HVE White Papers
||SIMON (SImulation MOdel Non-linear)
SIMON is a dynamic simulation of the response of one or more vehicles to driver inputs, factors related to the environment (e.g. terrain, atmosphere) and inter-vehicle collision(s). SIMON was built from the ground up employing the latest advances in software and simulation technology. SIMON uses a new, general purpose 3-D vehicle dynamics engine developed by Engineering Dynamics Corporation. The dynamics engine allows a sprung mass with six degrees of freedom and unsprung masses with up to five degrees of freedom per axle. Each vehicle model may have up to three axles (six axles for full trailers) and single or dual tires. Independent and solid axle suspension types are allowed.
SIMON was specifically designed to take advantage of the rich feature set available in the HVE simulation environment, including the HVE Brake Designer, ABS Simulation Model, Driver Model, Tire-Terrain Models, Tire Blow-out Model and the patented DyMESH 3-D Collision Model. SIMON has been validated against several well-instrumented vehicle handling studies, including combined steering and braking, severe irregular terrain traversal, rollover tests, staged crash tests and tire blow-out experiments.
If you would like to see an example of how to use SIMON, download the Tutorial from the SIMON Physics Manual. (Download time for this 1.8 MB Adobe PDF file is about 2 - 5 minutes, depending upon your connection speed.)
SIMON may be used for numerous types of simulation studies. Applications for SIMON include:
Single Vehicle Simulation - SIMON incorporates robust non-linear tire and suspension models required for vehicle handling simulation studies, such as ISO 3888 severe lane change or limit maneuvers. SIMON also includes a comprehensive drivetrain model with engine performance parameters, multi-gear transmissions and differentials.
Articulated Vehicle Simulation - SIMON can simulate the dynamics of articulated multi-vehicle trains. The model is general and allows the user to simulate virtually any vehicle/trailer configuration, including A-trains, B-trains and AB-combinations.
Collision Simulation - SIMON incorporates DyMESH® , a general-purpose, 3-D non-linear collision model for simulating vehicle-to-vehicle and vehicle-to-barrier collisions. DyMESH calculates 3-D forces and moments between the interacting meshes of each vehicle model. SIMON includes these collision forces and moments with suspension forces, aerodynamic forces and inter-vehicle connection forces to produce the total vehicle-fixed forces and moments acting on the vehicle at each timestep. The resulting body damage is visualized as the 3-D mesh geometry changes during the event.
Vehicle Design - SIMON may be used for vehicle design projects involving suspension, brake, tire and steering systems. Using SIMON, these systems may be optimized on the computer before expensive prototyping and testing begins. For example, compliance tests for braking systems, such as FMVSS 105 and FMVSS 135 can be simulated for any vehicle prior to actually fitting a prototype with a specific brake design. Parametric studies involving in-use factors, such as weight distribution changes due to occupant loading and payload location, may also be performed.
Safety Research - Safety researchers may use SIMON for reconstructing most crashes involving single or multiple vehicles. Human, vehicle and environment factors may be simulated and evaluated to assist in performing detailed crash studies. Typical human factors issues include driver inputs and speed; vehicle factors include brake system and suspension design, loading conditions, and tire properties; and environment factors include superelevation and slippery road conditions.
SIMON employs full 3-dimensional engineering models with up to 21 degrees-of-freedom per vehicle. The user assigns initial position, velocity and driver controls (steering, braking, throttle, gear selection) for each vehicle. Trailers and dollys are automatically positioned behind a tow vehicle according to connection compatibility and location. A payload and up to 9 human occupants may also be positioned in each vehicle. SIMON then predicts the motion of each vehicle’s sprung mass (X, Y, Z, roll, pitch, yaw), the motions of the unsprung masses (wheel deflections, spin velocities), suspension dynamics (spring forces and deflections, axle accelerations), tire dynamics (forces, moments and slip angles at the tire/road interface), and current brake system parameters at each wheel (air pressure, brake torque, lining temperature). Numerous other output parameters are also available. Vehicle body damage from a collision simulation is also calculated and displayed using HVE’s 3-D viewers.
An environment is optional. If supplied, the environment may be a simple flat surface or complex 3-D digital terrain map (DTM) from a total station survey. Environment models are typically built for simulation studies involving proving grounds, specific roads and crash sites. An unlimited number of friction zones may be supplied. 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 SIMON tire model queries the environment to use the current elevation, surface normal vector and friction beneath each tire. Using SIMON, a vehicle may be simulated driving on virtually any surface under any conditions, including airborne vehicles.
- Selectable from HVE's built-in database, according to Location, Sex, Age, Weight Percentile, Height Percentile (Parameters from GEBOD)
- Selectable from HVEs built-in databases, according to Type (Passenger Car, Pickup, Sport-Utility, Van, Truck, Trailer, Dolly, Fixed Barrier, Movable Barrier), Make, Model, Year and Body Style
- Tires selectable from HVEs built-in databases, according to Type (Passenger Car, Light Truck, Heavy Truck, Mobile Home), Manufacturer, Model, and Size.
- Multiple Database Sources (generic, EDVDB-3D, User and others) for both vehicles and tires
- Geometry file with 3-D coordinate and material stiffness properties
- Independent and Solid Axle Suspension types with ride rates, damping, anti-sway bars, roll center height, lateral spring spacing, jounce/rebound stops, inter-axle load transfer, roll steer, camber change and halftrack change characteristics
- Wheel locations (x, y, z coordinates)
- Steering System with steering gear and linkage parameters
- Brake System with lag/rise time, brake torque ratio and proportioning at each wheel (may be used with HVE Brake Designer)
- Drivetrain with engine power and torque vs rpm curves, transmissions with up to 12 numerical ratios, and differentials with up to 3 numerical ratios
- Inter-vehicle Connections (fifth wheel/king pin, pintle eye/hook, ball/hitch)
- All data are user editable
- Complete vehicle model specification published in SAE 950308
- Ambient Temperature and Pressure and Wind Conditions (speed and direction) for aerodynamics calculations
- Local Gravitational Constant
- 3-D Terrain Model (from DXF file or several other sources) with user-definable friction zones for tire-road interaction
- 3-D drag-and-drop positioning of humans in vehicles
- 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)
- Payloads (location, inertial parameters)
- Steer Degree of Freedom
- Vehicle Wheels (displacement, Tire Blow-out parameters, initial brake temperature and stroke)
- Accelerometers (positioning of up to 5 tri-axial accelerometers)
- Articulation Option
- DyMESH 3-D Collision Model Option
- Simulation Controls (integration time-steps, maximum simulation time, output time interval and termination conditions)
||Variable Output (time-based simulation results):
- Accelerometers (linear acceleration)
- Collision Pulse (acceleration history for use in occupant simulation)
- Connection Data (articulation angles, moments and forces at each inter-vehicle connection)
- Driver Data (throttle position, brake pedal force, master cylinder/treadle valve pressure, steering wheel angle, transmission/differential gear selection, path follower results)
- Drivetrain Data (engine speed, power and torque, transmission and differential numerical ratios)
- Tire Data (contact patch coordinates, forces, moments, radius, longitudinal slip, slip angle, skid status, terrain properties at the contact patch)
- Vehicle Kinematics (position, velocity, acceleration)
- Vehicle Kinetics (summation of aerodynamic, suspension, connection and collision forces and moments acting on CG of sprung mass of each vehicle)
- Wheel Data (coordinates, steer angle, spin velocity, suspension force and deflection, drive and brake torque, wheel cylinder/air chamber pressure)
- 3-D Visualization of vehicle motion at user-specified time intervals
- 3-D Damage Profile Viewer at user-specified time intervals
- Accident History (initial and final positions and velocities)
- Driver Controls (steering, braking, throttle, gear selection, path follower parameters)
- Environment Data (air temperature, pressure and density; wind speed and direction; gravity constant, name and information about environment geometry file)
- Event Data (payload information, accelerometer information, wheel data, Tire Blow-out information)
- Human Data (seat position, pelvis CG coordinates relative to vehicle CG, weight)
- Messages (event-related diagnostics)
- Program Data (version, simulation controls, calculation options)
- Vehicle Data (dimensions, inertias, suspension properties, steering system properties, brake system properties at master cylinder/treadle valve and wheels, HVE Brake Designer parameters, tire properties)