Advanced Technologies Testing Aircraft System Research Articles

Wavelet neural network aerodynamic modeling from flight data based on pso algorithm with information sharing and velocity disturbance

For the accurate description of aerodynamic characteristics for aircraft, a wavelet neural network (WNN) aerodynamic modeling method from flight data, based on improved particle swarm optimization (PSO) algorithm with information sharing strategy and velocity disturbance operator, is proposed. In improved PSO algorithm, an information sharing strategy is used to avoid the premature convergence as much as possible; the velocity disturbance operator is adopted to jump out of this position once falling into the premature convergence. Simulations on lateral and longitudinal aerodynamic modeling for ATTAS (advanced technologies testing aircraft system) indicate that the proposed method can achieve the accuracy improvement of an order of magnitude compared with SPSO-WNN, and can converge to a satisfactory precision by only 60–120 iterations in contrast to SPSO-WNN with 6 times precocities in 200 times repetitive experiments using Morlet and Mexican hat wavelet functions. Furthermore, it is proved that the proposed method is feasible and effective for aerodynamic modeling from flight data.

Pilot-Involved-Oscillation Suppression Using Low-Order Antiwindup: Flight-Test Evaluation

This paper presents results from the Saturation Alleviation In-Flight Experiment flight-test campaign in which several antiwindup compensators, designed to reduce the adverse effects of rate saturation of the control surfaces, were tested on the Advanced Technologies Testing Aircraft System. The objectives of the tests were twofold: 1) to demonstrate the potential for rigorously designed low-order antiwindup compensators to reduce the pilot-involvedoscillation proneness and to improve the handling qualities of the aircraft and 2) to compare a variety of low-order antiwindup compensators to determine the importance of different design parameters. The antiwindup compensators were assessed based on pilot handling-quality ratings, pilot-involved-oscillation ratings and pilot comments. The flight-test results demonstrated that the low-order antiwindup compensators tested reduced the pilot-involved-oscillation proneness and improved the handling qualities of the aircraft.

Characterization of Aircraft Wake Vortices by Airborne Coherent Doppler Lidar

This paper presents a new method of wake-vortex characterization by using the 2-μm coherent Doppler lidar in airborne configuration. After modification of the scanning and data acquisition tools, the lidar system has been integrated in the DLR research aircraft Falcon 20. For wake-vortex generation a second DLR aircraft, the Advanced Technologies Testing Aircraft System equipped with a smoke generator on the portside wing, was used. Different scanning modes and flight strategies have been investigated and tested during three tryout flights. Results of vortex trajectories and circulation strengths, measured in the upper part of and above the atmospheric boundary layer, are presented. Based on the results of the tryout flights, the potential of this method for characterization of wake vortices from large transport aircraft equipped with smoke generators is estimated.

LEARNING ABOUT FLIGHT CONTROL USING AIRBORNE SIMULATION

The article deals with an educational concept in the field of experimental flight systems and applied flight control. Within the scope of a university teaching position at the Technical University of Berlin, the author provides students with theoretical information and practical experiences in flight control and flight-testing. The students come from different branches of aeronautical education and have very different previous knowledge. Within two semesters the students learn in the lectures about particular aspects of theoretical and applied flight control, aircraft dynamics, man/machine systems, real-time simulation, flight-testing, software engineering concepts, etc. In laboratory courses the students work with a modern computer based simulation and control system design tool. They learn how to analyze dynamic systems and how they can be influenced by feedforward and feedback controllers. In the last part of the second semester the designed controllers are implemented in the fly by wire system of DLRs flying test-bed ATTAS (Advanced Technologies Testing Aircraft System). The flight-tests are performed by DLR test pilots. After the two semesters the students have to write a report including all theoretical results and flight-test data evaluations and they have to pass an oral examination.

Calibration of 5-hole Probe for Flow Angles from Advanced Technologies Testing Aircraft System Flight Data

This paper describes the investigations carried out to calibrate the 5-hole probe for flow angles from advanced technologies testing aircraft system flight data. The flight tests were carried out with gear up and at nominal mid-centre of gravity location for two landing flap positions, *df = IN and 14?. Dynamic manoeuvres were executed to excite the short period and Dutch roll mode of the aircraft. In addition, pull up, push down and steady sideslip manoeuvres were also carried out. The data compatibility check on the recorded flight data has been carried out using maximum likelihood output error algorithm to estimate the bias, scale factor, and time delay in the pressure measurements from the 5-hole probe mounted on a noseboom in front of aircraft nose. Through a way of kinematic consistency checking, flight-validated scale factors, biases, and time delays are determined for the differential pressure measurements for both angle of attack and angle of sideslip. Also, the dynamic pressure measurement is found to have time delays. Based on the earlier investigations, it is once again confirmed that the measurements of attitude angles, obtained from the inertial platform, clearly indicate time delays referred to the other signals like linear accelerations and angular rates which are measured with the dedicated flight instrumentation package. The identified time delays in attitude angles agreed well with the inertial platform specifications. The estimates of sensitivity coefficients and scale factors from the flight data analysis correlates reasonably well with the manufacturer Rosemount calibration curves for the tested Mach range 0.23-0.53. The flight data analysis at Mach number of about 0.59 indicate Mach dependency for the angle of attack.13;

Assistant systems for aircraft guidance: cognitive man-machine cooperation

This paper presents the concept of cognitive assistant systems which represents an approach to ensure the highest degree possible of situation awareness of the flight crew as well as a satisfactory workload level. This concept offers the solution to counteract susceptibility to pilot errors typical of lack of attention or other cognitive limitations. It is founded on cognitive system engineering. This technology enables a cockpit design in order to systematically comply with the requirements of ‘Human-Centred Automation (HCA)’. The underlying approach behind the concept has become real with the development of the cockpit assistant system prototype family CASSY/CAMA as described in this paper. CASSY/CAMA has been extensively tested in a flight simulator and successfully field tested with the ATTAS (Advanced Technologies Testing Aircraft System) of the DLR. Some of the test results with CAMA will be presented in this paper.

Active sidestick technology – a means for improving situational awareness

The use of an active sidestick in FBW-flight control is discussed and the specific features of both passive and active sidesticks are compared. Additional tactile information which could be provided by active sidesticks is seen as an important factor to improve the situational awareness of the pilot. An unique active sidestick concept based on the electro-magnetic actuation principle (electro-magnetic sidestick, MAGSI) is presented. This system is the key element in DLR's research programme EPIAS (Enhanced Pilot Information by using Active Sidestick) which is scheduled to be flight tested on the ATTAS (Advanced Technologies Testing Aircraft System) in-flight simulator at the beginning of next year.

Identification of actuation system and aerodynamic effects of direct-lift-control flaps

A maximum likelihood parameter estimation method for nonlinear systems has been applied to flight data of the research aircraft ATT AS (advanced technologies testing aircraft system). The emphasis is on modeling and identification of 1) dynamics and nonlinearities of actuation systems for the direct-lift-control (DLC) flaps, and 2) their aerodynamic effectiveness and other influences. These specially designed flaps provide an additional longitudinal control suitable for in-flight simulation or load alleviation investigations. The identification results indicate that under aerodynamic loads the possible maximum flap deflections are severely limited. The flightestimated aerodynamic characteristics are compared with those predicted by wind tunnel and analytical methods. It is found that the DLC flaps are somewhat less effective aerodynamically than they were designed for. More importantly, the transit time lag in the downwash generated due to flap deflections significantly affects the dynamic pitching motion. Furthermore, it leads to certain additional unsymmetrical and interference effects.