Design and Control Scheme Of A Rigid-flexible Coupled Duel-arm Hug Robots*

The humanoid design of robots can maximize the imitation of real human work, facilitate integrated control with other devices, and offer good safety and human-machine interaction. These attributes have led to their widespread application in various fields. The most critical component of the robot’s structure, the arm, can be categorized into three types based on stiffness characteristics: rigid robotic arms, flexible robotic arms, and rigid-flexible coupled robotic arms. Rigid robotic arms are characterized by high load capacity, high precision, high repeatability, and high speed. Their development is relatively mature across different fields. However, due to their low degrees of freedom, poor environmental adaptability, and unsafe human-machine interaction, they are difficult to apply in complex, unstructured scenarios. Currently, the design and manufacturing of flexible robotic arms have become a research hotspot in many engineering disciplines. Compared to traditional bulky rigid robotic arms, flexible robotic arms offer advantages such as smaller size, lower energy consumption, and reduced cost. However, their lower stiffness can lead to structural fatigue, and their precision is affected by elastic deformation. During motion or when subjected to external disturbances, flexible robotic arms are prone to vibration issues, which can reduce control accuracy and compromise the stability of the system. This paper focuses on the scenario of human-robot hugging and designs a safe and reliable rigid-flexible coupled dual-arm robot that can provide psychological comfort. The rigid-flexible coupled robotic arm primarily consists of a rigid skeleton, variable stiffness joints, and flexible muscles. Driven by pneumatic actuators, it can achieve sensing and human-machine interaction. The rigid-flexible coupled design ensures both the end-effector output force and safety. The research content mainly includes the structural design of the dual-arm robot, model establishment, simulation and control scheme of the hugging motion, and human-robot interaction hugging experiments.