The application of acceleration sensor ADXL50 in missile on the march
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source:TRIANA CNC Machining
Foreword carries march process in missile car in, the missile on the car can be affected by all sorts of oscillatory concussion, if this kind of oscillatory concussion passes to be able to cause the injury of missile or damage greatly. Introduced a kind to be based on ADXL50 sheet here piece the acceleration measurement technique of compositive acceleration sensor, use at detecting missile carries the oscillatory concussion that gets in march process in the car. Odd a bulk of ADXL50 of compositive acceleration sensor is small, directional good, precision is tall, when float as small as Wen Piao; In + 5V sheet works below power source, use convenient, what need periphery yuan parts of an apparatus is little; Reliability is very high, in the acceleration concussion that 500g can bear when electrify, the acceleration that 2000g can bear when appending report is pounded and do not cause damage. Because this is OK,application carries a car at missile. If the graph shows 1 times,1 design program devises plan: Include sensor and periphery circuit, signal to handle installation, show call the police the 3 parts such as circuit. Sensor and periphery circuit are enclosed within small-sized cask, solid carries drive a vehicle to go up on missile, ADXL50 acceleration sensor collects oscillatory acceleration signal, output corresponding voltage signal; Signal processing receives sensor to collect the imitate voltage signal that come partly, undertake to its modular ／ counts changeover, indicate the value of acceleration go up at LED, occupy judgement and processing into linage next, give out when exceeding safe range call the police, remind a driver the attention drives. The ADXL50 accelerometer that the design program of 2 sensor and periphery circuit drafts to use American AD company to produce regards acceleration as sensor. This parts of an apparatus is compositive in sheet piece on integrated circuit, use differential capacitance to serve as sensing element, output voltage signal directly, the collection of facilitating signal and processing. 2. The main technique index of 1ADXL50 measures sensitivity to be 19mV ／ G; Full scale measures limits to be ± 50g; Frequency answers limits to be DC ～ 1kHz; Self check can have below switch signal control; Inside buy buffer amplifier, can use at outputting sensitivity and n of 0 acceleration output to adjust. 2. 2ADXL50 job principle and measuring circuit ADXL50 basically is a complete acceleration surveys a system, it measures part of a sensor concerned circuit with the acceleration that finish, include oscillator, demodulator, preamplifier, buffer amplifier, referenced power source and temperature to compensate circuit to wait. All and compositive go up in chip of a silicon. Chip is enclosed within envelope of 10 feet T0100, the definition of this 10 feet is shown 2 times like the graph. Graph the 3 principle block diagram that are acceleration sensor. Outside using 3 among them, receive capacitance mixes 3 outside receive resistor. C1 in order to decides to measure systematic bandwidth, the capacity of C1 and C2 chooses O ～ commonly 0. 22 μ F, c2 is commonly 0. 1 μ F can. ADXL50 is in before leaving factory, manufacturer already the measurement of its preamplifier sensitivity is adjusted for 19mV ／ G, the output voltage VPR when its Og is 1. 8V. Accordingly, if acceleration is ± 50g, criterion VPR=1. 8V ± O. 95V, if acceleration is ± 20g, criterion VPR=1. 8V ± O. 38V. As a result of the signal on VPR not standard, unwell take at reading undertake indication or handle into travel digitlization. Additional, the infuse electric current of ADXL50 preamplifier can have 25 μ A only greatly most, drive capacity is very small, accordingly, the signal on VPR should do further processing, ability satisfies a requirement. General outside receive a few resistor and buffer amplifier to form an enlarge link, in order to adjust the Og potential of the VPR of sensor, heighten the sensitivity that outputs signal. Via the acceleration signal after amortize magnifies, its span had better is in 0. 5 ～ 4. Between 5V, two end have the made on any account that is apart from power source certain surplus. Be like acceleration, the metabolic extent close that loses two way, can move Og potential in 2. 5V left and right sides. Such, , the span that negative acceleration signal outputs buccal Vout to go up to have ± 2V in sensor. Set wait for the range that measures acceleration to be ± 50g, criterion VPR=1. 8V ± O, 95V, be about to make Vout=2. 5V ± 2. OV, need to magnify the communication heft in signal. The enlarge coefficient of buffer amplifier is - R3 ／ R1, so, if take R1=50k Ω , can decide R3=105k Ω . In the graph 3 in, the ground connection of one aspect of the matter of R2, to make the Vout=2 when 0g. 5V, r2 should satisfy a requirement: R2= (1. 8 × R3) ／ (Vout-1. 8) =270k Ω . 2. The item that 3ADXL50 should notice when use (1) ADXL50 has an acute axis, its direction is point to the 10th foot from the 5th foot (point to envelope to locate namely piece) , if pursue,2 are shown. What sensor measures is the acceleration along this axis. Set this axis to be X axis, set in the as perpendicular as X axis direction inside plane of sensor envelope bottom to be Y axis again. If the direction of acceleration G and sensor are bottom,the included angle between Xy plane is α , criterion acceleration G is Gxy=gcos α in the heft on Xy plane. Set the clip foot between acceleration heft Gxy and sensor delicacy axis to be β again, criterion Gxy is β of Cos of α of Gx=gxycos β =gcos in the heft on acute axis. Accordingly, when installing acceleration sensor, want to make the direction of its delicacy axis and acceleration consistent as far as possible, have to do necessary modification to measuring an outcome otherwise, lest had caused big error. (2) ADXL50 wants installation to be on circuit board use. Be in the resonance frequency of circuit board and when waiting for the frequency close that measures acceleration, if circuit board has a bit,become loose, can produce resonance, make measure a result to slant big, cause an error. Accordingly, when installing circuit board, want to choose proper place, secure firm. When having a test to the system, had better check below different frequency, so that discover potential resonance problem. (3) the action of C1 of capacitance of demodulator filter wave: Decide the bandwidth of ADXL50; Have filter wave to demodulator signal. 3 signal handle device 3. ADC0809 of 1ADC0809 is a kind by onefold + power supply of 5V power source, use successive to approach changeover principle, can be opposite 8 O ～ + what voltage of 5V input imitate undertakes time-sharing is changed is general-purpose but converter of D of ／ of process designing A. ADC0809 model ／ counts the working clock of converter to have broad applicable frequency range. This model ／ counts the frequency of clock of highest and effective job with applicable converter to be 3MHz about, ／ of the smallest model counts the cycle of changeover to be able to amount to 24 μ S, its sampling frequency is so highest achieve 41kHz. And missile carries drive a vehicle to be in march and frequency of the vibration in process having vertical stroke do not exceed 200Hz commonly, according to sampling theorem, completely OK and contented measure need. 3. 2 sheet piece machine and plan of its process designing plan to use MCS51 series sheet piece machine, it is OK and direct with ADC0809 model ／ several converter connect. The oscillatory signal that 3 acceleration sensor collects 3 direction (or so direction, fluctuation direction, around direction) , via 3 inputs of ADC0809 converter end is changed into digital signal, next by sheet piece machine collect. Odd an aircraft main program above all open up 3 memory division, every memory division is 10 byte unit, use what 3 inputs carry at memory to collect data respectively, next ordinal loop reads 3 inputs that take ADC0809 to carry (INO, INl, IN2) changeover result, show go up in LED indication screen, at the same time with beforehand the fixed data of set undertakes comparative: If lie inside acceptance area, continue ordinal loop reads the data that takes next input end, and store every input is carried recently 10 value; If read extraction certain to input upright data to exceed acceptance area, store this data first, continue to read next take this input to carry data N (N<9) second, read data hind to store in time every time, read N second hind the average that the 10 times that request this input to carry a memory occupy, if still exceed acceptance area, call the police quickly, make through drive circuit the horn cries namely, caution light is ablaze. Seek mean square way to data through this kind, can filter removes the random interference such as a few bizarre values. 4 epilogue carry the analysis that plays carriage process through holding drive a vehicle to missile, put forward to use sheet piece ADXL50 of sensor of compositive type acceleration and sheet piece a plan that Electromechanical road will come to to measure oscillatory acceleration. Main introduction ADXL50 is odd a compositive acceleration sensor, odd the composition of a machine test system. The methodological strain that uses flowing filter wave removes a few random interference. This plan circuit is concise, the reliable redundancy of the design is taller, better to checking a car to carry systematic acceleration to have draw lessons from action. CNC Milling