A novel method of attitude measurement for floated inertial platform using optical sensors

This paper presents a novel method to measure the attitude of the vehicle navigated by the floated inertial platform. Due to the non-contact characteristic between the sphere and the shell, eight optical sensors are mounted in the suspension pads and used to measure the rotation of the shell relative to the static sphere. The measurement is the arc derived from the rotational shell sweeping over the optical sensor. During a single rotation of the shell, a quarternion is formed by the rotational axis and angle derived from the outputs of the optical sensors. Based on this quarternion, iterating the recursion formula of the quarternion can calculate the quarternion from the initial moment to the arbitrary moment, which is used to compute the attitude angles of the shell according to the specified rotation sequence. Based on this method, a corresponding approach is proposed to identify the real measurement coordinate frame of the optical sensor. The simulation results denote that the actual measurement coordinate frame can be identified with high accuracy and faster maneuvers produce faster convergence of the estimate. The availability and precision of this attitude measurement method are demonstrated in the cases of the shell rotating in a simple sequence and a complex one.