Topological design of electromechanical actuators with robustness toward over- and under-etching
Abstract 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.
Topology optimization of a coupled thermal-fluid system under a tangential thermal gradient constraint
This paper presents a continuous adjoint approach for topology optimization of a coupled heat transfer and laminar fluid flow system under tangential thermal gradient (TTG) constraints. In this system, the thermal gradient along the boundary of multiple heat sources needs to be controlled. The design goals are to minimize the temperature of the domain, the fluid power dissipation and the TTG along the boundary of the heat sources. The first two goals are combined into a single cost function with weight variables. The TTG is constrained in one of two forms, an integral form where the integral of TTG squares along the boundaries of heat sources is constrained, or a point-wise form where TTG is constrained point-wise. A gradient-based approach is developed to obtain the optimized designs. A salient feature of our approach is the use of the continuous adjoint approach to derive gradients of both the cost function and two forms of TTG constraints. Numerical examples demonstrate that the continuous adjoint approach leads to successful topological optimization of the constrained thermal-fluid system. The use of TTG constraint is effective in lowering the TTG along the heat source boundaries. The resulting designs exhibit clear black/white contrast.
Study of large bending and low voltage drive electrostatic actuator with novel shaped cantilever and electrode
This paper presents the bending performance of an electrostatic actuator which has an electrode and a cantilever both with polynomial curved shapes. To investigate how to get a large deflection of a cantilever, various device structures are examined by a numerical calculation which takes into consideration large deflection formulation of a cantilever. Maximum deflections, just before a cantilever is pulled into an electrode, are evaluated. In a combination of a curved electrode and a rectangular cantilever, the applied voltage at the maximum deflection decreases at lower polynomial order of the electrode shape, while the deflection decreases. A shorter electrode gives larger deflection, while the applied voltage significantly increased. On the other hand, the modulated shaped cantilever is effective to enlarge the deflection and reduce the applied voltage, simultaneously.