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Meeting	ACGS Committee Meeting 97 - Tahoe - March 2006
Agenda Location	4 GENERAL COMMITTEE TECHNICAL SESSION 4.2 Research Institutions, Industry and University Reports 4.2.1 Research Institutes and Companies 4.2.1.9 Systems Technology Inc.
Title	Systems Technology Inc.
Presenter	David Klyde
Available Downloads*	presentation
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Abstract	A number of improvements have been made to VDANL, STI’s ground vehicle computer simulation application, primarily under a recent contract to the US Army TACOM. Improvements include: enhanced tire model with asymptotic fits of tire data; multi-axle vehicles and trailers – previously limited to 2 axles now up to 10 axles; multiple wheels/tires per axle side; brake thermal model; enhanced bump stop model; damper/bump stop track widths; and speed sensitive steering power assist model. In ongoing work for the Federal Highway Administration (under a subcontract to Battelle), many of these new features have been validated using a tractor-trailer model. The model was developed using parameters for a tractor-trailer combination that was fully instrumented and tested at the National Highway Traffic Safety Administration’s (NHTSA) Vehicle Research and Test Center (VRTC). The parameter determination, conducted on behalf of NHTSA by several organizations, and the test results from the VRTC testing were used to develop a VDANL parameter set and to evaluate the model using a wide range of vehicle tests. The VRTC conducted this testing to develop a parameter set for and to evaluate the vehicle dynamics software for the National Advanced Driving Simulator. This software is called NADSdyna. The results of their evaluation have been published by the SAE and were thus used as basis for comparison for the VDANL evaluation. The STI pilot-in-the-loop flight simulator has been developed as an additional research tool to strengthen the capabilities of STI in the area of real-time flight simulation and pilot-vehicle system identification. The McFadden feel system is a key component in that it provides key proprioceptive cues that enhance the fidelity of the simulation. The McFadden Series 292A 2-axis (pitch and roll) fighter stick was selected for a number of reasons. First, the device can provide a wide range of control force characteristics that are encountered in real aircraft including; linear and nonlinear spring gradients, damping, breakout, deadband, coulomb friction, and travel limits. Second, these characteristics can be used in any combination and be changed “on the fly.” McFadden Feel System Simulator Pilot Computer Projected Display The simulator shown in Figure 1 is a win32 console application designed to interface with Matlab™ for data input and output. It is capable of simultaneously simulating the time response to arbitrary input of as many linear transfer function systems as computer memory will allow. Initialization data for this program is one or more Matlab™ files, each containing a state-space quadruple representation of a linear dynamic system. Included in this file is information the simulator uses to attach its input and output devices to the input and output states being simulated. The current PC-based simulator features: • • Linear airframe equations of motion driven by state space input files; • Multiple aircraft input files; • Nonlinear software rate limits and actuator models; • Data recording of unlimited output states; • Vehicle dynamics that update at 120 Hz and graphics that update at a minimum of 30 Hz; and • Texture-mapped PC graphics with a superimposed head-up display that supports pitch and roll axis tracking tasks. Recent Activities at Systems Technology, Inc. Figure 1: STI Simulator with McFadden Control Loader and Projected Display During a run, the pilot is presented a HUD superimposed on a suitable 3-D environment (see Figure 2). At the end of a run, the input vectors and output time responses of all simulated systems are saved to a Matlab file for future analysis. The simulator uses tracking bars on the HUD to support sum-of-sines and step and ramp discrete tracking tasks. These tasks provide the high gain environment that is required to induce unfavorable pilot-vehicle interactions such as PIO. The discrete tracking task is particularly useful for investigating the effects of rate limiting. Changes to the controlled element dynamics can be introduced during a run to simulate system “failures” or unintended mode shifts. Figure 2: Projected Head-Up Display