Temperature compensation method for zero bias in MEMS accelerometers

Abstract

This invention discloses a temperature compensation method for zero bias in MEMS accelerometers. The method obtains the scaling factor temperature compensation coefficient and the static zero bias temperature compensation amount of the MEMS accelerometer. The scaling factor temperature compensation coefficient is obtained through dynamic testing of the MEMS accelerometer during a first temperature change. The static zero bias temperature compensation amount is obtained through static testing of the MEMS accelerometer during a second temperature change. The real-time output value of the MEMS accelerometer is then compensated using a combination of the scaling factor temperature compensation coefficient and the static zero bias temperature compensation amount. This invention achieves significantly higher compensation accuracy than traditional single static compensation methods by separating error sources and employing differentiated compensation strategies. It improves the performance stability of the inertial measurement unit (IMU) operating across the entire temperature range. It can be implemented simply through software algorithm optimization, making it easy to promote and apply to existing products. It is cost-effective and has high economic value.

Description

Technical Field

[0001] This invention relates to the field of inertial navigation technology, and more specifically to a temperature compensation method for zero bias in MEMS accelerometers. Background Technology

[0002] When MEMS accelerometers operate with inertial measurement units (IMUs), their operating temperature range is typically -40℃ to +65℃. Within this wide temperature range, due to the temperature characteristics of the MEMS accelerometer's sensitive structure and the complexity of its internal temperature field within the IMU, both its output zero bias and scaling factor drift significantly with temperature. This presents a serious technical challenge: when powered on from a cold state at different temperatures (low temperature, room temperature, and high temperature), the accelerometer's output zero bias varies greatly, making it difficult to meet the stringent requirements of full-temperature-range zero bias in high-precision applications.

[0003] Currently, most common temperature compensation methods employ a single static compensation model, which involves collecting accelerometer output data at different isothermal points and then fitting a zero-bias-temperature function for compensation. However, this method ignores the influence of dynamic effects during temperature changes, resulting in limited compensation for temperature drift in parameters such as the scaling factor. Therefore, the single static compensation method suffers from incomplete compensation and poor performance consistency across the entire temperature range, leading to reduced environmental adaptability of the inertial measurement unit. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, the technical problem to be solved by this invention is: how to provide a method for achieving high-precision and high-stability compensation of MEMS accelerometers with zero bias across the entire temperature range by separating error sources and adopting differentiated compensation strategies for different error sources.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A temperature compensation method for zero bias in a MEMS accelerometer is disclosed, comprising obtaining the scaling factor temperature compensation coefficient and the static zero bias temperature compensation amount of the MEMS accelerometer, respectively; wherein the scaling factor temperature compensation coefficient is obtained by performing dynamic testing on the MEMS accelerometer during a first temperature change process; the static zero bias temperature compensation amount is obtained by performing static testing on the MEMS accelerometer during a second temperature change process; and the real-time output value of the MEMS accelerometer is compensated by combining the scaling factor temperature compensation coefficient and the static zero bias temperature compensation amount.

[0007] As an optimization, the dynamic test is as follows: during the first temperature change process, the MEMS accelerometer is controlled to be in multiple different attitudes in sequence, and the output data under each attitude is collected. The scaling factor temperature compensation coefficient is calculated based on the output data.

[0008] As an optimization, the multiple different poses include pointing to the sky and pointing to the ground in each of the three orthogonal axes.

[0009] As an optimization, the first temperature change process is a process of uniformly increasing the temperature from (-40 to -20)℃ to (50 to 65)℃ at a rate of (1 to 2)℃ / min.

[0010] As an optimization, the static test is as follows: during the second temperature change process, the MEMS accelerometer is kept stationary, its output data is collected, and the static zero bias temperature compensation amount is calculated based on the output data.

[0011] As an optimization, the second temperature change process is a process of uniformly increasing the temperature from (-40 to -20)℃ to (50 to 65)℃ at a rate of (1 to 2)℃ / min.

[0012] As an optimization, the calculation formula for the combined compensation is: ACC = ACC 原始 ×ACC BDWBXS -ACC LP ACC 原始 The raw output value of the MEMS accelerometer, ACC BDWBXS ACC is the scaling factor and temperature compensation coefficient. LP This is the static zero-bias temperature compensation amount.

[0013] As an optimization, the scaling factor calibration coefficient of the MEMS accelerometer is also obtained. The scaling factor calibration coefficient is obtained by maintaining a constant temperature within a range of -45 to 65 °C and calibrating the scaling factor of the MEMS accelerometer using a multi-position calibration method. The scaling factor calibration coefficient, the scaling factor temperature compensation coefficient, and the static zero-bias temperature compensation amount are then used to perform combined compensation on the real-time output value of the MEMS accelerometer. The calculation formula for the combined compensation is: ACC = ACC 原始 ×ACC BDWBXS ×ACC BDBDXS -ACC LP ACC BDBDXS The scaling factor is the calibration coefficient.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) By separating the error sources and adopting differentiated compensation strategies for different error sources, the compensation accuracy is much higher than that of the traditional single static compensation method.

[0016] (2) Improved the performance stability of the inertial measurement unit and the consistency of batch products when operating within the full temperature range;

[0017] (3) This method does not require any changes to the hardware structure and can be implemented only through software algorithm optimization. It is easy to promote and apply on existing products, has low cost, and has high economic value. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments, but merely represent selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The temperature compensation method for zero bias of the MEMS accelerometer in this specific embodiment obtains the scaling factor temperature compensation coefficient and the static zero bias temperature compensation amount of the MEMS accelerometer. The scaling factor temperature compensation coefficient is obtained by performing dynamic testing on the MEMS accelerometer during a first temperature change. The static zero bias temperature compensation amount is obtained by performing static testing on the MEMS accelerometer during a second temperature change. The real-time output value of the MEMS accelerometer is compensated by combining the scaling factor temperature compensation coefficient and the static zero bias temperature compensation amount.

[0020] The dynamic test is as follows: during the first temperature change process, the MEMS accelerometer is controlled to be in multiple different attitudes in sequence, and the output data under each attitude is collected. The scaling factor temperature compensation coefficient is calculated based on the output data.

[0021] The various poses include pointing to the sky and pointing to the ground in each of the three orthogonal axes.

[0022] The first temperature change process is a process of uniformly increasing the temperature from (-40 to -20)℃ to (50 to 65)℃ at a rate of (1 to 2)℃ / min.

[0023] The static test is as follows: during the second temperature change process, the MEMS accelerometer is kept stationary, its output data is collected, and the static zero bias temperature compensation amount is calculated based on the output data.

[0024] The second temperature change process is a process of uniformly increasing the temperature from (-40 to -20)℃ to (50 to 65)℃ at a rate of (1 to 2)℃ / min.

[0025] The formula for calculating the combined compensation is: ACC = ACC 原始 ×ACC BDWBXS -ACC LP ACC原始 The raw output value of the MEMS accelerometer, ACC BDWBXS ACC is the scaling factor and temperature compensation coefficient. LP This is the static zero-bias temperature compensation amount.

[0026] The scaling factor calibration coefficient of the MEMS accelerometer is also obtained. The scaling factor calibration coefficient is obtained by maintaining a constant temperature within a range of -45 to 65 °C and calibrating the scaling factor of the MEMS accelerometer using a multi-position calibration method. The scaling factor calibration coefficient, the scaling factor temperature compensation coefficient, and the static zero-bias temperature compensation amount are then used to perform combined compensation on the real-time output value of the MEMS accelerometer. The calculation formula for the combined compensation is as follows:

[0027] ACC = ACC 原始 ×ACC BDWBXS ×ACC BDBDXS -ACC LP ACC BDBDXS The scaling factor is the calibration coefficient.

[0028] In the specific implementation process, the scaling factor temperature compensation coefficient is determined as follows: The inertial measurement unit is fixed in a triaxial temperature chamber turntable, and the temperature is uniformly increased from a low temperature of -40℃ to +65℃ at a heating rate of 1℃ / min. Simultaneously, the turntable is set to rotate cyclically in the following order: X-axis pointing upwards (hold for 30s), X-axis pointing downwards (hold for 30s), Y-axis pointing upwards (hold for 30s), Y-axis pointing downwards (hold for 30s), Z-axis pointing upwards (hold for 30s), Z-axis pointing downwards (hold for 30s), with smooth 1-second output data from the accelerometer collected at a frequency of 1Hz throughout the process. At each temperature point, based on the data from the upward and downward pointing positions for each axis, the real-time scaling factor at that temperature is calculated cyclically. A specific temperature (23℃) is selected as the reference point, a third-order fit is performed, and the temperature compensation coefficient is written into the program.

[0029] Static zero-bias temperature compensation: The inertial measurement unit was placed statically in the platform temperature chamber without any rotation. The temperature chamber was set to uniformly heat from -40℃ to +65℃ at a rate of 1℃ / min. Accelerometer data was collected smoothly in 1-second intervals at a frequency of 1Hz throughout the process. A reference point of 23℃ was selected, and a third-order fit was performed. The static zero-bias was then written into the program.

[0030] Scale factor calibration coefficients: The inertial measurement unit was fixed on a three-axis turntable inside a temperature chamber and powered on until thermal stability was achieved at a constant temperature of 23°C. The scale factor of the MEMS accelerometer was calibrated using a six-position method, and the resulting scale factor calibration coefficients were written into the program.

[0031] During actual operation, the inertial measurement unit (IMU) collects data from its internal temperature sensor in real time and reads the raw output value (ACC) of the accelerometer. 原始 The microprocessor calls the compensation parameters and performs real-time calculations according to the following formula:

[0032] ACC = ACC 原始 ×ACC BDWBXS ×ACC BDBDXS -ACC LP Finally, the compensated acceleration value ACC is output for navigation calculation. Testing of the inertial measurement unit product using the compensation method of this invention showed that the range of zero bias variation of the MEMS accelerometer during high and low temperature operation decreased from 1.5mg before compensation to below 0.3mg, demonstrating a significant performance improvement and fully meeting the relevant technical requirements.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described with reference to preferred embodiments, those skilled in the art should understand that various changes in form and detail can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A temperature compensation method for zero bias in a MEMS accelerometer, characterized in that: The scaling factor temperature compensation coefficient and static zero bias temperature compensation amount of the MEMS accelerometer are obtained respectively. The scaling factor temperature compensation coefficient is obtained by dynamic testing of the MEMS accelerometer during the first temperature change process; the static zero bias temperature compensation amount is obtained by static testing of the MEMS accelerometer during the second temperature change process; and the real-time output value of the MEMS accelerometer is compensated by combination based on the scaling factor temperature compensation coefficient and the static zero bias temperature compensation amount.

2. The temperature compensation method for zero bias of MEMS accelerometer according to claim 1, characterized in that: The dynamic test is as follows: during the first temperature change process, the MEMS accelerometer is controlled to be in multiple different attitudes in sequence, and the output data under each attitude is collected. The scaling factor temperature compensation coefficient is calculated based on the output data.

3. The temperature compensation method for zero bias of MEMS accelerometer according to claim 2, characterized in that: The various poses include pointing to the sky and pointing to the ground in each of the three orthogonal axes.

4. The temperature compensation method for zero bias of a MEMS accelerometer according to claim 2 or 3, characterized in that: The first temperature change process is a process of uniformly increasing the temperature from (-40 to -20)℃ to (50 to 65)℃ at a rate of (1 to 2)℃ / min.

5. The temperature compensation method for zero bias of MEMS accelerometer according to claim 1, characterized in that: The static test is as follows: during the second temperature change process, the MEMS accelerometer is kept stationary, its output data is collected, and the static zero bias temperature compensation amount is calculated based on the output data.

6. The temperature compensation method for zero bias of MEMS accelerometer according to claim 5, characterized in that: The second temperature change process is a process of uniformly increasing the temperature from (-40 to -20)℃ to (50 to 65)℃ at a rate of (1 to 2)℃ / min.

7. The temperature compensation method for zero bias of a MEMS accelerometer according to claim 1, characterized in that: The formula for calculating the combined compensation is: ACC = ACC 原始 ×ACC BDWBXS -ACC LP ACC 原始 The raw output value of the MEMS accelerometer, ACC BDWBXS ACC is the scaling factor and temperature compensation coefficient. LP This is the static zero-bias temperature compensation amount.

8. The temperature compensation method for zero bias of a MEMS accelerometer according to claim 7, characterized in that: The scaling factor calibration coefficient of the MEMS accelerometer is also obtained. The scaling factor calibration coefficient is obtained by maintaining a constant temperature within a range of -45 to 65 °C and calibrating the scaling factor of the MEMS accelerometer using a multi-position calibration method. The scaling factor calibration coefficient, the scaling factor temperature compensation coefficient, and the static zero-bias temperature compensation amount are then used to perform combined compensation on the real-time output value of the MEMS accelerometer. The calculation formula for the combined compensation is as follows: ACC = ACC 原始 ×ACC BDWBXS ×ACC BDBDXS -ACC LP ACC BDBDXS The scaling factor is the calibration coefficient.