Evolutionary Topology Optimization for Designing Cellular Fluid Actuators

Bio-inspired shape adapting systems, based on plants that can reshape themselves by altering the pressure in their cells, can attain very desirable features, such as light weight, large actuation and simple input. It is proposed to design efficient fluid actuators as cellular compliant mechanisms, in which each cell is internally loaded by pressured fluid cavities, through topology optimization techniques. In this work, a model for such cells was proposed, the finite element analysis, sensitivity analysis and optimization method were described and implemented. The chosen optimization method was the soft-kill Bidirectional Evolutionary Structural Optimization (BESO) method with material penalization. The loads dependency on the topology together with two considered nonlinear effects (geometrical nonlinearity and load nonlinearity) act as hindering factors to the optimization process as a whole. Cells with maximized expansion were obtained for two cases: cells that actuate only horizontally; and cells that actuate both horizontally and vertically.