1、rs in the synthesis of her time the citydrainage system. In particular drainage system often lags behind urban construction.Therefore there are often good building excavation has been building facilities to upgradethe drainage system phenomenon. It brought to the city sewage and it is clear to the c
2、itysewage and drainage culvert in the sewage treatment system. comfort is very important topeoples lives. Mobile robots designed to clear the drainage culvert and the automaticcontrol system Free sewage culvert clear guarantee robot the robot is designed to clear theculvert sewage to the core. Contr
3、ol System is the core component of the development ofultrasonic range finder. Therefore it is very important to design a good ultrasonic rangefinder.2. A principle of ultrasonic distance measurement 2.1 The principle of piezoelectric ultrasonic generator Piezoelectric ultrasonic generator is the use
4、 of piezoelectric crystal resonators to work.Ultrasonic generator the internal structure as shown it has two piezoelectric chip and aresonance plate. When its two plus pulse signal the frequency equal to the intrinsicpiezoelectric oscillation frequency chip the chip will happen piezoelectric resonan
5、ce andpromote the development of plate vibration resonance ultrasound is generated. Converselyif the two are not inter-electrode voltage when the board received ultrasonic resonance itwill be for vibration suppression of piezoelectric chip the mechanical energy is convertedto electrical signals then
6、 it becomes the ultrasonic receiver. The traditional way to determine the moment of the echos arrival is based onthresholding the received signal with a fixed reference. The threshold is chosen well abovethe noise level whereas the moment of arrival of an echo is defined as the first moment theecho
7、signal surpasses that threshold. The intensity of an echo reflecting from an objectstrongly depends on the objects nature size and distance from the sensor. Further the timeinterval from the echos starting point to the moment when it surpasses the thresholdchanges with the intensity of the echo. As
8、a consequence a considerable error may occurEven two echoes with different intensities arriving exactly at the same time will surpass thethreshold at different moments. The stronger one will surpass the threshold earlier than theweaker so it will be considered as belonging to a nearer object.2.2The
9、principle of ultrasonic distance measurement Ultrasonic transmitter in a direction to launch ultrasound in the moment to launch thebeginning of time at the same time the spread of ultrasound in the air obstacles on his wayto return immediately the ultrasonic reflected wave received by the receiver i
10、mmediatelystop the clock. Ultrasound in the air as the propagation velocity of 340m / s according tothe timer records the time t we can calculate the distance between the launch distancebarrier s that is: s 340t / 23.Ultrasonic Ranging System for the Second Circuit Design System is characterized by
11、single-chip microcomputer to control the use of ultrasonictransmitter and ultrasonic receiver since the launch from time to time single-chip selectionof 8751 economic-to-use and the chip has 4K of ROM to facilitate programming. Circuitschematic diagram shown in Figure 2. Figure 1 circuit principle d
12、iagram 3.1 40 kHz ultrasonic pulse generated with the launch Ranging system using the ultrasonic sensor of piezoelectric ceramic sensors UCM40its operating voltage of the pulse signal is 40kHz which by the single-chip implementationof the following procedures to generate.puzel: mov 14h 12h ultrasoni
13、c firing continued 200mshere: 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 single chipimplementation of the above procedure the P1.0 port in a 40kHz pulse output signal afteramplification transistor T the drive to
14、 launch the first ultrasonic UCM40T issued 40kHzultrasonic pulse and the continued launch of 200ms. Ranging the right and the left side ofthe circuit respectively then input port P1.1 and P1.2 the working principle and circuit infront of the same location.3.2 Reception and processing of ultrasonic U
15、sed to receive the first launch of the first pair UCM40R the ultrasonic pulsemodulation signal into an alternating voltage the op-amp amplification IC1A and afterpolarization IC1B to IC2. IC2 is locked loop with audio decoder chip LM567 internalvoltage-controlled oscillator center frequency of f0 1/
16、1.1R8C3 capacitor C4 determinetheir target bandwidth. R8-conditioning in the launch of the carrier frequency on theLM567 input signal is greater than 25mV the output from the high jump 8 feet into alow-level as interrupt request signals to the single-chip processing. Ranging in front of single-chip
17、termination circuit output port INT0 interrupt thehighest priority right or left location of the output circuit with output gate IC3A accessINT1 port single-chip while single-chip P1.3 and P1.4 received input IC3A interrupted by the process to identify the source of inquiry to deal with interrupt pr
18、iority level for thefirst left right after. Part of the source code is as follows:receive1: push psw push acc clr ex1 related external interrupt 1 jnb p1.1 right P1.1 pin to 0 ranging from right to interrupt serviceroutine circuit jnb p1.2 left P1.2 pin to 0 to the left ranging circuit interruptserv
19、ice routinereturn: SETB EX1 open external interrupt 1 pop acc pop psw retiright: . right location entrance circuit interrupt service routine Ajmp Returnleft: . left Ranging entrance circuit interrupt service routine Ajmp Return3.3 The calculation of ultrasonic propagation time When you start firing
20、at the same time start the single-chip circuitry within the timerT0 the use of timer counting function records the time and the launch of ultrasonicreflected wave received time. When you receive the ultrasonic reflectedwave the receivercircuit outputs a negative jump in the end of INT0 or INT1 inter
21、rupt request generates asignal single-chip microcomputer in response to external interrupt request theimplementation of the external interruptservice subroutine read the time differencecalculating the distance . Someof its source code is as follows: RECEIVE0: PUSH PSWPUSH ACCCLR EX0; related externa
22、l interrupt 0MOV R7, TH0; read the time valueMOV R6, TL0CLR CMOV A, R6SUBB A, # 0BBH; calculate the time differenceMOV 31H, A; storage resultsMOV A, R7SUBB A, # 3CHMOV 30H, ASETB EX0; open external interrupt 0POP ACCPOP PSWRETIFor a flat target, a distance measurement consists of two phases: a coars
23、e 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 equati-on , until the echo is detected.Step 3: Detection of the amplitudes and zero-crossing times of both echoes.Step 4: S
24、etting 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 produce an interfered wave. Testing the zero-crossin
25、g 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 ultrasonic ranging system software design
26、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 complete three of the rotation direction of ul
27、trasonic 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. ConclusionsRequired measuring range of 30cm 200cm objects inside the plane to do a number of measurements found that the maximum error is
28、 0.5cm, and good reproducibility. Single-chip design can be seen on the ultrasonic ranging system has a hardware structure is simple, reliable, small features such as measurement error. Therefore, it can be used not only for mobile robot can be used in other detection systems.Thoughts: As for why th
29、e receiver do not have the transistor amplifier circuit, because the magnification well, integrated amplifier, but also with automatic gain control level, magnification to 76dB, the center frequency is 38k to 40k, is exactly resonant ultrasonic sensors frequency.Ultrasonic ranging system design Publication title: Sensor Review. Bradford: 1993. Vol. 13.明买2个乒乓球和4个皮球共用去52元，6个乒乓球的价钱相当于1个皮球的价钱.乒乓球和皮球的单
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