RU2018132C1 - Accelerometer - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: accelerometer has housing 1, sensitive element 2, surface acoustic wave delay lines 3,4 and 5,6 self-oscillators, pulse shapers. The accelerometer is characterized by the use of auxiliary electronic temperature regulator, resistive heaters, counters-registers, control generator. The temperature regulator is composed of a register, serially connected code adder, code subtracting unit, reversible counter, electronic switch, a register input being connected to the second input of code subtracting unit and sign and code outputs of the code subtracting unit being connected respectively to enabling and information inputs of the reversible counter. EFFECT: enhanced accuracy. 6 dwg

Description

 The invention relates to measuring equipment, namely to accelerometers on surface acoustic waves (SAWs) for measuring the accelerations of moving objects.

 Known accelerometer with transducers of surface acoustic waves, containing a base, a sensitive element (SE) made on each main surface of the SE delay line (LZ) with input and output interdigital converters (IDT), SAW oscillators on the delay lines formed by the inclusion of the amplifier between input and output IDT, frequency mixer, frequency meter [1].

 In such an accelerometer, the temperature conditions for the delay lines are not identical on different surfaces of the SE, which causes the temperature error of the accelerometer.

 Greater accuracy is achieved in the accelerometer adopted as a prototype, which contains a base, a sensing element, at least two delay lines, SAW oscillators on the delay lines, pulse shapers connected to SAW oscillators [2].

 However, this accelerometer also does not provide temperature stabilization, which reduces the accuracy and reliability of the accelerometer.

 The aim of the invention is to increase the reliability and accuracy of accelerometer measurements.

 This goal is achieved by the fact that in the accelerometer, made on the basis of SAW converters and containing a base, CE of at least two delay lines with input and output IDTs, including amplifiers between which SAW oscillators are formed, connected to the corresponding pulse shapers, an electronic temperature regulator, resistive heaters connected to an electronic temperature controller, and the temperature controller is made from a register, a series adder of codes, a unit for subtracting codes, connected in series, reversible the counter, an electronic key, and the output of the register is connected to the second input of the code subtracting unit, the sign and code outputs of the code subtracting unit are connected respectively to the enabling and information inputs of the reverse counter, counters-registers are introduced into the accelerometer, each of which is connected between the outputs of the corresponding pulse shaper and one of the two inputs of the code adder, as well as a control generator connected by its outputs to the second and third inputs of the counter-registers, with enabling inputs of the sums torus codes and codes the subtraction unit, to the reset input and counting input of the reversible counter.

 The inclusion of counters-registers after the pulse shapers allows you to convert the signals of SAW-oscillators into a code and use digital accelerator signal processing devices in the electronic temperature controller: code adder, code subtraction unit, register and reversible counter. The register serves as the set point for the temperature control temperature, in which the code for the total frequency of the SAW oscillators is stored. The reversible counter together with the electronic key serves to control the heating power depending on the size and sign of the mismatch of the thermostating temperature from the set value.

 Setting the temperature setting in the register using the code of the total frequency of SAW self-oscillators increases the accuracy of thermostating, since it remains unchanged in contrast to the frequency of the clock generator.

 The dependence of the heating power on the magnitude and sign of the mismatch allows you to increase the accuracy of thermal control, as it increases the accuracy of temperature maintenance due to the elimination of under-regulation and over-regulation. The ability to control the heating power depending on the mismatch sign increases the reliability of the accelerometer due to eliminating the failure of the accelerometer elements due to overheating.

 Improving the accuracy of thermal control increases the accuracy of accelerometer measurements by 2 ... 5 or more times.

 Figure 1 shows the design of the first version of the accelerometer; figure 2 is a sensitive element; figure 3 is a structural diagram of an accelerometer; in FIG. 4 and 5 - types of execution of the SE of the second embodiment of the accelerometer; figure 6 is its structural diagram.

 The accelerometer has a base 1 and SE 2, fixed in the base 1 and made of piezoelectric material. The first delay line with the input IDT 3 and the output IDT 4 is formed on the upper main surface of the CE 2. The second delay line with the input IDT 5 and the output IDT 6 is formed on the lower main surface of the CE 2. The accelerometer is closed by a cover 7.

 On the upper and lower main surfaces of the CE 2 are resistive heaters 8.

 In the structural diagram of the accelerometer in accordance with the structure of FIG. 1 by turning on the amplifier 9 between the input IDT 3 and the output IDT 4 of the first delay line, the first SAW oscillator is formed. By turning on the amplifier 9 ′ between the input IDT 5 and the output IDT 6 of the second delay line, a second SAW oscillator is formed.

 A circuit from series-connected pulse shaper 10 and a counter-register 11 is connected to the output of amplifier 9 of the first SAW oscillator. A circuit from series-connected pulse shaper 10 ′ and counter-register 11 ′ is connected to the output of amplifier 9 ′ of the second SAW oscillator.

The first outputs of the counter-registers 11, 11 ′ are connected to two inputs of the adder 12 of the codes of the electronic temperature controller, which also contains a register 13 and series-connected block 14 of the subtraction of codes, a reversible counter 15, an electronic key 16, the output of which is connected to resistive heaters 8. The output of the first register 13 is connected to the second input of block 14. The sign output of block 14 is connected to the enable input of the reverse counter 15, the code block 14 is connected to the information input of the reverse counter 15. The electronic key 16 is fed heating supply voltage U _about . To obtain an acceleration code, the second outputs of the counter-registers 11, 11 ′ are connected to two inputs of the second code subtracting unit 17, the output of which is the output signal of the accelerometer.

 The output a of the control generator 18 is connected with the second inputs of the counter-registers 11, 11 ′, the output b is connected with the third inputs of the counter-registers 11, 11 ′ and with the enabling inputs of the adder 12 codes, the second block 17 of subtracting codes, the output of c is with the enabling input block 14 subtracting codes, the output g - with the input of zeroing the reverse counter 15, the output d - with the counting input of the reverse counter 15.

 In the embodiment, the CE 2 (Fig. 4) of the piezoelectric material at the same time with the fixed part 19 of the input IDT 3 and the output IDT 4 of the first delay line is made on one side of the fixed part 19. On the same surface of the CE 2 the input IDT 20 and the output IDT 21 are made the first LZ on the CE 2. Resistive heaters 8 are formed on the CE 2 and the fixed part 19.

 A second delay line with an input IDT 5 and an output ball screw 6 is made on the second surface of the fixed part 19, and an input IDT 22 and an output IDT 23 of the second delay line on the SE 2 are formed on the same surface of the FE 2 (Fig. 5).

 In the structural diagram (Fig.6) of the second version of the accelerometer, by turning on the amplifier 9 ″ between the IDT 20 and IDT 21, a third SAW oscillator is formed on the SE 2, turning on the amplifier 9 ″ ′ between the IDT 22 and IDT 23 the fourth SAW oscillator is formed. To the output of the third SAW self-oscillator, a pulse shaper 10 ″ and a counter-register 11 ″ are connected in series. The output of the fourth SAW oscillator is connected in series with a pulse shaper 10 ″ ″ and a counter-register 11 ″ ″. The outputs of the counter-registers 11 ″, 11 ″ ″ are connected to two inputs of the adder 17 codes, the output of which is the output of the accelerometer.

 The scheme of the temperature controller in Fig.6 is made similar to the scheme of the temperature regulator in Fig.3.

 The pulse shapers can be made in the form of Schmitt triggers, the code adder and code subtraction blocks in the form of digital adders. When summing, the inputs of the adder are fed signals in direct code. When subtracting, one of the inputs of the adder receives a signal in the reverse code.

 The accelerometer works as follows.

 In the absence of acceleration, the inertial force does not act on the CE 2, therefore there is no deformation of the sound duct of the delay lines on both sides of the CE 2. The frequency of the first SAW oscillator with amplifier 9 and the delay line with IDT 3 and 4 is equal to the nominal frequency and the frequency of the second SAW auto generator with an amplifier 9 ′ and a delay line with IDTs 5 and 6. From the sinusoidal output signal of the SAW oscillators in pulse shapers 10, 10 ′, pulse signals are generated with a pulse repetition rate equal to the frequency of the SAW oscillators. In the counter-registers 11, 11 ′ from the pulse signals of the pulse shapers 10, 10 ′, digital codes of the frequencies of the SAW oscillators are generated. The second block 17 of the subtraction of codes subtracts from the code generated in the counter-register 11, the code received in the counter-register 11 ′. Since the frequencies of SAW-oscillators are equal, their codes are equal. Therefore, in the absence of acceleration, the difference in codes at the output of the code subtracting block 17 is zero, which corresponds to the accelerometer signal indicating the absence of acceleration.

 In the presence of acceleration, the SE 2 deformation occurs, the first of the delay lines increases its length, and tensile strain occurs in it, the second delay line decreases its length, and compression strain occurs in it. The frequency of the first SAW oscillator increases, the second decreases. At the output of the code subtraction unit 17, a code difference is obtained equal to the sum of the codes for changing the frequencies of both SAW oscillators.

 Since the frequencies of SAW self-oscillators are equal in the absence of acceleration and their change in the presence of acceleration occurs by equal values, then at the same and constant temperature of the delay lines on SE 2 equal to the temperature of temperature control, the sum of the frequencies of SAW self-oscillators is constant and equal to twice the nominal frequency of one SAW auto generator. Therefore, in the adder of 12 codes, the sum of the frequency codes of both SAW oscillators is formed, which is equal to twice the nominal frequency code of one SAW oscillator.

 In order to measure the deviation of the temperature of the delay lines from the thermostatic one, a code equal to twice the code of the rated frequency of one SAW oscillator is recorded in the first register 13.

 If the temperature of the delay lines on the SE 2 is lower than the temperature of the thermostating, then, for example, with a negative temperature coefficient of the frequency of the SAW oscillator, the frequency of both SAW oscillators increases, their sum becomes more than twice the rated frequency of one SAW oscillator, and the sum of the frequency codes at the output of the adder 12 codes will be more than the code recorded in the register 13. Then, as a result of subtracting from the adder code 12 codes of the code of register 13 in block 14 of subtracting codes, the separation will be received at the code output of block 14 s code adder 12 and the register 13, at a landmark 14 will block the exit code is received character code adder 13, the register 12 with respect to the code.

 In the case when the temperature of the delay lines at the CE 2 is less than the temperature of the temperature control, the sign code received from the sign output of the block 14 of the subtraction of codes to the enable input of the reverse counter 15 opens it, and the code is written to the information input of the reverse counter 15 from the output of block 14 subtracting codes. If there is a digital code at the information inputs of the reversible counter 15 from the output of the code subtracting unit 14, counting pulses are sent to the counting input via line d from the control generator, by which the reversible counter 15 is reset. The number of counting pulses is determined by a digital code recorded on the information inputs. The time during which the reverse counter 15 is reset, therefore, the pulse duration at the input of the electronic key 16 is determined by the number of zeroing pulses and the period of their repetition.

 Thus, in the reverse counter 15, the code from the output of the code subtracting unit 14 is converted to the duration of the pulse supplied to the input of the electronic key 16. The larger the difference in the codes received from the output of the code subtracting unit 14 is, the longer the pulse is supplied from the output of the reversible counter 15 to the input of the electronic key 16 and opening it. The longer the opening time of the electronic key 16, the longer the heating voltage is supplied from the electronic key 16 to the resistive heaters 8, the greater the heating power dissipated by the resistive heaters 8.

 As a result of heating, the temperature of the delay lines at SE 2 becomes equal to the temperature of the thermostating, the frequencies of the SAW oscillators decrease, and their sum becomes equal to twice the nominal frequency of one SAW oscillator, the sum of the codes at the output of the adder 12 codes becomes equal to the code recorded in register 13. Then the difference of the codes at the output of the code subtraction unit 14 is zero, the electronic key 16 does not open, and the heating of the delay lines stops.

 When the temperature of the delay lines increases with respect to the temperature of the thermostat, the sign code of the block 14 of the code subtraction closes the information inputs of the reverse counter 15, the countdown of the reverse counter is locked, the input of the electronic key 16 does not receive a pulse to open it, and the resistive heaters 8 do not receive power to heat the delay lines .

 Thus, depending on the sign and magnitude of the mismatch in the temperature of the delay lines on the SE 2 from the thermostatically controlled, the heating power is regulated and the temperature of the delay lines is kept constant.

 In the second embodiment of the accelerometer, the first delay line with IDTs 3 and 4 and the second delay line with IDTs 5 and 6 on the fixed base 19 are used to control the temperature. The operation of the temperature controller with these delay lines on the fixed base 19 in accordance with the structural diagram of FIG. 6 is similar the operation of the temperature controller according to the structural diagram of figure 3.

 To measure acceleration in the second embodiment of the accelerometer, delay lines are used on the SE 2 with IDT 20-23. The signal from the first SAW oscillator with an amplifier 9 ″ and a delay line for IDTs 20 and 21 is converted into a pulse using a pulse shaper 10 ″, then a frequency code is generated in the counter register 11 ″, from where the signal goes to the first input of the second block 17 subtraction codes. The signal from the second SAW oscillator with an amplifier 9 ″ ″ and a delay line on IDT 22 and 23 is converted into a pulse line in a pulse shaper 10 ″ ″, a frequency code is generated in the counter-register 11 ″ ″, which arrives at the second input of the subtraction block 17 codes. After subtracting the codes in block 17 subtracting codes at its output, a signal is obtained about the measured acceleration.

 The outputs of the control generator 18 receive control signals of the accelerometer blocks. Line a receives a signal for resetting the counter-registers 11, 11 ′ ... 11 ″ ″, line b - reads the signals from the counter-registers 11, 11 ′. . . 11 ′ ′ ′ and resetting the adder 12 codes, block 17 subtracting codes. The line zero is used to transmit the zeroing signal of the first block 14 of subtracting codes, the line d is the signal for resetting the reversible counter 15, and the line d is for counting pulses to the reverse counter 15.

Claims (1)

 ACCELEROMETER, made on the basis of transducers of surface acoustic waves, containing a base, a sensing element, at least two delay lines with input and output interdigital transducers, including amplifiers between which are formed oscillators connected to the corresponding pulse shapers, characterized in that introduced resistive heaters and an electronic temperature controller connected to them, made from a register, series-connected code adders, a subtraction unit code, reversible counter, electronic key, and the register output is connected to the second input of the code subtraction unit, the sign and code outputs of the code subtraction unit are connected respectively to the enabling and information inputs of the reverse counter, counters-registers are entered into the accelerometer, each of which is connected between the output the corresponding pulse shaper and one of the two inputs of the code adder, as well as a control generator connected by its outputs to the second and third inputs of the counter-registers, with a bit Collapsing adder inputs codes and codes the subtraction unit, to the reset input and counting input of the reversible counter.

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