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Abstract
Circular feature has been widely applied in recognising moving object and estimating its position and orientation. Based on the principle of perspective projection, the rotational motion of circular feature was analysed. According to whether the rotational motion occurred in the plane of circular feature, the rotational motion could be classified into two types: in-plane rotation and non-in-plane rotation. For the convenience of computation, we set the camera’s initial position and orientation. The optical axis of camera was set perpendicular to the plane of circular feature. We analysed the perspective distortion of the circular feature. Additionally, based on the geometrical reasoning, we also proposed the method of computing the rotation angles. Finally, some experiments were carried to verify correctness and feasibility of the computing method. The results showed that the measurement of rotation angle could achieve better performance though the error existed. The maximum value of errors was only 0·4°. The average errors and the standard deviations of errors were also small.