微型飞行器中的若干动力学问题研究
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摘要
微型飞行器是一种融MEMS技术等多种技术于一体的集成化智能微系统。微型飞行器不是常规飞行器的简单小型化，需要提出和发展许多不同于传统飞行器设计的新概念。作为微型飞行器技术中蕴涵的重要科学问题之一，微系统力学的研究将为发展微型飞行器设计的新理念奠定科学的基础。本文就此对微型飞行器涉及的微系统动力学方面的若干问题展开了相应的研究。
论文首先回顾了微型飞行器产生的背景、发展过程和目前的研究现状，较全面地分析了微型飞行器的基本特征、应用前景以及微型飞行器所涉及的关键技术，总结了微型飞行器中蕴涵的科学问题，阐明了微系统力学的研究对微系统技术和微型飞行器发展的重要意义。
微型飞行器的飞行雷诺数和自然界中小型飞行动物(如小鸟、昆虫等)的相当。低雷诺数使得基于定常附着流理论得到的升力不足以平衡微型飞行器自身的重量。论文研究了动物和昆虫等生物的飞行方式和飞行机理，分析论证了微型飞行器在低雷诺数条件下采用扑翼飞行方式的可行性和必要性。同时通过对生物飞行随尺度变化规律的研究，得出了对微型飞行器采用扑翼设计布局具有价值的规律，导出了扑翼布局微型飞行器的尺度律。
结构尺度的减小使结构物的力学行为对应变率愈加敏感。对于在实际使用过程中经常承受动态冲击载荷的微型飞行器，论文研究了相似模型中若干力学量、力学实验及现象中塑性应变率的尺度效应对材料和结构动态响应的影响，深入探讨了两种考虑应变率效应的Cowper-Symonds与Johnson-Cook动态本构关系所描述的材料中塑性应变率的尺度效应。
构成微型飞行器系统的基本结构元件在冲击载荷下的动态塑性响应问题，已经有许多实验和理论上的研究。论文首次利用“响应数”将这些已有的实验和理论研究结果中诸多的物理参量统一表示为简洁的无量纲形式，以更好地运用于微型飞行器中的相应结构。
固体材料结构随着特征尺度减小表现出明显的尺度效应，当波长与材料微结构的特征尺度具有相同的数量级时，材料的微结构对波的传播有很大的影响。论文研究了微系统冲击动力失效及可靠性研究中的重要基础问题之一，应力波在梯度弹性介质中的行为，得到了考虑材料内部特征尺度时无限大体中的横波、纵波，一维杆中的纵波以及扭转波的相速度和波长的关系。
作为微型飞行器关键器件之一的微加速度计，论文最后部分对其结构失效问题进行了实验与数值分析研究。通过实验和数值分析，指出了冲击载荷下微加速度计结构失效的主要特点和形式，阐述了应力波在微结构失效问题分析中的重要应用，分析了微加速度计结构设计、制备和实验中的问题，得到了由冲击载荷所引起的微机械加速度计多个内部微结构复杂的粘着失效新模式，对于研究微系统在冲击过载下的粘着失效行为提供了重要的参考作用。
MAVs (Micro Air Vehicles) is one kind of integrated intelligent micro system involving MEMS (Micro-Electro-Mechanical Systems) and many other technologies. MAVs is not a simplified miniature of conventional air vehicle. It is necessary to develop a large number of new conceptions for the design of MAVs. Micro system mechanics is one of the basic scientific principles to develop the new generation of MAVs. Therefore, some dynamic problems in MAVs are studies in this dissertation.
At first, the dissertation reviews the backgrounds, development and state-of-the-art of MAVs, and presents the basic characteristics, application prospects and key technologies of MAVs. At the same time, the dissertation summarizes the scientific principles involved in MAVs and elucidates the importance of micro system mechanics for the development of MAVs.
Then, for the difficulties when flying under lower Reynolds number, the dissertation carries out some researches on the flight mechanism of animals and insects, and demonstrates that it is possible and necessary to adopt flapping wing configuration after the nature flying creatures. Also, the dissertation presents some valuable principles for the flapping wing configuration, and has induced the scaling laws for the MAVs with flapping wings.
Usually, MAVs is working under dynamic environment. Considering the scale effects with the decrease of dimension in MAVs, the dissertation studies the scale effects of plastic strain rate in some mechanical problems and presents a detail discussion on two dynamic constitutive equations considering strain rate effects.
There have been many theoretical and experimental studies on the dynamic plastic behavior of structures. For the first time, the author reformulates many results and physical parameters about the structure dynamic response into new dimensionless concise forms with response number, which could be used to study the corresponding structures in MAVs.
As an important basic problem on the dynamic failures and reliabilities of micro systems under impact loadings, the propagation of stress wave in gradient elastic medium has been studied. The dissertation has derived the relationships between phase speed and wave length, which relate to the transverse waves and longitudinal waves in infinite medium, the longitudinal waves and torsional waves in a thin rod.
At last, a kind of inertial MEMS devices for MAVs, micromachined accelerometer, has been studied experimentally and numerically and their dynamic reliability has been
also investigated. In this dissertation, drop tests and some structural failure analyses have been implemented for two typical newly designed microaccelerometers fabricated by the standard bulk-machining process. Researches in this dissertation have presented the main characteristics and modes for the failures on the structures of micro accelerometer, and elucidated the application of stress waves in the failure analysis of micro structures. Also, the dissertation has demonstrated the problem on structural design, fabrication and tests of micro accelerometers. The most important is that some new kinds of failure modes on adhesion have been found in micromachined accelerometers under impact loadings, and it is valuable for the study on the adhesion failure of micro systems subjected to impact loadings.
论文首先回顾了微型飞行器产生的背景、发展过程和目前的研究现状，较全面地分析了微型飞行器的基本特征、应用前景以及微型飞行器所涉及的关键技术，总结了微型飞行器中蕴涵的科学问题，阐明了微系统力学的研究对微系统技术和微型飞行器发展的重要意义。
微型飞行器的飞行雷诺数和自然界中小型飞行动物(如小鸟、昆虫等)的相当。低雷诺数使得基于定常附着流理论得到的升力不足以平衡微型飞行器自身的重量。论文研究了动物和昆虫等生物的飞行方式和飞行机理，分析论证了微型飞行器在低雷诺数条件下采用扑翼飞行方式的可行性和必要性。同时通过对生物飞行随尺度变化规律的研究，得出了对微型飞行器采用扑翼设计布局具有价值的规律，导出了扑翼布局微型飞行器的尺度律。
结构尺度的减小使结构物的力学行为对应变率愈加敏感。对于在实际使用过程中经常承受动态冲击载荷的微型飞行器，论文研究了相似模型中若干力学量、力学实验及现象中塑性应变率的尺度效应对材料和结构动态响应的影响，深入探讨了两种考虑应变率效应的Cowper-Symonds与Johnson-Cook动态本构关系所描述的材料中塑性应变率的尺度效应。
构成微型飞行器系统的基本结构元件在冲击载荷下的动态塑性响应问题，已经有许多实验和理论上的研究。论文首次利用“响应数”将这些已有的实验和理论研究结果中诸多的物理参量统一表示为简洁的无量纲形式，以更好地运用于微型飞行器中的相应结构。
固体材料结构随着特征尺度减小表现出明显的尺度效应，当波长与材料微结构的特征尺度具有相同的数量级时，材料的微结构对波的传播有很大的影响。论文研究了微系统冲击动力失效及可靠性研究中的重要基础问题之一，应力波在梯度弹性介质中的行为，得到了考虑材料内部特征尺度时无限大体中的横波、纵波，一维杆中的纵波以及扭转波的相速度和波长的关系。
作为微型飞行器关键器件之一的微加速度计，论文最后部分对其结构失效问题进行了实验与数值分析研究。通过实验和数值分析，指出了冲击载荷下微加速度计结构失效的主要特点和形式，阐述了应力波在微结构失效问题分析中的重要应用，分析了微加速度计结构设计、制备和实验中的问题，得到了由冲击载荷所引起的微机械加速度计多个内部微结构复杂的粘着失效新模式，对于研究微系统在冲击过载下的粘着失效行为提供了重要的参考作用。
MAVs (Micro Air Vehicles) is one kind of integrated intelligent micro system involving MEMS (Micro-Electro-Mechanical Systems) and many other technologies. MAVs is not a simplified miniature of conventional air vehicle. It is necessary to develop a large number of new conceptions for the design of MAVs. Micro system mechanics is one of the basic scientific principles to develop the new generation of MAVs. Therefore, some dynamic problems in MAVs are studies in this dissertation.
At first, the dissertation reviews the backgrounds, development and state-of-the-art of MAVs, and presents the basic characteristics, application prospects and key technologies of MAVs. At the same time, the dissertation summarizes the scientific principles involved in MAVs and elucidates the importance of micro system mechanics for the development of MAVs.
Then, for the difficulties when flying under lower Reynolds number, the dissertation carries out some researches on the flight mechanism of animals and insects, and demonstrates that it is possible and necessary to adopt flapping wing configuration after the nature flying creatures. Also, the dissertation presents some valuable principles for the flapping wing configuration, and has induced the scaling laws for the MAVs with flapping wings.
Usually, MAVs is working under dynamic environment. Considering the scale effects with the decrease of dimension in MAVs, the dissertation studies the scale effects of plastic strain rate in some mechanical problems and presents a detail discussion on two dynamic constitutive equations considering strain rate effects.
There have been many theoretical and experimental studies on the dynamic plastic behavior of structures. For the first time, the author reformulates many results and physical parameters about the structure dynamic response into new dimensionless concise forms with response number, which could be used to study the corresponding structures in MAVs.
As an important basic problem on the dynamic failures and reliabilities of micro systems under impact loadings, the propagation of stress wave in gradient elastic medium has been studied. The dissertation has derived the relationships between phase speed and wave length, which relate to the transverse waves and longitudinal waves in infinite medium, the longitudinal waves and torsional waves in a thin rod.
At last, a kind of inertial MEMS devices for MAVs, micromachined accelerometer, has been studied experimentally and numerically and their dynamic reliability has been
also investigated. In this dissertation, drop tests and some structural failure analyses have been implemented for two typical newly designed microaccelerometers fabricated by the standard bulk-machining process. Researches in this dissertation have presented the main characteristics and modes for the failures on the structures of micro accelerometer, and elucidated the application of stress waves in the failure analysis of micro structures. Also, the dissertation has demonstrated the problem on structural design, fabrication and tests of micro accelerometers. The most important is that some new kinds of failure modes on adhesion have been found in micromachined accelerometers under impact loadings, and it is valuable for the study on the adhesion failure of micro systems subjected to impact loadings.
引文
[1] 赵亚溥．微型飞行器中的关键力学和智能材料问题．中国科学基金．2000，(1)，pp．11-14．
[2] C.P. Ellington.The novel aerodynamics of insect flight: applications to micro-air vehicles.Journal of Experimental Biology.1999, 202 (23),pp.3439-3448.
[3] 武际可．力学史．重庆：重庆出版社．2000．
[4] R.O. Hundley, E.C. Gritton.Future Technology-Driven Revolutions in Military Operations.Documented Briefing of the RAND National Defense Research Institute.December,1992.
[5] R.O. Hundley, E.C. Gritton. Future Technology-Driven Revolutions in Military Operations:Results of a Workshop.RAND Corporation.Santa Monica,CA.1994.Document No.DB-110-ARPA.
[6] W.R. Davis. Micro UAV.In: 23rd Annual AUVSI Symposium. July 15-19,1996.
[7] S. Ashley. Palm-size spy plane.Mechanical Engineering.1999,120 (2), pp.74-78.
[8] J.M. Grasmeyer, M.T. Keennon. Development of the Black Widow Micro Air Vehicle. 2001.AIAA Paper No.2001-0127.
[9] J.M. McMichael, M.S. Francis. Micro Air Vehicles-Toward a New Dimension in Flight.USAF,DARPA TTO document.August 7,1997.
[10] 吴宇怀，周兆英，熊沈蜀，et al，微型飞行器的研究现状及其关键技术．武汉科技大学学报(自然科学版)．2000，23(2)，PP．170-174．
[11] 辛健成，喷薄欲出的微型无人机(上)．机器人技术与应用．1999，(4)，pp．24-25．
[12] Micro Air Vehicles. Themed Studies TS6. March, 1999.
[13] M. Dwortzan. It's a fly! It's a bug! It's a microplane.October,1997.
[14] 王立文．空中小精灵--微型飞行器挑战传统设计思维和战争模式．国际航空．2000，(12)，pp．46-48．
[15] M.A. Dornheim. Tiny drones may be soldier's new tool.Aviation Week & Space Technology.1998, 148, pp.42-43.
[16] Darpa selects micro air vehicle contractor.News Release. December 12, 1997.
[17] 辛健成．喷薄欲出的微型无人机(下)．机器人技术与应用．1999，(5)，pp．23-26．
[18] 晓清．美国微型飞行器计划进入飞行试验阶段．国际航空．1999，(9)，pp．55-56．
[19] MicroSTAR soars in quantico demonstration.Sanders News.November 6,2000.
[20] H. Keeter.DARPA says MAV acquisition schedule driven by technology. Defense Daily.July 29, 1999.
[21] I. Kroo, P. Kunz. Miniature rotorcraft as aerial explorers.In: NASA/DoD Second Biomorphic Explorers Workshop.December 5,2000.
[22] I. Kroo, F. Prinz, M. Shantz, et al. The Mesicopter: A Miniature Rotorcraft Concept-Phase Ⅱ Interim Report.July,2000.
[23] T.N. Pornsin-Sirirak,Y.-C.Tai,C.-M. Ho,et al.Microbat:a palm-sized electrically powered ornithopter.In:The NASA/JPL Workshop on Biomorphic Robotics.Pasadena, California,USA.August 14-16,2000.
[24] SRI (SRI International).Artificial muscle transducers.Internet URL:http://www.erg.sri.com/automation/actuators.html.2001.
[25] UTIAS (University of Toronto Institute for Aerospace Studies).Micro Air Vehicle.Internet URL:http://www.utias.toronto.edu/test/res/fm/fda-proj.html.2002.
[26] A. Stone.Flying into the Future.Georgia Tech Research Horizons.Spring,1997.
[27] J. Toon. Flying on Mars.Georgia Tech Research Horizons.2001,19(1),pp.19-23.
[28] R.C.Michelson,S.Reece.Update on flapping wing micro air vehicle research ongoing work to develop a flapping wing,crawling "Entomopter".In:13th Bristol International RPV Conference.Bristol,England.March 30-April 1,1998.
[29] A.Colozza.Planetary exploration using biomimetics:an Entomopter for flight on Mars.In:NIAC Fellows Conference.NASA Ames Research Center.June 6,2001.
[30] P.Scott.A bug's lift-the Defense Department is looking for a few good mechanical insects.Scientific American.1999,280 (4),pp.51-52.
[31] Micromechanical Flying Insect (MFI) project.2001.
[32] T. Sands. NanoEngineered Crystalline Materials for Artificial Muscle,Solid-State Lighting and Quantum-effect Refrigeration.2001.
[33] J. Fleming, W. Ng,S.Ghamaty.Thermoelectric-based power system for UAV/MAV applications.American Institute of Aeronautics and Astronautics.2002.AIAA Paper No.2002-3412.
[34] Darpa recognizes excellence in past year.News Release.September 25,1997.
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[36] T.N. Pornsin-Sirirak, Y.-C. Tai,H.Nassef,et al. Unsteady-state aerodynamic performance of MEMS wings.In: International Symposium on Smart Structures and Microsystems.The Jockey Club,Hong Kong.October 19-21,2000.
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[2] C.P. Ellington.The novel aerodynamics of insect flight: applications to micro-air vehicles.Journal of Experimental Biology.1999, 202 (23),pp.3439-3448.
[3] 武际可．力学史．重庆：重庆出版社．2000．
[4] R.O. Hundley, E.C. Gritton.Future Technology-Driven Revolutions in Military Operations.Documented Briefing of the RAND National Defense Research Institute.December,1992.
[5] R.O. Hundley, E.C. Gritton. Future Technology-Driven Revolutions in Military Operations:Results of a Workshop.RAND Corporation.Santa Monica,CA.1994.Document No.DB-110-ARPA.
[6] W.R. Davis. Micro UAV.In: 23rd Annual AUVSI Symposium. July 15-19,1996.
[7] S. Ashley. Palm-size spy plane.Mechanical Engineering.1999,120 (2), pp.74-78.
[8] J.M. Grasmeyer, M.T. Keennon. Development of the Black Widow Micro Air Vehicle. 2001.AIAA Paper No.2001-0127.
[9] J.M. McMichael, M.S. Francis. Micro Air Vehicles-Toward a New Dimension in Flight.USAF,DARPA TTO document.August 7,1997.
[10] 吴宇怀，周兆英，熊沈蜀，et al，微型飞行器的研究现状及其关键技术．武汉科技大学学报(自然科学版)．2000，23(2)，PP．170-174．
[11] 辛健成，喷薄欲出的微型无人机(上)．机器人技术与应用．1999，(4)，pp．24-25．
[12] Micro Air Vehicles. Themed Studies TS6. March, 1999.
[13] M. Dwortzan. It's a fly! It's a bug! It's a microplane.October,1997.
[14] 王立文．空中小精灵--微型飞行器挑战传统设计思维和战争模式．国际航空．2000，(12)，pp．46-48．
[15] M.A. Dornheim. Tiny drones may be soldier's new tool.Aviation Week & Space Technology.1998, 148, pp.42-43.
[16] Darpa selects micro air vehicle contractor.News Release. December 12, 1997.
[17] 辛健成．喷薄欲出的微型无人机(下)．机器人技术与应用．1999，(5)，pp．23-26．
[18] 晓清．美国微型飞行器计划进入飞行试验阶段．国际航空．1999，(9)，pp．55-56．
[19] MicroSTAR soars in quantico demonstration.Sanders News.November 6,2000.
[20] H. Keeter.DARPA says MAV acquisition schedule driven by technology. Defense Daily.July 29, 1999.
[21] I. Kroo, P. Kunz. Miniature rotorcraft as aerial explorers.In: NASA/DoD Second Biomorphic Explorers Workshop.December 5,2000.
[22] I. Kroo, F. Prinz, M. Shantz, et al. The Mesicopter: A Miniature Rotorcraft Concept-Phase Ⅱ Interim Report.July,2000.
[23] T.N. Pornsin-Sirirak,Y.-C.Tai,C.-M. Ho,et al.Microbat:a palm-sized electrically powered ornithopter.In:The NASA/JPL Workshop on Biomorphic Robotics.Pasadena, California,USA.August 14-16,2000.
[24] SRI (SRI International).Artificial muscle transducers.Internet URL:http://www.erg.sri.com/automation/actuators.html.2001.
[25] UTIAS (University of Toronto Institute for Aerospace Studies).Micro Air Vehicle.Internet URL:http://www.utias.toronto.edu/test/res/fm/fda-proj.html.2002.
[26] A. Stone.Flying into the Future.Georgia Tech Research Horizons.Spring,1997.
[27] J. Toon. Flying on Mars.Georgia Tech Research Horizons.2001,19(1),pp.19-23.
[28] R.C.Michelson,S.Reece.Update on flapping wing micro air vehicle research ongoing work to develop a flapping wing,crawling "Entomopter".In:13th Bristol International RPV Conference.Bristol,England.March 30-April 1,1998.
[29] A.Colozza.Planetary exploration using biomimetics:an Entomopter for flight on Mars.In:NIAC Fellows Conference.NASA Ames Research Center.June 6,2001.
[30] P.Scott.A bug's lift-the Defense Department is looking for a few good mechanical insects.Scientific American.1999,280 (4),pp.51-52.
[31] Micromechanical Flying Insect (MFI) project.2001.
[32] T. Sands. NanoEngineered Crystalline Materials for Artificial Muscle,Solid-State Lighting and Quantum-effect Refrigeration.2001.
[33] J. Fleming, W. Ng,S.Ghamaty.Thermoelectric-based power system for UAV/MAV applications.American Institute of Aeronautics and Astronautics.2002.AIAA Paper No.2002-3412.
[34] Darpa recognizes excellence in past year.News Release.September 25,1997.
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