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arXiv · 2203.11516

NOSNOC: A Software Package for Numerical Optimal Control of Nonsmooth Systems

Armin Nurkanović·Moritz Diehl
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Abstract

This letter introduces the NOnSmooth Numerical Optimal Control (NOSNOC) open-source software package. It is a modular MATLAB tool based on CasADi and IPOPT for numerically solving Optimal Control Problems (OCP) with piecewise smooth systems (PSS). The tool supports: 1) automatic reformulation of systems with state jumps into PSS (via the time-freezing reformulation [Nurkanovi\'c et al., 2021]) and of PSS into computationally more convenient forms, 2) automatic discretization of the OCP via, e.g., the recently introduced Finite Elements with Switch Detection [Nurkanovi\'c et al., 2022] which enables high accuracy optimal control and simulation of PSS, 3) solution methods for the resulting discrete-time OCP. The nonsmooth discrete-time OCP are solved with techniques of continuous optimization in a homotopy procedure, without the use of integer variables. This enables the treatment of a broad class of nonsmooth systems in a unified way. Two tutorial examples are given. A benchmark shows that NOSNOC provides both faster and more accurate solutions than conventional approaches, including mixed-integer formulations.

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Armin Nurkanović, Moritz Diehl. 2022-03-22. NOSNOC: A Software Package for Numerical Optimal Control of Nonsmooth Systems. https://doi.org/10.1109/lcsys.2022.3181800

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