SimCreator supports high performance
solutions. Typically, the driving simulator
software iterates at 60 Hz update rate to support
more data resolution for visuals subsystem update
rate, high-resolution terrain query, and rapid
system response. Driving simulators in a
host/visual channel configuration built with RTI's
SimCreator technology have shown less than 50 ms
measured latency from step input on the host to
vehicle dynamics are the cornerstone of any high performance driving
simulation platform. RTI's
SimVehicleLT product controls our simulation vehicle dynamics.
SimVehicleLT can be configured to represent a variety of wheeled vehicles
through selectable input data files.
SimVehicleLT is made up of models of the four corners of
the vehicle that are coupled with a 6DOF Body component. A
powertrain model calculates the torques at the wheels based on brake
pedal, gear, and accelerator pedal inputs. Each vehicle corner
component takes into account spring and damping rates, bump stops,
anti-sway bars, anti-squat anti-dive geometry and roll axis height.
The unsprung mass is modeled as a separate body connected by a prismatic
joint to the base body. In addition, we use a Magic Formula tire model
to predict the tire forces at each wheel.
The powertrain model contains complete engine, transfer
case, differential, and torque converter models. The engine model is
based on a torque lookup map. You can specify parameters such as torque
converter efficiency, shift maps, and gear ratios in the SimCreator data
file. You can also incorporate lockup transfer cases and differentials.
The brake model includes models of the master cylinder, prop valves,
wheel cylinders, pad friction, and rotor and wheel diameters.
Cabs, Control Loading, Visual Displays
with the RTI driving simulation platform can make use of a variety of
cab, control loading, and visual displays configurations. The
simulation model can be configured to support the data input/output
requirements of various cab types. Keyboard controls, PC
game-style steering wheel and pedal sets, custom mockup vehicle cabs, or
fully instrumented real vehicle cabs are fully supported.
An optional, high-fidelity control
loading system provides feedback on the steering wheel that is directly
coupled with the vehicle dynamics at 2000 Hz. Important factors such as
power steering boost curves, and tire aligning torque are included in
the steering model. You have the power to configure the steering
feedback to represent the vehicle you're simulating.
The quality of
visual graphics will often make or break a customer's acceptance of a
simulator and directly affects the driver's ability to be immersed in
the virtual environment. RTI's visual subsystem can present graphics
generated in OpenFLT, VRML, and most OBJ and 3DS formats. Smooth visual
presentation is attained through a 60 Hz visuals update rate and close
coupling with the SimCreator core software model.
Visual effects such as fog, rain, dynamic shadows,
headlights, deformable terrain, ambient lighting models, and
pre-rendered light maps are supported. Visual rendering techniques such
as full multi-texture, detail texture, bump mapping, environment
mapping, parallax mapping, light sources, and vertex or fragment-based
lighting models are supported. In addition, RTI's visual subsystem is
tightly coupled with the terrain query subsystem to provide highly
accurate correlation between the terrain and visual representations.
Scene and Scenario Control
RTI's scenario control subsystem provides
the ability to control nearly all aspects of virtual traffic,
pedestrians and simulator operation. Scenario development starts with
the SimVista scene authoring tool. SimVista makes it possible to drag
and drop objects into the virtual world and to give them scripted
behaviors to bring them to life.
SimVista comes with pallets of objects that can be
placed in the scene. A set of tiles have been developed that can be
arranged together within SimVista to make a seamless driving
environment. Objects such as buildings, trees, parked vehicles, terrain
features, signs, construction barriers, etc. and can be added to enhance
the visual complexity of the scene. Still more objects can be added and
assigned behaviors that will play out during scenario execution such as
sensors, vehicles, and pedestrians.
The sensor suite includes proximity, planar
time-to-collision and rectangular sensors, in addition to start and end
at runtime when entities in the scenario interact with the sensor.
Within the scripts, commands can control the vehicle, pedestrian and
traffic signals, sounds, text and image display, and changes in
environmental conditions, etc. A full set of data collection and
measurement objects are also available within the scenario control
system. All the tools you need to author your own simulation scenario
content are available with the scenario scripting system.
Motion cues are one of the best ways to enhance the driving experience
in your driving simulator. RTI’s driving simulation software
controls motion through
OverTilt, RTI’s motion control software algorithm. Based on the type of
application, specific driving tasks, and program budget you are working
with, RTI’s expert staff can recommend specific motion system
configurations. The motion control algorithm supports 3 DOF and 6 DOF
motion systems and can be tuned during runtime with a simple graphical