Pneumatics
From Combat Robot
Pneumatic systems employ pressurized gas to provide mechanical force. They are typically used in combat robots to provide a large, rapid force to power a lifter or flipper style weapon. They are also useful in self righting mechanisms.
The pneumatic system consists of a pressure cylinder to hold the pressurized gas, an electrically operated valve to direct the gas flow, pressure hoses to carry the gas to the actuator, and an actuator which converts the gas pressure into mechanical force. A pressure regulator may be required in some systems to reduce the gas pressure to a level usable by the rest of the system.
The gas used may be high-pressure air (HPA), or carbon dioxide (CO2) stored in a liquid form. The ability of CO2 to convert to a liquid at pressures around 800 PSI allows for large quantities of the gas to be stored in relatively little space. The drawbacks to CO2 are the limited maximum pressure, and the extreme cold produced during the conversion from a liquid to a gas. The cold may freeze some pneumatic components and caused a reduction in gas pressure. HPA systems can run at higher pressures and do not generate frigid temperatures in operation.
The typical actuator used in combat robotics is a linear pneumatic cylinder. Cylinders are available in a variety of bore diameters and stroke lengths, as well as maximum pressure ratings. The theoretical force available from a pneumatic cylinder may be calculated:
- Force = 3.1416 * bore radius2 * gas pressure available
Example: a pneumatic cylinder with a 1” radius bore operating at 125 PSI provides 3.1416 * (1)2 *125 = 3.1416 * 1 * 125 = 392.7 pounds of force.
Pneumatic systems on combat robots are potentially very dangerous to build and operate because of their speed and force. Exercise extreme caution when working with such components, and carefully follow all safety regulations required by event organizers.
A very complete article on combat robot pneumatics can be found at the Team DaVinci Pneumatics page
