Flexible Mount Research Articles

Research on the position of the neutral surface of the space lightweight mirror with two-axis bipod flexible mount

Research on the position of the neutral surface of the space lightweight mirror with two-axis bipod flexible mount

Analysis of the response of wind-induced vibrations on flexible photovoltaic mounts

Abstract This article investigates a flexible photovoltaic bracket’s response to wind vibration. A finite element model is established using SAP2000 software for time course analysis. Representative units and nodes were selected to analyze internal force response, displacement response, and acceleration response. The prestress and span change rule of the flexible photovoltaic bracket are also explored, and quantitative research is conducted on the size of prestress and span size. The magnitude of the prestress affects a structure’s responsiveness to wind vibration. As prestress grows, so do deflection and acceleration, and the rate at which axial force is increasing also increases. Conversely, when prestress increases, the rate of deflection reduction falls. Consequently, considering the prestress size, it is advised that 50-kN prestressing be used for the support and wind cables. As the span rises, so do the mid-span span and the axial force of the wind cables, while acceleration also increases. The rate of mid-span deflection increases gradually with the flexible PV mount span, but the rate of axial force increase decreases. It is recommended to limit the span to below 50 m.

A novel solder joints inspection method using curvature and geometry features in high-density flexible IC substrates surface mount technology

The automatic optical inspection based defective diagnosis systems in the surface-mounted device is fairly important to the optimization of electronic manufacturing. The gist of this paper is that presents a novel inspection system for the distinction of defective solder joints on the high-density flexible IC substrates. Initially, an ultra-high precision 3D information acquirement system is elaborated. Then, several critical sub-regions are divided and pivotal features are extracted from them, in which the differential geometry based estimation scheme to obtain discrete curvatures directly and the crest line representation based shape characterization method are proposed. Finally, each type of the solder joints is described with different and ordered feature sequences, and the practical classification process is formulated as the pattern recognition and classification problem, which is also implemented by the set of predefined diagnosis rules of thumb and the introduced logical operations. By classifying seven categories of industrial solder joints and exhaustively comparing with other state-of-the-art methods, the performances of the proposed diagnosis system is validated. Experimental results verify the effectiveness and efficiency of the developed system from three aspects, i.e. inspection speed, total correct rate, and detectable types.

Design and Fabrication of Piezoelectric Artificial Cilia for Airflow Sensing in Mobile Robot with Surface Mount

In order to realize the measurement of airflow velocity in narrow spaces, we fabricate, package and characterize a flexible and surface mount piezoelectric artificial cilia (PAC) for airflow sensing in a piezoelectric mobile robot (PMR). The diameter and height of the cilia are 0.3 mm and 5 mm, respectively, whose sensitivity is 30 (mV)/(m/s). Meanwhile, the PMR is 32.8 g in mass and 55 mm × 50 mm × 20 mm in size and it is capable of achieving a velocity of 200 mm/s. This sensing robot has advantages of light weight, miniature size, and low cost, which has potential to effectively evaluate air leakage in the pipeline.

Enabling paper-based flexible circuits with aluminium and copper conductors

Implementing electronics systems on paper is an important area of flexible circuit technologies. One of the approaches is to print conductive inks onto paper substrates, on which silicon-based surface mount device components are mounted. However, one of the problems is that the printed conductors have unneglectable resistivity. In this paper, we present paper-based flexible circuits, using copper and aluminium conductors that are laminated onto paper substrates using a high-speed roll-to-roll method. Edge roughness inspections and repeated two-point bending tests are carried out to evaluate the manufactured flexible circuits. Three surface mount techniques are used to assemble standard surface mount device components onto the flexible circuits, including an isotropic conductive adhesive, an anisotropic conductive adhesive, and a low-temperature solder paste. Several characterizations are performed to the surface mount techniques, including contact resistance measurements, component bonding strength tests, assembled circuit bending tests, and scanning electron microscopy. The results of the characterizations suggest that flexible circuits made from Cu with paper substrate achieve satisfactory results for mechanical reliability, all surface mount techniques, and have the potential to be used on automatic component assembly lines. In order to test whether such flexible circuits and surface mount techniques can be used in implementing electronics systems, passive NFC tags with relative humidity sensing functionality are made, which are interrogated by an NFC equipped mobile phone.

Dynamic modeling of an eccentric face seal including coupled rotordynamics, face contact, and inertial maneuver loads

Mechanical face seals are constitutive components of turbomachines, which in turn can be constitutive to other systems (e.g. aircraft). Furthermore, the rotating element of a face seal is inextricably coupled to the turbomachine via a flexible mount, and the stationary seal element is coupled to the rotating seal element via the fluid film existing between the seal faces. Consequentially, understanding interactions between the seal and turbomachine is important for quantifying seal performance and improving its design. With few exceptions, previous works study the face seal dynamics independent from the rotordynamics. In addition, most prior investigations consider only angular and axial seal dynamics and neglect eccentric (i.e. lateral) deflections of the seal element(s). For the first time, this work develops a comprehensive and novel model of a mechanical face seal in the inertial reference frame including coupled rotordynamics and inertial maneuver loads of the overall system. The model is developed for a general seal geometry where both seal elements, stationary and rotating, are flexibly mounted and allowed to undergo angular, axial, and eccentric deflections. In addition, the seal model presented here accounts for transient operation, fluid shear forces, seal face contact, friction, and thermoelastic deformation. Finally, various faults due to manufacturing imperfections, component flaws, and/or installation errors can be accounted for by incorporating static angular misalignment of both seal elements, dynamic angular misalignment of the rotating seal element, eccentric rotating imbalance, and axial offset of the rotating seal element center of mass. Throughout this work, the equations of motion developed are valid for both steady-state and transient operation. This comprehensive model significantly advances the state of the art in mechanical face seal dynamic modeling and represents a pivotal step towards analyzing seal performance regarding a broad diversity of realistic problems.

VIBRATION ANALYSIS OF A FLAT PLATE UNDER AERODYNAMIC LOADING

Aeroelastic instabilities may occur in aircraft surfaces, leading to fatigue or structure failure. Flutter is an aeroelastic instability that results in a self-excited divergent oscillatory behavior of the structure. A classical two-degree-of-freedom flutter is a combination of bending and torsion vibration modes. A flexible mount system has been developed for flutter tests with rigid wings in wind tunnel. This flexible mount has to provide a well-defined two-degrees-of-freedom system on which rigid wings encounter flutter. Experi-mental Modal Analysis (EMA) and Finite Element Model Analysis (FEM) were performed to verify the natural frequencies and modes prior to any wind tunnel flutter test. The equations of motion of the system were developed using Lagrange's equation. The critical flutter speed was determined by three different methods: the p-method for steady flow, the classical flutter analysis and the k-method for unsteady flow, and comparing with experimental results. قد يحدث عدم الاستقرار في أجنحة الطائرات مما يؤدي إلى الکسر او انهيار الهيکل بالکامل. وتعتبر الرفرفة أکثر أنواع عدم الاستقرارالتى تنشأ من التداخل بين قوى الهواء، والمرونة، وقوى القصور الذاتي. ولدراسة هذه الظاهرة نحصل على درجتان من درجات الحرية وهما عزم الثنى وعزم الالتواء وذلک عن طريق وضع انظمة مرنة وأخرى جاسئة ، ويتم وضع هذا النظام فى نفق هواء وذلک للحصول على هذه الظاهرة .ويتم استنتاج معادلات الحرکة عن طريق معادلة لاجرانج. ويتم حساب سرعة الهواء التى تحدث عندها هذه الظاهرة باستخدام ثلاثة طرق مختلفة، واحدة فى تدفق منتظم للهواء، والاثنان الأخريان فى تدفق غير منتظم للهواء

CFD simulation of a 2 bladed multi megawatt wind turbine with flexible rotor connection

An innovative passive load reduction concept for a two bladed 3.4 MW wind turbine is investigated by a conjoint CFD and MBS - BEM methodology. The concept consists of a flexible hub mount which allows a tumbling motion of the rotor. First, the system is simulated with a MBS tool coupled to a BEM code. Then, the resulting motion of the rotor is extracted from the simulation and applied on the CFD simulation as prescribed motion. The aerodynamic results show a significant load reduction on the support structure. Hub pitching and yawing moment amplitudes are reduced by more than 50% in a vertically sheared inflow. Furthermore, the suitability of the MBS - BEM approach for the simulation of the load reduction system is shown.

A Novel Eye-Gaze-Controlled Wheelchair System for Navigating Unknown Environments: Case Study With a Person With ALS

Thanks to advances in electric wheelchair design, persons with motor impairments due to diseases, such as amyotrophic lateral sclerosis (ALS), have tools to become more independent and mobile. However, an electric wheelchair generally requires considerable skill to learn how to use and operate. Moreover, some persons with motor disabilities cannot drive an electric wheelchair manually (even with a joystick), because they lack the physical ability to control their hand movement (such is the case with people with ALS). In this paper, we propose a novel system that enables a person with motor disability to control a wheelchair via eye-gaze and to provide a continuous, real-time navigation in unknown environments. The system comprises a Permobile M400 wheelchair, eye tracking glasses, a depth camera to capture the geometry of the ambient space, a set of ultrasound and infrared sensors to detect obstacles with low proximity that are out of the field of view for the depth camera, a laptop placed on a flexible mount for maximized comfort, and a safety off switch to turn off the system whenever needed. First, a novel algorithm is proposed to support continuous, real-time target identification, path planning, and navigation in unknown environments. Second, the system utilizes a novel N-cell grid-based graphical user interface that adapts to input/output interfaces specifications. Third, a calibration method for the eye tracking system is implemented to minimize the calibration overheads. A case study with a person with ALS is presented, and interesting findings are discussed. The participant showed improved performance in terms of calibration time, task completion time, and navigation speed for a navigation trips between office, dining room, and bedroom. Furthermore, debriefing the caregiver has also shown promising results: the participant enjoyed higher level of confidence driving the wheelchair and experienced no collisions through all the experiment.

Two-step transfer function calculation method and asymmetrical piecewise-linear vibration isolator under gravity

Piecewise-linear isolators are widely used in spacecraft for satisfying ever more stringent vibration requirements of high precision payloads. This paper focuses on ground tests of such isolators, with special consideration of gravitational asymmetry and mount flexibility. With asymmetrical equivalent isolator parameters derived with the extended equivalent linearization method, a two-step transfer function calculation method is proposed for enhancing the computation efficiency in dealing with studies where huge amount of computations are required, such as design parameter studies. The asymmetrical effect due to the gravity is presented by the movement of dynamic equilibrium positions as well as the softening and hardening characteristics of frequency responses. The effects and differences of the rigid mount and flexible mount, which respectively correspond to the shake table test and the whole spacecraft structure ground test, are studied with various design parameters. Numerical results show that the preload is an important factor in determining such effects and differences.

Selection of the optimal configuration for a flexible surface mount assembly system based on the interrelationships among the flexibility elements

Flexibility has been widely recognized as a key competitive factor for manufacturing firms coping with the increasingly turbulent manufacturing environment today. Establishing a flexible surface mount assembly (SMA) system is critical for organizations to achieve a cost-effective assembly and gain competitive advantages in the printed circuit board (PCB) assembly industry. To find a practicable operating strategy, a multi-criteria decision-making framework that combines the analytic network process (ANP) with the consistent fuzzy preference relations (CFPR) is proposed to explore the interrelationships among the six dimensions and twenty-one criteria of manufacturing flexibility and resolve the uncertainty and divergence between decision-makers with the least amount of pairwise comparisons. Based on the results of prior analysis, an optimum configuration of a flexible SMA system is suggested for the capacity investment intended by a Taiwan electronics manufacturing service (EMS) provider to quickly respond to dynamic production requirements.

Estimating the operation time of flexible surface mount placement machines

Gantry type component placement machines are widely used in electronics industry due to their accuracy, speed and flexibility. In order to make optimal plans of their usage one has to know the manufacturing time of a given component placement work before the actual processing. This presupposes the use of a reliable machine simulator. In the present article, discrete-event simulation is applied to predict component placement times of gantry type machines. The generic simulator model is based on a circumstantial analysis of the time factors by the means of observing and measuring the times of operations performed by the machine. As a result of this, very high accuracy is achieved; the operation times predicted by the simulator are for a particular machine type (Universal Instruments GC-60D) in range ±1 % from the observed operation times.

서보라이트 픽스쳐의 진동 특성 개선 방법

This paper presents a method to improve vibration characteristics of servo track write (STW) fixture. STW fixtures supported by flexible mounts are subject to various vibration sources. Using Finite element analysis (FEA) vibration modes of the fixture are identified. The FEA results suggest certain vibration modes be reduced through design change of flexible mounts to improve vibration responses of the fixture. Based on layered flexible mounts theory a parametric study on shear and bending stiffness is performed to obtain a suitable flexible mount design leading to increased resistance to rocking motion. Experiments confirm improvement of vibration characteristics and drive performance through new mounts design.

Towards a 3-D tomographic retrieval for the air-borne limb-imager GLORIA

Abstract. GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) is a new remote sensing instrument essentially combining a Fourier transform infrared spectrometer with a two-dimensional (2-D) detector array in combination with a highly flexible gimbal mount. It will be housed in the belly pod of the German research aircraft HALO (High Altitude and Long Range Research Aircraft). It is unique in its combination of high spatial and state-of-the art spectral resolution. Furthermore, the horizontal view angle with respect to the aircraft flight direction can be varied from 45° to 135°. This allows for tomographic measurements of mesoscale events for a wide variety of atmospheric constituents. In this paper, a tomographic retrieval scheme is presented, which is able to fully exploit the manifold radiance observations of the GLORIA limb sounder. The algorithm is optimized for massive 3-D retrievals of several hundred thousands of measurements and atmospheric constituents on common hardware. The new scheme is used to explore the capabilities of GLORIA to sound the atmosphere in full 3-D with respect to the choice of the flightpath and to different measurement modes of the instrument using ozone as a test species. It is demonstrated that the achievable resolution should approach 200 m vertically and 20 km–30 km horizontally. Finally, a comparison of the 3-D inversion with conventional 1-D inversions using the assumption of a horizontally homogeneous atmosphere is performed.

Manufacturing defect in a single use flexible catheter mount

Manufacturing defect in a single use flexible catheter mount

Doppler Optomechanics of a Photonic Crystal

A laser beam directed at a mirror attached onto a flexible mount adds friction to its mechanical motion by the Doppler effect. For a normal mirror the efficiency of this radiative Doppler friction is very weak and practically masked by laser shot noise. We find that it can become very efficient using a photonic crystal mirror near its photonic band gaps. As an example, a Bragg mirror used at the long wavelength edge of its band stop can be efficiently optically cooled using the Doppler friction. The opposite effect opens new routes for optical pumping of mechanical systems: a laser pointing at a Bragg mirror and tuned at its short wavelength edge induces amplification of the vibrational excitation of the mirror leading eventually to its self-oscillation. These new effects rely on the strong dependency of a photonic crystal reflectivity on the wavelength.

Design of an experimental flutter mount system

Aeroelastic instabilities may occur in aircraft surfaces, leading then to failure. Flutter is an aeroelastic instability that results in a self-sustained oscillatory behaviour of the structure. A two-degree-of-freedom flutter can occur with coupling of bending and torsion modes. A flexible mount system has been developed for flutter tests in wind tunnels. This apparatus must provide a well-defined 2DOF system on which rigid wings encounter flutter. Simulations and Experimental Tests are performed during the design period. The dimensions of the system are determined by Finite Element analysis and verified with an Aeroelastic Model. The system is modified until first bending and torsion modes become the first and second modes and other modes become higher than these. After this, a Modal Analysis is performed. An identification algorithm, ERA, is used to determine modes shape and frequencies from experimental data. Detailed results are presented for first bending and torsion modes, which are involved in flutter. The flutter mechanism is demonstrated by Frequency Response Functions obtained in several wind tunnel velocities until flutter achievement and by a V-g-f plot obtained from an identification process performed with an extended ERA. Mode coupling, damping behaviour and the self-sustained oscillatory behaviour are verified characterising flutter.

A tactile stimulus applied to the leg improves postural stability in young, old and neuropathic subjects

The purpose of this study was to determine whether the application of passive tactile cues to the lower limb could improve postural stability in healthy young controls, older people and people with diabetic peripheral neuropathy. Antero-posterior sway was measured with eyes open and closed in 10 healthy young subjects (mean age 27 years, 5 male, 5 female), 10 older subjects without diabetic peripheral neuropathy (mean age 88 years, 2 male, 8 female) and 10 subjects with diabetic peripheral neuropathy (mean age 65 years, 6 male, 4 female) while a small piece of Velcro ® attached to a flexible mount was applied to three different sites on the leg (ankle, calf, and knee). Across all conditions, the mean sway of the neuropathic subjects was 93% greater than for the young subjects and 11% more than the older subjects. On average, subjects swayed 10% more with the eyes closed than with the eyes open. Each stimulus reduced sway, but the effect increased approximately in proportion to the height of the stimulus above the ankles (ankle 7.6%, calf 13.5%, knee 20.1% reduction compared to the no stimulus condition). This experiment demonstrates that a passive stimulus applied to the skin of the leg, which provides sensory information about body movement, significantly reduces body sway during standing. This applies to older subjects and subjects with peripheral neuropathy as well as healthy young subjects. These results have implications for novel approaches for improving stability in people with peripheral sensory loss.

Dynamic Analysis of Rigid-Body Mechanisms Mounted on Flexible Support Structures — Planar Case

Computer-aided analysis of rigid-body mechanisms is combined with the finite element analysis of flexible structures to develop a computer model and derive the equation of motion, incorporating the Lagrange multiplier, to be used in the dynamic analysis of multi-rigid-body mechanisms mounted on flexible support structures. The resulting equations are solved by numerical integration. Predicting and analyzing the performance of the full system, including the motion of the system components and the forcing condition, during the engineering design process will promote the success of the entire system. Finally, a machine gun system with a flexible mount is given as a numerical example. The results reveal that the interaction between the rigid-body mechanisms and its flexible support structures importantly determines the performance of whole system. This study considers only the planar case. Our future work will propose a more complicated fully three-dimensional model.

A flutter suppression active controller

Flutter is a dynamic aeroelastic instability that involves the interaction of aerodynamic, elastic, and inertial forces. This instability may occur in aircraft surfaces, like wings and tails, leading them to a divergent oscillatory motion. A classical two-degrees-of-freedom flutter is an interaction of bending and torsional modes of vibration of a structure. A flexible mount system has been developed for flutter tests with rigid wings in wind tunnels. This flexible mount has to provide a well-defined two-degrees-of-freedom system on which rigid wings encounter flutter. Active control schemes for flutter suppression can be tested using this experimental set-up. An aeroelastic model is formulated to simulate the aeroelastic behaviour of this system. The equations of motion are developed using Lagrange' equations and the Principle of Virtual Work, resulting in a state space representation. This is a convenient way to determine pitch and plunge time responses for several initial conditions and velocities. Using this model, a state feedback controller of the form u = – Kx is determined. The wind tunnel model is a rectangular wing with a NACA 0012 airfoil section and a trailing edge control surface as actuator. The main goal is to suppress flutter and to maintain the stability of the closed loop system.