<title>Motion estimation of a freely rotating body in earth orbit</title>

Abstract

This paper presents a method of providing continuous and current attitude estimates of freely rotating objects to support the grasping tasks of a flying autonomous space robot. The rotational state estimator is subdivided into two sections: the rotational dynamics equations which propagate an object's attitude, angular velocity, and angular acceleration (rotational state) in time and an extended Kalman filter which produces an estimate of the error between an object's true rotational state and its estimated rotational state. In simulation tests, the rotational state estimator is periodically provided with noisy, dated object attitude measurements from computer vision. The difference between the noisy object attitude measurement and its associated attitude estimate are the input into the extended Kalman filter. Each object attitude measurement is dated when it is received by the rotational state estimator because of necessary computer vision processing time. Using this dated attitude measurement the rotational state estimator revises its current estimate of the object's attitude to guide the robot. Results of simulation tests, showing the accuracy of the attitude estimate as different parameters vary, are presented.