Ford Motor Company Research & Advanced Engineering Physical Fidelity and Driving Simulation 21 things to know about your simulator before you write the proposal Jeff Greenberg

Ford Motor Company Research & Advanced Engineering fidelity n 1: accuracy with which an electronic system reproduces the sound or image of its input signal 2: the quality of being faithful [syn: faithfulness] [ant: infidelity,infidelity]faithfulnessinfidelity SourceSource: WordNet ® 1.6, © 1997 Princeton University

Ford Motor Company Research & Advanced Engineering How much is enough? ●Depends on the experimental details, of course! ●Simulator experiments generally seek to measure a human response across a variety of controlled conditions ●The goal is often to extrapolate those findings from the simulator to the traffic system at large: real people, real cars, real roads.

Ford Motor Company Research & Advanced Engineering Fidelity Spectrum ●Real People, Real Cars, Real Roads Epidemiology (Truth Yesterday) ●Sampled People, Real Cars, Real Roads Black box observation, naturalistic data collection (Truth Today?) ●Sampled People, Fake Cars, Real Roads Prototype studies, Field Studies (Truth Tomorrow??) ●Sampled People, Virtual Cars, Virtual Roads Driving Simulation (Truth Today, Tomorrow and Beyond ???) FIDELITY higher lower

Ford Motor Company Research & Advanced Engineering Infidelity or Artifacts are key ●All simulators have artifacts ●The goal of characterizing a simulator’s fidelity is to know what your major artifacts are and how big they are in the context of a given experimental setup. ●The key to experimental success is understanding how those artifacts interact with your experimental design

Ford Motor Company Research & Advanced Engineering The Art of Simulator Triage No matter how compelling the research interest, a simulator study should only be done if you understand the artifacts that are likely to occur in your simulator during the experiment and have the ability to control them to an acceptable level. In practice, most patients cannot be saved – i.e. most research questions cannot be answered in a given simulator with a useful level of accuracy.

Ford Motor Company Research & Advanced Engineering How do I know what artifacts to expect? ●Start with a knowledge of the most important characteristics of physical fidelity in your simulator ●Cueing systems Visual Auditory Haptic or Tactile Vestibular ●Physical environment Cab Laboratory ●Virtual environment Visual world Terrain and roadways Vehicle Models

Ford Motor Company Research & Advanced Engineering Visual System CharacteristicKey MeasureMost Likely Artifacts 1Horiz. Field of View Angular extentToo Small: not enough visual information to see or drive scenario. Improper mirror scanning behavior and visual allocation. Too Large: potential simulator sickness 2Perceived resolution Angular extent of the smallest resolvable optical line pair Too Small: Improper threat identification. Difficulty seeing roadway and signage. Eyestrain & fatigue, simulator sickness. 3Transport delay Time delay between operator action and visual system response Too large: Degraded vehicle control. Increased simulator sickness. 4Accommodation Distance at which eye accommodates Too Small: eyestrain, poor depth perception and distance judgements, simulator sickness?

Ford Motor Company Research & Advanced Engineering Auditory System CharacteristicKey MeasureMost Likely Artifacts 5Wind/Tire noise loudness Loudness as a function of speed Too Small: Underestimation of vehicle speed Too Large: Discomfort 6Powertrain loudness Loudness as a function of engine speed and load Too Small: Poor onset acceleration cue

Ford Motor Company Research & Advanced Engineering Haptic Systems CharacteristicKey MeasureMost Likely Artifacts 7Steering loader torque Torque as a function of vehicle speed and sw angle Too Small: poor vehicle control Too Large: difficulty steering, potential safety concern 8Steering loader damping Free response to small step input Too Small: instability, potential safety issue Too Large: steering feels ‘dead’, poor steering control during lane changes 9Brake pedal stiffness Force per unit distance Too Small: low initial braking forces Too Large: high initial braking forces, can’t modulate brake pedal, increased simulator sickness

Ford Motor Company Research & Advanced Engineering Vestibular Cueing CharacteristicKey MeasureMost Likely Artifacts 10Useful motion range (<3Hz) Maximum useful acceleration scale factor per degree of freedom Too Small: poor vehicle control, simulator sickness, visual demand too high 11Small Signal bandwidth 3dB frequency 90deg phase Too Small: incorrect ride dynamics, poor road feel, ‘magic carpet’ ride 12Roughness Acceleration noise (g’s) Too Large: false cues, poor on-center control, discomfort, anxiety

Ford Motor Company Research & Advanced Engineering Environment: Cab & Laboratory CharacteristicKey MeasureMost Likely Artifacts 13Realistic greenhouse A-pillar geometryNo A-pillars: incorrect FOV, changed visual scanning 14Visual Immersion Number of objects fixed in laboratory frame that are visible while driving Too Large: destroys perception of self-motion in fixed sim, in moving sim generates false motion cues

Ford Motor Company Research & Advanced Engineering Visual World CharacteristicKey MeasureMost Likely Artifacts 15Maximum traffic density Number of cars in scene without frame overruns Too Low: may not meet experimental objectives. Adding traffic and tolerating overruns may invalidate vehicle control measures and increase simulator sickness! 16Clarity of road markings Distance at which road markings are clearly visible Too Small: Drivers may be unable to determine correct vehicle path

Ford Motor Company Research & Advanced Engineering Terrain & Roadways CharacteristicKey MeasureMost Likely Artifacts 17Offroad capability Can driving occur anywhere in the world or only on ‘roads’? ‘Road’ only: agricultural and off-road simulations not possible 18Terrain fidelity Spatial frequency of the terrain geometry Too Small: Vehicle motions unusually rough over terrain that appears to be smooth. When coupled with vibration or motion simulation can induce discomfort.

Ford Motor Company Research & Advanced Engineering Vehicle Models CharacteristicKey MeasureMost Likely Artifacts 19Acceleration 0-60 time (s)Too High or too low: Unrealistic following abilities and gap acceptance. 20Engine braking/Aero drag Decleration at closed throttle as a function of vehicle speed Too High: Unrealistic car following Too Low: Unrealistic car following, overuse of brakes to maintain speed 21Lateral acceleration gain Ay/Swa as a function of vehicle speed Too Low: Incorrect lane keeping, poor lane change ability Too High: Incorrect lane keep, unrealistic lane change ability, potentially unstable