NMPC-Augmented Visual Navigation and Safe Learning Control for Large-Scale Mobile Robots

TL;DR

This paper introduces an integrated control and navigation framework for large-scale mobile robots operating on loose terrain, combining visual pose estimation, nonlinear model predictive control, deep neural network policies, and safety monitoring.

Contribution

It presents a novel multi-module architecture that ensures stability, safety, and accurate control of large-scale robots on slip-prone terrain, with stability guarantees and real-world validation.

Findings

Achieved robust operation on slip-prone terrain with a 6,000 kg robot.

Demonstrated stability and safety guarantees through experimental validation.

Integrated multiple control modules for improved navigation and safety.

Abstract

A large-scale mobile robot (LSMR) is a high-order multibody system that often operates on loose, unconsolidated terrain, which reduces traction. This paper presents a comprehensive navigation and control framework for an LSMR that ensures stability and safety-defined performance, delivering robust operation on slip-prone terrain by jointly leveraging high-performance techniques. The proposed architecture comprises four main modules: (1) a visual pose-estimation module that fuses onboard sensors and stereo cameras to provide an accurate, low-latency robot pose, (2) a high-level nonlinear model predictive control that updates the wheel motion commands to correct robot drift from the robot reference pose on slip-prone terrain, (3) a low-level deep neural network control policy that approximates the complex behavior of the wheel-driven actuation mechanism in LSMRs, augmented with robust adaptive control to handle out-of-distribution disturbances, ensuring that the wheels accurately track the updated commands issued by high-level control module, and (4) a logarithmic safety module to monitor the entire robot stack and guarantees safe operation. The proposed low-level control framework guarantees uniform exponential stability of the actuation subsystem, while the safety module ensures the whole system-level safety during operation. Comparative experiments on a 6,000 kg LSMR actuated by two complex electro-hydrostatic drives, while synchronizing modules operating at different frequencies.