offlineVQF

void offlineVQF(const vqf_real_t gyr[], const vqf_real_t acc[], const vqf_real_t mag[], size_t N, vqf_real_t Ts, const VQFParams &params, vqf_real_t out6D[], vqf_real_t out9D[], vqf_real_t outDelta[], vqf_real_t outBias[], vqf_real_t outBiasSigma[], bool outRest[], bool outMagDist[])

A Versatile Quaternion-based Filter for IMU Orientation Estimation.

This function implements the offline variant of orientation estimation filter described in the following publication:

D. Laidig and T. Seel. “VQF: Highly Accurate IMU Orientation Estimation with Bias Estimation and Magnetic Disturbance Rejection.” Information Fusion 2023, 91, 187–204. doi:10.1016/j.inffus.2022.10.014. [Accepted manuscript available at arXiv:2203.17024.]

The filter can perform simultaneous 6D (magnetometer-free) and 9D (gyr+acc+mag) sensor fusion and can also be used without magnetometer data. It performs rest detection, gyroscope bias estimation during rest and motion, and magnetic disturbance detection and rejection.

To use this offline implementation, all data must have the same sampling rate and be available in (row-major) data buffers. Similar to VQF::updateBatch(), the output pointer arguments must be null pointers or point to sufficiently large data buffers.

This function is the C++ implementation of the offline variant. The offline variant makes use of the fact that the whole data is available and performs acausal signal processing, i.e. future samples are used to calculate the current estimate. Depending on use case and programming language of choice, the following alternatives might be useful:

Full Version

Basic Version

Offline Version

C++

VQF

BasicVQF

offlineVQF (this function)

Python/C++ (fast)

vqf.VQF

vqf.BasicVQF

vqf.offlineVQF()

Pure Python (slow)

vqf.PyVQF

–

–

Pure Matlab (slow)

VQF.m

–

–

Parameters:

  • gyr – gyroscope measurement in rad/s (N*3 elements, must not be null)

  • acc – accelerometer measurement in m/s² (N*3 elements, must not be null)

  • mag – magnetometer measurement in arbitrary units (N*3 elements, can be a null pointer)

  • N – number of samples

  • Ts – sampling time in seconds

  • params – parameters (pass VQFParams() to use the default parameters and see VQFParams for a full list and detailed descriptions)

  • out6D – output buffer for the 6D quaternion (N*4 elements, can be a null pointer)

  • out9D – output buffer for the 9D quaternion (N*4 elements, can be a null pointer)

  • outDelta – output buffer for heading difference angle (N elements, can be a null pointer)

  • outBias – output buffer for the gyroscope bias estimate (N*3 elements, can be a null pointer)

  • outBiasSigma – output buffer for the bias estimation uncertainty (N elements, can be a null pointer)

  • outRest – output buffer for the rest detection state (N elements, can be a null pointer)

  • outMagDist – output buffer for the magnetic disturbance state (N elements, can be a null pointer)