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International Journal of Control and Automation
Vol. 2, No. 1, March, 2009
Fabrication of Auto-Braking System for Pre-Crash Safety
Using Sensor
Eung Soo Kim
Div. Digital Media Engineering, Pusan University of Foreign Studies, Busan, Korea
e-mail: eskim@pufs.ac.kr
Abstract
The auto-braking system was designed by VHDL and fabricated to keep a distance between two cars. It provides pre-crash safety system for intelligent car. This module can detect the distance between front vehicle and driver’s vehicle to keep a constant distance using a sensor and operate the brake system forcibly if the driver does not decrease the speed of car. The system displays the distance between the two vehicles and the speed of your vehicle. The performance of the system was good.
Keywords: Auto-Braking System, Pre-cash safety, Sensor
1. Introduction
An automobile has been used to move human beings or something since the automobile was invented and the automobile technology has been developed within the last few years. Recently, the automobile is thought as daily necessaries because we spend much time in an automobile and enjoyed the entertainment such as game, e-mail, DVD, mp3, and internet etc. in the car. In nowadays, the intelligent car with adaptive cruise control, lane keeping technology, auto-parking system, tire pressure monitoring system (TPMS), and prevent precrashing system has been equipped because we need the convenient and intelligent car [1-3]. These new automobile technologies are made possible by the development of semiconductor technology, optical technology and software technology.
The use of electronic components in automobiles is set to accelerate and with ongoing efforts to improve safety and comfort. 250 electronic components are used in a car, for example, 50 MCUs are used in a car. Therefore, car makers in Europe and Japan are developing for safety such as both collision safety and preventive safety and new car technology for intelligent car such as intelligent transport system (ITS), rear view camera system, Road-to-vehicle and Inter-vehicle Communication Systems, auto-parking system,hybrid car, electric car, and hydrogen fueled car [4]. In addition, some vehicle networks will enter commercial use, such as the FlexRay interface instead of CAN bus for onboard local area network (LAN), which supports high-speed transfer, and MOST (media oriented systems transport) or IDB-1394, which can move multimedia data, that is audio and video signals,from multiple camera systems or multimedia devices, such as DVD, navigation system, mp 3,TV tuner, and CD changer etc. at once. Car makers are beginning to develop equipment for high-end vehicles with systems to sense roadway conditions using cameras, radar, sensors and such in an effort to avoid accidents. The traffic accident is increasing as automobile production has been increasing. It is important to prevent accidents and to protect the driver and pedestrian when accidents were occurred. Therefore, pre-crashing system will be demanded. The pre-crash system is to prevent front-end, rear-end, right-turn and left-turn accidents on roads with poor visibility by using sensor network to find invisible vehicles,which are to be detected by autonomous on-vehicle sensors. The pre-crashing system is processing the sensor data and controlling the vehicle to prevent front-end, rear-end accidents and accidents caused by careless driving. The development of such systems to automatically control vehicles and avoid accidents will accelerate in the future.
In this paper, we designed the auto-braking system which keeps a distance between the front car and driver car to prevent accident using sensor and fabricated it using FPGA and VHDL [5]. The power consumption of system was very small and another sensor or camera will be added easily. The performance of the system was good.
2. Design and Implementation
The fabricated auto-braking system has the sensor part and signal processing part to prevent an accident as shown in Figure 1. It performed monitoring the environment and sensor signal processing. The sensor embedded in vehicle will detect the road environment,such as self-velocity, distance from front vehicle, and surroundings vehicles, using infrared sensor and ultrasonic sensor. These sensors were operated all the time during driving. The processing part accepted the signal from sensors and processed the signals and generated the instructions and transferred the generated instruction to control unit of transmission and brake of vehicle. There are three cases occurred in real situations. One case is that the distance between the front car and driver’s car is far enough to defend crashing and self-velocity is the same velocity of front car or slower than that of front car. In this case, the driver’s car is continuously running without changing its velocity. Another case is that the distance between the front car and driver’s car is near and self-velocity is slower than that of front car. In this case, the driver’s car is also continuously running without changing its velocity. Another case is that the distance between the front car and driver’s car is near and self-velocity is faster than that of front car. In this case, the driver’s car is continuously running only when the driver reduce speed. But if the driver does not reduce speed, the auto-braking system may forcibly reduce the speed of driver’s car to protect an accident. The reason is that if the driver does not reduce speed, the accident will be occurred and the driver will be hurt.
Figure 1. The operation principle of the fabricated auto-braking system.
The important thing in auto-braking system is detect the distance and speed of front vehicle to prevent a traffic accident. We chose an ultrasonic sensor used to detect the distance between a front car and driver’s car because we mounted the fabricated system on a miniature car with a reduced scale of 1:20. The detectable range of the ultrasonic sensor was up to 3m.
We have made 4 MHz clock signal to generate ultrasonic sensor signal. The generated sensor signal was PWM (pulse width modulation) signal when 10 μs input signal was given as shown in Figure 2(a). Fig 2 (b) shows the simulation result of sensor input signal to detect the distance. The simulation was carried out by VHDL. The PWM signal which was reflected from the front car was varied from 1 ms to 11 ms according to the distance between the front car and driver’s car. Figure 3 (a) shows the simulation result of distance measurement from front car sensor using 4MHz input signal. The input pulse of sensor with duration of 2ms was displayed in Figure 3 (a). Figure 3 (b) output signal with 1ms pulse duration time. Figure 3 (c) shows the sensor output signal with 10ms pulse duration time. The duration of PWM sensor signal was increasing as the distance between the front car and driver’s car is increasing. We divided the reflected sensor signal into 10 values in according to the pulse duration of the reflected sensor signal. The motor of miniature car was varied from low speed to high speed according to these 10 different values, which are sensor output signals. The motor control signal is consists of 4bits and the clock signal of the stepping motor was changed as the variation of the sensor signal.
The stepping motor was controlled by the reflected sensor signal, that is, the speed of automobile became slow as the distance became close with the front automobile. If the pulse duration of the reflected sensor signal becomes narrow, it means that our car get near to the front car. So, the driver must decrease the speed of
Figure 2. (a)Sensor input signal with 10 μs in oscilloscope screen and (b)simulation result of input signal.
Figure 3. (a) the simulation result. PWM sensor output signal with (b) 1ms and(c) 11 ms in oscilloscope screen.
car. If a driver does not reduce the speed of car, the fabricated auto-braking system forcibly makes speed low. The output PWM signal from ultrasonic sensor displayed by 15bits and decided the control signal of motor to control the speed of motor. Figure 4 shows the source program to detect the motor speed. We used the division by 4000 counters to detect the car speed. Figure 5 shows the simulation result of the program as shown in Figure 4, where the length of arrow means the one rotation of motor. As above mentioned, the motor has 4bits control signal such as 1100, 0110, 0011, and 1001. The stepping motor was controlled by these 4 bits signal. We counted the 1100 signal to measure the speed.
Figure 4. The source program to detect the motor speed.
Figure 5. The simulation result of the motor control signal
The auto-braking system moved the brake pedal to reduce the speed if the distancebetween the front car and driver’s car. If the distance between front car and driver’s car was far, the pulse duration was the same and the auto-braking system does not work. We use servo motor to move the brake pedal. The brake pedal was controlled by PWM signal, which is different according the distance between the front car and driver’s car. The speed of the car was changed according to the angle of the brake pedal. The angle of the brake pedal was varied at the degree of 0, 35, 70, and 90. The speed of the car was decreasing as the angle of the brake pedal was increased. The car was stopped as the angle of brake pedal was 90°. We used servomotor to work the brake pedal. Figure 6 (a) shows the source program to control the brake pedal and simulation result. And Figure 6 (b) shows the simulation result at the PWM signal when the state of steeping motor was 0000, that is stepping motor was stopped. In Figure 6, servo_clk is output PWM signal and Figure 6 (c) shows the simulation result when the state of stepping motor was 1010. We decided the state of stepping motor as arbitrary to simulate the operating of brake pedal. The output PWM signal of brake pedal was varied as the state of steeping motor. The speed of driver’s car slowed down as the angle of brake was decreased. Figure 7 shows the block diagram of auto-braking system, where four input signals, clk, rst, direct, and in_clk, were needed in the auto-braking system. The clk input was clock signal, rst input was reset signal stop the operation of ultrasonic sensor, direct input made the stepping motor rotate opposite direction, and the output signal from the ultrasonic sensor was counted by in_clk input signal. The SOUND_CLK part generated sensor signal of the ultrasonic sensor to detect the distance. The sensor signal had 10 μs of pulse duration and the period was 5ms. If the rst signal was inputted, the sensor did not work.The high value of PWM sensor signal was counted at the COUNTBOX part and the count value used 15 bits.
Figure 6. (a) The source program to control the brake pedal, (b) the simulation result at the PWM signal with 0000, and (c) the simulation result at the PWM signal with 1010.
Figure 7. Block diagram of auto-braking system.
The SELSIGNAL part chose the control signal to select the period of the stepping motor clock signal. It selected one of 10 different values of stepping motor speed and the speed of car was varied by the selected signal. The SERVO part generated the control signal which decided the degree of the servomotor according to the select signal. The degree of the servomotor controlled the speed of the stepping motor. We generated 1 KHz signal to calculate the speed by dividing 4 MHz by 4000. It was performed at FQ_DIV4000 part. We have known the speed of stepping motor as counting how many times “1100” appears. This showed the rotation speed of stepping motor. We fabricated the auto-braking system using FPGA. The distance, the RPM of stepping motor, and the angle of brake pedal was displayed in the LCD panel as shown in Figure 8. In this case, the LCD display showed that the driver’s car is running without reducing the speed. The distance can be converted as real distance value. The operation of the system was good.
Figure 8. LCD screen displayed distance, speed, and angle
We also implemented the system using Labview and added surrounding sensing system to prevent an accident. Figure 9 shows the computer monitor which displayed the car speed and the angle of brake pedal by Labview program. It makes easy to implement user interface.
Figure 9. The screen executed by Labview
3. Conclusions
The auto-braking system was designed by VHDL and fabricated using FPGA to prevent accident. The system was mounted on a miniature car and tested. When the distance was getting closer, the auto-braking system was working and the speed will slow down if a driver does not reduce the speed of automobile. We also fabricated the auto-braking system using Labview. We will replace an ultrasonic sensor with a radar sensor as the auto-braking system is mounted on a real automobile.
4. Accknowledgment
We thank Jong Hui Park, Kyung Wha Cho for test.
5. References
[1] J. H. Kim, “Application and prospect of information technology: transport,” TTA Journal, vol. 117, May 2008, pp. 30–31, (in korean).
[2] See the www.toyota.co.jp.
[3] S.Mastumoto, M. Ishigura, “The latest hybrid car”, Automobile Technology, 2007.
[4] J. Kang et al, Digital systems design using VHDL, SciTech, 1998.
譯文
國際自動化控制學(xué)報
第一卷2，第1號，2009年3月
預(yù)碰撞制動安全傳感器的設(shè)計
金英書
數(shù)字媒體工程，釜山外國語大學(xué)，釜山，韓國 電子郵件：eskim@pufs.ac.kr
摘要
汽車制動系統(tǒng)采用VHDL語言設(shè)計與制造，兩輛車之間保持一定距離。它提供了預(yù)碰撞安全系統(tǒng)的智能汽車。該模塊可檢測前方車輛和司機之間的車距保持恒定距離使用傳感器和制動系統(tǒng)強行操作，如果驅(qū)動程序不減少汽車的速度。系統(tǒng)顯示兩車之間的和您的車輛行駛速度的距離。該系統(tǒng)性能良好。
關(guān)鍵詞：汽車制動系統(tǒng)，預(yù)碰撞安全，傳感器
1． 介紹
汽車已被用作人類移動的東西被發(fā)明以來，汽車和汽車技術(shù)已在過去數(shù)十年的發(fā)展。最近，汽車被認(rèn)為是日常必需品，因為我們花很多時間在汽車和享受上，如游戲娛樂，電子郵件，DVD，MP3和互聯(lián)網(wǎng)等在車?yán)镞M行。在今天與之適應(yīng)的巡航控制的智能車，行車線保持技術(shù)，自動停車系統(tǒng)，輪胎壓力監(jiān)測系統(tǒng)（TPMS），并防止碰撞系統(tǒng)已具備，因為我們需要的方便、智能的汽車[1-3]。這些新的汽車技術(shù)，是通過對半導(dǎo)體技術(shù)的發(fā)展，光學(xué)技術(shù)和軟件技術(shù)的發(fā)展而發(fā)展起來的。典型的剎車系統(tǒng)包括剎車前面的磁盤和磁盤或鼓中的管子鏈接在每個車輪的剎車總泵剎車系統(tǒng)連接在后方。與制動系統(tǒng)有關(guān)的其他系統(tǒng)包括停車制動器，電力制動助力器和防抱死系統(tǒng)等。
汽車電子組件的應(yīng)用加速了正在努力進行的安全性和舒適性的提高。250個電子元件被廣泛應(yīng)用于汽車，例如，50個微控制器在汽車中使用。因此，汽車制造商在歐洲和日本正在開發(fā)，如預(yù)防碰撞安全技術(shù)和智能汽車新技術(shù)，例如汽車智能交通系統(tǒng)（ITS），后視攝像系統(tǒng)，道路對車輛和車輛間通信系統(tǒng)，自動停車系統(tǒng)，混合動力汽車，電動汽車，氫燃料汽車[4]。此外，一些車輛將被連接進入網(wǎng)絡(luò)，而不是如用于車載總線的CAN局域網(wǎng)絡(luò)（LAN的FlexRay接口商業(yè)使用），支持高速傳輸，而且大多數(shù)（媒體導(dǎo)向系統(tǒng)傳輸）或IDB - 1394，其中可以傳輸多媒體數(shù)據(jù)，即音頻和視頻信號從多個攝像系統(tǒng)或多媒體設(shè)備傳輸，如DVD，導(dǎo)航系統(tǒng)，熔點3，電視調(diào)諧器和CD轉(zhuǎn)換等的一次。汽車制造商已經(jīng)開始制定與系統(tǒng)設(shè)備的高端車感巷道條件下使用相機，雷達，傳感器等，努力避免發(fā)生意外。越來越多的交通意外的汽車產(chǎn)量已經(jīng)提高。重要的是要防止意外發(fā)生，保護司機和行人時，意外發(fā)生。因此，預(yù)碰撞系統(tǒng)將要求。預(yù)碰撞系統(tǒng)是為了防止利用傳感器網(wǎng)絡(luò)，以找到無形的車輛，這是前端，尾部，右轉(zhuǎn)和能見度差的公路左轉(zhuǎn)入事故是由自主在車輛檢測傳感器。預(yù)碰撞傳感器系統(tǒng)，數(shù)據(jù)處理和控制，以防止車輛前端，尾部意外及不小心駕駛引致的意外。這種系統(tǒng)的發(fā)展將
國際自動化控制學(xué)報
第一卷2，第1號，2009年3月
現(xiàn)代汽車制動系統(tǒng)已完善了超過100年，已經(jīng)是非常可靠和有效的了。在本文中，我們設(shè)計了自動剎車系統(tǒng)，以保持與前車和司機車距離，以防止意外的發(fā)生。如果制動失靈，結(jié)果可能是損失慘重的。使用這項技術(shù)制作傳感器和利用FPGA和VHDL [5]。該系統(tǒng)功耗非常小，其他的傳感器或照相機將被更容易與之相適應(yīng)。該系統(tǒng)性能良好，工作可靠。
2．設(shè)計與實現(xiàn)
虛構(gòu)的汽車制動系統(tǒng)是傳感器和信號處理部分的一部分，以防止交通事故，如圖1所示。它表現(xiàn)在道路監(jiān)測和傳感器信號處理。該傳感器將檢測汽車嵌入式道路環(huán)境，如自身速度，與前方車輛的距離，周圍的車輛，使用紅外線傳感器，超聲波傳感器感應(yīng)。這些傳感器是在駕駛操作的所有時間里使用的。該處理的一部分接受和處理來自傳感器的信號產(chǎn)生的信號和指示，并移送生成的指令，以控制汽車的制動和VE的制動裝置hicle。在實際生活中有三種案件發(fā)生。一個例子是，與前車和司機的車距較大時，這種情況是遠(yuǎn)遠(yuǎn)不夠追上前車的自身的速度比同樣前車或前方車的速度慢。在這種情況下，自身的車是連續(xù)運行沒有使用C懸掛的速度。另一個例子是，與前車和自身的汽車已接近而自身距離速度比前車慢。在這種情況下，司機駕駛車也沒有改變它的速度是連續(xù)運行。另一個例子是，與前車和自身的汽車已接近而自我的距離是速度快于前車的。在這種情況下，自身的車是連續(xù)運行的只有當(dāng)司機主動減慢車速時車子的速度才會下降。但如果司機不減速，自動剎車系統(tǒng)可能會被迫減少自身的車速，以保障避免事故。原因是，如果驅(qū)動程序繼續(xù)不降低車速的話，將發(fā)生事故司機將受到損害。
圖1汽車制動系統(tǒng)的工作原理。
在汽車制動系統(tǒng)中重要的是偵測前方車輛的距離和速度以防止交通意外。我們選擇了一個超聲波傳感器檢測與前車和一個司機的車的距離，因為我們裝在一個有1:20縮尺微型汽
國際自動化控制學(xué)報
第一卷2，第1號，2009年3月
車的制造系統(tǒng)中。超聲波傳感器的探測范圍可達3米。
我們已取得4 MHz的時鐘信號產(chǎn)生超聲波傳感器的信號。生成的傳感器信號的PWM（脈寬調(diào)制）信號輸入信號時10微秒給出如圖2（a）的條，圖2（b）顯示了傳感器的輸入信號模擬結(jié)果發(fā)現(xiàn)距離。仿真是用VHDL進行。PWM信號是從正面反映了不同的車從1毫秒到11毫秒之間根據(jù)前面車和司機的車程。圖3（a）顯示了由前車的距離測量傳感器使用
圖2（a）傳感器在示波器屏幕10微秒的輸入信號（b）模擬輸入信號的結(jié)果。
圖3（a）仿真結(jié)果（b）1毫秒的輸出信號（c）11毫秒的輸出信號
4MHz的模擬結(jié)果輸入信號。該傳感器具有2ms的輸入脈沖持續(xù)時間為圖3（a）。圖3（b）輸出脈沖持續(xù)時間1ms的信號。圖3（c）顯示了10ms的脈沖持續(xù)時間傳感器的輸出信號。該傳感器的PWM信號持續(xù)時間為前方車和司機的車距離的增加。我們分成10個值中根據(jù)反射傳感器信號脈沖寬度反射傳感器信號。微型汽車發(fā)動機的變化是從低速到高速根據(jù)這
國際自動化控制學(xué)報
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10個不同的值，這些傳感器的輸出信號。馬達控制信號是由4bits和步進電機時鐘信號作為
傳感器信號的變化改變了。
圖4源程序檢測電機轉(zhuǎn)速。
圖5電機控制信號的仿真結(jié)果
步進馬達控制反射傳感器信號，那就使汽車的速度變得緩慢，距離減小前關(guān)閉。如果反射傳感器信號脈沖寬度變窄，這意味著我們的車靠近前面的車。因此，司機必須降低車速。如果驅(qū)動程序不減少汽車的速度，所制作的自動剎車系統(tǒng)強行將高速減低。由超聲波傳感器的15bits顯示輸出PWM信號，并決定了電機控制信號，控制電機轉(zhuǎn)速。圖4顯示了源程序檢測電機轉(zhuǎn)速。我們使用的4000柜臺的部門，檢測車的速度。該方案的仿真結(jié)果，如圖5所示，其中箭頭的長度是指一個旋轉(zhuǎn)的電動機。如上所說，馬達如1100，0110，0011 4bits控制信號，和1001。步進馬達控制這4位信號。我們計算了1100信號來測量速度。
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圖6（a）源程序控制剎車踏板（b）在與0000 PWM信號模擬結(jié)果（c）在1010 PWM信號與模擬結(jié)果。
自動制動系統(tǒng)，制動踏板提出降低車速，如果前面的車和司機之間的車程遠(yuǎn)，脈沖持續(xù)時間是相同的，自動制動系統(tǒng)不工作。我們使用伺服電機移動剎車踏板。剎車踏板的控制PWM信號，這是根據(jù)不同的線路之間的車和司機的車程確定的。車的速度改變根據(jù)剎車踏板的角度。該剎車踏板角變化在0度，35，70和90變化。車的速度作為剎車踏板的角度減少或增加。我的車D作為剎車踏板角90 °。我們使用伺服電機工作的剎車踏板。圖6（a）顯示源程序控制剎車踏板和仿真結(jié)果。圖6（b）顯示了在PWM信號仿真結(jié)果時，浸泡電動機狀0態(tài)是0000，即步進馬達停止。在圖6中servo_clk輸出PWM信號和圖6（c）模擬
圖7汽車剎車系統(tǒng)。
結(jié)果的顯示，當(dāng)步進電機狀態(tài)1010。我們決定了步進電機任意模擬制動踏板。剎車踏板的輸出PWM信號是多種多樣作為浸泡電動機狀態(tài)。對司機的車速減慢作為制動角下降。圖7顯示了汽車制動系統(tǒng)，其中四個輸入信號時鐘，RST，對直接，in_clk，在汽車制動系統(tǒng)所需的框圖。在CLK為時鐘信號輸入，RST輸入復(fù)位信號是停止運作的超聲波傳感器，直接
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輸入的步進電機旋轉(zhuǎn)相反方向，從超聲波傳感器的輸出信號由in_clk計數(shù)輸入信號。該
SOUND_CLK部分產(chǎn)生的超聲波傳感器的傳感器信號檢測距離。該傳感器的信號有10微秒的脈沖持續(xù)時間和時間為5毫秒。如果RST信號的輸入，傳感器的PWM信號的高值計算在COUNTBOX的一部分，使用15位計數(shù)值。
該SELSIGNAL部分選擇了控制信號，選擇步進電機的時鐘信號周期。它選擇的10步進電機的速度和車速不同，是由選定的信號變化。伺服控制部分產(chǎn)生的信號，決定了伺服電機程度按選擇信號。該伺服程度控制了步進電機的速度。我們生成1 kHz信號來計算4000除以4兆赫的速度。這是完成的FQ_DIV4000的一部分。我們已經(jīng)知道了步進計數(shù)多少次“1100”出現(xiàn)電機轉(zhuǎn)速。這表明步進電機旋轉(zhuǎn)速度。我們虛擬汽車制動系統(tǒng)用FPGA。步進電機的轉(zhuǎn)速，以及剎車踏板角顯示在液晶顯示面板。在這種情況下，液晶顯示屏顯示，司機的車是沒有減少的速度運行。距離可轉(zhuǎn)換為真正的距離值。該系統(tǒng)的運作是好的。
圖8液晶屏幕上顯示距離，速度和角度
我們還實施了系統(tǒng)使用Labview和補充周邊傳感系統(tǒng)，以防止發(fā)生意外。圖9顯示在計算機顯示器上顯示的是汽車的速度和剎車踏板的角度LabVIEW程序。這使得很容易實現(xiàn)用戶界面。
圖9通過Labview的執(zhí)行畫面
3．結(jié)論
國際自動化控制學(xué)報
第一卷2，第1號，2009年3月
自動制動系統(tǒng)設(shè)計利用FPGA的VHDL的制作以防止意外發(fā)生。該系統(tǒng)是安裝在微型車和測試。當(dāng)距離越來越近，自動剎車系統(tǒng)的工作，速度將會減慢，如果驅(qū)動程序不減少汽
車的速度。我們還制作了自動剎車系統(tǒng)采用Labview的。我們將替換為汽車制動系統(tǒng)雷達傳感器，超聲波傳感器是一個真正在汽車上安裝的傳感器。
4．致謝
我們感謝鐘暉園，趙慶和的測試。
5．參考文獻
[1] JH金.信息技術(shù)應(yīng)用與展望[J] .驅(qū)動tTA雜志， 2008，1（117）：30-31（韓國）。
[2] Editor. 智能汽車的研究[J]. ScieneDaily，2006.3（電子出版物）。
[3]見www.toyota.co.jp。
[4]南Mastumoto，米石倉，最新的混合動力汽車[J].汽車技術(shù)，2007。
[5]蘇康等人，利用VHDL數(shù)字系統(tǒng)設(shè)計[J].賽特，1998。