提出一种无饱和的有限时间轨迹规划方法,让非完整机器人更安全高效地抵达目标。
Finite-Time Curvature-Constrained Vector Field for Saturation-Free Motion Planning of Nonholonomic Robots

- 用互补增益构造曲率受限的向量场,实现有限时间收敛
- 控制输入不超限,且无需雅可比信息,实测验证性能提升
- 适合对安全性与实时性要求高的无人车等移动机器人
精确引导机器人到达目标位姿是工程中的基本问题,但对非完整移动机器人仍具挑战。向量场(VFs)通过定义工作空间内各点的期望运动方向,为反馈控制提供自然框架。然而,现有基于向量场的方法通常无法显式生成满足曲率约束的轨迹,导致执行器限制常通过输入饱和来强制执行,这可能破坏稳定性保证并降低闭环性能。此外,这些方法一般仅保证渐近收敛,缺乏明确的设定时间边界。为此,本文提出一种广义运动规划与控制框架,包含有限时间曲率约束向量场(FT-C2VF)和无饱和控制律。根据运动目标,该框架可使机器人在有限时间内到达目标或周期性穿越目标。首先,通过互补增益构建FT-C2VF,确保积分曲线曲率连续、有界且随径向比单调递减;其次,设计了一种几乎全局C1光滑、无饱和的控制器,无需雅可比信息即可跟踪FT-C2VF,同时保持所有控制输入在预设执行器极限内;第三,动力系统分析证明了目标平衡点的几乎全局有限时间稳定性。数值仿真显示性能优于代表性向量场方法,室外实验在阿克曼转向车辆上验证了该方法的有效性与鲁棒性。
原文摘要 · Abstract (English)
Accurately steering a robot to a target configuration is fundamental in engineering, yet remains challenging for nonholonomic mobile robots. Vector fields (VFs) provide a natural framework by specifying desired motion directions throughout the workspace and enabling direct integration with feedback control. However, most existing VF-based methods cannot explicitly generate trajectories satisfying curvature constraints. Actuator limits are therefore often enforced by input saturation, which may invalidate stability guarantees and degrade closed-loop performance when not considered in controller design. In addition, these methods usually ensure only asymptotic convergence without an explicit settling-time bound. To address these issues, we propose a generalized motion planning and control framework consisting of a finite-time curvature-constrained vector field (FT-C2VF) and a saturation-free control law. Depending on the motion objective, the framework drives the robot to the target configuration in finite time or through it periodically. First, the FT-C2VF is constructed using complementary gains to achieve finite-time convergence while ensuring that the curvature of its integral curves is continuous, bounded, and monotonically decreasing with the radial ratio. Second, an almost globally C1-smooth, saturation-free controller is developed to track the FT-C2VF without Jacobian information, while keeping all control inputs within prescribed actuator limits. Third, dynamical-systems analysis establishes almost-global finite-time stability of the target equilibrium. Numerical simulations show improved performance over representative VF-based methods, and outdoor experiments on an Ackermann-steered vehicle confirm the effectiveness and robustness of the proposed approach.
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