Time-Optimal Path Tracking via Reachability Analysis

TL;DR

This paper introduces a reachability analysis-based path controller that guarantees feasible reference trajectories for time-optimal path tracking, improving performance under torque constraints.

Contribution

It proposes a novel reachability analysis approach for path parameterization, ensuring feasible trajectories and enhanced tracking performance.

Findings

Outperforms existing path controllers in simulations.

Guarantees feasible reference trajectories under torque bounds.

Improves tracking accuracy and robustness.

Abstract

Given a geometric path, the Time-Optimal Path Tracking problem consists in finding the control strategy to traverse the path time-optimally while regulating tracking errors. A simple yet effective approach to this problem is to decompose the controller into two components: (i)~a path controller, which modulates the parameterization of the desired path in an online manner, yielding a reference trajectory; and (ii)~a tracking controller, which takes the reference trajectory and outputs joint torques for tracking. However, there is one major difficulty: the path controller might not find any feasible reference trajectory that can be tracked by the tracking controller because of torque bounds. In turn, this results in degraded tracking performances. Here, we propose a new path controller that is guaranteed to find feasible reference trajectories by accounting for possible future perturbations. The main technical tool underlying the proposed controller is Reachability Analysis, a new method for analyzing path parameterization problems. Simulations show that the proposed controller outperforms existing methods.