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  EDVSM

Name EDVSM (Engineering Dynamics Vehicle Simulation Model)
Description
EDVSM is an HVE-compatible 3-D simulation of the dynamic response of a motor vehicle to driver inputs and 3-D road conditions. Based on the HVOSM-VD2 model developed at Calspan, EDVSM incorporates numerous enhancements developed by EDC, including a powerful tire-terrain interaction model and Tire Blow-out Model™. The Tire Blow-out Model is a sophisticated 3-dimensional analysis of a vehicle's transient response to a gradual or sudden air loss in one or more tires. Using EDVSM, a vehicle may be simulated driving on virtually any surface under any conditions, including airborne vehicles and complete rollover.

The user enters initial position, velocity and driver controls (steering, braking, throttle and gear selection). The program calculates 3-D vehicle kinematics (position, velocity, acceleration vs time), tire forces and moments, suspension forces and deflections, and drive and brake system torques. Vehicle body damage from a rollover is also calculated and displayed using HVE's 3-D viewers.

EDVSM can be used by design engineers and safety researchers to predict and visualize vehicle handling response, especially for limit maneuvers resulting in loss of control or rollover. EDVSM has been validated against several well-instrumented vehicle handling studies, including combined steering and braking, severe irregular terrain traversal, roll over tests involving curbs and soft soil, and tire blow-out experiments.

EDVSM employs a fully 3-dimensional, 15 degree-of-freedom vehicle model. The program supports 2-axled vehicles with independent and solid axle suspension types. The analysis includes six degrees-of-freedom for the sprung mass (body x, y, z, roll, pitch, yaw), two degrees-of-freedom for each unsprung mass (wheel spin and deflection) and one degree-of-freedom for the steering system.

Tire vs terrain interaction is modeled transparently to the user. This powerful capability allows the user to create a detailed, 3-D environment (using HVE's 3-D Editor or any popular modeling package), then drive a vehicle on it. At each timestep, the EDVSM tire model queries the environment to use the current elevation, surface normal vector and friction beneath each tire.

Vehicle body vs terrain interaction is also modeled transparently by calculating the force between the vehicle 3-D mesh and the terrain mesh. This capability allows for the simulation of complete rollover involving multiple contacts between the body and the terrain. The resulting body damage is also visualized as the 3-D mesh geometry changes during the event.

EDVSM includes four powerful capabilities described below:

HVE Brake Designer
EDVSM supports the HVE Brake Designer. This key technology allows users to design and test brake systems all within the HVE simulation environment. For more information, see SAE 2000-01-1294 - "Integrating Design and Virtual Test Environments for Brake Component Design and Material Selection" and SAE 2000-01-0126 - "Vehicle Design Evaluation Using the Digital Proving Ground".

Sprung Mass vs. Terrain Contact
EDVSM now includes a newly developed technology that allows users to study complete vehicle rollover, including contact between the vehicle body and terrain. For more information, see SAE 2000-01-0852 - "Applications and Limitations of 3-Dimensional Vehicle Rollover Simulation".

HVE Driver Model
EDVSM now includes a new closed-loop driver model, allowing users to define an attempted maneuver and have the simulation determine the required steering inputs. Typical examples include single and double lane-change maneuvers. The HVE Driver Model may also be used to study the effects of driver fatigue and intoxication. For more information, see SAE 2000-01-1313 - "The Simulation of Driver Inputs using a Vehicle Driver Model".

Steer Degree of Freedom
EDVSM now allows steering inputs from forces and moments produced at the tire-road interface. This model, called the Steer Degree of Freedom, allows users to study how hands-off steering affects vehicle trajectory. An obvious application is post-collision motion of a vehicle. The model is described in detail in the latest revision of the EDVSM User’s Manual, Chapter 4 - Calculation Methods.

If you would like to see an example of how to use EDVSM, download the Tutorial from the EDVSM Physics Manual. (Download time for this 0.8 MB Adobe PDF file is about 1 - 3 minutes, depending upon your connection speed.)


Input Vehicle
  • Selectable from HVE's built-in databases, according to Type (Passenger Car, Pickup, Sport-Utility, Van, Truck), Make, Model, Year, Body Style
  • Tires selectable from HVE's built-in databases, according to Type (Passenger Car, Light Truck, Heavy Truck, Mobile Home), Manufacturer, Model and Size
  • Several Database Sources (Generic, EDVDB-3D, User and others) for both vehicles and tire
  • Geometry file with 3-D coordinate and material stiffness properties
  • Independent and Solid Axle suspension types with ride rates, damping, anti-sway bars, jounce/rebound stops, roll steer, anti-pitch, camber change and halftrack change characteristics
  • Brake system with proportioning at each wheel
  • Steering system with friction, left/right steering stops and steer inertia parameters
  • All data are user-editable
  • Complete vehicle model specification published in SAE 950308

Environment
  • Wind Speed and Direction for aerodynamics calculations
  • Ambient Temperature and Pressure for aerodynamics calculations
  • 3-D Terrain Model (from DXF file or several other sources) with user-definable friction zones for tire-road interaction
  • Local Gravitational Constant

Event
  • 3-D drag-and-drop positioning of vehicles in the environment
  • Open-loop driver control tables (steering, braking, throttle, gear selection)
  • Closed-loop Driver Model (Path, Driver characteristics, neuro-muscular filter)
  • Simulation Controls (integration timesteps, maximum simulation time and output time interval)
  • Tire Blow-out Parameters (blow-out time and duration, tire stiffness and rolling resistance multipliers)
Output Variable Output
  • Vehicle Kinematics (position, velocity, acceleration vs time)
  • Tire Data (contact patch coordinates, forces, moments, radius, longitudinal slip, slip angle, skid status vs time)
  • Wheel Data (coordinates, steer angle, spin velocity, suspension force and deflection, drive and brake torque, wheel cylinder pressure vs time)
  • Drivetrain Data (engine speed, power and torque, transmission and differential ratios vs time)
  • Driver Data (throttle position, brake pedal force, master cylinder pressure, steering wheel angle, transmission gear selection, path follower results vs time)
  • Collision Pulse (acceleration vs time history for occupant simulation)

Trajectory Simulation
  • 3-D visualization of vehicle motion at user-specified time intervals
  • 3-D Damage Profile Viewer

Reports

  • Accident History (initial and final positions and velocities)
  • Driver Controls (steering, braking, throttle, gear selection, path follower parameters)
  • Simulation Controls (numerical integration parameters)
  • Vehicle Data (dimensions, inertias, suspension properties, steering system properties, brake system properties at master cylinder and wheels, tire properties)
  • Messages (event-related diagnostics)

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