Journal of South China University of Technology(Natural Science Edition) ›› 2025, Vol. 53 ›› Issue (10): 131-144.doi: 10.12141/j.issn.1000-565X.240228

• Mechanical Transmission System • Previous Articles     Next Articles

History, Present Situation and Prospect of Research on Leg Configuration of Humanoid Robot

DING Hongyu1,2  SHI Zhaoyao3  FU Chunjiang4   

  1. 1. School of Mechanical and Energy Engineering, Guangdong Ocean University, Yangjiang 529500, Guangdong, China;

    2. Shenzhen Research Institute, Guangdong Ocean University, Shenzhen 518116, Guangdong, China;

    3. Beijing Engineering Research Center of Precision Measurement Technology and Instruments, Beijing University of Technology, Beijing 100124, China;

    4. Humanoid innovation center, UBTECH Robotics, Inc., Shenzhen 518052, Guangdong, China

  • Online:2025-10-25 Published:2025-05-30

Abstract:

The motion performance of humanoid robots has not fully reached the level of human beings, which is one of the factors affecting its large-scale industrial application. Such performance gaps stem not only from control algorithm limitations but also from mechanical design constraints, where the leg configuration plays a decisive role in the robot's dynamic stability, payload capacity, and energy efficiency.The leg configuration has an important effect on the motion performance of humanoid robot. The origin, history and status of leg configurations of humanoid robots at home and abroad are studied. Currently, the leg configurations of humanoid robots are primarily categorized into three types: serial, parallel, and hybrid serial-parallel configurations, with their structural characteristics significantly influencing motion performance.The series, parallel and series-parallel configurations are analyzed and their performance characteristics are compared. The serial configuration offers a large workspace and high flexibility, but its relatively lower stiffness—due to the extended joint transmission chain—compromises load-bearing capacity. In contrast, the parallel configuration provides high stiffness and rapid dynamic response, albeit with limited motion range. The hybrid serial-parallel design combines the strengths of both, achieving balanced stiffness and flexibility, which has increasingly made it a key research focus in recent years. The technical difficulties and hot spots in the study of leg configuration are discussed. The development trend is pointed out: the leg is developing from single series configuration to parallel and series-parallel configuration. The leg actuator develops from rigid actuator to elastic actuator and quasi direct drive actuator. The legs only use the rotary actuator to develop in the direction of rotation and linear actuator. The control is developing from position control to torque control and hybrid control of force and position. The research is of great significance for promoting the technological progress and industrial landing of humanoid robots.

Key words: series-parallel, leg configuration, actuator, motion control, humanoid robot