Topological design of electromechanical actuators with robustness toward over- and under-etching

In this paper, we combine the recent findings in robust topology optimization formulations and Helmholtz partial differential equation based density filtering to improve the topological design of electromechanical actuators. For the electromechanical analysis, we adopt a monolithic formulation to model the coupled electrostatic and mechanical equations. For filtering, we extend the Helmholtz-based projection filter with Dirichlet boundary conditions to ensure appropriate design boundary conditions. For the optimization, we use the method of moving asymptotes, where the sensitivity is obtained from the adjoint approach.
Our study shows that the robust filter approach produces topology optimized actuators with minimal length control and crisp structural boundaries. In particular, the minimal length control of both structural features and gap widths avoids common modeling artifacts in topology optimization, i.e. one-element wide structural parts or gaps. It thus leads to physically realizable designs that are robust against manufacturing imprecision such as over- and under-etching.
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