Ok, so I have my Arduino hooked up to an MPU-6050 6-axis gyro+accelerometer GY-521 breakout board. I've got it sending serial data to a program on my computer, all working perfectly. I'll pose this question in C++ even though my program is written in DBPro.
I'm currently using a complementary filter to combine the gyro rates of angular rotation with the accelerometer gravity vector for stable yet responsive rotations. Here's my current code:
angleX=0.98*(angleX+(gyroX/16.4)*timeMultiplier)+0.02*atanfull(accelY,accelZ)
angleY=0.98*(angleY+(gyroY/16.4)*timeMultiplier)+0.02*atanfull(accelZ,accelX)
angleZ=0.98*(angleZ+(gyroZ/16.4)*timeMultiplier)+0.02*atanfull(accelX,accelZ)
angleX/Y/Z and timeMultiplier are floats. timeMultiplier is basically (millis()-lastMillis)/1000.0. atanfull is basically atan2 but outputs in degrees (0-360), not radians (I think that's the only difference).
The issue is that when the board is sitting flat on the table, the accelerometer obviously can't measure rotations about the Y axis (up), but the gyro can. When I twist the board around Y, the 3D cube representation I'm rendering twists for a second then is pulled back to 0. That's because when the board is upright (with the Y axis pointing upwards) the atanfull results in 0.
What I've been scouring the internet for (but really don't know what to search) is a way to reduce the affect of the accelerometer data the less use it becomes. So as the X axis, say, is rotated so it's perpendicular to the ground (and becomes useless for measurements) the gyro is allowed more and more control, until when the X axis becomes fully perpendicular the gyro is taking no notice of the accelerometer for that axis and relies fully on the gyro.
TL;DR: I'm trying to find a way to combine gyro and accelerometer readings in a rotation-independent way. That is, all the implementations of gyro+accel complementary filters I can find handle pitch/roll differently to yaw, and I don't want to do that. I want to be able to turn my board in any direction and still get good readings.
I really have no idea what I should be searching for to find out how to do this, and would appreciate any help :)
