Direct floor height measurement for biped walking robot by fisheye stereo

A method to measure the floor height around the current foothold by using fisheye stereo directed forward is proposed. The pose of fisheye stereo is first estimated from the input image, and the input images are partially rectified so that the floor images are projected onto the base floor which is the flat plane including the current foothold. This particular rectification not only makes the stereo matching easy and reliable but also enables to calculate the floor height directly from the image disparities. Since the method uses no coordinate conversion, the error arising when any measurement based on the sensor coordinate system is converted to world coordinate system through robot kinematics and so on is avoided. The experimental results show that the floor height measurements by the proposed method are quite stable against the pose changes of fisheye stereo.