At at the Jožef Stefan Institute in Slovenia they designed a special 3 degrees of freedom robot dedicated for skiing using the carving technique.
The robot has a complex sensory and control system that assures stabilization on the ski slope during skiing and tracks a path marked with race gates and avoids obstacles.
The robot is controlled with a hierarchically built multi processor computer system. The upper level controller is used for navigation, vision processing and decision making. The upper level controller communicates with a GPS receiver and an USB based camera. The low level controller deals with skier stability, joint control and receives information from the sensory system comprised of an electronic gyroscope, force sensors mounted between the skis and robot legs and the motor position sensors.
Vision processing was accomplished using a single camera with a view angle of 78 degrees. "With an image size of 320 x 200 pixels we were able to obtain the object recognition and localization at 30 fps. The distance between the current robot position and the next gate was calculated using the camera orientation and the estimated size of the gate mark. We used blue and red gate fences, respectively. The color defined whether the robot-skier should approach them from the left or from the right side depending on the color. The desired turn radii were estimated from the localization information, and the angular acceleration. The velocity in the sagittal plane was obtained by the GPS sensor with an accuracy of 0.1 m/s and sample time of 0.25 s.," the team said.
They performed several experimental runs on the ski slope. Their experiments showed that the robot was able to follow the desired path marked by any combination of four race gates providing that the distance between the gates allowed the robot to execute the turn.