The Cougar's Robot Design Proposal for MoonBots: A Google Lunar X PRIZE LEGO MINDSTORMS Challenge. Please scroll to the bottom to download the Cougar Rover in Lego Digital Designer.
Our robot has a four wheel drive system. One motor controls four wheel steering and one controls the four wheel power. Two worm gears powered off one motor raise and lower the arm. A continuous motor powers the scoop that picks up the rings. The motor can be turned on and off by an infrared link. It has a mount for a camera that is built off the brick. The robot barely fits in the footprint. It has a touch, EOPD, compass, infrared sensors. The touch sensor is on the back to find walls. The EOPD is on the tool so that it can be close to the ground. The infrared sensor is to control the continuous motor. The compass must be far away from everything so it is on a tower.
Below are pictures of our prototype side-by-side with output from Lego Digital Designer.
The Cougar Rover - side view
The ring retrieval tool is fully raised so that the robot fits in base. The sensor on the left side of the tool (and the left edge of the photo) is an EOPD sensor (Electro-Optical Proximity Detector) that will help us find things close to the ground. On top of the "antenna" is a compass sensor that will help us know which way the robot is facing. On the back of the robot is a touch sensor. So we can back up into things like the walls of the field to help figure out exactly where the robot is. The 4th sensor port drives an IR-Link Sensor which allows the NXT brick to control the Power Functions motors via an infrared receiver.
The Cougar Rover has 4 wheel drive and 4 wheel steering.
A single NXT motor is connected via chain to the forward and rear axles (the gears at the extreme ends of the robot) Those axles transmit power to drive heads above each drive wheel. The power is then transmitted down through the center of the turntable and finally to the drive axle attached to the wheel.
Another NXT motor controls the steering. The front and rear wheels steer in opposite directions making the Cougar Rover highly maneuverable. The wheels do scrub a bit. We canned the idea of a differential because we would lose traction any time a wheel might come off of the ground while climbing over obstacles. We also investigated ackerman steering options but the added complexity outweighed any advantages.
Here the Cougar Rover has begun to deply the ring retrieval tool. We can also aim the EOPD by raising and lowering the tool or arm.
Here the Cougar Rover has fully lowered the ring tool and is ready to scoop up ice/water or
The Cougar Rover, right front view, camera mounted on robot
Cougar Rover, left rear view, showing the touch sensor.
Cougar Rover, right rear view. You can get a good look at the gearboxes that help raise the ring tool.
Detail of the part of the drive train that goes through the steering mechanism.
Detail of the gearboxes and drive train that raise and lower the ring tool. These gearboxes and the chain were not available in Lego Digital Designer.
Here is how a ring retrieval process should work. The Cougar Rover will lower his arm, spin the brushes, and then raise the tool again.