Design of Velocity-Measuring System with Doppler Radar Concept
Contents
1. x 0 e yes p r DN X 0 a 5 p x 4 l a bo n A eo yore X 1 x 2 x nr be pT A ae X 2 6 e lt oe tbo 7 0 X 3 U re DAVAT ot gt H x 5 eo be aod pe j NE fh Ae X 5 x S e nye X j i4 be of N TRE X 6 7 Gs a BZ he X 7 Stage 0 Stage Stage 2 Figure 3 8 Point FFT The butterfly simply represents following operations on complex numbers x x W ay y x Wiy Where x and y are input values x and y are output values As we can see there s one complex multiplication in one butterfly Since in one stage we use N 2 butterflies and there are log N stages total number of complex N multiplications in FFT algorithm equals 9 log N as written earlier Let s sum up by computing FFT for N samples of input signal x n sampled with some sampling frequency fs we received sequence of N complex numbers X m the Fourier transform But X m sequence directly doesn t consist any information about frequencies or voltages of FFT bins bin is a value assigned to some m index That s how FFT results should be interpreted 7 Leakage phenomenon Is price we pay for making smooth things discreet One of methods of decreasing leakage s effects is windowing of input signals It can be done by multiplying x n sequence s values by special window function It ensures that signal values are the same or very close at begin n O and at the end n N 1 of sampling time range We ha2. Therefore it entirely can be applied to traffic management departments in order to enhance the traffic safety 26 All Rights Reserved 2012 IJARECE ISSN 2278 909X International Journal of Advanced Research in Electronics and Communication Engineering IJARECE REFERENCES 1 Yi Zeng Jianmin Xu and Deng Peng Radar Velocity measuring System Design and Computation Algorithm Based on ARM Processor IEEE 2010 2 Andrew N Sloss Dominic Symes Chris Wright ARM system developer s guide designing and optimizing system software American Elsevier PteLtd 2005 pp 1 306 3 Bruce R Hellinga Improving freeway speed estimates from single loop detectors Journal of Transportation Engineering 2002 pp 58 67 4 Huei Yung Lin Kun Jhih Li Chia Hong Chang Vehicle speed detection from a single motion blurred image Image and Vision Computing 26 2008 pp 1327 1337 5 LIU Chang wen LU Yao LIU Jie LU Fei Spectrum analyzing laser velocimetric system Opto Electronic Engineering 31 2004 pp 52 55 6 W Kleinhempel D Bergmann W Stammler Speed measure of vehicles with on board Doppler radar IEE Conference Publication Oct 12 13 1992 pp 284 287 7 Yun Nan Chang Keshab K Parhi An efficient pipelined FFT architecture IEEE Transactions on Circuits and Systems II 2003 50 6 pp 322 325 8 Tanno K Takeda T Horiguchi S Parallel radix 4 FFT algorithms on an
3. pretreatment the analog signal will be put into the ARM s ADC module for sampling convert into a digital signal and then use ARM to carry out digital signal processing ultimately use ARM control module to communicate with the PC to set the speeding threshold value in the keyboard to display the real time velocity to set speeding violation alarm by a buzzer and some other functions The hardware block diagram of these two parts is shown in Figure 2 Figure 2 Hardware block diagram of these two parts The digital signal processing part fully uses the ARM s underlying hardware resources and it is achieved by software design that is the digital signal which is produced from the ADC module will use the spectrum analysis to estimate the frequency and velocity This part will be adequately described in the following software design part The design of the system s peripherals control part such as LCD circuit PC and so on they are common circuits so this paper will no longer describe its composition 3 3 THE SOFTWARE DESIGN OF RADAR SIGNAL PROCESSING SYSTEM The system s software design uses mixed programming which includes ARM _ assembly language and C programming language in which the ARM assembly language is to achieve the key algorithm FFT algorithm while pretreatment part of the radar signal and follow up processing section of the spectrum analysis use C language for the program The main task of radar digital signa
4. Communication Engineering IJARECE achieve the radar velocity measuring system It can be used in traffic enforcement agency for measuring speeding violations and will be a new trend in the development of the radar velocity measuring system Il THE STRUCTURE AND RELATED PRINCIPLES OF RADAR VELOCITY MEASURING SYSTEM The ARM based radar velocity measuring system mainly includes two parts radar signal pretreatment part and radar signal processing system As millimeter wave radar has advantages of narrow angle high resolution anti interference ability and small size these qualities of design of radar transceiver frontend is developed by the radar hardware simulation unit which generates the frequency of the input signal within the range of ADC As for the radar signal processing system the specific design will be highlighted in Chapter 3 Firstly it will introduce the basic principles of radar velocity measurement and the signal processing principles in the radar signal processing system 2 1 DOPPLER PRINCIPLES OF RADAR VELOCITY MEASUREMENT Measurement of the target velocity by radar mainly uses the Doppler Effect to carry out The fixed frequency electromagnetic waves which are launched by the radar transceiver front end will be bounced back when it encounters objects in the transmission process If the encountered objects are stationary then the frequency of bounced back waves will not change If the encountered objects moved t
5. ADAR signal and finally generate the Doppler shift component and it will be applied to ADC input of the ARM microcontroller After analog to digital conversion FFT will be computed to find the frequency of the input signal As the ARM7 doesn t have any DSP blocks for implementing FFT we develop routines in C In the final stage of velocity computation the velocity is calculated based on the measured frequency component The measured result will be displayed on LCD and the spectrum of the frequency will be sent to PC through serial port The ARM7TDMI NXP s LPC2148 microcontroller is used for this task Index Terms ARM Doppler effect FFT algorithm Radar Velocity Measuring I INTRODUCTION The real time monitoring of vehicles velocity has become essential for traffic safety Because with the rapid development of the transportation industry on the one hand it promotes the economic and social prosperity on the other hand the modern intelligent traffic management and the traffic safety has been pushed to an unprecedented height This extensive research topic has become an important world issue and how to measure the velocity of vehicles is an important part of it Speeding has been the main causation for traffic accidents so the real time monitoring of vehicles velocity has become essential for traffic management and traffic safety At present there are many ways of velocity measurement including the coil method 3 image pro
6. ISSN 2278 909X International Journal of Advanced Research in Electronics and Communication Engineering IJARECE Volume I Issue 4 October 2012 Design of Velocity Measuring System with Doppler Radar Concept and FFT Algorithm Based On ARM Processor for Traffic Safety Mr GUMMAREKULA SATTIBABU Mrs CH SRIDEVI Mr T SIVA SANKAR PHANI Mrs S GANIKA SRIDEVI 1 PG Scholar Department of ECE BVC Engineering College Odalarevu A P Associate Professor Department of ECE BVC Engineering College Odalarevu A P 3 gt 4 Assistant Professor Department of ECE BVC Engineering College Odalarevu A P Abstract The real time monitoring of vehicles velocity has become essential for traffic safety Since Traffic control is one of the largest challenges in cities and metros Therefore in turn to improve the method of monitoring the velocity of vehicles on road this paper has designed a new radar based velocity measuring system which is based on ARM processor This system uses the Doppler principle and spectral estimation FFT algorithm in its hardware design part and it takes full use of the underlying resources of ARM processor The implementation of digital processor portion of the RADAR velocity measuring system is prototyped on ARM7 TDMI based LPC2148 microcontroller The project aims to evolve a low cost DSP solution for such applications The radar signal pretreatment block address all the issues involved with R
7. X 1 we should perform XN multiplication operations Since X m is a sequence of N complex numbers the total number of complex multiplication 2 operations equals NV As written above it turned out that many operations made while computing DFT are not necessary In 1965 Cooley and Tuckey presented FFT algorithm which needs only pe log N complex multiplication operations for computing X m for N input values Let s assume that we have to compute DFT of N 8192 samples Using DFT we would have to perform approx 1200 times more multiplication operations than while using FFT Even for N 256 the gain is big When we use FFT we have to perform 1024 multiplication operations instead 65536 when using DFT FFT algorithm works well also for N not being integer power of 2 But in practice N often equals integer power of 2 and such version of FFT will be discussed 8 Let s consider an example Assume that N 8 Operations which have to be performed to compute 8 point FFT can be drawn in graphed form as shown at Figure 3 If two arrows ends meet in one point it means that number assigned to this point is sum of two numbers k assigned to begin of arrows multiplied by Wy Of course if no number is written on some arrow then it means multiplication by 1 24 All Rights Reserved 2012 IJARECE ISSN 2278 909X International Journal of Advanced Research in Electronics and Communication Engineering IJARECE
8. _ eight neighbor processor array IEEE TENCON 92 1992 pp 855 859 9 Yan Feng Li Kui Fu Chen Eliminating the picket fence effect of the fast Fourier transform Computer Physics Communications 178 2008 pp 486 491 10 Richard G Lyons Understanding Digital Signal Processing 11 Fixed Point Arithmetic on the ARM ARM DAT 0033A Advanced RISC Machines Ltd ARM 1996 pdf 12 Volume 1 LPC214x User Manual Rev 01 15 August 2005 User manual Philips Semiconductors pdf All Rights Reserved 2012 IJARECE Volume I Issue 4 October 2012 27
9. cessing method 4 laser Doppler velocimetry 5 radar velocity measuring system etc 6 The last two methods have been widely used due to its portability and high accuracy advantages The laser Doppler velocimetry though it has high accuracy long effective distance advantages but also has shortcomings as only in the stationary state to use easy to be found by driver expensive and so on The radar velocity measuring system signals are in larger and higher resolution and device can be moved from one place to another easily and can be used anywhere Although it s effective distance is less than the laser velocimetry it also can meet the requirements of high accuracy and can be used in stationary and motion state moreover it has become popular due to the mature technology and affordable price As early as 1970s western countries began to use radar velocity measuring system but these products are analog large and with low accuracy To 1990s a new radar velocity measuring system appeared which contained integrated circuits digital signal processor and worked in the Ka band compared with the analog one it has advantages of high accuracy and small size 1 In respect of implementation technology several generations of radar velocity measuring system has appeared with the development of microcontroller and microprocessor chip The first generation product uses single chip to implement This single chip needs to complete the co
10. dal signal which is generated by function generator from this diagram we can see that its frequency is 9 5 kHz the third diagram is the value of frequency spectrum through the core algorithm the measured signal frequency is 9 45 kHz Compare with the true frequency 9 5 kHz the frequency measurement accuracy of this algorithm is very high which can reach more than 99 The sampling points N in here are only 256 We can choose N 1024 4096 in the program then its frequency measurement accuracy will be higher ISSN 2278 909X International Journal of Advanced Research in Electronics and Communication Engineering IJARECE Volume I Issue 4 October 2012 ARM Spectrum Analyzer Entry ART 31 X 9 45kHz Y 0 86V F 0 00kHz V 000V EKE Run Window Hanning Figure 7 The result diagrams of the test 5 CONCLUSION In order to improve the method of monitoring the velocity of vehicles on road this paper describes the radar based velocity measuring system design and algorithm research based on ARM7TDMI The characteristics of this design are reflected by using single core ARM processor to achieve the dual core task which is traditionally completed by DSP plus single chip and it has laid the foundation for ARM s DSP application The test results show that the accuracy of this system can fully meet the requirements of traffic law enforcement agencies and have the advantages of small size low cost low power consumption etc
11. igital signal processing chip there is no single command to achieve the multiply accumulate and parallel data access However with the ARM architecture fortified making ARM slowly can be applied to many DSP applications For ARM7TDMI and the beyond ARM processor simply by careful clever software design it can get a higher performance in digital signal processing section of the application system while in the control part of the application system can also significantly better than DSP chips Therefore radar signal processing system based on ARM is entirely feasible and it has simple hardware design low cost and low power consumption advantages Here we choose the LPC2148 NXP ARM chip to be the main processor of the system The system s hardware architecture mainly includes three parts pretreatment part of the radar signal digital signal processing part and peripherals control part of the system 3 1 THE DESIGN OF RADAR SIGNAL PRETREATMENT PART The Protection circuit using in this project is to set the analog signals to reference voltage of Ov to 3 3v coming from the hardware simulation unit function generator as our microcontroller can work from a reference voltage of Ov to 3 3v So if we get any voltage other than this amplitude the ADC of LPC2148 microcontroller cannot convert to digital And also if we get any negative amplitude voltages this circuit converts to offset levels The unit actually consists of two resistors to gi
12. l processing systems software design is to carry out the sampling operation pretreatment spectrum operation output and display of the operation results for the Doppler radar signal which passed from the radar hardware simulation unit Volume I Issue 4 October 2012 3 3 1 FFT ALGORITHM IMPLEMENTATION ON THE ARM PROCESSOR FFT algorithm needs to handle a lot of floating point operations further more it has high requirements in the multiply accumulate and data access aspect while the ARM processor does not support hardware floating point operations 12 and there is no single instruction to achieve multiply accumulate and parallel data access Forasmuch it is necessary to compare FFT s various implementation ways and select a good method 11 The Fourier transform of x t signal is given by formula X f x t e dt If we consider x t function as sequence x n composed of N samples of input signal took by A D converter than Fourier transform would be given so N 1 X m gt slanje N n 0 It is a DFT formula For real world signals we assume that x n values are real numbers which represent values of those signals given simply in volts DFT result for input N samples of x n signal is set of N complex values X m The DFT formula could be simply used to compute spectrum of input signal But let s watch how many complex multiplication operations had to be performed To receive one value of X m sequence for example
13. ntrol functions also needs to complete the core algorithm of velocity measuring system but these algorithms are limited to a few simple low precision algorithms such as counting cycles method and so on The final product can achieve velocity measurement but the accuracy is not enough and the speed of systems operation is very slow The second generation product uses single chip plus DSP Digital Signal Processing processor which uses the traditional dual core mode that is one single chip is to deal with the control system and another separate DSP processor is to complete the part of digital signal processing This way can achieve the core algorithm that contains a large number of complex operations The accuracy and speed of this generation products are much higher than the first generation products With the emergence and extensive application of ARM processors its rich peripheral control module and the underlying hardware resources make it possible to achieve the second generation product that is to say just use of ARM single core will be able to complete the traditional dual core task not only can greatly simplify the complex hardware design of the second generation product but also have low cost low power consumption advantages 2 Therefore the innovation of this paper lies in using ARM processor to 22 All Rights Reserved 2012 IJARECE ISSN 2278 909X International Journal of Advanced Research in Electronics and
14. o set up the project as it is equipped with all necessary peripherals such as LCD interface UARTO UARTI1 and User Switches The LPC2148 samples the input signal with sampling frequency of 40 kHz where a built in analog to digital converter is used Cipseesttetsyyt cccccccs z Figure 6 ARM7 LPC2148 development board The 256 point Fast Fourier Transform FFT algorithm is performed after getting 256 samples of the signal There are 256 complex numbers that comprise the result of FFT The amplified spectrum of the signal comes from dividing the real and imaginary parts of those numbers by 128 and absolute values of them are displayed The spectrum is sent to the PC via RS232 interface and the spectrum is displayed using specially created Windows application For software developing I used Keil s uVision4 development environment along with ARM GCC compiler For flash programming the LPC2000 Flash Utility V2 2 1 has been used 4 TEST RESULTS For testing the accuracy of the core algorithm we have produced a fine tuned sinusoidal signal from a function generator and used this signal as a good pretreatment radar signals input to the ARM processor then through the serial port the Doppler frequency which is calculated by the program will be sent to the PC and displayed on the screen The first diagram of Figure 7 shows the hardware results of measured velocity through the Doppler frequency component the second diagram is a sinusoi
15. oward the direction of wave source the waves bounced back at this time will be compressed its frequency will increase On the contrary if the movement away from the wave source the received echo frequency will be lower than the launch frequency 6 Among them the increase or decrease of frequency value is called the Doppler frequency decided by the following equation fp f 1 Where fa is Doppler frequency v is the velocity of target vehicle C is the speed of light f is the launch frequency of radar wave From 1 we can get y a fa E 2 2 fa From 2 we can see other variables are known as long as the Doppler frequency is worked out we can calculate the target vehicle velocity 2 2 THE SIGNAL PROCESSING PRINCIPLES OF THE SYSTEM From the above Doppler principles we can see that through estimating the Doppler frequency of radar echo signal we can complete the velocity estimation of target vehicle Among them the measurement error of frequency directly affects the measurement results of velocity The Volume 1 Issue 4 October 2012 use of FFT algorithm is a kind of traditional spectral estimation it is not only has the high accuracy of frequency estimation but also can complete real time signal processing Therefore we choose this method as the core algorithm of frequency measurement in the system M THE DESIGN OF RADAR SIGNAL PROCESSING SYSTEM Unlike DSP processor ARM processor is not a dedicated d
16. ve an offset voltage or reference voltage using voltage divider rule As the two resistors values are same the converted voltage is half of the input voltage giving So as we give supply of 3 3 volts to this circuit it converts any other voltages to within the range of Ov to 3 3v by taking offset voltage as 1 65v 1 e reference voltage Here every maximum positive peak of signal is 3 3v and every negative peak is with Ov and taking reference voltage as 1 65v So here we are using the capacitor to clipping the positive and negative peaks to block and set to reference voltage The hardware block diagram of this part is shown in Figure 1 Protection Unit or 3V Luter Circuit Radar Hardware Simulation Unit Figure 1 Hardware block diagram of the radar signal pretreatment part 23 All Rights Reserved 2012 IJARECE ISSN 2278 909X International Journal of Advanced Research in Electronics and Communication Engineering IJARECE The design of Radar signal pretreatment part is directly related to the back end software s velocity measurement accuracy that is even if the back end frequency estimation algorithm is very accurate as long as the radar signal s pretreatment has a little distortion it also will reduce the back end velocity measurement accuracy 3 2 THE DESIGN OF SIGNAL PROCESSING AND PERIPHERALS CONTROL PART ARM processor is the core of these two parts of hardware design First through the radar signal
17. ve to remember that window function only decreases leakage s effects and do not eliminate them 9 There is also no universal window function good for every purpose There are dozens of window functions everyone has different features In practice Hanning and Hamming window functions are often used and spectrum analyzer described here provides both of them Figure 4 shows Hanning and Hamming functions Figure 5 shows an influence of Hanning window on DFT leakage 10 Volume I Issue 4 October 2012 HANNING WINDOW HAMMING WINDOW Figure 4 Hanning and Hamming functions Without Window With Hanning Window ix m IX m No Leakage Figure 5 Influence of Hanning window on DFT leakage 3 3 2 IMPLEMENTATION OF SPECTRUM ANALYZER ON LPC2148 MICROCONTROLLER The main loop of spectrum analyzer software performs the following actions periodically in the microcontroller Getting 256 samples of input signal Multiplying samples by window function chosen by the user Computing 256 point FFT Computing squares of absolute values of FFT result Checking if any request came from PC Sending spectrum when request received This spectrum analyzer utilizes an ARM7 LPC2148 microcontroller to create an FFT algorithm while performing digital signal processing without the use of special DSP processor and it is shown in Figure 6 ARM7 25 All Rights Reserved 2012 IJARECE LPC2148 development board is used t
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