A virtual parallel model for the buffer landing of multi-legged landing gear

Small offshore platforms rock and heave under the impact of waves. The adaptive landing gear should reduce the impact force between the landing legs and the platform while keeping the unmanned aerial vehicle (UAV) level. In this paper, a general virtual parallel model is proposed to describe the coupling relationship between multi-legged landing gear and the platform during buffer landing. Based on Lie group theory, a method of constructing various types of landing gear as a virtual parallel model is proposed. The landing gear base, the legs and the ground can be established as a unified parallel mechanism. Based on the virtual parallel model, the landing stiffness is established to evaluate the buffering performance of the landing gear in the pre-landing posture. A buffer landing surface which can make the landing gear obtain superior buffering effect can be obtained in the workspace through the case analysis. A buffer landing strategy based on virtual parallel model is established. The feasibility and effectiveness of the control strategy is verified by simulations and prototype experiments.