Lunar surface soft-landing analysis of a novel six-legged mobile lander with repetitive landing capacity

The autonomous robots consisting of an immovable lander and a rover are widely deployed to explore extraterrestrial planets. Two main drawbacks limit the development of this cooperative work mode: (1) it cannot perform soft-landing missions repeatedly on the planet, owing to the damage of buffer structure during soft-landing. (2) the rover's detection area is restricted to the vicinity of the immovable lander. To overcome these problems, we have designed an innovative six-legged mobile lander with repetitive landing capacity, called "HexaMRL", which integrates the functions of a lander and a rover including folding, deploying, repetitive landing, and walking. This novel robot's legs adopted hybrid mechanism with active and passive compliance. Therefore, it remains to be a great challenge to analyze the robot soft-landing capacity which is determined by the parameters such as spring stiffness coefficient, damper damping coefficient, and initial tiptoe position. In order to solve the problem, the dynamic modeling and assessment criteria were established. The soft-landing process was analyzed through three numerical simulations using three sets of representative parameters based on dynamic model and the set of best effective parameters was chosen to apply in soft-landing experiment on a 5-DOF lunar gravity testing platform (5-DOF LGTP). The experiments were further verified that the selected parameters met the requirement of soft landing on the lunar surface. The HexaMRL provides novel insight for the next generation equipment for lunar exploration, which may be an efficient solution to the extraterrestrial planet exploration.