Constrained Policy Optimization via Sampling-Based Weight-Space Projection

Fuente: arXiv
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Autores principales: Cao, Shengfan, Borrelli, Francesco, Joa, Eunhyek
Formato: Preprint
Publicado: 2025
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author Cao, Shengfan
Borrelli, Francesco
Joa, Eunhyek
author_facet Cao, Shengfan
Borrelli, Francesco
Joa, Eunhyek
contents Safety-critical learning requires policies that improve performance without leaving the safe operating regime. We study constrained policy learning where model parameters must satisfy rollout-based safety constraints that can be evaluated but not differentiated analytically. We propose SCPO, a sampling-based weight-space projection method that enforces safety directly in parameter space without requiring gradient access to the constraint functions. SCPO constructs a local safe region by combining rollout-based safety evaluations with smoothness bounds relating parameter perturbations to changes in safety metrics, and projects each gradient update via a convex QCQP. We establish a safe-by-induction guarantee: starting from any safe initialization, all intermediate policies remain safe given feasible projections. In constrained control settings with a stabilizing backup policy, SCPO further ensures closed-loop stability while enabling safe adaptation beyond the conservative backup. Experiments on constrained regression with harmful supervision and double-integrator imitation with a malicious expert show that SCPO rejects unsafe updates, maintains feasibility throughout training, and achieves meaningful objective improvement.
format Preprint
id arxiv_https___arxiv_org_abs_2512_13788
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Constrained Policy Optimization via Sampling-Based Weight-Space Projection
Cao, Shengfan
Borrelli, Francesco
Joa, Eunhyek
Machine Learning
Robotics
Safety-critical learning requires policies that improve performance without leaving the safe operating regime. We study constrained policy learning where model parameters must satisfy rollout-based safety constraints that can be evaluated but not differentiated analytically. We propose SCPO, a sampling-based weight-space projection method that enforces safety directly in parameter space without requiring gradient access to the constraint functions. SCPO constructs a local safe region by combining rollout-based safety evaluations with smoothness bounds relating parameter perturbations to changes in safety metrics, and projects each gradient update via a convex QCQP. We establish a safe-by-induction guarantee: starting from any safe initialization, all intermediate policies remain safe given feasible projections. In constrained control settings with a stabilizing backup policy, SCPO further ensures closed-loop stability while enabling safe adaptation beyond the conservative backup. Experiments on constrained regression with harmful supervision and double-integrator imitation with a malicious expert show that SCPO rejects unsafe updates, maintains feasibility throughout training, and achieves meaningful objective improvement.
title Constrained Policy Optimization via Sampling-Based Weight-Space Projection
topic Machine Learning
Robotics
url https://arxiv.org/abs/2512.13788