AHEAD Simulation Lab Applications

Some of real-world applications for the AHEAD-SL include convenient comparisons wof noise, vibration, passenger seating and human factors.

Noise and Vibration

The Noise and Vibration application of the Simulation Lab Lab provides wide range of engineering quality vibration and audio feedback for the driver. Input to the system can come from: recorded data, simulated data (e.g., CAE), or a combination of the two. The Simulation Lab allows engineers and management to subjectively evaluate these data throughout the design and development cycle of the vehicle. This includes early development before prototype hardware is available to late development when design objectives can be verified. These subjective evaluations can be critical when the alternative is making decisions based purely on analytical data which are, at their very best, difficult to translate into driver satisfaction.

Users of the Simulation Lab are placed on a geo-specific portion of the DaimlerChrysler Chelsea Proving Grounds. As they drive through the simulated world, they encounter the same noise and vibration "events" as they do at the proving grounds. However, unlike "real" driving, drivers of the Simulation Lab may change vehicles or vehicle characteristics by merely touching keys on a touch-pad. In this way engineers and managers can conduct A/B comparisons immediately with repeatability and reliability. In addition, drivers may switch to an "abstracted" version of the proving grounds where events may be repeated continuously and switch to new events instantaneously.

Below are some the comparisons that can be made:

• Compare the target vehicle against the newest CAE data
• Compare the target vehicle against the newest proving ground data from the vehicle prototype
• Compare the CAE data, the data from the first prototype, and this newest prototype all against the target data to see how far we've come.
• Compare other factors, such as reducing the wind noise by 1 decibel

The physical noise and vibration platform includes six degrees-of-freedom that subject the driver to vibrations at the most significant tactile locations; the steering wheel, floor, and seat. These "sub-platform" locations are isolated from one another to eliminate "cross-talk" between other sub-platform locations. Also, an off-the-shelf high-quality binaural sound system (also used in the sound quality labs at DaimlerChrysler) has been integrated into the Simulation Lab to recreate the sounds with detailed realism.

For the first time, engineers are able to perform the following types of tests:

• Perform subjective vs. objective evaluations - The Simulation Lab provides a tool for making subjective sense of graphs and plots.
• Make instantaneous A/B comparisons - Vehicles or vehicle subsystems are changed in the press of a button rather than parking and physically changing the vehicle being driven.
• Customized ride events - Not enough impact slabs on the actual ride road? In the Simulation Lab endless events can be duplicated with the press of a button.
• Focus - The Simulation Lab provides opportunities to more easily focus on specific issues. For example, removing all the vibration except the floor Z-component.
• Setting targets - In the early design phase users have the opportunity to create their own subjective targets for the vehicle and from that experience generate more precise objective measures.
• Database of Rides - Every measured and analytically derived vehicle or vehicle subsystem can be stored in a database. For example, if you can’t bring clearly to mind what the first prototype felt like during an evaluation held months ago, you can always drive it again in the Simulation Lab.

The vibration subsystem is able to reproduce a nearly flat response from 5 Hz to 200 Hz in multiple degrees-of-freedom at the seat and floor. A true flat response is achieved by identifying the appropriate transfer function through an iterative pre-processing step. This kind of attention to engineering detail allows the system to recreate the source data with extraordinary fidelity.

The steering wheel/column also includes rotational and Z-direction vibration degrees-of-freedom. The rotation control also provides closed-loop torque feedback to the driver to deliver the proper feel of driving.

The sound subsystem is comprised of a combination of a 4-way speaker system that recreates a near perfect "binaural" sound field through the use of special equalization systems. The frequency range of the system is 200 Hz to 20 kHz.

Alternatively, a true binaural sound field can be generated through the use of headphones. A subwoofer is included to generate low frequency acoustic energy. Real-time control of the sounds is accomplished through the use of complex algorithms that control a series of sound samples and filters. These sounds are synchronized to the vibration and visual signals by direct control of the host computer and as such are under the control of the driver's input to the throttle, brake and steering wheel.

Occupant Packaging Simulator

The Occupant Packaging Simulator of the Simulation Lab provides a test platform for physically evaluating how the driver "fits and feels" inside a vehicle that is being designed. However, unlike static mock-ups of an early design, these evaluations can be made under dynamic real-time driving conditions.

The OPS platform allows occupants in front and rear positions to subjectively evaluate the packaging design. Engeneers can do the following:

• Design comparisons and evaluations
• Perform market research
• Perform competitive vehicle analysis
• Make benchmark comparisons.

A prominent advantage of this tool is that the Simulation Lab can change from one design package to another in a matter of seconds. This rapid ability to make A/B comparisons can result in significant cost savings as well as increased speed-to-market opportunities. Jury evaluations can also be performed in a controlled, repeatable laboratory environment.

Before the OPS platform was integrated with the Simulation Lab, all evaluations were done statically. Now ergonomic specialists, juries, and management can &"drive" the vehicle on new or familiar roads and get a sense for the package in a much more realistic environment. These evaluations can take place well in advance of full prototype development. As with all Simulation Lab applications, the driver has complete control of the vehicle using the normal controls to maneuver through the virtual world.

The OPS platform has vertical and fore/aft degrees-of-freedom for the following components:

• Driver seat
• Driver floor
• Pedal package
• Steering column
• Instrument panel
• Passenger seat
• Passenger floor
• Center console
• Rear seat
• Rear floor

These degrees-of-freedom on the platform are computer controlled so that design data can be downloaded to the system and adjusted in real-time. The platform is typically covered with mockups of an appropriate vehicle shell resulting in an exceptionally real driving experience.

Human and Machine Interface

Human and Machine Interface is a highly flexible component of the Simulation Lab that allows a wide array of human factors experiments. One of the most important features of this lab component is the speed with which vehicles can be integrated into the Simulation Lab. The lab is capable of integrating anything from a crude seating buck to a fully running production vehicle within a day. Moreover, the minimal intrusions required for integration allow an integrated vehicle to be made road worthy again as quickly as it was modified for the Simulation Lab.

This rapid integration is essential in order to be effective in the design cycle for early vehicle prototypes. That is, when the first fully functional prototypes are built, many interested labs throughout DaimlerChrysler are eager to take control of it in order to conduct their tests. This highly competitive situation means that tests done in the Simulation Lab need to take as little as three days and by the end of that third day, the vehicle must be released in the same running condition it was in when it entered the lab.

All in a matter of hours virtually any vehicle or vehicle buck can be prepared for the Simulation Lab by integrating the throttle, brake, gear selector and steering column with the gForce SmartNode steering torque system. Additionally, when instrument clusters and speakers are available, they are powered and driven in real-time to provide the appropriate driver feedback.

A wide array of experiments can be performed in a safe and consistent laboratory setting:

• Ergonomic (anthropomorphic) packaging studies
• Night-time interior illumination
• Visibility studies
• Integration and testing of new technologies (from simulated to hardware-in-the-loop)
• Cognitive human factors research