CN103558415B

CN103558415B - With the mems accelerometer of temperature-compensating

Info

Publication number: CN103558415B
Application number: CN201310585144.3A
Authority: CN
Inventors: 王晓臣; 鞠莉娜; 张斌; 王甫; 高玉霞
Original assignee: China North Industries Group Corp No 214 Research Institute Suzhou R&D Center
Current assignee: No 214 Institute of China North Industries Group Corp
Priority date: 2013-11-19
Filing date: 2013-11-19
Publication date: 2016-05-11
Anticipated expiration: 2033-11-19
Also published as: CN103558415A

Abstract

The present invention relates to a kind of mems accelerometer with temperature-compensating, comprise acceleration transducer, temperature sensor, temperature-compensated chip, acceleration transducer and temperature sensor are connected with temperature-compensated chip. The temperature compensation that temperature-compensated chip adopts is: (1) measures zero partially and one group of output valve of scale factor fit to fitting surface and obtain a series of fitting coefficients and be arranged in coefficient matrix under multiple temperature spots; (2) the output signal modeling of the output signal of degree of will speed up sensor and temperature sensor be expressed as model matrix; (3) coefficient matrix and model matrix are done to dot product and obtain the output formula of acceleration transducer after temperature-compensating; (4) fitting coefficient being write to temperature-compensated chip with output formula calculates. The present invention by curved surface 3 D Quasi and and calculate after compensate, effectively reduced the impact on system of error that accelerometer produces in assembling and installation process.

Description

MEMS accelerometer with temperature compensation

Technical Field

The invention relates to an MEMS accelerometer, in particular to an MEMS accelerometer with a temperature compensation function.

Background

An MEMS (micro electro-mechanical system) accelerometer is one of important sensors in a micro inertial navigation system, and the navigation precision of the inertial navigation system is directly influenced by the advantages and disadvantages of the performance of the MEMS accelerometer. The measurement output error of the MEMS accelerometer mainly comes from aspects such as a manufacturing process, an installation method, an external environment and the like, wherein the influence of the environmental temperature on the measurement output of the MEMS accelerometer is particularly prominent, and the measurement output error also becomes a key problem in the engineering application of the micro accelerometer.

Currently, local temperature control and software methods are commonly used to achieve temperature compensation. Local temperature control usually needs to change the internal structure and materials of the accelerometer or increase a temperature control system, and the realization is complex, so that more software schemes are adopted in engineering for compensation, and the stability of acceleration measurement can be improved by 5-20 times after compensation. The software compensation scheme is based on the premise of obtaining an accelerometer temperature model, and usually a special temperature control box or complex test equipment needs to be designed for carrying out model identification experiments, for example, an independent high-precision temperature control box is designed, and the temperature model of the accelerometer is identified by means of an indexing table; or a temperature model of an accelerometer is identified by adopting a temperature control rotary table and an indexing table, and the like.

For example, the static model of an accelerometer is shown in equation (1):

y=K₀+K₁a_i+K₂a_i ²+K₃a_ia₀（1）

wherein, y: an accelerometer output (V); k₀: a null output (V) of the accelerometer; k₁: scale factor of the accelerometer (V/gn); k₂: second order nonlinear coefficient (V/g)_n ²）；K₃Cross coupling coefficient (V/g)_n ²）；a_i: acceleration (g) parallel to the accelerometer input axis_n）；a₀: lateral acceleration (g)_n). For the accelerometer used in the test, since K₂And K₃Is generally 10^－4In order of magnitude, the non-linear error caused by the accelerometer is less than 0.5%, so that the non-linear term and the cross interference term in the accelerometer output can be ignored, and the real acceleration value can be obtained according to the accelerometer measurement output by adopting the formula (2):

a_i=（y－K₀）/K₁（2）

in the traditional temperature compensation method, the essence of temperature modeling of the accelerometer is to determine the zero position output K of the accelerometer₀And a scale factor K₁And temperature. If K of the accelerometer at different temperatures is obtained₀And K₁Then, a temperature model can be obtained by a first-order curve fitting method, as shown in formula (3):

K₀=K₀₀+K₀₁TK₁=K₁₀+K₁₁T（3）

wherein,t is the ambient temperature, K₀₀、K₀₁、K₁₀、K₁₁Is the undetermined coefficient.

As can be seen from equation (3), the conventional temperature compensation method compensates for the zero position and scale factor of the accelerometer separately.

Therefore, the traditional accelerometer has high requirements on the assembly and installation of the accelerometer during temperature compensation, and the zero position and the scale factor of the accelerometer are separately compensated.

Disclosure of Invention

It is an object of the present invention to provide a MEMS accelerometer with temperature compensation that does not require separate consideration of the zero position and the scale factor.

In order to achieve the purpose, the invention adopts the technical scheme that:

the MEMS accelerometer with the temperature compensation comprises an MEMS acceleration sensor, a temperature sensor and a temperature compensation chip, wherein the output end of the MEMS acceleration sensor and the output end of the temperature sensor are respectively connected with the input end of the temperature compensation chip through an A/D channel, and the output end of the temperature compensation chip is the output end of the MEMS accelerometer with the temperature compensation;

the temperature compensation method adopted by the temperature compensation chip comprises the following steps: (1) measuring the zero offset and the output value of the scale factor of the MEMS acceleration sensor under a plurality of temperature points through high-low temperature circulation to obtain a group of data, fitting the group of data to obtain a fitted surface of the data, obtaining a series of fitting coefficients required by meeting the fitting order through the fitted surface, and arranging the series of fitting coefficients into a coefficient matrix; (2) the output signal N of the MEMS acceleration sensor is measured_RAnd the output signal T of the temperature sensor is modeled asAnd expressed as a model matrix, where n is the fitting order; (3) performing dot multiplication on the coefficient matrix and the model matrix to obtain an output formula of the MEMS acceleration sensor after temperature compensation in a full temperature range; (4) writing the series of fitting coefficients and the output formula of the MEMS acceleration sensor in the full temperature range after temperature compensation into the temperature compensation chip, and outputting a signal N of the MEMS acceleration sensor_RAnd the output signal T of the temperature sensor is calculated by a formula to obtain the acceleration value output by the MEMS accelerometer with temperature compensation.

Preferably, the fitted surface is obtained by least square fitting the set of data.

Preferably, the fitting order is 5 th order.

Preferably, the series of fitting coefficients is 21, each of which is C₀-C₂₀Arranged as a coefficient matrix of

(\begin{matrix} C_{0} & C_{2} & C_{5} & C_{9} & C_{14} & C_{20} \\ C_{1} & C_{4} & C_{8} & C_{13} & C_{19} & 0 \\ C_{3} & C_{7} & C_{12} & C_{18} & 0 & 0 \\ C_{6} & C_{11} & C_{17} & 0 & 0 & 0 \\ C_{10} & C_{16} & 0 & 0 & 0 & 0 \\ C_{15} & 0 & 0 & 0 & 0 & 0 \end{matrix});

The model matrix is

(\begin{matrix} 1 & T & T^{2} & T^{3} & T^{4} & T^{5} \\ N_{R} & N_{R} T & N_{R} T^{2} & N_{R} T^{3} & N_{R} T^{4} & 0 \\ N_{R}^{2} & N_{R}^{2} T & N_{R}^{2} T^{2} & N_{R}^{2} T^{3} & 0 & 0 \\ N_{R}^{3} & N_{R}^{3} T & N_{R}^{3} T^{2} & 0 & 0 & 0 \\ N_{R}^{4} & N_{R}^{4} T & 0 & 0 & 0 & 0 \\ N_{R}^{5} & 0 & 0 & 0 & 0 & 0 \end{matrix});

The output formula of the MEMS acceleration sensor in the full temperature range after temperature compensation is as follows

\begin{matrix} g (T) = C_{0} + C_{1} N_{R} + C_{2} T + C_{3} N_{R}^{2} + C_{4} N_{R} T + \\ C_{5} T^{2} + C_{6} N_{R}^{3} + C_{7} N_{R}^{2} T + C_{8} N_{R} T^{2} + \\ C_{9} T^{3} + C_{10} N_{R}^{4} + C_{11} N_{R}^{3} T + C_{12} N_{R}^{2} T^{2} + \\ C_{13} N_{R} T^{3} + C_{14} T^{3} + C_{15} N_{R}^{5} + C_{16} N_{R}^{4} T + \\ C_{17} N_{R}^{3} T^{2} + C_{18} N_{R}^{2} T^{3} + C_{19} N_{R} T^{4} + C_{20} T^{5} \end{matrix} .

Preferably, the MEMS acceleration sensor and the temperature sensor are located in the same thermal field.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the MEMS accelerometer does not separately consider the zero position and the scale factor of the MEMS accelerometer during compensation, but compensates the MEMS accelerometer after three-dimensional fitting and calculation of a curved surface, and effectively reduces the influence of errors generated by the accelerometer in the assembling and installing processes on a system.

Drawings

FIG. 1 is a schematic block circuit diagram of a MEMS accelerometer with temperature compensation according to the present invention.

FIG. 2 is a schematic diagram of a curved surface fitted by the MEMS accelerometer with temperature compensation in the compensation method.

FIG. 3 is a data graph of the output of the MEMS accelerometer at full temperature of-1 g- +1g before compensation.

FIG. 4 is a data graph of the outputs of the MEMS accelerometer at full temperature of-30 g- +30g before compensation.

FIG. 5 is a graph showing the relationship between the outputs of the compensated MEMS accelerometer of-1 g- +1g at full temperature and the temperature.

FIG. 6 is a graph of the relationship between the compensated graph of the voltage value converted from the g value outputted by the MEMS accelerometer at the full temperature and the temperature.

Detailed Description

The invention will be further described with reference to examples of embodiments shown in the drawings to which the invention is attached.

The first embodiment is as follows: see fig. 1 for a description. A MEMS accelerometer with temperature compensation comprises a MEMS acceleration sensor, a temperature sensor and a temperature compensation chip. The output end of the MEMS acceleration sensor and the output end of the temperature sensor are respectively connected with the input end of the temperature compensation chip through an A/D channel, and the output end of the temperature compensation chip is the output end of the MEMS accelerometer with temperature compensation. The MEMS acceleration sensor adopts a high-precision temperature sensor LM20, processes and temperature compensates the acquired acceleration data in a temperature compensation chip, and outputs a compensation result. Meanwhile, for convenience of calibration and guarantee that the MEMS acceleration sensor and the temperature sensor are located in a heat field, for example, the temperature sensor and the MEMS acceleration sensor are bonded on a PCB and then assembled in an aluminum alloy tube shell. The MEMS accelerometer with temperature compensation has the main performance indexes that: the working voltage is 5V; the working current is 10 mA; the measuring range is variable, and the maximum measuring range is +/-30 g.

The temperature compensation method adopted by the temperature compensation chip is as follows:

(1) in the experiment, a group of data is obtained by measuring the zero offset and the scale factor output value of the MEMS acceleration sensor under a plurality of temperature points through high and low temperature circulation, and the group of data is fitted by using a least square method to obtain a fitted surface of the group of data. And obtaining a series of fitting coefficients required by meeting the fitting order through the fitting surface, and arranging the series of fitting coefficients into a coefficient matrix.

Taking 5 th order fitting as an example, a series of fitting coefficients are 21, each of which is C₀-C₂₀Arranged as a coefficient matrix

(\begin{matrix} C_{0} & C_{2} & C_{5} & C_{9} & C_{14} & C_{20} \\ C_{1} & C_{4} & C_{8} & C_{13} & C_{19} & 0 \\ C_{3} & C_{7} & C_{12} & C_{18} & 0 & 0 \\ C_{6} & C_{11} & C_{17} & 0 & 0 & 0 \\ C_{10} & C_{16} & 0 & 0 & 0 & 0 \\ C_{15} & 0 & 0 & 0 & 0 & 0 \end{matrix}) - - - (4)

It can be seen that in the coefficient matrix, the fitting coefficients are arranged in an upper triangle divided by a sub-diagonal of the matrix.

(2) Output signal N of MEMS acceleration sensor_RAnd the output signal T of the temperature sensor is modeled asAnd expressed as a model matrix, where n is the fitting order.

Again taking the 5 th order fit as an example, the model matrix is constructed as

(\begin{matrix} 1 & T & T^{2} & T^{3} & T^{4} & T^{5} \\ N_{R} & N_{R} T & N_{R} T^{2} & N_{R} T^{3} & N_{R} T^{4} & 0 \\ N_{R}^{2} & N_{R}^{2} T & N_{R}^{2} T^{2} & N_{R}^{2} T^{3} & 0 & 0 \\ N_{R}^{3} & N_{R}^{3} T & N_{R}^{3} T^{2} & 0 & 0 & 0 \\ N_{R}^{4} & N_{R}^{4} T & 0 & 0 & 0 & 0 \\ N_{R}^{5} & 0 & 0 & 0 & 0 & 0 \end{matrix}) - - - (5)

The model matrix has a structure corresponding to the coefficient matrix, in which the elements are also arranged in an upper triangle divided by a sub-diagonal of the matrix.

(3) Performing dot multiplication on the coefficient matrix type (4) and the model matrix type (5) to obtain an output formula of the MEMS acceleration sensor in the full temperature range after temperature compensation;

\begin{matrix} g (T) = C_{0} + C_{1} N_{R} + C_{2} T + C_{3} N_{R}^{2} + C_{4} N_{R} T + \\ C_{5} T^{2} + C_{6} N_{R}^{3} + C_{7} N_{R}^{2} T + C_{8} N_{R} T^{2} + \\ C_{9} T^{3} + C_{10} N_{R}^{4} + C_{11} N_{R}^{3} T + C_{12} N_{R}^{2} T^{2} + \\ C_{13} N_{R} T^{3} + C_{14} T^{3} + C_{15} N_{R}^{5} + C_{16} N_{R}^{4} T + \\ C_{17} N_{R}^{3} T^{2} + C_{18} N_{R}^{2} T^{3} + C_{19} N_{R} T^{4} + C_{20} T^{5} \end{matrix} - - - (6)

the surface to which it is fitted is shown schematically in FIG. 2, where the X-axis is the output signal of the accelerometer (N)_R) The Y-axis is the output of the temperature sensor (T), and the Z-axis is the actual measured acceleration value (g). When fitting the data collected over the full range of the accelerometer over the full temperature range, theoretically any acceleration value of the accelerometer at any temperature point is included in the simulationAnd in the curved surface of the sum, the real acceleration value of the accelerometer at any temperature point can be obtained through the calculation of the formula (6).

(4) Writing a series of fitting coefficients and an output formula of the MEMS acceleration sensor in the full temperature range after temperature compensation into a temperature compensation chip, and outputting a signal N of the MEMS acceleration sensor_RAnd the output signal T of the temperature sensor is calculated by a formula to obtain the acceleration value output by the MEMS accelerometer with temperature compensation.

For the MEMS accelerometer which is not subjected to temperature compensation and assembled, an NI6281 data acquisition card is adopted to acquire data of-1 g to +1g at-40 ℃, 10 ℃, 25 ℃, 55 ℃ and 85 ℃, the acquired data are shown in the attached figure 3, wherein the abscissa is time (S), the ordinate is voltage value (V), the curve of the series 2 is the output of a temperature sensor, and the temperature sensor is a negative temperature coefficient, so that the curve of the series 2 represents the output of-40 ℃, 10 ℃, 25 ℃, 55 ℃ and 85 ℃ from the left to the right 5 steps, and the curve of the series 1 represents the output of-1 g to +1g of the accelerometer at-40 ℃, 10 ℃, 25 ℃, 55 ℃ and 85 ℃ from the left to the right 5 steps. It can be seen from the figure that the output drift of the accelerometer is still relatively large under the low temperature condition, because there is no device for testing the output of the accelerometer in the full-temperature full-range temporarily, the output of the accelerometer in the full-temperature full-range is only derived by the zero position and the scale factor of different temperature points, and the derived data is graphically shown in fig. 4.

And performing least square fitting by software to obtain a compensated fitting coefficient of

[\begin{matrix} - 203.222 & 845.874 & - 1029.087 & 615.967 & - 183.663 & 21.671 \\ 12.289 & - 105.471 & 100.329 & - 40.267 & 5.93 & 0 \\ 0.736 & - 0.645 & 0.319 & - 0.061 & 0 & 0 \\ - 0.128 & 0.025 & - 0.003 & 0 & 0 & 0 \\ 0.015 & 0 & 0 & 0 & 0 & 0 \\ - 0.001 & 0 & 0 & 0 & 0 & 0 \end{matrix}]

The coefficient is written into a temperature compensation chip, and the calculated acceleration value is finally output in the temperature compensation chip through operation, and the output result is shown in the attached figures 5 and 6.

As can be seen from a comparison of FIGS. 6 and 3, the zero drift of the accelerometer is approximately 500mV, which translates to approximately 10g for g at-40 ℃ before warm-up, and approximately 50mV for voltage after warm-up, which translates to approximately 1g drift, thus reducing the temperature drift by one order of magnitude.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A MEMS accelerometer with temperature compensation comprises a MEMS acceleration sensor, and is characterized in that: the output end of the MEMS acceleration sensor and the output end of the temperature sensor are respectively connected with the input end of the temperature compensation chip through an A/D channel, and the output end of the temperature compensation chip is the output end of the MEMS accelerometer with temperature compensation; the MEMS acceleration sensor and the temperature sensor are positioned in the same heat field, and the temperature sensor and the MEMS acceleration sensor are assembled in an aluminum alloy tube shell after being adhered to a PCB (printed Circuit Board);

2. The temperature-compensated MEMS accelerometer of claim 1, wherein: and fitting the group of data by a least square method to obtain a fitted surface of the data.

3. The temperature-compensated MEMS accelerometer of claim 1, wherein: the fitting order is 5 orders.

4. The temperature-compensated MEMS accelerometer of claim 3, wherein: the series of fitting coefficients are 21 and are respectively C₀-C₂₀Arranged as a coefficient matrix of

(\begin{matrix} C_{0} & C_{2} & C_{5} & C_{9} & C_{14} & C_{20} \\ C_{1} & C_{4} & C_{8} & C_{13} & C_{19} & 0 \\ C_{3} & C_{7} & C_{12} & C_{18} & 0 & 0 \\ C_{6} & C_{11} & C_{17} & 0 & 0 & 0 \\ C_{10} & C_{16} & 0 & 0 & 0 & 0 \\ C_{15} & 0 & 0 & 0 & 0 & 0 \end{matrix});

The model matrix is

(\begin{matrix} 1 & T & T^{2} & T^{3} & T^{4} & T^{5} \\ N_{R} & N_{R} T & N_{R} T^{2} & N_{R} T^{3} & N_{R} T^{4} & 0 \\ N_{R}^{2} & N_{R}^{2} T & N_{R}^{2} T^{2} & N_{R}^{2} T^{3} & 0 & 0 \\ N_{R}^{3} & N_{R}^{3} T & N_{R}^{3} T^{2} & 0 & 0 & 0 \\ N_{R}^{4} & N_{R}^{4} T & 0 & 0 & 0 & 0 \\ N_{R}^{5} & 0 & 0 & 0 & 0 & 0 \end{matrix});

\begin{matrix} g (T) = C_{0} + C_{1} N_{R} + C_{2} T + C_{3} N_{R}^{2} + C_{4} N_{R} T + \\ C_{5} T^{2} + C_{6} N_{R}^{3} + C_{7} N_{R}^{2} T + C_{8} N_{R} T^{2} + \\ C_{9} T^{3} + C_{10} N_{R}^{4} + C_{11} N_{R}^{3} T + C_{12} N_{R}^{2} T^{2} + \\ C_{13} N_{R} T^{3} + C_{14} T^{3} + C_{15} N_{R}^{5} + C_{16} N_{R}^{4} T + \\ C_{17} N_{R}^{3} T^{2} + C_{18} N_{R}^{2} T^{3} + C_{19} N_{R} T^{4} + C_{20} T^{5} \end{matrix} .