Physics-based sit-to-stand three-dimensional motion prediction considering seat pan contact

James Yang, Burak Ozsoy

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review


Sit-to-stand (STS) is one of the most demanding tasks in mechanical terms in daily lives. Many elderlies, people with lower limb injuries, and patients with neurological disorders or musculoskeletal abnormalities have difficulties during this task. In literature, most studies were carried out through experiments. Experiment-based methods are time-consuming and tedious. In addition, seat pan contact forces were ignored or analyses started after lift-off instance. In this study, a three-dimensional physics-based formulation for the entire STS motion was presented. This formulation was based on joint space, where resultant joint torques instead of activations of individual muscles are considered to reduce computational time. Both ground reaction forces and the seat pan contact forces were considered, and resultant joint torques were predicted with recursive Lagrangian dynamics. A 56 degree-of-freedom (DOF) digital human model was used, and time and chair height were altered to study cause and effect. First, bilateral symmetry was assumed, and results were compared with the experimental results in literature to validate the proposed formulation. As time and chair height increased, the motion became less demanding in mechanical terms. After 2.5 s, resultant peak joint torques at the knee and ankle joints were found to be relatively equivalent to static torque components. An asymmetric STS motion example was also investigated.

Original languageEnglish
Title of host publicationDHM and Posturography
Number of pages17
ISBN (Electronic)9780128167137
StatePublished - Jan 1 2019


  • Asymmetry
  • Joint space
  • Physics-based formulation
  • Seat pan contact
  • Sit-to-Stand


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