A Review on the Stability of Biped Robots

Abstract

The use of robotics has been increasing in various applications in industrial, medical, entertainment, and disaster management. Biped robotics is one of the most popular specialized fields. This paper starts with a discussion on the application of robotics and argues that bipeds are an important domain of robotics due to their universal application. Stability is an important issue for bipeds. The present paper is an endeavour to review the important topic of stability. The literature review on stability of bipeds in this paper is broadly divided into two parts: Stable gait generation, also regarded as dynamic stability, and stability against disturbance, also regarded as stance stability. Stable gait generation techniques on various geometrical surfaces, such as level ground, inclined grounds, uneven grounds, stairs, and wide ditch (crossing), are discussed. Stable locomotion for avoiding obstacles is discussed as well. For stance stability, the discussion is broadly divided into two parts: with controller and without controller. For small disturbances that do not cause significant changes in the system’s states, proper Centre of mass (CoM) placement ensures stability; controls at the joints are not needed. However, to ensure stability against sufficiently large disturbances causing significant changes in the system’s states, a proper controller strategy must be developed. All these aspects of stability against disturbances are discussed in detail. After critical review of the above aspects of stability in the literature, existing research gaps are identified, and the possible future works to address them are discussed.