Exact Truncation and Radial Rigidity in Time-Optimal Control
Abstract
We consider minimum-time control for the linear system ż(t)=Az(t)+Bu(t), |u|L∞(0,∞;ℝm)≤ 1, with A∈ℝn× n and B∈ℝn× m. While the individual point-target and ball-target problems are classical, we study a different question: when are their optimal controls exactly compatible, in the sense that, for every nonzero initial state x and all sufficiently small ε>0, the optimal control for the tolerance ball B̅ε(0) is precisely the restriction of the point-target optimal control? We prove that this {\it{exact truncation}} property is equivalent to the rigidity conditions B B⊤=βIn, A+A⊤=2aIn, β>0, a≤ 0, and also to Euclidean radiality of the point-target minimum-time function. Thus exact truncation holds precisely when the sublevel sets of the point-target minimum-time function are Euclidean balls centered at the origin, matching the geometry of the tolerance targets. Moreover, the local property automatically extends to every 0<ε<|x|, and the resulting optimal times and point-target optimal feedback are both explicit.
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BibTeX
@misc{quan2026exact,
title = {{Exact Truncation and Radial Rigidity in Time-Optimal Control}},
author = {Changqin Quan and Gengsheng Wang and Lijuan Wang and Qishu Yan},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22802},
eprint = {2609.22802},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22802},
}
RIS
TY - UNPB
TI - Exact Truncation and Radial Rigidity in Time-Optimal Control
AU - Changqin Quan
AU - Gengsheng Wang
AU - Lijuan Wang
AU - Qishu Yan
PY - 2026
DA - 2026/09/19
PB - arXiv
DO - 10.48550/arxiv.2609.22802
UR - https://arxiv.org/abs/2609.22802
AB - We consider minimum-time control for the linear system ż(t)=Az(t)+Bu(t), |u|_L^∞(0,∞;ℝ^m)≤ 1, with A∈ℝ^n× n and B∈ℝ^n× m. While the individual point-target and ball-target problems are classical, we study a different question: when are their optimal controls exactly compatible, in the sense that, for every nonzero initial state x and all sufficiently small ε>0, the optimal control for the tolerance ball B̅_ε(0) is precisely the restriction of the point-target optimal control? We prove that this {\it{exact truncation}} property is equivalent to the rigidity conditions B B^⊤=βI_n, A+A^⊤=2aI_n, β>0, a≤ 0, and also to Euclidean radiality of the point-target minimum-time function. Thus exact truncation holds precisely when the sublevel sets of the point-target minimum-time function are Euclidean balls centered at the origin, matching the geometry of the tolerance targets. Moreover, the local property automatically extends to every 0<ε<|x|, and the resulting optimal times and point-target optimal feedback are both explicit.
ER -