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CN-121994218-A - IMU accelerometer module length out-of-tolerance inhibition method based on constraint

CN121994218ACN 121994218 ACN121994218 ACN 121994218ACN-121994218-A

Abstract

A constraint-based IMU accelerometer module length out-of-tolerance suppression method comprises the steps of 1, starting, powering on an IMU, outputting original data of an accelerometer and a gyroscope, setting an accelerometer module length constraint identification position and a maximum out-of-tolerance threshold value and a small out-of-tolerance threshold value of the accelerometer module length out-of-tolerance, 2, directly outputting the original data of the accelerometer and the gyroscope if the module length constraint identification position is invalid, such as the about bundle identification position is valid, triggering the module length constraint identification position, calculating an accelerometer module length difference value, 3, if the module length difference value is larger than a maximum threshold value, reporting a fault, and when the module length difference value is smaller than a minimum threshold value, setting the accelerometer zero offset to zero, outputting an original accelerometer observation result, 4, when the module length difference value is between the maximum threshold value and the small threshold value, entering dynamic and static state, carrying out accelerometer module length constraint, 5, carrying out normalization processing on the accelerometer output, respectively calculating zero offset value to be corrected by three axes, and outputting the accelerometer measurement value after correction. According to the invention, the function of the length constraint of the accelerometer module under any static state can be realized, the size of each vector is changed before and after correction, the direction is unchanged, and the size of each vector is the same as that of the gravity acceleration of 1 g.

Inventors

  • ZHANG YANMEI
  • LI LINXIANG
  • WAN ZIXIANG

Assignees

  • 上海华依智造感知科技有限公司

Dates

Publication Date
20260508
Application Date
20251219

Claims (9)

  1. 1. The method for suppressing the out-of-tolerance of the module length of the IMU accelerometer based on the constraint is characterized by comprising the following steps of: Step 1. Starting, powering up the IMU, outputting the original data of linear accelerations (acc_x, acc_y, acc_z) and angular velocities (gyro_x, gyro_y, gyro_z) of the XYZ three axes of the accelerometer, Configuring a parameter file, setting a maximum and minimum out-of-tolerance threshold value of the accelerometer module length constraint identification bit and the accelerometer module length out-of-tolerance, Step 2, if the algorithm entrance finds that the accelerometer module length constraint identification bit is invalid, the accelerometer directly sends the original data of the output accelerometer and the gyroscope, If the accelerometer constraint flag is valid, triggering the accelerometer module length constraint flag, calculating an accelerometer module length difference, The accelerometer module length is equal to the sum of squares of the accelerometer measurements of the three axes, the root number, , Norm, the length of the die, Acc_x, acc_y, acc_z represent acceleration measurements of the three axes of the accelerometer XYZ, The actual module length at rest is equal to g (earth gravitational acceleration constant), the difference between the two is the module length difference, Calculating the current acceleration module length : If the deviation is 1g, normalization processing is carried out: , , Step 3, if the module length difference value of the accelerometer is larger than the maximum out-of-tolerance threshold value, directly reporting a fault; if the accelerometer module difference is less than the minimum out-of-tolerance threshold, the accelerometer is directly zero-biased, Outputting linear accelerations (acc_x, acc_y, acc_z) of the XYZ three axes of the original accelerometer, Step4, when the calculated module length difference value of the accelerometer is between the minimum out-of-tolerance threshold value and the maximum out-of-tolerance threshold value, the dynamic and static judgment of the IMU is carried out: When the IMU is in a dynamic state, the IMU is not processed and ignored; When the IMU is in a static state, accelerometer mode length constraint is performed: And 5, carrying out normalization processing on the output of the accelerometer, respectively calculating zero offset values required to be corrected by the three axes, and finally, correcting (zero offset value) the measured value of the accelerometer and outputting.
  2. 2. The method for suppressing the excessive die length of the IMU accelerometer based on the constraint according to claim 1 is characterized in that if the excessive die length of the IMU is 10mg and the calibration test cannot be passed, the installation angle calibration is required, and the IMU is powered on at the moment to trigger the start of the die length constraint identification bit.
  3. 3. The constraint-based IMU accelerometer module length out-of-tolerance suppression method of claim 2, wherein the minimum out-of-tolerance threshold is set to 6mg, the maximum out-of-tolerance threshold is set to 20mg, The threshold value 20mg and the 6mg low threshold value belong to common values and belong to an empirical range, but can be freely configured according to project indexes.
  4. 4. The method for suppressing the excessive module length of the IMU accelerometer based on the constraint according to claim 2, wherein the calibration angle of the installation angle is performed under the condition that dynamic and static detection is static, a module length constraint normalization program is triggered, three-axis correction zero offset is estimated, and corrected data are output.
  5. 5. The method of claim 1, wherein the method comprises the steps of, Step5, the corrected data includes: corrected accelerometer output vector , XYZ axis observation value after acceleration correction 、 、 , Corrected and original values of pitch angle 、 , Corrected and original values of roll angle 、 , Raw accelerometer output vector True accelerometer vector Is the zero offset of the accelerometer 。
  6. 6. The method of claim 5, wherein the method comprises the steps of, The algorithm and the proving process of the constraint-based IMU accelerometer module length out-of-tolerance suppression method are as follows: Accounting for corrected accelerometer output vectors : , Wherein, the Is the original accelerometer output vector, in g, earth gravitational acceleration, Is the true accelerometer vector, in g, Is the zero offset of the accelerometer, the unit is g, , G is the acceleration of the earth's gravity, Norm is the modulus of the accelerometer and, Substituting the calculation formulas of pitch and roll: Pitch calculation: , Wherein, the 、 、 The XYZ axis observations after the acceleration correction, 、 The corrected value and the original value of the pitch angle are respectively, Roll calculation: 、 the corrected value and the original value of the roll angle are respectively, = 1.000g, Is the corrected accelerometer mode length.
  7. 7. The constraint-based IMU accelerometer module length out-of-tolerance suppression method according to claim 1 is characterized in that in step 1, by enabling configuration parameter files (namely enabling an accelerometer module length constraint function, a minimum module difference threshold value and a maximum module difference threshold value), the module length constraint function of the accelerometer can be flexibly controlled by dynamic and static judgment, a more accurate initial value is provided for subsequent user estimation of zero offset, and initialization time and convergence time are shortened.
  8. 8. A method of suppressing IMU accelerometer module length out of tolerance according to claim 1, wherein in step 1, configuration parameter files are set in the sensor configuration or data processing to ensure that the measured values are within safe or effective ranges.
  9. 9. The method for suppressing the excessive length of the IMU accelerometer based on the constraint according to claim 1 is characterized in that the method is suitable for the situation that the excessive length of the accelerometer is large and the installation angle calibration cannot be entered, and is mainly used for the static coarse calibration occasion of the installation angle of the IMU.

Description

IMU accelerometer module length out-of-tolerance inhibition method based on constraint Technical Field The invention relates to detection and calibration of an Inertial Measurement Unit (IMU), in particular to a method for restraining the modular length of an Inertial Measurement Unit (IMU) accelerometer (static) and suppressing the modular length out-of-tolerance, and more particularly to a method for suppressing the modular length out-of-tolerance of the inertial measurement unit IMU accelerometer (static) by means of self-adaptive restraining. The self-checking mechanism is used for monitoring and analyzing abnormal conditions of the accelerometer (static) module length in real time after the IMU is electrified, and self-adaptive constraint is carried out on the detected abnormal conditions of the different accelerometer module lengths, so that the module length is recovered to be normal, the detection and calibration efficiency of the inertial measurement unit IMU is effectively improved, and the stability and reliability of the inertial measurement unit IMU in long-term use are improved. Background The Inertial Measurement Unit (IMU) can be subjected to strict detection and parameter calibration when leaving a factory, so that the mode length out-of-tolerance control of the accelerometer is ensured to be within a certain range, and the stability and reliability of the inertial measurement unit IMU in long-term use are effectively improved. The mode length out-of-tolerance is the absolute value of the difference between the mode length and the earth gravitational acceleration g in the rest state of the accelerometer, and is usually strictly controlled within 1mg (1 mg. Apprxeq. 0.001X 9.80 m/s 2). However, due to variations in storage environment (e.g., temperature, humidity, magnetic field, etc.) and other factors, very few IMUs may have irregular fluctuations in accelerometer module length (in a static state) after receiving a parametrically calibrated product by a customer. If the mode length out-of-tolerance of the accelerometer cannot be controlled within a certain range, namely the mode length is not matched with the earth gravity acceleration g, the correction result cannot reflect the actual gravity mode length, an additional error is introduced, and even the accelerometer output data is distorted and not available when serious, so that the output result of the IMU and the precision of the whole navigation system are affected. Such mode length overrun can only be observed in a fully stationary state of the accelerometer, and when the IMU is in motion, the mode length overrun is usually negligible because of its small order of magnitude relative to external acceleration, and therefore does not affect the normal use of the IMU. In order to ensure the stability of the accelerometer module length in the long-term use of the IMU, various large IMU manufacturers currently commonly adopt a module length constraint technology (the existing module length constraint technology is mainly used for adjusting the Z-axis acceleration value under the condition that the IMU module length is out of tolerance and is large when the IMU is static so as to reduce the whole module length to meet the requirement, or simply adjust the module length, the simple module length adjustment is only used for adjusting the Z-axis acceleration value so as to reduce the whole module length to meet the requirement.) On the other hand, the die length constraint technology can effectively work under the condition that the IMU is static and approximately horizontally placed, static data output by the accelerometer can be adjusted, in this case, the gravity acceleration direction is parallel to the measuring axis of the accelerometer, and errors can be eliminated through simple die length adjustment. However, as the usage situation of the IMU changes, and particularly as the IMU is gradually applied to the fields of robots, automobiles and the like, the situation of obliquely mounting the IMU is more and more common. In the case of IMU inclined placement, the existing mode length constraint method will not work effectively. When the IMU is in an inclined state, the gravity acceleration direction is not parallel to the measuring axis of the accelerometer, and the existing mould length constraint scheme cannot be accurately corrected. Thus, existing mold length constraint techniques can only function if the IMU is stationary and placed approximately horizontally. When the IMU is mounted at an oblique angle, existing solutions may use non-gravity direction components for correction erroneously, resulting in an offset in the accelerometer measurement direction. At this time, the correction result cannot reflect the actual gravity module length, and an additional error is introduced, so that even the accelerometer output data is distorted and unavailable in severe cases, and the output result of the IMU and the precision of the whole navig