Stiffness Control with Pneumatic Artificial Muscle Inclusions in a Cellular Honeycomb Unit

Abstract

Pneumatic artificial muscles are potentially useful actuators for the development of tunable modulus structures. This paper details the simulation and experimental validation of a unit Delrin hexagonal cell with three pneumatic artificial muscle inclusions for the purpose of actively controlling the modulus of the cell in the horizontal or vertical directions. The complete set of analytical equations used to simulate the cell is presented, including the PAM force equations, the cell wall modulus expressions, the force balance for the fully-assembled cell in the horizontal and vertical directions, and the secant modulus method. Then, simulation is compared to experimental measurements of the cell modulus in the horizontal and vertical directions over a range of pressures up to 1302 kPa. It is shown that simulation captures the trends evident in the experimental results and that the maximum increase in cell modulus is achieved when only the set of muscles perpendicular to the direction of loading is fully pressurized. A maximum increase in cell modulus of 227% is demonstrated in the horizontal direction with a corresponding change in equilibrium cell angle of only 3.75%.