Sliding mode control of underactuated biped robots

Mehdi Nikkhah, Hashem Ashrafiuon, Farbod Fahimi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Scopus citations


This paper presents a robust tracking control algorithm for underactuated biped robots. The biped considered in this work is modeled as a five-link planar robot with four actuators located at hip and knee joints to control the joint angles. The control law is defined based on the sliding mode control approach. The objective of the controller is to generate stable walking based on predefined desired trajectories. The planning of the trajectory in swing phase is discussed while the double support phase is considered to be instantaneous and the impact of the swing leg with the ground is modeled as rigid body contact. In order to formulate the sliding control law, we define four first-order sliding surfaces, based on the number of actuators, as a linear combination of tracking joint positions and velocities. The control approach is shown to guarantee that all trajectories will reach and stay on these surfaces. The surface parameters are then selected to ensure the stability of the surfaces leading to an asymptotically stable control law. Numerical simulation is presented for tracking a multi-step walk of a biped robot.

Original languageEnglish (US)
Title of host publicationProceedings of the ASME Dynamic Systems and Control Division 2005
Number of pages7
Edition2 PART B
StatePublished - Dec 1 2005
Externally publishedYes
Event2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005 - Orlando, FL, United States
Duration: Nov 5 2005Nov 11 2005

Publication series

NameAmerican Society of Mechanical Engineers, Dynamic Systems and Control Division (Publication) DSC
Number2 PART B
Volume74 DSC


Other2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005
Country/TerritoryUnited States
CityOrlando, FL

ASJC Scopus subject areas

  • Mechanical Engineering
  • Software


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