Online Feedback Control for Input-Saturated Robotic Systems on Lie Groups

TL;DR

This paper introduces an online feedback control method for robotic systems on Lie groups with input saturation, extending Sequential Action Control (SAC) to improve real-time control and scalability.

Contribution

The paper extends SAC to Lie groups, providing a closed-form feedback law for input-saturated systems and demonstrating its effectiveness on robotic models.

Findings

SAC on Lie groups achieves real-time control with input saturation.

The method scales well to complex robotic systems.

SAC outperforms iLQG in speed and basin of attraction.

Abstract

In this paper, we propose an approach to designing online feedback controllers for input-saturated robotic systems evolving on Lie groups by extending the recently developed Sequential Action Control (SAC). In contrast to existing feedback controllers, our approach poses the nonconvex constrained nonlinear optimization problem as the tracking of a desired negative mode insertion gradient on the configuration space of a Lie group. This results in a closed-form feedback control law even with input saturation and thus is well suited for online application. In extending SAC to Lie groups, the associated mode insertion gradient is derived and the switching time optimization on Lie groups is studied. We demonstrate the efficacy and scalability of our approach in the 2D kinematic car on SE(2) and the 3D quadrotor on SE(3). We also implement iLQG on a quadrator model and compare to SAC, demonstrating that SAC is both faster to compute and has a larger basin of attraction.