Search

• Variable stiffness design for a 3-legged asteroid probe. • Landing dynamics for soft landing on the 2016HO3 asteroid is modeled. • Response surface surrogate model is established for optimization. • Variable stiffness leg and pressing force are optimized. China plans to launch a probe to detect and sampling on the near-Earth asteroid 2016HO3 around 2025. In view of this, this paper discusses an alternative landing strategy with passive variable stiffness landing gears, which help to land the probe stably on the asteroid for sufficient sampling time. First, a three-legged lander is introduced, following which, a four-bar-linkage-based variable stiffness leg is designed considering the design constraint of landing clearance. Then, a numerical model of the probe for landing simulation is established. Moreover, a surrogate model is obtained using the second-order response surface method (RSM) to improve computational efficiency. Based on the surrogate, the variable stiffness leg and the pressing force are optimized to reduce the impact forces at touchdown and the landing time. Finally, the optimal solution is validated using the dynamics analysis model. [ABSTRACT FROM AUTHOR]

Maximum loads acting on aircraft structures generally arise when the aircraft is undergoing some form of acceleration, such as during landing. Landing, especially when considering rotorcrafts, is thus crucial in determining the operational load spectrum, and accurate predictions on the actual health/load level of the rotorcraft structure cannot be achieved unless a database comprising the structural response in various landing conditions is available. An effective means to create a structural response database relies on the modeling and simulation of the items and phenomena of concern. The structural response to rotorcraft landing is an underrated topic in the open scientific literature, and tools for the landing event simulation are lacking. In the present work, a coupled sequential simulation strategy is proposed and experimentally verified. This approach divides the complex landing problem into two separate domains, namely a dynamic domain, which is ruled by a multibody model, and a structural domain, which relies on a finite element model (FEM). The dynamic analysis is performed first, calculating a set of intermediate parameters that are provided as input to the subsequent structural analysis. Two approaches are compared, using displacements and forces at specific airframe locations, respectively, as the link between the dynamic and structural domains.

A simplified model is presented for cushion legs. Shell elements and beam elements are separately used to simulate the cylinders, taking the flexibility and the friction force of landing legs into consideration. Connector elements are used to present the dynamic performance of crushable material, improving the computational efficiency. Implicit dynamics procedure is introduced to ensure the calculation accuracy. The results show that shell element model can reflect the effect of legs' flexibility on landing performance better, meanwhile, as friction coefficient increasing, the energy absorption capabilities of legs are decreased. [ABSTRACT FROM AUTHOR]

Maximum loads acting on aircraft structures generally arise when the aircraft is undergoing some form of acceleration, such as during landing. Landing, especially when considering rotorcrafts, is thus crucial in determining the operational load spectrum, and accurate predictions on the actual health/load level of the rotorcraft structure cannot be achieved unless a database comprising the structural response in various landing conditions is available. An effective means to create a structural response database relies on the modeling and simulation of the items and phenomena of concern. The structural response to rotorcraft landing is an underrated topic in the open scientific literature, and tools for the landing event simulation are lacking. In the present work, a coupled sequential simulation strategy is proposed and experimentally verified. This approach divides the complex landing problem into two separate domains, namely a dynamic domain, which is ruled by a multibody model, and a structural domain, which relies on a finite element model (FEM). The dynamic analysis is performed first, calculating a set of intermediate parameters that are provided as input to the subsequent structural analysis. Two approaches are compared, using displacements and forces at specific airframe locations, respectively, as the link between the dynamic and structural domains. [ABSTRACT FROM AUTHOR]