Our Robot
The LegoAces robot uses the fundamental design principle of simplicity combined with accurate sensing to insure mission success in exploring the MoonBots challenge.
The Drive Train and overall design employs a high ground clearance 4 wheel drive chassis with tank-drive steering. Treads and various wheels were evaluated to see which ones could best cross the graters and ridges and most accurately navigate the moon surface. The wheels chosen are large Lego Motorcycle wheels. These wheels were not available in the Lego CAD model software and were left off so that the underlying mechanics of the chassis can be seen better in the model.
The Actuator used to pick up the science target loops is an articulated arm that drops into a storage box on the robot for transportation. The three prong fork arm is hinged so that the loops are "slam-dunked" into the box after they are picked up. In addition, the robot has two special side wing outriggers that are deployed out each side of the robot to pick up the final two loops in the large crater on the way back to base. These outriggers are stored on the side of the robot and are actuated by backing against the wall near the peak of eternal light. A latch mechanism allows the outriggers to stay stored compactly when on the lander base and pop out the sides and drop down to pick up the final loops. This actuation makes the robot wide enough to pick up all the loops in the large crater and drag them back to base.
Accurate navigation is accomplished by using a combination of sensor inputs and positive alignment on the MoonBots board to guarantee position. The robot uses two ultrasonic distance sensors and a compass to navigate. The ultrasonic sensors are placed at a 45 degree angle facing forward and facing backwards to enable precise ultrasonic wall-following and distance measurement. At many times in the drive the robot uses the sensors to check position in distance from a wall and adjust if necessary to insure precise alignment. The robot also uses a compass sensor for most of the turns. A turn to compass heading function is used to reduce inaccuracy of slippage between the wheels and the surface. Another critical navigation mechanism is physical alignment on crater walls. Before picking up loops or when crossing the ridge, the robot creeps up on the physical parts of the moonscape at very low power. The low power setting allows the robot to push up against a crater without crossing it to reset the sensors and insure positive alignment.
This design combining robust chassis design, innovative actuators to grab the loops and reliable sensing to guarantee position combined to make a very successful robot. In development trials, the robot is able to consistently score 350 points by accomplishing all mission objectives.