試系統(tǒng)的性能和制動過程可自動測量，以控制和剎車，其中包括光盤和鼓的。和測量和控制軟件的設(shè)計與 LabVIEW 的出版的美國公司-美國。然后數(shù)據(jù)實時采集，處理，顯示和記錄一定會實現(xiàn)。測試系統(tǒng)還具有功能的電壓調(diào)整，轉(zhuǎn)速控制，負(fù)荷調(diào)節(jié)，巴埃納價值設(shè)定，溫度測量，和制動路線和時間背誦和分析。這將是非常重要的意義和令人激動的推動作用，以推進素質(zhì)和能力的剎車和安全的設(shè)備和系統(tǒng)已經(jīng)采取剎車。1.工作原理根據(jù)工作原理和功率的變化動能在移動的物體等于全部力量采取行動，該部隊的目標(biāo)過程中取得的制動能量進行測試：因此，它是可行的使用相結(jié)合，模擬慣性飛輪轉(zhuǎn)動慣量的起重機吊重機及其傳動部件的性能測試和質(zhì)量制動。根據(jù)動量矩定理：Tb·t =Ji·ω （1）當(dāng) TB 是固定的，TB 是可以控制的，通過組合之間籍和 ω 不同，制動鼓或板，這將是衡量，并結(jié)合慣性飛輪裝載的驅(qū)動旋轉(zhuǎn)的交流變頻電機。根據(jù)原則表現(xiàn)在公式（1） ，我們可以模擬實際過程中剎車安裝在起吊和運輸機械，工程的，采礦業(yè)和建筑業(yè)的是通過改變技術(shù)規(guī)范責(zé)任巴埃納，飛輪的慣性時刻姬和電機轉(zhuǎn)速鎳。當(dāng)工作中發(fā)現(xiàn)剎車和制動仿真周期重復(fù)，其他傳感器將記錄中顯示的制動熱，制動力矩，制動時間和制動的速度參數(shù)。2.剎車測試系統(tǒng)的組成和結(jié)構(gòu)該測試系統(tǒng)是為了實現(xiàn)表演鼓和盤式制動器，并以下職能：（1）更換制動根據(jù)不同類型的剎車相應(yīng)的基地將選擇和剎車的位置可以調(diào)整使用電動滑試驗臺；（2）多層次載入中我們可以模擬實際負(fù)荷制動器在起重機不同組合飛輪。該測試系統(tǒng)采用手動液壓系統(tǒng)組成，由一個三人立場四路手操作的方向閥，救濟及其配件之一，它是操作方便，節(jié)約和替代飛輪。7（3）規(guī)例轉(zhuǎn)速 n它可以實現(xiàn)通過改變頻率提供給交流電動機。當(dāng)制動力矩非常大，如 10000Nm ，應(yīng)該適當(dāng)調(diào)節(jié)初始制動速度向上 1000r/min 盡量轉(zhuǎn)動慣量可能。（4）制動頻率調(diào)整根據(jù)實際需要制動頻率可以限于在 1 ? 4 倍，每分鐘。（5）制動力矩測量，有三種方法：a) 直接測量通過扭矩傳感器：轉(zhuǎn)速和扭矩傳感器將被安裝與檢測制動鼓或板和慣性飛輪板.動態(tài)制動力矩的檢測制動將直接測量，顯示在圖 1 和圖 2 。根據(jù)范圍的制動力矩的檢測剎車，兩個或三個轉(zhuǎn)速和扭矩傳感器應(yīng)準(zhǔn)備用于測試的扭矩，以滿足精度要求；b) 間接參數(shù)測量：基于轉(zhuǎn)動慣量和制動時間，我們可以用數(shù)學(xué)制動力矩這些參數(shù)之間的關(guān)系，如圖2 所示c) 間接測量的基座力：壓力傳感器安裝在基地發(fā)現(xiàn)剎車固定感受到部隊給予剎車，然后獲得制動力矩。第二個辦法投資少，結(jié)構(gòu)簡單，沒有扭矩傳感器，這意味著不考慮相關(guān)故障的改變扭矩傳感器。但是程序計算扭矩是復(fù)雜的，并積累總額將是更大的錯誤，然后將結(jié)果準(zhǔn)確性低。第三條道路的優(yōu)點是更換傳感器更容易，也沒有特殊要求的傳感器安裝精度。它仍然是一種間接測量的程序，但低于第二方法和手段的累積誤差相對較小。和明顯的缺點是窮人的動態(tài)響應(yīng)。（6）自動控制除手動操作測試系統(tǒng)也編程控制。（7）監(jiān)測制動頻率，初始制動速度快，制動人數(shù)的總和，目前，時間等將自動顯示。（8）自動數(shù)據(jù)采集與處理曲線描述制動力矩，時間和速度可以得出自動通過計算機軟件，同時檢測制動測量占空比工作。因此，在應(yīng)對方式的制動力矩測試系統(tǒng)可分為三個一的，在扭矩傳感器，例如圖 1 和 2 段，如果沒有扭矩傳感器，如在圖 3 所示和底座，功率測量無扭矩傳感器，圖 4 所示。該測試系統(tǒng)主要由交流變頻傳輸系統(tǒng)，飛輪加載系統(tǒng)，轉(zhuǎn)速和扭矩傳感器，基地修復(fù)剎車鼓或板，可調(diào)直流電源供應(yīng)器，檢測剎車系統(tǒng)以及測試和控制系統(tǒng)。除了上述功能，該系統(tǒng)可以測試以下性能剎車：8a) 排放性能這是測試的條件下， 85 ％維生素 E 和額定負(fù)載，調(diào)整電壓通過增壓裝置；b) 關(guān)閉性能：這是測試的條件下，額定電壓 E 和 50 ％的額定載荷； 否則的話，下面的表演也可以進行測試：（1）結(jié)構(gòu)功能：a) 制動蹄功能b) 使輪轂和制動蹄匹配c) 潤滑（2）其他項目a） 接觸區(qū)b） 機械裝置測試c） 剎車片和制動蹄間距d） 引腳的硬度。3.交流變頻調(diào)速系統(tǒng)與直流電動機，交流電動機簡單，結(jié)構(gòu)緊湊，維修工作量小，效率高，轉(zhuǎn)動慣量小，快速動態(tài)響應(yīng)，而且可以取得的高電壓，大容量和高速度。目前，交流電機的發(fā)展趨勢，以取代直流一個領(lǐng)域中的調(diào)整高速傳輸。一般而言，有許多類型的汽車可以適用各種不同類型的轉(zhuǎn)換器驅(qū)動，這是大致分為普通交流電機，特殊和專用的。變頻調(diào)整加速系統(tǒng)是由變頻器和汽車專用升降機。普通異步電動機，下列因素，而應(yīng)該考慮，以確定它們的能力：（1） 選擇電動機能力應(yīng)大于電力負(fù)荷需要；（2） 與需要負(fù)載拉在扭矩最大扭矩電機出口應(yīng)該有足夠的剩余量；（3） 即使是較低的電源電壓超過額定 10 ％的價值，汽車出口也需要扭矩；（4） 考慮到生命長度的電機應(yīng)運行在指定的溫度范圍；（5） 由于傳輸速率的傳輸系統(tǒng)，效率和負(fù)荷波動，電動機功率應(yīng)該有足夠的剩余量；（6） 對負(fù)載性質(zhì)，有必要選擇一個合適的汽車操作模式，如連續(xù)的服務(wù)體系，短期操作和重復(fù)的系統(tǒng)。在交流調(diào)速控制系統(tǒng)變頻調(diào)速電機的減速是通過降低輸出頻率的轉(zhuǎn)換器。當(dāng)汽車需要放慢速度快于自由減速，低速轉(zhuǎn)換器的輸出頻率可然和速度是對應(yīng)的頻率低于實際轉(zhuǎn)速電機和電機將再生制動。在這種情況下，異步電動機將是一個異步發(fā)電機和負(fù)9荷將機械能轉(zhuǎn)換成電能，然后反饋給轉(zhuǎn)換器。然而，當(dāng)回到飼料是超負(fù)荷，超電壓保護電路的轉(zhuǎn)換器將努力降低轉(zhuǎn)換器的輸出和汽車將是自由經(jīng)濟放緩而不是迅速減速。為了避免上述現(xiàn)象，也就是說，消費的能源中其他部分的電路，而不會造成直流電壓上升電壓饋轉(zhuǎn)換，再生制動電路（制動電阻）通常用于和能源反饋到直流電路將消費形式的熱量。為測試系統(tǒng)顯然，這制動電阻沒有必要的，因為使用的剎車制動減速。有必要界定的機動能力過?；蜣D(zhuǎn)換的基礎(chǔ)上，實際情況。和確保的情況下，以滿足需求的驅(qū)動系統(tǒng)的性能，能耗或經(jīng)濟因素，應(yīng)考慮和整體系統(tǒng)具有較小的投資，獲得最大的利益。