Accelerometer current conversion circuit and control method thereof

Abstract

The invention relates to the technical field of electrical engineering application, and discloses an accelerometer current conversion circuit and a control method thereof so as to consider both precision and cost. The circuit comprises a device for converting a current value output by an accelerometer into a voltage value through integration, and the device is used for transmitting analog voltage to an AD conversion chip; the AD conversion chip converts the input analog voltage into digital voltage and transmits the digital voltage to the control chip; the control chip is used for realizing start and stop control of discharging in a mode of controlling on and off of a switch between the current output end of the accelerometer and the accelerometer power supply circuit; dividing a single sampling period of continuous charging into discharging time and sampling time except the discharging time, stopping discharging when the absolute value of the voltage is reduced to be smaller than a discharging stopping threshold value, and entering the sampling time; when the absolute value of the voltage rises to be greater than the discharge threshold value, the discharge time is started; and amplifying according to the ratio of the sampling time to the sampling period to obtain the estimated pulse increment of the whole sampling period.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical engineering applications, and in particular to an accelerometer current conversion circuit and a control method thereof. Background Art

[0002] With the development of aerospace technology, inertial measurement units have been widely used in various fields, so various requirements have been put forward for the performance of inertial measurement units, such as high precision, low cost, and miniaturization. However, high precision and low cost are contradictory and difficult to take into account at the same time. Therefore, in some application fields, the indicators of measurement accuracy can be relaxed, and the requirements for cost are increased. This is especially true for the acceleration current conversion circuit, an important sensor circuit in the inertial measurement unit.

[0003] There are two forms of traditional accelerometer conversion circuits:

[0004] The first form is an I / F conversion circuit, which converts the accumulated current output by the accelerometer into a voltage increment, i.e., a pulse increment of the accelerometer, through the integral effect of the capacitor on the current. At the same time, positive and negative constant current sources are used to charge and discharge the capacitor to avoid voltage saturation (exceeding the maximum voltage that can be measured).

[0005] In order to obtain the current integral value of the entire cycle (a requirement for navigation), the IF conversion circuit needs to sample the voltage value of the capacitor at both ends of the sampling cycle, and calculate the voltage change value generated by the constant current source based on the charging / discharging time and current size of the constant current source. The two are added to obtain the current integral value of the entire cycle. The specific calculation formula is as follows:

[0006]

[0007] in, is the estimated pulse increment of the entire sampling period, Δ U is the change value of the capacitor voltage during the sampling period, T c is the constant current source charge / discharge time, i is the constant current source charge / discharge current, and C is the capacitance value.

[0008] In summary, the IF conversion circuit has no principle error, but requires a high-precision constant current source circuit, which has complex hardware design, reduced reliability, and high cost.

[0009] The second form is a sampling resistor circuit, which converts the output current into a voltage value by passing the current through a high-precision, low-temperature-coefficient sampling resistor.

[0010] In the calculation method of pulse increment, the sampling resistor circuit can only obtain the voltage value at one sampling moment, and thus obtain the current value at one sampling moment. By approximating it to the average current of the entire cycle, the approximate current integral value of the entire cycle can be obtained. The specific calculation formula is as follows:

[0011]

[0012] in, is the estimated pulse increment of the entire sampling period, U is the voltage value across the resistor at a certain moment in the sampling period, and T s is the sampling period, and R is the sampling resistance value.

[0013] Therefore, the sampling resistor circuit has principle errors and is usually very accurate; however, the circuit is the simplest and the calculation is the simplest. Summary of the invention

[0014] The present invention aims to disclose an accelerometer current conversion circuit and a control method thereof, so as to balance accuracy and cost.

[0015] To achieve the above object, the accelerometer current conversion circuit disclosed in the present invention includes:

[0016] A device for converting the current value output by the accelerometer into a voltage value by integration, and for transmitting an analog voltage to an AD conversion chip;

[0017] AD conversion chip, used to convert the input analog voltage into digital voltage for transmission to the control chip;

[0018] The control chip is used to realize the start and stop control of discharge by controlling the switch between the current output terminal of the accelerometer and the power supply circuit of the accelerometer; and divide the single sampling period of continuous charging into the discharge time and the sampling time outside the discharge time. When the absolute value of the voltage drops to less than the stop discharge threshold, the discharge is stopped and the sampling time is entered; when the absolute value of the voltage rises to greater than the discharge threshold, the discharge time is entered; then, the sampling time is amplified according to the ratio of the sampling time to the sampling period to obtain the estimated pulse increment of the entire sampling period. The specific calculation formula is:

[0019]

[0020] in, is the estimated pulse increment of the entire sampling period; Δ Tc T is the pulse increment obtained by subtracting the voltage at the start and end of the sampling time. s is the sampling period, T c is the sampling time.

[0021] Preferably, the voltage value of the positive and negative terminals of the power supply circuit of the accelerometer is 15V, and the control chip is used to select to open the +15V voltage switch or the -15V voltage switch for discharge according to the voltage sampling result.

[0022] To achieve the above object, the present invention further discloses a control method of an accelerometer current conversion circuit, which is applied to the above accelerometer current conversion circuit, and comprises:

[0023] Step S1, dividing a single sampling period of continuous charging into a discharge time and a sampling time outside the discharge time, when the absolute value of the voltage drops to less than a stop-discharge threshold, the discharge is stopped and the sampling time is entered, and when the absolute value of the voltage rises to greater than the discharge threshold, the discharge time is entered, and the controller realizes the start and stop control of the discharge by controlling the on and off of the switch between the current output terminal of the accelerometer and the power supply circuit of the accelerometer;

[0024] Step S2: amplify the ratio of the sampling time to the sampling period to obtain the estimated pulse increment of the entire sampling period. The specific calculation formula is:

[0025]

[0026] in, is the estimated pulse increment of the entire sampling period; Δ Tc T is the pulse increment obtained by subtracting the voltage at the start and end of the sampling time. s is the sampling period, T c The sampling time

[0027] The present invention has the following beneficial effects:

[0028] It does not require a high-precision constant current source circuit, has low requirements for switches, has fewer circuit components, and has low cost. Compared with the resistor sampling circuit, the present invention is based on a current integration circuit and uniform extrapolation to calculate the pulse increment. For use in navigation algorithms, the principle error is small and has better accuracy.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0031] Figure 1 It is a schematic diagram of a current conversion circuit disclosed in an embodiment of the present invention.

[0032] Figure 2 The diagram is a schematic diagram of the distribution of sampling time and discharge time in a sampling period disclosed in an embodiment of the present invention.

[0033] Figure 3 It is a flow chart of a control method of a current conversion circuit disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0035] Example 1

[0036] This embodiment discloses an accelerometer current conversion circuit, referring to Figures 1 to 3 ,include:

[0037] A device that converts the current value output by the accelerometer into a voltage value by integration, and is used to transmit analog voltage to the AD conversion chip.

[0038] The AD conversion chip is used to convert the input analog voltage into a digital voltage for transmission to the control chip.

[0039] The control chip is used to realize the start and stop control of discharge by controlling the switch between the current output terminal of the accelerometer and the power supply circuit of the accelerometer; and divide the single sampling period of continuous charging into the discharge time and the sampling time outside the discharge time. When the absolute value of the voltage drops to less than the stop discharge threshold, the discharge is stopped and the sampling time is entered; when the absolute value of the voltage rises to greater than the discharge threshold, the discharge time is entered; then, the sampling time is amplified according to the ratio of the sampling time to the sampling period to obtain the estimated pulse increment of the entire sampling period. The specific calculation formula is:

[0040]

[0041] in, is the estimated pulse increment of the entire sampling period; Δ Tc T is the pulse increment obtained by subtracting the voltage at the start and end of the sampling time. s is the sampling period, T c is the sampling time.

[0042] exist Figure 1 In the embodiment, the voltage value of the positive and negative terminals of the power supply circuit of the accelerometer is 15V, and the control chip is used to select to open the +15V voltage switch or the -15V voltage switch for discharge according to the voltage sampling result.

[0043] Example 2

[0044] Corresponding to the above embodiment, this embodiment discloses a control method of an accelerometer current conversion circuit, including:

[0045] Step S1, dividing a single sampling period of continuous charging into a discharge time and a sampling time outside the discharge time. When the absolute value of the voltage drops to less than the discharge stop threshold, the discharge is stopped and the sampling time is entered. When the absolute value of the voltage rises to greater than the discharge threshold, the discharge time is entered, and the controller realizes the start and stop control of the discharge by controlling the on and off of the switch between the current output end of the accelerometer and the accelerometer power supply circuit.

[0046] Step S2: amplify the ratio of the sampling time to the sampling period to obtain the estimated pulse increment of the entire sampling period. The specific calculation formula is:

[0047]

[0048] in, is the estimated pulse increment of the entire sampling period; Δ Tc T is the pulse increment obtained by subtracting the voltage at the start and end of the sampling time. s is the sampling period, T c The sampling time

[0049] Preferably, the voltage value of the positive and negative terminals of the power supply circuit of the accelerometer is 15V, and the control chip is used to select to open the +15V voltage switch or the -15V voltage switch for discharge according to the voltage sampling result.

[0050] In summary, the accelerometer current conversion circuit and control method thereof disclosed in the embodiments of the present invention have at least the following advantages:

[0051] It does not require a high-precision constant current source circuit, has low requirements for switches, has fewer circuit components, and has low cost. Compared with the resistor sampling circuit, the present invention is based on a current integration circuit and uniform extrapolation to calculate the pulse increment. For use in navigation algorithms, the principle error is small and has better accuracy.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An accelerometer current conversion circuit, characterized in that: include: A device for converting the current value output by the accelerometer into a voltage value by integration, and for transmitting an analog voltage to an AD conversion chip; AD conversion chip, used to convert the input analog voltage into digital voltage for transmission to the control chip; The control chip is used to realize the start and stop control of discharge by controlling the switch between the current output terminal of the accelerometer and the power supply circuit of the accelerometer; and divide the single sampling period of continuous charging into the discharge time and the sampling time outside the discharge time. When the absolute value of the voltage drops to less than the stop discharge threshold, the discharge is stopped and the sampling time is entered; when the absolute value of the voltage rises to greater than the discharge threshold, the discharge time is entered; then, the sampling time is amplified according to the ratio of the sampling time to the sampling period to obtain the estimated pulse increment of the entire sampling period. The specific calculation formula is: in, is the estimated pulse increment of the entire sampling period; Δ Tc T is the pulse increment obtained by subtracting the voltage at the start and end of the sampling time. s is the sampling period, T c is the sampling time.

2. The accelerometer current conversion circuit according to claim 1, characterized in that: The voltage value of the positive and negative terminals of the power supply circuit of the accelerometer is 15V, and the control chip is used to select to open the +15V voltage switch or the -15V voltage switch for discharge according to the voltage sampling result.

3. A control method for an accelerometer current conversion circuit, applied to the accelerometer current conversion circuit as claimed in claim 1 or 2, characterized in that: include: Step S1, dividing a single sampling period of continuous charging into a discharge time and a sampling time outside the discharge time, when the absolute value of the voltage drops to less than a stop-discharge threshold, the discharge is stopped and the sampling time is entered, and when the absolute value of the voltage rises to greater than the discharge threshold, the discharge time is entered, and the controller realizes the start and stop control of the discharge by controlling the on and off of the switch between the current output terminal of the accelerometer and the power supply circuit of the accelerometer; Step S2: amplify the ratio of the sampling time to the sampling period to obtain the estimated pulse increment of the entire sampling period. The specific calculation formula is: in, is the estimated pulse increment of the entire sampling period; Δ Tc T is the pulse increment obtained by subtracting the voltage at the start and end of the sampling time. s is the sampling period, T c is the sampling time.

4. The control method of the accelerometer current conversion circuit according to claim 3, characterized in that: The voltage value of the positive and negative terminals of the power supply circuit of the accelerometer is 15V, and the control chip is used to select to open the +15V voltage switch or the -15V voltage switch for discharge according to the voltage sampling result.

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