Nigel -- Mechatronic Design and Robust Sim2Real Control of an Over-Actuated Autonomous Vehicle (2401.11542v4)

Abstract: Simulation to reality (sim2real) transfer from a dynamics and controls perspective usually involves re-tuning or adapting the designed algorithms to suit real-world operating conditions, which often violates the performance guarantees established originally. This work presents a generalizable framework for achieving reliable sim2real transfer of autonomy-oriented control systems using multi-model multi-objective robust optimal control synthesis, which lends well to uncertainty handling and disturbance rejection with theoretical guarantees. Particularly, this work is centered around a novel actuation-redundant scaled autonomous vehicle called Nigel, with independent all-wheel drive and independent all-wheel steering architecture, whose enhanced configuration space bodes well for robust control applications. To this end, we present the mechatronic design, dynamics modeling, parameter identification, and robust stabilizing as well as tracking control of Nigel using the proposed framework, with exhaustive experimentation and benchmarking in simulation as well as real-world settings.

• The paper proposes a novel over-actuated vehicle design featuring an independent 4WD4WS system to enhance fault tolerance and maneuverability.
• It introduces both nonlinear and linearized dynamic models integrated with a mixed H2-H∞ robust control synthesis to effectively manage uncertainty.
• Experimental results benchmark the approach against conventional controls, demonstrating significant improvements in mitigating sim2real discrepancies.

Essay on "Nigel - Mechatronic Design and Robust Sim2Real Control of an Over-Actuated Autonomous Vehicle"

The paper "Nigel - Mechatronic Design and Robust Sim2Real Control of an Over-Actuated Autonomous Vehicle" presents a compelling examination of sim2real transfer challenges in autonomous vehicle control, introducing an innovative framework for reliable transfer under conditions of uncertainty and disturbances. The authors propose a novel actuation-redundant scaled autonomous vehicle, Nigel, equipped with independent all-wheel drive and steering capabilities. This configuration significantly expands the control application's configuration space, thus contributing to robust sim2real performance.

Mechatronic Design and Configuration

Nigel showcases a robust mechatronic architecture featuring a four-wheel drive and steering system (4WD4WS). This actuation configuration offers distinct benefits in terms of redundancy and independent wheel control, enhancing fault tolerance and maneuverability. Notable is the design's small form factor at a 1:14 scale, allowing comprehensive sensor integration. The embodiment of these factors in Nigel underscores the paper's focus on hardware-software co-design—a necessary shift in the current era of autonomous systems development.

Dynamics Modeling and Control Synthesis

The paper advances the discussion on vehicle dynamics by presenting both nonlinear and linearized models specific to the 4WD4WS architecture. The nonlinear model is deduced from foundational works, which the authors adeptly linearize for control synthesis. This systematic derivation transitions into a polytopic linear parameter-varying model, accommodating parameters like frictional coefficients as sources of uncertainty. The methodological rigor in parameter identification from empirical data bolsters the reliability of this modeling approach.

Drawing on multi-model multi-objective control theory, the authors employ mixed $H_2$-$H_\infty$ strategies within a robust control framework. This approach optimally balances disturbance rejection with performance tradeoffs, thereby placing emphasis on $D$-stability guarantees. Such a framework not only aids sim2real transfer but also shields against real-world dynamical disruptions, which are paramount for practical vehicle autonomy deployment.

Experimental Validation and Benchmarking

The experimental analysis offers crucial insights into the efficacy of the proposed control framework. Benchmarking against both a traditional control scheme and an open-loop system highlights superior performance, especially in terms of error metrics across standard maneuvers. The independent 4WD4WS configuration inherently supports more nuanced control strategies, evidenced by enhanced $H_\infty$ and $H_2$ performance outcomes as compared to conventional architectures. Through these results, the authors propose an advanced control strategy capable of navigating significant sim2real discrepancies.

Implications and Future Work

The implications of this research extend to both theoretical advances in robust control synthesis and practical developments in vehicle autonomy. The proposed framework not only mitigates the sim2real gap via robust control but also potentiates further research into vehicular digital twins, autonomy stacks, and fault-tolerant systems. The anticipated future work involves the exploration of mixed sensitivity loop-shaping and full-scale vehicular deployments, which could lead towards more resilient and adaptable autonomous systems.

In summary, this paper significantly contributes to the discourse of autonomous vehicle control. Through rigorous design and control synthesis methodologies, the authors offer substantial improvements in sim2real transfer reliability, pushing the boundaries of vehicle control theory and practice. Nigel, as a prototype, not only substantiates theoretical claims but also serves as a versatile foundation for future innovations in autonomous mobility systems.