WO2016115995A1 - 强磁场误差校准的磁电阻角度传感器及其校准方法 - Google Patents

强磁场误差校准的磁电阻角度传感器及其校准方法 Download PDF

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WO2016115995A1
WO2016115995A1 PCT/CN2016/070743 CN2016070743W WO2016115995A1 WO 2016115995 A1 WO2016115995 A1 WO 2016115995A1 CN 2016070743 W CN2016070743 W CN 2016070743W WO 2016115995 A1 WO2016115995 A1 WO 2016115995A1
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axis
output
offset
calibration
angle sensor
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迪克·詹姆斯·G
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MultiDimension Technology Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/16—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying resistance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D18/00—Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/30—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring angles or tapers; for testing the alignment of axes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D18/00—Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
    • G01D18/002—Automatic recalibration
    • G01D18/004—Continuous recalibration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/16—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying resistance
    • G01D5/165—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying resistance by relative movement of a point of contact or actuation and a resistive track

Definitions

  • the present invention relates to the calibration of the output error of a two-axis magnetoresistive angle sensor for use in a strong magnetic field.
  • the combination of a magnetoresistive sensor and a rotating magnet provides an attractive means of non-contact measurement of the direction of the rotating shaft for a variety of automotive, industrial and consumer products.
  • magnetic angle sensors in the prior art for measuring the direction of a magnetic field.
  • problems well known in the art such as excessive size, insufficient sensitivity, insufficient dynamic range, high cost, low reliability, and other problems. Therefore, it is still necessary to further improve the magnetoresistance angle sensor to design a magnetoresistive angle sensor having high performance, particularly a magnetoresistive angle sensor which can be easily used in combination with an integrated circuit and an existing manufacturing method.
  • the finite value that can be achieved by the pinned layer of the GMR or TMR magnetoresistive angle sensor results in increased output error is a common knowledge in the art as the applied magnetic field increases. The reason for this is that the applied external magnetic field causes a slight shift in the magnetization direction of the pinned layer.
  • the present invention proposes a correction algorithm. When applied to the dual-axis TMR/GMR angle sensor, the algorithm greatly reduces the measurement error that is strongly related to the applied magnetic field strength.
  • the new algorithm includes simple math and simple one-time calibration, which expands the magnetic field application range of the dual-axis TMR/GMR magnetoresistive angle sensor and greatly improves the accuracy of its measurement in high magnetic fields.
  • the present invention provides a two-axis magnetoresistive angle sensor comprising two orthogonal single-axis magnetoresistance angle sensors for detecting an applied magnetic field along mutually perpendicular X-axis and Y-axis directions,
  • the signal error is added to or subtracted from the X-axis output and the Y-axis output to calculate a calibrated X-axis output signal and a calibrated Y-axis output signal,
  • the X-axis output and the Y-axis output are offset-calibrated X-axis voltage output and offset-calibrated Y-axis voltage output, respectively, and the first offset calibration value is subtracted from the X-axis voltage output. Obtaining the offset-calibrated X-axis voltage output; subtracting the second offset calibration value from the Y-axis voltage output to obtain the offset-calibrated Y-axis voltage output.
  • the X-axis voltage output is divided by a first known vector amplitude calibration value, the Y-axis voltage output being divided by a second known vector amplitude calibration value, and the first known The vector magnitude calibration value and the second known vector magnitude calibration value are set to one.
  • the offset calibrated X-axis voltage output is divided by a first known vector amplitude calibration value, the offset calibrated Y-axis voltage output being divided by a second known vector amplitude calibration value, and
  • the first known vector amplitude calibration value and the second known vector amplitude calibration value are set to one.
  • Each of the single-axis magnetoresistive angle sensors is a GMR spin valve or a TMR sensor.
  • the dual-axis magnetoresistive angle sensor further includes a temperature sensing sensor.
  • the temperature signal generated by the temperature sensor is used to calculate a linear expansion peak, the offset calibration value, and/or a vector magnitude calibration value with respect to temperature.
  • the maximum amplitudes of the voltage outputs of the two orthogonal X-axis single-axis magnetoresistive sensors and the Y-axis single-axis magnetoresistive sensor are approximately equal.
  • the known calibration vector amplitude is
  • V p ⁇ Max[Vx( ⁇ ,H)]-Min[Vx( ⁇ ,H)]+Max[Vy( ⁇ ,H)]-Min[Vy( ⁇ ,H)] ⁇ /4.
  • the biaxial magnetoresistive angle sensor further includes an element for storing a calibration constant of an offset value and a maximum amplitude, wherein the calibration constant of the maximum amplitude is rotated by the single magnetic field angle sensor in the applied magnetic field. Calculated from the maximum and minimum peaks obtained at 360 degrees, the two-axis magnetoresistive angle sensor only needs to store the peak value and the offset value of each of the single-axis magnetoresistive sensors for calibration.
  • the present invention also provides a method for calibrating a magnetic field measurement error of a magnetoresistive angle sensor, comprising:
  • the applied magnetic field along the mutually perpendicular X-axis and Y-axis directions is detected by two orthogonal single-axis magnetoresistive angle sensors;
  • the signal error is added to or subtracted from the X-axis output and the Y-axis output, respectively, to calculate a calibrated X-axis output signal and a calibrated Y-axis output signal;
  • the inverse tangent of the quotient of the calibrated Y-axis output signal divided by the calibrated X-axis output signal is calculated to calculate the angle of rotation of the applied magnetic field.
  • the X-axis output and the Y-axis output are offset-calibrated X-axis voltage output and offset-calibrated Y-axis voltage output, respectively, and the first offset calibration value is subtracted from the X-axis voltage output. Obtaining the offset-calibrated X-axis voltage output; subtracting the second offset calibration value from the Y-axis voltage output to obtain the offset-calibrated Y-axis voltage output.
  • the X-axis voltage output is divided by a first known vector amplitude calibration value, the Y-axis voltage output being divided by a second known vector amplitude calibration value, and the first known The vector magnitude calibration value and the second known vector magnitude calibration value are set to one.
  • the offset calibrated X-axis voltage output is divided by a first known vector amplitude calibration value, the offset calibrated Y-axis voltage output being divided by a second known vector amplitude calibration value, and
  • the first known vector amplitude calibration value and the second known vector amplitude calibration value are set to one.
  • the peak, the offset calibration value, and/or the vector magnitude calibration value are linearly spread with respect to temperature.
  • the maximum amplitudes of the voltage outputs of the two orthogonal X-axis single-axis magnetoresistive sensors and the Y-axis single-axis magnetoresistive sensor are approximately equal.
  • the known calibration vector amplitude is
  • V p ⁇ Max[Vx( ⁇ ,H)]-Min[Vx( ⁇ ,H)]+Max[Vy( ⁇ ,H)]-Min[Vy( ⁇ ,H)] ⁇ //4.
  • the magnetoresistive angle sensor only needs to store the peak value and the offset value of each of the single-axis magnetoresistive sensors for calibration.
  • the beneficial effects of the present invention are: the invention applies the correction algorithm to the dual-axis magnetoresistive angle sensor, greatly reduces the measurement error strongly related to the applied magnetic field strength, and expands the magnetic field of the dual-axis magnetoresistive angle sensor.
  • Figure 1 shows the working principle of the magnetoresistive angle sensor.
  • 2A is an ideal voltage output curve of the two-axis magnetoresistive angle sensor 1.
  • 2B is an ideal XY-curve of the two-axis magnetoresistive angle sensor 1 obtained by plotting the X-axis output and the Y-axis output.
  • FIG. 3A is a non-ideal voltage output curve of the two-axis magnetoresistive angle sensor 1.
  • FIG. 3B is a non-ideal XY-graph obtained by plotting the X-axis output to the Y-axis output of the dual-axis magnetoresistive angle sensor 1.
  • Figure 4A shows the effect of the strength of the different applied magnetic fields on the XY-curve of the X-axis output of the two-axis magnetoresistive angle sensor 1 plotted against the Y-axis output.
  • Fig. 4B is the maximum error of the output of the biaxial angle sensor 1 measured at the intensity of different applied magnetic fields.
  • Figure 5 is a graph showing the common effects observed with all GMR/TMR angle sensors.
  • Figure 6 is a schematic illustration of an MTJ (tunnel magnetoresistive junction) component.
  • Figure 7 is a schematic diagram explaining the movement of the pinning layer resulting from the applied external magnetic field.
  • Fig. 8A is a maximum error XY-curve when the angle of the applied magnetic field with respect to the pinned layer is 33°.
  • Fig. 8B is the maximum error due to the movement of the pinning layer calculated at different magnetic field strengths HPS when the applied magnetic field has an angle of 33 with respect to the pinned layer.
  • Figure 9 shows the amplitude of the waveform of the non-ideal output waveform having an amplitude equal to or less than the ideal output.
  • Figure 10 shows a comparison of the amplitude and uniaxial error of the two axes.
  • Figure 11 shows the uniaxial output error as a function of the biaxial amplitude error, indicating a proportionality between the uniaxial error and the biaxial amplitude error.
  • the graph of Figure 12 shows that the non-ideal output of the angle sensor can be corrected for non-ideal output by adding the measured biaxial amplitude error back to the non-ideally deformed waveform.
  • Figure 13A is an XY-curve plotted from an uncalibrated X-axis output versus a Y-axis output in several applied magnetic fields of different intensities.
  • Figure 13B shows the XY-curve obtained from the corrected output along the X-axis and the Y-axis output at several different applied magnetic field strengths, indicating that the output error can be corrected.
  • Figure 13C shows that the corrected angular error is much smaller than the original error.
  • Figure 14 shows that the algorithm is still valid when the output changes by more than 10%, indicating that the correction algorithm should be insensitive to temperature changes.
  • Figures 15A-C show that the algorithm can reduce the error by a factor of three when calibrating a highly distorted output.
  • Figure 16 shows the design of a two-axis magnetoresistive angle sensor.
  • Figure 17 is a diagram showing another design of a two-axis magnetoresistive angle sensor.
  • FIG. 1 is a schematic diagram showing the working principle of the two-axis magnetoresistive angle sensor 1.
  • the two-axis magnetoresistive angle sensor 1 includes two single-axis magnetoresistive angle sensors that are rotated by 90° with respect to each other to measure the strength of the magnetic field along the X-axis and the Y-axis, respectively. One of them is used to measure the cosine waveform is called a cosine sensor, and the other is used to measure a sinusoidal waveform called a sinusoidal sensor.
  • the magnetoresistive (MR) angle sensor 1 is placed in a rotating magnetic field 2 generated by the magnet 3.
  • the two-axis magnetoresistive angle sensor 1 By detecting the change in resistance of the two-axis magnetoresistive angle sensor 1, the two-axis magnetoresistive angle sensor 1 can measure the angle of rotation of the magnet 3. The resistance change of the aforementioned two-axis magnetoresistive angle sensor 1 changes in a regular sine wave manner.
  • 2A is a sine and cosine output curve of the two-axis magnetoresistive angle sensor 1.
  • the output of the two-axis magnetoresistive angle sensor 1 is plotted against the rotation angle of the rotating magnetic field 2, and the ideal sine and cosine output curves are obtained: a cosine waveform along the X-axis direction and a sinusoidal waveform along the Y-axis; these two waveforms It is an ideal Y-axis sinusoidal waveform 7 and an ideal X-axis cosine waveform 5. If the ideal X-axis voltage output is plotted against the Y-axis voltage output, the resulting curve is a perfect circle as shown in Figure 2B. 9.
  • the vector magnitude of the output voltage component is independent of the angle of rotation, as discussed below, which is a key part of the work of the proposed correction algorithm.
  • the angle of rotation can be calculated using the well-known CORDIC algorithm, in which the voltage of the sinusoidal sensor is divided by the voltage of the cosine sensor, and then the arc tangent of the ratio is calculated to determine the angle of rotation of the magnet 3.
  • 3A and 3B are non-ideal output curves of a TMR (tunneling magnetoresistance) or GMR (giant magnetoresistance) biaxial magnetoresistive sensor 1 when the magnetic field is externally strengthened.
  • 3A shows that the Y-axis waveform 13 and the X-axis waveform 11 of the two-axis magnetoresistive angle sensor 1 are strongly distorted.
  • Figure 3B is an ideal XY-output curve 9 formed by an ideal output and a non-ideal output forming a non-ideal XY-output curve 15.
  • the non-ideal XY-output curve 15 is not circular and tends to form a star-shaped or square shape in the XY plane, wherein the vector size of the biaxial sensor 1 is not independent of the angle of rotation. .
  • the vector 33 at 33 degrees and the vector 31 at 45 degrees show that the aforementioned distortion produces an error when calculating the angle of the rotating magnetic field 2 with CORDIC.
  • the point 32 on the twisted curve 15 should be the point 32' on the curve 9 of the ideal curve.
  • the point 34 on the warp curve 15 is not mapped along the vector 33 to a corresponding point on the ideal curve 9, but to a point 34' having a smaller angle. This indicates that the output curve has an error in the high field, and an angle-dependent error or a nonlinear error is generated, so the output of the MR angle sensor 1 needs to be corrected.
  • Figure 4 shows the dependence of the measurement error on the magnetic field strength.
  • Figure 4A is an XY-output curve measured at different magnetic field strengths. It should be noted that the enhanced applied magnetic field causes an increase in error, as illustrated by the set of curves 15 of Figure 4A at a higher applied magnetic field. An applied magnetic field of different strength is applied to the magnetoresistive angle sensor 1.
  • 4B is a graph obtained by applying a rotating magnetic field 2 to a 360-degree rotation, and the maximum error generated by the output of the two-axis magnetoresistive angle sensor 1 is plotted against the intensity of the rotating magnetic field 2, which further clearly shows that the output error is The magnetic field strength increases and increases.
  • Figure 5 is a graph illustrating the role of the GMR angle sensor. It relates to the structure of a GMR or TMR element.
  • the output transmission curve 4 is the same as the ideal output curve 5. If the intensity of the rotating magnetic field is as high as 400 Oersted, the output curve 6 becomes a triangle.
  • the difference or uniaxial error between the twisted curve and the ideal curve is curve 8.
  • This error from the ideal output curve may be caused by imperfect saturation or a non-ideal behavior of the free layer in a low applied magnetic field. It may also be caused by the limited strength of the pinning layer (PL) pinning field under a strong applied magnetic field.
  • PL pinning layer
  • the present invention discloses a correction algorithm that calibrates the high field error of the aforementioned sensor output caused by the pinning layer or other causes.
  • FIG. 6 shows a simple MTJ structure.
  • the sensor elements each comprise a ferromagnetic layer-insulation layer-ferromagnetic layer structure (FM-I-FM).
  • FM-I-FM ferromagnetic layer-insulation layer-ferromagnetic layer structure
  • the magnetoresistance effect of this structure is called tunnel magnetoresistance (TMR) and its size can easily exceed DR/RO ⁇ 200%.
  • TMR tunnel magnetoresistance
  • the change in resistance of the sensing element is proportional to the cosine of the relative orientation angle between the magnetization directions of the free layer 17 and the pinned layer (PL) 21, and therefore, if the design of the MTJ is such that the FL17 is rotated in response to the applied external magnetic field H While the magnetization direction of the PL 21 is rigidly fixed, the output resistance of the sensor element is related to the direction of the applied magnetic field. Since the resistance change of the MTJ is a function of the relative angle between the FL and the magnetization direction of the PL layer, any slight rotation of the pinned layer 21 increases the error of the sensor.
  • the rotation angle of the magnetization direction of the PL can be obtained by the equation (3), and this rotation angle is expressed as ⁇ err .
  • the pinning magnetic field (Hp) intensity in equation (4) is typically about 1500 Oe, which limits the accuracy of the MTJ magnetoresistive sensor.
  • the measured data shows that when the applied applied magnetic field has an angle of about 30 degrees, the angular measurement error is the most serious, which can be observed by mapping the data points from the non-ideal curve 15 to the ideal curve 9, see Figure 8A. .
  • the measurement error is the smallest.
  • Figure 8B is a plot of Hp with the calculated maximum PL angle error. Assuming that the maximum measurement error occurs when the applied angle of the applied magnetic field is 33°, the calculation is performed by the equation (5). The error curve calculated using Equation 5 is very consistent with the error curve measured on real equipment.
  • Fig. 9 is a graph plotting the angle of the voltage output wave of the two-axis magnetoresistive angle sensor 1 with respect to the applied external magnetic field.
  • the zero degree in the figure represents the applied magnetic field parallel to the Hp direction.
  • the amplitudes of the non-ideal curves 11 and 13 are always equal to or smaller than the amplitudes of the ideal curves 5 and 7, and the magnitude of the measurement error is 90 degrees.
  • the non-ideal curves 11 and 13 and the ideal curves 5 and 7 have the same maximum and minimum peaks.
  • the above model is universal in measurement, indicating that a correction algorithm can be established accordingly.
  • Fig. 10 is an error waveform chart drawn.
  • Ideal amplitude 27 biaxial vector amplitude
  • original amplitude 29 vector amplitude of biaxial triangular wave
  • amplitude difference 31 ideal amplitude - original amplitude
  • error of triangular waveform 33 uniaxial difference of ideal sine and cosine waveform and triangular waveform error .
  • the non-ideal sinusoidal waveform 13 is represented as V SIN ( ⁇ , H); the non-ideal cosine wave 11 is represented as Vcos( ⁇ , H); the offsets of the sine and cosine waveforms are denoted as V OS and V OC , respectively;
  • the peaks of the sine and cosine waveforms are expressed as V ps and V pc ;
  • V'sin( ⁇ ,H) and V'cos( ⁇ ,H) are used as the offset and amplitude corrected sensor outputs; then the following equations can be used to correct non- The ideal output waveform:
  • V' s ( ⁇ , H) ⁇ V sin ( ⁇ ,H)-V os ⁇ /V ps (7)
  • V' c ( ⁇ ,H) ⁇ V cos ( ⁇ ,H)-V oc ⁇ /V pc (8)
  • V peak (V peak is the sensor or amplitude of the maximum or minimum signal) and V offset (the offset of the sensor signal) can be calculated by Equation 12-15:
  • V pc ⁇ Max[V cos ( ⁇ ,100)]-Min[V cos ( ⁇ ,100)] ⁇ /2 (12)
  • V ps ⁇ Max[V sin ( ⁇ ,100)]-Min[V sin ( ⁇ ,100)] ⁇ /2 (13)
  • V oc ⁇ Max[V cos ( ⁇ ,100)]+Min[V cos ( ⁇ ,100)] ⁇ /2 (14)
  • V os ⁇ Max[V sin ( ⁇ ,100)]+Min[V sin ( ⁇ ,100)] ⁇ /2 (15)
  • V PC , V PS , V oc and V OS are parameters that need to be calculated.
  • V P is sufficient.
  • H can be any value.
  • V p ⁇ Max[V c ( ⁇ ,100)]-Min[V c ( ⁇ ,100)]+Max[V s ( ⁇ ,100)]-Min[V s ( ⁇ ,100)] ⁇ /4 (16)
  • V' s ( ⁇ ,H) V sin ( ⁇ ,H) (17)
  • V' c ( ⁇ ,H) V cos ( ⁇ ,H) (18)
  • the calibration can be performed by the following equation:
  • Figure 13A is an ideal XY-curve 9 obtained by plotting a set of non-ideal XY-curves 15 resulting from an uncalibrated X-axis output versus a Y-axis output and an ideal X-axis output versus Y-axis output.
  • Figures 13B and 130 show the effects corrected by equations (18) and (19).
  • Figure 13B shows that the calibrated XY-curve 10 obtained by plotting the calibrated X-axis voltage output versus the Y-axis voltage output is the ideal circle, which is the same as the circle of the ideal output XY-curve 9.
  • Figure 13C shows that the corrected angular error 41 is much smaller than the original error 39, and the algorithm correction appears to reduce the correlation between the nonlinear angular error and the strength of the applied magnetic field.
  • a and ⁇ are known temperature coefficients of the sensor 1
  • T1 is the temperature at which the MR angle sensor 1 is calibrated
  • T is the operating temperature measured by an on-chip thermometer.
  • A-C of Fig. 14 shows that the XY-curve obtained by plotting the output of the corrected X-axis to the output of the Y-axis is circular.
  • Figures 15A, 15B and 15C show that the output error is reduced by more than three times.
  • the algorithm is applied to highly distorted output curves.
  • 15A is a non-ideal XY-curve 15, an ideal XY-curve 9 and a corrected XY-curve 10 obtained by plotting the corrected X-axis and output Y-axis output.
  • the curves 11 and 13 of the triangular waveform become the ideal cosine or sinusoidal waveforms 5 and 7 in Fig. 15B.
  • Figure 15C shows that the original error of the corrected angular error ratio is three times smaller.
  • Curve 35 is the error before calibration and curve 37 is the error after calibration.
  • Figure 16 shows one possible arrangement of four sensor chips 120, 121, 122 and 123 to produce a two-axis magnetic field angle sensor 1 for detecting the sine and cosine components of a rotating magnetic field.
  • Four sensors are placed around the circumference of the central ASIC 124 and electrically connected to each other by standard wire bonding techniques.
  • the arrangement of the four chips is such that the orthogonal full bridge has a common center 126.
  • the ASIC can contain an ESD protection circuit, and it can also provide circuitry for converting the signal output angle of the quadrature sensor to a digital format.
  • Figure 17 shows another possible arrangement of four sensor chips 130, 131, 132 and 133 to produce a two-axis magnetic field angle sensor 1 that detects the sine and cosine components of the rotating magnetic field.
  • the four sensors are circularly symmetrical to each other and are located on top of an ASIC 135. Unlike the design of Figure 16, each sensor chip is skewed such that sensor 1 is closer to the common geometric center.
  • the arrangement of the four chips allows this orthogonal full bridge to have a common center 136.
  • the ASIC can contain an ESD protection circuit, and it can also provide circuitry for converting the signal output angle of the quadrature sensor to a digital format.
  • the biaxial magnetic field angle sensor 1 is deposited or connected to an ASIC (application specific integrated chip) circuit or other device to perform the operation of the algorithm disclosed herein.
  • the design also includes internal or external data storage.
  • the ASIC includes means for calculating a difference between a known vector magnitude calibration value and a real-time two-axis vector magnitude based on the voltage output of each of the single-axis magnetic field angle sensors X-axis and Y-axis, and Means for dividing the square root of the difference by 2 to calculate an error signal, and means for increasing or subtracting the error signal from the respective X and Y voltage outputs to generate an error corrected X voltage output signal and error corrected Y
  • the voltage output signal wherein the inverse tangent of the error corrected Y voltage signal and the error corrected X voltage output is the angular value of the applied external magnetic field to be measured.
  • the biaxial magnetic field angle sensor 1 may also include a temperature sensor, the temperature signal from the temperature sensor being used for linearly expanding known calibration and offset values with respect to temperature.
  • Temperature sensors and data stores may be included in the ASIC 124 or they may be located separately from the ASIC 124 within the angle sensor chip or connected to the chip.

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Abstract

一种双轴磁电阻角度传感器（1）及磁场误差校准方法，包括两个检测沿相互垂直的X-轴和Y-轴方向外加磁场的单轴磁电阻角度传感器，实时计算单轴磁电阻角度传感器的沿X-轴和Y-轴的电压输出的矢量幅度的元件，计算已知的校准矢量幅度和测量的矢量幅度的差别的元件，将差别用（I）相除以计算信号误差的元件，分别将所述信号误差加入到所述X-轴输出和Y-轴输出或从其中减去以计算校准的X-轴和Y-轴的输出信号的元件，计算校准的Y-轴输出信号除以校准的X-轴的输出信号所得的商的反正切以计算所述外加磁场的旋转角度的元件。将该磁场误差校准方法应用在双轴磁电阻角度传感器中，降低了测量误差、扩大了磁场应用范围并提高了其在高磁场中的测量精度。

Description

强磁场误差校准的磁电阻角度传感器及其校准方法 技术领域
本发明涉及在强磁场下使用的双轴磁电阻角度传感器的输出误差的校准。
背景技术
磁电阻传感器和旋转磁体相结合提供了用于各种汽车，工业和消费产品的旋转轴的方向的非接触式测量的一个有吸引力的手段。在现有技术中有许多不同类型的磁角度传感器，用于测量磁场的方向。不幸的是，它们都存在在本领域中公知的问题，例如，过大的尺寸，灵敏度不足，动态范围不足，高成本，低可靠性，以及其他问题。因此，仍然有必要对磁电阻角度传感器进一步地改进以设计具有高性能的磁电阻角度传感器，特别是可以与集成电路和现有制造方法很容易地结合使用的磁电阻角度传感器。
当外加磁场增加时，GMR或TMR磁电阻角度传感器的钉扎层的可能取得的有限值导致了增加的输出的误差是本领域的公知常识。其原因是所施加的外磁场造成被钉扎层的磁化方向的轻微的移动。为解决此问题，本发明提出了一个校正算法。本算法应用于双轴TMR/GMR角度传感器时，大大降低了和外加磁场强度强烈相关的测量误差。新算法包括简单的数学和简单的一次性校准，扩大了双轴TMR/GMR磁电阻角度传感器的磁场应用范围并极大地提高了其在高磁场中的测量的精度。
发明内容
为了解决以上问题，本发明提供一种双轴磁电阻角度传感器，包括两个检测沿相互垂直的X-轴和Y-轴方向外加磁场的正交单轴磁电阻角度传感器，
实时计算所述单轴磁电阻角度传感器的沿X-轴和Y-轴的电压输出的测量的矢量幅度的元件，
计算已知的校准矢量幅度和所述测量的矢量幅度的差值的元件，
将所述的差值用
Figure PCTCN2016070743-appb-000001
相除以计算出信号误差的元件，
分别将所述信号误差加入到所述X-轴输出和Y-轴输出或从其中减去以计算校准的X-轴输出信号和校准的Y-轴的输出信号的元件，
计算校准的Y-轴输出信号除以校准的X-轴的输出信号的商的反正切以计算所述外加磁场的旋转角度的元件。
所述沿X-轴输出和Y-轴输出分别是偏移校准的X-轴电压输出和偏移校准的Y-轴电压输出，将第一偏移校准值从所述X-轴电压输出减去获得所述偏移校准的X-轴电压输出；将第二偏移校准值从所述Y-轴电压输出减去获得所述的偏移校准的Y-轴电压输出。
所述沿X-轴电压输出被第一已知的矢量幅度校准值相除，所述沿Y-轴电压输出被第二已知的矢量幅度校准值相除，并且所述第一已知的矢量幅度校准值和第二已知的矢量幅度校准值设定为1。
所述偏移校准的X-轴电压输出被第一已知的矢量幅度校准值相除，所述偏移校准的Y-轴电压输出被第二已知的矢量幅度校准值相除，并且所述第一已知的矢量幅度校准值和第二已知的矢量幅度校准值设定为1。
所述每一个单轴磁电阻角度传感器均为GMR自旋阀或TMR传感器。
所述双轴磁电阻角度传感器还包括温度感应传感器。
所述温度传感器产生的温度信号用来相对于温度计算线性扩展峰值、所述偏移校准值和/或矢量幅度校准值。
两个正交的所述X-轴单轴磁电阻传感器和Y-轴单轴磁电阻传感器的电压输出的最大振幅近似相等。
已知的校准矢量幅度为
Vp＝{Max[Vx(θ，H)]-Min[Vx(θ，H)]+Max[Vy(θ，H)]-Min[Vy(θ，H)]}/4。
所述第一偏移校准值是Vox＝{Max[Vcos(θ，H)]+Min[Vcos(θ，H)]}/2，所述第二偏移校准值是Voy＝{Max[Vsin(θ，H)]+Min[Vsin(θ，H)]}/2。
所述双轴磁电阻角度传感器还包括储存偏移值和最大振幅的校准常数的元件，所述的最大振幅的校准常数是由每一个单轴磁电阻角度传感器在所述外加磁场旋转一个 360度时得到的最大和最小峰值计算而来，所述双轴磁电阻角传感器只需储存所述的峰值和所述每一个单轴磁电阻传感器用于校准的所述偏移值。
相应地，本发明还提供了一种磁电阻角度传感器磁场测量误差校准方法，包括：
通过两个正交的单轴磁电阻角度传感器检测沿相互垂直的X-轴和Y-轴方向的外加磁场；
实时计算所述磁电阻角度传感器的沿X-轴和Y-轴的电压输出的测量的矢量幅度；
计算已知的校准矢量幅度和所述测量的矢量幅度的差值；
将所述的差值用
Figure PCTCN2016070743-appb-000002
相除以计算出信号误差；
分别将所述信号误差加入到所述X-轴输出和Y-轴输出或从其中减去以计算校准的X-轴输出信号和校准的Y-轴的输出信号；
计算校准的Y-轴输出信号除以校准的X-轴的输出信号所得的商的反正切以计算所述外加磁场的旋转角度。
所述沿X-轴输出和Y-轴输出分别是偏移校准的X-轴电压输出和偏移校准的Y-轴电压输出，将第一偏移校准值从所述X-轴电压输出减去获得所述偏移校准的X-轴电压输出；将第二偏移校准值从所述Y-轴电压输出减去获得所述的偏移校准的Y-轴电压输出。
所述沿X-轴电压输出被第一已知的矢量幅度校准值相除，所述沿Y-轴电压输出被第二已知的矢量幅度校准值相除，并且所述第一已知的矢量幅度校准值和第二已知的矢量幅度校准值设定为1。
所述偏移校准的X-轴电压输出被第一已知的矢量幅度校准值相除，所述偏移校准的Y-轴电压输出被第二已知的矢量幅度校准值相除，并且所述第一已知的矢量幅度校准值和第二已知的矢量幅度校准值设定为1。
所述峰值、所述偏移校准值和/或矢量幅度校准值相对于温度线性扩展。
所述两个正交的X-轴单轴磁电阻传感器和Y-轴单轴磁电阻传感器的电压输出的最大振幅近似相等。
所述已知的校准矢量幅度为
Vp＝{Max[Vx(θ，H)]-Min[Vx(θ，H)]+Max[Vy(θ，H)]-Min[Vy(θ，H)]}//4。
所述第一偏移校准值是Vox＝{Max[Vcos(θ，H)]+Min[Vcos(θ，H)]}/2，所述第二偏移校准值是Voy＝{Max[Vsin(θ，H)]+Min[Vsin(θ，H)]}/2。
储存偏移值和最大振幅的校准常数，所述的最大振幅的校准常数是由在每一个单轴磁电阻角度传感器在所述外加磁场旋转一个360度时得到的最大和最小峰值计算而来，所述磁电阻角度传感器只需储存所述的峰值和所述每一个单轴磁电阻传感器用于校准的所述偏移值。
由于以上技术方案，本发明的有益效果为：本发明将校正算法应用在双轴磁电阻角度传感器中，大大降低了和外加磁场强度强烈相关的测量误差，扩大了双轴磁电阻角度传感器的磁场应用范围并极大地提高了其在强磁场中的测量的精度。
附图说明
图1为磁电阻角度传感器的工作原理。
图2A为双轴磁电阻角度传感器1的理想的电压输出曲线。
图2B为双轴磁电阻角度传感器1由X-轴输出和Y-轴输出作图得到的理想XY-曲线图。
图3A为双轴磁电阻角度传感器1的非理想的电压输出曲线。
图3B为双轴磁电阻角度传感器1由X-轴输出对Y-轴输出作图得到的非理想XY-曲线图。
图4A为不同外加磁场的强度对双轴磁电阻角度传感器1的X-轴输出对Y-轴输出作图得到的XY-曲线的影响。
图4B为在不同外加磁场的强度下测得的双轴角度传感器1的输出的最大误差。
图5为一个曲线图，展示了在所有GMR/TMR角度传感器观察到的共同效果。
图6为MTJ(隧道磁阻结)元件的示意图。
图7为一个示意图解释由所施加的外磁场而产生的钉扎层的移动。
图8A为当外加磁场相对于钉扎层的角度为33°时的最大误差XY-曲线。
图8B为当外加磁场相对于钉扎层的角度为33°时，在不同的磁场强度HPS下计算得到的由于钉扎层移动引起的最大误差。
图9表明非理想输出波形的幅度等于或小于理想输出的波形的幅度。
图10示出了双轴的幅度和单轴误差的比较。
图11为单轴输出误差以双轴幅值误差为函数作图，表明单轴误差和双轴幅度误差之间成比例。
图12的曲线图表明的角度传感器的非理想输出可以通过将测得的双轴幅度误差加回非理想的变形的波形，从而对非理想输出进行校正。
图13A为在几个不同强度的外加磁场中由没有校准的X轴输出对Y轴输出作图得到的XY-曲线。
图13B在几个不同的外加磁场强度下由校正的沿X轴的输出与Y轴输出作图得到的XY-曲线，表明了输出误差可以被校正。
图13C显示了校正后的角度误差比原始误差小很多。
图14显示该算法在输出变化超过10％时，依然有效，这表明所述校正算法应该是对温度变化不敏感。
图15A-C表明本算法用于校准高度扭曲的输出时可以使误差降低3倍。
图16为一种双轴磁电阻角度传感器的设计。
图17为另一种双轴磁电阻角度传感器的设计。
具体实施方式
图1为双轴磁电阻角度传感器1工作原理示意简图。双轴的磁电阻角度传感器1包括两个相对彼此旋转90°的单轴磁电阻角度传感器，以便分别沿X轴和Y轴测量磁场的强度。其中之一用于测量余弦波形被称为余弦传感器，另一个用于测量正弦波形被称为正弦传感器。磁电阻(MR)角度传感器1被放置在由磁铁3产生的一个旋转磁场2中，通过检测双轴磁电阻角度传感器1的电阻变化，双轴磁电阻角度传感器1可以测量磁铁3的旋转角度。前述的双轴磁电阻角度传感器1的电阻变化呈正余弦波规律变化。
图2A为双轴磁电阻角度传感器1的正余弦输出曲线。双轴磁电阻角度传感器1的输出对旋转磁场2的旋转角度作图，得到理想的正弦和余弦输出曲线：沿X轴方向是一余弦波形，沿Y轴向是正弦波形；这两个波形是理想的Y轴正弦波形7和理想X轴余弦波形5。如果理想的X轴电压输出对Y轴电压输出作图，所得曲线是如图2B所示的正圆 9。具体而言，这意味着输出电压分量的矢量幅度是独立于旋转角度的，如下面讨论的，这一特点是使得本发明所提出的校正算法的可以工作的关键部分。在任何情况下，旋转角度可以使用公知的CORDIC算法计算，其中正弦传感器的电压除以余弦传感器的电压，然后计算比值的反正切，来确定磁铁3的旋转角度。
图3A和图3B为TMR(tunneling magnetoresistance)或GMR(giant magnetoresistance)双轴磁电阻传感器1在外加强磁场时的非理想输出曲线。图3A显示双轴的磁电阻角度传感器1的Y轴波形曲线13和X轴波形曲线11被强烈扭曲。图3B是理想的输出形成的理想的XY-输出曲线9和非理想的输出形成非理想的XY-输出曲线15。在该图，很明显非理想XY-输出曲线15不成圆形，并趋向于形成在XY平面内的星形线或正方形的形状，其中所述双轴传感器1的矢量大小并不是独立于旋转角度。在33度的矢量33和在45度矢量31显示前述的扭曲在用CORDIC计算旋转磁场2的角度时会产生误差。扭曲的曲线15上点32应该是理想曲线的曲线9上的点32′。在扭曲曲线15上的点34不沿矢量33映射到理想曲线9上对应的一点，而是映射到有较小角度的点34′。这表明输出曲线在高场时会有误差，会产生角度依赖性误差或非线性的误差，因此需要对MR角度传感器1的输出进行修正。
往往存在可以最小化传感器输出的这种非线性的外加的磁场2测量误差的最佳值，但一般来说，测量误差随着所施加的外磁场2的强度增加而增加。图4显示了的测量误差对磁场强度依赖性。图4A是在不同的磁场强度下测得的XY-输出曲线，需要注意，增强的外加磁场会导致误差的增加，图4A的一组在较高外加磁场下输出曲线15说明了这一点。对磁电阻角度传感器1施加不同强度的外加磁场。图4B为外加旋转磁场2做360度旋转，双轴磁电阻角度传感器1的输出所产生的最大误差对外加旋转磁场2的强度作图得出的曲线，其进一步清楚地表明了输出误差随着磁场强度增加而增加。
图5是一个曲线图，用来说明GMR角度传感器的作用。它涉及一种GMR或TMR元件的结构。当旋转磁场是低至50奥斯特，输出传输曲线4和理想的输出曲线5相同。如果旋转磁场的强度高达400奥斯特，输出曲线6变为三角形。扭曲曲线和理想曲线的差或单轴误差为曲线8。
这种偏离理想的输出曲线的误差可能是由不完全饱和或自由层在低外加磁场的非理想行为引起的。它也可能是在强外加磁场下钉扎层(PL)钉扎场的有限的强度造成的。下 面，我们将说明，高场误差主要由钉扎层的非理想性行为引起，其中所述被钉扎层磁化方向由于所施加的外磁场而稍微移动，而此种移动随所施加的外加磁场的强度值而增加。
本发明公开了一种校正算法，校准由钉扎层或其它原因引起的前述的传感器输出的高场误差。
图6为简单的MTJ结构。传感器元件各自包括一铁磁性层-绝缘层-铁磁层结构(FM-I-FM)的。通常有至少两个被绝缘隧道势垒19分隔开的铁磁金属层，隧道势垒19的厚度约为2nm厚，该层的厚度控制所述隧道结的电阻。这种结构的磁阻效应被称为隧道磁阻(TMR)，它的大小可以很容易地超过DR/RO≈200％。传感元件的电阻的变化是正比于自由层17和钉扎层(PL)21的磁化方向之间的相对取向角的余弦，因此，如果MTJ的设计使得FL17旋转的响应于施加的外磁场H，而PL21的磁化方向被刚性地固定，所述传感器元件的输出电阻是与所施加的磁场的方向有关。因为MTJ的电阻变化为FL和PL层的磁化方向之间的相对角度的函数，所以钉扎层21的任何微小的旋转都会增加传感器的误差。
假设FL17的磁化完全遵循所施加的外磁场的角度，误差的分析可以通过仅考虑PL21磁化的方向21。图7示出了钉扎磁场的方向22，PL21的磁化的方向21’，和外加磁场2的两个分量的X2’和Y2”的方向。为了确定PL21所施加的外加磁场2的响应，作了如下通常的自由能分析了，其中该系统的能量依赖于相对于总磁场的PL21的磁化方向：
Figure PCTCN2016070743-appb-000003
Figure PCTCN2016070743-appb-000004
Figure PCTCN2016070743-appb-000005
通过方程(3)可以求出PL的磁化方向的旋转角度，这个旋转角度表示为θerr.
Figure PCTCN2016070743-appb-000006
方程(4)中的钉扎磁场(Hp)强度通常约为1500Oe，这限制了MTJ磁电阻传感器的精确度。
测得的数据表明，当所施加的外加磁场的角度约为30度，角度的测量误差最严重，这一点可以通过把数据点从非理想的曲线15的映射到理想曲线9观察到，见图8A。另外，外加磁场的角度是45度时，测量误差最小。图8B是用计算出的最大PL角度误差对Hp作图。假设最大测量误差是发生在当外加磁场的施加的角度为33°时，计算由公式(5)进行。用公式5计算得到的误差曲线与在真实设备上测量的误差曲线非常一致。
Figure PCTCN2016070743-appb-000007
图9是用双轴磁电阻角度传感器1的电压输出波对所施加的外磁场的角度作图。图中的零度表示所施加的平行于Hp方向的磁场。双轴磁电阻角度传感器1的输出模型，Cos＝理想余弦轴电压，Sin＝理想正弦轴电压，为Ct＝三角形非理想余弦信号，ST＝三角形非理想正弦信号。
需要注意的是非理想曲线11和13的幅度是始终等于或比理想曲线5和7幅度小，并且测量误差大小呈90度相位。非理想曲线11和13和理想曲线5和7具有相同的最大和最小峰值。上述模型在测量中具有普遍性，表明可以据此建立一个校正算法。
为了解释这个校正方法中，图10是绘制的误差波形曲线。理想幅度27＝双轴矢量幅度；原始幅值29＝双轴三角波的矢量幅度；幅度差31＝理想幅度-原始幅度；三角波形的误差33＝理想正余弦波形曲线和三角波形误差的单轴差。
注意，幅度差很容易实时计算，三角形误差33在实际测量中不可知，但它与幅度差相关，这一点显示于图11。在图10中Cos-CT(曲线7-曲线13)的差被表示为曲线31对CT和ST的向量幅度(曲线11和13矢量幅度)曲线29作图。令人惊讶的是，图11表明，非理想曲线的幅度(测量的矢量幅度)和每一个轴的预期峰值(振幅)之间的差与角度测量误差(三角形误差)成比例，这个比例，也就是斜率为：
Figure PCTCN2016070743-appb-000008
由此可见，非理想和理想响应之间的向量幅度计算的差值可以实时地被加回到传感器1的输出中校准正交单轴波形。其结果是，图12中的三角形误差34变得比图10中的小得多，非理想的余弦波曲线11经校准后取得了校准的X-轴电压输出曲线16，其与理想的X-轴电压输出曲线的5相同。
将非理想的正弦波形13表示作为VSIN(θ，H)；将非理想的余弦波11表示为Vcos(θ，H)；正弦和余弦波形的偏移分别表示为VOS与VOC；将正弦和余弦波形的峰值表示为Vps和Vpc；V′sin(θ，H)和V′cos(θ，H)作为偏移和幅度校正的传感器输出；然后下面的方程可用于实时纠正非理想的输出波形：
V′s(θ，H)＝{Vsin(θ，H)-Vos}/Vps          (7)
V′c(θ，H)＝{Vcos(θ，H)-Voc}/Vpc        (8)
Figure PCTCN2016070743-appb-000009
Figure PCTCN2016070743-appb-000010
Figure PCTCN2016070743-appb-000011
可以通过公式12-15计算得到Vpeak(Vpeak是最大或最小信号的传感器或幅度)和Voffset的(传感器信号的偏移)：
Vpc＝{Max[Vcos(θ，100)]-Min[Vcos(θ，100)]}/2          (12)
Vps＝{Max[Vsin(θ，100)]-Min[Vsin(θ，100)]}/2          (13)
Voc＝{Max[Vcos(θ，100)]+Min[Vcos(θ，100)]}/2           (14)
Vos＝{Max[Vsin(θ，100)]+Min[Vsin(θ，100)]}/2        (15)
通常情况下只需要计算这四个参数(VPC，VPS，Voc和VOS)。在实际操作中，如果该正弦和余弦波形是相互匹配，只需VP就足够的。这种方法的优点在于不需要储存波形，至多只有需储存四个参数。磁体3只需旋转一个360度就足够了。只要磁阻角度传感器1是饱和的，H可以是任何值。
假设传感器饱和了，经验表明，传感器只需要在一个单一的磁场校准。假设传感器在100G得到了饱和，正弦和余弦曲线匹配的很好，那么下面的实施例说明了如何校准的传感器1：
Vp＝{Max[Vc(θ，100)]-Min[Vc(θ，100)]+Max[Vs(θ，100)]-Min[Vs(θ，100)]}/4      (16)
为了校正误差把下面的方程加到每个测量值中：
V′s(θ，H)＝Vsin(θ，H)        (17)
V′c(θ，H)＝Vcos(θ，H)           (18)
Figure PCTCN2016070743-appb-000012
Figure PCTCN2016070743-appb-000013
Figure PCTCN2016070743-appb-000014
另一个实施例，偏移值比较小，并且正弦和余弦波的峰值相同，那么校准可以通过下面的方程进行：
Figure PCTCN2016070743-appb-000015
Figure PCTCN2016070743-appb-000016
Figure PCTCN2016070743-appb-000017
Figure PCTCN2016070743-appb-000018
图13A是没有校准的X轴输出对Y轴输出作图得到的一组非理想的XY-曲线15和理想的X轴输出对Y轴输出作图得到的理想的XY-曲线9。图13B和130示出了用公式(18)和(19)修正后的效果。图13B表明经校准的X轴电压输出对Y轴电压输出作图得到的校准的XY-曲线10是理想的圆，和理想输出XY-曲线9的圆相同。图13C显示了校正后的角度误差41比原始误差39小很多，算法修正似乎降低了非线性角度误差和外加磁场的强度的相关性。
使用本算法时需要注意，如果峰值和偏移随温度变化，在这种情况下，需要进行温度相关的校准。一般来说，这可以通过下面的假设进行：
Vps＝Vps(T)＝Vps(T1)-aT               (26)
Vpc＝Vpc(T)＝Vpc(T1)-aT               (27)
Vos＝Vos(T)＝Vos(T1)-βT              (28)
Voc＝Voc(T)＝Voc(T1)-βT              (29)
在这里，a和β是传感器1的已知的温度系数，T1是MR角度传感器1被校准的时的温度，而T是用一个片上温度计测量的操作温度。这些温度校正系数可以被用在公式(7)和(8)，从而在本发明的算法中对温度引起的误差进行补偿。
替代的方法，如果峰值和偏移补偿值随温度没有太大变化，该算法不需要温度补偿。图14的A-C′示出了本发明的误差校正方法在10％的输出误差的变化内是有效的：VP/Vp′＝0.99，1，和1.1。图14的A′-C′表明随着外加磁场增强，原始最大误差增大。除了在0-150奥斯特并且VP/Vp′＝1.1的范围，修正后的最大误差是较原始的最大 误差小。图14的A-C表明，修正后的X-轴的输出对Y-轴的输出作图得到的XY-曲线是圆形。
图15A，15B和15C表明，输出误差的降低超过了3倍。该算法被应用于高度扭曲的输出曲线。15A是非理想的XY-曲线15，理想的XY-曲线9和纠正后的X轴与输出Y轴输出作图得到的校准的XY-曲线10。经过实时校正，三角形波形的曲线11和13成为图15B中的理想的余弦或正弦波形5和7。图15C表明校正后的角度误差比的原始误差小3倍。曲线35是校准前的误差，曲线37是校准后的误差。
图16为四个传感器芯片120，121，122和123的一种可能的排布以制作双轴磁场角度传感器1，用来检测旋转磁场的正弦和余弦分量。四个传感器被置于围绕中央的ASIC124的圆周上，并相互通过标准丝焊技术电连接。四个芯片的排布使得这个正交全桥有一共同的中心126。ASIC可含有静电放电保护电路，而且它也可提供用于将正交传感器的信号输出角度变换成数字格式的电路。
图17示出四个传感器芯片130，131，132和133的另一个可能的安排，以制作双轴磁场角传感器1，其检测所述旋转磁场的正弦和余弦分量。四个传感器相互之间呈圆对称，位于一个ASIC135的顶部上。不同于图16的设计，各传感器芯片歪斜使得传感器1更靠近共同几何中心。四个芯片的排布使得这个正交全桥有一共同的中心136。ASIC可含有静电放电保护电路，而且它也可提供用于将正交传感器的信号输出角度变换成数字格式的电路。
双轴磁场角度传感器1被沉积或连接到一个ASIC(application specific integrated chip)电路或其他装置来进行本发明所公开的算法的运行。设计还包括内部或外部的数据存储。具体而言，ASIC包括根据每个单轴磁场角度传感器X-轴和Y-轴的电压输出计算一个已知矢量幅度校准值和实时的两轴矢量幅度之间的差的装置，及其将所述差除以2的平方根以计算误差信号的装置，以及用于从所述各X和Y电压输出增加或减去误差信号的装置，以产生一个误差校正X电压输出信号和误差校正后的Y电压输出信号，其中所述误差校正后的Y电压信号和误差校正后的X电压输出的商的反正切值就是要测量的所施加的外磁场的角度值。
双轴磁场角度传感器1还可以包括温度传感器，来自温度传感器的温度信号被用于线性扩展的相对于温度的已知的校准和偏移值。
温度传感器和数据存储可以包含在ASIC124中，或者它们可以与ASIC124分开位于角度传感器芯片内，或连接到芯片上。
以上所述仅为本发明的优选实施例而已，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化，本发明中的实施也可以进行不同组合变化，凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (20)

  1. 一种双轴磁电阻角度传感器，其特征在于，包括两个检测沿相互垂直的X-轴和Y-轴方向外加磁场的正交的单轴磁电阻角度传感器，
    实时计算所述单轴磁电阻角度传感器的沿X-轴和Y-轴的输出的测量的矢量幅度的元件，
    计算已知的校准矢量幅度和所述测量的矢量幅度的差值的元件，
    将所述的差值用
    Figure PCTCN2016070743-appb-100001
    相除以计算出信号误差的元件，
    分别将所述信号误差加入到所述沿X-轴和Y-轴的输出或从其中减去以计算校准的X-轴输出信号和校准的Y-轴的输出信号的元件，
    计算校准的Y-轴输出信号除以校准的X-轴的输出信号所得的商的反正切以计算所述外加磁场的旋转角度的元件。
  2. 根据权利要求1所述的一种双轴磁电阻角度传感器，其特征在于，所述沿X-轴输出和Y-轴输出分别是偏移校准的X-轴电压输出和偏移校准的Y-轴电压输出，将第一偏移校准值从所述沿X-轴电压输出减去获得所述偏移校准的X-轴电压输出；将第二偏移校准值从所述沿Y-轴电压输出减去获得所述的偏移校准的Y-轴电压输出。
  3. 根据权利要求1所述的一种双轴磁电阻角度传感器，其特征在于，所述沿X-轴电压输出被第一已知的矢量幅度校准值相除，所述沿Y-轴电压输出被第二已知的矢量幅度校准值相除，并且所述第一已知的矢量幅度校准值和第二已知的矢量幅度校准值设定为1。
  4. 根据权利要求2所述的一种双轴磁电阻角度传感器，其特征在于，所述偏移校准的X-轴电压输出被第一已知的矢量幅度校准值相除，所述偏移校准的Y-轴电压输出被第二已知的矢量幅度校准值相除，并且所述第一已知的矢量幅度校准值和第二已知的矢量幅度校准值设定为1。
  5. 根据权利要求1所述的一种双轴磁电阻角度传感器，其特征在于，所述每一个单轴磁电阻角度传感器均为GMR自旋阀或TMR传感器。
  6. 根据权利要求1、2、3或4所述的一种双轴磁电阻角度传感器，其特征在于，包括温度感应传感器。
  7. 根据权利要求6所述的一种双轴磁电阻角度传感器，其特征在于，所述温度传感器产生的温度信号用来相对于温度计算线性扩展峰值、所述偏移校准值和/或矢量幅度校准值。
  8. 根据权利要求1所述的一种双轴磁电阻角度传感器，其特征在于，两个正交的所述X-轴单轴磁电阻传感器和Y-轴单轴磁电阻传感器的电压输出的最大振幅近似相等。
  9. 根据权利要求1所述的一种双轴磁电阻角度传感器，其特征在于，已知的校准矢量幅度为Vp＝{Max[Vx(θ，H)]-Min[Vx(θ，H)]+Max[Vy(θ，H)]-Min[Vy(θ，H)]}/4。
  10. 根据权利要求2所述的一种双轴磁电阻角度传感器，其特征在于，所述第一偏移校准值是Vox＝{Max[Vcos(θ，H)]+Min[Vcos(θ，H)]}/2，所述第二偏移校准值是Voy＝{Max[Vsin(θ，H)]+Min[Vsin(θ，H)]}/2。
  11. 根据权利要求1所述的一种双轴磁电阻角度传感器，其特征在于，包括储存偏移值和最大振幅的校准常数的元件，所述的最大振幅的校准常数是由每一个单轴磁电阻角度传感器在所述外加磁场旋转一个360度时得到的最大和最小峰值计算而来，所述双轴磁电阻角传感器只需储存所述的峰值和所述每一个单轴磁电阻传感器用于校准的所述偏移值。
  12. 一种磁电阻角度传感器磁场测量误差校准方法，其特征在于，包括：
    通过两个正交的单轴磁电阻角度传感器检测沿相互垂直的X-轴和Y-轴方向的外加磁场；
    实时计算所述磁电阻角度传感器的沿X-轴和Y-轴的电压输出的测量的矢量幅度；
    计算已知的校准矢量幅度和所述测量的矢量幅度的差值；
    将所述的差值用
    Figure PCTCN2016070743-appb-100002
    相除以计算出信号误差；
    分别将所述信号误差加入到所述X-轴输出和Y-轴输出或从其中减去以计算校准的X-轴输出信号和校准的Y-轴的输出信号；
    计算校准的Y-轴输出信号除以校准的X-轴的输出信号所得的商的反正切以计算所述外加磁场的旋转角度。
  13. 根据权利要求12所述的方法，其特征在于，所述沿X-轴输出和Y-轴输出分别是偏移校准的X-轴电压输出和偏移校准的Y-轴电压输出，将第一偏移校准值从所述X-轴电压输出减去获得所述偏移校准的X-轴电压输出；将第二偏移校准值从所述Y-轴电压输出减去获得所述的偏移校准的Y-轴电压输出。
  14. 根据权利要求12所述的方法，其特征在于，所述沿X-轴电压输出被第一已知的矢量幅度校准值相除，所述沿Y-轴电压输出被第二已知的矢量幅度校准值相除，并且所述第一已知的矢量幅度校准值和第二已知的矢量幅度校准值设定为1。
  15. 根据权利要求13所述的方法，其特征在于，所述偏移校准的X-轴电压输出被第一已知的矢量幅度校准值相除，所述偏移校准的Y-轴电压输出被第二已知的矢量幅度校准值相除，并且所述第一已知的矢量幅度校准值和第二已知的矢量幅度校准值设定为1。
  16. 根据权利要求12-15中任意一项所述的方法，其特征在于，峰值、所述偏移校准值和/或矢量幅度校准值相对于温度线性扩展。
  17. 根据权利要求12所述的方法，其特征在于，所述两个正交的X-轴单轴磁电阻传感器和Y-轴单轴磁电阻传感器的电压输出的最大振幅近似相等。
  18. 根据权利要求12所述的方法，其特征在于，所述已知的校准矢量幅度为Vp＝{Max[Vx(θ，H)]-Min[Vx(θ，H)]+Max[Vy(θ，H)]-Min[Vy(θ，H)]}/4。
  19. 根据权利要求13所述的方法，其特征在于，所述第一偏移校准值是Vox＝{Max[Vcos(θ，H)]+Min[Vcos(θ，H)]}/2，所述第二偏移校准值是Voy＝{Max[Vsin(θ，H)]+Min[Vsin(θ，H)]}/2。
  20. 根据权利要求12所述的方法，其特征在于，储存偏移值和最大振幅的校准常数，所述的最大振幅的校准常数是由每一个单轴磁电阻角度传感器在所述外加磁场旋转一个360度时得到的最大和最小峰值计算而来，所述磁电阻角传感器只需储存所述的峰值和所述每一个单轴磁电阻传感器用于校准的所述偏移值。
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