Integral Acceleration Generation for Slip Avoidance in a Planar Humanoid Robot

Slip occurrence puts not only the humans but also the humanoid robots into dangerous situations. Although the detection and the estimation of slip have been well researched, studies on slip avoidance control in a humanoid robot are rare. Previous methods used to restrict the horizontal motion or regulate the vertical motion of the humanoid robot did not take the important rotational motion into account. This study proposes an integral acceleration generation method for slip avoidance that meets the real-time requirements, using the sagittal plane as an example. The proposed method makes full use of all the motions related to the slip in the sagittal plane to prevent the slip, including the translational and the rotational motions. The simulations and experiments on the physical humanoid robot demonstrate the effectiveness of the presented method.

I. Introduction

Humanoid robots provide advantages when assisting people in human environments. In recent decades, some well-known prototypes have been developed, e.g., WABIAN [1], ASIMO [2], HRP [3], LOLA [4], SARCOS PRIMUS [5], and KHR [6]. Encouraging achievements have been made in the basic principles and techniques of humanoid robot development [7] –[14], including balance control which is one of the most important techniques used to prevent a robot from tipping over. Therefore, most of the previous studies focused on balance control in the humanoid robot when walking, running, or jumping, and many effective controllers and criteria for balance evaluation have been proposed, e.g., the zero-moment point (ZMP) [15] , the foot rotation indicator [16].