Thomas D. Gillespie, Ph.D.Research Professor Emeritus, The University of Michigan

Director of Product Planning, Mechanical Simulation Corporation

ISTVS 8th Americas Conference

Simulation Applications in Mobility

Research

Simulation Questions

� In what areas can truck simulation tools help us

understand the mechanics affecting on/off-road mobility?

� Do Performance Based Standards being developed for

on-highway trucks point the way for designing better

off/on-road vehicles?

� What are some of the new technologies for powertrain

control being developed by the automotive industries

that could potentially improve mobility of off/on-road

vehicles?

3

Engineering plotter

Surface animator

Vehicle math model solversGraphical database

What Is Simulation?• Computes time-based vehicle motion

• High fidelity models

• All in one, turn key program

• Multiple examples

• Built-in animation

• Built-in plotter

• Runs in real time

Areas where simulation help us understand the mechanics affecting on/off-road mobility?

� Simulation creates a virtual vehicle for testing:

� Mobility/tractive performance – propulsion and braking

� Turning behavior – agility and maneuverability

� Rollover – static and dynamic

� Ride – crew comfort and fatigue

Examples of Mobility Simulation

Severe Bump Test Course

Rollover Threshold

Tire Forces when Maneuvering

Do Performance Based Standards being developed for on-highway trucks point the way for designing better off/on-road vehicles?

� Gradeability and turning quantify maneuvering

performance

� Startability on grades (PBS 15% slopes)

� 10x10 gradeability on slippery terrain

� Front axle friction demand when turning multi-axle

vehicles

New technologies for powertrain control from the automotive industries

� Advanced 4WD/AWD systems

� Broad class of powertrain systems

� Differences between manufacturers, models and brands

� All controls throttle and brakes automatically to increase mobility

� Crawl control

Powertrain Example -- Ford Intelligent 4WD

Ford Intelligent 4WD Features

� Normal: Default FWD with RWD as needed

� Mud/Ruts: Aggressive throttle response, limited

upshifting and de-sensitized ESC to allow more spin

� Snow/Grass/Gravel*: More responsive upshifting

with engine torque controlled for traction

� Sand*: Tuned to allow aggressive wheel spin for

traction

� Hill Descent: Sets and maintains constant speed

during hill descent

*ABS mode changes to allow material build up in front of the tire

Toyota Multi-Terrain Select System with Crawl Control

� Regulates wheel spin by control of throttle and brake

� Crawl Control

� Set speed from 1 – 5 mph

� System controls throttle and brakes, driver only steers

Example of Off-road Simulation

� Crusher is a high-mobility autonomous vehicle

� Developed by National Robotics Engineering Center, Pittsburgh PA

� 6x6 vehicle with skid steer

� Advanced high speed model was tested using TruckSim

Ref: DARPA Project, Carnegie Mellon University

National Robotics Engineering Center

End