提出可约束轨迹曲率的向量场,让非完整机器人安全抵达目标。
Curvature-Constrained Vector Field for Motion Planning of Nonholonomic Robots
- 通过融合基础流场构建曲率受限向量场,统一设计控制律。
- 实测与仿真表明轨迹曲率可控,且在饱和情况下仍能收敛。
- 适用于轮式、固定翼无人机等实际平台,具强实用性。
向量场在处理非完整运动规划时具有优势,能为机器人提供参考朝向。然而,在额外引入曲率约束时面临挑战,因曲率有界向量场的设计与欠驱动下的跟踪控制器相互耦合。本文提出一种新框架,协同设计向量场与控制律,引导非完整机器人以曲率受限轨迹到达目标配置。首先,通过引入目标正极限集,使机器人可根据不同动力学和任务需求收敛或经过目标点。其次,通过在工作空间中混合与分布基础流场,构建曲率受限向量场(CVF),并设计含动态增益的饱和控制律,即使在饱和情况下,跟踪误差仍持续减小。在此控制律下,满足运动学约束的非完整机器人能稳定跟踪参考CVF,并以有界曲率轨迹收敛至目标正极限集。数值仿真显示,该方法优于其他基于向量场的算法。在阿克曼式地面车辆与半物理固定翼无人机上的实验表明,该方法可在真实场景中有效实施。
原文摘要 · Abstract (English)
Vector fields are advantageous in handling nonholonomic motion planning as they provide reference orientation for robots. However, additionally incorporating curvature constraints becomes challenging, due to the interconnection between the design of the curvature-bounded vector field and the tracking controller under underactuation. In this paper, we present a novel framework to co-develop the vector field and the control laws, guiding the nonholonomic robot to the target configuration with curvature-bounded trajectory. First, we formulate the problem by introducing the target positive limit set, which allows the robot to converge to or pass through the target configuration, depending on different dynamics and tasks. Next, we construct a curvature-constrained vector field (CVF) via blending and distributing basic flow fields in workspace and propose the saturated control laws with a dynamic gain, under which the tracking error's magnitude decreases even when saturation occurs. Under the control laws, kinematically constrained nonholonomic robots are guaranteed to track the reference CVF and converge to the target positive limit set with bounded trajectory curvature. Numerical simulations show that the proposed CVF method outperforms other vector-field-based algorithms. Experiments on Ackermann UGVs and semi-physical fixed-wing UAVs demonstrate that the method can be effectively implemented in real-world scenarios.
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