Temperature drift compensation method and starting characteristic compensation method of current frequency conversion circuit

Abstract

The invention provides a temperature excursion compensation method and a starting characteristic compensation method of a current frequency conversion circuit. The temperature excursion compensation method comprises the following steps: determining a full temperature interval of working of the current frequency conversion circuit; dividing the full-temperature interval into a plurality of sub-temperature intervals according to a set step length; in each sub-temperature interval, performing low-order polynomial fitting on the acquisition temperature and the frequency count value of the current frequency conversion circuit, establishing a temperature factor temperature drift compensation model, and obtaining a polynomial temperature compensation parameter of each sub-temperature interval; the current temperature of the current frequency conversion circuit is collected, the sub-temperature interval where the current temperature is located is determined, and a corresponding fitting scale factor is obtained; and calculating the compensated scale factor. According to the invention, through temperature interval division and low-order nonlinear fitting, compensation in a scale factor full-temperature range is realized, and the problem that an existing compensation algorithm is restricted by FPGA resources and time sequences is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of current-frequency conversion, and in particular relates to a current-frequency conversion circuit supporting software compensation for nonlinear temperature drift and startup characteristic compensation in the field of inertial navigation. Background Art

[0002] The current-frequency conversion circuit has been more and more widely used in the field of inertial navigation. Its main function is to convert the current signal into a corresponding frequency signal to achieve pulse output. The temperature drift compensation method of the traditional conversion circuit itself is hardware compensation or software compensation. The hardware compensation method is to change the output current of the constant current source by welding a temperature-compensated current source and debugging a resistor, thereby adjusting the change in the scale factor. However, hardware compensation can only establish a linear compensation model based on the tested temperature point, and the requirements for the resistor itself are relatively high, and nonlinear compensation cannot be performed. The software compensation method is to establish a temperature compensation model by collecting temperature sensor information. At present, the full-temperature polynomial fitting formula is mostly used for curve fitting. The compensation effect of this method depends on the order of the multi-term fitting formula. The higher the order, the better the compensation effect. However, the higher the order, the greater the amount of calculation and complexity, the greater the FPGA resource occupation, and the calculation time will also be greatly increased. Under the condition of high timing requirements and limited FPGA resources, the compensation order will be restricted, and it is difficult to achieve the purpose of improving accuracy.

[0003] In addition, the temperature drift compensation operation of the conversion circuit can ensure the stability of the circuit output at all temperatures. However, the output value used for temperature compensation is the stable value 20 to 30 minutes after the circuit is powered on. In addition to the instability caused by temperature drift, the output change caused by the circuit's own startup characteristics at the beginning of power-on is more drastic, and it will not stabilize until 20 to 30 minutes later. The original temperature compensation method does not take the circuit startup characteristics into consideration and cannot compensate for the circuit startup output error. Summary of the invention

[0004] In view of the technical problems existing in the existing temperature drift compensation method of the current-frequency conversion circuit, the present invention provides a temperature drift compensation method for the current-frequency conversion circuit. By dividing the temperature interval and low-order nonlinear fitting, compensation of the scale factor within the full temperature range is achieved, thereby solving the problem that the existing compensation algorithm is restricted by FPGA resources and timing.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0006] The present invention provides a temperature drift compensation method for a current-frequency conversion circuit, comprising the following steps:

[0007] Determine the full temperature range in which the current-frequency conversion circuit operates;

[0008] Divide the full temperature range into several sub-temperature ranges according to the set step length;

[0009] In each sub-temperature interval, the collected temperature and frequency count value of the current-frequency conversion circuit are fitted with a low-order polynomial, a scale factor temperature drift compensation model of the current-frequency conversion circuit is established, and the polynomial temperature compensation parameters of each sub-temperature interval are obtained to calculate the fitting scale factor of each sub-temperature interval;

[0010] Collect the current temperature of the current-frequency conversion circuit, determine the sub-temperature interval in which the current temperature is located, and obtain the corresponding fitting scaling factor;

[0011] Calculate the compensated scale factor.

[0012] Furthermore, the setting step size of the temperature sub-intervals ranges from 5 to 10°C.

[0013] Furthermore, the low-order polynomial fitting is a polynomial fitting of no more than fourth order.

[0014] Furthermore, the temperature drift compensation method of the current-frequency conversion circuit also includes the following steps:

[0015] The polynomial temperature compensation parameters corresponding to the fitting scale factors of each sub-temperature interval and the sub-temperature interval values ​​are stored in a storage module of the current-frequency conversion circuit;

[0016] The current temperature value of the current-frequency conversion circuit is collected, and the sub-temperature interval where the current temperature is located is located by using a table lookup method. The polynomial temperature compensation parameters corresponding to the sub-temperature interval are called to calculate the fitting scale factor.

[0017] Furthermore, the temperature drift compensation method of the current-frequency conversion circuit further comprises the following steps: collecting a real-time measurement scale factor of the current-frequency conversion circuit;

[0018] The real-time measurement scale factor of the current-frequency conversion circuit is divided by the corresponding fitting scale factor, and multiplied by the standard scale factor of the sub-temperature interval to obtain the compensated scale factor.

[0019] Furthermore, the sub-temperature interval standard scale factor is equal to the full-scale scale factor of the current-frequency conversion circuit divided by the range of the current-frequency conversion circuit.

[0020] The present invention also provides a method for compensating temperature drift and startup characteristics of a current-frequency conversion circuit, comprising the following steps:

[0021] Constructing a first fitting relationship between the scale factor compensation amount during the power-on process of the current-frequency conversion circuit and the temperature change amount of the current-frequency conversion circuit, wherein the scale factor compensation amount is the ratio of the normal temperature stable scale factor to the real-time measurement scale factor, and the temperature change amount is the difference between two adjacent temperatures collected by the current-frequency conversion circuit according to a set time step;

[0022] Constructing a second fitting relationship between the difference between the measured temperature and the stable temperature during the startup process and the temperature change of the current-frequency conversion circuit, wherein the stable temperature is the temperature after power-on stabilization;

[0023] Collecting the temperature of the current frequency conversion circuit, calculating the temperature change, calculating the target stable temperature according to the second fitting relationship, and calculating the scale factor compensation amount according to the temperature change, the target stable temperature and the first fitting relationship;

[0024] The fitting scale factor is calculated based on the target stable temperature and the compensation is performed using the following formula:

[0025]

[0026] Where α is the target stable temperature T 稳 The corresponding scale factor compensation, N 测量 is the actual measured scale factor, N 拟合 The target stable temperature T 稳 The corresponding fitting scale factor.

[0027] Furthermore, the step of constructing a first fitting relationship between the scale factor compensation amount during the power-on process of the current-frequency conversion circuit and the temperature change amount of the current-frequency conversion circuit specifically includes the following steps:

[0028] S101, determining a normal temperature range, a high temperature range, and a low temperature range in which a current-frequency conversion circuit operates;

[0029] S102, controlling the current frequency conversion circuit to start within a normal temperature range;

[0030] S103, inputting a positive current, collecting temperature and forward real-time measurement scale factor according to a set time step, calculating the temperature change and positive scale factor compensation under the time step, performing polynomial fitting, and obtaining a first positive scale factor compensation;

[0031] Input negative current, collect temperature and negative real-time measurement scale factor according to the set time step, calculate the negative scale factor compensation under the time step, perform polynomial fitting, and obtain the first negative scale factor compensation;

[0032] S104, in the high temperature range, checking whether the first positive and negative scale factor compensation amounts meet the use requirements, if so, using the first positive and negative scale factor compensation amounts to perform startup characteristic compensation in the high temperature range, otherwise, recalculating the second positive and negative scale factor compensation amounts in the high temperature range according to step S103;

[0033] S104. In the low temperature range, check whether the first positive and negative scale factor compensation amounts meet the use requirements. If so, use the first positive and negative scale factor compensation amounts to perform startup characteristic compensation in the low temperature range. Otherwise, recalculate the third positive and negative scale factor compensation amounts in the low temperature range according to step S103.

[0034] Furthermore, the method for determining the normal temperature range, high temperature range, and low temperature range in which the current-frequency conversion circuit operates comprises the following steps:

[0035] Take the initial value of normal temperature as 25℃;

[0036] Increase the temperature according to the fixed temperature value to verify the startup characteristic index of the current-frequency conversion circuit. When the index exceeds 20ppm, the temperature is taken as the high temperature threshold;

[0037] Lower the temperature according to the fixed temperature value to verify the startup characteristic index of the current-frequency conversion circuit. When the index exceeds 20ppm, the temperature is taken as the low temperature threshold.

[0038] The low temperature interval, normal temperature interval, and high temperature interval are determined using the low temperature threshold and the high temperature threshold as nodes.

[0039] Furthermore, the first fitting relationship and the second fitting relationship adopt first-order or second-order fitting to improve calculation efficiency.

[0040] Furthermore, the normal temperature stable scaling factor is an average value of the scaling factor from 30 minutes to 1 hour after power-on.

[0041] The beneficial effects of the present invention compared with the prior art are as follows:

[0042] The present invention provides a temperature drift compensation method for a current-frequency conversion circuit, which realizes compensation of the scale factor within the full temperature range by dividing the temperature interval into sub-intervals and low-order nonlinear fitting, and solves the problem that the existing compensation algorithm is restricted by FPGA resources and timing.

[0043] The present invention designs a startup characteristic compensation method for a current-frequency conversion circuit in view of the output change caused by the startup characteristic of the circuit itself during the power-on process. By constructing a model of the scale factor compensation amount and the temperature change amount, the scale factor measured in real time is compensated. The output scale factor during the startup process can be fitted and calculated to the scale factor in a stable state, thereby solving the problem of output instability caused by the self-heating of the circuit in the initial stage of power-on. At the same time, combined with the above-mentioned temperature drift compensation method, the circuit startup characteristic and temperature drift are compensated simultaneously, effectively improving the accuracy of the circuit output. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 A flow chart of a temperature drift compensation method for a current-frequency conversion circuit provided by a specific embodiment of the present invention;

[0046] Figure 2 A schematic diagram of the structure of a current-frequency conversion circuit provided by a specific embodiment of the present invention;

[0047] Figure 3 A schematic diagram of the relationship between the positive and negative scale factor compensation α and ΔT of the accelerometer X channel provided by a specific embodiment of the present invention;

[0048] Figure 4 A schematic diagram of the relationship between the positive and negative scale factor compensation α and ΔT of the accelerometer Y channel provided in a specific embodiment of the present invention;

[0049] Figure 5 A schematic diagram of the relationship between the positive and negative scale factor compensation α and ΔT of the accelerometer Z channel provided by a specific embodiment of the present invention;

[0050] Figure 6 A flow chart of a method for compensating startup characteristics of a current-frequency conversion circuit provided by a specific embodiment of the present invention;

[0051] Figure 7 A cold start comparison of the scale factors of the three-axis accelerometer before and after three-channel compensation provided by a specific embodiment of the present invention;

[0052] Figure 8 A schematic diagram of the relationship between the positive and negative current temperatures and the stable temperature difference T' and ΔT of the X channel provided in a specific embodiment of the present invention;

[0053] Fig. 9A schematic diagram of the relationship between the positive and negative current temperatures and the stable temperature difference T' and ΔT of the Y channel provided in a specific embodiment of the present invention;

[0054] Fig.10 A schematic diagram of the relationship between the positive and negative current temperatures and the stable temperature difference T' and ΔT of the Y channel provided in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0055] Specific embodiments of the present invention are described in detail below. In the following description, for the purpose of explanation and not limitation, specific details are set forth to help fully understand the present invention. However, it will be apparent to those skilled in the art that the present invention may also be practiced in other embodiments that depart from these specific details.

[0056] It should be noted that in order to avoid obscuring the present invention due to unnecessary details, only the device structure and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0057] Example 1

[0058] The scaling factor of the current-frequency conversion circuit refers to the output pulse frequency count value within a unit time of 1s under a 1mA current input.

[0059] This embodiment provides a temperature drift compensation method for a current-frequency conversion circuit, comprising the following steps:

[0060] Determine the full temperature range in which the current-frequency conversion circuit operates;

[0061] Divide the full temperature range into several sub-temperature ranges according to the set step length;

[0062] In each sub-temperature interval, the collected temperature and frequency count value of the current-frequency conversion circuit are fitted with a low-order polynomial, a temperature drift compensation model of the current-frequency conversion circuit scale factor is established, and the polynomial temperature compensation parameters of each sub-temperature interval are obtained to calculate the fitting scale factor of each sub-temperature interval;

[0063] Collect the current temperature of the current-frequency conversion circuit, determine the sub-temperature interval in which the current temperature is located, and obtain the corresponding fitting scaling factor;

[0064] Calculate the compensated scale factor.

[0065] In the present invention, the full temperature range in which the current-frequency conversion circuit operates can be determined through measurement according to the specific working environment and working mode.

[0066] Preferably, in order to reduce the amount of calculation while taking into account the calculation accuracy, the setting step size for dividing the sub-temperature intervals is in the range of 5 to 10°C.

[0067] In the present invention, low-order polynomial fitting refers to polynomial fitting with an order not exceeding fourth order, including 2nd to 4th order nonlinear polynomial fitting and 1st order linear polynomial fitting. Preferably, 1st or 2nd order polynomial fitting can be used to simplify calculation.

[0068] Preferably, in order to facilitate practical application, the temperature drift compensation method of the current-frequency conversion circuit also includes the following steps:

[0069] The polynomial temperature compensation parameters corresponding to the fitting scale factors of each sub-temperature interval and the sub-temperature interval values ​​are stored in a storage module of the current-frequency conversion circuit;

[0070] The current temperature value of the current-frequency conversion circuit is collected, and the sub-temperature interval where the current temperature is located is located by using a table lookup method. The polynomial temperature compensation parameters corresponding to the sub-temperature interval are called to calculate the fitting scale factor.

[0071] Preferably, the temperature drift compensation method of the current-frequency conversion circuit further comprises the following steps: collecting a real-time measurement scale factor of the current-frequency conversion circuit;

[0072] The real-time measurement scale factor of the current-frequency conversion circuit is divided by the corresponding fitting scale factor, and multiplied by the standard scale factor of the sub-temperature interval to obtain the compensated scale factor.

[0073] Preferably, the sub-temperature interval standard scale factor can be set based on experience or through experimental testing. In addition, the standard scale factor can be obtained by calculating the full-scale scale factor of the current-frequency conversion circuit and dividing it by the range of the current-frequency conversion circuit.

[0074] The above temperature drift compensation method uses a combination of table lookup method and low-order polynomial fitting method to establish sample curves of temperature in different temperature intervals within the full temperature range and output pulse count value per unit time of 1s (i.e., scale factor), and performs low-order polynomial fitting on the temperature curves of different temperature intervals. Different temperature intervals are identified by table lookup method, thereby retrieving different polynomial fitting parameters. Compensation of the scale factor within the full temperature range is achieved, effectively solving the problem that the existing compensation algorithm is restricted by FPGA resources and timing.

[0075] Compared with the simple table lookup method, the accuracy depends on the size of the table. To achieve high-precision nonlinear fitting, a large amount of data will be required, and the storage space is high and the search speed is slow. This method takes up less storage space and has a fast search speed. Compared with the high-order polynomial compensation method, the low-order polynomial fitting takes up less resources and has a fast calculation speed, achieving the purpose of fast low-order and high-precision compensation.

[0076] Example 2

[0077] This embodiment takes second-order polynomial fitting as an example to illustrate the technical solution of the present invention.

[0078] This embodiment provides a temperature drift compensation method for a current-frequency conversion circuit. The specific temperature drift compensation algorithm is to establish a polynomial fitting formula 1 of the operating temperature and frequency count value curve in different temperature ranges of the circuit with a step size of 5°C, that is:

[0079]

[0080]

[0081] Thus, the scale factor temperature compensation model in the full temperature range is established, that is, the following formula:

[0082] N=K×T (2)

[0083] in,

[0084]

[0085] Where: n represents the number of segmented temperature ranges, N n is the fitting scale factor of the nth temperature interval (corresponding to the frequency count value), K n0 , K n1 , K n2 are the second-order polynomial temperature compensation parameters for the nth temperature interval, T 0 , T 1 , T n is the temperature value in each temperature interval, from which the temperature drift compensation model of the current-frequency conversion circuit scale factor can be established.

[0086] The compensation parameters and temperature interval values ​​of each temperature interval are stored in the parameter storage device EEPROM of the current frequency conversion circuit. When the temperature compensation processing module obtains the current temperature value transmitted by the temperature acquisition module, the table lookup method is used to quickly locate the temperature interval where the current temperature is located, and the corresponding temperature compensation parameters of the interval are called to calculate the fitting scale factor. The process is as follows: Figure 1 shown.

[0087] For example: When the temperature is T 3 When the fitting count value is selected, the temperature compensation parameter K 30 , K 31 and K 32 According to formula (1),

[0088] N 拟合 =K 30 +K 31 *T+K 32 *T 2 (4)

[0089] You can calculate N拟合 To fit the scale factor, further, the compensated scale factor is calculated using Formula 5:

[0090]

[0091] Among them, N 补偿后 Refers to the scale factor after compensation; N 测量 is the actual measured scale factor, which can be measured and output in real time by the current-frequency conversion circuit; N 拟合 is the scaling factor calculated by the piecewise low-order fitting formula; N 标准 is the standard scaling factor expected in each temperature range, which is a fixed value. Preferably, N 标准 It is obtained by dividing the full-scale scale factor of the current-frequency conversion circuit by the range of the current-frequency conversion circuit.

[0092] Through the above calculation, the compensated scale factor in the full temperature range can be obtained. This segmented second-order fitting compensation algorithm will greatly reduce the number of multipliers and adders used in the high-order polynomial compensation algorithm, reduce resource usage, reduce calculation time, and also avoid the problem of incomplete fitting caused by a single fitting curve in the full temperature range.

[0093] Example 3

[0094] Aiming at the problem that the output changes dramatically due to the self-starting characteristics of the current-frequency conversion circuit at the initial stage of power-on, and it takes a certain period of time to stabilize, the present invention provides a startup characteristic compensation method for the current-frequency conversion circuit, and establishes a model of the ratio of the scale factor at a stable temperature 30 minutes after the conversion circuit is started to the scale factor measured in real time during the startup process and the temperature change. The output scale factor during the startup process can be fitted and calculated to the scale factor in the stable state, thereby solving the problem of output instability caused by the self-heating of the circuit at the initial stage of power-on.

[0095] The current-frequency conversion circuit will generate positive and negative scaling factors according to the positive and negative input current. Since the positive and negative scaling factors are not completely symmetrical, the positive and negative scaling factors of the current-frequency conversion circuit need to be considered separately when performing startup characteristic compensation.

[0096] The full temperature range of the current frequency conversion circuit usually includes a low temperature range, a normal temperature range and a high temperature range, and the three ranges are divided by a low temperature threshold and a high temperature threshold. In the present invention, the normal temperature initial value is set to 25°C. After establishing the normal temperature startup characteristic compensation model, the model is used to verify the startup characteristic index at different temperatures every 20°C. When the index exceeds 20ppm and the temperature is higher than 25°C, the temperature is considered to be the high temperature threshold. When the temperature is lower than the normal temperature by 25°C and the startup characteristic index exceeds 20ppm, the temperature is considered to be the low temperature threshold. The temperature between the two temperature thresholds is the normal temperature range.

[0097] The present invention provides a method for compensating startup characteristics of a current-frequency conversion circuit, comprising the following steps:

[0098] Determine the normal temperature range, high temperature range, and low temperature range in which the current frequency conversion circuit operates;

[0099] Controlling the current frequency conversion circuit to start within a normal temperature range;

[0100] Input a positive current, collect temperature and positive real-time measurement scale factor according to a set time step, calculate the temperature change and positive scale factor compensation under the time step, perform polynomial fitting, and obtain the first positive scale factor compensation;

[0101] Input negative current, collect temperature and negative real-time measurement scale factor according to the set time step, calculate the negative scale factor compensation under the time step, perform polynomial fitting, and obtain the first negative scale factor compensation;

[0102] In the high temperature range, check whether the first positive and negative scale factor compensation amounts meet the use requirements. If so, the first positive and negative scale factor compensation amounts are used to compensate for the startup characteristics in the high temperature range. Otherwise, recalculate the second positive and negative scale factor compensation amounts in the high temperature range according to the above method.

[0103] In the low temperature range, check whether the first positive and negative scale factor compensation amounts meet the use requirements. If yes, use the first positive and negative scale factor compensation amounts to perform startup characteristic compensation in the low temperature range. Otherwise, recalculate the third positive and negative scale factor compensation amounts in the low temperature range according to the above method.

[0104] The current temperature of the current-frequency conversion circuit is collected, the temperature change from the initial temperature is calculated, the corresponding scale factor compensation is calculated, and the scale factor measured in real time at the current moment is collected to obtain the scale factor after the startup characteristic compensation.

[0105] In the present invention, the temperature variation is the difference between two adjacent temperatures collected by the current-frequency conversion circuit according to a set time step, that is, the difference between the temperature collected at the current time step and the temperature collected at the previous time step.

[0106] In the present invention, the positive / negative scale factor compensation amount is the normal temperature stable scale factor divided by the positive / negative real-time measurement scale factor. The normal temperature stable scale factor in the present invention is the average value of the scale factor from 30 minutes to 1 hour after power-on.

[0107] In the present invention, the time step of data acquisition is 10s.

[0108] The startup characteristic compensation algorithm can fit the output scale factor during the startup process to the scale factor under the stable state by establishing a model of the ratio of the scale factor under the stable temperature to the current scale factor and the temperature change. This method has a simple model and small calculation amount.

[0109] Example 4

[0110] Taking a three-axis accelerometer as an example, the technical solution of the startup characteristic compensation method of the present invention is described in detail.

[0111] In this embodiment, the three-axis accelerometer includes X, Y, and Z channels, and each channel uses Figure 2 The current-frequency conversion circuit shown includes positive and negative scale factors for each channel.

[0112] In this embodiment, the current frequency conversion circuit, such as Figure 2 As shown, the circuit includes: a current frequency conversion main circuit, a control circuit, and an interface circuit. The current frequency conversion main circuit is connected to the accelerometer, converts the output current of the accelerometer into an integral voltage, and then uses a constant current source circuit to stabilize the output current. The control circuit compares the integral voltage with a preset threshold voltage and outputs a proportional digital pulse (the pulse frequency count value is the scale factor). The interface circuit is used to connect to an external device, such as a reading display device.

[0113] The main current frequency conversion circuit includes an integration circuit, an ADC acquisition circuit, a constant current source circuit, and a switch circuit. The integration circuit is used to integrate the input current to generate an integral voltage; the ADC sampling circuit is used to periodically acquire the integral voltage; the constant current source circuit is used to stabilize the output current to the integration circuit; and the switch circuit controls the connection or disconnection of the constant current source circuit.

[0114] The control circuit uses an FPGA controller to realize functions such as comparison of the integrated voltage, constant current source control, compensation calculation of digital pulses, and output. The logic module of the FPGA mainly includes an ADC acquisition module, a temperature acquisition module, a pulse counting module, a temperature compensation processing module, an output module, and a constant current source control module. The ADC acquisition module collects the integrated voltage and compares the voltage value with the preset threshold voltage. When the integrated voltage is lower than the threshold output low level, the constant current source control module controls the switch circuit to disconnect and the constant current source circuit is not turned on. When the integrated voltage is higher than the threshold value and outputs a high level, the constant current source control module controls the switch circuit to connect and the constant current source circuit is turned on, so that the current frequency conversion circuit enters the feedback stage. The pulse counting module counts the output pulses, that is, records the frequency count value, and sends the frequency count value to the temperature compensation processing module. Based on the frequency count value and the real-time acquisition temperature, the temperature compensation processing module compensates the real-time measurement scale factor in the full temperature range to the standard scale factor according to the temperature compensation algorithm, and outputs the standard scale factor through the output module.

[0115] The key to startup characteristic compensation is to find the relationship between the compensation amount during the power-on process of the conversion circuit and the temperature change of the conversion circuit. Suppose the normal temperature stable values ​​of the positive and negative scale factors of the accelerometer combination (i.e., the normal temperature stable scale factors) are N1. + (t 稳 ) and N1 - (t 稳 ), in order to ensure that the scale factor and N1 are consistent during the startup of the current-frequency conversion circuit + (t 稳 ) and N1 - (t 稳 ), the positive and negative scale factor compensation α+ and α- can be obtained as shown in Formula 6 and Formula 7.

[0116]

[0117]

[0118] In formula 6 and formula 7, N1 + (t) is the real-time measurement data N of the positive scaling factor in formula 5 测量 , N1 - (t) is the real-time measurement data N of the negative scaling factor in formula 5 测量 , which is the scale factor before temperature compensation. N1 + (t 稳 ) and N1 - (t 稳 ) is used to model the startup characteristics, and the scale factor is measured after the temperature stabilizes 30 minutes after the circuit is started. Preferably, it can be the average value of the scale factor from 30 minutes to 1 hour after power-on.

[0119] By processing the modeling data, the relationship between the current-frequency conversion circuit scale factor compensation α and the temperature change ΔT (to increase the resolution of the temperature change, the 10s cumulative value is used for calculation) can be obtained as follows: Figure 3 to Figure 5 shown.

[0120] By measuring the mean value of the positive and negative scale factors and the temperature change within 30 minutes of cold start of each channel and a time step of 10 seconds, the data model of the scale factor compensation α and the temperature change ΔT can be obtained. Figure 3 to Figure 5 From the modeling data, it can be seen that when the temperature change ΔT is less than or equal to 0.8℃, the scale factor compensation α is linearly related to the temperature change ΔT; when the temperature change ΔT is greater than 0.8℃, the relationship is more divergent and covers fewer temperature points. In order to simplify the compensation algorithm and avoid over-compensation or under-compensation problems, when ΔT is greater than 0.8℃, it is calculated as if ΔT is equal to 0.8℃.

[0121] It can be concluded from the above analysis that, in this embodiment, the startup characteristic compensation model of the current-frequency conversion circuit is a linear model, and the relationship between the scale factor compensation amount α and the temperature change amount ΔT is shown in Formula 8.

[0122] α=k×ΔT+1(ΔT≤0.8) (8)

[0123] Where k is the scale factor compensation coefficient. When ΔT is greater than 0.8°C, the calculation is performed based on ΔT being equal to 0.8°C.

[0124] Based on the compensation model shown in Formula 8, the three-axis accelerometer can obtain a set of 6 compensation coefficients k, and according to the set low temperature threshold and high temperature threshold, the corresponding scale factor compensation coefficients kH, kN, and kL can be obtained in different high, normal, and low temperature ranges. By judging which temperature range the current temperature belongs to, the corresponding compensation coefficient is selected to calculate the scale factor compensation amount. The current frequency conversion circuit startup characteristic compensation algorithm used in this embodiment is as follows: Figure 6 shown.

[0125] Through formula 8 and the compensation process Figure 6 It can be seen that by setting the low temperature threshold, the high temperature threshold or the compensation parameter k, any combination of the startup characteristic compensation of the current-frequency conversion circuit under three temperatures can be achieved, which is convenient for practical application.

[0126] Through the above-mentioned startup characteristic compensation method, the unstable scaling factor of the conversion circuit within 30 minutes of cold start power-on can be stably output, and the startup characteristic index of the circuit can be improved from the original 50ppm to better than 8ppm, greatly improving the startup characteristic index of the IF conversion circuit. Figure 7 This is a comparison chart of the scaling factors of the three channels before and after compensation at normal temperature starting with temperature changes.

[0127] Example 5

[0128] When temperature drift compensation and startup characteristic temperature compensation are combined, since temperature drift compensation is actually performed under stable working conditions, it is necessary to establish the relationship between the difference T' between the current temperature and the stable temperature during startup and the temperature change ΔT. The difference between the stable temperature and the currently measured temperature during startup can be calculated using the temperature change ΔT, such as Figure 8-10 As shown, the current temperature value during the startup process is then added to the difference to obtain the stable temperature.

[0129] T 稳定 =T'+T 当前 (9)

[0130] T'=ΔT×k 1T +ΔT 2 ×k 2T +b T (10)

[0131] T' is the difference between the measured temperature and the stable temperature, T 当前 Refers to the measured temperature value, T 稳定 It refers to the temperature measured after stabilization for 30 minutes after power-on. ΔT is the temperature change (the difference between two adjacent temperatures collected by the current-frequency conversion circuit according to the set time step). 1T , k 2T , b T Calculate parameters for temperature-stable second-order compensation.

[0132] Combining the startup characteristic compensation with the stable temperature compensation algorithm can realize the compensation of startup characteristics and temperature drift. Taking the normal temperature startup characteristic compensation as an example, the compensation algorithm is as follows:

[0133] When the ambient temperature is T, the stable temperature is T after the conversion circuit is powered on for 30 minutes. 稳 , the temperature of the conversion circuit during startup is T 测 , using formulas 9 and 10, the target stable temperature is calculated as:

[0134] T 稳 =T 测 +ΔT*k 1T +ΔT 2 ×k 2T +b T

[0135] After obtaining the stable temperature, the final compensation result can be obtained by combining the startup characteristic compensation and the stable temperature drift compensation algorithm. The compensation formula is as follows:

[0136]

[0137] Among them, N 总补偿 is the result of startup characteristic compensation and temperature drift compensation, α is the target stable temperature T 稳 The corresponding scale factor compensation, N 测量 is the actual measured scale factor, N 拟合 The target stable temperature T 稳 The corresponding fitting scale factor.

[0138] Features described and / or illustrated above for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or used in place of features in other embodiments.

[0139] It should be emphasized that the term "include / comprises" when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or combinations thereof.

[0140] The many features and advantages of these embodiments are apparent from this detailed description, and thus the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not intended that the embodiments of the invention be limited to the exact construction and operation illustrated and described, but rather all suitable modifications and equivalents falling within the scope thereof are intended to be covered.

[0141] 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.

[0142] Parts of the present invention that are not described in detail are well known to those skilled in the art.

Claims

1. A method for compensating temperature drift of a current-frequency conversion circuit, characterized in that: The steps include: Determine the full temperature range in which the current-frequency conversion circuit operates; Divide the full temperature range into several sub-temperature ranges according to the set step length; In each sub-temperature interval, the collected temperature and frequency count value of the current-frequency conversion circuit are fitted with a low-order polynomial, a scale factor temperature drift compensation model of the current-frequency conversion circuit is established, and the polynomial temperature compensation parameters of each sub-temperature interval are obtained; Collect the current temperature of the current-frequency conversion circuit, determine the sub-temperature interval in which the current temperature is located, and obtain the corresponding fitting scaling factor; Calculate the compensated scale factor.

2. The temperature drift compensation method according to claim 1, characterized in that: The setting step size of the temperature sub-intervals is in the range of 5 to 10° C.; the low-order polynomial fitting is a polynomial fitting of no more than the fourth order.

3. The temperature drift compensation method according to claim 1, characterized in that: The following steps are also included: The polynomial temperature compensation parameters corresponding to the fitting scale factors of each sub-temperature interval and the sub-temperature interval values ​​are stored in a storage module of the current-frequency conversion circuit; The current temperature value of the current-frequency conversion circuit is collected, and the sub-temperature interval where the current temperature is located is located by using a table lookup method. The polynomial temperature compensation parameters corresponding to the sub-temperature interval are called to calculate the fitting scale factor.

4. The temperature drift compensation method according to claim 1, characterized in that: The following steps are also included: Acquiring real-time measurement scale factors of current-to-frequency conversion circuits; The real-time measurement scale factor of the current-frequency conversion circuit is divided by the corresponding fitting scale factor, and multiplied by the standard scale factor of the sub-temperature interval to obtain the compensated scale factor.

5. The temperature drift compensation method according to claim 4, characterized in that: The sub-temperature interval standard scale factor is equal to the full-scale scale factor of the current-frequency conversion circuit divided by the current-frequency conversion circuit range.

6. A method for compensating temperature drift and startup characteristics of a current-frequency conversion circuit, characterized in that: The steps include: Constructing a first fitting relationship between the scale factor compensation amount during the startup process of the current-frequency conversion circuit and the temperature change amount of the current-frequency conversion circuit, wherein the scale factor compensation amount is the ratio of the normal temperature stable scale factor to the real-time measurement scale factor, and the temperature change amount is the difference between two temperatures collected by the current-frequency conversion circuit according to a set time step; Constructing a second fitting relationship between the difference between the measured temperature and the stable temperature during the startup process and the temperature change of the current-frequency conversion circuit, wherein the stable temperature is the temperature after power-on stabilization; Collect the current temperature of the current frequency conversion circuit, calculate the temperature change, calculate the target stable temperature according to the second fitting relationship, and calculate the scale factor compensation amount according to the temperature change, the target stable temperature and the first fitting relationship; The fitting scale factor is calculated based on the target stable temperature and the compensation is performed using the following formula: Where α is the scale factor compensation corresponding to the target stable temperature, N 测量 is the actual measured scale factor, N 拟合 is a fitting scaling factor corresponding to a target stable temperature, wherein the fitting scaling factor is calculated using the temperature drift compensation method described in any one of claims 1 to 5.

7. The method for compensating temperature drift and startup characteristics according to claim 6, characterized in that: The step of constructing a first fitting relationship between the scale factor compensation amount during the power-on process of the current-frequency conversion circuit and the temperature change amount of the current-frequency conversion circuit specifically includes the following steps: S101, determining a normal temperature range, a high temperature range, and a low temperature range in which a current-frequency conversion circuit operates; S102, controlling the current frequency conversion circuit to start within a normal temperature range; S103, inputting a positive current, collecting temperature and forward real-time measurement scale factor according to a set time step, calculating the temperature change and positive scale factor compensation under the time step, performing polynomial fitting, and obtaining a first positive scale factor compensation; Input negative current, collect temperature and negative real-time measurement scale factor according to the set time step, calculate the negative scale factor compensation under the time step, perform polynomial fitting, and obtain the first negative scale factor compensation; S104, in the high temperature range, checking whether the first positive and negative scale factor compensation amounts meet the use requirements, if so, using the first positive and negative scale factor compensation amounts to perform startup characteristic compensation in the high temperature range, otherwise, recalculating the second positive and negative scale factor compensation amounts in the high temperature range according to step S103; S104. In the low temperature range, check whether the first positive and negative scale factor compensation amounts meet the use requirements. If so, use the first positive and negative scale factor compensation amounts to perform startup characteristic compensation in the low temperature range. Otherwise, recalculate the third positive and negative scale factor compensation amounts in the low temperature range according to step S103.

8. The method for compensating temperature drift and startup characteristics according to claim 7, characterized in that: The step S101 specifically includes the following steps: Take the initial value of normal temperature as 25℃; Increase the temperature according to the fixed temperature value to verify the startup characteristic index of the current-frequency conversion circuit. When the index exceeds 20ppm, the temperature is taken as the high temperature threshold; Lower the temperature according to the fixed temperature value to verify the startup characteristic index of the current-frequency conversion circuit. When the index exceeds 20ppm, the temperature is taken as the low temperature threshold. The low temperature interval, normal temperature interval, and high temperature interval are determined using the low temperature threshold and the high temperature threshold as nodes.

9. The method for compensating temperature drift and startup characteristics according to claim 6, characterized in that: The first fitting relational expression and the second fitting relational expression adopt first-order or second-order fitting to improve calculation efficiency.

10. The method for compensating temperature drift and startup characteristics according to claim 6, characterized in that: The normal temperature stable scale factor is the average value of the scale factor from 30 minutes to 1 hour after power-on.

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