# Riverbank Following Planner (RBFP) for USVs Based on Point Cloud Data
## 5 Conclusions and Future Work  
This paper introduced an innovative riverbank following planner (RBFP) for USVs. This planner leverages a 2D LiDAR to scan riverbank shapes, enabling the USV to autonomously generate navigation paths without the need for manually predefined waypoints. Within the VRX simulation environment, where wind force was introduced as an external perturbation, our planner demonstrated remarkable proficiency. For straight banks, 96.92% of the path exhibited deviations confined within 15% of the relative distance. Even in more intricate convex and concave banks, 67.30% and 61.15% path following efficiency was achieved. The RBFP notably addresses a significant challenge in traditional path planning: the laborious task of setting accurate target points, especially when the riverbank's morphology is elusive. Such adaptability is indispensable for tasks like riverbank safety inspections and underwater pipe detection. However, one limitation of the proposed planner is evident. Strong winds and turbulent waves can influence the USV's orientation, making the LiDAR scans prone to fluctuations. While filters like the Kalman filter might refine the raw point cloud data, they could introduce latency, potentially jeopardizing the algorithm's real-time efficacy. In the future, it is imperative to field-test the RBFP on an actual USV, validating its capabilities outside of controlled simulations. Given the potential external disruptions in real-world settings, relying solely on IMUs might compromise pose accuracy. Consequently, our future endeavors will entail the fusion of RTK GPS with inertial sensors for enhanced state estimation. Furthermore, we aspire to harness multi-sensor fusion strategies--incorporating near-infrared cameras, millimeter-wave radar, and further LiDAR modalities--to counter external environmental interferences. By assimilating these avant-garde sensing techniques, we aim to fortify the precision and resilience of our riverbank following planner, ensuring its readiness for practical implementations. Conceptualization, Y.C. ; methodology, Y.C. ; software, Y.C. and Z.W. ; validation, Y.C. and Z.W. ; writing--original draft preparation, Y.C., Z.W., Y.Y., X.Z., E.G.L. and P.P. ; writing--review and editing, Y.C., Z.W., X.Z., Y.Y., E.G.L., P.P. and J.M; funding acquisition, Y.Y., X.Z. and J.M. All authors have read and agreed to the published version of the manuscript. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Scenario** & **Wind** & **Max [m]** & **Min [m]** & **Mean [m]** & **Variance [m]** & \(\pm\)**15\% Error Ratio** \\ \hline \multirow{4}{*}{Straight} & 0.0 & 23.67 & 19.58 & 20.99 & 0.43 & 96.97\% \\  & 0.5 & 23.68 & 19.57 & 20.98 & 0.42 & 96.99\% \\  & 1.0 & 23.76 & 19.58 & 20.99 & 0.43 & 96.89\% \\  & 2.0 & 23.85 & 19.59 & 21.02 & 0.44 & 96.82\% \\ \hline \multirow{4}{*}{Convex} & 0.0 & 35.68 & 8.34 & 21.42 & 24.95 & 66.97\% \\  & 0.5 & 35.69 & 8.25 & 21.36 & 24.65 & 67.27\% \\  & 1.0 & 35.69 & 8.14 & 21.31 & 24.58 & 67.45\% \\  & 2.0 & 35.69 & 7.86 & 21.23 & 25.12 & 67.51\% \\ \hline \multirow{4}{*}{Concave} & 0.0 & 35.69 & 4.48 & 20.94 & 14.31 & 61.23\% \\  & 0.5 & 35.59 & 4.49 & 20.92 & 14.51 & 61.23\% \\ \cline{1-1}  & 1.0 & 35.63 & 4.47 & 20.95 & 14.76 & 60.90\% \\ \cline{1-1}  & 2.0 & 35.61 & 4.50 & 20.90 & 14.83 & 61.23\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The relative distance of the USV from the riverbank. **Funding:** This research was funded by the Suzhou Science and Technology Project (SYG202122), the Key Programme Special Fund of Xi'an Jiaotong-Liverpool University (XJTLU) (KSF-A-19, KSF-E-65, KSF-P-02, KSF-E-54), Suzhou Municipal Key Laboratory for Intelligent Virtual Engineering (SZS202004), the Research Development Fund of XJTLU (RDF-19-02-23), the XJTLU AI University Research Centre, Jiangsu Province Engineering Research Centre of Data Science and Cognitive Computation at XJTLU and SIP AI innovation platform (YZCXPT2022103). **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable.