Game: Recycle Rush
Our robot: Lil' Suzie
Recycle Rush is the 2015 FIRST Robotics Competition game. Alliances of three teams compete by creating stacks of gray totes on a 54′ x 27′ field. The totes can either be collected from the Landfill Zone, near the center of the field, or from a Human Player Station through a chute at the end of the field. The field is divided into two sides by a Step, separating the two alliances. Points can be scored by placing these stacks on the scoring platforms. Additionally, placing green recycling bins on top of stacks, and pool noodles inside of the bins, earns extra points. Opposing teams can also work together to earn points for their respective alliances by creating a joint stack of yellow totes on the dividing Step.
Meet Lil' Suzie
Lil’ Suzie was designed to perform as an external-stacking robot, collecting totes and bins outside of the frame perimeter. The robot was built for dexterity and versatility using the Kit of Parts base. Lil’ Suzie uses an elevator mechanism and carriage, attached to the base, to lift up to 3 totes and 1 bin.
Our 2015 drive base is the FRC Kit of Parts AM14U2 chassis. Our configuration is in the square stance, measuring at 27.5″ x 28.5″.
Our 2015 drivetrain is a single transmission AndyMark-0654 Toughbox mini. The overall ratio is 12.75:1. In first determining our transmission, the most important factor to 4990 was that Recycle Rush’s field is half the size of prior years. Therefore, acceleration and quick increases in torque are unnecessary, as Recycle Rush is a game of higher finesse. Using two CIMS per gearbox freed up motor space for our elevator gearbox.
Vanguard’s controls system used Wi-Fi broadcasting communications along with a NI roboRIO. All motors on the robot were controlled by Talon speed controllers. Our pneumatic arms were controlled by a Vex Pro Spike relay and Festo solenoid.
The elevator mechanism is composed of 1/8” thick 2”x1” aluminum bars forming a 20.25”x68.5” frame outfitted with a continuous chain loop to drive the central carriage. The drive side has a 15 tooth hex-bore sprocket which is looped around by ~10 feet of #35 ANSI Standard Roller chain. On the top end of the loop, an identical sprocket is fitted on 3 inches of 1/2″ hex shaft, flanged bearings, and clamping shaft collars for retainment. The gearbox is a Vex VersaPlanetary dual-stage planetary with two 5:1 gear kits for a total ratio of 25:1. We decided to power this gearbox with a standard 2.5″ CIM controlled by a Talon motor controller.
The carriage is attached to the elevator’s continuous chain loop with five 8-32 socket head alloy steel bolts. To ensure maximum carriage support by the chain, we used 18-8 stainless steel spacers in conjunction with Vex VersaFrame Roller Chain Mounts. By using the Vex gussets, we were able to maximize the surface area contact between the chain and the carriage. The same front carriage bars have mounting 8 mounting holes precision machined in order to match the mounting holes on the fork. The two attach, and the elevator is thus able to lift the fork.
Our prime consideration when designing the carriage was to ensure smooth travel along the elevator frame. The ultimate solution was to use the VersaFrame Linear Motion Gusset kits combined with 1/4″-20 screws, radial bearings, nylon spacers, and round 1/2″ anodized aluminum stock. The dual radial bearing action provides the carriage with proper rotational constraints (inhibiting pitch, yaw, roll), while retaining the ability to smoothly slide up and down the frame. The carriage setup is strong enough to support a cantilevered mass of totes outside of the frame.
The fork is a modular attachment to the carriage in order to fit within the transportation perimeter. The fork’s left arm is powered by two 10″ throw, 3/4″ bore “Cylinders Only” pneumatic cylinders. This pneumatic setup provides the drive team with the option of gathering totes from both a vertical and horizontal orientation. When fired, the pneumatic cylinders retract the dynamic left arm and uses a radial bearing roller system (similar to the carriage’s) to ride along the two 2×1″ boxbeam tracks. The resulting motion allows the fork to clamp down on a tote within its grab.
Lil’ Suzie was operated using the same joystick-based system as the previous season. One joystick was used to raise and lower the elevator carriage and operate the pneumatic cylinders (opening and closing the fork), and the other was used to operate the drivetrain.