Pressure precision compensation method and system for pressure bridge

Abstract

The invention provides a pressure precision compensation method and system for a pressure bridge, and the method comprises the steps: providing a calibration platform, and collecting the temperature calibration code values of a pressure core body at a plurality of preset temperature points and the pressure calibration code values of a plurality of preset pressure points through the calibration platform; performing Kalman filtering on the pressure calibration code value to obtain a target pressure code value of the pressure core body; and performing Newton interpolation based on the target pressure code value and the temperature calibration code value to obtain a compensated trimming pressure value. The compensation precision of the pressure bridge can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of sensor control, and in particular to a pressure accuracy compensation method and system for a pressure bridge. Background Art

[0002] Traditional pressure accuracy temperature compensation is mainly to compensate for the temperature drift and nonlinearity of the pressure core output by external instrument amplification hardware circuit combined with commonly used least squares method, spline interpolation method or neural network technology. However, since the differential voltage output by the pressure Wheatstone bridge is a weak signal with low signal-to-noise ratio, filtering of the signal is crucial. Due to the low accuracy requirements and cost factors, traditional pressure cores are directly adjusted by hardware or by lookup tables, compensation coefficients, etc., but the pressure core adjusted by the above methods has the disadvantages of low accuracy and poor long-term stability. Summary of the invention

[0003] In view of the above problems existing in the prior art, the present invention proposes a pressure accuracy compensation method and system for a pressure bridge, which mainly solves the problems of low accuracy and poor stability of traditional adjustment methods.

[0004] In order to achieve the above purpose and other purposes, the technical solution adopted by the present invention is as follows.

[0005] The present application provides a pressure accuracy compensation method for a pressure bridge, the method comprising: providing a calibration platform, collecting temperature calibration code values ​​of a pressure core at multiple preset temperature points and pressure calibration code values ​​of multiple preset pressure points through the calibration platform; performing Kalman filtering on the pressure calibration code values ​​to obtain target pressure code values ​​of the pressure core; performing Newton interpolation based on the target pressure code values ​​and the temperature calibration code values ​​to obtain a compensated adjusted pressure value.

[0006] In one embodiment of the present application, the step of collecting temperature calibration code values ​​of the pressure core at multiple preset temperature points and pressure calibration code values ​​of multiple preset pressure points through the calibration platform includes:

[0007] Placing the pressure core in a cavity and adjusting the temperature in the cavity;

[0008] Applying pressure values ​​corresponding to a plurality of preset pressure points to the pressure core;

[0009] Collecting pressure state signals and temperature state signals at different preset pressure points and preset temperature points;

[0010] The pressure state signal and the temperature state signal are amplified and converted into digital signals to obtain corresponding temperature calibration code values ​​and pressure calibration code values.

[0011] In one embodiment of the present application, the step of performing Kalman filtering on the pressure calibration code value includes: filtering through a Kalman dynamic model, wherein the Kalman dynamic model is determined based on the nonlinearity, sensitivity drift, temperature drift, zero drift and process noise of the pressure core.

[0012] In one embodiment of the present application, the step of performing Newton interpolation based on the target pressure code value and the temperature calibration code value includes: performing a first interpolation according to the temperature calibration code value to obtain a dynamic data linked list, wherein the dynamic data linked list contains the fitting pressure corresponding to each preset pressure point; performing a second interpolation according to the dynamic data linked list and the target pressure code value to obtain the adjusted pressure value.

[0013] The present application also provides a pressure accuracy compensation system for a pressure bridge, the system comprising: a calibration platform, through which temperature calibration code values ​​of a pressure core at multiple preset temperature points and pressure calibration code values ​​at multiple preset pressure points are collected; a filtering module, for performing Kalman filtering on the pressure calibration code values ​​to obtain target pressure code values ​​of the pressure core; an interpolation module, for performing Newton interpolation based on the target pressure code values ​​and the temperature calibration code values ​​to obtain a compensated adjusted pressure value.

[0014] In one embodiment of the present application, the filtering module and the interpolation module are arranged in the cloud, and the temperature calibration code value and the pressure calibration code value of the calibration platform are collected through the cloud.

[0015] As described above, the pressure accuracy compensation method and system of a pressure bridge proposed in the present application have the following beneficial effects.

[0016] This application constructs a calibration platform to calibrate the corresponding code values ​​of the pressure bridge under different temperatures and pressures, removes interference noise based on Kalman filtering, and then compensates for nonlinear errors through Newton interpolation to obtain more accurate adjusted pressure values, thereby ensuring the accuracy and long-term stability of the pressure bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the flow of a pressure accuracy compensation method of a pressure bridge in one embodiment of the present application.

[0018] Figure 2 Schematic diagram of the circuit architecture of the calibration platform in one embodiment of the present application.

[0019] Figure 3 This is a schematic diagram of the full-temperature range accuracy test results of three prototypes in one embodiment of the present application.

[0020] Figure 4 This is a schematic diagram of the forward and reverse stroke accuracy test results of three prototypes at room temperature in one embodiment of the present application.

[0021] Figure 5 1 is a block diagram of a pressure accuracy compensation system of a pressure bridge in one embodiment of the present application. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0023] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0024] The inventors have found that:

[0025] Traditional pressure accuracy temperature compensation is mainly to compensate for the temperature drift and nonlinearity of the pressure core output by external instrument amplification hardware circuit combined with commonly used least squares method, spline interpolation method or neural network technology. However, since the differential voltage output by the pressure Wheatstone bridge is a weak signal with low signal-to-noise ratio, filtering of the signal is crucial. Due to the low accuracy requirements and cost factors, traditional pressure cores are directly adjusted by hardware or by lookup tables, compensation coefficients, etc., but the pressure core adjusted by the above methods has the disadvantages of low accuracy and poor long-term stability.

[0026] The output voltage differential signal of the pressure bridge has the disadvantages of weak signal and low signal-to-noise ratio; therefore, it is necessary to amplify and filter the output signal of the pressure bridge through the instrument amplifier hardware circuit and the software filtering algorithm to improve the signal-to-noise ratio of the original signal, and finally compensate the pressure accuracy through the correction algorithm. In the pressure signal correction and compensation link, the filtering process of the original signal is very important. Therefore, the embodiment of the present application proposes a pressure accuracy compensation method and system for a pressure bridge, which performs full-temperature range and nonlinear compensation correction of pressure accuracy based on Kalman filtering combined with a double Newton interpolation algorithm. The main idea of ​​the present invention is to filter the differential output signal through the Kalman filtering algorithm to improve the signal-to-noise ratio of the original signal, and at the same time combine the double Newton algorithm to adjust and correct the pressure accuracy. The technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0027] See also Figure 1 , Figure 1 This is a flow chart of a pressure accuracy compensation method of a pressure bridge in an embodiment of the present application. The method includes:

[0028] Step S100, providing a calibration platform, and collecting temperature calibration code values ​​of the pressure core at multiple preset temperature points and pressure calibration code values ​​at multiple preset pressure points through the calibration platform.

[0029] In one embodiment, the steps of collecting temperature calibration code values ​​of the pressure core at multiple preset temperature points and pressure calibration code values ​​of multiple preset pressure points through the calibration platform include: placing the pressure core in a cavity and adjusting the temperature in the cavity; applying pressure values ​​corresponding to multiple preset pressure points to the pressure core; collecting pressure state signals and temperature state signals at different preset pressure points and preset temperature points; converting the pressure state signals and the temperature state signals into digital signals after amplifying them to obtain corresponding temperature calibration code values ​​and pressure calibration code values.

[0030] The calibration platform may include an oven, a pressure controller, a DC power supply, a host computer, and a hardware circuit board. The pressure core of the pressure bridge may be placed in the oven. The oven may be a closed cavity structure. The DC power supply powers the pressure core. Of course, the host computer, the hardware circuit board, the pressure controller, etc. may also be powered by a DC power supply, or by other power supply modules. They may be set and adjusted according to actual application requirements, and there are no restrictions here. The pressure controller may control the pressure applied to the pressure core, and the host computer may issue instructions to control the temperature of the oven. Of course, the oven may also have its own temperature control module, such as heating by controlling the resistance wire flowing through the oven, adjusting the temperature within the red line, etc. The specific temperature adjustment method may be set and adjusted according to actual application requirements, and there are no restrictions here. The host computer may be connected to the hardware circuit board, which is provided with an analog-to-digital converter and at least two instrument amplifiers. Please refer to the specific temperature control module. Figure 2 , Figure 2The circuit architecture diagram of the calibration platform in one embodiment of the present application. One of the instrument amplifiers is connected to the differential output of the pressure bridge, and the differential output signal is amplified and output to the analog-to-digital converter to convert it into a digital signal to obtain the corresponding pressure calibration code value; the other instrument amplifier is connected to the positive and negative input terminals of the pressure bridge, and the voltage signal corresponding to the temperature can be collected and amplified and output to the analog-to-digital converter to convert it into a corresponding digital signal to obtain the temperature calibration code value. Of course, the hardware circuit board may also include other peripheral devices, such as bias circuits, resistor-capacitor filter circuits, etc. The circuit composition in the specific hardware circuit board can be set and adjusted according to the actual application requirements, and there is no restriction here. When calibrating, multiple temperature points and pressure points can be preset. The host computer controls the pressure controller to adjust the pressure value applied to the pressure core according to the set pressure point. Similarly, the host computer can also issue instructions to adjust the temperature of the oven according to the preset temperature point.

[0031] In one embodiment, the analog-to-digital converter may adopt a high-precision, high-resolution Σ-Δ ADC, which can effectively restore the original signal and ensure the accuracy of compensation correction.

[0032] In one embodiment, the preset temperature points may be -40°C, -20°C, 0°C, 30°C, 60°C and 80°C, and the preset pressure points may be 0%FS, 20%FS, 40%FS, 60%FS, 80%FS and 100%FS. FS represents the full scale of the pressure bridge. Of course, the specific temperature points and pressure points are set and adjusted according to actual application requirements, and are not limited here.

[0033] Step S110, performing Kalman filtering on the pressure calibration code value to obtain a target pressure code value of the pressure core.

[0034] In one embodiment, the pressure calibration code value can be dynamically estimated by the Kalman filter algorithm, and the Kalman dynamic model can be established by fully considering the nonlinearity, sensitivity, temperature, zero drift and noise of the pressure core. The dynamic model can calculate the target output value, that is, the target pressure code value of the pressure core after filtering. The establishment of the Kalman dynamic model mainly involves the following Kalman modeling formulas, as follows:

[0035] x k =F k *x k-1 +B k *u k +ω k (1)

[0036] Where: u k is the calibration signal collected by the pressure core, x k-1 is the state variable, i.e. the temperature drift state of the pressure core, ωk is the process noise; F k is acting on x k-1 State transition model on B k is the vector acting on the controller u k Input-control model on .

[0037] The observation equation is shown in formula (2):

[0038] Z k =H k *x k +v k (2)

[0039] Where: Z k is the observed variable, i.e. the sensitivity of the pressure core, v k H represents the observation noise, i.e. the original calibration signal noise. k It is the observation model, which maps the real state space into the observation space;

[0040] The state error evaluation established in the embodiment of the present application is performed by the following (3):

[0041]

[0042] in, Indicates the temperature drift state error at adjacent moments.

[0043] Step S120, performing Newton interpolation based on the target pressure code value and the temperature calibration code value to obtain a compensated adjusted pressure value.

[0044] In one embodiment, the step of performing Newton interpolation based on the target pressure code value and the temperature calibration code value includes: performing a first interpolation based on the temperature calibration code value to obtain a dynamic data linked list, wherein the dynamic data linked list contains the fitting pressure corresponding to each preset pressure point; performing a second interpolation based on the dynamic data linked list and the target pressure code value to obtain the adjusted pressure value.

[0045] Specifically, the calibrated pressure code value after filtering can be obtained through equations (1) to (3), and the temperature code value can be combined with the double Newton algorithm equations (4) to (5) to calculate the pressure value P after pressure accuracy compensation. nthex (i.e. adjust the pressure value);

[0046] P_code x =k2*(t c -t0)*(t c -t1)+k1*(t c -t0)+k0(x=0...6) (4)

[0047] Where: k2, k1, k0 are code values ​​P_code respectively x The fitting coefficients; t1, t0 are the currently collected temperature code values ​​t c The two adjacent temperature calibration code values ​​below; P_code x It is the value of dynamic data linked list;

[0048] The dynamic data chain table calculated by the above formula (5) is used to calculate the final accuracy adjustment value P considering the influence of temperature drift, sensitivity, zero drift, etc. on the accuracy of the pressure core. nthex ;

[0049] P nihex =k nihe2 *(P c -P_code0)*(P c -P_code1)+k nihe1 *(P c -P_code0)+k nihe0 (5)

[0050] Where: k nihe2 , k nihe1 , k nihe0 The final fitting pressure P nihex The fitting coefficient, P c It is the pressure code value currently sampled.

[0051] The double Newton interpolation method can reduce nonlinear errors and improve compensation accuracy.

[0052] See also Figure 3 and Figure 4 ,from Figure 3 It can be concluded that the scheme proposed in this application (prototype 1) can achieve a comprehensive pressure compensation accuracy within 0.06% FS in the full temperature range of -40℃~80℃; Figure 4 The pressure core accuracy is obtained by testing at room temperature (25°C). Figure 4 It can be concluded that: under normal temperature, under the working conditions of forward and reverse stroke, the pressure of the pressure controller is changed to test the adjustment accuracy of the embodiment of the present application. The accuracy (prototype 1) after adjustment by the scheme of the embodiment of the present application can be within 0.06% FS, so the feasibility and correctness of the technical scheme proposed in the embodiment of the present application can be verified. Prototypes 2 and 3 are the accuracy after adjustment by other methods.

[0053] By analyzing the test result data, we can obtain intuitive results as shown in the figure below, so we can conclude that the scheme proposed in the embodiment of the present application can better realize the compensation and correction of the temperature, nonlinearity, zero point and sensitivity of the pressure core that affect the final accuracy of the pressure core, thereby verifying the feasibility and correctness of the scheme of the embodiment of the present application, and providing a new compensation and adjustment idea for the core accuracy adjustment.

[0054] See also Figure 5 , Figure 5 This is a block diagram of a pressure accuracy compensation system for a pressure bridge in an embodiment of the present application. The system includes a calibration platform, through which the temperature calibration code values ​​of the pressure core at multiple preset temperature points and the pressure calibration code values ​​at multiple preset pressure points are collected; a filtering module, which is used to perform Kalman filtering on the pressure calibration code values ​​to obtain the target pressure code values ​​of the pressure core; and an interpolation module, which is used to perform Newton interpolation based on the target pressure code values ​​and the temperature calibration code values ​​to obtain the compensated adjusted pressure value.

[0055] In one embodiment, the filtering module and the interpolation module are arranged in the cloud, and the temperature calibration code value and the pressure calibration code value of the calibration platform are collected through the cloud, and the collected data are sent to the cloud for processing, and the Kalman filtering and double Newton interpolation are performed by using the computing power of the cloud to obtain the target pressure code value. The specific system execution process has been described in detail in the aforementioned method embodiment, and will not be repeated here.

[0056] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A pressure accuracy compensation method for a pressure bridge, characterized in that: The method comprises: Providing a calibration platform, through which the temperature calibration code values ​​of the pressure core at multiple preset temperature points and the pressure calibration code values ​​at multiple preset pressure points are collected; Performing Kalman filtering on the pressure calibration code value to obtain a target pressure code value of the pressure core; Newton interpolation is performed based on the target pressure code value and the temperature calibration code value to obtain a compensated adjusted pressure value.

2. The pressure accuracy compensation method of the pressure bridge according to claim 1, characterized in that: The step of collecting the temperature calibration code values ​​of the pressure core at multiple preset temperature points and the pressure calibration code values ​​at multiple preset pressure points through the calibration platform includes: Placing the pressure core in a cavity and adjusting the temperature in the cavity; Applying pressure values ​​corresponding to a plurality of preset pressure points to the pressure core; Collecting pressure state signals and temperature state signals at different preset pressure points and preset temperature points; The pressure state signal and the temperature state signal are amplified and converted into digital signals to obtain corresponding temperature calibration code values ​​and pressure calibration code values.

3. The pressure accuracy compensation method of the pressure bridge according to claim 1, characterized in that: The step of performing Kalman filtering on the pressure calibration code value includes: filtering through a Kalman dynamic model, wherein the Kalman dynamic model is determined based on the nonlinearity, sensitivity drift, temperature drift, zero drift and process noise of the pressure core.

4. The pressure accuracy compensation method of the pressure bridge according to claim 1, characterized in that: The step of performing Newton interpolation based on the target pressure code value and the temperature calibration code value includes: performing a first interpolation according to the temperature calibration code value to obtain a dynamic data linked list, wherein the dynamic data linked list contains the fitting pressure corresponding to each preset pressure point; performing a second interpolation according to the dynamic data linked list and the target pressure code value to obtain the adjusted pressure value.

5. A pressure accuracy compensation system for a pressure bridge, characterized in that: The system comprises: A calibration platform, through which temperature calibration code values ​​of the pressure core at multiple preset temperature points and pressure calibration code values ​​at multiple preset pressure points are collected; A filtering module, used for performing Kalman filtering on the pressure calibration code value to obtain a target pressure code value of the pressure core; The interpolation module is used to perform Newton interpolation based on the target pressure code value and the temperature calibration code value to obtain a compensated adjusted pressure value.

6. The pressure accuracy compensation system of the pressure bridge according to claim 5, characterized in that: The filtering module and the interpolation module are arranged in the cloud, and the temperature calibration code value and the pressure calibration code value of the calibration platform are collected through the cloud.

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