A Corrector-aided Look-ahead Distance-based Guidance for Online Reference Path Following with an Efficient Mid-course Guidance Strategy

TL;DR

This work tackles autonomous 2-D path following for unmanned vehicles by addressing limitations of fixed look-ahead guidance. It introduces a two-phase strategy: a mid-course phase that optimally steers the UxV toward an initiation circle tangent to the path start using a dynamically selected $L_1$, and a terminal, close-range phase that augments a constant $L_1$ with a corrector point to tighten tracking, while online optimization of $k_1$ and $k_2$ minimizes local RMS cross-track error. The method combines analytic geometric decisions (initiation circle contact, optimal look-ahead) with a weighted sum of look-ahead and corrector-based commands, yielding bounded lateral acceleration and reduced cross-track error compared to conventional constant-$L_1$ guidance. Simulation results on a sinusoidal reference path demonstrate improved tracking performance across diverse initial conditions, validating the proposed algorithm and its online tuning scheme. The approach provides a practical, model-light path-following framework with potential extension to 3-D trajectories.

Abstract

Efficient path-following is crucial in most of the applications of autonomous vehicles (UxV). Among various guidance strategies presented in literature, the look-ahead distance ($L_1$)-based nonlinear guidance has received significant attention due to its ease in implementation and ability to maintain a low cross-track error while following simpler reference paths and generating bounded lateral acceleration commands. However, the constant value of $L_1$ becomes problematic when the UxV is far away from the reference path and also produces higher cross-track error while following complex reference paths having high variation in radius of curvature. To address these challenges, the notion of look-ahead distance is leveraged in a novel way to develop a two-phase guidance strategy. Initially, when the UxV is far from the reference path, an optimized $L_1$ selection strategy is developed to guide the UxV towards the vicinity of the start point of the reference path, while maintaining minimal lateral acceleration command. Once the vehicle reaches a close neighborhood of the reference path, a novel notion of corrector point is incorporated in the constant $L_1$-based guidance scheme to generate the guidance command that effectively reduces the root mean square of the cross-track error and lateral acceleration requirement thereafter. Simulation results validate satisfactory performance of this proposed corrector point and look-ahead point pair-based guidance strategy, along with the developed mid-course guidance scheme. Also, its superiority over the conventional constant $L_1$ guidance scheme is established by simulation studies over different initial condition scenarios.

Figures (12)

• Figure 1: Initial engagement geometry
• Figure 2: Engagement Geometry for constant Look-Ahead Guidance ($\eta<0$ illustrated)
• Figure 3: Moving to Initiation Circle
• Figure 4: Initial Heading to Contact Point Mapping
• Figure 5: Circle Selection in Midcourse Phase

Theorems & Definitions (1)

• proof