title: Dynamics and regulation of locomotion of a human swing leg as a double-pendulum considering self-impact joint constraint.
abstract: BACKGROUND
  Despite some successful dynamic simulation of self-impact double pendulum (SIDP)-as humanoid robots legs or arms- studies, there is limited information available about the control of one leg locomotion.
  
  
  OBJECTIVE
  The main goal of this research is to improve the reliability of the mammalians leg locomotion and building more elaborated models close to the natural movements, by modeling the swing leg as a SIDP. This paper also presents the control design for a SIDP by a nonlinear model-based control method. To achieve this goal, the available data of normal human gait will be taken as the desired trajectories of the hip and knee joints.
  
  
  METHODS
  The model is characterized by the constraint that occurs at the knee joint (the lower joint of the model) in both dynamic modeling and control design. Since the system dynamics is nonlinear, the MIMO Input-Output Feedback Linearization method will be employed for control purposes.
  
  
  RESULTS
  The first constraint in forward impact simulation happens at 0.5 rad where the speed of the upper link is increased to 2.5 rad/sec. and the speed of the lower link is reduced to -5 rad/sec. The subsequent constraints occur rather moderately. In the case of both backward and forward constraints simulation, the backward impact occurs at -0.5 rad and the speeds of the upper and lower links increase to 2.2 and 1.5 rad/sec., respectively.
  
  
  CONCLUSIONS
  The designed controller performed suitably well and regulated the system accurately.
authors.affiliation: Department of Mechanical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Y
authors.initials: Y
authors.lastname: Bazargan-Lari
authors.affiliation: School of Mechanical Engineering, Shiraz University, Shiraz, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Eghtesad
authors.affiliation: Department of Mechanical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran ; Department of Mechanical Engineering, Maleke-Ashtar University of Technology, Lavizan,Tehran, Iran.
authors.forename: A
authors.initials: A
authors.lastname: Khoogar
authors.affiliation: Department of Mechanical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: A
authors.initials: A
authors.lastname: Mohammad-Zadeh
keywords: Double pendulum; Feedback linearization; Leg locomotion; Self-impact joint constraint; Single support phase; Swing leg