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author | Hyon Lim (Retina) <limhyon@gmail.com> | 2013-05-29 00:29:31 +1000 |
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committer | Hyon Lim (Retina) <limhyon@gmail.com> | 2013-05-29 00:34:21 +1000 |
commit | cc6c590af062d80681430fa5139837c87fbd72f0 (patch) | |
tree | 5465b65713e7e67d6226017f95102c2fcfcc9778 /src/modules/attitude_estimator_so3_comp | |
parent | 13faf0d55526c65e33ec62546f106ecb5395a9c5 (diff) | |
download | px4-firmware-cc6c590af062d80681430fa5139837c87fbd72f0.tar.gz px4-firmware-cc6c590af062d80681430fa5139837c87fbd72f0.tar.bz2 px4-firmware-cc6c590af062d80681430fa5139837c87fbd72f0.zip |
I finished to implement nonlinear complementary filter on the SO(3).
The previous problem was roll,pitch and yaw angle from quaternion.
Now it is fixed. 1-2-3 Euler representation is used.
Also accelerometer sign change has been applied.
Diffstat (limited to 'src/modules/attitude_estimator_so3_comp')
-rwxr-xr-x | src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_main.cpp | 176 |
1 files changed, 120 insertions, 56 deletions
diff --git a/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_main.cpp b/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_main.cpp index 28fcf0369..9bb749caf 100755 --- a/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_main.cpp +++ b/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_main.cpp @@ -1,7 +1,19 @@ /* + * Author: Hyon Lim <limhyon@gmail.com, hyonlim@snu.ac.kr> + * * @file attitude_estimator_so3_comp_main.c * - * Nonlinear SO3 filter for Attitude Estimation. + * Implementation of nonlinear complementary filters on the SO(3). + * This code performs attitude estimation by using accelerometer, gyroscopes and magnetometer. + * Result is provided as quaternion, 1-2-3 Euler angle and rotation matrix. + * + * Theory of nonlinear complementary filters on the SO(3) is based on [1]. + * Quaternion realization of [1] is based on [2]. + * Optmized quaternion update code is based on Sebastian Madgwick's implementation. + * + * References + * [1] Mahony, R.; Hamel, T.; Pflimlin, Jean-Michel, "Nonlinear Complementary Filters on the Special Orthogonal Group," Automatic Control, IEEE Transactions on , vol.53, no.5, pp.1203,1218, June 2008 + * [2] Euston, M.; Coote, P.; Mahony, R.; Jonghyuk Kim; Hamel, T., "A complementary filter for attitude estimation of a fixed-wing UAV," Intelligent Robots and Systems, 2008. IROS 2008. IEEE/RSJ International Conference on , vol., no., pp.340,345, 22-26 Sept. 2008 */ #include <nuttx/config.h> @@ -46,7 +58,13 @@ static bool thread_running = false; /**< Deamon status flag */ static int attitude_estimator_so3_comp_task; /**< Handle of deamon task / thread */ static float q0 = 1.0f, q1 = 0.0f, q2 = 0.0f, q3 = 0.0f; /** quaternion of sensor frame relative to auxiliary frame */ static float gyro_bias[3] = {0.0f, 0.0f, 0.0f}; /** bias estimation */ -static float gravity_vector[3] = {0.0f,0.0f,0.0f}; /** estimated gravity vector */ +static bool bFilterInit = false; + +//! Auxiliary variables to reduce number of repeated operations +static float q0q0, q0q1, q0q2, q0q3; +static float q1q1, q1q2, q1q3; +static float q2q2, q2q3; +static float q3q3; //! Serial packet related static int uart; @@ -150,29 +168,77 @@ float invSqrt(float number) { return y; } +//! Using accelerometer, sense the gravity vector. +//! Using magnetometer, sense yaw. +void MahonyAHRSinit(float ax, float ay, float az, float mx, float my, float mz) +{ + float initialRoll, initialPitch; + float cosRoll, sinRoll, cosPitch, sinPitch; + float magX, magY; + float initialHdg, cosHeading, sinHeading; + + initialRoll = atan2(-ay, -az); + initialPitch = atan2(ax, -az); + + cosRoll = cosf(initialRoll); + sinRoll = sinf(initialRoll); + cosPitch = cosf(initialPitch); + sinPitch = sinf(initialPitch); + + magX = mx * cosPitch + my * sinRoll * sinPitch + mz * cosRoll * sinPitch; + + magY = my * cosRoll - mz * sinRoll; + + initialHdg = atan2f(-magY, magX); + + cosRoll = cosf(initialRoll * 0.5f); + sinRoll = sinf(initialRoll * 0.5f); + + cosPitch = cosf(initialPitch * 0.5f); + sinPitch = sinf(initialPitch * 0.5f); + + cosHeading = cosf(initialHdg * 0.5f); + sinHeading = sinf(initialHdg * 0.5f); + + q0 = cosRoll * cosPitch * cosHeading + sinRoll * sinPitch * sinHeading; + q1 = sinRoll * cosPitch * cosHeading - cosRoll * sinPitch * sinHeading; + q2 = cosRoll * sinPitch * cosHeading + sinRoll * cosPitch * sinHeading; + q3 = cosRoll * cosPitch * sinHeading - sinRoll * sinPitch * cosHeading; + + // auxillary variables to reduce number of repeated operations, for 1st pass + q0q0 = q0 * q0; + q0q1 = q0 * q1; + q0q2 = q0 * q2; + q0q3 = q0 * q3; + q1q1 = q1 * q1; + q1q2 = q1 * q2; + q1q3 = q1 * q3; + q2q2 = q2 * q2; + q2q3 = q2 * q3; + q3q3 = q3 * q3; +} + void MahonyAHRSupdate(float gx, float gy, float gz, float ax, float ay, float az, float mx, float my, float mz, float twoKp, float twoKi, float dt) { float recipNorm; - float q0q0, q0q1, q0q2, q0q3, q1q1, q1q2, q1q3, q2q2, q2q3, q3q3; float halfex = 0.0f, halfey = 0.0f, halfez = 0.0f; - - // Auxiliary variables to avoid repeated arithmetic - q0q0 = q0 * q0; - q0q1 = q0 * q1; - q0q2 = q0 * q2; - q0q3 = q0 * q3; - q1q1 = q1 * q1; - q1q2 = q1 * q2; - q1q3 = q1 * q3; - q2q2 = q2 * q2; - q2q3 = q2 * q3; - q3q3 = q3 * q3; + //! Make filter converge to initial solution faster + //! This function assumes you are in static position. + //! WARNING : in case air reboot, this can cause problem. But this is very + //! unlikely happen. + if(bFilterInit == false) + { + MahonyAHRSinit(ax,ay,az,mx,my,mz); + bFilterInit = true; + } + //! If magnetometer measurement is available, use it. if((mx == 0.0f) && (my == 0.0f) && (mz == 0.0f)) { - float hx, hy, bx, bz; + float hx, hy, hz, bx, bz; float halfwx, halfwy, halfwz; // Normalise magnetometer measurement + // Will sqrt work better? PX4 system is powerful enough? recipNorm = invSqrt(mx * mx + my * my + mz * mz); mx *= recipNorm; my *= recipNorm; @@ -181,8 +247,9 @@ void MahonyAHRSupdate(float gx, float gy, float gz, float ax, float ay, float az // Reference direction of Earth's magnetic field hx = 2.0f * (mx * (0.5f - q2q2 - q3q3) + my * (q1q2 - q0q3) + mz * (q1q3 + q0q2)); hy = 2.0f * (mx * (q1q2 + q0q3) + my * (0.5f - q1q1 - q3q3) + mz * (q2q3 - q0q1)); + hz = 2 * mx * (q1q3 - q0q2) + 2 * my * (q2q3 + q0q1) + 2 * mz * (0.5 - q1q1 - q2q2); bx = sqrt(hx * hx + hy * hy); - bz = 2.0f * (mx * (q1q3 - q0q2) + my * (q2q3 + q0q1) + mz * (0.5f - q1q1 - q2q2)); + bz = hz; // Estimated direction of magnetic field halfwx = bx * (0.5f - q2q2 - q3q3) + bz * (q1q3 - q0q2); @@ -203,7 +270,7 @@ void MahonyAHRSupdate(float gx, float gy, float gz, float ax, float ay, float az recipNorm = invSqrt(ax * ax + ay * ay + az * az); ax *= recipNorm; ay *= recipNorm; - az *= recipNorm; + az *= recipNorm; // Estimated direction of gravity and magnetic field halfvx = q1q3 - q0q2; @@ -254,6 +321,18 @@ void MahonyAHRSupdate(float gx, float gy, float gz, float ax, float ay, float az q1 *= recipNorm; q2 *= recipNorm; q3 *= recipNorm; + + // Auxiliary variables to avoid repeated arithmetic + q0q0 = q0 * q0; + q0q1 = q0 * q1; + q0q2 = q0 * q2; + q0q3 = q0 * q3; + q1q1 = q1 * q1; + q1q2 = q1 * q2; + q1q3 = q1 * q3; + q2q2 = q2 * q2; + q2q3 = q2 * q3; + q3q3 = q3 * q3; } void send_uart_byte(char c) @@ -630,44 +709,29 @@ const unsigned int loop_interval_alarm = 6500; // loop interval in microseconds uint64_t timing_start = hrt_absolute_time(); - MahonyAHRSupdate(gyro[0],gyro[1],gyro[2],acc[0],acc[1],acc[2],mag[0],mag[1],mag[2],so3_comp_params.Kp,so3_comp_params.Ki, dt); - - float aSq = q0*q0; // 1 - float bSq = q1*q1; // 2 - float cSq = q2*q2; // 3 - float dSq = q3*q3; // 4 - float a = q0; - float b = q1; - float c = q2; - float d = q3; - - Rot_matrix[0] = 2*aSq - 1 + 2*bSq; // 11 - //Rot_matrix[1] = 2.0 * (b * c - a * d); // 12 - //Rot_matrix[2] = 2.0 * (a * c + b * d); // 13 - Rot_matrix[3] = 2.0 * (b * c - a * d); // 21 - //Rot_matrix[4] = aSq - bSq + cSq - dSq; // 22 - //Rot_matrix[5] = 2.0 * (c * d - a * b); // 23 - Rot_matrix[6] = 2.0 * (b * d + a * c); // 31 - Rot_matrix[7] = 2.0 * (c * d - a * b); // 32 - Rot_matrix[8] = 2*aSq - 1 + 2*dSq; // 33 - - gravity_vector[0] = 2*(q1*q3-q0*q2); - gravity_vector[1] = 2*(q0*q1+q2*q3); - gravity_vector[2] = aSq - bSq - cSq + dSq; - - //euler[0] = atan2f(Rot_matrix[7], Rot_matrix[8]); - //euler[1] = -asinf(Rot_matrix[6]); - //euler[2] = atan2f(Rot_matrix[3],Rot_matrix[0]); - - // Euler angle directly from quaternion. - euler[0] = -atan2f(gravity_vector[1], sqrtf(gravity_vector[0]*gravity_vector[0] + gravity_vector[2]*gravity_vector[2])); // roll - euler[1] = atan2f(gravity_vector[0], sqrtf(gravity_vector[1]*gravity_vector[1] + gravity_vector[2]*gravity_vector[2])); // pitch - euler[2] = -atan2f(2*(q1*q2-q0*q3),2*(q0*q0+q1*q1)-1); // yaw - - //euler[2] = atan2(2 * q1*q2 - 2 * q0*q3, 2 * q0*q0 + 2 * q1*q1 - 1); // psi - //euler[1] = -asin(2 * q1*q3 + 2 * q0*q2); // theta - //euler[0] = atan2(2 * q2*q3 - 2 * q0*q1, 2 * q0*q0 + 2 * q3*q3 - 1); // phi - + // NOTE : Accelerometer is reversed. + // Because proper mount of PX4 will give you a reversed accelerometer readings. + MahonyAHRSupdate(gyro[0],gyro[1],gyro[2],-acc[0],-acc[1],-acc[2],mag[0],mag[1],mag[2],so3_comp_params.Kp,so3_comp_params.Ki, dt); + + // Convert q->R. + Rot_matrix[0] = q0q0 + q1q1 - q2q2 - q3q3;// 11 + Rot_matrix[1] = 2.0 * (q1*q2 + q0*q3); // 12 + Rot_matrix[2] = 2.0 * (q1*q3 - q0*q2); // 13 + Rot_matrix[3] = 2.0 * (q1*q2 - q0*q3); // 21 + Rot_matrix[4] = q0q0 - q1q1 + q2q2 - q3q3;// 22 + Rot_matrix[5] = 2.0 * (q2*q3 + q0*q1); // 23 + Rot_matrix[6] = 2.0 * (q1*q3 + q0*q2); // 31 + Rot_matrix[7] = 2.0 * (q2*q3 - q0*q1); // 32 + Rot_matrix[8] = q0q0 - q1q1 - q2q2 + q3q3;// 33 + + //1-2-3 Representation. + //Equation (290) + //Representing Attitude: Euler Angles, Unit Quaternions, and Rotation Vectors, James Diebel. + // Existing PX4 EKF code was generated by MATLAB which uses coloum major order matrix. + euler[0] = atan2f(Rot_matrix[5], Rot_matrix[8]); //! Roll + euler[1] = -asinf(Rot_matrix[2]); //! Pitch + euler[2] = atan2f(Rot_matrix[1],Rot_matrix[0]); //! Yaw + /* swap values for next iteration, check for fatal inputs */ if (isfinite(euler[0]) && isfinite(euler[1]) && isfinite(euler[2])) { /* Do something */ |