2019 - Lil' Mr. P
FIRST Destination: Deep Space
Lil' Mr. P competed in Destination: Deep Space, the 2019 FRC game. In Deep Space, two alliances competed to place disks on rocket ship walls and then place balls inside of the ships. Additional points were earned for "jumping" off of the platforms at the beginning of the match, and climbing back onto the platforms at the match's end. Destination: Deep Space did not have an autonomous period at the beginning of the match, like most FRC games, but instead had a "sandstorm" period where drivers' view of the field was obscured. Drivers could still control their robots during this period using robot vision, making that an important aspect of design.
Robot overview
A CAD of Lil' Mr. P's claw may be found here.
For simplicity's sake, the Swampscott Currents decided to build a robust disk-only robot that could access the bottom levels of each rocket ship. To manipulate the disks, Lil' Mr. P employed a large, tripod-like claw which entered a disk's center and expanded outward. In addition, because climbing was an important part of the game, Lil' Mr. P was designed with three "legs," pistons that could lift the robot seven inches off of the ground. At the end of each match, Lil' Mr. P actuated his legs to climb onto the second level of the platforms. To provide clear driver vision, Lil' Mr. P had a camera mounted on a driver-controlled gimbal that could swivel in two dimensions.
Strengths:
Lil' Mr. P's gimbal camera allowed for a good view in front of the robot at all times. This allowed 4311 to successfully place disks during the sandstorm period and made aligning the robot during disk placement easier. In addition, 4311 was able to effectively play defense on the opposite end of the field, where it is often difficult to see without a robot camera.
The twisted metal supporting the camera prevented vibration, allowing a stable image at all times.
Lil' Mr. P could climb in under 10 seconds, allowing 4311 to continue scoring points or defending until the very end of the match.
Lil' Mr. P's claw mount, on the front of a piston, allowed the disk manipulator to compress/decompress and pick up disks from all angles.
Weaknesses:
Lil' Mr. P was a light robot, weighing only about 90 pounds, which made playing defense against heavy teams harder. In addition, Lil' Mr. P had a standard 4-CIM drivetrain, which was not powerful enough to effectively push around other robots.
When Lil' Mr. P finished climbing, the robot drove forward onto the raised platform. If the legs were not retracted before driving forward, they could catch on the edge of the platform. Sometimes, when the robot was driving fast enough, the force caused by this bent the piston legs, permanently damaging them. In the future, pistons should not be placed into situations where they can easily bend.
Claw subsystem
To grasp disks, Lil' Mr. P had a large claw. With the help of a piston, the entire claw mechanism slid back and forth inside rectangular aluminum tube, allowing the claw to move in/out of the robot frame. The claw itself consisted of three fingers, each connected by a linkage to a piston in the center. When the center piston actuated, the claws were forced to rotate outward - much like a camera tripod - and could grasp the disks from their center. The fingers were made of aluminum bar and covered in pool noodle and duct tape.
Climbing subsystem
Lil' Mr. P could climb by standing up on three actuating piston legs. The pistons were 1-1/2" bore, 8" stroke, and were affixed directly to the robot frame. The end of each piston had a CNC-milled wheel mount, along with a small wheel, allowing the robot to roll forward while standing up. A motor was originally affixed to the back leg, allowing the robot to drive while standing, but it was found to be unnecessary, and was not used during competition. To climb onto the platform, Lil' Mr. P first actuated its front legs, and then drove forward using the back wheels of the drivetrain. Once the front of the robot was positioned over the platform, the front legs were retracted and the back leg was extended, causing front of the drivetrain to touch the platform. Finally, the robot drove onto the platform using its drivetrain, retracting the back leg once it was finished.
