Autonomous landing in complex and hazardous terrains is a critical stage of planetary in-situ exploration and sample-return missions. The design of the landing trajectory has to seek a balance between safety and fuel economy. Based on the theorems of convex trajectory and curvature guidance law, this paper proposes an obstacle avoidance guidance method with an adaptive curvature adjusting mechanism. The method remains the advantage in obstacle avoidance of the existed curvature guidance, and can further minimize fuel consumption by adopting a global optimization technique with a specific curvature constraint. Firstly, the nonconvex curvature constraint is transformed into a second-order cone constraint to construct a standard convex programming problem. The curvature adjustment strategy is then designed to adapt the trajectory to varying terrain conditions. By introducing the successive convex technique, the adaptive curvature guidance strategy is also suitable for small celestial body landing problems in nonlinear dynamic environments. Simulations of typical planetary landing scenarios are conducted to verify the effectiveness of the proposed method in improving safety and fuel efficiency.

在复杂和危险的地形中自主着陆是行星原地探索和样品返回任务的关键阶段。着陆轨迹的设计必须在安全性和燃油经济性之间寻求平衡。基于凸轨迹定理和曲率引导律，提出了一种具有自适应曲率调节机制的避障引导方法。该方法保留了现有曲率引导避障的优势，并且通过采用具有特定曲率约束的全局优化技术，可以进一步降低油耗。首先，将非凸曲率约束转化为二阶锥约束，构造标准凸规划问题。然后设计曲率调整策略以使轨迹适应不同的地形条件。通过引入连续凸技术，自适应曲率引导策略也适用于非线性动态环境下的小天体着陆问题。对典型的行星着陆场景进行了模拟，以验证所提出的方法在提高安全性和燃油效率方面的有效性。