A Novel Shape Memory Alloy Modular Robot with Spatially Stable Structure

Soft robots exhibit significant flexibility but normally lack stability owing to their inherent low stiffness. Current solutions for achieving variable stiffness or implementing lock mechanisms tend to involve complex structures. Additionally, passive solutions like bistable and multistate mechanisms lack spatial stable characteristics. This study presents a novel shape memory alloy (SMA) modular robot with spatially stable structure, by utilizing gooseneck as the backbone. This is the first time that a concept of spatially stable structure is proposed. When the power is off, the robot can still maintain its current posture in three-dimensional space and resist external disturbance. The SMA spring and gooseneck are characterized, elucidating the mechanism behind achieving spatial stability. Then, a controller based on the inverse kinematics is designed, and validated by experiments. The results demonstrate the structural stability of the robot. Specifically, it can withstand a maximum external force of 2.5 N (0.0875 Nm) when bent at an angle of 20 degrees without consuming energy. Moreover, with the assistance of the SMA spring, this resistance capacity surpasses 5 N (0.175 Nm). This article presents a novel shape memory alloy (SMA) modular robot with spatially stable structure, by utilizing gooseneck as the backbone. It is the first time that a concept of spatially stable structure is proposed. This innovation significantly enhances the robot's stability and its ability to resist external disturbances without the need for additional control mechanisms or energy consumption.image (c) 2024 WILEY-VCH GmbH