Aircraft Engineering and Aerospace Technology

An almost disturbance decoupling solution of the attitude control problem : Table of Contents

R. Özgür Doruk, Erol Kocaoglan — Sun May 11 14:15:06 BST 2008

Abstract:
Purpose The purpose of this paper is to derive a robust nonlinear attitude control law intended for practical application. Design/methodology/approach The method of input/output feedback linearization is utilized for having a linear model and a recently developed almost disturbance decoupling (ADD) approach is adopted for designing a robust satellite attitude control (SAC) system. The kinematics of the satellite is modeled by modified Rodriguez parameters because of their continuous invertibility. The design is simulated on the model of a realistic satellite project (BILSAT-I), which is developed by the Turkish Scientific and Technological Research Council. Findings The torque requirement of the operation does not exceed the maximum limit provided by the actuator. The square error levels are staying under the boundary of final global attractor, which is one of the important proofs for the successful operation of the generated ADD control law. Originality/value The ADD concept is investigated on SAC problem. By that way, simple control structures with known disturbance attenuation capability can be designed.

On the predicted errors of atmospheric guidance laws : Table of Contents

S.H. Jalali-Naini, S.H. Pourtakdoust — Sun May 11 14:15:06 BST 2008

Abstract:
Purpose The purpose of this paper is to develop a novel solution for the predicted error and introduces a systematic method to develop optimal and explicit guidance strategies for different missions. Design/methodology/approach The predicted error is derived from its basic definition through analytical dynamics. The relations are developed for two classes of systems. First, for systems in which the acceleration commands are truncated at a specified time. Second, for systems in which the corrective maneuvers are cut off at a specified time. The predicted error differential equation is obtained in a way that allows for derivation of several optimal and explicit guidance schemes. Findings The effect of tangential acceleration in conjunction with autopilot dynamics can be realized in guidance gain and the predicted error. The differential equation of velocity-to-be-gained is obtained assuming the gravitational acceleration to be given as a vectorial function of time. The relations for different velocity profiles are obtained and discussed including the effective navigation ratio. Research limitations/implications The guidance/control system is modeled as a linear time-varying dynamic and of arbitrary-order. The gravitational acceleration is assumed as a given vectorial function of time. Practical implications The presented schemes are applicable to both midcourse and terminal guidance laws with/without velocity constraints. Originality/value Providing a new analytical solution of predicted errors with final position and velocity constraints and their differential equations considering the thrust/drag acceleration and autopilot dynamics in the presence of gravity.

The robust adaptive attitude control of a certain satellite : Table of Contents

Xin-long Chen, Di Yang — Sun May 11 14:15:06 BST 2008

Abstract:
Purpose The purpose of this paper is to examine the attitude control problem of a certain and big flexible satellite with unmodeled dynamics and unknown bounded disturbances and control input saturation; and to present a design method of robust adaptive controllers (RACs). Design/methodology/approach First, using the Lyapunov stability theory, it is shown that the proposed adaptive controller can guarantee the stability of the nonlinear system. Then, the parameters regulation method of the RAC is introduced. Finally, an RAC is designed for the object satellite model consisted of all the error-source models. Findings The simulation results are compared with other results that are derived by using the typical PID controller. It is proved that the designed RAC has some properties of quickly response, high steady-state precision and strong robustness. Originality/value The paper is of value in presenting a design method of RACs aiming at the object satellite with uncertainties and control input saturation.

Proposal of the experimental simulation method for handling qualities evaluation : Table of Contents

Andrzej Tomczyk — Sun May 11 14:15:06 BST 2008

Abstract:
Purpose The purpose of this paper is to present analysis and primary evaluation of different control laws implemented on experimental indirect (fly-by-wire) flight control system designed for perspective general aviation aircraft. Design/methodology/approach 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 2-4 five min 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 45 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/value 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.

Low-cost flight test system for light aircrafts : Table of Contents

Paulo Iscold — Sun May 11 14:15:06 BST 2008

Abstract:
Purpose The purpose of this paper is to present the research efforts of the Center of Aeronautical Studies of the Federal University of Minas Gerais Brazil to develop a low-cost flight test data acquisition system for light aircraft and unmanned aerial vehicles (UAEs). Design/methodology/approach The development of this system was based on a microcontroller, chosen in accordance with main requirements of light aircrafts flight tests. The system uses the microcontroller in order to communicate with different kinds of sensors, including a GPS, and organize this information to be sent to a PDA device, which is used to control the acquisition process and storage the data acquired. Details about the development of this system, including firmware algorithm and sensors development, are presented and discussed in the paper. Findings The paper presents example results obtained with this system in applications such as performance evaluation and stability and control derivatives estimation problems. Take into account all the aspects of the system and the quality of the results, the main conclusion is that this system can efficiently support the demands of the aerospace industry for light aircraft and UAEs development programs as well as the necessities of the research centers and universities developing aeronautical research and didactic programs. Practical implications Recently, results confirm the applicability of this system in order to perform flight tests of aircrafts in accordance with FAR-Part 23 or CS-VLA or Light Sport Aircrafts as required by FAA Order 8130.2F and ASTM Designation F2245-04. Originality/value This paper presents details about the construction of a low-cost data acquisition system for flight tests of light aircrafts. The main advantage of this system is the use of a PDA device in order to control and storage the acquisition, which reduce costs, weight and size of the system and permits its installation in light aircrafts or UAVs.

The training rate of aircraft handling quality evaluation scale : Table of Contents

Boguslaw Dolega, Tomasz Rogalski — Sun May 11 14:15:06 BST 2008

Abstract:
Purpose The purpose of this paper is to present the sample result of researches under original conception of the aircraft handling qualities evaluation scale. It allows rating and comparing of different control algorithms implemented into the control system in the simple way. Design/methodology/approach The presented handling qualities evaluation scale takes into consideration two main elements to generate the grade of the tested control law. These are: pilot's workload during typical flight phases and the second is precision of control the pilot reaches controlling the plane. Findings The paper presents possibilities of using of the proposed methodology. Also contributions of its use are described. Practical implications The presented methodology can be applied to evaluate and compare handling qualities of different control algorithms supporting pilots. Originality/value This paper presents original conception of handling qualities evaluation scale for aircraft equipped with fly-by-wire control system.

Recuperated gas turbine aeroengines, part II: engine design studies following early development testing : Table of Contents

Colin F. McDonald, Aristide F. Massardo, Colin Rodgers, Aubrey Stone — Sun May 11 14:15:06 BST 2008

Abstract:
Purpose To advance the design of heat exchanged gas turbine propulsion aeroengines utilising experience gained from early development testing, and based on technologies prevailing in the 1970-2000 time frame. Design/methodology/approach With emphasis on recuperated helicopter turboshaft engines, particularly in the 1,000 hp (746?kW) class, detailed performance analyses, parametric trade-off studies, and overall power plant layouts, based on state-of-the-art turbomachinery component efficiencies and high-temperature heat exchanger technologies, were undertaken for several engine configuration concepts. Findings Using optimised cycle parameters, and the selection of a light weight tubular heat exchanger concept, an attractive engine architecture was established in which the recuperator was fully integrated with the engine structure. This resulted in a reduced overall engine weight and lower specific fuel consumption, and represented a significant advancement in technology from the modified simple-cycle engines tested in the late 1960s. Practical implications While heat exchanged engine technology advancements were projected, there were essentially two major factors that essentially negated the continued study and development of recuperated aeroengines, namely again as mentioned in Part I, the reduced fuel consumption was not regarded as an important economic factor in an era of low-fuel cost, and more importantly in this time frame very significant simple-cycle engine performance advancements were made with the use of significantly higher pressure ratios and increased turbine inlet temperatures. Simply stated, recuperated variants could not compete with such a rapidly moving target. Originality/value Establishing an engine design concept in which the recuperator was an integral part of the engine structure to minimise the overall power plant weight was regarded as a technical achievement. Such an approach, together with the emergence of lighter weight recuperators of assured structural integrity, would find acceptance around the year 2000 when there was renewed interest in the use of more efficient heat exchanged variants towards the future goal of establishing greener aeroengines, and this is discussed in Part III of this paper.