Journal of Bionic Engineering (2024) 21:607–634  https://doi.org/10.1007/s42235-023-00468-1 

Development of Wheel-Legged Biped Robots: A Review 

Xuefei Liu1  · Yi Sun1  · Shikun Wen1  · Kai Cao1  · Qian Qi1  · Xiaoshu Zhang1  · Huan Shen1  · Guangming Chen1  · Jiajun Xu1  · Aihong Ji1,2 

1 Lab of Locomotion Bioinspiration and Intelligent Robots, College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, China
2 State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China

Abstract The wheel-legged biped robot is a typical ground-based mobile robot that can combine the high velocity and high efciency pertaining to wheeled motion and the strong, obstacle-crossing performance associated with legged motion. These robots have gradually exhibited satisfactory application potential in various harsh scenarios such as rubble rescue, military operations, and wilderness exploration. Wheel-legged biped robots are divided into four categories according to the open–close chain structure forms and operation task modes, and the latest technology research status is summarized in this paper. The hardware control system, control method, and application are analyzed, and the dynamic balance control for the two-wheel, biomimetic jumping control for the legs and whole-body control for integrating the wheels and legs are analyzed. In summary, it is observed that the current research exhibits problems, such as the insufcient application of novel materials and a rigid–fexible coupling design; the limited application of the advanced, intelligent control methods; the inadequate understanding of the bionic jumping mechanisms in robot legs; and the insufcient coordination ability of the multi-modal motion, which do not exhibit practical application for the wheel-legged biped robots. Finally, this study discusses the key research directions and development trends for the wheel-legged biped robots. 

Keywords Wheel-legged biped robot · Wheeled motion · Legged motion · Control strategy