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I have a CMRotationMatrix *rot and i would like to get the pitch, yaw, roll from the matrix. Any ideas how i could do that?
Thanks
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magx = magnetometer[0]*cos(pitch)+magnetometer[1]*sin(roll)*sin(pitch) + magnetometer[2]*sin(pitch)*cos(roll); magy = -magnetometer[1]*cos(roll) + magnetometer[2]*sin(roll); yaw = atan2(-magy,magx)*180/M_PI; I'm getting incorrect yaw data but I'm not sure about the equations which I found on the internet.
Yaw velocity can be measured by measuring the ground velocity at two geometrically separated points on the body, or by a gyroscope, or it can be synthesized from accelerometers and the like. It is the primary measure of how drivers sense a car's turning visually.
XYZ Roll-Pitch-Yaw Angles in Robotics In the previous lesson, we learned about Euler angles, and we saw that Euler angles refer to the angles in a sequence of rotations in a body-fixed frame. On the other hand, the roll-pitch-yaw angles are a sequence of rotations about axes of the space frame.
Its better to use the Quaternion than Euler angles.... The roll, pitch and yaw values can be derived from quaternion using these formulae:
roll = atan2(2*y*w - 2*x*z, 1 - 2*y*y - 2*z*z)
pitch = atan2(2*x*w - 2*y*z, 1 - 2*x*x - 2*z*z)
yaw = asin(2*x*y + 2*z*w)
It can be implemented as:
CMQuaternion quat = self.motionManager.deviceMotion.attitude.quaternion;
myRoll = radiansToDegrees(atan2(2*(quat.y*quat.w - quat.x*quat.z), 1 - 2*quat.y*quat.y - 2*quat.z*quat.z)) ;
myPitch = radiansToDegrees(atan2(2*(quat.x*quat.w + quat.y*quat.z), 1 - 2*quat.x*quat.x - 2*quat.z*quat.z));
myYaw = radiansToDegrees(asin(2*quat.x*quat.y + 2*quat.w*quat.z));
where the radianstoDegrees is a preprocessor directive implemented as:
#define radiansToDegrees(x) (180/M_PI)*x
This is done to convert the radian values given by the formulae, to degrees.
More information about the conversion can be found here: tinkerforge and here:Conversion between Quaternions and Euler angles.
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pitch, yaw, roll from the matrix. Any ideas how i could do that?
In which order? Pitch, yaw and roll, commonly called Euler angles, don't represent rotations unambigously. Depending on the order you carry out the individual sub-rotations you end up with completely different rotation matrices.
My personal recommendation: Don't use Euler angles at all, they just call for (numerical) trouble. Use a matrix (you already do) or a quaternion.
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