News

Updates on what's happening at STI:

The intent of this ongoing project for NASA Dryden Flight Research Center is to develop and validate means to alert, constrain and thereby alleviate loss of control (LOC) associated with unfavorable pilot-vehicle systems (PVS) interactions present in high gain, closed-loop PVS operations. While the effective aircraft dynamic properties involved in these events have been extensively studied and understood, similar scrutiny has not been paid to the many aspects of the primary manual control system that converts the pilot control inputs to motions of the control surfaces. It has often been tacitly assumed that the adoption of fly-by-wire (FBW) systems has eliminated the primary manual control link as an important player in LOC situations. Consequently, the impact of static and dynamic control system effects that distort "ideal" pilot to surface relationships, the near absence of manipulator tactile cues for some FBW systems, as well as the total elimination in FBW systems of some favorable cues present in traditional hydro-mechanical systems have not received detailed attention. The purpose of the developments proposed in this program are to redress this neglect, to develop and, ultimately, to validate remedial manual control systems.

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Loss of Control Detection Using Wavelets

In a recently completed program for NASA Dryden Flight Research Center wavelet transform methods were developed for on-line detection of aircraft loss of control. Wavelet transforms were compared with Fourier transform methods and shown to more rapidly detect changes in the vehicle dynamics. This faster response was due to a time window that decreases in length as the frequency increases. New wavelets were defined that further decrease the detection time by skewing the shape of the envelope. The wavelets were used for time vary ing power spectrum and transfer function estimation. Smoothing was used to tradeoff the variance of the estimate with detection time. Stability metrics were estimated from the frequency response and models, and it is these time varying metrics that are used for loss of control detection. An analysis toolbox was developed for post-processing simulation and flight data using the wavelet analysis methods. A subset of these methods was implemented in real time and named the Loss of Control Analysis Tool Set or LOCATS. A manual control experiment was conducted using a flight control system hardware-in-the-loop simulator for a large transport aircraft, in which the real time performance of LOCATS was demonstrated. The next step will be to use and assess the wavelet analysis tools in a flight test environment.

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Papers: AIAA2004-5064 & AIAA2004-4072

Improved Flutter Flight Test Techniques Using Wavelets

Classic flutter flight testing involves the evaluation of a given configuration at a stabilized test point before clearance is given to expand the envelope further. At each stabilized point flight test data are compared with computer simulation models to assess the accuracy of predicted flutter boundaries. Because of the time constraints associated with these procedures, the Air Force has been seeking methods to improve current flight test methods. In a program conducted for the Air Force Flight Test Center a technique was developed that provides a rapid, on-line tool for the identification of aeroservoelastic (ASE) systems. The technique involves the use of discrete wavelet transforms to compute the impulse response (Markov parameters) of the estimated system. This is then used in the Eigensystem Realization Algorithm (ERA) method to compute the discretized state-space matrices. The technique used herein includes metrics that are used to assess the validity of the identified system. Although the method does require that the identification begin from initial conditions that are quasi-steady, it has been shown to be relatively insensitive to input forcing function. A model of a modern naval fighter aircraft was used to evaluate the capabilities of the identification method. The identification techniques were evaluated with and without an active oscillation controller in place.

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Paper: AIAA2004-5065

The Dynamic Icing Detection System (DIDS) was developed by STI in a recent program for the NASA Glenn Research Center. The basic concept is to apply system identification techniques to identify icing - induced changes to an aircraft's aerodynamics in near real time. The DIDS is intended to augment other icing detection options, such as icing sensors, to improve pilot situational awareness regarding icing. Developing strategies to achieve good identification consistent with aircraft operational constraints has been an important challenge. DIDS is designed to operate on signals expected to be available from existing sensors on modern aircraft. Thus, DIDS will consist of software to be integrated with existing avionics. Much of the work in the last year has been devoted to developing prototype DIDS software. This sofware was initially tested using a simulation of the NASA Twin Otter aircraft featuring an icing accretion model. Much of the work on the icing model was done by the University of Illinois Urbana-Champaign. Damos Research Associates (www.damosaviation.com) assisted with human factors assessments of the DIDS. A flight test of the DIDS prototype was conducted at NASA Glenn in Cleveland using the NASA Twin Otter aircraft. Significant icing was obtained during two flights. These data have been analyzed to assess and refine the DIDS.

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Paper: AIAA2000-0364

NASA Twin Otter Icing Research Aircraft

Helicopter Autorotation Trainer

Rotorcraft autorotation is a time-critical maneuver that allows very little margin for error in the timing and magnitude of the pilot's control inputs. Pilot training on autorotation procedures are also inadequate due to the inherent dangers involved. Under NASA sponsorship, STI has developed a real-time trajectory optimization method for guiding a rotorcraft pilot through an autorotation following a total loss of power. Preliminary tests strongly indicate that successful autorotations may be performed from well within the unsafe operating area of the height-velocity profile of a helicopter by employing a fast and robust optimal algorithm that provides guidance on control inputs through an intuitive pilot display. The algorithm generates optimal aircraft trajectories and control commands via the direct-collocation optimization method, solved using a commercially available nonlinear programming problem solver. The commanded control inputs generated by optimal control formulation are collective and aircraft pitch which are easily tracked by a pilot or can be converted to control actuator commands for automated operation during autorotation. The formulation of the optimal control problem was carefully tailored to emulate solutions resembling those of an expert pilot, accounting for the performance limitations of the rotorcraft as well as safety concerns. The concept has also been extended to provide pilot guidance for continued take-off or landing following a single engine failure in a dual engine helicopter and could be used to provide a pilot advisory on the take-off decision point (TDP) following an engine failure. STI has applied for a patent on this technology and the guidance display.

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Papers: AHS-UAV-2005 & AHSForum61-Bimal-Aponso

AIRCRAFT GROUND HANDLING

In recent work, STI has merged its aircraft and ground vehicle expertise to address issues surrounding aircraft ground handling. This research revealed common threads between the behavior of aircraft and automobiles including the use of lower order equivalent systems modeling as a means of characterizing vehicle dynamics and application of the STI tire model. The composite slip tire model was validated against a comprehensive aircraft tire test data set that included braking and cornering runs conducted with main and nose gear tires at several service pressures. The validated tire model was successfully incorporated in both analytical and piloted simulation models. These complete aircraft models were validated with ground handling flight test data that included rudder pedal frequency sweeps, runway lateral position maneuvers, and straight line braking runs. Building upon its long history in aircraft flying qualities research, a set of ground handling demonstration maneuvers and corresponding metrics were developed by STI and used in both simulation and flight test activities. The results of these activities was the successful development and flight test evaluation of Stability Augmentation Steering System as means to improve the ground handling of a Navy jet trainer.

Papers: AIAA 2002-4798 & AIAA 2003-5318

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STI worked with Boeing and the Navy to improve the ground handling of the T-45

FUSED REALITY (Patent Pending)

Fused Reality is a novel technique conceived at STI that is similar to the blue-screening technique that Hollywood is using (employed initially by Hitchcock in Vertigo). The critical differences are: 1) Hollywood requires carefully controlled lighting conditions, and 2) the computer processing is done off-line - Fused Reality on the other hand, can operate over a wide range of lighting conditions, and the processing is executed in real-time thus enabling real-time fusing of the virtual and physical environments. STI is currently applying for a patent on the Fused Reality technique and its coined term. Fused Reality employs three proven technologies - live video capture, real-time video editing (blue screen imaging), and virtual environment simulation - thus offering a quantum jump in training realism and capability. Video from the trainee's perspective is sent to a processor that preserves near-space (cabin environment) pixels and makes transparent the far-space (out-the-cabin) pixels using blue screen imaging techniques. This bitmap is overlaid on a virtual environment, and sent to the trainee's helmet mounted display. Thus the user directly views the physical cabin environment, while the simulated outside world serves as a backdrop.

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Key Elements of the Fused Reality System:
Helmet-Mounted Display, Helmet-Mounted Micro-Camera, Interactive Hardware (Sub-Machine Gun),
Portal Surface (Magenta Dish)

Biodynamic Modeling

STI recently concluded a program for the Human Research and Engineering Directorate of the U.S. Army Research Laboratory at Aberdeen Proving Ground, MD to develop an integrated anthropometrics, vehicle dynamics, and biodynamics software tool. The ultimate goal of this program was to develop a computer aided design tool, referred to herein as AVB-DYN, for analyzing the effect of dynamic environments on the habitability and performance of the human operator in specific workstation designs. The AVB-DYN software addresses: anthropometrics for operator workstation design and human posture assessment; vehicle dynamics to determine the acceleration environment at the vehicle-mounted operator workstation; biodynamics for the assessment of human motion in response to vibration inputs from the vehicle; and dynamic systems analysis for vibration and ride quality analysis, and manual control and human transmissibility assessments. The anthropometrics are provided by the JACK software from UGS PLM Solutions, which interacts with AVB-DYN as a stand alone application. The innovation was to provide a complete and validated biodynamic model that has been hosted in a multibody computational environment, dynamic systems analysis tools that allow the characterization of biodynamic environments according to standard guidelines, and a means for evaluating the biodynamic interference with human task performance. Representative tasks such as driving are accommodated as a vehicle encounters selected terrain profiles at specified speeds. The resulting biodynamic model has been validated for the driving posture using a human subject data collected with a ride motion simulator.

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Link to UGS PLM Solutions and the Classic Jack software:
http://www.ugs.com/products/tecnomatix/human_performance/jack/cla ssic_jack.shtml

Biodynamic Interfaces for Human/Machine Control

Real Time Detection of Human Fatigue

The goal of this ongoing project for the Air Force Office of Scientific Research is to develop and validate an automated, real-time, fatigue detection system for operators seated at workstations. The system can be used for alerting the operator, self-assessment, supervision, and scheduling. The operational environments of interest include stationary and airborne command centers. The proposed system will combine (1) a well-validated mathematical model of circadian rhythm and performance, (2) wrist mounted actigraph and lux sensors used to initialize the circadian rhythm model, (3) a non-intrusive (and non-invasive to the primary task) visual face and eye monitoring system that will measure eye point angle, blink rate, percentage eye closure, and other physiological metrics, and (4) signal processing methods such as the extended Kalman filter that will optimally combine the model's fatigue prediction with the real time physiological measurements. The hypothesis is that this combined system will result in improved detection of operator fatigue. A pilot study undertaken by the Division of Sleep Medicine at Brigham and Women's Hospital will demonstrate the system and test the hypothesis using a small subject population. A set of cognitive and psychomotor tasks will be used to provide an objective performance measure. The tracking equipment being used is faceLab, a product of Seeing Machines, Inc.

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Fatigue and Performance Modeling of Sleep-Deprived Soldiers

Soldiers with chronic sleep restriction have reduced cognitive performance that can result in dangerous and deadly behavior. Current mathematical models used to predict performance are based on the Two-Process sleep regulation and have been well-validated for single episodes of sleep deprivation, but not for chronic sleep restriction and recovery. An innovative new modeling approach is being developed in a project for the Army Medical Research and Materiel Command based on hybrid neural networks, where the existing circadian pacemaker model will be retained and combined with a neural network mapping of the fatigue and performance metrics. The model will first be trained to duplicate existing Two-Process models, and then will be altered as needed and training directly from experimental data. A technical issue that will be resolved is how to include sleep and wake protocols in the model structure and training. Validated models can be used to determine unit readiness and to schedule sleep regimens. Real time versions combined with physiological measurements can potentially be used to adapt to and monitor individual soldiers.

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Cognition of Impaired Drivers

STI is currently involved in two National Institutes of Health grants to investigate cognition in impaired drivers. These studies are being funded by the National Institute of Mental Health and by the National Institute of Child Health and Human Development. On these grants STI has teamed with the HIV Neurobehavioral Research Center in San Diego, CA for one study; and with the University of Minnesota, Sister Kenny Rehabilitation Services, The Courage Center and the University of Vermont for the other. Both of these grants use STISIM Drive^TM to investigate subject populations with reduced cognition due to either multiple neurological disorders or traumatic brain injury. Through clinical trials the simulator will be used to determine if (1) the simulator can distinguish between people with varying driving ability (discriminant validity); (2) if driving performanc e in the simulator matches on-road driving performance (concurrent validity); (3) you get similar simulator session results when the test is repeated a second time at a later date (test-retest reliability); (4) determine if using STISIM Drive^TM changes a person's self-awareness of their driving abilities.

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Novice Driver Training

In work conducted for the Centers for Disease Control STI created a relatively self-administering driver training system based on STISIM Drive^TM and trained over 500 drivers in several high schools and two research laboratories. The system has been operated with minimal supervision in a high school setting and has been received with enthusiasm by teachers and students. The training system runs on a standard desktop PC with the addition of an nVIDIA GeForce graphics card and a game port controller. These hardware upgrades are relatively low cost (about $350, plus about $500 for software) which is an important consideration if these training systems are ever to be widely used in high schools.

To make the training system as self-administering as possible, STI developed a software-based administrative platform. The purpose of the administrative platform was to permit relatively automated subject registration, briefing and evaluation of driving behavior in a high school environment with minimal supervision. The automated training platform: 1) allows a new subject to log-in to a database, 2) briefs the subject on the background and objectives of the training, 3) familiarizes the subject with the driving simulation, 4) administers the required training, 5) logs data and 6) provides performance assessment and gives feedback to the subject. Simulator performance measurement includes assessment of vehicle motions, driver control responses, and relative motions with respect to other vehicles and pedestrians. Typical measures include accidents, violations, speed and lane deviations, time to collision, use of turn indicators, reaction time, etc. During a second phase of this project we will analyze novice driver records of accidents and violations. We will compare the records of our subjects with other control subjects in the same age group to see whether simulator training has reduced the incidence of accidents and violations.

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Novice Driver Training in the Class Room

Watch this space for information on upcoming conferences where STI personnel will be attending and presenting papers.

 

STI's Dave Klyde will be attending the USAF T&E Days, in Los Angeles, CA, February 5-7. He will be presenting a paper co-authored by Calspan and AFFTC, entitled "Use of Simulation to Create a Flying Qualities Database."

 

We will be exhibiting STI PARASIM at the 2008 Parachute Industries Association International Symposium , in Barcelona, Spain, February 18-24.

 

We will be exhibiting STISIM Drive at the American Occupational Therapy Association's (AOTA) 88th Annual Conference and Expo , in Long Beach, CA, April 10-13. 

 

We will be joining our Australian representatives, Defcon Technologies, in exhibiting STI PARASIM at SimTecT, in Melbourne, Australia, May 12-15.

 

August 2008 

We will be exhibiting STISIM Drive at the American Psychological Association's 116th Annual Convention , in Boston, MA, August 14-17.

 

STI's Dave Klyde and Brian Danowsky will be attending and presenting papers at the AIAA Atmospheric Flight Mechanics Conference and Exhibit , in Honolulu, HI, August 18-21.

 

The 2008 STISIM Drive Users Group Meeting will be held September 17-18, 2008, at the Université Laval in Quebec City, Canada. Plan to attend with us in beautiful, historic Quebec City, which is celebrating its 400th anniversary this year!