Kit of Parts Challenge Demo Bot: T-Shirt Cannon

[KRivera]

Description

The T-Shirt cannon is a semi-automatic, compressed air powered, mobile platform that fires t-shirts to distances of up to 65 yards. It is designed for use at sporting events, or any place where t-shirts need to be distributed in crowds.

Warnings

The projectile mechanisms use compressed air stored at 120psi. Sudden releases of pressure can cause serious injury.

• Always discharge the system when not in use and maintain strict control over firing mechanisms.
• Always be sure of where the barrels are pointing.
• Maintain a clear zone in front of the robot and practice verbal warnings before firing the cannon.

Components

Driving base

The robot uses the standard driving base from the 2011 FIRST Kit of Parts.

Mechanism

The barrels are made from standard, clear PVC pipe. The firing mechanism consists of two 12V air compressors, steel plumbing pipe (available from any home improvement or hardware store), an air storage tank, a main safety valve (to cut off the air supply to the firing solenoids), and three 12V solenoid valves. All pressure-containing components and systems are rated at or above 120 psi.

The air compressors are powered through Spike relays and are taken from the pre-2011 FIRST Kit of Parts. A regulator (also supplied with the Kit of Parts) is monitored by the control system. When a system pressure of 120 psi is reached, the control system switches the compressors off.

The solenoid valves are 3/4” NPT valves, and were purchased online. The actuation time is <10ms, allowing for very precise fire control by the NI CompactRIO control system. The valves are also powered through Spike relays.

The entire assembly is housed in a simple plywood enclosure.  The structural frame is completed by 1x2 lumber and secured to the driving baseby 80/20™aluminum rails.

Operating instructions

Safety

• It is recommended that the system be “dry-fired” to relieve any pressure before disabling teleop mode.
• Place a purge valve on the rear of one of the compressors. The purge valve can be used to release any residual system pressure after the robot is powered off and teleop mode is disabled.

Power-up

1. Connect the driver station to the router on therobot.
2. Once the driver station is connected, enable teleoperated mode.
   - The compressors should begin to pressurize the system when teleop mode is enabled.
3. Wait for the system to pressurize. This can take several minutes, depending on the battery charge.
   - Pulling the trigger at any time will fire the cannon, releasing anystored pressure in the system (regardless of the system pressure).
4. Once the system is fully charged, the compressors will automatically shut off.
   -The system is ready to fire. Ensure all personnel are clear of the front of the robot before firing.

Operation

• Pull the trigger to fire the main cannon. Pulling the trigger repeatedly will cause the solenoids to fire sequentially, allowing t-shirts to be fired semi-automatically from the barrels.
• To change the elevation of the main cannon, use buttons 2 and 3 on the joystick.
• The robot can be driven with the joystick. Push the joystick to move forward, pull back to move backward. Lean the joystick left or right to rotate the robot in either direction. The control system uses the default “Arcade Drive” VIs that ship with the FRC edition of LabVIEW™.

Power-down

1. Ensure that none of the barrels of the main cannon are loaded.
2. Dry-fire the main cannon several times to release system pressure.
3. Press the red button on the main power relay and/or disable teleop mode from the driver station.
4. Slowly open the purge valve on the back of the compressor to release any residual pressure.