HVE Features Overview
HVE offers an extensive feature set available to use in several HVE-compatible simulation models. These features allow for advanced simulation of vehicle control systems, driver inputs, tire failures and 3-D collision modeling. A brief overview of each feature is presented below, with links to more details available within this website:
|HVE ABS Simulation Model (Available in SIMON™)
The HVE ABS Simulation model is a general purpose model, available for use in the SIMON vehicle simulation model. The model is applicable to the design of ABS systems, as well as the study of loss-of-control crashes of ABS-equipped vehicles. The HVE ABS model works like the ABS system on an actual vehicle: It uses an algorithm to modulate the brake pressure at each wheel. The algorithm is designed to maximize brake force and prevent excessive wheel slip.
Two ABS algorithms are currently implemented in the HVE simulation environment. These are the Tire Slip algorithm and the HVE Bosch Version 1 algorithm. Tire Slip - This is a simple and straight-forward ABS algorithm. Its design is based on the fundamental goal of an ABS system, which is to maintain tire slip in the vicinity of peak friction coefficient. It is generally applicable to any type of vehicle (passenger car, truck, etc). HVE Bosch Version 1 Algorithm - The HVE Bosch Version 1 ABS algorithm is based on the information provided in Bosch technical literature. The algorithm is based on wheel spin acceleration and a critical tire slip threshold. The Bosch ABS system is used on many US and foreign passenger cars.
To further enhance the results from an ABS simulation, HVE now includes a new method for displaying tire marks. In the new method, the opacity of a tire mark is varied according to the current vertical tire load (heavier tire loads produce darker marks), the percentage of longitudinal tire slip and the percentage of lateral tire slip (increased slip produces darker marks). In addition, a set of weighting coefficients determines the opacity of tire marks during combined braking and steering. Since the vast majority of vehicles are now fitted with ABS, the new HVE ABS model is an important new feature, especially for simulating pre-impact braking and loss of control.
More detailed information about the HVE ABS Simulation Model is available in SAE 2002-01-0559, "A Simulation Model for Vehicle Braking Systems Fitted with ABS" and in SAE 2010-01-0070, "Verification of ABS Models Applied in Programs for Road Accident Simulation".
|HVE Brake Designer (Available in SIMON™, EDVSM™ and EDVDS™)
The Brake Designer™ is a time-domain simulation model of user-defined brake system components. The purpose of the HVE Brake Designer is to provide a detailed brake design capability integrated directly within the HVE simulation environment. Engineers can reduce costs by performing simulated compliance tests of complete vehicles on a digital proving ground prior to expensive prototyping and proving ground testing. Examples include steering and braking on high-friction, low-friction and split-mu surfaces at different speeds and loading conditions. In addition, alternative brake designs can quickly be evaluated.
The HVE Brake Designer model incorporates advanced features, such as the effect of sliding speed and temperature on lining friction. The model also includes the capability to study brake fade characteristics, such as that which occurs to trucks on long downhill grades. Parameters defining physical, performance and material properties of brake components are fully user-editable.
Values for brake factor, actuation factor and brake torque ratio are calculated by the HVE Brake Designer. Initial values are based on the environment's ambient temperature and zero sliding velocity at the pad/rotor (or drum/lining) interface. During a vehicle dynamic simulation, the appropriate brake factor and brake torque ratio are based on the current brake internal temperature and sliding velocity calculated by the simulation. Outputs from HVE-compatible vehicle dynamics simulation models using the HVE Brake Designer include brake torque, brake stroke, brake pressure, brake piston force, drum/rotor temperature and lining temperature.
More detailed information about the HVE Brake Designer is available in SAE 2000-01-1294, "Integrating Design and Virtual Test Environments for Brake Component Design and Material Selection".
|HVE Driver Model, Path Follower (Available in SIMON™, EDVSM™, EDVDS™and EDSMAC4™)
The HVE Driver Model is a closed-loop driver model, allowing users to define an attempted maneuver and have the simulation determine the required steering inputs to make the vehicle follow the defined path. 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.
The HVE Driver Model has four components: Path Generator, General Parameters, Driver Descriptors, Driver Neuro-Muscular Filter. The path generator uses up to eight 3-D positions and orientations to define the attempted path. The path is constructed from a 3-D spline curve passing through each user-specified location and tangent to the roll, pitch and yaw orientations for each location. The general parameters provide control over the Driver Model algorithm. Control parameters include driver starting time, driver sample interval, driver preview distance, allowable path error, and initial steering wheel angle. The driver descriptors describe how the operator attempts to control the vehicle. These parameters include the driver preview distance (the point ahead of the vehicle where the driver is actually looking and presumably wants to go), driver comfort level (lateral acceleration), maximum steering wheel velocity, steer correction rate and steer correction damping. The driver neuro-muscular filter represents a mathematical model of the human operator in man-machine performance. The model used in HVE was derived from the model described by McRuer, et al (1965) as published in the NASA Bioastronautics Databook (NASA SP-3006). The model includes an effective time delay representing the time required to read, interpret and decide upon the appropriate control motion, the lead time representing a ratio of the weight the driver attributes to the displayed velocity compared to the displayed position, and the time lag representing the amount of data smoothing the driver applies to his external stimuli. These parameters correspond to the first-order effects of the neurological and muscular systems of a human driver.
More detailed information about the HVE Driver Model is available in SAE 2000-01-1313, "The Simulation of Driver Inputs Using a Vehicle Driver Model".
|HVE Driver Model, Speed Follower (Available in SIMON™)
SIMON users can take advantage of this enhancement to the HVE Driver Model. When assigning target positions for the Path Follower, simply assign a Total Velocity at each position in order to use the Speed Follower. SIMON will then determine the throttle and/or brake applications required to maintain the desired speed. The speed, just like the path, is determined using interpolation between target positions and velocities. The parameters that control the Speed Follower are found on the Speed tab in the HVE Driver Controls dialog. The main control parameters that define how quickly the pedals are applied and released are the Throttle and Brake Correction Rates.
|HVE Steer Degree of Freedom Model (Available in SIMON™and EDVSM™)
The HVE Steer Degree of Freedom Model allows users to study how hands-off steering affects vehicle trajectory. The steering linkage of the vehicle is assumed to be rigid, thus the angular acceleration about the steering axis is the same for right-side and left-side wheels. External steer forces are generated at the tire-road interface, thus producing a moment about each tire's steering axis according to the tire's pneumatic trail. The moments are resisted by steer system inertia and internal coulomb friction. Steering is limited by right and left steering stops at each wheel. Based upon these conditions, the steering inputs used in the simulation are calculated from the interaction of the vehicle's tires traveling over and interacting with the 3-D terrain model defined by the user. An obvious application of the Steer Degree of Freedom Model is the post-collision motion of a vehicle.
|HVE Tire Blow-out Model (Available in SIMON™, EDVSM™and EDSMAC4™)
The output from the HVE Tire Blow-out Model provides detailed information regarding the transient nature of a vehicle's response to a tire blow-out that occurs during any maneuver. Dynamic changes in tire forces and moments are calculated and displayed, giving researchers the capability to simulate and predict the outcome for one or more driving scenarios, and to study how these transient forces affect vehicle handling.
To study transient effects, the HVE Tire Blow-out Model operates in the time domain (i.e., the dependent parameters are varied according to time). By far, the greatest effect of reduced inflation is on cornering stiffness, camber stiffness, radial tire stiffness and rolling resistance. Therefore, these parameters were made the dependent parameters in the blow-out model. The dependent parameters are varied using linear interpolation, starting at the initiation time and lasting over the blow-out duration. The dependent parameters are multiplied (stiffness values) and divided (rolling resistance) by user-entered blow-out factors to create the blown tire properties.
More detailed information about the HVE Tire Blow-out Model is available in SAE 980221, "3-Dimensional Simulation of Vehicle Response to Tire Blow-outs".
|Enhanced Tire-Terrain Models (Available in SIMON™)
The Radial Spring Model allows for simulating tires mounting curbs and rolling over potholes. The Sidewall Impact Model allows for a rigorous modeling of the force applied to the sidewall of a tire such as occurs in a curb-tripped rollover. The Soft Soil Model allows for calculating tire drag for a vehicle that has left the roadway and is traveling through soft dirt. Details about the tire-terrain models were presented in the Technical Session of the Winter 2005 EDC Technical Newsletter and also in HVE Forum White Paper WP2005-6 "Simulation of Tire Interaction with Curbs and Irregular Terrain."
|HVE Automatic Transmission Model (Available in SIMON™)
The HVE Automatic Transmission Model in shifts the vehicle's transmission automatically during a simulation, based upon engine speed and throttle position, just like a real transmission. Entering a shift table manually is no longer required, resulting in improved simulations in less time. The HVE Automatic Transmission Model is especially useful whenever the vehicle's powertrain capabilities and driver control inputs are an issue.
The Transmission dialog not only displays the gear ratios of the transmission, but also a Type selector for Manual or Automatic. If you select Automatic, SIMON automatically determines the correct gear at the start of your simulation according to the user-entered Initial Velocity, then shifts the transmission accordingly. In general, shifting is controlled according to engine speed and throttle position, exactly like a real automatic transmission. More details regarding the HVE Automatic Transmission model are included in the Technical Session of the Summer 2009 EDC Technical Newsletter.
A scenario demonstrating the application of the HVE Automatic Transmission Model is available in the Passing Maneuver example in the Featured Capabilities page of this website.
|HVE Hydroplaning Model (Available in SIMON™& EDSMAC4™ )
A hydroplaning model has been integrated into the vehicle dynamics model within HVE so the effect on vehicle handling behavior may be directly observed! The HVE Hydroplaning Model calculates the reduction in tire-roadway friction at each tire contact patch as the vehicle drives through wet pavement or standing water. SIMON and EDSMAC4 users can include the effects of hydroplaning on vehicle handling directly in their simulations.
The HVE Hydroplaning Model uses three components within HVE: the Vehicle Editor provides tire pressure, tread width and tread depth for each tire; the Environment Editor provides the water surface and depth, as well as pavement microtexture and hydroplaning (reduced) friction multiplier; the Event Editor's Calculation Options dialog allows the user to select from several available hydroplaning models to be used during the simulation. The Technical Session of the Fall 2009 EDC Technical newsletter provides an overview describing how to use this exciting new capability in both EDSMAC4 and SIMON simulations.
A scenario demonstrating the application of the HVE Hydroplaning Model is available in the Hydroplaning example in the Featured Capabilities page of this website.
|HVE Electronic Stability Systems Model (Available in SIMON™)
The HVE Electronic Stability Systems (ESS) model provides crash reconstructionists the ability to simulate motor vehicle crashes involving loss-of-control due to poor driving conditions or driver overreaction during an emergency.
Most modern vehicles have two types of electronic stability control systems. A Traction Control System (TCS) helps to maintain traction at each wheel by reducing drive torque for drive wheels that are spinning, and rerouting that drive torque to wheels that are not. A Yaw Stability Control system (YSC) helps to maintain vehicle directional control during a steering maneuver by applying or reducing drive torque and/or brake pressure to individual wheels to reduce the current yaw moment. The HVE ESS model includes both a TCS model and a YSC model, providing exceptional fidelity for predicting real-world behavior of modern vehicles.
Whether the vehicles involved in your crash have Vehicle Stability Assist (VSA), Vehicle Dynamic Control (VDC), Electronic Stability Program (ESP) or other branded electronic stability control safety features, the HVE ESS model will allow you to perform detailed investigations of loss-of-control and related issues. The Technical Session of the Spring 2011 EDC Technical Newsletter focuses on the inner workings of the HVE ESS model and provides an application of the model for a high-speed cornering and braking maneuver using SIMON.
A scenario demonstrating the application of the HVE ESS Model is available in the Stability Control example in the Featured Capabilities page of this website.