.. _auto_curve_vpi:

*COMPUTE THE PULSE INDEX BASED ON VEHICLE DISPLACEMENT AND ACCELERATION TIME-HISTORY DATA*
==========================================================================================

Computes the Vehicle Pulse Index (VPI) from vehicle displacement and acceleration time-history curves, using a single-degree-of-freedom model parameterized by slack, stiffness, and mass. Use this worker to quantify crash pulse severity and structural aggressiveness for occupant safety assessments.

When to use
-----------

Classification: **process**.

Tagged: ``acceleration``, ``crash_pulse``, ``displacement``, ``occupant_safety``, ``pulse_severity``, ``time_history``, ``vehicle_pulse_index``, ``vpi``.

Inputs
------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20 20 20

   * - Label
     - ID
     - Type
     - Default
     - Required
     - Description
   * - Vehicle Displacement
     - vehicle_displacement
     - vector
     - —
     - 
     - Vehicle displacement time-history curve (time vs. displacement, typically in mm or inches); used as the primary kinematic input to the VPI SDOF model.
   * - Vehicle Acceleration
     - vehicle_acceleration
     - vector
     - —
     - 
     - Vehicle acceleration time-history curve (time vs. acceleration, typically in g or mm/ms²); paired with displacement to drive the VPI calculation.
   * - Slack
     - slack
     - scalar
     - 1
     - 
     - Slack (free travel) of the SDOF surrogate occupant model in displacement units (default = 1); represents the gap before contact force is engaged.
   * - Stiffness
     - stiffness
     - scalar
     - 1
     - 
     - Stiffness of the SDOF surrogate occupant spring in force-per-displacement units (default = 1); controls the restraint load in the VPI model.
   * - Mass
     - mass
     - scalar
     - 1
     - 
     - Mass of the surrogate occupant in the SDOF model in mass units (default = 1); scales the inertial force contribution to the pulse index.

Outputs
-------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20

   * - Label
     - ID
     - Type
     - Description
   * - curve_vpi_output_1
     - curve_vpi_output_1
     - scalar
     - Scalar Vehicle Pulse Index (VPI) value computed from the supplied displacement and acceleration curves and SDOF parameters; higher values indicate a more aggressive crash pulse.

Disciplines
-----------

- data.curve.pair
- engineering.crash.dynamics
- engineering.crash.occupant_safety

Runnable example
----------------

A runnable example is registered for this worker. Open the example workflow on the d3VIEW canvas: `/api/workflow/example?id=curve_vpi <https://www.d3view.com/api/workflow/example?id=curve_vpi>`_

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   Auto-generated from <code>transformation</code> schema. Worker id: <code>curve_vpi</code>. Schema hash: <code>5eae8d01d864</code>. Hand-curated docs in <code>workerexamples/</code> override this page when present.
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