An overview of the underactuated biped robots

This paper presents an overview on underactuated biped robots. Firstly, background, latest research and characteristics of underactuated biped robot are introduced. Secondly, the model of underactuated biped walking system is described. And then the stability criterion based on hybrid zero dynamics theory and the Poincaré map is discussed. Meanwhile, commonly used methods for off-line gait planning and control strategies are analyzed. Finally, several open problems need further research and the development directions are indicated and discussed.

I. Introduction and Review

Biped motion is the specific movement of higher life forms. As a mechanical recreation of biological bipedal movement, biped robot (also known as humanoid robot) is one of the hot topics in robotics development. Current research on biped walking robot is mainly flat-footed and bases on ZMP (zero moment point) stability criterion [1] and trajectory tracking control method. As the limitations of the mechanical structure, motion planning and control methods, the robots generally have problems such as stiff motion, unnatural gait, low speed and large energy consumption. In order to solve these problems, underactuated biped robot, a new robot svstem, is proposed.