title: Identification of human-generated forces on wheelchairs during total-body extensor thrusts.
abstract: BACKGROUND
  Involuntary extensor thrust experienced by wheelchair users with neurological disorders may cause injuries via impact with the wheelchair, lead to the occupant sliding out of the seat, and also damage the wheelchair. The concept of a dynamic seat, which allows movement of a seat with respect to the wheelchair frame, has been suggested as a potential solution to provide greater freedom and safety. Knowledge of the human-generated motion and forces during unconstrained extensor thrust events is of great importance in developing more comfortable and effective dynamic seats. The objective of this study was to develop a method to identify human-generated motions and forces during extensor thrust events. This information can be used to design the triggering system for a dynamic seat.
  
  
  METHODS
  An experimental system was developed to automatically track the motions of the wheelchair user using a video camera and also measure the forces at the footrest. An inverse dynamic approach was employed along with a three-link human body model and the experimental data to predict the human-generated forces.
  
  
  RESULTS
  Two kinds of experiments were performed: the first experiment validated the proposed model and the second experiment showed the effects of the extensor thrust speed, the footrest angle, and the seatback angle. The proposed method was tested using a sensitivity analysis, from which a performance index was deduced to help indicate the robust region of the force identification.
  
  
  CONCLUSIONS
  A system to determine human-generated motions and forces during unconstrained extensor thrusts was developed. Through experiments and simulations, the effectiveness and reliability of the developed system was established.
authors.affiliation: School of Mechanical Engineering, Kumoh National Institute of Technology, 1 Yangho-dong, Kumi, Kyungbuk 730-701, South Korea. swhong@kumoh.ac.kr
authors.forename: Seong-Wook
authors.initials: SW
authors.lastname: Hong
authors.forename: Vlad
authors.initials: V
authors.lastname: Patrangenaru
authors.forename: William
authors.initials: W
authors.lastname: Singhose
authors.forename: Stephen
authors.initials: S
authors.lastname: Sprigle
mesh_terms: D000054:Acceleration; D000056:Accident Prevention; D000058:Accidental Falls / Q000517:prevention & control*; D000465:Algorithms; D001696:Biomechanical Phenomena; D004867:Equipment Design; D004869:Equipment Safety; D006801:Humans; D019563:Mechanics; D008962:Models, Theoretical; D009038:Motion; D019838:Neck Injuries / Q000517:prevention & control*; D015203:Reproducibility of Results; D014910:Wheelchairs