Research progress of the most popular deformable a

Research progress of deformable aircraft in the United States

in order to effectively complete specific flight missions, aviation researchers usually design aircraft with different aerodynamic layouts and types according to different flight conditions, forming the current aircraft family, such as fighter planes that emphasize speed and agility; Transport aircraft pursuing cruise economy; Reconnaissance aircraft that can stay in the air for a long time. There are many supporting equipment for the design, manufacture and maintenance of various types of aircraft, which makes the aviation flight cost very high. For this reason, many government organizations and scientific research institutes in developed countries such as Europe and the United States are conducting technical research that can significantly reduce aircraft manufacturing and operating costs. These technologies will enable aircraft to more effectively complete different flight missions under different flight conditions. For example, in military affairs, the common air combat and reconnaissance tasks are usually completed by two different types of aircraft due to the different performance requirements of the two tasks. In order to complete reconnaissance and strike missions more effectively at the first time, the US Defense advance research agency (DARPA) is actively committed to the research of morphing aircraft

deformable body technology is an advanced technology that allows aircraft to reconstruct its layout in flight. Aircraft with such technology can perform two or more incompatible tasks with their respective optimal layout. The military application prospect of deformable aircraft makes it one of the key research projects funded by the U.S. Defense pre research agency

development profile of deformable body aircraft

deformable body is not a new concept in a broad sense. In 1903, Wright brothers tried to control the aircraft by twisting the wings; At present, the widely used leading-edge slats, trailing edge flaps, brake resistance plates, landing gear retraction, and some variable swept wing aircraft (such as MiG-23, fb-111, etc.) can be regarded as the specific application of the early deformable body technology of the generalized concept

in the 1980s, the aircraft morphing program of NASA Langley Research Center and Dryden Flight Research Center was one of the earlier programs for morphing aircraft research. NASA first developed flexible composite "adaptive wing" with Boeing, and then cooperated with Rockwell to carry out "active flexible wing" (AFW) research. In 1996, NASA, Air Force Research Laboratory (AFRL) and Boeing jointly launched the "Active Aeroelastic Wing program" (AAW). On this basis, the defense advance research agency of the United States, together with the air force research laboratory and NASA, launched the "smart wing program" (SWP)

at present, the deformable aircraft structure (MAS) program in the charge of Dr. Terry weisshaar of the U.S. Defense pre research agency is a real research on deformable aircraft based on the results of the above research programs. Its purpose is to integrate, demonstrate and verify some technologies of deformable aircraft, and provide an advanced aircraft for completing a variety of incompatible complex military tasks in the future. There are two important reasons why the defense advanced research agency of the United States attaches importance to the variant aircraft project: first, it has a good economy; Multi mission aircraft; Second, improve flight performance. Europe is also actively engaged in the research of deformable body technology. The Active Aeroelastic aircraft structure (AAAS) project of the European Commission (EC) is to develop and evaluate the design concepts of improving aircraft efficiency through aeroelastic deformation of aircraft structure. These concepts will improve the flight efficiency of aircraft under different flight conditions and loading conditions by optimizing and adjusting aircraft configuration. An important part of the project is to study new intelligent materials and develop new actuation systems to verify their effectiveness and feasibility

to sum up the application scope and functional characteristics of metal tensile testing machine, the current foreign deformed body technology research mainly expects the aircraft with this technology to make a difference in the following four aspects:

(1) improve aircraft performance, expand flight envelope, and have the ability to perform multiple tasks

(2) replace the traditional flight control surface to improve stealth and flight performance

(3) reduce resistance and increase range

(4) reduce vibration or control flutter

main layout scheme of deformable aircraft in the United States

some indicators of deformation ability of deformable aircraft by the U.S. Defense pre research agency are: (1) wing sweep angle changes by 20 °; (2) The aspect ratio changes by 200%; (3) The wing area changes by 50%

the U.S. Defense pre research agency's deformed aircraft structure program has carried out a series of concept verification projects, with major partners including Boeing, Lockheed Martin, Raytheon missile systems and NextGen aeronautics. Many university research institutions have also participated in the research of deformation adaptive structures, materials, actuators and other subsystems, such as Payne State University, University of Notre Dame, Georgia Institute of technology and so on

at present, the main representative Concept Schemes of deformable body aircraft in the United States are as follows:

(1) Lockheed Martin's folding "Z" wing scheme. According to the needs of the flight mission at that time, the wings can be folded into different "Z" shapes

(2) Lockheed Martin's cormorant program. The program is designed for the development of a multi-purpose UAV, which can be launched and recovered from submarines. The changing shape of cormorant bird wings is used for reference

(3) Boeing's connecting wing scheme. Boeing first developed the connecting wing scheme by wolkovitch and applied for a patent. On this basis, Garrett continued to study and develop the sliding deformable connecting wing scheme and obtained two patents. This scheme can better meet the index requirements of the national defense pre research agency for deformable aircraft

(4) n-mas scheme of next generation airlines. The wing of this scheme can slide and expand into five attitudes to meet the flight requirements of hovering, cruising, climbing, high lift and high-speed maneuvering

deformable body aircraft test research and key technologies

after long-term research on deformable body technology and concept scheme, at present, the structural plan of deformable body aircraft of the U.S. Defense pre research agency mainly includes Lockheed Martin's folded "Z" wing scheme and the next generation airline's n-mas scheme. It has entered the model wind tunnel test and model freedom

Lockheed Martin's folded "Z" wing scheme after qualitative quality evaluation After the full-scale sub component test and integrated component test, the test was carried out in NASA TDT (transonic dynamics wind tunnel). In addition to wind tunnel tests, the n-mas program of the next generation airlines also designed a 45.4kg remote control free flight model mfx-1 (deformable flight test vehicle 1) powered by jet engines, and conducted free flight model tests. The main purpose of wind tunnel test is to verify the impact of system integration on aerodynamic load changes, which mainly includes three aspects:

(1) in a similar flight environment, with a continuous and repeatable model attitude, high dimensional accuracy and excellent dimensional stability change mode, verify the ability of deformation system and technology specific functions under aerodynamic action

(2) obtain test data and verify the analysis and estimation method

(3) explore model design and wind tunnel test technology

the development of deformable body aircraft involves the innovation and engineering application of various disciplines and technologies. The aerodynamics of deformable body, attitude control, replacing 50% of e-commerce packaging materials with 100% degradable green packaging materials/structures/processes, new actuators, etc. need to be studied. The main key technologies are as follows:

(1) prediction and aerodynamic mechanism of deformable aircraft deformation aerodynamic force

(2) analyze the iron content in the lubricating oil. When the friction surface is constantly supplied with lubricating oil, according to the technical index requirements of the U.S. Defense pre research agency, the layout optimization design of the deformable aircraft

(3) flight stability and controllability during deformation

(4) intelligent material and deformation mechanism

(5) advanced sensors and actuators

(6) air servo elasticity

(7) structural failure mechanism, fault monitoring, safety management and system reliability

(8) deformed body aircraft test and flight simulation

conclusion

in 2008, focusing on deformable body technology, NASA actively committed to the research of compact solid actuators and high temperature shape memory alloys (SMAs) with structural reconstruction ability. NASA green, together with Boeing, NASA Langley, and Texas a&m, has established a new organization to accelerate the development and certification of reconfigurable aerospace structures based on high temperature shape memory alloys. The Air Force Institute of technology studied the distribution and optimal orientation of actuators through a plane flexible deformable wing. At NASA 12.2m × In the 24.4m wind tunnel, Boeing, the air force, NASA, the army, Massachusetts Institute of technology and the University of Maryland have verified the adjustment piece of intelligent material control on the full-scale rotor for the first time. NASA Dryden Flight Center demonstrated and verified the ability of sensing wing shape and determining structural stress in flight. The University of Florida demonstrated the feasibility of using ionic polymer alloys for in-flight actuation. Pennsylvania is developing high strain materials with the concept of cell structure and auxiliary connection adaptive mechanism

n-mas wind tunnel test

looking forward to the future, the research on deformable body technology will enable the future aircraft to effectively perform a variety of different tasks under a wider range of flight conditions, significantly reducing the cost of aircraft manufacturing and operation; Militarily, deformable aircraft will have stronger ability to maneuver and stay in the air for a long time. In addition, the new achievements brought by the development of deformable body technology will also be applied to conventional aircraft and significantly improve the performance of existing aircraft