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譯文題目：Design of Anti-pinch of ElectricWindow
on the Threshold of Automatic Configuration
基于自動(dòng)控制臨界值的電動(dòng)車窗防夾設(shè)計(jì)
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Design of Anti-pinch of ElectricWindow
on the Threshold of Automatic Configuration
Abstract ：In this paper, the design of anti-pinch of electric window is based on the current feedback principle, when the motor load increases, the electrical current will increase, too. Using a smart chip with current feedback function to determine whether the window is blocked while it upwards. This paper presents an algorithm which will configure the current threshold automatically. It is an improvement on Anti-pinch of Electric Window in Vehicles.
Key words: Threshold of Automatic Configuration,Anti-pinch of Electric Window, Feedback current
1. Introduction
Nowadays many cars installed electrical Windows.By the use of electrical windows, on the one hand, it reduce the labor intensity of drivers and passengers, with convenient operation. On the other hand, because of electrical windows rising fast, it always induced clamp accident. Electrical windows with anti-pinch function has become a necessity. When the window rising around an obstacle, it can be back to return to the bottom, thus avoiding accidents. Currently, there are two types of methods used to implement anti-pinch function: One way is using the sensor switch(such as Infrared sensor and Hall sensor).This method is generally relatively high cost, and this paper will not discuss it in detail. Another is that with the current feedback through the use of smart power chips. In the solution for anti-pinch this paper introduced, there are set-bottom switch and set-top switch in the window control mechanisms, achieving anti- pinch function by AD sampling current. Current feedback to achieve anti-pinch function is based on the principle that as the motor load increases, the motor current will increase accordingly[1][2].
2. Design Principles
For the power window anti-pinch systems, detecting the value accurately is the key to achieve the anti-pinch function. Due to the cost price of designconstraints and door style, it is difficult to adopt infrared and mechanical sensors technology in other areas widely to achieve anti-pinch. Today, the mainstream method to achieve anti-pinch function are either detecting motor current or using Hall sensor to detect motor current. Both methods have the common features that, through detecting the force indirectly when window be contact with obstacles to achieve the anti-pinch function, it has the advantage that the hardware is relatively simple, of low cost and high reliability. This work discusses the method which needs to detect the motor current, and through this method, it can determine whether the force is over the limit, and without the need for Hall sensors can accurately determine whether there are obstacles blocking the windows[3].
This is the relationship diagram between the motor resistance and motor current value, as depicted in Fig.1-1.
Figure 1-1 the relationship diagram between the motor resistance and motor current value
This is the relationship diagram between the motor resistance and motor current value, as depicted in Fig.1-1.
As shown in Fig.1-1, there exists linear relationship between the suffered force and the current value. When the suffered force increasing, the current increases accordingly, indicating that the resistance of the window is increasing and may have encountered the obstacles. Therefore, by detecting the motor current, we can learn the force the motor suffered exactly, in order to achieve the anti-pinch function.
Normal load on the motor, that is the value of the force under Fnormal feedback on the current value of port AD Inormal. When the motor is to withstand the resistance Fmax, the port AD feedback current value is Imax. To achieve the anti-pinch function, it is assumed that it encounter the obstacle when the AD sample value exceeds the AD sample value with force value Fnormal＋100N(100N is presented by FMVSS118 safety norms the United States).
Only overcoming gravity, friction and all kinds of interference, electric window switches can achieve anti-pinch. But if one of these value is too high, it will affect the anti-pinch function. And if it needs to determine whether it encounters obstacle accurately, or it reached the top or bottom, this work adopt a set top switch and bottom switch, that spring switch is triggered by pressure during the window ascent. It will ignore the data sampled at AD port, and assuming that the window reaches the bottom or top.
Even having added the reach-top switch and reach-bottom switch, for each car, because every window in the process of lifting the resistance Fnormal bear is not same, so that it will inevitably lead to the data AD sampled is different. And with the car in the course of continuous wear and aging of the device will also lead to changes in the threshold current value.
In the past, anti-pinch windows are achieved using AD for each car AD parameters need to be measured, and then caught the configuration of the current threshold, which brought a lot of maintenance.
3. Implementations
In order to solve the problem mentioned above, this work presents a current threshold auto
configuration program, to replace the previous fixed threshold, which greatly simplifies the system installation and testing. A similar approach can be used to find the threshold, that when the motor is under the pressure value of ,the current value sampled from AD can be thethreshold. This current value can be approximately calculated by as the formula. If only sampling the value once, the error is relatively large, so the average methodcan be used to offset the margin of error. After the first installation of windows, the first initial value is set, then adjusting the data automatically according to the history and present status.
In his work the historical data will be stored in the MCU's flash, testing Ntest times.The the average threshold current and the implementation of testing procedures logo Ftest . When the first installation or turn on testing window switch, window will lift up and down automatically, using the end top switch set to test Inormal_i and Imax_i value and calculate Iclip_i. After the number of Ntest tests, is calculated. At this time the results Ntest and are stored in Flash as a historical reference data.
To reflect the changes in threshold current, in process of using the car, due to constant wear and aging of the devices, it is necessary to adjust the data sampling, We can treat changes in threshold current in each lifting of window as a data sampling. When the window is not top or bottom set, we treat the current sampling as Inormal, and then find the mean of several samples as.After the switch is set to top or bottom, maintain operation of the motor 10ms, treat the current after 10ms as Imax. Then calculate the threshold current of the current with
. However, in order to prevent the sampling data with large deviations, weighted average method is used to offset the deviation, when calculate the new threshold current with and replace the original value in the flash memory with the new value value [3] .
The value of the threshold current changes with theNtest, as depicted in Fig.2-1
Figure 2-1. Influence of Ntest on
Ntest value is determined according to different models and different application environment. When Ntest greater value, the more decisive role in the historical data, current threshold changes with the environmental change more slowly, better stability. When Ntest is smaller, the current data are more bigger role, the current threshold of the current environment will be more sensitive, but the stability deteriorates.
The method of Dynamic Configuration threshold current value effectively overcomes the fixed threshold current value of the anti-pinch shortcomings, improve the accuracy of the anti-pinch windows. When the current value sampled Iad>Iclip ,it assumes that there is an obstacle, and at this point the window lift switches will be invalid, and the motor will drive down the windows some distance away in order toavoid accidents.
4. System Design
This paper is to achieve anti- pinch function by AD sampling current using Smart Power ICs. Current feedback to achieve anti-pinch function is based on the principle that as the motor load increases, the motor current will increase accordingly. The MC33887 is a monolithic H-Bridge Power IC with a load current feedback feature making it ideal for closed-loop DC motor control. It has a feedback output for real time monitoring of H-Bridge high-side current to facilitate closed loop operation for motor speed and torque control. So MC33887 is a good choice.
Hardware consists of MC68HC908GR8, MC33689, MC33887 and MC33884[4-7].The MC33689 is an integrated power management chip with LIN driver module, and the MC33887 is a monolithic H-Bridge Power IC with a load current feedback feature, and theMC33884 is an integrated Smart switch chip, and the MC68HC908GR8 is a 8-bit microcontroller. This is a logical connection diagram between the chip, as depicted in Fig.3-1.
Figure 3-1.Hardware Design of Window module
In this work, the MC33887 can pass the current sampled by AD through FB output to MCU, then MCU determines whether there are obstacles through the value of the current. When the current value is greater than Iclip, it can be assumed that there is an obstacle.
5. Conclusions
Window lift system is an extremely complex system, that the environment, machinery and many other factors will impact the operation of the automatic windows. In other countries, the anti-pinch power windows product research and application has been for decades, and the technology is not a matter.But in china, because Automobile electronic starts lately, the technology remains a challenge. This paper analyzes the method that through the motor current to achieve anti-pinch electric function. As each has a separate ECU electric window control, in a damaged condition, the other three can still work, increasing the system reliability and safety. This method to achieve anti-pinch function through the motor current feedback can reduce the system cost effectively.
Acknowledgement
This work is supported by the National Natural Science Foundation of China under grant No. 60903011, Natural Science Foundation of Zhejiang province under grant No.Y1100689, Science and Technology Department of Zhejiang ProvinceFoundation under grant No. 2010C31122.
References
[1] Atmel.AVR480:Anti-Pinch System for Electrical Window.2006.
[2] Chen Zhaolong,Fan Qingbo.The development of jamproof glass lifter based on freescale single chip
machine(SCM)[J].chaohu college journal No.3,Vol.8.
[3] Xie Youhua, Yin Chengliang, Shu Jie.Application of LIN Bus in Power Window System Controlling. Control&Automation.2008,24(5).
[4] Freescale. MC9S08AW16 Data Sheet.Rev.2.
[5] Freescale. MC33689 Data Sheet .Rev.2.
[6] Freescale. MC33887 Data Sheet.Rev.2.
[7] Freescale. MC33993 Data Sheet.Rev.
基于自動(dòng)控制臨界值的電動(dòng)車窗防夾設(shè)計(jì)
摘要：本文中，設(shè)計(jì)的電動(dòng)車窗防夾原理是基于電流反饋原則進(jìn)行，當(dāng)電機(jī)負(fù)載增加時(shí)，電路中電流也相應(yīng)增大。利用小型芯片將電流反饋形式放大，用以判斷車窗在上升過(guò)程中是否被阻礙。本文中描述了一種根據(jù)電流臨界值自動(dòng)控制的運(yùn)算法則，將有利于提高電動(dòng)車窗防夾系統(tǒng)在汽車上的運(yùn)用。
關(guān)鍵詞：自動(dòng)控制臨界值，電動(dòng)防夾車窗，電流反饋
1引言
今天，越來(lái)越多的汽車都配置了電動(dòng)車窗。使用電動(dòng)車窗一方面可以降低駕駛員的勞動(dòng)強(qiáng)度，給予乘客更加舒適方便的操作；但另一方面，隨著電動(dòng)車窗使用量的增加，也經(jīng)常伴隨著夾傷等安全事故。電動(dòng)車窗具備防夾功能也逐漸成為必須配置，當(dāng)車窗自動(dòng)上升過(guò)程中碰到障礙物時(shí)能夠自動(dòng)下降至最低處，這樣就可以避免安全事故的發(fā)生。目前，比較普遍的有兩種方式用以實(shí)現(xiàn)防夾功能：一種方法是運(yùn)用傳感開(kāi)關(guān)（比如紅外線傳感器和霍爾傳感器）這種方法相較普遍方法而言成本較高，所以本文中將不再對(duì)此方法做過(guò)多的贅述。另外一種方法是運(yùn)用小型功率芯片電流反饋的方法，在本文中提出的解決防夾方案中，在車窗的機(jī)械控制系統(tǒng)中設(shè)定一個(gè)頂部開(kāi)關(guān)和一個(gè)底部開(kāi)關(guān)，通對(duì)AD電流進(jìn)行監(jiān)測(cè)以實(shí)現(xiàn)防夾功能。電流反饋實(shí)現(xiàn)車窗防夾功能的基本原理是：電機(jī)負(fù)載增加時(shí)，通過(guò)電機(jī)的電流也隨之相應(yīng)增大[1][2]。
2設(shè)計(jì)原則
對(duì)于電動(dòng)防夾車窗，精確實(shí)現(xiàn)防夾功能是體現(xiàn)其價(jià)值的關(guān)鍵。由于設(shè)計(jì)成本和車門型式的約束，很難通過(guò)在其它空間布置紅外線和機(jī)械傳感器而實(shí)現(xiàn)防夾。今天，比較廣泛運(yùn)用的方法是檢測(cè)電機(jī)電流或使用霍爾傳感器監(jiān)測(cè)電機(jī)電流。兩種方法都有共同的特點(diǎn)，即間接的監(jiān)測(cè)當(dāng)車窗遇到障礙物時(shí)產(chǎn)生的力，從而實(shí)現(xiàn)防夾功能，這樣使得硬件設(shè)計(jì)更加簡(jiǎn)單，成本更低、可靠性好。這項(xiàng)研究討論的方法是在不運(yùn)用霍爾傳感器的基礎(chǔ)上，通過(guò)監(jiān)測(cè)電機(jī)電流從而得出窗阻力是否達(dá)到設(shè)定的最低值，用以判斷車窗在上升過(guò)程中是否遇到障礙物[3]。
電機(jī)受的阻力與電機(jī)電流值關(guān)系如圖1-1所示：
圖1-1 電機(jī)阻力與電流值關(guān)系圖
如圖1-1所示，車窗玻璃上升過(guò)程中受到的阻力與電機(jī)反饋電流程線性關(guān)系。當(dāng)阻力增大時(shí)，電機(jī)電流相應(yīng)的增大，表明需要使車窗繼續(xù)上升的力增加，可能是遇到障礙物阻擋。因此為了實(shí)現(xiàn)自動(dòng)防夾功能，我們可以監(jiān)測(cè)電機(jī)電流的變化從而可以精確的掌握此時(shí)電機(jī)承受了多大的阻力。
當(dāng)電機(jī)在正常負(fù)載情況時(shí)，其正常承受的作用力通過(guò)AD轉(zhuǎn)換接口變反饋的值為Fnormal，電機(jī)達(dá)到其承受的最大阻力Fmax時(shí)，通過(guò)AD轉(zhuǎn)換接口反饋的回來(lái)最大的電流值Imax。為了實(shí)現(xiàn)防夾功能，設(shè)定車窗上升時(shí)通過(guò)AD轉(zhuǎn)換接口反饋回來(lái)的力超過(guò)車窗普通上升力+100 N時(shí)，則表明遇到了障礙物（100N的力值是根據(jù)美國(guó)安全規(guī)范條列FMVSS118標(biāo)準(zhǔn)執(zhí)行）。
只有克服車窗在自動(dòng)上升過(guò)程中的重力、摩擦力和其他各種因素的干擾，電動(dòng)車窗開(kāi)關(guān)才能實(shí)現(xiàn)防夾，如果其中任意一項(xiàng)值太高，將會(huì)影響電動(dòng)車窗防夾功能。如果需要準(zhǔn)確的判定是遇到障礙物還是到達(dá)頂部或底部，還需要設(shè)置一個(gè)頂部開(kāi)關(guān)和底部開(kāi)關(guān)，當(dāng)車窗上升至頂部/下降至底部，開(kāi)關(guān)在承受一定的壓力后被觸發(fā)，此時(shí)電流值的增大則會(huì)被AD轉(zhuǎn)換接口忽略。
因?yàn)槊總€(gè)車窗在上升過(guò)程中承受的阻力不同，所以不可避免的導(dǎo)致監(jiān)測(cè)的AD信號(hào)不同，甚至需要在每個(gè)車窗處增加頂部開(kāi)關(guān)和底部開(kāi)關(guān)。且隨著汽車不斷的磨損和老化過(guò)程中依然需要不斷的修正設(shè)定的電流臨界值。
以往，AD轉(zhuǎn)換器被用在每個(gè)具有電動(dòng)防夾車窗的汽車上，且AD轉(zhuǎn)換器參數(shù)需要測(cè)量，然后捕捉當(dāng)前的電流臨界值，這樣會(huì)帶來(lái)大量的維護(hù)和維修。
3安裝及過(guò)程
為解決上述問(wèn)題,本論文提出了一種自動(dòng)控制臨界值的程序,以替換之前的或臨界值配置,此工作極大的提高了系統(tǒng)的安裝和測(cè)試。采用類似逼近的方法來(lái)查找臨界值，當(dāng)電機(jī)運(yùn)行于低于壓力值Fnormal+（Fmax-Fnormal）/3時(shí)，從AD所取的當(dāng)前樣本值可以被認(rèn)為是當(dāng)前臨界值。此所取的當(dāng)前樣本值可以采用下面的的公式來(lái)進(jìn)行近似計(jì)算 Iclip~Inormal+（Imax-Inormal）/3 。當(dāng)樣本數(shù)為1時(shí)，誤差值將會(huì)被放大，因此采用計(jì)算平均值的方法來(lái)減小誤差。當(dāng)初次安裝該車窗時(shí)，所設(shè)定的初始值會(huì)根據(jù)歷史和當(dāng)前狀態(tài)進(jìn)行自動(dòng)調(diào)整。
在其工作狀態(tài)下歷史數(shù)據(jù)會(huì)被存儲(chǔ)在閃存MCU內(nèi)，并測(cè)試N次。當(dāng)前平均閥值電流為，測(cè)試程序的標(biāo)志Ftest會(huì)生效。 當(dāng)首次安裝或打開(kāi)測(cè)試車窗時(shí)，車窗會(huì)自動(dòng)上升和下降，使用頂置開(kāi)關(guān)設(shè)置測(cè)試值Inormal 、Imax并計(jì)算值Iclip_i。當(dāng)測(cè)試N次后，根據(jù)公式會(huì)得到計(jì)算值。測(cè)試結(jié)果Ntest和會(huì)被存儲(chǔ)于閃存，以替代所涉及的原始值。
為響應(yīng)臨界值電流的變化，在車輛使用處理過(guò)程中，由于持續(xù)的磨損和設(shè)備的老化，有必要對(duì)樣本數(shù)據(jù)進(jìn)行調(diào)整，我們可以對(duì)每一次的車窗上升數(shù)據(jù)進(jìn)行變化處理并以此作為樣本數(shù)據(jù)。當(dāng)車窗不在最高或最低時(shí)，我們將當(dāng)前樣本數(shù)據(jù)作非正常處理，并找到樣本數(shù)據(jù)的平均值作為當(dāng)開(kāi)關(guān)被設(shè)置到頂部或底部時(shí),保持電機(jī)運(yùn)行10ms并將其置為Imax.然后按照公式： 計(jì)算當(dāng)前臨界值電流。盡管如此,為避免樣本數(shù)據(jù)產(chǎn)生較大的偏差,使用加權(quán)平均法來(lái)消除此偏差,根據(jù)公式 計(jì)算出臨界值電流后,用新產(chǎn)生的值替換存儲(chǔ)于閃存的原始值 。
臨界值電流隨Ntest的變化情況，如圖2-1所示。
圖2-1 對(duì)Ntest的影響
Ntest的值取決于不同的模型和不同的應(yīng)用環(huán)境。當(dāng)Ntest值越大，歷史值更多的取決于Ntest，而電流臨界值隨環(huán)境的變化越慢，從而得到的穩(wěn)定性更好。當(dāng)Ntest越小，電流值所起的決定性因素更高，電流臨界值隨當(dāng)前環(huán)境的變化越敏感，但同時(shí)穩(wěn)定性會(huì)惡化。
自動(dòng)配置臨界電流值的方法有效的克服了anti-pinch配置臨界值電流的缺點(diǎn)，提高了防夾車窗的精度。當(dāng)現(xiàn)值樣本時(shí)，其判定當(dāng)前存在障礙物，同時(shí)此刻車窗上升的開(kāi)關(guān)被忽略，電機(jī)會(huì)繼續(xù)將車窗向下拉一段距離以避免發(fā)生事故。
4系統(tǒng)設(shè)計(jì)
本論文是通過(guò)使用多塊智能型片來(lái)進(jìn)行電流取樣從而實(shí)現(xiàn)防夾功能的。從電流反饋到實(shí)現(xiàn)防夾功能是基于電機(jī)負(fù)載增加的原則，電機(jī)電流會(huì)隨著負(fù)載的增加而相應(yīng)地增加。MC33887是一種高性能集成微型處理器，其負(fù)載電流反饋特征使其成為理想的直流電機(jī)閉環(huán)控制器。其能對(duì)全橋電路高端電流進(jìn)行實(shí)時(shí)監(jiān)控反饋，從而能促進(jìn)電機(jī)速度和扭矩實(shí)現(xiàn)閉環(huán)控制。因此MC33887是很好的選擇。
硬件由MC68HC908GR8，MC33689，MC33887 和MC33884 組成[4-7]。MC33689是一種基于LIN驅(qū)動(dòng)的綜合動(dòng)力管理芯片，MC33887是一種整體式的全橋集成電路并具有負(fù)載電流反饋特征，MC3384是一種集成智能開(kāi)關(guān)芯片，而MC69HC908GR8則是一個(gè)8字節(jié)的微控制器。芯片間的線路原理圖如圖3-1。
圖3-1 車窗控制硬件設(shè)計(jì)圖
在這項(xiàng)工作中，MC33887能將接收到的瞬時(shí)電流值通過(guò)AD輸入到FB然后輸出到MCU，MCU再根據(jù)電流值判斷是否有障礙物。當(dāng)電流值增大到超過(guò)Iclip，可以判斷當(dāng)前存在障礙物。
5．結(jié)論
車窗防夾系統(tǒng)是一種極端復(fù)雜的系統(tǒng)，環(huán)境、機(jī)器、以及許多其他的因素都會(huì)自動(dòng)操縱車窗造成影響。在其他國(guó)家，防夾車窗產(chǎn)品的研究和應(yīng)用已經(jīng)持續(xù)了幾十年，因此技術(shù)上已經(jīng)不成問(wèn)題。但在中國(guó)，由于汽車電控技術(shù)開(kāi)始較晚，此項(xiàng)技術(shù)仍具有挑戰(zhàn)。本論文分析了通過(guò)電機(jī)電流來(lái)實(shí)現(xiàn)電控防夾功能的方法。由于各模塊都有單獨(dú)的電控ECU來(lái)進(jìn)行控制，在損壞的情況下，其余的三個(gè)部件仍可以工作，提高了系統(tǒng)的可靠性和安全性。通過(guò)電機(jī)反饋電流來(lái)實(shí)現(xiàn)防夾功能的方法能有效地減少系統(tǒng)成本。
鳴謝
本論文得到中國(guó)國(guó)家自然科學(xué)基金No.60903011的授權(quán)支持，浙江省自然科學(xué)基金No.Y1100689的授權(quán)，浙江省科技部基金會(huì)NO.2010C31122授權(quán)。
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