CN101893722B - Giant magneto-resistance sensor-based geomagnetic roll angle measurement system and method - Google Patents

Abstract

The invention relates to a geomagnetic roll angle measurement system and method based on a giant magnetoresistance sensor. The system is mainly composed of a geomagnetic measurement module, a pitch angle measurement module, a signal conditioning module and a microprocessor. Among them, the geomagnetic measurement module uses the giant magnetoresistance sensor to measure the geomagnetism of the X-axis, Y-axis and Z-axis; the pitch angle measurement module uses the dual-axis acceleration sensor to measure the X-axis pitch angle; the signal conditioning module performs the amplification of the analog signal of the giant magnetoresistance sensor , offset zeroing, analog-to-digital conversion; the microprocessor performs multi-sensor fusion processing on the geomagnetic and pitch information to obtain the geomagnetic roll angle. In this method, an amplifier bias zeroing circuit is designed to reduce the zero output of the giant magnetoresistive sensor and improve the accuracy of roll angle measurement; a dual-axis acceleration sensor is used to solve the problem of multi-value in the pitch angle measurement of the single-axis acceleration sensor The problem is to realize the uniqueness of the pitch angle and the measurement of the roll angle.

Description

A system and method for measuring geomagnetic roll angle based on giant magnetoresistive sensor

technical field

The invention relates to a geomagnetic sensor system and method including an amplifier bias zeroing circuit, in particular to a geomagnetic roll angle measurement system and method based on a giant magnetoresistance sensor. It belongs to the field of sensor technology.

Background technique

With the continuous expansion of the field of human activities, in the fields of aviation, aerospace, navigation, stratum exploration, deep sea exploration and other fields, attitude angle measurement technology has become necessary for most engineering fields. At present, the methods used for attitude angle measurement mainly include: radio navigation, gyroscope, geomagnetic positioning, solar azimuth positioning, and stellar astronomical positioning. Due to the limitation of radio signals by terrain, the accuracy of gyroscope measurement is low, the technology of high-precision gyroscope is complex and expensive, and the positioning of celestial bodies is limited by the weather. The attitude angle measurement based on the geomagnetic sensor system can solve the above shortcomings very well. Generally speaking, these geomagnetic sensors are required to have high sensitivity, high resolution, small size, and low power consumption.

Common geomagnetic sensors mainly include the following:

1. Permanent magnet compass, the disadvantage of this kind of geomagnetic field measuring device is that the permanent magnet has limited magnetic moment and low resolution, it is difficult to realize miniaturization, the structure is complex, and the bearing capacity is poor.

2. Fluxgate compass, as described in patent 200610101789.5 CN1971309 "Geomagnetic Sensor and Its Azimuth Calculation Method". The disadvantages of this type of fluxgate geomagnetic sensor are relatively large structure, slow dynamic response, and complicated calculation.

3. Magnetoresistive sensors, such as patent 200580035519.2 CN101044412 describes "method and equipment for measuring magnetic field using magnetoresistive sensors". It uses the principle that the resistance of the nickel-iron alloy is only sensitive to a magnetic field in a certain direction. Since the size of the resistor can be made very small and there are no moving parts, the attitude angle measuring instrument formed by the magnetoresistive element is small in size and good in reliability. Its disadvantage is that it is sensitive to temperature, and it is necessary to eliminate the influence of external temperature changes; in addition, the change rate of magnetoresistance is low and the sensitivity is low, so the improvement of measurement accuracy will be greatly limited.

Therefore, if there is no accurate geomagnetic field measurement sensor, plus the pitch angle with errors, the roll angle cannot be well compensated, so that there will be errors in the calculation of the roll angle. Aiming at the above-mentioned problems of large volume and low sensitivity, the present invention provides a geomagnetic roll angle measurement system and method based on a giant magnetoresistive sensor, which is small in size, low in cost, high in precision, and has good use value.

Contents of the invention

The object of the present invention is to address the defects of the prior art, to provide a system and method for measuring the geomagnetic roll angle based on the giant magnetoresistance sensor, so that the measurement of the geomagnetic field by the giant magnetoresistance sensor is more accurate and reliable, and the uniqueness of the pitch angle is realized. , and use the pitch angle and geomagnetic field components to solve the roll angle.

For achieving above-mentioned purpose of the present invention, design of the present invention is:

When the giant magnetoresistance sensor measures the geomagnetic field, due to the bias of the bridge of the giant magnetoresistance sensor, that is, when the external magnetic field is zero, the sensor output is not zero, and the signal range entering the A/D converter is reduced, reducing The sampling resolution of the analog-to-digital converter is reduced, which also reduces the accuracy of the measurement of the geomagnetic field and roll angle.

When the acceleration sensor measures the pitch angle, since the relationship between the output of the acceleration sensor and the measured pitch angle is Sinθ, obviously, there will be a multi-value problem when the single-axis acceleration sensor measures the pitch angle, so the calculated roll angle is not accurate. only.

According to above-mentioned inventive concept, the present invention adopts following technical scheme:

A kind of geomagnetic roll angle measurement system based on giant magnetoresistive sensor is made up of geomagnetic measurement module, pitch angle measurement module, signal conditioning module, microprocessor, it is characterized in that described geomagnetic measurement module comprises two orthogonal X axes, Y-axis and Z-axis giant magnetoresistive sensors; the pitch angle measurement module includes mutually perpendicular X-axis and Z-axis biaxial acceleration sensors; the signal conditioning module includes a bias zeroing circuit through an amplifier, an instrument amplifier, connected An A/D converter; the geomagnetic measurement module is connected to the microprocessor via a signal conditioning module, and the elevation angle measurement module is connected to the microprocessor.

The geomagnetic measurement module adopts a three-axis giant magnetoresistive sensor AAH002-02; the pitch angle measurement module adopts a biaxial acceleration sensor ADXL202; the instrumentation amplifier in the signal conditioning module adopts INA118, and the A/D converter is a microprocessor automatic belt; the microprocessor adopts Atmega128L; the signal conditioning module amplifies the analog signal measured by the giant magnetoresistive sensor of the geomagnetic measurement module, offsets zero adjustment and analog-to-digital conversion; the microprocessor performs geomagnetic and pitch information The geomagnetic roll angle is obtained after multi-sensor fusion processing.

The signal conditioning module is to amplify the analog signal of the giant magnetoresistive sensor through the amplifier bias zeroing circuit, and then convert it into a digital signal through the A/D converter, and finally send it to the microprocessor; The zero circuit is: a digital potentiometer R _g is connected to one input terminal of the instrumentation amplifier, and by controlling the digital potentiometer R _g , the adjustment of the power supply voltage of the bridge is realized to reduce the zero output of the giant magnetoresistive sensor and improve The sampling resolution of the analog-to-digital converter is improved, thereby improving the accuracy of the geomagnetic field measurement.

A method for measuring geomagnetic roll angle based on a giant magnetoresistive sensor, using the above-mentioned system to measure, is characterized in that the specific steps are as follows:

(1) Measure the geomagnetic roll angle parameter based on the giant magnetoresistive sensor;

(2) Collect the measured values of the giant magnetoresistive sensors of each axis, and calculate the magnetic field components H″’ _X , H″’ _Y , H″’ _Z on the X-axis, Y-axis and Z-axis according to the measured values;

(3) Collect the output value of the biaxial acceleration sensor, use the output value to calculate the pitch angle, and realize the uniqueness of the pitch angle θ:

进行方位角为零的横滚角计算；(4) Using the X-axis, Y-axis and Z-axis geomagnetic field components H″′ _X , H″′ _Y and H″′ _Z and the pitch angle θ, through the formula

roll angle with zero azimuth calculate;

(5) Output roll angle

In the above step (2), the AAH002-02 sensor uses the change of the magnetic field to cause the change of the resistance value, and the change of the resistance causes the change of the output of the Wheatstone bridge; use the following formula ΔV _out = KSHV _b to calculate the X-axis and Y-axis respectively And the magnetic field components on the Z axis H″′ _X , H″′ _Y , H″′ _Z . In the formula, ΔV _out is the output of AAH002-02, K is the magnification of INA118, S is the sensitivity of AAH002-02, and V _b is the excitation voltage .

In described step (3), the concrete steps that realize pitch angle uniqueness are as follows:

According to the principle of uniaxial acceleration measurement, the pitch angle calculated by the equation gSinθ=Ax has multi-value problems, and a unique measurement value cannot be obtained. The present invention utilizes the dual-axis acceleration sensor ADXL202 to provide a method for judging the quadrant of the pitch angle: judge the quadrant of the pitch angle according to the positive or negative of the X-axis acceleration sensor measurement value Ax and the Z-axis measurement value Az. Substitute the measured value Ax of the X-axis acceleration sensor into the equation θ=arcSin(Ax/g) to calculate the pitch angle. When Ax is greater than 0 and Az is greater than 0, then the θ is the pitch angle; when Ax is greater than 0 and Az is less than 0 , then 180°-θ is the pitch angle; when Ax is less than 0 and Az is less than 0, then 180°+|θ| is the pitch angle; when Ax is less than 0 and Az is greater than 0; then 360°-|θ| is the pitch horn.

Compared with the prior art, the present invention has the following obvious outstanding substantive features and remarkable advantages:

(1) The change rate of giant magnetoresistance is high, the sensitivity is high, and the accuracy of measuring the earth's magnetic field by using giant magnetoresistance sensor is high;

(2) The amplifier bias zeroing circuit is used to reduce the zero output of the giant magnetoresistive sensor and improve the measurement accuracy of the geomagnetic field;

(3) Suitable for the measurement of low magnetic field;

(4) The hardware design circuit is simple, and the measuring device is small in size;

(5) The only pitch angle can be obtained by using the quadrant discrimination method, which improves the measurement accuracy of the roll angle;

(6) Low cost and low power consumption.

Description of drawings

Figure 1 is a structural block diagram of a geomagnetic roll angle measurement system based on a giant magnetoresistive sensor.

Fig. 2 is a circuit structure diagram of a signal conditioning module designed in the geomagnetic roll angle measuring system of Fig. 1 .

Fig. 3 is a flowchart of a method for calculating roll angle.

Fig. 4 is a flow chart of measuring the earth's magnetic field in the calculation method of the roll angle in Fig. 3 .

Fig. 5 is a flow chart of quadrant discrimination for determining the uniqueness of the pitch angle in the calculation method of the roll angle in Fig. 3 .

Detailed ways

Preferred embodiments of the present invention are described as follows in conjunction with the accompanying drawings:

Embodiment 1: Referring to FIG. 1 , the geomagnetic roll angle measurement system of the giant magnetoresistive sensor is composed of a geomagnetic measurement module 1 , a pitch angle measurement module 2 , a signal conditioning module 3 and a microprocessor 4 .

The geomagnetic measurement module 1 includes a 3-axis giant magnetoresistive sensor AAH002-02 with mutually orthogonal X-axis, Y-axis and Z-axis. AAH002-02 outputs the voltage value corresponding to the external geomagnetic field, therefore, the corresponding geomagnetic field component is obtained through the output value of each axis sensor.

The pitch angle measurement module 2 includes an acceleration sensor ADXL202 with X-axis and Z-axis perpendicular to each other. ADXL202 outputs the acceleration corresponding to the inclination of the main body of the geomagnetic sensor system. There is a relationship between them gSinθ=Ax and gCosθ=Az. Therefore, the pitch angle can be measured through the dual-axis acceleration sensor to achieve the uniqueness of the pitch angle.

Signal conditioning module 3 includes instrumentation amplifier INA118, A/D converter and amplifier bias zeroing circuit. The output signal of the giant magnetoresistive sensor AAH002-02 is amplified by the instrument amplifier INA118, and then enters the A/D converter to convert it into a digital signal that can be processed by the microprocessor Atmega128L.

The microprocessor Atmega128L 4 performs multi-sensor fusion processing on the geomagnetic and pitch information to obtain the geomagnetic roll angle.

Embodiment 2: This embodiment is the same as Embodiment 1, and the special features are as follows: Refer to the circuit structure diagram of signal conditioning module 3 in the geomagnetic roll angle measurement system described in Fig. 2, the analog signal of giant magnetoresistance sensor AAH002-02 is bias The zero-adjustment circuit and the instrumentation amplifier INA118 amplify, and then convert it into a digital signal through the A/D converter, and finally send it to the microprocessor Atmega128L. The amplifier bias zeroing circuit consists of a digital potentiometer R _g and two fixed resistors R ₂ . When the geomagnetic field is parallel to the sensitive axis of the giant magnetoresistance sensor, the giant magnetoresistance sensor has a bias voltage output. At this time, by adjusting the resistance value of the digital potentiometer R _g , a voltage with opposite polarity is added to the instrument amplifier to generate a The opposite DC voltage strength cancels the bias, which is half the supply voltage minus the bridge bias voltage.

Embodiment three: referring to Fig. 3, Fig. 4, Fig. 5, the method for measuring the geomagnetic roll angle based on the giant magnetoresistive sensor, the specific steps are as follows:

(1) As shown in process 1 of Figure 3, measure the parameters of the geomagnetic roll angle based on the giant magnetoresistive sensor.

(2) Process 2 as shown in Figure 3, collect the measured values of the giant magnetoresistive sensors of each axis, turn to the process in Figure 4 according to the measured values, and calculate the magnetic field components H″’ _X , H″’ _Y on the X-axis, Y-axis and Z-axis , H″′ _Z .

Process 1 as shown in Figure 4, system initialization, including INA118 magnification K, AAH002-02 sensitivity S, excitation voltage V _b .

As shown in process 2 of Figure 4, the output values ΔV _out of the giant magnetoresistive sensor AAH002-02 on the X-axis, Y-axis and Z-axis are collected respectively.

As shown in Flowchart 3 of Figure 4, ΔV _out , K, S and V _b are brought into the equation ΔV _out =KSHV _b to calculate the geomagnetic field components H″′ _X , H″′ _Y , and H″′ _Z .

(3) As shown in process 3 of Figure 3, the output value of the biaxial acceleration sensor is collected, and the output value is used to go to the process of Figure 5 to calculate the pitch angle and realize the uniqueness of the pitch angle θ.

：(4) Calculate roll angle

:

As shown in process 1 of Figure 5, the measured values of the X-axis and Z-axis acceleration sensors are collected as Ax and Az.

As shown in process 2 of Figure 5, substitute Ax into the equation θ=arcSin(Ax/g) to calculate the pitch angle θ.

As shown in process 3 of FIG. 5 , when Ax is greater than 0 and Az is greater than 0, the θ is the pitch angle.

As shown in process 4 of Figure 5, when Ax is greater than 0 and Az is less than 0, then 180°-θ is the pitch angle.

As shown in process 5 of Figure 5, when Ax is less than 0 and Az is less than 0, then 180°+|θ| is the pitch angle.

As shown in process 6 of Figure 5, when Ax is less than 0 and Az is greater than 0; then 360°-|θ| is the pitch angle.

Process 4 as shown in Figure 3, using the X-axis, Y-axis and Z-axis geomagnetic field components H"' _X , H"' _Y and H"' _Z and the pitch angle θ, through

(方位角为零)进行横滚角

计算。Passed

(azimuth is zero) for roll angle

calculate.

(5) Output roll angle

Claims (3)

1. A geomagnetic roll angle measurement system based on a giant magnetoresistive sensor, consisting of a geomagnetic measurement module (1), a pitch angle measurement module (2), a signal conditioning module (3) and a microprocessor (4), its characteristics The geomagnetic measurement module (1) includes pairwise orthogonal X-axis, Y-axis and Z-axis giant magnetoresistive sensors; the pitch angle measurement module (2) includes mutually perpendicular X-axis and Z-axis dual-axis acceleration sensors ; The signal conditioning module (3) includes an amplifier bias zeroing circuit, an instrumentation amplifier, connected to an A/D converter; the geomagnetic measurement module (1) is connected to the microprocessor via a signal conditioning module (3) device (4), the pitch angle measurement module (2) is connected to the microprocessor (4); the geomagnetic measurement module (1) uses a three-axis giant magnetoresistive sensor AAH002-02; the pitch angle measurement module ( 2) ADXL202 biaxial acceleration sensor is adopted; the instrumentation amplifier in the signal conditioning module (3) adopts INA118, and the A/D converter is provided by the microprocessor; the microprocessor (4) adopts Atmega128L; the signal conditioning The module (3) performs amplification, offset zeroing and analog-to-digital conversion on the analog signal measured by the giant magnetoresistive sensor of the geomagnetic measurement module (1); the microprocessor (4) performs multi-sensor fusion processing on the geomagnetic and pitch information Then get the geomagnetic roll angle. 2. The geomagnetic roll angle measurement system based on the giant magnetoresistance sensor according to claim 1, characterized in that the signal conditioning module (3) is to pass the analog signal of the giant magnetoresistance sensor through the amplifier bias zeroing circuit by The instrumentation amplifier is amplified, then converted into a digital signal by the A/D converter, and finally sent to the microprocessor; the bias zeroing circuit of the amplifier is: one input terminal of the instrumentation amplifier in the signal conditioning module (3) is connected to a The digital potentiometer R _g , by controlling the digital potentiometer R _g , realizes the adjustment of the power supply voltage of the bridge, achieves the purpose of reducing the zero output of the giant magnetoresistive sensor, improves the sampling resolution of the analog-to-digital converter, and thus improves the ground Accuracy of magnetic field measurements. 3. A method for measuring the geomagnetic roll angle based on the giant magnetoresistance sensor, adopting the geomagnetic roll angle measurement system based on the giant magnetoresistance sensor according to claim 1 to measure, it is characterized in that concrete operation steps are as follows: (1) Measure the geomagnetic roll angle parameters based on the giant magnetoresistive sensor; (2) Collect the measured values of the giant magnetoresistive sensors of each axis, and calculate the magnetic field components on the X-axis, Y-axis and Z-axis according to the measured values

,

,

; (3) Collect the output value of the biaxial acceleration sensor, and use the output value to calculate the pitch angle, realizing the uniqueness of the pitch angle θ; (4) Using the X-axis, Y-axis and Z-axis geomagnetic field components

,

and and the pitch angle θ, through the formula

=

roll angle with zero azimuth

calculate; (5) Output roll angle

; In the step (2), the AAH002-02 sensor uses the change of the magnetic field to cause the change of the resistance value, and the change of the resistance causes the change of the output of the Wheatstone bridge; using the following formula

Calculate the magnetic field components on the X-axis, Y-axis and Z-axis separately

, ,

; where

For AAH002-02 output volume,

is the magnification of INA118,

Sensitivity for AAH002-02,

is the excitation voltage; In the step (3), due to the multi-value problem when the single-axis acceleration sensor measures the pitch angle, the dual-axis acceleration sensor ADXL202 is used to realize the uniqueness of the pitch angle; the specific steps are as follows: set Ax and Az as the X axis and Z axis axis acceleration; (1) Microprocessor (4) Substitute Ax into the equation θ=arcSin(Ax/g) to calculate the pitch angle; (2) According to gSinθ=Ax, gCosθ=Az, there are: When Ax is greater than 0 and Az is greater than 0, then the θ is the pitch angle; When Ax is greater than 0 and Az is less than 0, then 180 ⁰ -θ is the pitch angle; When Ax is less than 0 and Az is less than 0, then 180 ⁰ + |θ| is the pitch angle; When Ax is less than 0 and Az is greater than 0; then 360 ⁰ -|θ| is the pitch angle.

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