超声测距系统设计汽车电子毕设设计外文文献翻译.pdf

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1、Ultrasonic ranging system design Publication title:Sensor Review.Bradford:1993.Vol.ABSTRACT:Ultrasonic ranging technology has wide using worth in many fields,such as the industrial locale,vehicle navigation and sonar engineering.Now it has been used in level measurement,self-guided autonomous vehicl

2、es,fieldwork robots automotive navigation,air and underwater target detection,identification,location and so on.So there is an important practicing meaning to learn the ranging theory and ways deeply.To improve the precision of the ultrasonic ranging system in hand,satisfy the request of the enginee

3、ring personnel for the ranging precision,the bound and the usage,a portable ultrasonic ranging system based on the single chip processor was developed.Keywords:Ultrasound,Ranging System,Single Chip Processor 1.Introductive With the development of science and technology,the improvement of peoples sta

4、ndard of living,speeding up the development and construction of the city.Urban drainage system have greatly developed their situation is construction improving.However,due to historical reasons many unpredictable factors in the synthesis of her time,the city drainage system.In particular drainage sy

5、stem often lags behind urban construction.Therefore,there are often good building excavation has been building facilities to upgrade the drainage system phenomenon.It brought to the city sewage,and it is clear to the city sewage and drainage culvert in the sewage treatment system.Comfort is very imp

6、ortant to peoples lives.Mobile robots designed to clear the drainage culvert and the automatic control system Free sewage culvert clear guarantee robots,the robot is designed to clear the culvert sewage to the core.Control system is the core component of the development of ultrasonic range finder.Th

7、erefore,it is very important to design a good ultrasonic range finder.2.A principle of ultrasonic distance measurement The application of AT89C51:SCM is a major piece of computer components are integrated into the chip micro-computer.It is a multi-interface and counting on the micro-controller integ

8、ration,and intelligence products are widely used in industrial automation.and MCS-51 microcontroller is a typical and representative.Microcontrollers are used in a multitude of commercial applications such as modems,motor-control systems,air conditioner control systems,automotive engine and among ot

9、hers.The high processing speed and enhanced peripheral set of these microcontrollers make them suitable for such high-speed event-based applications.However,these critical application domains also require that these microcontrollers are highly reliable.The high reliability and low market risks can b

10、e ensured by a robust testing process and a proper tools environment for the validation of these microcontrollers both at the component and at the system level.Intel Plaform Engineering department developed an object-oriented multi-threaded test environment for the validation of its AT89C51 automoti

11、ve microcontrollers.The goals of this environment was not only to provide a robust testing environment for the AT89C51 automotive microcontrollers,but to develop an environment which can be easily extended and reused for the validation of several other future microcontrollers.The environment was dev

12、eloped in conjunction with Microsoft Foundation Classes(AT89C51).1.1 Features *Compatible with MCS-51 Products *2Kbytes of Reprogrammable Flash Memory Endurance:1,000Write/Erase Cycles *2.7V to 6V Operating Range *Fully Static operation:0Hz to 24MHz *Two-level program memory lock *128x8-bit internal

13、 RAM *15programmable I/O lines *Two 16-bit timer/counters *Six interrupt sources *Programmable serial UART channel *Direct LED drive output *On-chip analog comparator *Low power idle and power down modes 1.2 Description The AT89C2051 is a low-voltage,high-performance CMOS 8-bit microcomputer with 2K

14、bytes of flash programmable and erasable read only memory(PEROM).The device is manufactured using Atmels high density nonvolatile memory technology and is compatible with the industry standard MCS-51 instruction set and pinout.By combining a versatile 8-bit CPU with flash on a monolithic chip,the At

15、mel AT89C2051 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.The AT89C2051 provides the following standard features:2Kbytes of flash,128bytes of RAM,15 I/O lines,two 16-bit timer/counters,a five vector two-level interrup

16、t architecture,a full duplex serial port,a precision analog comparator,on-chip oscillator and clock circuitry.In addition,the AT89C2051 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes.The idle mode stops the CPU while allowin

17、g the RAM,timer/counters,serial port and interrupt system to continue functioning.The power down mode saves the RAM contents but freezer the oscillator disabling all other chip functions until the next hardware reset.1.3 Pin Configuration 1.4 Pin Description VCC Supply voltage.GND Ground.Prot 1 Prot

18、 1 is an 8-bit bidirectional I/O port.Port pins P1.2 to P1.7 provide internal pullups.P1.0 and P1.1 require external pullups.P1.0 and P1.1 also serve as the positive input(AIN0)and the negative input(AIN1),respectively,of the on-chip precision analog comparator.The port 1 output buffers can sink 20m

19、A and can drive LED displays directly.When 1s are written to port 1 pins,they can be used as inputs.When pins P1.2 to P1.7 are used as input and are externally pulled low,they will source current(IIL)because of the internal pullups.Port 3 Port 3 pins P3.0 to P3.5,P3.7 are seven bidirectional I/O pin

20、s with internal pullups.P3.6 is hard-wired as an input to the output of the on-chip comparator and is not accessible as a general purpose I/O pin.The port 3 output buffers can sink 20mA.When 1s are written to port 3 pins they are pulled high by the internal pullups and can be used as inputs.As input

21、s,port 3 pins that are externally being pulled low will source current(IIL)because of the pullups.Port 3 also serves the functions of various special features of the AT89C2051 as listed below.1.5 Programming the Flash The AT89C2051 is shipped with the 2 Kbytes of on-chip PEROM code memory array in t

22、he erased state(i.e.,contents=FFH)and ready to be programmed.The code memory array is programmed one byte at a time.Once the array is programmed,to re-program any non-blank byte,the entire memory array needs to be erased electrically.Internal address counter:the AT89C2051 contains an internal PEROM

23、address counter which is always reset to 000H on the rising edge of RST and is advanced applying a positive going pulse to pin XTAL1.Programming algorithm:to program the AT89C2051,the following sequence is recommended.1.power-up sequence:Apply power between VCC and GND pins Set RST and XTAL1 to GND

24、With all other pins floating,wait for greater than 10 milliseconds 2.Set pin RST to H set pin P3.2 to H 3.Apply the appropriate combination of H or L logic to pins P3.3,P3.4,P3.5,P3.7 to select one of the programming operations shown in the PEROM programming modes table.To program and Verify the Arr

25、ay:4.Apply data for code byte at location 000H to P1.0 to P1.7.5.Raise RST to 12V to enable programming.5.Pulse P3.2 once to program a byte in the PEROM array or the lock bits.The byte-write cycle is self-timed and typically takes 1.2ms.6.To verify the programmed data,lower RST from 12V to logic H l

26、evel and set pins P3.3 to P3.7 to the appropriate levels.Output data can be read at the port P1 pins.7.To program a byte at the next address location,pulse XTAL1 pin once to advance the internal address counter.Apply new data to the port P1 pins.8.Repeat steps 5 through 8,changing data and advancing

27、 the address counter for the entire 2 Kbytes array or until the end of the object file is reached.9.Power-off sequence:set XTAL1 to L set RST to L Float all other I/O pins Turn VCC power off 2.1 The principle of piezoelectric ultrasonic generator Piezoelectric ultrasonic generator is the use of piez

28、oelectric crystal resonators to work.Ultrasonic generator,the internal structure as shown,it has two piezoelectric chip and a resonance plate.When its two plus pulse signal,the frequency equal to the intrinsic piezoelectric oscillation frequency chip,the chip will happen piezoelectric resonance,and

29、promote the development of plate vibration resonance,ultrasound is generated.Conversely,it will be for vibration suppression of piezoelectric chip,the mechanical energy is converted to electrical signals,then it becomes the ultrasonic receiver.The traditional way to determine the moment of the echos

30、 arrival is based on thresholding the received signal with a fixed reference.The threshold is chosen well above the noise level,whereas the moment of arrival of an echo is defined as the first moment the echo signal surpasses that threshold.The intensity of an echo reflecting from an object strongly

31、 depends on the objects nature,size and distance from the sensor.Further,the time interval from the echos starting point to the moment when it surpasses the threshold changes with the intensity of the echo.As a consequence,a considerable error may occur even two echoes with different intensities arr

32、iving exactly at the same time will surpass the threshold at different moments.The stronger one will surpass the threshold earlier than the weaker,so it will be considered as belonging to a nearer object.2.2 The principle of ultrasonic distance measurement Ultrasonic transmitter in a direction to la

33、unch ultrasound,in the moment to launch the beginning of time at the same time,the spread of ultrasound in the air,obstacles on his way to return immediately,the ultrasonic reflected wave received by the receiver immediately stop the clock.Ultrasound in the air as the propagation velocity of 340m/s,

34、according to the timer records the time t,we can calculate the distance between the launch distance barrier(s),that is:s=340t/2 3.Ultrasonic Ranging System for the Second Circuit Design System is characterized by single-chip microcomputer to control the use of ultrasonic transmitter and ultrasonic r

35、eceiver since the launch from time to time,single-chip selection of 875,economic-to-use,and the chip has 4K of ROM,to facilitate programming.3.1 40 kHz ultrasonic pulse generated with the launch Ranging system using the ultrasonic sensor of piezoelectric ceramic sensors UCM40,its operating voltage o

36、f the pulse signal is 40kHz,which by the single-chip implementation of the following procedures to generate.puzel:mov 14h,#12h;ultrasonic firing continued 200ms Here:cpl p1.0;output 40kHz square wave nop;nop;nop;djnz 14h,here;ret Ranging in front of single-chip termination circuit P1.0 input port,si

37、ngle chip implementation of the above procedure,the P1.0 port in a 40kHz pulse output signal,after amplification transistor T,the drive to launch the first ultrasonic UCM40T,issued 40kHz ultrasonic pulse,and the continued launch of 200ms.Ranging the right and the left side of the circuit,respectivel

38、y,then input port P1.1 and P1.2,the working principle and circuit in front of the same location.3.2 Reception and processing of ultrasonic Used to receive the first launch of the first pair UCM40R,the ultrasonic pulse modulation signal into an alternating voltage,the op-amp amplification IC1A and af

39、ter polarization IC1B to IC2.IC2 is locked loop with audio decoder chip LM567,internal voltage-controlled oscillator center frequency of f0=1/1.1R8C3,capacitor C4 determine their target bandwidth.R8-conditioning in the launch of the high jump 8 feet into a low-level,as interrupt request signals to t

40、he single-chip processing.Ranging in front of single-chip termination circuit output port INT0 interrupt the highest priority,right or left location of the output circuit with output gate IC3A access INT1 port single-chip,while single-chip P1.3 and P1.4 received input IC3A,interrupted by the process

41、 to identify the source of inquiry to deal with,interrupt priority level for the first left right after.Part of the source code is as follows:Receivel:push psw push acc clr ex1;related external interrupt 1 jnb p1.1,right;P1.1 pin to 0,ranging from right to interrupt service routine circuit jnb p1.2,

42、left;P1.2 pin to 0,to the left ranging circuit interrupt service routine return:SETB EX1;open external interrupt 1 pop acc pop psw reti right:;right location entrance circuit interrupt service routine Ajmp Return left:;left ranging entrance circuit interrupt service routine Ajmp Return 3.3 The calcu

43、lation of ultrasonic propagation time When you start firing at the same time start the single-chip circuitry within the timer T0,the use of timer counting function records the time and the launch of ultrasonic reflected wave received time.When you receive the ultrasonic reflected wave,the receiver c

44、ircuit output a negative jump in the end of INT0 or INT1 interrupt request generates a signal,single-chip microcomputer in response to external interrupt request,the implementation of the external interrupt service subroutine,read the time difference,calculating the distance.Some of its source code

45、is as follows:RECEIVE0:PUSH PSW PUSH ACC CLR EX0;related external interrupt 0 MOV R7,TH0;read the time value MOV R6,TL0 CLR C MOV A,R6 SUBB A,#0BBH;calculate the time difference MOV 31H,A;storage results MOV A,R7 SUBB A,#3CH MOV 30H,A SETB EX0;open external interrupt 0 POP ACC POP PSW RETI For a fla

46、t target,a distance measurement consists of two phases:a coarse measurement and a fine measurement:Step 1:Transmission of one pulse train to produce a simple ultrasonic wave.Step 2:Changing the gain of both echo amplifiers according to equation,until the echo is detected.Step 3:Detection of the ampl

47、itudes and zero-crossing times of both echoes.Step 4:Setting the gains of both echo amplifiers to normalize the output at,say 3 volts.Setting the period of the next pulses according to the:period of echoes.Setting the time window according to the data of step 2.Step 5:Sending two pulse trains to pro

48、duce an interfered wave.Testing the zero-crossing times and amplitudes of the echoes.If phase inversion occurs in the echo,determine to otherwise calculate to by interpolation using the amplitudes near the trough.Derive t sub m1 and t sub m2.Step 6:Calculation of the distance y using equation.4、The

49、ultrasonic ranging system software design Software is divided into two parts,the main program and interrupt service routine.Completion of the work of the main program is initialized,each sequence of ultrasonic transmitting and receiving control.Interrupt service routines from time to time to complet

50、e three of the rotation direction of ultrasonic launch,the main external interrupt service subroutine to read the value of completion time,distance calculation,the results of the output and so on.5、Conclusions Required measuring range of 30cm-200cm objects inside the plane to do a number of measurem