Co Design of an Active Suspension Using Simultaneous Dynamic Optimization

Abstract

Design of physical systems and associated control systems are coupled tasks; design methods that manage this interaction explicitly can produce systemoptimal designs, whereas conventional sequential processes may not. Here, we explore a new technique for combined physical and control system design (codesign) based on a simultaneous dynamic optimization approach known as direct transcription, which transforms infinitedimensional control design problems into finitedimensional nonlinear programming problems. While direct transcription problem dimension is often large, sparse problem structures and finegrained parallelism (among other advantageous properties) can be exploited to yield computationally efficient implementations. Extension of direct transcription to codesign gives rise to new problem structures and new challenges. Here, we illustrate direct transcription for codesign using a new automotive active suspension design example developed specifically for testing codesign methods. This example builds on prior active suspension problems by incorporating a more realistic physical design component that includes independent design variables and a broad set of physical design constraints, while maintaining linearity of the associated differential equations. A simultaneous codesign approach was implemented using direct transcription, and numerical results were compared with conventional sequential optimization. The simultaneous optimization approach achieves better performance than sequential design across a range of design studies. The dynamics of the active system were analyzed with varied level of control authority to investigate how dynamic systems should be designed differently when active control is introduced.