Robotic mobility in microgravity is necessary to expand human utilization and exploration of outer space. Bio-inspired multi-legged robots are a possible solution for safe and precise locomotion. However, a dynamic motion of a robot in microgravity can lead to failures due to gripper detachment caused by excessive motion reactions. We propose a novel Reaction-Aware Motion Planning (RAMP) to improve locomotion safety in microgravity, decreasing the risk of losing contact with the terrain surface by reducing the robot's momentum change. RAMP minimizes the swing momentum with a Low-Reaction Swing Trajectory (LRST) while distributing this momentum to the whole body, ensuring zero velocity for the supporting grippers and minimizing motion reactions. We verify the proposed approach with dynamic simulations indicating the capability of RAMP to generate a safe motion without detachment of the supporting grippers, resulting in the robot reaching its specified location. We further validate RAMP in experiments with an air-floating system, demonstrating a significant reduction in reaction forces and improved mobility in microgravity.

Owing to the irregular terrain and microgravity environment of an asteroid, an appropriate locomotion mechanism is required for exploring the asteroid by a robot. In this paper, a ground grip locomotive robot is proposed. One of the most important requirements of the robot is the development of the finger gripping mechanism that can be attached on an uneven surface. To meet this requirement, grip condition and friction characteristics between the finger and the surface need to be understood. Therefore, we conducted an experimental evaluation of gripping characteristics by measuring the coefficients of friction between several types of fingers and simulated grounds. Moreover, the range of possible gripping angles for simulated ground was determined by conditional equations and confirmed by an experiment of gripping the ground using an air-floating system. In this paper, conical shape is shown to be effective for ground grip locomotive robot.