In this paper, we consider the tracking of arbitrary curvilinear geometric paths in three-dimensional output spaces of unmanned aerial vehicles (UAVs) without pre-specified timing requirements, commonly referred to as path-following problems, subjected to bounded inputs. Specifically, we propose a novel nonlinear path-following guidance law for a UAV that enables it to follow any smooth curvilinear path in three dimensions while accounting for the bounded control authority in the design. The proposed solution offers a general treatment of the path-following problem by removing the dependency on the path's geometry, which makes it applicable to paths with varying levels of complexity and smooth curvatures. Additionally, the proposed strategy draws inspiration from the pursuit guidance approach, which is known for its simplicity and ease of implementation. Theoretical analysis guarantees that the UAV converges to its desired path within a fixed time and remains on it irrespective of its initial configuration with respect to the path. Finally, the simulations demonstrate the merits and effectiveness of the proposed guidance strategy through a wide range of engagement scenarios, showcasing the UAV's ability to follow diverse curvilinear paths accurately.

翻译：本文研究了无人机在三维输出空间中跟踪任意曲线几何路径的问题，该问题不预设时序要求（通常称为路径跟随问题），且受限于有界输入。具体而言，我们提出了一种新颖的非线性路径跟随制导律，使无人机能够在考虑设计中控制权限有界的情况下，跟随任意三维光滑曲线路径。所提出的解决方案通过消除对路径几何形状的依赖，为路径跟随问题提供了一种通用处理方法，使其适用于不同复杂度和光滑曲率的路径。此外，该策略从追踪制导方法中汲取灵感，该方法以简单性和易于实现而著称。理论分析保证无人机在固定时间内收敛到期望路径，并无论其相对于路径的初始配置如何，都能保持在路径上。最后，仿真通过多种交战场景展示了所提制导策略的优点和有效性，证明了无人机能够准确跟随各种曲线路径。