EDVSM (Engineering Dynamics Vehicle Simulation Model)
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 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 includes a 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 includes a 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 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.