Use of walking simulations to assess the frictional requirements of slip resistant gait.
Mahboobin-A; Cham-R; Piazza-S
Proceedings of the 2010 International Conference on Fall Prevention and Protection May 19-20, 2010, Morgantown, WV. Morgantown, WV: National Institute for Occupational Safety and Health, 2010 May; :45
Falls account for more than 20% of fatal injuries in workers over the age of 65 years old, and are often initiated by slips. Experimental studies have been useful to identify biomechanical variables that may impact slipping severity, but to determine the causes of failed recovery attempts from experiments alone is a challenging endeavor. Modeling and simulation techniques can complement experimental approaches to identify both the causes of falling and fall recovery strategies. The purpose of this study was to demonstrate the feasibility of using simulations to determine the subject-specific peak required coefficient of friction (RCOF) and to assess a slip simulation utilizing this parameter. This was achieved by using a model that included foot-floor interaction to find the set of moments that best tracked the joint angles and measured ground reaction forces obtained from a dry trial. A slip simulation was then generated by driving the model with moments obtained from the dry condition and by reducing the foot-floor friction coefficient (mu). The peak RCOFs obtained through simulations were very similar to their experimental counterpart. There was also an agreement between the simulation peak RCOF and the mu value obtained for each subject, under which the resulting body kinematics were substantially different from the dry gait patterns. This correspondence supports the validity of our simulation results. In addition, the slip simulation findings imply the need for early and appropriate active corrective responses to prevent a fall, especially in slippery environments with mu values less than the peak RCOF. Objectives: The purpose of this study was to demonstrate the feasibility of using forward dynamic simulations to determine subject-specific peak RCOF values. These simulations were used to determine the mu value under which body kinematics will diverge from normal gait. The potential findings of this work could be used to (i) reduce the risk of slips and falls, (ii) may provide insights into the impact of active corrective moments needed to prevent a fall, and (iii) may have important implications in safety-related research, specifically in the design of slip-resistant shoe and flooring environments. Methods: A walking model incorporating foot-floor interaction, modeled using an array of damped springs with friction under the foot, was utilized to find, using parameter optimization, the set of moments that best tracked the joint rotations and ground reaction forces obtained from a dry trial. Normal gait was simulated from the leading leg heel contact (0 ms) to 190 ms after. Slip was simulated by reducing the frictional forces applied to the leading foot (i.e., by reducing mu). The applied joint-moments remained the same as in the dry gait simulation. Results: The optimization of dry walking resulted in joint moments that reproduced main features of the experimentally collected data. The experimental and simulated peak RCOF patterns were very similar. Applying the required joint moments needed in dry walking in the slip simulations with values of greater than or equal to peak
Accident-potential; Accident-prevention; Accidents; Accident-statistics; Ergonomics; Injuries; Injury-prevention; Models; Posture; Qualitative-analysis; Risk-analysis; Risk-factors; Statistical-analysis; Surface-properties
Arash Mahboobin, University of Pittsburgh, Pittsburgh, PA, 15261, USA
Proceedings of the 2010 International Conference on Fall Prevention and Protection May 18-20, 2010, Morgantown, WV
University of Pittsburgh