TR2011-053

Integrated Design and Control of Flexure-Based Nanopositioning Systems - Part I: Methodology



Flexure-based mechanisms, also referred to as flexures, are widely being used as motion-guidance, or bearing, elements in applications requiring multi-degree-of-freedom positioning and alignment. Unlike friction-bearings (such as sliding or rolling contact bearings), flexures can be designed to offer, to a large extent, reliable linear elastic motion with a high resolution (on the order of nanometers) over small ranges of motion (on order of micrometers). Example applications include positioning a probe or sample in atomic force microscopy, alignment of tool and sample in stamping processes, and fine-positioning of wafer steppers in semiconductor manufacturing. These applications are often required satisfy critical functional requirements, such as load-capacity, bandwidth, resolution, and range. A systematic approach is needed to simultaneously address the design and control challenges involved, starting from the initial design concept generation stage to the final control implementation and testing. In this paper, we present an integrated design and control method for implementing flexurebased nanopositioning systems. We discuss the need for varying design topology and order of a controller in design and control optimization. An automation engine generates a set of flexurebased design topologies and also controllers of varying order in the optimization. A simple 1-DOF example is worked out to illustrate the steps involved in using this methodology. The outcome of the exercise is a novel design topology, with it shape and size optimized, and a controller synthesized such that a desired control bandwidth and design requirements of strength and modal separation are met.