Design and Experimental Verification of a Jumping Legged Robot for Martian Lava Tube Exploration

The potential of Martian lava tubes for resource extraction and habitat sheltering highlights the need for robots capable to undertake the grueling task of their exploration. Driven by this motivation, in this work we introduce a legged robot system optimized for jumping in the low gravity of Mars, designed with leg configurations adaptable to both bipedal and quadrupedal systems. This design utilizes torque-controlled actuators coupled with springs for high-power jumping, robust locomotion, and an energy-efficient resting pose. Key design features include a 5-bar mechanism as leg concept, combined with springs connected by a high-strength cord. The selected 5-bar link lengths and spring stiffness were optimized for maximizing the jump height in Martian gravity and realized as a robot leg. Two such legs combined with a compact body allowed jump testing of a bipedal prototype. The robot is 0.472 m tall and weighs 7.9 kg. Jump testing with significant safety margins resulted in a measured jump height of 1.141 m in Earth's gravity, while a total of 4 jumping experiments are presented. Simulations utilizing the full motor torque and kinematic limits of the design resulted in a maximum possible jump height of 1.52 m in Earth's gravity and 3.63 m in Mars' gravity, highlighting the versatility of jumping as a form of locomotion and overcoming obstacles in lower gravity.