Imon Chakraborty

Vehicle posture control through aggressive maneuvering for mitigation of T-bone collisions

This work analyzes the mitigation of unavoidable T-bone collisions between two automobiles through the execution of an aggressive maneuver involving a rapid yaw rotation of one of the vehicles, in order to achieve a favorable vehicle posture prior to the collision. The maneuvering vehicle is assumed to possess torque vectoring technology at the rear wheels, allowing the generation of a direct yawing moment. The maneuver is posed as an optimal control problem, whose numerical solution yields the optimal control strategy. Several conditions involving a variety of speeds and friction coefficients are investigated.

Electric Control Surface Actuator Design Optimization and Allocation for the More Electric Aircraft

This work pertains to the optimization of electric actuators for the primary and secondary flight control surfaces of a More Electric Aircraft. Electrohydrostatic and electromechanical actuators are considered and optimized in accordance with the flight loads and actuator requirements identified in a separate work by the same authors. For the purposes of this work, the Boeing 737-800 aircraft is chosen as a test case. However the methodology is general and can be applied to any existing design or proposed design concept. Once the optimized actuator designs are obtained, the possibility of using both actuator types by allocating them to control surfaces on the basis of reliability requirements is considered.

An integrated approach to vehicle and subsystem sizing and analysis for novel subsystem architectures

The aerospace industry is currently transitioning to More Electric subsystem architectures due to steadily improving electric technologies and the technology saturation of established conventional architectures. For aircraft with such unconventional architectures, the lack of historical information and the presence of increased inter-subsystem interactions create a significant design challenge. These necessitate a greater focus on subsystems design earlier in the design process than typically seen for aircraft with conventional subsystem architectures. At the same time, however, to be suitable for the early design phases, the subsystem analyses must be computationally inexpensive and not require detailed aircraft definition. This work presents an integrated, modular, and tool-independent approach to the sizing and performance analysis of the aircraft and its subsystems, in which inter-dependencies are established between relevant aircraft and subsystem level parameters. The approach allows the assessment of subsystem architectures using vehicle and mission level metrics for a fixed vehicle design, and also the amplified effect of re-sizing the vehicle in accordance with a pre-defined rule-set. The proposed approach was demonstrated through a comparative assessment of a predominantly electric subsystem architecture and a conventional one for a representative single-aisle aircraft. In this assessment, the impacts of changing the form of secondary power extraction, the change in vehicle empty weight, and re-sizing of the vehicle were successively identified.

A methodology for vehicle and mission level comparison of More Electric Aircraft subsystem solutions: Application to the flight control actuation system

As part of the More Electric Initiative, there is a significant interest in designing energy-optimized More Electric Aircraft, where electric power meets all non-propulsive power requirements. To achieve this goal, the aircraft subsystems must be analyzed much earlier than in the traditional design process. This means that the designer must be able to compare competing subsystem solutions with only limited knowledge regarding aircraft geometry and other design characteristics. The methodology presented in this work allows such tradeoffs to be performed and is driven by subsystem requirements definition, component modeling and simulation, identification of critical or constraining flight conditions, and evaluation of competing architectures at the vehicle and mission level. The methodology is applied to the flight control actuation system, where electric control surface actuators are likely to replace conventional centralized hydraulics in future More Electric Aircraft. While the potential benefits of electric actuation are generally accepted, there is considerable debate regarding the most suitable electric actuator – electrohydrostatic or electromechanical. These two actuator types form the basis of the competing solutions analyzed in this work, which focuses on a small narrowbody aircraft such as the Boeing 737-800. The competing architectures are compared at both the vehicle and mission levels, using as metrics subsystem weight and mission fuel burn, respectively. As shown in this work, the use of this methodology aids the decision-making process by allowing the designer to rapidly evaluate the significance of any performance advantage between the competing solutions.

Development of a Sizing and Analysis Tool for Electrohydrostatic and Electromechanical Actuators for the More Electric Aircraft

This work documents the development of a MATLAB/Simulink based methodology for the sizing, simulation, analysis, and optimization of electric actuators for the primary and secondary control surfaces of a More Electric Aircraft. For a given aircraft and control surface configuration, the control surface flight loads are first evaluated taking into account their aerodynamic characteristics and the critical flight conditions relevant to each. With this information, the performance of a given actuator design can be analyzed via a simulation of the actuator and thermal dynamics. Conversely, for a given objective function and constraint set, the actuator design can be optimized through the solution of a constrained optimization problem. This work focuses on the development of the flight load estimation capability, the modeling and simulation environment, and the weight estimation method, while a separate work describes the actuator optimization problem and a study of actuator-to-surface allocation. While applicable to a wide variety of aircraft, the current work analyzes electrohydrostatic and electromechanical actuators using the Boeing 737-800 aircraft as a test case.

Multidisciplinary Design Optimization of a Truss Braced Wing Aircraft

†‡ § ¶ This paper focuses on establishing the po tential benefits of a truss-braced wing aircraft configuration as compared to the current generation cantilever wing aircraft, as well as a strut-braced wing. Mu ltidisciplinary Design Optimization is used to design aircraft with three diffe rent wing configurations with increasing complexity of structural topology: cantilever, 1-member truss (strut) and 3-member truss. Three different objective functions are studied: minimum takeoff gross weight, minimum fuel consumption and emissions, and maximum lift to drag ratio. The results show the significant advantage of strut and simple truss configurations over the conventional cantilever configuration. They also indicate that a truss-braced wing has a greater potential for improved aerodynamic performance than has been reported for other innovative aircraft configurations. In addition, the comparison between the various design objective functions shed light on their effect on the resulting configurat ions. Some initial aeroelastic analyses are then presented and discussed. Further studies will consider the inclusion of more complex truss topologies and other innovative technologies which are judged to be synergistic with truss-braced wing configurations.

Assessment of Electrically Actuated Redundant Control Surface Layouts for a Hybrid Wing Body Concept

Hybrid Wing Body configurations are currently an active field of research as potential candidates to meet NASA ERA N+2 goals. One characteristic of these configurations is the presence of a large number of redundant flight control surfaces. However, the design process and decision rationale for a given control surface layout is rarely discussed in the open literature. This paper investigates tradeoffs between drag, control authority, actuator weight, and actuation power requirements as a function of the number and spacing of elevons. The actuators will be sized based on hinge moments measured during nominal and failed control trim analyses. These effects are propagated upwards to estimate changes to fuel burn, a system level metric important to the ERA program, via the Breguet range equation. A model of the N2A-EXTE will be used to demonstrate these tradeoffs.

Time-optimal vehicle posture control to mitigate unavoidable collisions using conventional control inputs

This paper analyzes the mitigation of an unavoidable T-bone collision, where an “intelligent” vehicle executes an aggressive time-optimal rotation to achieve a favorable relative orientation with another vehicle prior to impact. The current paper extends the previous work by the authors on this problem, by modeling additional vehicle dynamics (neglected in the prior work) and by utilizing conventionally available control commands (that is, steering, braking, handbrake) for the maneuvering vehicle. The commands can either be applied directly by a trained driver, or (as in the majority of cases) can be executed with the help of a combination of an Active Front Steering (AFS) and an Electronic Stability Control (ESC) system onboard the vehicle. The optimal yaw rotation maneuver is analyzed for different initial speeds on both dry and wet asphalt. The results confirm the existence of an “option zone” for some cases, within which such an aggressive maneuver may be possible and perhaps even preferable to straight line braking.

Multidisciplinary Approach to Assessing Actuation Power of a Hybrid Wing–Body

Hybrid wing–body configurations, such as the N2A-EXTE, have the potential to meet NASA Environmentally Responsible Aviation N+2 goals. These configurations have redundant elevons typically spanning the entire trailing edge of the wing, for which the large areas result in the generation of large hinge moments. To ensure aircraft stability with a reduced static margin, high control surface deflection rates may also be required. The combination of large actuation loads and rates results in significant actuation power requirements, which affect both fuel burn and the sizing of the actuation subsystem. In the early design phases, there is significant uncertainty regarding the magnitude of the actuation power, which may depend on the vehicle’s static margin, the design and designated roles of the redundant control surfaces, actuator design parameters, and the intensity of encountered atmospheric turbulence. The objective of this paper is to present a methodical approach for assessing this uncertainty and relati...

Method for Evaluating Electrically Actuated Hybrid Wing–Body Control Surface Layouts

Hybrid wing–body configurations are currently an active field of research as potential candidates to meet NASA Environmentally Responsible Aviation N+2 goals. One characteristic of these configurations is the presence of a large number of redundant flight control surfaces. However, the design process and decision rationale for a given control surface layout is rarely discussed in the open literature. This work investigated tradeoffs between drag, control authority, actuator weight, and actuation power requirements as a function of the number and spacing of elevons. The actuators were sized based on hinge moments computed during nominal and failed control flight conditions. These effects were propagated upward to estimate changes to fuel burn, a system-level metric important to the Environmentally Responsible Aviation program, via the Breguet range equation. A model of the NASA N2A-EXTE hybrid wing–body configuration concept was used to demonstrate these tradeoffs. The study concluded that adjacent elevons...