The surface of a minor body in space features a harsh terrain and microgravity. To explore such surfaces in detail, a robot with an appropriate moving mechanism is required. To this end, we proposed a robot that moves by gripping the surface like a rock climber. We focus on the robot's gait, where the motion of the idling arm generates the reaction force that acts on the gripper of the supporting arm. The reaction force needs to be controlled to maintain a grip without slipping. Therefore, we formulate a simultaneous control law that combines the tip position control of the idling arm with reactionless control by utilizing the reaction null-space. Moreover, the validity of the control law was confirmed by an experiment involving an air floating system under microgravity. Furthermore, a planar simulation clarified that the robot can move continuously on an irregular terrain.

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.