Zhen Yan’s research while affiliated with Harbin Institute of Technology and other places

Traditional skid or wheeled landing gears fall short in meeting the rigorous requirements of challenging surfaces such as rugged terrain and swaying deck, which restraints the application in extreme tasks including disaster rescue, cargo transportation as well as ship-relevant operations. This paper proposes a novel legged landing gear scheme for the unmanned helicopter in dealing with terrain irregularity by fully leveraging the antagonistic mechanism of cables to effectively reduce the power demand of indispensable actuators. The tailored control framework combining the whole body control (WBC) and the contact force optimization is developed for the legged landing gear to ameliorate internal force conflicts amongst individual legs at the landing stage. Experiments on an unmanned helicopter prototype are conducted to demonstrate the effectiveness of the legged landing gear in achieving stable slope landing and fuselage posture adjusting, enhancing the adaptation of the unmanned helicopter in unstructured environments.

In order to investigate the landing process of a vertical landing reusable vehicle, a dynamic model with a complex nonlinear dissipative element is established based on the discrete impulse step approach, which includes a three-dimensional multi-impact model considering friction and material compliance, and a multistage aluminum honeycomb theoretical model. The normal two-stiffness spring model is adopted in the foot–ground impact model, two motion patterns (stick and slip) are considered on the tangential plane and the structural changes caused by buffering behavior are included, and the energy conversion during the impact follows the law of conservation of energy. The state transition method is used to solve the dynamic stability convergence problem of the vehicle under the coupling effect of impact and buffering deformation in the primary impulse space. Landing experiments on a scaled physical reusable vehicle prototype are conducted to demonstrate that the theoretical results exhibit good agreement with the experimental data.

The reusable launch vehicle (RLV) presents a new avenue for reducing cost of space transportation. The landing mechanism, which provides landing support and impact absorption, is a vital component of the RLV at final stage of recovery. This study proposes a novel legged deployable landing mechanism (LDLM) for RLV. The Watt-II six-bar mechanism is adopted to obtain the preferred configuration via the application of the linkage variation approach. To endow the proposed LDLM with advantages of large landing support region, lightweight, and reasonable linkage internal forces, a multi-objective optimization paradigm is developed. Furthermore, the optimal scale parameters for guiding the LDLM prototype design is obtained numerically using the non-dominated sorting genetic algorithm-II (NSGA-II) evolutionary algorithm. A fully-functional scaled RLV prototype is developed by integrating the gravity-governed deploying scheme to facilitate unfolding action to avoid full-range actuation, a dual-backup locking mechanism to enhance reliability of structure stiffening as fully deployed, and a shock absorber (SA) with multistage honeycomb to offer reliable shock absorbing performance. The experimental results demonstrate that the proposed LDLM is capable of providing rapid and smooth deployment (duration less than 1.5 s) with mild posture disturbance to the cabin (yaw and pitch fluctuations less than 6°). In addition, it provides satisfactory impact attenuation (acceleration peak less than 10g) in the 0.2 m freefall test, which makes the proposed LDLM a potential alternative for developing future RLV archetype.