Ratler

(the same as GIF file)

Ratler, or Robotic All Terrain Lunar Exploration Rover, is about the size of a tractor mower, with four depth-sensing (or stereo) cameras mounted on a 1.5 meter mast. It is a battery-powered, four-wheeled, skid-steered vehicle, about 1.2 meters long and wide, with fifty centimeter diameter wheels. Unlike any other robot, Ratler's body is divided into halves that rotate against each other. This articulation enables all four wheels to maintain ground contact, even when crossing uneven terrain, which increases Ratler's ability to surmount terrain obstacles. The body and wheels are made of a composite material that provides a good strength-to-weight ratio.

Sensors on Ratler include wheel encoders, turn-rate gyro, a compass, a roll inclinometer, and two pitch inclinometers (one for each body segment). There is one color teleoperation camera and we have added a camera mast and four black and white cameras for stereo vision (only two of which are currently being used). To keep the cameras' view steady while Ratler travels, we have created a motion-averaging linkage for the robot that averages the pitch of Ratler's body halves and adjusts the camera mast - mounted on a pivot bar between the two halves - accordingly. On-board computation is provided by a 286 and a 486 CPU board, connected by an STD bus, which also contains A/D boards and digitizer boards for the stereo cameras. Communication is through a 4800 baud data link and a 2.3 GHz microwave video link.