DISTRIBUTED ELECTRO-MECHANICAL ACTUATION AND SENSING SYSTEM DESIGN FOR MORPHING STRUCTURES

Smart structures, able to sense changes of their own state or variations of the environment they’re in, and capable of intervening in order to improve their performance, find themselves in an ever-increasing use among numerous technology fields, opening new frontiers within advanced structural engineering and materials science. Smart structures represent of course a current challenge for the application on the aircrafts. A morphing structure can be considered as the result of the synergic integration of three main systems: the structural system, based on reliable kinematic mechanisms or on compliant elements enabling the shape modification, the actuation and control systems, characterized by embedded actuators and robust control strategies, and the sensing system, usually involving a network of sensors distributed along the structure to monitor its state parameters. Technologies with ever increasing maturity level are adopted to assure the consolidation of products in line with the aeronautical industry standards and fully compliant with the applicable airworthiness requirements. Until few years ago, morphing wing technology appeared an utopic solution. In the aeronautical field, airworthiness authorities demand a huge process of qualification, standardization, and verification. Essential components of an intelligent structure are sensors and actuators. The actual technological challenge, envisaged in the industrial scenario of “more electric aircraft”, will be to replace the heavy conventional hydraulic actuators with a distributed strategy comprising smaller electro-mechanical actuators. This will bring several benefit at the aircraft level: firstly, fuel savings. Additionally, a full electrical system reduces classical drawbacks of hydraulic systems and overall complexity, yielding also weight and maintenance benefits. At the same time, a morphing structure needs a real-time strain monitoring system: a nano-engineered polymer capable of densely distributed strain sensing can be a suitable solution for this kind of flying systems. Piezoresistive carbon nanotubes can be integrated as thin films coated and integrated with composite to form deformable self-sensing materials. The materials actually become sensors themselves without using external devices, embedded or attached. This doctoral thesis proposes a multi-disciplinary investigation of the most modern actuation and sensing technologies for variable-shaped devices mainly intended for large commercial aircraft. The personal involvement in several research projects with numerous international partners - during the last three years - allowed for exploiting engineering outcomes in view of potential certification and industrialization of the studied solutions. Moving from a conceptual survey of the smart systems that introduces the idea of adaptive aerodynamic surfaces and main research challenges, the thesis presents (Chapter 1) the current worldwide status of morphing technologies as well as industrial development expectations. The Ph.D. programme falls within the design of some of the most promising and potentially flyable solutions for performance improvement of green regional aircrafts. A camber-morphing aileron and a multi-modal flap are herein analysed and assessed as subcomponents involved for the realization of a morphing wing. An innovative camber-morphing aileron was proposed in CRIAQ MD0-505, a joint Canadian and Italian research project. Relying upon the experimental evidence within the present research, the issue appeared concerns the critical importance of considering the dynamic modelling of the actuators in the design phase of a smart device. The higher number of actuators involved makes de facto the morphing structure much more complex. In this context (Chapter 2), the action of the actuators has been modelled within the numerical model of the aileron: the comparison between the modal characteristics of numerical predictions and testing activities has shown a high level of correlation. Morphing structures are characterized by many more degrees of freedom and increased modal density, introducing new paradigms about modelling strategies and aeroelastic approaches. These aspects affect and modify many aspects of the traditional aeronautical engineering process, like simulation activity, design criteria assessment, and interpretation of the dynamic response (Chapter 3). With respect the aforementioned aileron, sensitivity studies were carried out in compliance with EASA airworthiness requirements to evaluate the aero-servo-elastic stability of global system with respect to single and combined failures of the actuators enabling morphing. Moreover, the jamming event, which is one of the main drawbacks associated with the use of electro-mechanical actuators, has been duly analyzed to observe any dynamic criticalities. Fault & Hazard Analysis (FHA) have been therefore performed as the basis for application of these devices to real aircraft. Nevertheless, the implementation of an electro-mechanical system implies several challenges related to the integration at aircraft system level: the practical need for real-time monitoring of morphing devices, power absorption levels and dynamic performance under aircraft operating conditions, suggest the use of a ground-based engineering tool, i.e. “iron bird”, for the physical integration of systems. Looking in this perspective, the Chapter 4 deals with the description of an innovative multi-modal flap idealized in the Clean Sky - Joint Technology Initiative research scenario. A distributed gear-drive electro-mechanical actuation has been fully studied and validated by an experimental campaign. Relying upon the experience gained, the encouraging outcomes led to the second stage of the project, Clean Sky 2 - Airgreen 2, encompassing the development of a more robotized flap for next regional aircraft. Numerical and experimental activities have been carried out to support the health management process in order to check the EMAs compatibility with other electrical systems too. A smart structure as a morphing wing needs an embedded sensing system in order to measure the actual deformation state as well as to “monitor” the structural conditions. A new possible approach in order to have a distributed light-weight system consists in the development of polymer-based materials filled with conductive smart fillers such as carbon nanotubes (CNTs). The thesis ends with a feasibility study about the incorporation of carbon nanomaterials into flexible coatings for composite structures (Chapter 5). Coupons made of MWCNTs embedded in typical aeronautic epoxy formulation were prepared and tested under different conditions in order to better characterize their sensing performance. Strain sensing properties were compared to commercially available strain gages and fiber optics. The results were obtained in the last training year following the involvement of the author in research activities at the University of Salerno and Materials and Structures Centre - University of Bath. One of the issues for the next developments is to consolidate these novel technologies in the current and future European projects where the smart structures topic is considered as one of the priorities for the new generation aircrafts. It is remarkable that scientists and aeronautical engineers community does not stop trying to create an intelligent machine that is increasingly inspired by nature. The spirit of research, the desire to overcome limits and a little bit of imagination are surely the elements that can guide in achieving such an ambitious goal

Conceptual designs of multi-degree of freedom compliant parallel manipulators composed of wire-beam based compliant mechanisms

This paper proposes conceptual designs of multi-degree(s) of freedom (DOF) compliant parallel manipulators (CPMs) including 3-DOF translational CPMs and 6-DOF CPMs using a building block based pseudo-rigid-body-model (PRBM) approach. The proposed multi-DOF CPMs are composed of wire-beam based compliant mechanisms (WBBCMs) as distributed-compliance compliant building blocks (CBBs). Firstly, a comprehensive literature review for the design approaches of compliant mechanisms is conducted, and a building block based PRBM is then presented, which replaces the traditional kinematic sub-chain with an appropriate multi-DOF CBB. In order to obtain the decoupled 3-DOF translational CPMs (XYZ CPMs), two classes of kinematically decoupled 3-PPPR (P: prismatic joint, R: revolute joint) translational parallel mechanisms (TPMs) and 3-PPPRR TPMs are identified based on the type synthesis of rigid-body parallel mechanisms, and WBBCMs as the associated CBBs are further designed. Via replacing the traditional actuated P joint and the traditional passive PPR/PPRR sub-chain in each leg of the 3-DOF TPM with the counterpart CBBs (i.e. WBBCMs), a number of decoupled XYZ CPMs are obtained by appropriate arrangements. In order to obtain the decoupled 6-DOF CPMs, an orthogonally-arranged decoupled 6-PSS (S: spherical joint) parallel mechanism is first identified, and then two example 6-DOF CPMs are proposed by the building block based PRBM method. It is shown that, among these designs, two types of monolithic XYZ CPM designs with extended life have been presented

Conjoined piezoelectric harvesters and carbon supercapacitors for powering intelligent wireless sensors

To achieve total freedom of location for intelligent wireless sensors (IWS), these need to be autonomous. To achivethis today there is a need of broadband piezoelectric energy harvesting and a long-lasting energy. The Harvester needto be able to provide sufficient amount of energy for the intelligent wireless sensor to perform its task. The energystorage needs to fulfill the requirement of a large number of charge discharge cycles and contain sufficient power forthe intelligent wireless sensor.The biggest issue with piezoelectric energy harvesting today is the bandwidth limitation. Solutions today to achievelarger bandwidth make a tradeoff where the output is decreased. The biggest issue for energy storage today is thelimitation of energy density for supercapacitors and the lack of sufficient life cycles for batteries.This thesis aims to realize piezoelectric energy harvesters with broad bandwidth and maintained power output.Moreover, for energy storage in the form of supercapacitors realize an electrode material that has a high effectivesurface area, good conductivity not dependent on a conductive agent and can be used without a binder. This thesiscover background and history of the two fields, discussion of technologies used and presents solutions for piezoelectricenergy harvesting and carbon based supercapacitor storage.A Backfolded piezoelectric harvester was made of two conjoined piezoelectric cantilevers, one placed on top of abottom cantilever. By the backfolded design this thesis show that by utilizing the extended stress distribution of thebottom cantilever a maintained power output is achieved for both output peaks. By introducing asymmetry where thetop cantilever have 80% length compared with the bottom cantilever the bandwidth was increased. An effectivebandwidth of 70 Hz with voltage output above 2,75 V for 1 g is achieved.To achieve further enhanced bandwidth a piezoelectric energy harvester with selftuning was designed. Theselftuning was achieved by a sliding mass on a beam, which is conjoined, to two piezoelectric cantilevers in abackfolded structure. By introducing length asymmetry, the effective bandwidth was enhanced to 38 Hz with a poweroutput above 15 mW, for 1 g, which is sufficient for an intelligent wireless sensor to start up and transmit data.To utilize the positive output effect from conjoined cantielvers a micro harvester was fabricated. The design wasbased on the same principle as for the backfolded, but for fabrication reasons the design was made in one plane. Theharvester contain two outer cantilevers conjoined to a backfolded middle cantilever. Due to fabrication difficulties,only a mechanical characterization of the harvester was possible. The result from the characterization looks promisingfrom a harvesting point of view, by showing a clear peak that seems to be somewhat broadband.Energy storage for an autonomous wireless intelligent sensor (IWS) needs to be able to charge and discharge duringthe lifetime of the IWS. Therefor the choice fell on supercapacitors instead of batteries. Over time the supercapacitordue to its superior amount of charge and discharge cycles, outperform a battery when energy density is compared.Increasing the energy density for supercapacitors gives the advantage to prolong the providing of power to theIWS. One such electrode material is conjoined carbon nanofibers and carbon nanotubes. The material is not dependenton conductive agents or binders. The effective surface area can be expanded through a denser structure of CNF, wheremore CNT can grow. In combination with activation, which will yield more micropores, hence an increasedcapacitance for the presented synthesized material yielded 91 F/g with an effective surface area of 131 m2.There is many challenges to power an IWS on a gasturbine. This thesis cover challenges like vibrations on cables,placement issues and the charge of a supercapacitor by harvested energy that comes in small chunks. Solutions forthese challenges are offered.The presented work in this thesis shows how the bandwidth for piezoelectric energy harvesters can be broader byasymmetric implementation of conjoined resonators. In addition, the advantages of conjoined carbon electrodematerials to be implemented as electrode material in supercapacitors. Both harvester and storage are intended to beused as energy sources for intelligent wireless sensors

Materials Science and Technology

Materials are important to mankind because of the benefits that can be derived from the manipulation of their properties, for example electrical conductivity, dielectric constant, magnetization, optical transmittance, strength and toughness. Materials science is a broad field and can be considered to be an interdisciplinary area. Included within it are the studies of the structure and properties of any material, the creation of new types of materials, and the manipulation of a material's properties to suit the needs of a specific application. The contributors of the chapters in this book have various areas of expertise. therefore this book is interdisciplinary and is written for readers with backgrounds in physical science. The book consists of fourteen chapters that have been divided into four sections. Section one includes five chapters on advanced materials and processing. Section two includes two chapters on bio-materials which deal with the preparation and modification of new types of bio-materials. Section three consists of three chapters on nanomaterials, specifically the study of carbon nanotubes, nano-machining, and nanoparticles. Section four includes four chapters on optical materials

성능-침강안정성 상충 문제 해결을 위한 복합체 기반 자기유변유체에 대한 연구

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 재료공학부, 2021. 2. 서용석.Magnetorheological (MR) fluids are smart materials composed of magnetic particles dispersed in magnetically-insulating carrier medium. With magnetic field, chain-like structures are formed due to dipole-induced magnetostatic interaction between magnetic particles, and the structures inhibit the flow and increase the viscosity of MR fluids in very short time. This characteristic enables the rheological properties of MR fluids to be easily tailored with magnetic field strength. Due to this unique response, MR fluids can be used for actuator systems like power steering pumps haptic devices, and active suspensions, and damper systems in automobile, bridges, buildings and so on. A huge obstacle for application of MR fluids is their poor long-term stability against the sedimentation of magnetic particles. The large difference in the density between heavy magnetic particles and light medium make magnetic particles quickly go down to bottom, reducing the MR fluids length of life. One of the strategies for improvement of the long-term stability was to reduce the density of magnetic particles by synthesizing magnetic composite materials. Fabrication of magnetic composites using light materials such as polymer, silica, carbon materials efficiently have reduced the density mismatch between magnetic materials and carrier medium, enhancing the long-term stability of MR fluids. However, there was trade-off between long-term stability and performance of MR fluids because use of light materials is equivalent to the deterioration in magnetic properties. In this study, various magnetic composites with different composition and structures were fabricated for the objective of producing MR fluids having excellent performance and long-term stability simultaneously. As a first step, hollow structured polymer-Fe3O4 composite particles were synthesized using SiO2 as sacrificial template. With cavity inside, the hollow magnetic composite particles showed the density only 40 % of bare Fe3O4 and the large improvement in long-term stability of MR suspensions could be observed. To avoid huge decline in MR performance with non-magnetic polymers, hierarchically-structured Fe3O4 nanoparticles were prepared with simple electrospraying process. By excluding polymers, hierarchically-structured Fe3O4 had magnetization value very closed to its primary nanoparticles, leading to MR performance higher more than 3 times of hollow structured polymer-Fe3O4 suspensions. At the same time, the pores inside reduced the density of the structured particles by 23 %, resulting in better long-term stability of hierarchically-structured Fe3O4 suspension than bare Fe3O4 suspension. To minimize the trade-off between MR performance and long-term stability (density of magnetic particles), non-spherical, CoFeNi-based magnetic composites were fabricated and applied for MR fluids. CNT-Co0.4Fe0.4Ni0.2 composite was produced by synthesizing Co0.4Fe0.4Ni0.2 on the surface of functionalized CNTs. Much higher magnetization of Co0.4Fe0.4Ni0.2 compared to Fe3O4 enabled CNT-Co0.4Fe0.4Ni0.2 suspension to have much superior MR performance than Fe3O4 composite-based MR fluids. Also, due to high aspect ratio of CNTs, outstanding long-term stability of 22 % light transmission was observed with formation of 3-dimensional network structures. Finally, magnetically non-active CNTs were replaced by magnetizable, flake-shaped sendust. The high drag coefficient of flake sendust, combined with roughened surface due to attached Co0.4Fe0.4Ni0.2 nanoparticles, resulted in excellent stability with 23 % of light transmission despite of the high density of sendust-Co0.4Fe0.4Ni0.2 composite particles. Also, because both constituents of sendust-Co0.4Fe0.4Ni0.2 are both magnetic materials with high magnetization value, the MR fluids retained very high yield stress value자기유변유체는 자성입자가 비자성 매개액에 분산된 현탁액 형태의 스마트물질이다. 외부 자기장 하에서 자성입자들 사이의 쌍극자로 인한 정자기성 상호작용으로 체인 형태의 구조가 형성되고, 이 구조가 유체의 흐름을 막아 매우 짧은 시간 내에 점도가 크게 향상되게 된다. 이러한 성질로 인해 자기유변유체의 유변특성을 외부 자기장을 통해 쉽게 조절하는 것이 가능하다. 이러한 외부자장에 대한 톡특한 반응성으로 인해, 햅틱 디바이스 파워스티어링 펌프, 그리고 자동차, 다리, 건물 등의 충격 방지 시스템에 자기유변유체를 이용할 수 있다. 하지만 자기유변유체의 활용은 자성입자의 침전에 대한 안정성의 부족함으로 인해 크게 제한 될 수 있다. 밀도가 높은 자성입자와 밀도가 낮은 매개액 사이의 큰 밀도차이로 인해 자성입자가 빠르게 가라앉게 되면, 자기유변유체의 수명이 크게 감소하게 된다. 이러한 문제를 해결하기 위한 한가지 방법으로 자성물질과 밀도가 낮은 물질(고분자, 실리카 탄소물질 등)을 결합하여 자성복합입자를 합성함으로써, 자성입자의 밀도를 낮추고 자기유변유체의 침강안정성을 높이는 연구들이 진행되어 왔다. 하지만 이러한 경우 복합자성입자의 자기적 성질이 저하되기 때문에 자기유변유체의 침강안정성과 성능이 서로 상충관계에 있다는 문제점을 가지고 있다. 본 논문에서는 뛰어난 성능과 침강안정성을 가지는 자기유변유체를 제조하기 위해 다양한 물질구성과 구조를 가지는 합성하였다. 첫 단계로 실리카를 템플레이트로 사용하여 할로우 구조를 가지는 고분자-Fe3O4 복합자성입자를 합성하였다. 할로우 구조 내부의 공동으로 인해, 입자의 밀도가 순수 Fe3O4 대비 40 % 수준까지 감소하였고, 이로 인해 자기유변유체의 침강안정성이 크게 상승하였다. 다음 연구로, 비자성 고분자로 인한 자기유변유체 성능의 감소를 최소화하기 위해, 간단한 전기방사 방법을 통해 계층구조를 가지는 Fe3O4 나노입자들을 제조하였다. 앞의 연구와 대비하여, 고분자의 배제를 통해 높은 자화값을 가지는 Fe3O4 나노구조입자들을 얻을 수 있었고, 이를 자기유변유체에 적용하여 할로우 고분자-Fe3O4 입자 기반 자기유변유체 대비 3배 이상의 성능을 가지는 자기유변유체를 얻을 수 있었다. 이와 동시에 Fe3O4 나노구조입자 내부에 생성된 기공들로 인해 순수 Fe3O4 대비 밀도가 약 23 % 정도 감소하였고, 이로 인해 침 Fe3O4 나노구조입자기반 자기유변유체의 침강안정성이 향상됨을 확인할 수 있었다. 자기유변유체의 성능과 침강안정성사이의 상충성을 최소화 하기 위해서 비구형의, CoFeNi 합금기반 자성 복합입자를 합성하고 자기유변유체에 적용하였다. 먼저 개질된 카본나노튜브 표면에 CoFeNi를 합성하는 방법을 통해 카본나노튜브-CoFeNi 복합체를 합성하였다. Fe3O4 대비 높은 CoFeNi의 자화값으로 인해 카본나노튜브-CoFeNi 복합체 기반 자기유변유체는 Fe3O4 복합체기반 유체 대비 3배에서 10배 이상의 뛰어난 유변성능을 보였다. 또한 종횡비가 높은 카본나노튜브로 인해 복합체가 유체 내에서 3차원 네트워크 구조를 형성하여, 빛 투과도 22 %의 매우 뛰어난 침강안정성을 보였다. 마지막으로 비자성 물질인 카본나노튜브를, 자성물질인 플레이크형 센더스트로 대체한 센더스트-CoFeNi 복합입자를 합성하여 자기유변유체에 적용하였다. 플레이크형 센더스트의 높은 종횡비로 인해 나타나는 높은 항력계수로 인해, 해당 자기유변유체는 빛 투과도 23 %의, 높은 입자밀도 대비 매우 뛰어난 침강안정성을 보였다. 동시에, 센더스트 CoFeNi 모두 높은 자화값을 가지는 자성물질이기 때문에, 센더스트-CoFeNi 기반 자기유변유체의 성능이 카본나노튜브-CoFeNi 유체 대비 크게 향상되는 것을 확인할 수 있었다.Contents Abstract ………………………………………………………..........i Contents ……………………………………………………….........v List of Tables ………………………………………………….........x List of Figures ………………………………………………..........xi Chapter 1. Introduction ……………………………………............1 1. 1. Magnetorheological (MR) Fluids and Applications………………….........1 1. 2. Long-Term Stability Problem and Proposed Solutions ……………...........4 1. 3. Research Objectives ………………………………………………….…...7 References ………………………………...........................................................9 Chapter 2. Backgrounds …………………….……………….......16 2. 1. Definition of Terms …………..................................................................16 2. 1. 1. Shear Stress …………........................................................................16 2. 1 .2. Shear Rate …………..........................................................................16 2. 1. 3. Shear Viscosity……............................................................................17 2. 1 .4. Viscoelastic Behavior .........................................................................17 2. 1. 4. 1. Storage Modulus and Loss Modulus ..........................................17 2. 2. Yield Stress of MR Fluids …………........................................................18 2. 2. 1. Rheological Models for Prediction of Dynamic and Static Yield Stress ………….............................................................................................................19 2. 2 .2. Yield Stress Dependency on the Magnetic Field Strength .................22 2. 3. Mechanism of Structures Evolution .........................................................25 References ………............................................................................................27 Chapter 3. Suspensions of Hollow Polydivinylbenzene Nanoparticles Decorated with Fe3O4 Nanoparticles as Magnetorheological Fluids for Microfluidics Applications ........31 3. 1. Introduction ………....................................................................................31 3. 2. Experimental Section ...............................................................................34 3. 2. 1. Synthesis of Hollow Polydivinylbezene (h-PDVB) Particles ............34 3. 2. 2. Deposition of Fe3O4 onto Hollow PDVB Particles ............................36 3. 2. 3. Characterization ..................................................................................37 3. 3. Results and Discussion .............................................................................41 3. 3. 1 Morphology and Structures ..................................................................41 3. 3. 2. Magnetorheological Behaviors ............................................................48 3. 3. 3. Long-Term Stability of Suspensions ...................................................62 3. 4. Conclusion ……….....................................................................................65 References ……….............................................................................................67 Chapter 4. Hierarchically Structured Fe3O4 Nanoparticles for High-Performance Magnetorheological Fluids with Long-Term Stability …………………….………………...................................74 4. 1. Introduction ………...................................................................................74 4. 2. Experimental Section ................................................................................77 4. 2. 1. Synthesis of Citric Acid-Capped Fe3O4 ..............................................77 4. 2. 2. Fabrication of HS-Fe3O4 with Electrospraying Process .....................78 4. 2. 3. Characterization ..................................................................................79 4. 3. Results and Discussion .............................................................................82 4. 3. 1. Morphology and Structures ................................................................82 4. 3. 2. Magnetorheological Behaviors ...........................................................89 4. 3. 3. Long-Term Stability of Suspensions .................................................103 4. 4. Conclusion ………..................................................................................106 References ………..........................................................................................108 Chapter 5. High-Performance Magnetorheological Fluids of Carbon Nanotube-CoFeNi Composites with Enhanced Long-Term Stability…………………….……………….................................116 5. 1. Introduction ………...............................................................................116 5. 2. Experimental Section ............................................................................119 5. 2. 1. Functionalization of Carbon Nanotubes ..........................................119 5. 2. 2. Synthesis of Co0.4¬Fe0.4Ni0.2 and CNT-Co0.4¬Fe0.4Ni0.2 .......................119 5. 2. 3. Characterization ...............................................................................120 5. 3. Results and Discussion ...........................................................................123 5. 3. 1. Morphology and Structures ..............................................................123 5. 3. 2. Magnetorheological Behaviors .........................................................130 5. 3. 3. Long-Term Stability of Suspensions .................................................142 5. 4. Conclusion ………..................................................................................145 References ………..........................................................................................146 Chapter 6. Sendust-CoFeNi Magnetic-Magnetic Composites-Based Magnetorheological Fluids for Simultaneous Improvement of Performance and Long-Term Stability ……………………..154 6. 1. Introduction ………................................................................................154 6. 2. Experimental Section .............................................................................157 6. 2. 1. Synthesis of Citric Acid-Capped Fe3O4 ...........................................157 6. 2. 2. Characterization ...............................................................................157 6. 3. Results and Discussion ...........................................................................159 6. 3. 1. Morphology and Structures ..............................................................159 6. 3. 2. Magnetorheological Behaviors ........................................................163 6. 3. 3. Long-Term Stability of Suspensions ................................................176 6. 4. Conclusion ………..................................................................................179 References ………..........................................................................................181 Chapter 7. Conclusions ………………………………………....188 7. 1. Overall conclusion ………......................................................................188 7. 2. Further works ………..............................................................................194 References ………...........................................................................................195 국문초록 ………...............................................................................................196 List of Publication ………………………………………….......199 Appendix …………………………………………..........…........201 Appendix A. Nonisothermal Crystallization Behaviors of Structure-Modified Polyamides (Nylon 6s) ...............................................................................201Docto

Directly Printed Nanomaterial Sensor for Strain and Vibration Measurement

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 기계공학부, 2020. 8. 안성훈.Most discussions about Industrie 4.0 tacitly assume that any such system would involve the processing and evaluation of large data volumes. Specifically, the operation of complex production processes requires stable and reliable data measurement and communication systems. However, while modern sensor technology may already be capable of collecting a wide range of machine and production data, it has been proving difficult to measure and analyse the data which is not easy to measurable and feed the results quickly back into an optimised production cycle. This is why the cost and installation of sensor, data acquisition, and transmission systems for flexible and adaptive manufacturing process have not been match the requirement of industrial demands. In this dissertation, directly printed nanomaterial sensor capable of strain and vibration measurement with high sensitivity and wide measurable range was fabricated using aerodynamically focused nanomaterial (AFN) printing system which is a direct printing technique for conductive and stretchable pattern printing onto flexible substrate. Specifically, microscale porous conductive pattern composed of silver nanoparticles (AgNPs) and multi-walled carbon nanotubes (MWCNTs) composite was printed onto polydimethylsiloxane (PDMS). Printing mechanism of AFN printing system for nanocomposite onto flexible substrate in order of mechanical crack generation, seed layer deposition, partial aggregation, and fully deposition was demonstrated and experimentally validated. The printed nanocomposite sensor exhibited gauge factor (GF) of 58.7, measurable range of 0.74, and variance in peak resistance under 0.05 during 1,000 times life cycle evaluation test. Furthermore, vibration measurement performance was evaluated according to vibration amplitude and frequency with Q-factor evaluation and statistical verification. Sensing mechanism for nanocomposite sensor was also analysed and discussed by both analytical and statistical methods. First, electron tunnelling effect among nanomaterials was analysed statistically using bivariate probit model. Since electrical property varies by the geometrical properties of nanomaterial, Monte Carlo simulation method based on Lennard-Jones (LJ) potential model and the voter model was developed for deeper understanding of the dynamics of nanomaterial by strain. By simply counting the average attachment among nanomaterials by strain, electrical conductivity was easily estimated with low simulation cost. The main objective of all processes to manufacture high-tech products is compliance with the specified ranges of permissible variation. In this perspective, all data must be recorded that might provide some evidence of status changes anywhere along the process chain. This dissertation covers the monitoring of forming and milling process. By measurement of mechanical deformation of stamp during forming process, it was possible to estimate the forming force according to various process parameters including maximum force, force gradient, and the thickness of sheet metal. Furthermore, accurate and reliable vibration monitoring was also conducted during milling process by simple and direct attachment of printed sensor to workpiece. Using frequency and power spectrum analysis of obtained data, the vibration of workpiece was measured during milling process according to process parameters including RPM, feed rate, cutting depth and width of spindle. Finally, developed sensor was applied to the digital twin of turbine blade manufacturing that vibration greatly affects the quality of product to predict the process defects in real time. To overcome the wire required data acquisition and transmission system, directly printed wireless communication sensor was also developed using chipless radio frequency identification (RFID) technology. It is one of the widely used technique for internet-of-things (IoT) devices due to low-cost, printability, and simplicity. The developed stretchable and chipless RFID sensor exhibited GF more than 0.6 and maximum measurable range more than 0.2 with high degree-of-freedom of motion. Since it showed its original characteristics of sensing in only one direction independently, sensor patch composed of various sensor with different resonance frequency was capable of measuring not only normal strains but also shear strains in all directions. Sensors in machinery and equipment can provide valuable clues as to whether or not the actual values will fall into the tolerance range. In this aspect, a real-time, accurate, and reliable process monitoring is a basic and crucial enabler of intelligent manufacturing operations and digital twin applications. In this dissertation, developed sensor was used for various manufacturing process include forming process, milling process, and wireless communication using highly sensitive and wide measuring properties with low fabrication cost. It is expected that developed sensor could be applied for the digital twin and process defects prediction in real-time.4차 산업혁명에 대한 대부분의 논의는 많은 양의 데이터를 처리하고 평가하는 시스템을 암묵적으로 가정한다. 특히, 복잡한 생산 공정을 운영하기 위해서는 안정적이고 신뢰할 수 있는 데이터 측정 및 통신 시스템이 필요하다. 하지만, 최신 센서 기술은 광범위한 기계 및 생산 공정 중 데이터를 수집하는 것이 가능하지만 측정하기 쉽지 않은 데이터를 측정하고 분석하여 그 결과를 최적화된 생산 공정에 신속하게 제공하는데 한계를 가지고 있다. 때문에, 유연하고 적응 가능한 제조 공정을 위한 센서의 가격과 설치 방법, 데이터 수집 및 전송 시스템이 실제 산업의 요구 사항에 도달하지 못하고 있다. 이 학위 논문에서는 유연 기판에 전도성 및 신축성 패턴을 직접 인쇄할 수 있는 공기역학적 나노물질 집속 인쇄 시스템을 사용하여 높은 민감도와 넓은 측정 가능 범위를 가진 변위 및 진동 센서를 개발하였다. 구체적으로, 은 나노입자와 다중 벽 탄소 나노튜브로 구성된 나노 복합재를 폴리디메틸실록산 위에 직접 인쇄하였다. 유연 기판 위에 공기역학적 나노물질 집속 인쇄 시스템을 사용한 나노 복합재 인쇄 방법의 기작이 기계적 균열 발생, 시드층 적층, 부분 응집 및 완전 증착 순으로 논의 및 실험적으로 검증되었다. 인쇄된 나노 복합재 센서는 58.7의 게이지 팩터, 0.74의 측정 가능 범위를 나타내었으며 1,000번 반복된 수명 주기 평가에서 5% 미만의 정점 저항 변화를 확인할 수 있었다. 또한 Q 인자 평가 및 통계 검증을 사용하여 진동의 진폭 및 주파수에 따른 진동 측정 성능을 평가하였다. 나노 복합재 센서에 대한 측정 기작 또한 해석적 및 통계적 방법으로 분석되었다. 먼저, 나노물질 간 터널 효과가 이변량 프로빗 모델을 통해 통계적으로 분석되었다. 센서의 전기적 물성이 나노물질의 기하학적 물성에 따라 상이하기 때문에 변위에 따른 나노물질의 동적인 이해를 위해 레너드존스 전위 및 유권자 모델을 기반으로 한 몬테카를로 시뮬레이션 방법이 개발되었다. 이를 활용하여 나노물질 간 평균 부착 수를 계산하여 낮은 비용으로 전기전도도를 추정할 수 있었다. 첨단 제품을 제조하기 위한 모든 공정의 주요 목표는 지정된 범위의 허용 가능한 변동을 준수하는 것이다. 이를 위해 공정 중 어디에서나 상태 변경의 증거를 제공할 수 있는 모든 데이터를 기록하는 것이 필수적이다. 이 학위 논문에서는 제작된 센서를 통해 성형 및 절삭 공정의 데이터를 기록함으로써 공정을 모니터링하였다. 성형 공정 동안 스탬프의 기계적 변형을 측정함으로써 최대 힘, 힘의 구배 및 판금의 두께를 포함하는 다양한 공정 변수에 따라 성형 힘을 추정할 수 있었다. 또한, 절삭 공정 중 공작물에 제작된 센서를 직접 부착하여 정확하고 안정적인 진동 모니터링을 수행하였다. 얻어진 데이터의 주파수 및 전력 스펙트럼 분석을 이용하여, 분당 회전 수, 이송 속도, 스핀들의 절삭 깊이 및 너비에 따른 공작물의 진동을 측정하였다. 마지막으로 제조된 센서를 진동이 제품 품질에 큰 영향을 미치는 터빈 동익 제조 공정의 디지털 트윈으로 적용하여 실시간으로 공정 결함을 예측하였다. 유선 데이터 수집 및 전송 시스템을 극복하기 위해 칩리스 무선 주파수 식별 기술을 사용하여 직접 인쇄된 무선 통신 센서를 개발하였다. 칩리스 무선 주파수 식별 기술은 저비용, 인쇄성 및 공정의 평이성으로 인해 사물 인터넷 장치에 널리 사용되는 기술 중 하나이다. 개발된 유연한 칩리스 센서는 0.6 이상의 게이지 팩터와 0.2 이상의 측정 가능 범위를 나타냈다. 또한 제작된 센서는 한 방향의 변위만 독립적으로 측정할 수 있는 특성을 가지고 있기 때문에, 모든 방향의 수직 및 전단 변형을 측정할 수 있는 다양한 공진 주파수로 구성된 센서 패치가 개발되었다. 기계 및 장비의 센서는 실제 값이 공차 범위에 속하는지 여부에 대한 중요한 단서를 제공할 수 있다. 이러한 측면에서, 정확하고 신뢰할 수 있는 실시간 공정 모니터링은 지능형 제조 공정 및 디지털 트윈으로의 응용을 위한 기본적이고 결정적인 요소이다. 이 학위 논문에서 개발된 센서는 낮은 제조 비용과 높은 민감도 및 신축성을 가지고 있기 때문에 성형 공정, 절삭 공정, 무선 통신을 포함한 다양한 제조 공정에서 응용되었다. 뿐만 아니라 제작된 센서는 디지털 트윈 및 공정 결함의 실시간 예측을 위해 다양하게 사용될 수 있을 것으로 예상된다.Chapter 1. Introduction 1 1.1. Toward smart manufacturing 1 1.2. Sensor in manufacturing 4 1.3. Research objective 11 Chapter 2. Background 16 2.1. Aerodynamically focused nanomaterial printing 16 2.2. Printing system envelope 26 2.3. Highly sensitive sensor printing 34 Chapter 3. Sensor fabrication and evaluation 42 3.1. Highly sensitive and wide measuring sensor printing 42 3.2. Sensing performance evaluation 59 3.3. Environmental and industrial evaluation 87 Chapter 4. Sensing mechanism analysis 97 4.1. Theoretical background 97 4.2. Statistical regression anaylsis 101 4.3. Monte Carlo simulation 104 Chapter 5. Application to process monitoring 126 5.1. Forming process monitoring 126 5.2. Milling process monitoring 133 5.3. Wireless communication monitoring 149 Chapter 6. Conclusion 185 Bibliography 192 Abstract in Korean 211Docto

Proceedings of the 4th International Conference on Innovations in Automation and Mechatronics Engineering (ICIAME2018)

The Mechatronics Department (Accredited by National Board of Accreditation, New Delhi, India) of the G H Patel College of Engineering and Technology, Gujarat, India arranged the 4th International Conference on Innovations in Automation and Mechatronics Engineering 2018, (ICIAME 2018) on 2-3 February 2018. The papers presented during the conference were based on Automation, Optimization, Computer Aided Design and Manufacturing, Nanotechnology, Solar Energy etc and are featured in this book

Carbon nanotube bearings in theory and practice

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 157-170).Carbon Nanotubes (CNTs) are attractive elements for bearings in Micro-Electro-Mechanical Systems (MEMS), because their structure comprises nested shells with no bonding and sub-nanometer spacing between them, enabling relative motion with low friction and wear. A few demonstrations of CNT bearings have been reported in the literature, and atomistic simulations have been used to probe the properties of these bearings. This thesis extends the state of knowledge about these bearing systems, by building on these prior works in both the experimental and simulation domains. The prototype CNT rotor device presented in this thesis, and accompanying fabrication process, improve on existing CNT bearing demonstrators by establishing a vertical bearing orientation (enabling superior rotor balance and speed, and flexibility of placement for drive mechanisms) and a more manufacturable process (employing CNTs grown in place by chemical vapor deposition, and evaluating trade-offs in growth parameters). The device consists of a silicon rotor, supported on a cantilevered CNT shaft, and actuated by impingement of air jets on blades around its perimeter. For the fabrication development, extensive and consistent studies on the compatibility of CNTs with a suite of standard MEMS process were conducted, yielding valuable information for future CNT-based device designers on the effects of these processes on CNTs. Additionally, manual manipulation and placement of loose CNTs into the required vertical alignment was demonstrated, providing an alternate fabrication route, as well as a useful research technique for development of CNT devices. Simulation of friction in a CNT bearing system has been a popular topic, yet many questions remain open. For example, the quantitative estimates of this friction reported to date range by as much as eight orders of magnitude, and simulation techniques employ a variety of disparate simulation paradigms and parameters. This thesis presents a new suite of consistently implemented but complementary and independent simulations, which span the approaches reported to date, yet agree quantitatively within the error margin. Furthermore, the quantitative relationships between friction and sliding speed, temperature, geometry, and simulation implementation parameters are determined, and a description of the causes of friction based on phonon analyses is offered.by Eugene Hightower Cook.Ph.D

The Development of an Antagonistic SMA Actuation Technology for the Active Cancellation of Human Tremor.

Human Tremor is an unintentional bodily motion that affects muscle control among both healthy individuals and those with movement disorders, occasionally to severe detriment. While assistive devices avoid the risk of side effects from pharmacological or surgical treatments, most devices are impractical for daily use due to limitations inherent in conventional actuators. The goal of this research is to address these limitations by developing an antagonistic Shape Memory Alloy (SMA) actuation technology, enabling a new class of active tremor cancellation devices. This is accomplished through the construction of a model and body of empirical support that provides the necessary design insight and predictive power for an antagonistic actuator that ensures stable amplitude and high frequency motion with low power draw. Actuation frequency and power draw were improved while balancing their competing effects through the development of: 1) a method that accurately measures the convective coefficient of SMA to enhance actuator design, 2) a growth process for carbon nanotube cooling fins to enhance cooling in a fixed medium, and 3) an understanding of the antagonistic architecture to produce increased frequency in a controllable manner. To enable applications requiring predictability for positioning and complex control, a thermodynamic model for antagonistic SMA was derived to account for inertial, slack, boiling, friction, and convective effects. Using the model, a series of simulation studies provided design insight on the effect of operating environment, driving signal, and environmental conditions so that the generic actuation system can be utilized in a wide variety of applications beyond tremor cancellation. If high forces are required in such applications, stability issues can arise, which were addressed in experimental shakedown research that broadens the high-stress SMA design space. The technology enabled by this dissertation was demonstrated in a working Active Cancellation of Tremor (ACT) prototype that produced 71% RMS cancellation of human tremor. The cancellation results show significant improvement over the current state of the art by providing intuitive, lightweight, compact hand-held tremor cancellation that is a promising solution to numerous assistive applications in medical, military, and manufacturing sectors.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/76010/1/apathak_1.pd