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Chapter 4 — Calculation Method

In the original Fifth Edition manual this chapter was marked (Reserved For Future Use).

NOTE: See Reference 2 (Robbins, Bennett & Bowman, User-Oriented Mathematical Crash Victim Simulator, HSRI, University of Michigan) for the underlying calculation method — see Chapter 7 — References.

Summary of the method (from the current source code)

The following overview is derived from the current EDHIS physics source (Physics/Source/Edhis/), consistent with the model description in Chapters 1 and 2:

  • Human model — A 3-mass (Head, Torso, Legs), 2-joint (Neck, Hip) rigid-body model with 12 degrees of freedom, derived from the HSRI-3D crash victim simulator. HVE's 15-segment human is condensed into the three EDHIS segments using the parallel axis theorem (Hisinput.cpp).
  • Contact forces — Human segment ellipsoids are tested against vehicle planar contact surfaces each timestep; penetration produces a force from the linear/quadratic/cubic stiffness, damping, edge-constant and unloading-slope properties (Contact.cpp, Fct.cpp).
  • Joints — Ball-and-socket joint torques are computed from linear elastic, damping and joint-stop elasticity properties (Joint.cpp).
  • Vehicle motion — The vehicle is not dynamically simulated; its accelerations are interpolated from the user-supplied 6-DOF collision pulse and integrated for velocity and position (Vehaccel.cpp).
  • Numerical integration — The equations of motion are integrated using a starter method (Euler, Runge-Kutta-Ralston "Modified Runge-Kutta" — the default — or classical Runge-Kutta) followed by a predictor-corrector method (Adams-Moulton or Milne-Hamming — the default), with timestep bisection to achieve velocity convergence (Rk.cpp, Drkgs.cpp, Hismain.cpp). See Calculation Options for EDHIS for the user-selectable options and their internal variables.
  • Injury measures — HIC, Chest Severity Index, chest force/acceleration, head pitch concussion, head side acceleration, femur load, joint over-rotation and belt loads are accumulated during the run and compared against the human's injury tolerances (Output.cpp, Accel.cpp).

Previous: Chapter 3 — Program Output | Next: Chapter 5 — EDHIS Tutorial

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