Development, Analysis, and Control of Series Elastic Actuator-Driven Robot Leg.

Chan Lee,Sehoon Oh

doi:10.3389/fnbot.2019.00017

Abstract

The mass-spring system-like behavior is a powerful analysis tool to simplify human running/locomotion and is also known as the Spring Loaded Inverted Pendulum (SLIP) model. Beyond being just an analysis tool, the SLIP model is utilized as a template for implementing human-like locomotion by using the articulated robot. Since the dynamics of the articulated robot exhibits complicated behavior when projected into the operational space of the SLIP template, various considerations are required, from the robot's mechanical design to its control and analysis. Hence, the required technologies are the realization of pure mass-spring behavior during the interaction with the ground and the robust position control capability in the operational space of the robot. This paper develops a robot leg driven by the Series Elastic Actuator (SEA), which is a suitable actuator system for interacting with the environment, such as the ground. A robust hybrid control method is developed for the SEA-driven robot leg to achieve the required technologies. Furthermore, the developed robot leg has biarticular coordination, which is a human-inspired design that can effectively transmit the actuator torque to the operational space. This paper also employs Rotating Workspace (RW), which specializes in the control of the biarticulated robots. Various experiments are conducted to verify the performance of the developed robot leg with the control methodology.

Highlights

Humans and animals’ dynamic walking has been attracting many engineers’ and scientists’ attention, and the dynamic walking of a robot itself has been a very prominent research topic for robotic engineers.Researches on dynamic walking can be categorized into two groups: an engineering approach and a scientific approach
This paper proposes a serial and systematic procedure to achieve Spring Loaded Inverted Pendulum (SLIP) dynamics by fully utilizing the advantage of the biarticular mechanism as well as the employment of Series Elastic Actuator (SEA) and Hybrid Control (HC) in Rotating Workspace (RW)
This paper has analyzed the dynamics of SEA and designed the Disturbance Observer (DOB)-based torque controller based on the dynamics

Summary

Introduction

Humans and animals’ dynamic walking has been attracting many engineers’ and scientists’ attention, and the dynamic walking of a robot itself has been a very prominent research topic for robotic engineers.Researches on dynamic walking can be categorized into two groups: an engineering approach and a scientific approach. Various research aiming to build biped robots and quadruped robots (Boaventura et al, 2013; Englsberger et al, 2014; Hutter et al, 2016; Kuindersma et al, 2016; Jung et al, 2018) is considered to be within this approach Walking algorithm theories such as Zero Moment Point stabilization are categorized into this research approach, whereas the scientific approach attempts to analyze actual human walking and derive a walking dynamic model (Seyfarth et al, 2002; Geyer et al, 2006). The main requirements to realize stable and periodic running of a robot are the realization of spring dynamics and attack angle control These correspond to the SLIP model-based locomotion as 2-fold: a pure massspring behavior during the ground interaction or stance phase is rendered, and the correct attack angle with regards to the momentum of the mass at the landing moment or incidence angle of the leg is required

Methods

Discussion

Conclusion