Using Topology Optimization for Actuator Placement within Motion Systems

Abstract

Topology optimization is a strong approach for generating optimal designs which cannot be obtained using conventional optimization methods. Improving structural characteristics by changing the internal topology of a design domain has been fascinating scientists and engineers for years. Topology optimization can be described as a distribution of a given amount of material in a specified design domain, which is subjected to certain loading and boundary conditions. This domain can then be optimized to minimize specified objectives, for example compliance. For static problems, topology optimization is extensively used. The distribution of material, void and solid regions, can be used to solve several problems within the mechanical domain. However, this method of optimization is also used to optimize structures with respect to their resonant dynamics.

Design of actuator placement is used to determine the most optimal actuator layout for a given objective, for example reducing responses. Combined with topology optimization, both design variables can influence each other, and be optimized towards the wanted behavior. This is done in a static domain. When material is removed, the force layout is updated, which influences the material distribution again. It is shown that the combination of these design variables in the optimization process, contributes to a better result; weight reduction can be achieved, while large deformations are preserved.

Design of actuator placement, combined with topology optimization is also implemented in a dynamic domain. Since topology changes result in frequency response changes, the force placement is more sensitive. On the other hand, forces can be placed in a smart way, to ensure some mode shapes are not excited, whereas others are. By enabling positive and negative forces these forces can even be used to counteract or minimize certain modal responses. When implementing for example a harmonic excitation, the weight and total force can be linked together, to ensure accelerations are feasible. A weight reduction can thus lead to force reduction, which on its turn leads to less deformations. Especially in the high-precision industry, smart placement of actuators, including weight reduction can be very helpful. The combination of these phenomena could provide a new insight in creating accurate wafer stages.