Why gyros + accelerometers + GPS + magnetometer + sonar?
It is possible to do a stability augmentation system with just the two gyros and two accelerometers (as we have done), but for control of all axes (attitude, altitude and position), more sensors are required. The error in a pure inertial position estimate is huge over time, but fairly good for short term (less than one second) solutions. The GPS position is reasonable and DGPS is fairly good, but the update frequency is very slow (1 Hz) and high-latency (> 1 second). Using both of these together allows for a better solution than either alone. • 2.2: Do I need three axes for the accelerometers? It depends what you want to do. For small angles, you can estimate attitude with the simple equation: Pitch angle = asin( -accel_y / g ) Roll angle = -asin( -accel_x / g ) However, this will introduce significant errors for angles larger than a few degrees and can not distinguish upside down from right side up. Aggressive aerobatics would not work here. • 2.3: Do I need three axes for the magneto
