Discussion on the Stiffness of the Drive Chain in the Legs of Biped Robots

Ruilong Du,Daming Nie,Sumian Song,Haihui Yuan,Jason Gu

doi:10.3390/act11030079

Abstract

Biped robots’ locomotion is realized by driving the joint motion via a drive chain. Therefore, the stiffness of the drive chain is an important factor that affects the drive performance and can influence the locomotion behavior of the biped robot. This work focused on the influence of the stiffness of the leg’s drive chain using a mass-spring model based on the biped robot AIRO built in Zhejiang Lab. Methods for determination of the parameters in the proposed model were presented, including the use of ANSYS Workbench to determine the stiffness parameters and the determination of the inertia parameters by dynamic modelling of the biped robot. Simulation results show that special attention should be paid to the stiffness of the drive train of the leg when designing a biped robot to ensure the walking capability of the robot. Using the model proposed in this work, relations between the executed accuracy of the joint trajectories and the stiffness can be analyzed; after that, the stiffness parameters can be optimized. In addition, simulation results also showed that attention should be paid to manufacturing tolerances to ensure the symmetry of the legs of the bipedal robot in order to reduce the vibration of the robot body. Experiments were conducted on AIRO for validating the proposed model and the simulation analysis.

Highlights

Biped robots have attracted a lot of attention in recent years for their unique advantage of human-like structure, which allows them to work in a human-built environment [1]
Though developed by different research groups, what these biped robots have in common is the anthropomorphic leg structure, which is comprised of mechanical components, drive systems and transmission mechanisms, such as the thigh, the electric motor and the linkage, mechanism, Typically, biped robots are driven by electric motors [7,8], hydraulics [9,10] or pneumatics [11,12]
Elastic deformation would occur when subjected to external forces during the biped robot’s locomotion process; the actual execution of the joint trajectory might deviate from the expected trajectory

Summary

Introduction

Biped robots have attracted a lot of attention in recent years for their unique advantage of human-like structure, which allows them to work in a human-built environment [1]. With respect to the publications of biped robots, most of them address the issues of bionic structure designs, gait panning, and control strategies [13–15]. In these publications, the biped robots are usually taken as rigid bodies, which is not feasible in the real design, regardless of the driving approach. Elastic deformation would occur when subjected to external forces during the biped robot’s locomotion process; the actual execution of the joint trajectory might deviate from the expected trajectory. Due to the elastic deformation of the drive chain of the knee joint motion, the execution angle position of the knee joint may deviate from its gait planning

Methods

Results

Conclusion