Current conversion circuit, inertial navigation device, control method and storage medium

Abstract

The present invention provides an acceleration sensor output current conversion circuit, an inertial navigation device, a control method for the acceleration sensor output current conversion circuit, and a computer storage medium. The output current conversion circuit includes a first operational amplifier, a first capacitor, an A / D conversion circuit, a controller, a constant current source, and a second operational amplifier; one end of the first switch, one end of the second switch, one end of the third switch, and one end of the second capacitor are electrically connected to each other; one end of the fourth switch, one end of the fifth switch, and the other end of the second capacitor are electrically connected to each other; the other end of the first switch is electrically connected to the first positive voltage power supply end through a constant current source; the other end of the second switch, the inverting input end, and the output end of the second operational amplifier are electrically connected to each other; the other end of the third switch and the other end of the fifth switch are both electrically connected to the inverting input end of the first operational amplifier; the other end of the fourth switch and the non-inverting input end of the second operational amplifier are both grounded; and the control ends of each switch are electrically connected to the controller respectively.

Description

Technical Field

[0001] The invention relates to an I / F (current / frequency) conversion circuit, in particular to an output current conversion circuit applied to an accelerometer measurement circuit in an inertial navigation system. Background Art

[0002] The accelerometer is the core component of the inertial navigation system. The output signal of the accelerometer is an analog current. In order to facilitate the navigation computer to collect and process the output signal of the accelerometer, an I / F conversion circuit is required. The I / F circuit is a circuit that converts analog current into a digital frequency signal. At present, the I / F conversion circuit is quite mature. Because the output current of the accelerometer is bipolar, the existing I / F conversion circuit generally uses a combination of a dual constant current source, an integration circuit, and an A / D conversion circuit, such as Figure 1 shown.

[0003] like Figure 1 As shown, the principle of the existing I / F conversion circuit is: when the accelerometer outputs a positive current (Ia is a positive current), the integration circuit starts to work, the integration capacitor is in a charging state, and when the output voltage of the integration circuit does not exceed the specified threshold voltage, both the positive and negative constant current sources are in a bypass state; when the output voltage of the integration circuit exceeds the threshold voltage, the negative constant current source is connected to the integration circuit, the integration capacitor starts to discharge, and the positive constant current source is still in a bypass state. Similarly, when the accelerometer outputs a negative current (Ia is a negative current), the integration capacitor is in a reverse charging state, and when the output voltage of the integration circuit does not exceed the threshold voltage, both the positive and negative constant current sources are in a bypass state; when the output voltage of the integration circuit exceeds the threshold voltage, the positive constant current source is connected to the integration circuit, the integration capacitor starts to discharge, and the negative constant current source is still in a bypass state.

[0004] The existing I / F conversion circuit uses a dual constant current source, so the power consumption is relatively high. In addition, since there are two constant current sources working, the temperature drift is large, which will have an adverse effect on the accuracy of the product. Summary of the invention

[0005] The problem to be solved by the present invention is to provide an acceleration sensor output current conversion circuit for the problem of high power consumption of the existing I / F conversion circuit, which is mainly used in an inertial navigation system.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: an acceleration sensor output current conversion circuit, including a first operational amplifier, a first capacitor C1, a constant current source, an A / D conversion circuit, and a controller;

[0007] One end of the first capacitor C1, the inverting input end of the first operational amplifier, and the output end of the acceleration sensor are electrically connected to each other, the other end of the first capacitor C1, the output end of the first operational amplifier, and the input end of the A / D conversion circuit are electrically connected to each other, the output end of the A / D conversion circuit is electrically connected to the input end of the controller, and the non-inverting input end of the first operational amplifier is grounded;

[0008] The number of constant current sources in the acceleration sensor output current conversion circuit is 1, the acceleration sensor output current conversion circuit further includes a second operational amplifier and a second capacitor C2, the inverting input terminal and the output terminal of the second operational amplifier are electrically connected to each other, and the acceleration sensor output current conversion circuit further includes:

[0009] a first switch unit, used for selectively connecting one of the inverting input terminal of the first operational amplifier, the inverting input terminal of the second operational amplifier, and the output terminal of the constant current source to one end of the second capacitor C2;

[0010] The second switch unit is used for selecting to ground the other end of the second capacitor C2 or to electrically connect the other end of the second capacitor C2 to the inverting input terminal of the first operational amplifier.

[0011] In the prior art, when the acceleration sensor outputs a positive current or a negative current, the directions of the charges on the first capacitor C1 are opposite, so two constant current sources are provided. In the present invention, by providing the first switch unit and the second switch unit, the connection relationship between the constant current source and the first capacitor C1 can be changed, and the charges on the first capacitor C1 can be neutralized by one constant current source when the acceleration sensor outputs a positive current or a negative current. Since only one constant current source is used, the power consumption is low, the temperature drift is small, the influence on the accuracy of the acceleration sensor is small, and space is saved.

[0012] Further, the first switch unit includes a first switch S1, a second switch S2, and a third switch S3, and the second switch unit includes a fourth switch S4 and a fifth switch S5;

[0013] One end of the first switch S1, one end of the second switch S2, one end of the third switch S3, and one end of the second capacitor C2 are electrically connected to each other;

[0014] One end of the fourth switch S4, one end of the fifth switch S5, and the other end of the second capacitor C2 are electrically connected to each other;

[0015] The other end of the first switch S1 and the other end of the second switch S2 are electrically connected to the output end of the constant current source and the inverting input end of the second operational amplifier respectively;

[0016] The other end of the third switch S3 and the other end of the fifth switch S5 are both electrically connected to the inverting input terminal of the first operational amplifier;

[0017] The other end of the fourth switch S4 is grounded;

[0018] The non-inverting input terminals of the first operational amplifier and the second operational amplifier are both grounded;

[0019] The control end of the first switch S1 , the control end of the second switch S2 , the control end of the third switch S3 , the control end of the fourth switch S4 , and the control end of the fifth switch S5 are electrically connected to the controller respectively.

[0020] Furthermore, the capacitance of the second capacitor C2 is greater than the capacitance of the first capacitor C1.

[0021] By setting the capacitance of the second capacitor C2 to be larger than that of the first capacitor C1, more charges can be stored in the second capacitor C2, thereby avoiding the problem of multiple accumulation of residual charges in the first capacitor C1 causing saturation of the first capacitor C1 due to the inability of the second capacitor C2 to completely neutralize the charges in the first capacitor C1.

[0022] Furthermore, the controller is used for:

[0023] In the initial state, a first control signal is sent to the first switch part, and a second control signal is sent to the second switch part, so that both the first switch part and the second switch part are in the disconnected state;

[0024] If it is determined that the output value of the A / D conversion circuit is less than the first negative threshold voltage, the following steps (A1)-(A2) are performed;

[0025] (A1) sending a third control signal to the first switch unit so that the first switch unit electrically connects one end of the second capacitor C2 to the output end of the constant current source, and sending a fourth control signal to the second switch unit so that the second switch unit grounds the other end of the second capacitor C2, and maintaining the states of the first switch unit and the second switch unit in this step until a first preset time length Tb is reached;

[0026] (A2) When the first preset time length Tb is reached, a fifth control signal is sent to the first switch unit, so that the first switch unit electrically connects one end of the second capacitor C2 to the inverting input terminal of the second operational amplifier, and a sixth control signal is sent to the second switch unit, so that the second switch unit electrically connects the other end of the second capacitor C2 to the inverting input terminal of the first operational amplifier.

[0027] If it is determined that the output value of the A / D conversion circuit is greater than the first positive threshold voltage, the following steps (B1)-(B2) are performed;

[0028] (B1) sending a third control signal to the first switch unit so that the first switch unit electrically connects one end of the second capacitor C2 to the output end of the constant current source, and sending a fourth control signal to the second switch unit so that the second switch unit grounds the other end of the second capacitor C2, and maintaining the states of the first switch unit and the second switch unit in this step until a first preset time length Tb is reached;

[0029] (B2) When the first preset time length Tb is reached, a seventh control signal is sent to the first switch unit, so that the first switch unit electrically connects one end of the second capacitor C2 to the inverting input terminal of the first operational amplifier, and an eighth control signal is sent to the second switch unit, so that the second switch unit grounds the other end of the second capacitor C2.

[0030] Furthermore, the controller is also used for:

[0031] The frequency value f1 of the first pulse within the first time length is calculated according to the number of first pulses that appear continuously within the first time length, the first pulse is a pulse generated when it is determined that the output value of the A / D conversion circuit is less than the first negative threshold voltage, the output current value of the accelerometer within the first time length is calculated as Ia1=f1×Ib×Tb, and the acceleration value measured by the accelerometer within the first time length is calculated according to the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia1 of the accelerometer within the first time length, wherein Ib is the output current value of the constant current source;

[0032] The frequency value f2 of the second pulse within the second time length is calculated according to the number of second pulses that appear continuously within the second time length, the second pulse is a pulse generated when it is judged that the output value of the A / D conversion circuit is greater than the first positive threshold voltage, the output current value of the accelerometer within the second time length is calculated to be Ia2=-f2×Ib×Tb, and the acceleration value measured by the accelerometer within the second time length is calculated according to the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia2 of the accelerometer within the second time length.

[0033] The present invention also provides an inertial navigation device, characterized in that it includes an acceleration sensor and an acceleration sensor output current conversion circuit as described in any one of claims 1 to 5, wherein the acceleration sensor output end is electrically connected to the acceleration sensor output current conversion circuit.

[0034] The present invention also provides a control method using the above acceleration sensor output current conversion circuit, comprising:

[0035] In the initial state, the first switch part and the second switch part are both in the disconnected state;

[0036] If it is determined that the output value of the A / D conversion circuit is less than the first negative threshold voltage, the following steps (A1)-(A2) are performed;

[0037] (A1) The first switch unit electrically connects one end of the second capacitor C2 to the output end of the constant current source, and the second switch unit grounds the other end of the second capacitor C2 until a first preset time length Tb is reached;

[0038] (A2) When the first preset time length Tb is reached, the first switch unit electrically connects one end of the second capacitor C2 to the inverting input terminal of the second operational amplifier, and the second switch unit electrically connects the other end of the second capacitor C2 to the inverting input terminal of the first operational amplifier;

[0039] If it is determined that the output value of the A / D conversion circuit is greater than the first positive threshold voltage, the following steps (B1)-(B2) are performed;

[0040] (B1) the first switch unit electrically connects one end of the second capacitor C2 to the output end of the constant current source, and the second switch unit grounds the other end of the second capacitor C2 until a first preset time length Tb is reached;

[0041] (B2) When the first preset time length Tb is reached, the first switch unit electrically connects one end of the second capacitor C2 to the inverting input terminal of the first operational amplifier, and the second switch unit grounds the other end of the second capacitor C2.

[0042] In the above technical solution, the control method further includes:

[0043] Calculating the frequency value f1 of the first pulse within the first time length according to the number of first pulses that appear continuously within the first time length, wherein the first pulse is a pulse generated when it is determined that the output value of the A / D conversion circuit (4) is less than the first negative threshold voltage, calculating the output current value of the accelerometer within the first time length as Ia1=f1×Ib×Tb, calculating the acceleration value measured by the accelerometer within the first time length according to the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia1 of the accelerometer within the first time length, and defining Ib as the output current value of the constant current source;

[0044] The frequency value f2 of the second pulse within the second time length is calculated based on the number of second pulses that appear continuously within the second time length, the second pulse being a pulse generated when it is determined that the output value of the A / D conversion circuit (4) is greater than the first positive threshold voltage, the output current value of the accelerometer within the second time length is calculated to be Ia2=-f2×Ib×Tb, and the acceleration value measured by the accelerometer within the second time length is calculated based on the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia2 of the accelerometer within the second time length.

[0045] The present invention also provides a computer storage medium, wherein the computer storage medium stores a program; the program is used to execute the control method described in claim 7 or 8.

[0046] The advantages and positive effects of the present invention are as follows: the present invention adopts a single constant current source circuit to replace a dual constant current source circuit, charges a conversion capacitor through the single constant current source circuit, and controls the charge conversion between the conversion capacitor and the integration capacitor through an analog switch, thereby realizing accurate measurement of the bipolar output current of the accelerometer, and the circuit structure is simple, power consumption is reduced, and light weight and miniaturization are realized, so the present invention can be widely used in inertial navigation systems and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0048] Figure 1 It is the I / F circuit schematic diagram in the prior art;

[0049] Figure 2 1 is a schematic diagram of a single constant current source acceleration sensor output current conversion circuit according to an embodiment of the present invention;

[0050] Figure 3 Schematic diagram of waveform of output current conversion circuit of single constant current source acceleration sensor according to an embodiment of the present invention.

[0051] In the figure, 1, a first operational amplifier, 2, a second operational amplifier, 3, an A / D conversion circuit, 4, a constant current source, 5, a controller, 10, an integration circuit, 20, a single constant current source circuit, S1, a first switch, S2, a second switch, S3, a third switch, S4, a fourth switch, S5, a fifth switch, C1, a first capacitor, and C2, a second capacitor. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0053] like Figure 2As shown, the present invention provides an acceleration sensor output current conversion circuit, including an integration circuit 10, a single constant current source circuit 20, an A / D conversion circuit 4, and a controller 5.

[0054] The integration circuit 10 is used to convert the output current of the accelerometer into a corresponding integrated voltage. The integration circuit 10 includes a first operational amplifier 1 and a first capacitor C1. N1 is an operational amplifier 1, and the first capacitor C1 is an integrating capacitor. The A / D conversion circuit 4 is used to convert the integrated voltage of the first capacitor C1 of the analog signal into a digital signal. The voltage across the first capacitor C1 is directly measured by the A / D conversion circuit 4. The A / D conversion circuit 4 is preferably a bipolar analog-to-digital conversion circuit. One end of the first capacitor C1, the inverting input end of the first operational amplifier 1, and the output end of the acceleration sensor are electrically connected to each other, the other end of the first capacitor C1, the output end of the first operational amplifier 1, and the input end of the A / D conversion circuit 4 are electrically connected to each other, the output end of the A / D conversion circuit 4 is electrically connected to the input end of the controller 5, and the in-phase input end of the first operational amplifier 1 is grounded.

[0055] The single constant current source circuit 20 includes a first switch section 100, a second switch section 200, a second capacitor C2, a constant current source 3 and a second operational amplifier 2. The second capacitor C2 is a conversion capacitor, and N2 is an operational amplifier 2. The analog switch is used to control the charging process of the constant current source 3 to the second capacitor C2 and the discharging process of the second capacitor C2 to the first capacitor C1. The constant current source 3 can be a DC constant current source.

[0056] The first switch unit 100 is in an off state, that is, one end of the second capacitor C2 is not electrically connected to other circuits. The second switch unit 200 is in an off state, that is, the other end of the second capacitor C2 is not electrically connected to other circuits.

[0057] The first switch unit 100 includes a first switch S1, a second switch S2, and a third switch S3. The second switch unit 200 includes a fourth switch S4 and a fifth switch S5. The first switch unit 100 is used to select to electrically connect one of the inverting input terminal of the first operational amplifier 1, the inverting input terminal of the second operational amplifier 2, and the output terminal of the constant current source 3 to one end of the second capacitor C2. The second switch unit 200 is used to select to ground the other end of the second capacitor C2 or to electrically connect the other end of the second capacitor C2 to the inverting input terminal of the first operational amplifier 1. The constant current source 3 is powered by a power supply. The connection between the constant current source 3 and the power supply can refer to the connection of the existing I / F conversion circuit using a dual constant current source. The output terminal of the constant current source 3 refers to the current output terminal.

[0058] The first switch S1 , the second switch S2 , the third switch S3 , the fourth switch S4 , and the fifth switch S5 may be analog switches.

[0059] One end of the first switch S1, one end of the second switch S2, one end of the third switch S3, and one end of the second capacitor C2 are electrically connected to each other;

[0060] One end of the fourth switch S4, one end of the fifth switch S5, and the other end of the second capacitor C2 are electrically connected to each other. The other end of the first switch S1 is grounded through the constant current source 3; the other end of the second switch S2, the inverting input end and the output end of the second operational amplifier 2 are electrically connected to each other; the other end of the third switch S3 and the other end of the fifth switch S5 are electrically connected to the inverting input end of the first operational amplifier 1; the non-inverting input end of the first operational amplifier 1, the non-inverting input end of the second operational amplifier 2, and the other end of the fourth switch S4 are all grounded. The control end of the first switch S1, the control end of the second switch S2, the control end of the third switch S3, the control end of the fourth switch S4, and the control end of the fifth switch S5 can be electrically connected to different I / O ports of the controller 5 respectively. The switch chip (monolithic integrated circuit) can also be used to control the opening and closing of each switch S1~S5. The opening and closing of each analog switch can also be controlled by FPGA.

[0061] In a preferred embodiment, the capacitance of the second capacitor C2 is greater than the capacitance of the first capacitor C1.

[0062] The invention provides an inertial navigation device, comprising an acceleration sensor and an acceleration sensor output current conversion circuit, wherein the acceleration sensor output end is electrically connected to the acceleration sensor output current conversion circuit.

[0063] Ia is defined as the output current of the accelerometer (i.e., the current value output by the accelerometer after converting the measured acceleration value). Ib is defined as the constant output current value of the constant current source. Tb is defined as the preset time length (i.e., the integration time of the second capacitor C2). Tb is the time length during which the first switch S1 and the fourth switch S4 are both in the closed state and the second switch S2, the third switch S3, and the fifth switch S5 are all in the open state. The first preset time length Tb can be set in the FPGA circuit. The first positive threshold voltage U+ and the first negative threshold voltage U- are defined. The first positive threshold voltage U+ and the first negative threshold voltage U- are set according to the threshold value of the I / O port of the A / D conversion circuit 4. The threshold value of the I / O port has positive and negative values, so the threshold voltage also has positive and negative values. When the positive current is input, the corresponding first negative threshold voltage U- is a negative voltage, and when the negative current is input, the corresponding first positive threshold voltage U+ is a positive voltage. Preferably, Tb<430us. The output current Ib of the constant current source 3 is greater than the absolute value of the maximum output current of the accelerometer. In this application, an accelerometer is also referred to as an acceleration sensor.

[0064] The control method of the acceleration sensor output current conversion circuit of the present invention comprises:

[0065] In the initial state, the first switch unit 100 and the second switch unit 200 are both in the off state;

[0066] If it is determined that the output value of the A / D conversion circuit 4 is less than the first negative threshold voltage, the following steps (A1)-(A2) are performed;

[0067] (A1) The first switch unit 100 electrically connects one end of the second capacitor C2 to the output end of the constant current source 3, and the second switch unit 200 grounds the other end of the second capacitor C2 until a first preset time length Tb is reached;

[0068] (A2) When the first preset time length Tb is reached, the first switch unit 100 electrically connects one end of the second capacitor C2 to the inverting input terminal of the second operational amplifier 2, and the second switch unit 200 electrically connects the other end of the second capacitor C2 to the inverting input terminal of the first operational amplifier 1;

[0069] If it is determined that the output value of the A / D conversion circuit 4 is greater than the first positive threshold voltage, the following steps (B1) to (B2) are performed;

[0070] (B1) The first switch unit 100 electrically connects one end of the second capacitor C2 to the output end of the constant current source 3, and the second switch unit 200 grounds the other end of the second capacitor C2 until a first preset time length Tb is reached;

[0071] (B2) When the first preset time length Tb is reached, the first switch unit 100 electrically connects one end of the second capacitor C2 to the inverting input terminal of the first operational amplifier 1, and the second switch unit 200 grounds the other end of the second capacitor C2.

[0072] The above control method also includes:

[0073] The frequency value f1 of the first pulse within the first time length is calculated according to the number of first pulses that appear continuously within the first time length, the first pulse is a pulse generated when it is judged that the output value of the A / D conversion circuit 4 is less than the first negative threshold voltage, the output current value of the accelerometer within the first time length is calculated as Ia1=f1×Ib×Tb, the acceleration value measured by the accelerometer within the first time length is calculated according to the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia1 of the accelerometer within the first time length, and Ib is the output current value of the constant current source;

[0074] The frequency value f2 of the second pulse within the second time length is calculated according to the number of second pulses that appear continuously within the second time length, the second pulse is a pulse generated when it is judged that the output value of the A / D conversion circuit 4 is greater than the first positive threshold voltage, and the output current value of the accelerometer within the second time length is calculated to be Ia2=-f2×Ib×Tb. The acceleration value measured by the accelerometer within the second time length is calculated according to the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia2 of the accelerometer within the second time length.

[0075] The first time length and the second time length may be preset as fixed values. The first time length and the second time length may also be equal values.

[0076] The present invention also provides a computer storage medium, wherein the computer storage medium stores a program; the program is used to execute the control method described in claim 7 or 8.

[0077] The following combination Figure 3 A control method using the acceleration sensor output current conversion circuit is described.

[0078] In the initial state, the controller 5 can make the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, and the fifth switch S5 all in the disconnected state. When the accelerometer output current is positive or negative, the integration circuit 10 integrates the first capacitor C1. The controller 5 collects the output value of the A / D conversion circuit 4.

[0079] 1) The accelerometer output current is positive current

[0080] Starting from time 0, assuming that the output current Ia is a positive current value Ia1, the integration circuit 10 starts to integrate the first capacitor C1. Since the point M11 is at ground potential, the voltage at the point M12 collected by the A / D conversion circuit 4 is a negative voltage value.

[0081] At time t1, the voltage across the first capacitor C1 is lower than the first negative threshold voltage U-, and step (A1) is executed at this time. The controller 5 generates a first pulse P1, and within the first preset time length Tb, the first switch S1 and the fourth switch S4 are closed, and the second switch S2, the third switch S3, and the fifth switch S5 are opened, that is, one end of the second capacitor C2 is electrically connected to the output end of the constant current source 3, and the other end of the second capacitor C2 is grounded. That is, the constant current source 3 charges the second capacitor C2 for a time length of Tb. The time interval from time t1 to time t2 is Tb.

[0082] At time t2, that is, when the first preset time length Tb is reached, the constant current source 3 completes charging the second capacitor C2, and step (A2) is started, the second switch S2 and the fifth switch S5 are closed, and the first switch S1, the third switch S3, and the fourth switch S4 are opened, that is, one end and the other end of the second capacitor C2 are respectively electrically connected to the inverting input end of the second operational amplifier 2 and the inverting input end of the first operational amplifier 1. From time t2, the second capacitor C2 begins to discharge the first capacitor C1, that is, the charge stored on the second capacitor C2 neutralizes the charge on the first capacitor C1. One end of the second capacitor C2 is connected to the inverting input end of the second operational amplifier N2, and the other end is connected to the inverting input end of the first operational amplifier N1 and one end of the first capacitor C1. Therefore, the charge on the second capacitor C2 can neutralize the charge on the first capacitor C1, so that the voltage value at both ends of the first capacitor C1 after integration is increased to above the first negative threshold voltage U-. Among them, the actions of opening S1, S3, S4 and closing S2 and S5 can be performed simultaneously. Among them, after reaching the first preset time length Tb, the second switch S2 and the fifth switch S5 are kept in the closed state and the first switch S1, the third switch S3, and the fourth switch S4 are kept in the open state until the threshold is exceeded again (that is, the voltage across the first capacitor C1 is lower than the first negative threshold voltage U-), and then step (A1) is repeated to repeat the above process.

[0083] At time t3, the neutralization process ends. Starting from t3, since the output current Ia still maintains the positive current value Ia1, the integration circuit 10 continues to integrate the first capacitor C1 and repeats the above process. The certain charge Q stored on the second capacitor C2 C2 =Ib×Tb. When the charge of the second capacitor C2 is used to neutralize the charge of the first capacitor C1 for the first time, the charge released is When n approaches infinity, the charge discharged for the nth time is: Therefore, from Ia×Ta=Ib×Tb, we can get: fa=1 / Ta=Ia / (Ib×Tb). Therefore, the output frequency fa is proportional to the accelerometer output current Ia.

[0084] 2) The accelerometer output current is negative

[0085] At time t4, it is assumed that the output current Ia changes from the positive current value Ia1 to the negative current value Ia2, so the integration circuit 10 continues to integrate the first capacitor C1 from time t4.

[0086] At time t5, the voltage across the first capacitor C1 is higher than the first positive threshold voltage U+, and step (B1) is executed at this time. The controller 5 generates a second pulse P2, and within the first preset time length Tb, the first switch S1 and the fourth switch S4 are closed, and the second switch S2, the third switch S3, and the fifth switch S5 are opened, that is, one end of the second capacitor C2 is electrically connected to the output end of the constant current source 3, and the other end of the second capacitor C2 is grounded. That is, the constant current source 3 charges the second capacitor C2 for a time length of Tb. The time interval from time t5 to time t6 is Tb. Closing the first switch S1 and the fourth switch S4 will not affect the charging of the first capacitor C1. If the acceleration maintains the previous output current, the first capacitor C1 will still be charged, and its integrated voltage will rise a little in a short period of time. A protection circuit can be set at the input interface of the A / D conversion circuit to prevent the voltage across the first capacitor C1 from exceeding the input interface threshold value of the A / D conversion circuit.

[0087] At time t6, that is, when the first preset time length Tb is reached, the constant current source 3 completes charging the second capacitor C2, and step (B2) is started, the third switch S3 and the fourth switch S4 are closed, and the first switch S1, the second switch S2, and the fifth switch S5 are opened, that is, one end of the second capacitor C2 is electrically connected to the inverting input end of the first operational amplifier 1, and the other end of the second capacitor C2 is grounded. From time t2, the second capacitor C2 begins to discharge the first capacitor C1, that is, the charge stored on the second capacitor C2 neutralizes the charge on the first capacitor C1. One end of the second capacitor C2 is connected to the inverting input end of the first operational amplifier N1 and one end of the first capacitor C1, and the other end is grounded, so the charge on the second capacitor C2 can neutralize the charge on the first capacitor C1, so that the voltage value at both ends of the first capacitor C1 after integration drops below the first positive threshold voltage U+. Among them, the actions of opening S1, S2, S5 and closing S3 and S4 can be performed simultaneously. Among them, after reaching the first preset time length Tb, the third switch S3 and the fourth switch S4 are kept in the closed state and the first switch S1, the second switch S2, and the fifth switch S5 are kept in the open state until the threshold is exceeded again (that is, the voltage across the first capacitor C1 is higher than the first positive threshold voltage U+), and then step (B1) is repeated to repeat the above process.

[0088] At time t7, the neutralization process ends. Starting from t7, since the output current Ia still maintains the negative current value Ia2, the integration circuit 10 continues to integrate the first capacitor C1 and repeats the above process.

[0089] Ca and Cb are defined as the capacitance of the first capacitor C1 and the second capacitor C2 respectively.

[0090] The charge stored on the first capacitor C1 is Q C1=Ia×Ta = Ca×Ua. Since the input voltage range of the A / D conversion circuit 4 has a limited value, there are upper and lower limits for the voltage value of Ua. For the acceleration sensor, the maximum value of its output current Ia can also be determined (from the product manual of the acceleration sensor). Therefore, the values of Ta and Ca can be determined accordingly.

[0091] The charge stored on the second capacitor C2 is Q C2 =Ib×Tb = Cb×Ub. Q C2 should not be less than Q C1 and according to Figure 3 the timing diagram, it can be seen that Tb < Ta. Therefore, the constant current Ib output by the constant current source 3 should be greater than the maximum absolute value of the output current Ia of the acceleration sensor. The forms of the first pulse and the second pulse and how to generate them can all be set with reference to the I / F conversion circuit of the dual constant current source in the prior art. The controller 5 can be a single-chip microcomputer, a DSP or an FPGA.

[0092] The references of this application are as follows:

[0093] Reference 1: The journal article "Accelerometer I / F Conversion Circuit in Missile-Borne Inertial Navigation System" published by Meng Junfang in the 3rd issue of "Aero Weaponry" in 1998.

[0094] It should be noted that the embodiments in this specification are all described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other.

[0095] The above has described the embodiments of the present invention in detail, but the content described is only the preferred embodiments of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope covered by this patent. After reading the present invention, various equivalent modifications made by those skilled in the art to the present invention fall within the scope defined by the appended claims of this application. Without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

Claims

1. An acceleration sensor output current conversion circuit, comprising a first operational amplifier (1), a first capacitor C1, a constant current source (3), an A / D conversion circuit (4), and a controller (5); One end of the first capacitor C1, the inverting input end of the first operational amplifier (1), and the output end of the acceleration sensor are electrically connected to each other; the other end of the first capacitor C1, the output end of the first operational amplifier (1), and the input end of the A / D conversion circuit (4) are electrically connected to each other; the output end of the A / D conversion circuit (4) is electrically connected to the input end of the controller (5); and the non-inverting input end of the first operational amplifier (1) is grounded; It is characterized in that The number of constant current sources in the acceleration sensor output current conversion circuit is 1. The acceleration sensor output current conversion circuit further comprises a second operational amplifier (2) and a second capacitor C2. The inverting input terminal and the output terminal of the second operational amplifier (2) are electrically connected to each other. The acceleration sensor output current conversion circuit further comprises: A first switch unit (100) is used to select and electrically connect one of the inverting input terminal of the first operational amplifier (1), the inverting input terminal of the second operational amplifier (2), and the output terminal of the constant current source (3) to one end of the second capacitor C2; A second switch unit (200) is used to select to ground the other end of the second capacitor C2 or to electrically connect the other end of the second capacitor C2 to the inverting input terminal of the first operational amplifier (1); The first switch unit (100) comprises a first switch S1, a second switch S2, and a third switch S3, and the second switch unit (200) comprises a fourth switch S4 and a fifth switch S5; One end of the first switch S1, one end of the second switch S2, one end of the third switch S3, and one end of the second capacitor C2 are electrically connected to each other; One end of the fourth switch S4, one end of the fifth switch S5, and the other end of the second capacitor C2 are electrically connected to each other; The other end of the first switch S1 and the other end of the second switch S2 are electrically connected to the output end of the constant current source (3) and the inverting input end of the second operational amplifier (2) respectively; The other end of the third switch S3 and the other end of the fifth switch S5 are both electrically connected to the inverting input terminal of the first operational amplifier (1); The other end of the fourth switch S4 is grounded; The common-phase input terminals of the first operational amplifier (1) and the second operational amplifier (2) are both grounded; The control end of the first switch S1, the control end of the second switch S2, the control end of the third switch S3, the control end of the fourth switch S4, and the control end of the fifth switch S5 are electrically connected to the controller (5) respectively; The controller (5) is used to: In the initial state, a first control signal is sent to the first switch unit (100), and a second control signal is sent to the second switch unit (200), so that the first switch unit (100) and the second switch unit (200) are both in the disconnected state; If it is determined that the output value of the A / D conversion circuit (4) is less than the first negative threshold voltage, the following steps (A1) to (A2) are performed; (A1) sending a third control signal to the first switch unit (100) so that the first switch unit (100) electrically connects one end of the second capacitor C2 to the output end of the constant current source (3), and sending a fourth control signal to the second switch unit (200) so that the second switch unit (200) grounds the other end of the second capacitor C2, and maintaining the states of the first switch unit (100) and the second switch unit (200) in this step until a first preset time length Tb is reached; (A2) When the first preset time length Tb is reached, a fifth control signal is sent to the first switch unit (100), so that the first switch unit (100) electrically connects one end of the second capacitor C2 to the inverting input end of the second operational amplifier (2), and a sixth control signal is sent to the second switch unit (200), so that the second switch unit (200) electrically connects the other end of the second capacitor C2 to the inverting input end of the first operational amplifier (1); If it is determined that the output value of the A / D conversion circuit (4) is greater than the first positive threshold voltage, the following steps (B1) to (B2) are performed; (B1) sending a third control signal to the first switch unit (100) so that the first switch unit (100) electrically connects one end of the second capacitor C2 to the output end of the constant current source (3), and sending a fourth control signal to the second switch unit (200) so that the second switch unit (200) grounds the other end of the second capacitor C2, and maintaining the states of the first switch unit (100) and the second switch unit (200) in this step until a first preset time length Tb is reached; When (B2) reaches the first preset time length Tb, a seventh control signal is sent to the first switch unit (100), so that the first switch unit (100) electrically connects one end of the second capacitor C2 to the inverting input end of the first operational amplifier (1), and an eighth control signal is sent to the second switch unit (200), so that the second switch unit (200) grounds the other end of the second capacitor C2.

2. The acceleration sensor output current conversion circuit according to claim 1, characterized in that: The capacitance of the second capacitor C2 is greater than the capacitance of the first capacitor C1.

3. The acceleration sensor output current conversion circuit according to claim 1, characterized in that: The controller (5) is also used for: Calculating the frequency value f1 of the first pulse within the first time length according to the number of first pulses that appear continuously within the first time length, wherein the first pulse is a pulse generated when it is determined that the output value of the A / D conversion circuit (4) is less than the first negative threshold voltage, calculating the output current value of the accelerometer within the first time length as Ia1=f1×Ib×Tb, and calculating the acceleration value measured by the accelerometer within the first time length according to the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia1 of the accelerometer within the first time length, wherein Ib is the output current value of the constant current source; The frequency value f2 of the second pulse within the second time length is calculated based on the number of second pulses that appear continuously within the second time length, the second pulse being a pulse generated when it is determined that the output value of the A / D conversion circuit (4) is greater than the first positive threshold voltage, the output current value of the accelerometer within the second time length is calculated to be Ia2=-f2×Ib×Tb, and the acceleration value measured by the accelerometer within the second time length is calculated based on the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia2 of the accelerometer within the second time length.

4. An inertial navigation device, characterized in that: The invention comprises an acceleration sensor and an acceleration sensor output current conversion circuit according to any one of claims 1 to 3, wherein the output end of the acceleration sensor is electrically connected to the acceleration sensor output current conversion circuit.

5. A control method using the acceleration sensor output current conversion circuit according to any one of claims 1 to 3, characterized in that: include: In the initial state, the first switch unit (100) and the second switch unit (200) are both in the disconnected state; If it is determined that the output value of the A / D conversion circuit (4) is less than the first negative threshold voltage, the following steps (A1) to (A2) are performed; (A1) the first switch unit (100) electrically connects one end of the second capacitor C2 to the output end of the constant current source (3), and the second switch unit (200) grounds the other end of the second capacitor C2 until a first preset time length Tb is reached; (A2) When the first preset time length Tb is reached, the first switch unit (100) electrically connects one end of the second capacitor C2 to the inverting input terminal of the second operational amplifier (2), and the second switch unit (200) electrically connects the other end of the second capacitor C2 to the inverting input terminal of the first operational amplifier (1); If it is determined that the output value of the A / D conversion circuit (4) is greater than the first positive threshold voltage, the following steps (B1) to (B2) are performed; (B1) the first switch unit (100) electrically connects one end of the second capacitor C2 to the output end of the constant current source (3), and the second switch unit (200) grounds the other end of the second capacitor C2 until a first preset time length Tb is reached; (B2) When the first preset time length Tb is reached, the first switch unit (100) electrically connects one end of the second capacitor C2 to the inverting input end of the first operational amplifier (1), and the second switch unit (200) grounds the other end of the second capacitor C2.

6. The control method according to claim 5, characterized in that: Also includes: Calculating the frequency value f1 of the first pulse within the first time length according to the number of first pulses that appear continuously within the first time length, wherein the first pulse is a pulse generated when it is determined that the output value of the A / D conversion circuit (4) is less than the first negative threshold voltage, calculating the output current value of the accelerometer within the first time length as Ia1=f1×Ib×Tb, and calculating the acceleration value measured by the accelerometer within the first time length according to the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia1 of the accelerometer within the first time length, wherein Ib is the output current value of the constant current source; The frequency value f2 of the second pulse within the second time length is calculated based on the number of second pulses that appear continuously within the second time length, the second pulse being a pulse generated when it is determined that the output value of the A / D conversion circuit (4) is greater than the first positive threshold voltage, the output current value of the accelerometer within the second time length is calculated to be Ia2=-f2×Ib×Tb, and the acceleration value measured by the accelerometer within the second time length is calculated based on the relationship between the input acceleration and the output current value of the accelerometer and the output current value Ia2 of the accelerometer within the second time length.

7. A computer storage medium, characterized in that: The computer storage medium stores a program; the program is used to execute the control method described in claim 5 or 6.

Images