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  4. Bipedal walking and push recovery with a stepping strategy based on time-projection control
 
research article

Bipedal walking and push recovery with a stepping strategy based on time-projection control

Faraji, Salman  
•
Razavi, Hamed  
•
Ijspeert, Auke J.  
April 1, 2019
International Journal Of Robotics Research

In this paper, we present a simple control framework for online push recovery on biped robots with dynamic stepping properties. Owing to relatively heavy legs in our humanoid robot COMAN, we use a linear model called 3LP, which is composed of three pendulums to take swing and torso dynamics into account. Based on 3LP equations, we formulate discrete linear quadratic regulator (LQR) controllers and use a particular time-projection method to adjust footstep locations during the motion continuously. This process, which is based on pelvis and swing foot tracking errors, naturally considers swing dynamics and leads to leg-retraction properties. Suggested adjustments are added to the Cartesian 3LP gaits and converted into joint-space trajectories through inverse kinematics. Fixed and adaptive foot lift strategies are also used to ensure enough ground clearance in perturbed walking conditions. The proposed control architecture is robust, yet uses very simple state estimation and basic position tracking. We rely on series elastic actuators to absorb impacts while introducing simple laws to compensate for spring compressions. Extensive experiments on COMAN (real) and Atlas (simulated) robots demonstrate the functionality of different control blocks and prove the effectiveness of time-projection in extreme push recovery scenarios. We also show self-produced and emergent walking gaits when the robot is subject to continuous dragging forces. These gaits feature dynamic walking robustness with minimal reliance on the ankles and avoiding any active zero moment point (ZMP) control. The proposed architecture is therefore generic, computationally very fast and yet with no critical parameter to tune.

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Type
research article
DOI
10.1177/0278364919835606
Web of Science ID

WOS:000465025200004

Author(s)
Faraji, Salman  
Razavi, Hamed  
Ijspeert, Auke J.  
Date Issued

2019-04-01

Publisher

SAGE PUBLICATIONS LTD

Published in
International Journal Of Robotics Research
Volume

38

Issue

5

Start page

587

End page

611

Subjects

Robotics

•

Robotics

•

humanoid robot

•

dynamic walking

•

time-projection

•

continuous control

•

linear model

•

intermittent push recovery

•

capturability-based analysis

•

pattern generation

•

legged locomotion

•

robot

•

gait

•

efficient

•

optimization

•

dynamics

•

forces

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
BIOROB  
Available on Infoscience
June 18, 2019
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/157024
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