We present a novel controller design on a robotic locomotor that combines an aerial vehicle with a spring-loaded leg. The main motivation is to enable the terrestrial locomotion capability on aerial vehicles so that they are carrying heavy loads: heavy enough that flying is no longer possible, e.g., when the thrust-to-weight ratio (TWR) is small. The robot is designed with a pogo-stick leg and a quadrotor, and thus it is named as PogoX. We show that with a simple and lightweight spring-loaded leg, the robot is capable of hopping with TWR $<1$. The control of hopping is realized via two components: a vertical height control via control Lyapunov function-based energy shaping, and a step-to-step (S2S) dynamics based horizontal velocity control that is inspired by the hopping of the Spring-Loaded Inverted Pendulum (SLIP). The controller is successfully realized on the physical robot, showing dynamic terrestrial locomotion of PogoX which can hop at variable heights and different horizontal velocities with robustness to ground height variations and external pushes.

翻译：我们提出了一种新型控制器设计，用于将飞行器与弹簧负载腿相结合的机器人运动器。主要动机是赋予飞行器地面运动能力，使其能够承载重物——重到无法飞行，例如推力重量比（TWR）较小时。该机器人采用弹簧杆腿与四旋翼飞行器设计，因此命名为PogoX。我们证明，通过简单且轻量化的弹簧负载腿，机器人能够在TWR<1的条件下实现跳跃。跳跃控制通过两个组件实现：基于控制李雅普诺夫函数的能量整形实现垂直高度控制，以及受弹簧负载倒立摆（SLIP）启发、基于步态动力学（S2S）的水平速度控制。该控制器已成功在实体机器人上实现，展示了PogoX的动态地面运动能力：可在不同高度和水平速度下跳跃，并对地面高度变化和外部推力具有鲁棒性。