Camera Image Based Moving Platform Rotation Estimation for Quadrotor Landing

This paper considers the 3D rotation estimation of a moving platform from 2D images captured by a camera. Assume that a circular pattern marker is on the flight deck of a ship and quadrotor hovers on the center of a platform. The quadrotor has a camera that captures 2D images of markers and measures the distance between markers. The circular pattern of markers changes to an ellipse as the platform rotates. The ellipse equation can be derived from marker positions on an ellipse, and a platform's rotation sequence can be determined by leveraging geometry and trigonometric functions. As the platform's rotation can be estimated, the quadrotor is able to decide the timing that platform rotation is within the quadrotor's capacity to land safely. A simulation and a hardware test were performed to verify the estimation method, and the estimation error was discussed.