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This paper presents a Control Allocation formulation aimed at altering the dynamic transient response of an aircraft by exclusive means of the aerodynamic effectiveness of its control effectors. This is done, for a given Flight Control System architecture and, optionally, closed-loop performance, by exploiting the concept of Control Center of Press...
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... which is able to operate consistently with different levels of input fidelity. Thanks to ts capability to support automatic aircraft design workflows, PHALANX has been used in a number of research studies and applications on different aircraft configurations [8][9][10][28][29][30][31]. A block-scheme overview of the toolbox is shown in Fig. ...
Citations
... The activities planned and conducted within the PARSI-FAL project involved multidisciplinary and interconnected aspects, such as the structural analysis of the box-wing system [42][43][44][45], its aeromechanical features [46][47][48], the integration of systems [49], the assessment of its environmental impact [50], and of course its aerodynamic analysis, which is the topic of this paper. ...
This article presents a detailed aerodynamic investigation on a transport aircraft with a box-wing lifting system. The aerodynamic development of this configuration is presented through the description of the collaborative and multi-fidelity design approach that took place within PARSIFAL, an European project aiming to develop the box-wing configuration for a civil transonic aircraft. The article starts from an accurate description of the collaborative methodological framework employed and offers an overview of the development of the box-wing aerodynamics together with the highlight on its most significant characteristics and aerodynamic features identified. The design development is detailed step by step, with specific focus on the challenges faced, starting from the conceptual investigations up to the most advanced evaluations. Significant focus is given to the assessment of the aerodynamic performance in transonic flight for the box-wing lifting system, and to the design solutions provided to overcome issues related to this flight regime, such as drag rise and flow separation. In addition, the high-fidelity shape optimisation techniques employed in the advanced stage of the design process are detailed; these allow to define a final configuration with improved aerodynamic performance.
... The toolbox has been developed in-house in MATLAB, using the Simulink and Simscape multi-body dynamics packages. It has already been implemented in several other research applications to unconventional aircraft configurations [27,28], including studies on the propulsive empennage concept [29], and the trim and transient response of staggered box-wing aircraft [30,31]. A top-level overview of the PHALANX flight simulation toolbox is shown in Figure 6. ...
... This flexibility should be exploited to improve the flying and handling qualities characteristics of the aircraft. Redundant CSs can be coordinated to increase safety in case of failure, actively control the aerodynamic load over the wing, and allow innovative techniques in maneuvering flight, such as direct lift control [20][21][22]. A possible way to do so is through the employment of Control Allocation (CA) methods. ...
... The toolbox has been used in several previous studies on novel aircraft configurations like the Blended Wing Body [36], the Delft University Unconventional Configuration, featuring the propulsive empennage concept [37], and other box-wing aircraft [20,21,38]. An overview diagram of PHALANX is shown in Figure 3. ...
... Differential braking is chosen in this paper. The CA method can be expressed as follows [26][27][28][29]: ...
The antidisturbance control problem of autonomous vehicle path tracking considering lateral stability is studied in this paper. This paper proposes an improved active disturbance rejection control (IADRC) control method including an improved extended state observer (IESO) and an error compensator based on LQR, where a new continuous nonlinear function is proposed in the IESO instead of the classical piecewise function. Based on the IADRC, an autonomous vehicle path-tracking controller considering lateral stability is designed. Using the output wheel steering angle and external yaw moment, the IESO estimates the disturbance value and compensates for the disturbance in the feedback to meet the goal of antidisturbance control. Based on the concept of control allocation (CA), the control distributor is designed to distribute the external yaw moment to the four wheels in a reasonable and optimal way to achieve differential braking. Finally, the control scheme is evaluated in the form of CarSim/Simulink cosimulation; the results show that the proposed autonomous vehicle path-tracking control scheme has better path-tracking effect and higher antidisturbance robustness.
... Parts of this chapter have been published in the Aerospace Science and Technology journal in 2021 [172]. 7 134 7. TRANSIENT DYNAMIC RESPONSE After the following Section 7.1 briefly recaps the most relevant DLC concepts, first introduced in Chapter 1, Section 7.2 goes into more detail on the employed FCS architecture, as well as on the procedure implemented to tune it. ...
The objective of the present dissertation is to show how redundant control surfaces can be exploited to shape an aircraft dynamic behavior and obtain desired flight mechanics performance. This is achieved by introducing novel approaches and methods for flight mechanics and control, mainly revolving around original implementations of traditional formulations of the Control Allocation (CA) problem. Control surfaces and, more in general, control effectors are defined as redundant if they are capable to independently control the same motion axis of the aircraft.
Redundant effectors can be linked together, and to the pilot input, in many ways according to different optimality criteria and/or performance objectives. In particular, the research presented in this dissertation focuses on the possibility to achieve Direct Lift Control (DLC). The latter is intended as the ability to use control effectors to alter the aircraft lift "without, or largely without, significant change in the aircraft incidence, and ideally is meant not to generate pitching moment."
The ability to do so is essentially dependent on the position of the Control Center of Pressure (CCoP), which is the center of pressure of aerodynamic forces solely due to control surface deflections. In case of a single control surface dedicated to DLC, the CCoP coincides with the control surface itself. In case of redundant control surfaces, their deflections can be coordinated to induce the position of the CCoP towards some preferred location, as allowed by the architecture of the aircraft and the available control effectiveness.
The first three chapters of the dissertation are dedicated to establishing the societal, scientific, and technical background underlying the subsequent research studies, including an overview of the CA problem for redundant control effectors. The following four chapters present, in this order: an evaluation of the mission performance of a staggered box-wing aircraft model designed for commercial transonic operations; a comparison of different CA methods on the design of an optimum control surface layout for a box-wing aircraft, with control surface both fore and aft the aircraft center of gravity; a trim problem formulation which employs forces and moments due to the aircraft control surfaces as decision variables, to maximize control authority, minimize aerodynamic drag or obtain a prescribed pitch angle; a CA-based formulation aimed at altering the characteristics of the transient response of an aircraft by exploiting the properties of the CCoP.
The conclusive chapter presents a comprehensive, top-level recap of the main aspects and topics covered within the dissertation. It reflects on the classic meaning of DLC, and what it means to achieve it with redundant control surfaces that are not expressly dedicated to it. With some considerations on the needs of aviation market, it speculates on the practical role of unconventional aircraft configurations in the near future. Lastly, it provides suggestions for improvements and future research studies.
... The box-wing has been known for a long time to be the "best wing system" for induced drag performance [15], and the PrP concept strives to integrate it in an innovative aircraft architecture for sustainable future aviation. The double wing system of the PrP allows the installation of multiple control effectors, which poses an interesting design challenge, and at the same time enables innovative control possibilities like DLC [29]. With control surfaces on the both the front and rear wings, the PrP is capable to generate substantial variations in lift, while decoupling, partially or totally, the control of pitch moment from the one of vertical forces. ...
... The toolbox has been used in the past for the Flight Mechanics analysis of the PrP [5,29], its mission performance evaluation [6], and the sizing of control surfaces on its box-wing geometry [18,19]. PHALANX has also been employed in the analysis of different novel aircraft configurations like the BWB [20] and the Delft University Unconventional Configuration (DUUC), featuring the propulsive empennage concept [21]. ...
This paper presents a generic trim problem formulation, in the form of a constrained optimization problem, which employs forces and moments due to the aircraft control surfaces as decision variables. The geometry of the Attainable Moment Set (AMS), i.e. the set of all control forces and moments attainable by the control surfaces, is used to define linear equality and inequality constraints for the control forces decision variables. Trim control forces and moments are mapped to control surface deflections at every solver iteration through a linear programming formulation of the direct Control Allocation algorithm. The methodology is applied to an innovative box-wing aircraft configuration with redundant control surfaces, which can partially decouple lift and pitch control, and allow direct lift control. Novel trim applications are presented to maximize control authority about the lift and pitch axes, and a "balanced" control authority. The latter can be intended as equivalent to the classic concept of minimum control effort. Control authority is defined on the basis of control forces and moments, and interpreted geometrically as a distance within the AMS. Results show that the method is able to capitalize on the angle of attack or the throttle setting to obtain the control surfaces deflections which maximize control authority in the assigned direction. More conventional trim applications for minimum total drag and for assigned angle of elevation are also explored.
This article studies the control problem of autonomous vehicle path following with coordination of active front steering and differential steering. A hierarchical control scheme including upper layer and lower layer is proposed. In the upper layer controller, a linear quadratic regulator based on extended state observer is proposed to generate the front-wheel steering angle and external yaw moment, where extended state observer is used to estimate and compensate for the system uncertainty and external disturbance which enhances the capability of the vehicle to suppress the disturbance. A brake force distribution scheme based on the theory of control allocation is proposed in the lower layer controller to optimize and coordinate each wheel brake force to achieve differential steering. Finally, the effectiveness of proposed control scheme is verified in a co-simulation platform based on CarSim/Simulink; it can be concluded that the linear quadratic regulator based on extended state observer scheme not only has a few parameters need to be tuned, but also has the capability of active disturbance rejection.
