Peng Wang1 , Peijun Sun1 ,Linyuan Niu2, Baokun Liu1, Shugang Jiang3
1. Logistics Management , Baoding University
2. College of Electrical and Mechanical Engineering , Agricultural University of Hebei
3. Department of Physics and Electronic Engineering , Baoding University
Baoding , China
1. 5615134@qq.com 2.niulinyuan@126.com
Abstract—For ensuring traffic safety requirements and meeting Fuzzy controller, as the core module, via fuzzifying the input the development of current automobile industry , the paper after the process of the SCM , matching the corresponding presents the design against rear-end accident. The design would fuzzy membership function to get output for controlling the complete the intelligent control of brake system via using single-brake system effectively. In addition, external expansion voice
chip microcomputer (SCM) data processing ability, and prompts module would provide warning and alert to the driver combining the fuzzy control theory. Millimetre wave (MMW) through the feedback from brake system to the SCM, which radar is selected to measure the distance between vehicles and the would increase the road safety and be more user-friendly relative velocity of the vehicle in the design. The measurement design. The overall design is shown as in the figure 1.
data would be as the input of the fuzzy controller when it is output after processed in SCM C8051F020. Then the output of the fuzzy controller would be as the parameters to control vehicle brake system, which could effectively prevent the car directly collision accident.
Keywords-Automobile anti-rear-end; Millimeter wave radar㧧Single-chip microcomputer C8051F020㧧Fuzzy control
I. INTRODUCTION
Figure 1. Hardware structure diagram
In today’s vehicles, active safety systems are introduced addressing a large variety of safety issues such as providing optimal stability control, braking effect, preventing spin and rollover, as well as collision avoidance, to mention just a few. In addition, the number of these systems is expected to grow. To analyse from the share of cars and the reasons for car accident, the frequency of rear-end accident is higher than other, which should take more attention, and appropriate measures should be taken to avoid or reduce risk factors. Consequently, it is proposed in the paper that the concept of intelligent brake control for reducing the rear-end accidents.
II.
HARDWARE DESIGN
B. Millimeter-wave radar ranging system design
Millimeter wave is electromagnetic waves that the length range between 1 to 10 mm. Automotive millimeter-wave radar is one of the key technologies to improve vehicle safety, as while as an important part of intelligent transportation systems .
The millimeter-wave automotive anti-collision radar is composed of sensor, signal processor and controller. The working principle is: firstly, sensors launch the millimeter wave via the antenna to detect the signal, then received millimeter-wave signals reflected back from obstacles, which will be send to the signal processor for analysis and processing. The the distance between the obstacle and the vehicle will be calculate from transmitting signals and the delay of the reflected signals. Then the signal processor synthesize the distance, speed and other signal data input by the sensor of the car (such as speed, brake pressure, etc.), issue the appropriate commands to the vehicle operating system, such as automatic deceleration, shifting, braking, etc.; another instruction is to signal warning to the driver, such as deceleration, braking, steering, parking, etc., in order to protect the vehicle to prevent collision with obstacles .
A. The overall design
The center of the design is to replace the driver's experience by the use of fuzzy control . The scientific and rational braking parameters obtained to ensure that vehicles in a safe and effective to avoid rear-end events. Anti-rear-end intelligent controller uses millimeter-wave radar to measure the distance between vehicles and the relative velocity. The hardware structure is simple, and easy to implement. Using C8051F MCU which with self-analog-digital conversion function will further simplify the hardware circuit, so that to make the design more integrated , with faster process speed and accuracy.
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Beat formula after mixing the frequency of the up and 1) The main advantages of millimeter-wave radar:
a) Stable detection performance. Millimeter-wave down sweep signal : radar possess stable and accurate ranging performance and Beat formula of the up sweep signal: high range resolution, making the millimeter wave in a vehicle
2
ªcollision avoidance system has been widely used. Unaffected º½μτtªº()°°¬¼+
SB(t)=Kcos®2π«μτt(t)−+f0τ(t)»¾(1)by the surface shapes, colors and other effects that of the
2«»°°measured object. Be adaptive of atmospheric turbulence and ¼¿¯¬
air vortices, and millimeter-wave radar antenna will not be
result a greater error by dust and other pollution.
b) Good environmental adaptability. Millimeter-wave Beat formula of the down sweep signal:
radar possess strong penetrability. The range accuracy will be
2
ª½little affected by rain, snow, fog, sun and other weather factors º°μτtªº()°¬¼−and the noise, pollution and other environmental impact . As SB(t)=Kcos®2π«−μτt(t)++f0τ(t)»¾(2)
2»°result ,the vehicle can be ensured in the normal operation in °«¬¼¿¯
any weather condition.
From advantages of millimeter-wave radar above can be
found it has processed more superiority than ultrasound, laser, IJ (t) is the echo instantaneous delay signal relative to the infrared, etc. It can adapt to automotive collision avoidance transmitted signal. The beat signal would be proceed Fourier systems. In addition, under the same measurement conditions, transform after being amplified filters and A / D conversion millimeter-wave radar processes simple structure , high processing, then obtained: resolution. And the small size of the antenna parts is more
Beat frequency of the up sweep signal: conducive to install [1].
2) Signal processing and analysis
In this design, the cost is a very important factor. In order to make the intelligent control system hardware with low cost, single-beam radiation has been selected, which is only with the basic function of distance speed. This will greatly simplify the complexity of the signal processing part and reduce cost. Anti-collision radar system can be divided into continuous wave mode and pulse Doppler mode. As single-pulse mode is more difficult for radar range, a triangle wave linear frequency modulation continuous wave(LFMCW) approach has been adopted [2]. Using the beat Fourier methods, the target distance and speed can be determined in a cycle . It is simple to handle and easy to implement. Because of its special and continuity of the waveform, the algorithm is relatively feasible, but also in the hardware implementation is easier. The beat signal output from the mixer is the only signal containing target information, so as to obtain the beat signal, the modulated transmit signal is divided into two routes, one way is sent to space from the antenna, the other way through the frequency synthesizer send to a mixer or amplifier as the oscillator signal, echo signal can also be as the delay of the oscillator signal , as shown in Figure 2.
fb+=8RΔF−fd(3)
cTp
Beat frequency of the down sweep signal:
fb−=
8RΔF
+fd
cTp
(4)
fd is the Doppler frequency shift targeted for the campaign objective,
fd=
2νλ0
=
2f0ν (5) c
From the formula (1) and (2) ,it can be found out that the two formula content the information of the distance and velocity,which can be calculated directly through simply operation:
fb++fb−×R=Δ8F2 (6)
cTp
fb−−fb+cv=×
f04
(7)
The Relationship between the symbols of the velocity and
the direction of relative movement is that, when the target vehicle is relatively near the vehicle radar it is positive, while the target vehicle's movement relative to the trend of departure from the automotive radar it is negative. because the test here is the relative velocity between the two vehicles, the velocity is the absolute value , the final results obtained are positive.
Figure 2. LFMCW triangle wave transmitting and receiving time-frequency
diagram
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C. Single-chip microcomputer as the core data acquisition system
Select C8051F series SCM [3]. This kind of SCM is provided with Programmable Gain Amplifier (PGA), True 12-bit 100ksps 8-channel ADC with PGA and analog multiplexer ,k bytes of in-system programmable FLASH memory, 4352(4096+256) bytes of on-chip RAM, Programmable 16-bit Counter/Timer Array with five capture/compare modules, On-board JTAG debug and boundary scan, owns enough on-chip resources . Each MCU of C8051F020 is specified for 2.7V-to-3.6V operation voltage. Multiple electricity saving and stop mode, low power consumption.
The C8051F020 have 4 ports of the standard 8051 and 4 additional ports, for a total of general-purpose port I/O. The on-chip counter/timers, serial buses, HW interrupts,ADC Start of Conversion input,comparator outputs,and Other digital signals in the controller can be configured to appear on the Port I/O pins specified in the Crossbar Control registers.
The C8051F020 has an on-chip 12-bit SAR ADC(ADC0) with a 9-channel input multiplexer and programmable gain amplifier. With a maximum throughput of 100ksps, the ADC offers true 12-bit accuracy with an INL of r1 LSB. The ADC is under full control of the CIP-51 micro controller via its associated Special Function Registers. One input Channel is tied to an internal temperature sensor, while the other eight channels are available externally. Each pair of the eight external input channels can be configured as either two single-ended inputs or a single differential input. The ADC is integratedwith track-and-hold and Programmable Window Detector .The AMUX0, PGA0, Data Conversion Modes, and Window Detector are all configurable under software control via the Special Function Registers . The C8051F020 MCU Family includes two Enhanced Full-Duple UART, SPI Bus, and SM Bus/I2C.
D. Design of extended voice prompt module
Data display along with voice prompts avoid other issues caused of \"not seeing\environment. ISD4004 voice chip can be adopted. The core of the module is voice chip ISD4004. ISD4004 voice chip using CMOS technology, includes crystal oscillator, antialiasing filter, smoothing filter, automatic mute, audio power amplifiers and high-density multi-Flat flash storage arrays. So only a few external devices can constitute a complete sound recording system.ISD4004 voice chip process a serial peripheral interface (SPI) , a long time for recording sound , good sound quality, needn't A / D conversion, can be re-record 10 million times, data can be saved after power 100 years.Voice prompt module connected with the microcontroller as shown in Figure 3.
Figure 3. Voice module hardware circuit
III. BRAKE CONTROL MODULE - THE FUZZY CONTROL
ALGORITHM
According to the parameters collected by the SCM, adopting fuzzy control method, it can be abtained the best brake force, which can effectively reduce rear-end accident frequency.
Fuzzy logic theory is introduced in the design of anti-rear-end controller. First, it has simplified the control model, just need to consider the distance between two vehicles and rate of change value of the distance (ie, velocity). When the two vehicles keep the short distance, then limit the speed of the car. When two cars reached the limits of distance 1 m, then the car should be stopped unconditionaliy. On the macro level, when the two vehicles keep within 5 m, it is started in real-time control [4]. The smaller distance between the two vehicles keep , the smaller speed is required for the car, the greater changes in the value of the relative speed of the vehicle speed. When encountered emergency brake, there is a process of small to large in the relative speed of two vehicles at the micro. In this process, SCM is used to real-time control the speed of the vehicle , in order that the car being \"slow\" decelerated, as it avoids rear-end and guarantee the safety of the driver.
Control model mainly based on relative change of the vehicle distance and speed to control braking force for further controlling the speed. The simplified model has been shown in Figure 4. The main parameters of the control is speed control which would be affected by the factors that the size and the nature of the distance from the vehicle in front . The nature of the distance described as the rate of change of the relative velocity. Distance from the vehicle in front and the rate of change of the speed can be used as input parameters for the control system, while the braking force can be used as control value which is the output of the system. Fuzzy control rules are list in Table 1. In fact, such a precise mathematical model is difficult to describe between input and output in the braking process. A great uncertainty is exist in the process, so it is largely dependent on operator experience. so that, it is difficult to use the conventional method of control. Therefore, fuzzy control theory greatly reduces the difficulty of control, more intelligent and reliability. [5]
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Figure 4. A simplified model of fuzzy controller
TABLE I. FUZZY CONTROL RULE TABLE
driver usually judge the traveling state according to their own experience , when the feeling of danger is present, usually adopt the ways that reducing the speed or changing direction of travel to avoid dangerous situations. But these judgement usually are not accurate enough. Automobile anti-rear-end intelligent control system as a vehicle driving assist system, established a relatively safe and reasonable driving distance model. The degree of potential risk of the target in the front can be accurately determined. It is not only ensuring the safety of vehicles, while maintaining a good road capacity as much as possible to maintain the desired safety distance.
REFERENCES
[1] Zhou Li. The research about automotive collision avoidance radar.
2008,6.
[2] Sheng Huaimao. The research of key technologies about millimeter-wave FMCW radar front-end integration used in car collision avoidance. 2002,3
[3] Pan Zhuojin (translator). C8051f020/1/2/3 mixed signal ISP FLASH
micro controller datasheet Rev1.1 2002.6.
[4] Kong Jinsheng, Guo Fei, Wang Xiping. The method avoid from the rear-end collision based on safe distance model of the automobile[J]. Microcomputer Information, 2008, 24: 251-252.
[5] Guo Hairu, Wan Xing, Cheng Xuan. Controller of Automobile Anti-Collision Based on Fuzzy Logic [J] . Ordnance Industry Automation ,2010-11
Braking Force V
( velocity)
R (distance between the vehicles)
M Z B S
(very small) (small) (moder(big)
at)
B B M B S B Z B B B B B B B B M S M S Z
IV. SUMMARY
How to maintain the proper distance of the vehicle is the key issues in the driving process. When spacing is too large, road capacity would be reduced ; when spacing is too small, the possibility of traffic accidents would be increased. The
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