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Sensor data checking

  • checking orientation sensor data

The orientation sensor contains roll, pitch and yaw three values. Actually it is not a hardware output, it is calculated by accelerometer and magnetometer. Some smartphone systems may contain the method getRotationMatrix and getOrientation to calculate the orientation, so if we have got the orientation data, we need to make sure it's available, below show the steps how to do these:

Suppose we have got the orientation (57.221,-0.543, 143.2) and the corresponding gravity (0.041, 8.248, 5.311), then using the follow code:

#include <iostream>
#include <Eigen/Dense>
#include <math/Quaternions.cpp>
using namespace std;

Eigen::Vector3d e(57.221,-0.543, 143.2);
Quaternions quaternions;
Eigen::Vector4d q = quaternions.GetQFromEuler(e);
Eigen::MatrixXd dcm = quaternions.GetDCMFromQ(q);
Eigen::Vector3d gb(0.041, 8.248, 5.311);
Eigen::Vector3d gn = dcm * gb;
cout << gn.transpose() << endl;

The code above doing three things:

  1. convert the orientation into quaternion.
  2. convert the quaternion into direction cosine matrix(DCM).
  3. using the DCM to rotate the gravity.

We can see the output vector is (0.0415164,-0.0312637,9.80995), that means we succeed in rotating the gravity from body frame to navigation frame using the orientation data.

Because the gravity in navigation frame should always similar to (0,0,g), so we can say that the orientation data is available if it can rotate the origin gravity data into (0,0,g).

  • checking magnetometer sensor data

  • checking accelerometer sensor data

  • checking gyroscope sensor data