Proposal of the Experimental Simulation Method for

Proposal of the Experimental Simulation Method for Handling Qualities Evaluation Andrzej Tomczyk Department of Avionics and Control Systems, Faculty of Mechanical Engineering and Aeronautics

Rzeszów University of Technology, W. Pola 2, 35-959 Rzeszów, POLAND

Abstract Purpose - The main targets of the work are analysis and primary evaluation of different control laws implemented on experimental indirect (Fly-by-wire) flight control system designed for perspective general aviation aircraft. Methodology - The control law tests have been accomplished on the flight simulation stand equipped with side-stick, throttle lever and flight instrument display. Every evaluator was caring out 2 to 4 five-minutes instrument flights (IR) according to command shown on the screen. PZL-110 general aviation aircraft properties and seven modes of control system operation were modeled and examined. Findings - Results of evaluation by forty-five commercial pilots are analyzed and handling qualities of the small aircraft equipped with the indirect flight control system (Fly-by-wire) have been examined. In this way the most convenient control law was chosen for design the user-friendly, human-centered, simplified software based flight control system. Practical implications- The result of research can be implemented on real indirect flight control system dedicated to general aviation aircraft. Originality - This paper presents the practical approach for analysis of Handling Qualities of general aviation aircraft equipped with indirect flight control system. This kind of works concern to military and transport airplanes are known, however there are no published work in the area of small aircraft so far.

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Keywords Flight control systems, Handling Qualities, Flight simulation, General aviation aircraft

Paper type Research paper

Introduction Light aircraft equipped with classic, mechanical flight control systems require full aviation training and comprehensive theoretical knowledge from the pilot. Measuring and navigation systems require extensive observation, detailed analysis of instrument indications, and complex interpretation. In military aircraft and state-of-the-art jetliners, integrated systems of information collection, processing and presenting, along with the fly-by-wire flight control systems have been implemented (Pratt, 2000; Moorhouse, 2000). Current technological level allows undertaking efforts to design an automated and integrated flight control system in light aircraft. New design concepts allow improvements in operating properties of already existing and newly designed executive aircraft, as well as increase flight safety. For this purpose, efforts are undertaken to design aircraft exhibiting required handling qualities, and automate many navigating and piloting activities. Specialized systems of handling and navigation data visualization, which facilitate interpretation of instrument readings (for example, tunnel display), have been designed. Integrated navigation systems, based on satellite systems are used; global aircraft Automatic Depended Surveillance (ADS) systems are designed. As far as piloting technique is concerned, limits are set by aircraft characteristics, which result from aerodynamics laws, and flight mechanics and dynamics. An aircraft's complex dynamic properties are the reason that attitude stabilization, and especially

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takeoff and landing procedures, require the pilot to have proper coordination of manual flying controls displacement and engine power management, as well as acting-ahead abilities, made necessary by aircraft's inertia. A significant difficulty in piloting is the necessity to abide by operating and safety limitations. Simple devices which help pilots and warn them when limits are being exceeded have been designed, among them: proper mass and aerodynamic balance, or devices controlling aircraft's stall, such as stick-shaker and stick-pusher, for example (Hodginson, 1999; Webster, 2001). The next stage of control automatization is applying the indirect flight control systems (fly-by-wire). The term "fly-by-wire control system" is widely known and extensively used. I believe, however, that expression "indirect flight control system" is better suited to describe this particular mode of aircraft control. Pilot controls the plane through a computer system, which constitutes an indirect control. The term "fly-by-wire" describes only physical implementation of a flight control system. With "fly-by-light" and wireless flight control systems being recently introduced, the physical characteristics of a flight control system become less significant. An indirect flight control system serves mainly the purpose of shaping the required control properties of an aircraft regardless of its physical construction. The aircraft is automatically controlled, and the pilot, by displacing the stick, enters information about desired flight parameters to the flight control computer. This flight control method allows for almost unlimited choice of designing the aircraft's handling qualities and also makes it possible to control statically unstable aircraft. In recent years, a growing interest in light airplanes (which constitute the general aviation sector) has been observed. This trend has been particularly visible in the U.S.A. where AGATE (Advanced General Aviation Transport Experiment) had been started in 1994 and continued, from 2000, as SATS (Small Aircraft Transportation System). These projects

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unite several federal institutions, universities and aircraft manufacturers for the purpose of establishing a general aircraft transportation system (Holmes, 2003). Similar program was started in Europe (Anon., 2006). The main idea of these projects is finding solutions for design a safety personal aircraft. From safety and handling qualities point of view, the flight control system plays an important role in the new generation small aircraft design. Very often there is suggestion that piloting of the light aircraft should be so easy as a car driving (Kocks, 2001; Moore, 2003; Wilson, 2001). Advanced flight control systems dedicated to general aviation aircraft has been presented by Wichita State University and Raytheon Aircraft Company (Duerksen, 2003; Lambregts, 2005; Steck, 2004) and Delft University of Technology (Bost, 2006; Lam, 2006; Mulder, 2005). Some results of simulation and flighttesting were showed as well. Research team of the Department of Avionics and Control, Rzeszów University of Technology, has been working on a long-term project of designing a small aircraft flight control system, which would allow pilots with limited aviation experience to establish a safe control of the aircraft. The project draws from experiences and solutions employed in earlier designs of our team: digital flight control system for general aviation and commuter aircraft (1990) and navigation and control system for Unmanned Air Vehicles (1999). The main goal of the project is to improve safety and Handling Qualities of general aviation aircraft so that airplane becomes pilot-friendly, "almost unmanned" aircraft. A proposal of employing an intuitive, human-centered, simplified software-based flight control system in general aviation aircraft has been taken into consideration. Airplanes equipped with such a flight control system belong to a new class of general aviation aircraft with improved safety and efficiency handling properties – Safe Flying Airplane (SFA) or Facilitated Airplane (FA) (Tomczyk, 2003; Tomczyk, 2004). In this paper, the preliminary results of the

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simplified flight simulation pilot evaluation of the control laws applied in the indirect flight control system SPS-1A are presented.

Indirect Flight Control System SPS-1A The basic idea of the project is to employ an indirect (Fly-by-Wire) software-based flight control system characterized by high degree of automatization, leading to an almost “unmanned” general aviation aircraft. “Unmanned” does not mean eliminating humans from the control process but changing their role in the system. User-friendly control system should shape handling qualities of an aircraft in such a way that control becomes easy and safe. Pilot retains the crucial role of decision-maker, and control system takes appropriate steps to fulfill his requirements, or suggests optimal methods of implementing his decisions. Such a system may be considered to be pilot’s electronic assistant as it integrates simplified handling flight controls and autopilot functions, and reduces the complexity of interactions between aircraft attitudes, power settings, and rate of motion, and in conclusion limits the possibility of loss of control. General functional properties of the proposed system have been presented at the SAE/AIAA World Aviation Congress, Los Angeles, CA, 1998 (Tomczyk, 1998). Main characteristics of the system may be described as continued stabilization of attitude orientation of an aircraft and guidance (for example, flight along a selected path on constant altitude). However, pilot can influence the flight state at any moment by displacing the sidestick for a manual control following the general rule: if pilot does not take action (side-stick remains in neutral placement), previously planned flight plan is realized, or, previous safe flight conditions are maintained.

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Take in Figure 1 The general structure of the indirect flight control system is presented in Figure 1. The system is based on three independent flight control computers (CC-x) that control double electromechanical actuators. Pilot selects a control option (system’s mode) using a control mode selector panel (SP) and then controls the aircraft by the means of side-stick (SI) and throttle lever (TI), which plays a role of the speed lever during flight. The main sources of information concerning angular orientation of aircraft are Attitude and Heading Reference Systems (AHRS). Parameters of aircraft’s movements in relation to air are measured by Air Data Computers (ADC). Low cost ADC and two versions of AHRS (one is based on Fiber Optic Gyros, the MEMS technology sensors were used in the second one) were designed by the project team. Navigation system, consisting of integrated receiver GNS-530 (GPS, VOR, ILS, comm) and backup receiver GPS-35, assures proper navigation and instrument-assisted landing. “Other measurements” block presents remaining sensors and measurement systems, engine instruments included. Measurement systems are multiplied (hardware redundancy). Integration of the system is established by a triple digital, low cost, bi-directional databus network CAN-2 (CAN1H - high speed bus, CAN2L and CANL3 – low speed, higher reliability buses) that connects all system elements with controlling computers. Mechanical linkage (ML) is applied as an emergency control of engine. In case of malfunction of all three controlling computers or all three CAN-2 network lines, or total breakdown of measurement systems, an emergency direct control of actuators is possible by the means of independent PWM signals (line PWM) generated directly in sidestick module. Maintenance computer (MC) may be connected in order to complete service tasks; full testing or adjustment of the system and it was used during flight-testing of the control system, as well.

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Operation of an indirect flight control system must be characterized by high degree of reliability. Diagnostic systems that evaluate state of control system and on-board instruments have been employed. Method of controlling aircraft is determined on the basis of rules established for the following levels: • Level I – normal control, all the properties of indirect flight control system are employed, • Level II – simplified control, only the simple CAS (Control Augmentation System) or forming filters are used, • Level III – emergency control, displacement of aerodynamic control surfaces depends directly on side-stick displacement. Change of control method is realized by on-board supervisory subsystem if imperfect operation of crucial elements of control system is discovered. However, we can also consider an option of manual switching to Level II operation in case of any problem with autopilot or for "more manual" handling a plane. Level III should be used in emergency only for reaching a safe area where airplane-parachute type lifesaving system could be used. The control laws were chosen according to control level; very simple for level III and more sophisticated for level I of control system. The basic idea of control system being designed is appropriate stabilization of angular orientation of aircraft without pilot’s intervention, and timely following of pilot’s instructions that change attitude and flight parameters. Employing a model following control system has solved this problem (Tomczyk, 2006). Its simplified diagram is presented in Figure 2. Take in Figure 2 If pilot does not displace the side-stick, aircraft is stable (current state vector X is maintained) and influence of external factors (N) is minimized. By displacing the side-stick, pilot generates directional signal UP. Expected reaction of aircraft is described by change in

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vector YM following the properties of the model of ideal aircraft (MoIA) employed in the particular option of aircraft control. Forming filter FF allows initial transformation of the UP signal into information about intended change in angular orientation of aircraft (UPF). Basic properties of flight control systems are shaped by selection of ideal aircraft model. Selection of the model is a result of extensive theoretical analysis as well as practical experiences, including flight simulator tests and flight tests. Output signal of the model (YM) is compared to realize properties of the aircraft (observation matrix C maps measured vector of output signals Y from measurement subsystem (ME) to signals YC with structure compatible with model’s output vector YM) and difference ∆Y is minimized. Flight computer (FC) controls aircraft (A/C) by actuator (AR). Blocks encircled with a dotted line form a control augmentation system, which may be described as Handling Qualities Augmentation System, or Handling Augmentation System (HAS). Model-following flight control system is solution of destination; simplified versions of control systems have been tested as well. In case of malfunction of measurement systems, control level II or III should be used when deflection of aerodynamics control surfaces depends directly on stick displacement. In such situation, dynamic properties of actuators significantly influence quality of manual control. Significant improvement of flight control quality may be obtained by employing appropriate forming filter. The different variants (modes) of the control laws were applied into flight simulation stand and some experiments were used for their evaluation.

Flight Simulation Laboratory Stand The main function of the described flight control system is research the set of control algorithms using for forming filter and flight computer control laws synthesis. The preliminary step of the research is simulation experiment.

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The experimental indirect flight control system was tested at the laboratory stand (Rogalski, 2004a). There are two main goals of this activity. At first, we are going to conduct research in the area of small aircraft Handling Qualities, Pilot Induced Oscillations (PIO) problem, and develop diagnostic and reconfiguration flight control system. The second goal is using the stand for didactic purposes. There is a kind of flight simulator for students who make some "flying" experiments. The general scheme of the stand is shown in Figure 3. Take in Figure 3 Simulation process can be carrying out applying the real hardware flight computer (hardware in-the-loop simulation) or properties of the control system are modeled using PC. For didactic purposes the second method is employed. Take in Figure 4 & 5 Figure 4 presents flow diagram of the simulation process. From "test pilot" point of view the stand executes flight simulation for different properties flight control system. Results of simulation are observed as flight instrument indication on the PC monitor screen– see Figure 5. On the display the command for pilot are showed: HC – altitude, ΨC – heading, ϕC – bank angle and wC – vertical speed.

Simulation experiment The main task of experiment is evaluating handling qualities of aircraft equipped with different version of indirect control system. The "test pilot" is caring out a five-minutes instrument flight (IFR) according to command shown on the screen (see example in Figure 5 – inscription "PRZECHYLENIE -20" means "BANK ANGLE MINUS 20 DEGREES"). The example of flight plan is shown in Figure 6. Every flight was different and pilot has not known parameters of the flight plan; he/she should follow commands.

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Take in Figure 6 Handling Qualities of the simulated airplanes are evaluated by "test pilot" using Training Rate scale (TR) which was prepared in Department of Avionics and Control by T. Rogalski (Rogalski, 2004b). The idea of the TR scale is similar to well-known Cooper-Harper scale, but in our opinion, it is more intuitive and effortless for not experience pilots. The scheme of decision process is shown in Figure 7. Take in Figure 7 After every simulated flight pilot should fill on the TR forms, taking into consideration pilot decision algorithm. Every segment of flight is evaluated: horizontal flight, climbing, descending flight, and turns. General rating should summarize all handling qualities characteristics. Additionally two parameters of control process are evaluated: possibility of state stabilization precision, and arduousness of steering, according to evaluating scale presented in Table 1.

Table 1. Pilot rating scale for precision and arduousness of steering evaluation

Pilot rating

Flight parameters stabilization

Arduousness of steering

1

Very easy

Least arduousness

2

Easy

Less arduousness

3

Acceptable

Acceptable arduousness

4

Difficult

More arduousness

5

Very difficult

Most arduousness

Seven different control laws in longitudinal and lateral flight of the PZL-110 Koliber general aviation aircraft were verified in simulation experiments. The control laws were prepared for three levels of system operation:

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A. Emergency control – level III (Figure 8) 1.

Direct proportional control surface deflections (Figure 9, curve a) – equivalent of mechanical linkage,

2.

As No 1, with a dead band (∆UP) around the central (neutral) side-stick placement (Figure 9, curve b),

3.

As No 2, plus automatic trimmer (pitch moment equilibrium), B. Simplified control, forming filter is used – level II (Figure 8)

4.

As No 3, but nonlinear function was used (Figure 9, curve c),

5.

Forming filter described by Rogalski’s formula was used (Rogalski, 2006):

U MW

• ⎧ ⎫ • ⎪ f (U P ) + k ⋅ U P ⎪ ⎛ ⎞ = min ⎨ ⎬ ⋅ sign⎜ f (U P ) + k ⋅ U P ⎟ ⎝ ⎠ ⎪⎩ ⎪⎭ U P max

where:

⎛ UP f (U P ) = ⎜ ⎜ U P max ⎝

⎞ ⎟ ⎟ ⎠

2

UMW=δ – required displacement of aerodynamics control surface, UP – stick displacement, k – weight factor of side-stick rate of movement. Properties of forming filter are graphically presented by 3D-surface in Figure

9, surface d. C. Normal flight control system operation – level I (Figure 10)

6.

Indirect control "Rate Command / Attitude Hold" type (for kFF=0),

7.

As No 6, plus modification "Feed-Forward" type (for kFF≠0). Take in Figures 8, 9 & 10

The parameters of the control laws have been calculated for PZL-110 Koliber aircraft model (Cieciński, 2004) and verified by experienced flight instructors as acceptable for this kind of steering. Additionally, the parameters of the control laws were chosen in this way that 90% of full deflections of the stick have generated signals correspond with limited envelope of aircraft state.

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Pilot evaluation summary

Forty-five students of Machine Design and Aeronautics Faculty have taken part in the first flight simulation experiment. At the beginning, every pilot made training flight for familiarization with simulation stand and flight task, next they have executed 110 evaluated flights. Students have commercial pilots license, they had 160-270 hours of total flight time, 90-210 hours of pilot in command, and preliminary training in instrument rating flights. Take in Figures 11 &12

The results of the flight control evaluation for different versions (modes) of control laws are summarized in Figure 11. Figure 12 shows pilots' rating for typical segments of flight, and Figure 13 presents pilots' opinion about precision and arduousness of steering. In general, students experience as pilots of aircraft with classical (mechanical) control system had radical influence on the evaluation – the simple control laws were evaluated as acceptable. However, the flight control system No 7 (rate control / altitude hold plus feedforward loop) was estimated as the best one. In addition, this kind of controller lets pilot to more accurate control of plane with minimum of workload (Figure 12). Take in Figure 13

The flight simulator experiment was the preliminary evaluation of the indirect flight control system SPS-1A. The next simulation and flight tests are planned.

Final remarks

The experimental indirect flight control system SPS-1A was designed, built, and tested. All basic modules of the system were designed by research team, build and tested in laboratory conditions. The main properties of the control system are described by algorithms. The proposed control laws were tested during described flight simulation experiment before implementation on the board of the PZL-110 testbed aircraft.

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The special problem connected with indirect flight control system that should be analyzed is Pilot Induced Oscillations (PIO) phenomena. Results of using analytical criteria, which enable prediction of susceptibility oscillations of general aviation aircraft, simulation experiments and flight tests, have been presented in another papers (Rzucidło, 2006; Rzucidło, 2007). The next steps of this project were flight tests (Tomczyk, 2003; Tomczyk, 2004). During the first testing flight, the Level III mode of operation was tested (control law No 2). This version of aircraft has been found by pilots to be difficult to control. When the Level II mode of operation was used, with forming filter (control law No 5), pitch and bank angle stabilization was easier. Using the normal operation mode of the flight control system (Level I) causes that piloting is very easy because aircraft attitude is automatically stabilized; sidestick deflection is applied for the bank and pitch angle changing (control law No 7). The results of flight-testing confirm to flight simulation evaluation. However, flight tests are rather expensive and only the main properties of the flight control system were examined. The research team planes more sophisticated experiments using the modified flight simulator Alsim AL-200 MCC that is used for pilots training at Rzeszow University of Technology. We expect more precision evaluation control laws design for Socata TB-20 Trinidad, Piper Seneca II, and Beech King Air 200 aircraft. Additionally, the safety procedures can be tested. The experiments should show the role of human-aiding automation in creating singlecrew safety flights. This research will also aid the design of new types of pilot training and certification process because new piloting skills will be required.

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Acknowledgments

This paper was worked out within the framework of the project "Development of the Indirect Control System for Handling Qualities Shaping of General Aviation Aircraft" financed partly by The Polish State Committee for Scientific Research in the years 20032006.

References

Anon. (2006), EPATS - European Personal Air Transportation System, EU Project No FP62002-AERO-2-ASA6-CT-2006-044549, 2007-2008, Coordinator: Institute of Aviation, Warsaw (unpublished) Bost C., Mulder M., Passen van M.M. and Mulder J.A. (2006), "Path-Oriented Control/Display Augmentation for Perspective Flight-Path Displays", Journal of Guidance, Control, and Dynamics, vol. 29, No 3, pp. 780-791 Cieciński P. and Pieniążek J. (2004), "Aircraft model for flight control system synthesis", Mechanics in Aeronautics Conference, Polish Society of Theoretical and Applied Mechanics, pp. 287-300 (in Polish) Duerksen N. (2003), "Advanced Flight Controls and Pilot Displays for General Aviation", AIAA/ICAS International Air and Space Symposium and Exposition: The Next 100 Y, AIAA Paper No 2003-2647, Dayton, Ohio, 14-17 July 2003 Hodginson J. (1999), Aircraft Handling Qualities. AIAA Education Series, AIAA Inc., Reston, VA Holmes B.J., Durham M.H. and Tarry S. (2003) "Small Aircraft Transportation System Concept and Technologies", AIAA 2003-2510, AIAA/ICAS International Air and Space Symposium and Exposition: The Next 100 Y, Dayton, Ohio, 14-17 July 2003

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Kocks K. (2001) "Systems That Permit Everyone to Fly", Avionics Magazine, March 2001, pp. 16-20. Lam T.M., Mulder M., Passen van M.M. and Mulder J.A. (2006), "Comparison of Control and Display Augmentation for Perspective Flight-Path Displays", Journal of Guidance, Control, and Dynamics, vol. 29, No 4, pp. 564-578 Lambregts A.A. (2005), Fundamentals of FBW Augmented Manual Control, SAE-2005-013419, 24 pages Moore M.D. (2003) "Personel Air Vehicles: A Rural/Regional and Intra-urban On-demand Transportation System", AIAA/ICAS International Air and Space Symposium, 14-17 July 2003, Dayton, Ohio Moorhouse D.J. (Ed.) (2000), Flight Control Design – Best Practices. RTO-TR-029, NATO Mulder M., Veldhuijzen A.R., Passen van M.M. and Mulder J.A. (2005), "Integrating Fly-byWire Controls with Perspective Flight-Path Displays", Journal of Guidance, Control, and Dynamics, vol. 28, No 6, pp. 1263-1274 Pratt R.W. (Ed.) (2000), Flight Control Systems. Progress in Aeronautics and Astronautics, AIAA Inc., Reston, VA Rogalski T. (2004a), Modifications of selected operational characteristics of general aviation aircraft, PhD Thesis, Rzeszow University of Technology, Faculty of Mechanical Engineering and Aeronautics, (in Polish, unpublished) Rogalski T. and Dołęga B. (2004b), "The new conception of the laboratory testing of the FBW systems for small aircraft", Aircraft Engineering and Aerospace Technology; An International Journal, Emerald, Vol. 76, No 3, pp. 293-2982 Rogalski T. and Dołęga B. (2006), "Algorithms Improving Flying Qualities of General Aviation Aircraft", AVIATION, Vol. X, No 2, pp. 17-21

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Rzucidło P. (2006), "The Detection of Pilot Induced Oscillations", VII International Seminar on Recent Research and Design Progress in Aeronautical Engineering and its Influence on Education, Tallin, 11-12 October 2006 Rzucidło P. (2007), Pilot Induced Oscillations in Indirect Flight Control System, Rzeszów University of Technology Press, ISBN 978-83-7199-444-9 (in Polish) Steck J.E., Rokhsaz K. and Pesonen U. (2004), "Pilot Evaluation of an Adaptive Controller on General Aviation SATS Testbed Aircraft", AIAA 2004-5239, AIAA Guidance, Navigation, and Control Conference and Exhibit, 16-19 August 2004, Providence, Rhode Island Tomczyk A. (1998), "Concept for Simplified Control of General Aviation Aircraft", 1998 World Aviation Conference, Anaheim, CA, SAE/AIAA Paper No 985551, SAE 1988 Transactions, Journal of Aerospace, 1999, ISSN 0096-736X Tomczyk A. (2003), "Experimental Fly-by-Wire Control System for General Aviation Aircraft", AIAA Paper No 2003-5776, CD-ROM ISBN 1-56347-638-X Tomczyk A. (2004), "Facilitated airplane – Project and preliminary in-flight experiments", Aerospace Science and Technology, Elsevier, vol. 8, No 6, pp. 469-477 Tomczyk A. (2006), "Model-Following Method as a Useful Tool for Flight Indirect Control System Design", International Symposium on Generalized Solutions in Control Problems, Ulan-Ude, Russia, 5-8 July 2006 Tomczyk A. (2007), "Preliminary Evaluation of the Indirect Flight Control System for General Aviation Aircraft", AIAA Paper 2007-6526, AIAA Guidance, Navigation, and Control Conference and Exhibit, Hilton Head, SC, 20-23 August 2007 Webster F. and Smith T.D. (2001), Flying Qualities Flight Testing of Digital Flight Control Systems, RTO AGARDograph 300, vol. 21, NATO Wilson J.R. (2001), "Creating cars that fly", Aerospace America, AIAA, July 2001, pp. 52-61

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Figures Figure 1. General structure of the indirect flight control system SPS-1A

CAN1H

CAN2L

AHRS-F

CAN3L

Actuators

CC-1 Control Computer

RS AHRS-W1

AI AHRS-W Interface

AHRS-W2

CC-2 Control Computer

RS

CC-3 Control Computer

ADC-1

ADC-2

B

RS

EC Controller

EA Elevator Act.

AC Controller

AA Aileron Act.

RC Controller

RA Rudder Act.

TC Controller

TA Trimm Act.

PC Controller

PA Engine Act.

GNS-530

GPS-35

RS

CI Control Interface

A Other Measurem.

MC Maintenance Computer

SP Selector Panel

B

NI Navigation Interface

A

EC Engine Controller

USB - CAN

A

Flight Computers

Measurement Systems

SI Side-stick Interface

PWM

TI Throttle Lever Interface

ML

A – analog signal B – binary signal RS – RS232 bus

PWM – Pulse Duration Modulation ML – mechanical linkage

Pilot Interfaces

Figure 2. Simplified diagram of model-following aircraft control FF PILOT

UP

UPF FC

δD AR

∆Y MoIA

YM

YC

δ

A/C

N C

HAS

17

X

ME

Y

Figure. 3. The computer based stand for indirect flight control system testing PC for aircraft modeling and user interface

1

PC for flight simulation and data storage

Flight computer of the indirect control system

3

2 Hardware in the loop simulation

Sidestick and control panel

Figure 4. Block-scheme of the simulation process: Y – aircraft flight parameters vector, N – disturbances (air turbulence, for example)

PILOT

DISPLAY ϑ, ϕ, ψ H, w, V HC, ψC, ϕC, wC

RECORDING

•

INDIRECT FLIGHT CONTROL SYSTEM

SIDE-STICK (CONTROL)

Up

FORMING FILTER

UN

UMW CONTROLLER

ACTUATORS MODEL

δ

AIRCRAFT MODEL N

Y

18

X

MEASUREMENT SYSTEMS MODEL

•

Y

Figure 5. Simulated instrument panel on the PC monitor

Command Display

Figure 6. Trajectory and vertical profile of the simulated flight (an example) w = –3 m/s

4

5

3

H [m]

w = –3 m/s

1050

w = –3 m/s

1000 w = +2 m/s

w = +2 m/s

2

7

w = 0 m/s

8

1

w = –3 m/s

6

w = +2 m/s

950 1

w = 0 m/s

2

3

6

7

8

9

10 11 12 time points of trajectory

Ψ [0]

w = +2 m/s 180

10

Flight time – 5 min

5

Vertical speed and altitude commands

9

START

Horizontal plan of the flight

4

0

11 w = 0 m/s

12

φ = –200

φ = –200

φ = 200

φ = 30

90

φ = 200

0 1

2

3

4

5

6

7

8

9

10 11 12 time points of trajectory

Bank angle and heading commands

19

Figure 7. Decision algorithm for Training Rate scale (TR)

Is it possible to orient the plane at demanded plane’s space orientation?

YES

NO

5 very poor

Practically is impossible to control the flight. It is impossible to realize another flight task then keeping the plane in flight. Controlling the plane needs a big number of movements with the control device and their amplitude is also big.

Flight stabilization doesn’t need much effort from pilot?

NO

4 poor

Keeping demanded plane space orientation is possible but it requires rather bigger pilot’s effort. Extensive pilot compensation is required.

YES

Is it possible to accurately control the flight near the selected steady state?

YES

1 very good

3 acceptable

It is possible to catch and keep demanded plane space orientation. Desired performance don’t required pilot compensation. But both very accurate and too dynamical control can result in lost control..

Does dynamical pilot’s action brings equivalently dynamical plane response?

YES

NO

NO

2 good

It is possible to accurately control the plane flight near the selected flight steady state. Dynamical action with control device brings adequate dynamical plane response

All plane responses to pilot’s actions are adequate to his intentions. All kinds of maneuvers are available

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Figure 8. Simplified flight control system block-scheme (level II & III)

PILOT

uP

Forming Filter

uMW

Actuator

δ

Aircraft

X

Figure 9. Forming filter functions No 1-5

d UMW

a

∆UP UMW UP

c b

dUP/dt

UP

Figure 10. Rate Command / Attitude Hold Control Algorithm (pitch channel example)

PILOT

uP

•

TFFs TFFs + 1

kFF K Θ ΘD + s

Flight Computer

Θ

∆Θ −

q

uPF

Control Algorithms +

+

uMW

Actuator

δH

Aircraft

X• •

21

Figure 11. Training Rate evaluation (TR)

5

Mean value of rating

Training Rate Scale [TR]

4.5

RMS of rating

4

3.5

3

2.5

2

1.5

1

0.5

0

1

2

3

4

5

6

7

Number of control laws

Figure 12. Evaluation of flight segments: A -horizontal flight, B - climbing, C - descending flight, D – turns 3.5

3

2.5

2

1.5

1

0.5

0

1 2 3 14 5 6 7

A

1 2 3 24 5 6 7

B

1 2 3 34 5 6 7

C

22

1 2 3 44 5 6 7

D

Figure 13. Evaluation of precision (P) and arduousness (A) of steering 3

2.5

2

1.5

1

0.5

0

1

2

1 2 3 4 5 6 7

1 2 3 4 5 6 7

P

A

23