Air Tanks and Pressure:

Estimated Volume:

Figure 1: Arm Mold with Air Chamber Outlined

Each chamber is modeled as a sphere with the same cross sectional area as the air chamber. The diameter and volume of this sphere are used to calculate the number of layer needed as well as the amount of air needed to fill the arm to full extension. The total desired length of the arm is 18 inches so it will be capable of reaching objects on the ground around the robot.

Figure 2: Simplified inflatable finger schematic (fully inflated)

The maximum operating pressure of either of these systems will be 15psi. The worse case scenario of needing to fully inflate at this pressure will be used in tank volume and pressure requirements. Currently a 590ml tank capable of containing 120psi has been purchased. The air will be considered an ideal gas for all calculation purposes.

In order to fully inflate the arm, the tank will need to be pressurized to roughly 40 psi. In order to increase the flow rate as well as decrease the inflation time, a higher tank pressure can be used.

The desire inflation time is 2 seconds. Therefore in order to inflate to arm fully a flow rate of 45in^3/sec or 1.56 cfm. A flow rate calculator from http://www.pipeflowcalculations.com/airflow/ was used in order to calculate the needed input pressure from the desired output pressure of 15 psi, the minimum flow rate needed (1.56cfm), the pipe diameter (0.16in), and the pipe length (1m). From this calculator, the psi needed at the inlet to generate this cfm is only 17.43psi. Therefore as long as the tank is still above this pressure when the arm is fully inflated, it will have inflated fully within the 2 seconds specified in the engineering requirements.