Abstract: The attitude of a tiltable body is tracked and controlled on the basis of signals outputted from gyros and tilt sensors. The signals outputted from the gyros are transformed and integrated to produce estimated position information in the form of a modified quaternion in which the yaw component is constrained to a zero value. Modified quaternion information in the same form is also generated from signals outputted from the tilt sensor and is used to detect and correct an error component in the estimated position information. Gyro drift is also corrected based on the output of the tilt sensor.

Abstract: Apparatus and method for controlling a plurality of pulse width modulated devices from a single controller including condition sensors to input the controller, a logic unit to determine the error between the sensed values and the desired values of the conditions and a direct memory access unit which is digitally coded with the error values, the pulse width modulated device being connected to receive the outputs of the direct memory access unit and operable to control the conditions.