Planning a safe and dynamic flyable trajectory for unmanned aerial vehicle (UAV) is the precondition for autonomous flight. Considering environmental complexity and flight safety under limited motor speed, we proposed a new time-segmented trajectory planning method, which can ensure motor speed within the allowable range and achieve safe flight. Firstly, the candidate trajectory for quadrotor UAV is expressed by high-order polynomials. Herein, polynomial is used as the expression of trajectory, and nonlinear programming (NLP) is used to calculate polynomial coefficient. Then, two strategies and an initial value calculation method are proposed to improve the efficiency of NLP. Furthermore, aiming at the problem that the initial trajectory of UAV motor cannot meet the current speed limit constraint after the motor speed drops, an adjustment strategy based on feasible trajectory is designed. The method presented in this paper not only enhances flexibility of the flight process, improves solving efficiency of the algorithm but also enables UAV to continue flying when the motor speed is limited. Finally, simulation analysis and comparison illustrate the effectiveness and superiority of the proposed method.

中文翻译：

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有限电机速度下四旋翼飞行器的快速轨迹生成

规划无人机安全、动态的飞行轨迹是实现自主飞行的前提。考虑到环境复杂性和有限电机速度下的飞行安全性，我们提出了一种新的分时轨迹规划方法，可以保证电机速度在允许范围内，实现安全飞行。首先，用高阶多项式表达四旋翼无人机的候选轨迹。这里，采用多项式作为轨迹的表达，并采用非线性规划(NLP)来计算多项式系数。然后，提出了两种策略和初始值计算方法来提高NLP的效率。此外，针对无人机电机转速下降后初始轨迹无法满足当前限速约束的问题，设计了基于可行轨迹的调整策略。本文提出的方法不仅增强了飞行过程的灵活性，提高了算法的求解效率，而且能够使无人机在电机速度受到限制的情况下继续飞行。最后，仿真分析和比较说明了该方法的有效性和优越性。