We’re soliciting comments and input on our draft design for Power Up. (Here is the launch page for game resources, and here is the PDF of the complete game manual.) If you are new to FRC and Power Up, sections 1-4 are the only ones relevant to understanding our approach at a high level. Beyond that, just know that we can generally implement any mechanism we want as long as it is powered by a very narrow list of motors. Hydraulics are not permitted, and we have opted not to use pneumatics this year due to complexity. So we want all our actuation to be mechanical, with belts, chains, pulleys, etc. driven by electric motors. Comments below assume you are familiar with the basic game and field elements as described in the game manual.
Here is our CAD export (2018 Rex Power Up v15.step) from AutoDesk Fusion 360, STEP format.
Our game strategy is to focus on loading the Vault and controlling the switches. We are not planning to attempt to lift cubes 6 feet + to the scale, and we currently don’t plan to attempt to climb during the endgame, hoping we can efficiently load the Vault and earn a Levitate power up to contribute to our alliance.
The key mechanism in our design is a 2-fingered gripper driven by a worm screw and mounted to a carriage on an elevator. We will get the ability to positively control cubes in the x and z dimensions with the elevator/carriage, and we will rely on the robot drivetrain for the y axis mobility.
The elevator and carriage in our model ride on linear motion parts from Igus. The carriage is a low-profile linear guide system. The elevator is shown as drylin W single rail, but that is out of stock so we need something equivalent. We feel both of these linear systems should be engineered to handle shock impacts, as this is a full-contact game with 5 other robots on the field and active defense strategies.
All mechanisms must be inside the robot frame perimeter at the start of the game. To achieve this, our gripper carriage is on an unpowered pivot. It will rotate up and rest on the top horizontal crosspiece of the elevator. We can place a Power Cube on a shelf within the frame of the robot at match start. During autonomous, the gripper will grip the cube, then the elevator will descend. The shelf will pivot the cube and the gripper carriage about 270 degrees so that the gripper carriage comes to rest against the lower elevator crosspiece. We hope. Our CAD skills are poor, so we haven’t modeled well enough to simulate the motion.
Another problem with our model is that we found a nice gripper design on the internet, but don’t have the skills to scale the arms up to the correct size for grabbing the cube. So currently our robot has the T-Rex arms problem. The other problem with the gripper is that we don’t know how we would fabricate it, but our first concern is whether the overall design would work.