On quaternion update algorithm

Space vehicle attitude control system performance using a strapdown inertial measurement unit is often limited by the computational burden of the digital computer. The application of quaternion to digital attitude transformation can reduce computation time. This thesis presents two update algorithms using quaternions. These algorithms have a simple expression, and do not involve any trigonometric functions. These algorithms are compared by means of digital simulation test. The first algorithm, developed from the algebra of quaternion, yields higher accuracy than the second algorithm; the second algorithm, derived from the quaternion differential equations, produce a less deviation of unity norm compared to the first.