IMU
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Diff: IMUfilter.h
- Revision:
- 0:976ab2e4e4bd
- Child:
- 1:8a920397b510
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/IMUfilter.h Mon Sep 06 13:54:41 2010 +0000 @@ -0,0 +1,138 @@ +/** + * @author Aaron Berk + * + * @section LICENSE + * + * Copyright (c) 2010 ARM Limited + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + * + * @section DESCRIPTION + * + * IMU orientation filter developed by Sebastian Madgwick. + * + * Find more details about his paper here: + * + * http://code.google.com/p/imumargalgorithm30042010sohm/ + */ + +#ifndef IMU_FILTER_H +#define IMU_FILTER_H + +/** + * Includes + */ +#include "mbed.h" + +/** + * Defines + */ +#define PI 3.1415926536 + +/** + * IMU orientation filter. + */ +class IMUfilter { + +public: + + /** + * Constructor. + * + * Initializes filter variables. + * + * @param rate The rate at which the filter should be updated. + * @param gyroscopeMeasurementError The error of the gyroscope in degrees + * per second. This used to calculate a tuning constant for the filter. + * Try changing this value if there are jittery readings, or they change + * too much or too fast when rotating the IMU. + */ + IMUfilter(double rate, double gyroscopeMeasurementError); + + /** + * Update the filter variables. + * + * @param w_x X-axis gyroscope reading in rad/s. + * @param w_y Y-axis gyroscope reading in rad/s. + * @param w_z Z-axis gyroscope reading in rad/s. + * @param a_x X-axis accelerometer reading in m/s/s. + * @param a_y Y-axis accelerometer reading in m/s/s. + * @param a_z Z-axis accelerometer reading in m/s/s. + */ + void updateFilter(double w_x, double w_y, double w_z, + double a_x, double a_y, double a_z); + + /** + * Compute the Euler angles based on the current filter data. + */ + void computeEuler(void); + + /** + * Get the current roll. + * + * @return The current roll angle in radians. + */ + double getRoll(void); + + /** + * Get the current pitch. + * + * @return The current pitch angle in radians. + */ + double getPitch(void); + + /** + * Get the current yaw. + * + * @return The current yaw angle in radians. + */ + double getYaw(void); + +private: + + int firstUpdate; + + //Quaternion orientation of earth frame relative to auxiliary frame. + double AEq_1; + double AEq_2; + double AEq_3; + double AEq_4; + + //Estimated orientation quaternion elements with initial conditions. + double SEq_1; + double SEq_2; + double SEq_3; + double SEq_4; + + //Sampling period + double deltat; + + //Gyroscope measurement error (in degrees per second). + double gyroMeasError; + + //Compute beta (filter tuning constant.. + double beta; + + double phi; + double theta; + double psi; + +}; + +#endif /* IMU_FILTER_H */