Engineering system co-design with limited plant redesign

Abstract

Rather than designing engineering systems from the ground up, engineers often redesign strategic portions of existing systems to accommodate emerging needs. In the redesign of mechatronic systems, engineers typically seek to meet the requirements of a new application via control redesign only, but this is often insufficient and physical system (plant) design changes must be explored. Here, an integrated approach is presented for the redesign of mechatronic systems involving partial plant redesign that avoids costly complete redesign. Candidate plant modifications are identified using sensitivity analysis, and then an optimization problem is solved that minimizes redesign cost while satisfying system requirements. This formal methodology for Plant-Limited Co-Design (PLCD) is demonstrated using a robotic manipulator design problem. The PLCD result costs significantly less than the full redesign, and parametric studies illustrate the tradeoff between redesign cost and performance. It is shown that the proposed sensitivity analysis results in the lowest cost limited redesign.

Keywords:

• design optimization
• robotics
• passive dynamics
• control
• energy efficiency

Notes

^†Optimization problems throughout this article were solved using a hybrid approach where a gradient-based method (SNOPT [Gill et al. 1997]) is applied after a gradient-free method (pattern search with a global search method [Audet and Dennis 2006]). The first step provides a good starting point for SNOPT and improves the probability of finding a global optimum.