# External Constraint Handling for Solving Optimal Control Problems with Simultaneous Approaches and Interior Point Methods

## TL;DR

This paper introduces a novel method for efficiently handling inactive constraints in optimal control problems, significantly reducing computational effort when using interior point methods within a simultaneous approach framework.

## Contribution

The paper proposes a systematic constraint removal strategy tailored for interior point solvers in optimal control, improving computational efficiency during mesh refinement.

## Key findings

- Over 40% reduction in computation time in example problems
- Effective removal of inactive constraints without compromising solution feasibility
- Enhanced efficiency in interior point-based optimal control solvers

## Abstract

Inactive constraints do not contribute to the solution of an optimal control problem, but increase the problem size and burden the numerical computations. We present a novel strategy for handling inactive constraints efficiently by systematically removing the inactive and redundant constraints. The method is designed to be used together with simultaneous approaches under a mesh refinement framework, with mild assumptions that the original problem has feasible solutions, and the initial solve of the problem is successful. The method is tailored for interior point-based solvers, which are known to be very sensitive to the choice of initial points in terms of feasibility. In the example problem shown, the proposed scheme achieves more than a 40% reduction in computation time.