Muscle Testing Plan
Overview: In order to quantify the kinetic ability of the muscles that are included in our design, a test will be conducted on each muscle type to determine and compare the force output. This test will help us to examine the aptitude of our designs and the movement speed of the robot. The test will consist of the constrained muscles being actuated and measured for force output.
Figure 1a/b - a. Soft robotic muscle, actuated b. McKibben muscle displayed in relaxed and actuated states
Theory: The soft robotic muscles and the McKibben air muscles are fairly dissimilar in composition and actuation. The soft robotic muscle is comprised nearly entirely of a silicone compound, and features a number of rectangular chambers along its length. When the muscle is pressurized, the chambers expand outwards, curling the muscle, as shown in figure 1a. In contrast, the McKibben air muscle is comprised of tubing, mesh, and some hardware. The main components are the bladder, which is most likely polyurethane, and the mesh that covers it. When the bladder is pressurized, the mesh forces the muscle to contract, as shown in figure 1b. This difference in actuation and design will allow each muscle to fit different niches in our robot design. It will, however, be of concern, with respect to the unhindered motion and movement speed of our robot, to find and compare the force capabilities of the muscles.
Figure 2a/b - a. Experimental setup for soft robotic muscle b. Experimental setup for McKibben muscle
Implementation: To measure the force due to actuation in the muscles, the muscles will be fixed to a reference point on one end, and attached to a force gauge on the other end. Due to the difference in actuation for the two muscles, the soft robotic muscle will be constrained in a vertical position, normal to the force gauge, while the McKibben muscle will be constrained in a horizontal position, in plane with the force gauge.
Test Facility: Using 80/20 aluminum supports in the mechanical lab and other support materials, potentially wood, the fixture outlined in figure 2 will be assembled for testing. Also, the desired force gauge will be available in the lab.
Test Procedure:For both setups, the gauge will be zeroed for the starting position, then the muscle will be pressurized to 5, 10, 15, and 20 PSI. The force will be recorded for each pressure.