Cantilever Structure Research Articles

Fuzzy logic based active vibration control using novel photostrictive composites

Although conventional actuators like piezoelectric and electrostrictive are efficient, but they required hard wiring, which contaminates the control signal and adds to the weight of the structure. The current study presents a wireless control strategy using photostrictive actuators. Owing to the fortunate combination of photovoltaic effect and converse piezoelectric effect, a photostrictive actuator can generate mechanical strain, when irradiated with light intensity. Limited choices of photostrictive material with high electromechanical coupling coefficient give the motivation to design photostrictive composites. The finite element-based formulation incorporating fuzzy logic controller is employed to study the active vibration control response of cantilever structure when equipped with photostrictive composite actuator. A parametric study has been carried out to study the influence of inclusion’s volume fraction on wireless active vibration control of the structure. Control merits have been defined to compare the control performance of different composites. It is found that particulate composites are the better choice for lightweight structure and fiber composites are better if there is no weight constraint.

Model and experimental analysis of a rotor rig dynamics with time-varying characteristics

This work is motivated by the rapid developments of a broad range of electrically powered vertical take-off and landing vehicles which frequently feature two-bladed thrust generating rotor propulsion units. The interaction between a two-bladed rotor and the surrounding structure causes an emergence of the complex dynamics specific to the systems with the time-varying characteristics. This paper introduces a new rotor-structure test rig aimed to support the focused analyses of such systems. The test rig is realized as an idealised configuration consisting of a flexible slender cantilevered beam-like support structure which accommodates a single brushless electrical motor and a two-bladed propeller at its free end. Whilst retaining relative simplicity and scalability, this system allows analysis of complex flexible structure-propeller coupled phenomena, some of which are evidenced in this study. To form a compact and fully defined low-order model suitable for the computationally efficient in-vacuo analysis presented here, a Lagrange-based energy formulation is used to derive the equations of motion. The frequency and time domain techniques, including the complex modal analysis of the linear time-periodic systems, frequency response function and Udwadia-Kalaba method, are used to describe and explain the observed dynamics. The predicted dynamic changes, their impact on the modal interactions and the validity of the finite-sized time-invariant approximating system are successfully demonstrated through correlation with the experiment in the frequency range which encompasses the first four modal families and the rotor speed range spanning up to the first observed experimental instability. Specifically, the study confirms the occurrence of the modal veering and lock-in phenomena, modal splits as well as the strong dominance of the 0th order frequency modulation clusters in the structural response. The results presented in this work show that the proposed experimental platform represents a useful minimal dynamic system with the behavioral characteristics of high significance for the design of novel electrically powered and propeller-driven aircrafts.

Investigation of Aeroelastic Energy Extraction from Cantilever Structures under Sustained Oscillations

The present article is focused on a detailed computationalinvestigation of energy production capacity of various lightweight materials that are employed with piezoelectric vibration energy harvesters (PVEHs) subjected to various aeroelastic effects. Piezoelectric transducers are primarily employed to capture vibrational energy, which yields predictable and locally storable electrical energy. Higher energy extraction is possible under larger deflections of the structures when they are employed with PVEHs. In order to estimate the largest possible deflection of the structures, the response of them under external perturbations is estimated. An airplane wing consists of tapered planform, an advanced wind turbine blade, and the rectangular wings of an unmanned aerial vehicle (UAV) are considered for the vibrational analysis as the feasibility of achieving larger deflection is high compared with other aerodynamic surfaces. The stated elastic structures are modelled with different lightweight materials such as aluminium alloy, glass fibre-reinforced polymer (GFRP), titanium alloy, carbon fibre-reinforced polymer (CFRP), and Kevlar fibre-reinforced polymer (KFRP). Advanced partly coupled computational simulations are carried out with computational fluid dynamics (CFDs), and structural and vibrational effects to investigate the energy harvesting potential from the perturbations. Based on the outcomes of vibrational analysis, the raw transformable power production capacity of different lightweight materials that are employed with a cantilevered PVEH is estimated. The most suitable combination of material and associated aeroelastic effect which yields a significant amount of raw energy in each application is proposed and discussed with findings.

Research on AlN thin film microstructure processing technology based on ultra-thin cantilever beam structure

Aiming at the problem of poor solution selection ratio when the AlN film and porous silicon sacrificial layer are released in the ultra-thin cantilever structure and at the problem of large surface roughness after AlN graphing, the wet corrosion process parameters were optimized, and the influence of different corrosive fluids and corrosion times on the surface roughness of AlN and the influence on the etching rate of AlN were studied, and different process parameters were selected for experiments. According to the experimental results, a suitable microstructure processing method was selected to effectively reduce the surface roughness of AlN and improve the integrity of the AlN film and the reliability and yield of the cantilever structure when the sacrificial layer is released. The microstructure fabrication of AlN films in ultra-thin cantilever structures enables the fabrication of ultra-micro-force sensors, accelerometers, acoustic sensors, and other devices.

Creep Properties and Analysis of Cross Arms' Materials and Structures in Latticed Transmission Towers: Current Progress and Future Perspectives.

Fibre-reinforced polymer (FRP) composites have been selected as an alternative to conventional wooden timber cross arms. The advantages of FRP composites include a high strength-to-weight ratio, lightweight, ease of production, as well as optimal mechanical performance. Since a non-conductive cross arm structure is exposed to constant loading for a very long time, creep is one of the main factors that cause structural failure. In this state, the structure experiences creep deformation, which can result in serviceability problems, stress redistribution, pre-stress loss, and the failure of structural elements. These issues can be resolved by assessing the creep trends and properties of the structure, which can forecast its serviceability and long-term mechanical performance. Hence, the principles, approaches, and characteristics of creep are used to comprehend and analyse the behaviour of wood and composite cantilever structures under long-term loads. The development of appropriate creep methods and approaches to non-conductive cross arm construction is given particular attention in this literature review, including suitable mitigation strategies such as sleeve installation, the addition of bracing systems, and the inclusion of cross arm beams in the core structure. Thus, this article delivers a state-of-the-art review of creep properties, as well as an analysis of non-conductive cross arm structures using experimental approaches. Additionally, this review highlights future developments and progress in cross arm studies.

Vibration Control of a Dynamic Structure Using PLZT Sensor and Actuator with Temperature Variation

Piezoelectric material PLZT exhibits non-linearity in the dielectric constant and piezoelectric strain coefficient with respect to the temperature. In this paper, the active vibration control technique is employed on a cantilevered plate structure using PLZT piezoelectric material as a sensor as well as an actuator. The variation in dielectric constant and piezoelectric strain coefficient with change in temperature is considered while actively controlling the vibrations of the plate instrumented with PLZT patches. The finite element modeling of the structure is done using Hamilton’s principle. The modified constitutive equations of piezoelectric material PLZT are included for dielectric constant and piezoelectric strain coefficient with respect to the temperature variation. The vibrations are sensed by one piezoelectric patch at different ambient temperatures ranging from 27 °C to −15 °C. The negative velocity feedback control law is used for the active vibration control of the structure. The second piezoelectric patch is used as an actuator in the same temperature range of 27 °C to −15 °C. The experiments are performed for two cases: in case 1 the effect of temperature on dielectric constant and piezoelectric strain coefficient is ignored in the control law for active vibration control of the structure. In case 2 the effect of temperature on dielectric constant and piezoelectric strain coefficient is considered in the control law. In this work, the active vibration control of a dynamic structure is achieved by using PLZT piezoelectric material with the variation in ambient temperature.

Time-dependent dynamic response of cylindrical 2D-FG spinning microbeam based on different high-order beam theories applying the GDQEM and Newmark-beta techniques

The nonlocal influence on the cantilever constructions varies significantly. Some researchers feel that nonlocal cantilever structures predict stiffness hardening features; others argue that nonlocal cantilever models cause dynamic softening. In this regard, the vibration behavior of a spinning cylindrical cantilever imperfect functionally graded beam structure is analyzed using several mathematical models based on the nonlocal strain gradient theory. More specifically, higher-order shear deformation theories are investigated in the current study. In addition, the effect of boundary condition modeling is presented. Boundary conditions could be modeled with nonlocal effects or as a classical boundary condition. The governing equations are solved using a technique called generalized differential quadrature element (GDQE) method. The findings of a frequency analysis and a dynamic deflection study, both of which are impacted by a variety of diverse factors, are presented and analyzed. Specifically, the effects of boundary condition model selection are investigated in detail. The findings proved that nonlocality in boundary conditions caused the softer behavior of the cylindrical beam structure by decreasing the natural frequency. On the other hand, using different beam models and boundary conditions could result in a complete difference in obtained results.

Nozzle-based precision patterning with micro-/nano fluidics integrated cantilevers

As the requirements of micro-/nano printing technologies are continuously increasing, direct writing technologies on a submicron scale are drawing attention. One of the promising methods is a nozzle-based precision patterning with atomic force microscopy (AFM), which has the advantages of high position controllability including nozzle-to-substrate distance feedback under a nanometer scale. It uses a fluidic channel and a dispensing nozzle integrated with a cantilever structure for deflection monitoring. In this paper, we introduce micro/nanofluidics integrated cantilevers for nozzle-based precision patterning in several considerations: 1) numerous fabrication strategies for nozzle-integrated fluidic cantilevers; 2) methods for liquid transport; 3) methods for pattern formation; and 4) applications with various printing materials.

Force and stability mechanism analysis of two types of nonlinear mono-stable and multi-stable piezoelectric energy harvesters using cantilever structure and magnetic interaction

Nonlinear mono-stable and multi-stable piezoelectric energy harvesters have attracted a lot of attention owing to their broadband frequency spectra and excellent energy harvesting performance. Herein, two types of nonlinear mono-stable, bi-stable, tri-stable, and quad-stable piezoelectric energy harvesters using cantilever structure and magnetic interaction are compared and analyzed. Based on the magnetizing current method, the magnetic force equations are obtained. Calculation results demonstrate that the stability of these harvesters is dependent on the equivalent linear elastic force and the vertical magnetic force. The equilibrium point occurs when the equivalent linear elastic force equals to the vertical magnetic force. The relationship between the number of stable equilibrium points E S and the number of the intersections of the two force curves N I is that E S= (N I + 1)/2. Experiments are carried out to verify the equivalent linear elastic force, vertical magnetic force, and the number of stable equilibrium points of the fabricated prototypes. The experimental results are consistent with the calculated results, which verifies the correctness of the stability mechanism. Moreover, it is found that the stability mechanism is also applicable to the harvesters with more stable equilibrium points, such as penta-stable and hexa-stable harvesters. This work reveals the stability mechanism of nonlinear mono-stable and multi-stable energy harvesters using cantilever structure and magnetic interaction, and provides technical methods for the design of multi-stable energy harvesters.

Design and simulation of piezoelectric MEMS logic gates

In this article, MEMS-based logic gates such as OR, AND, NOT, NOR, and NAND gates with functionalities similar to the electronic digital devices are designed and simulated. The key feature of these logic devices is that the mechanical cantilever structure of the basic piezo-actuator is adapted to operate like a particular digital logic gate based on the digital inputs. Complete analytical modelling for a single piezo-actuator with a correlation between its out-of-plane tip deflection with applied voltage is obtained. The proposed digital logic devices are further validated through simulation using the MEMS CAD tool CoventorWare.

Cold Formed Steel Type C On Beams With Connection Variations

The disadvantages of using cold rolled steel (cold formed steel) include a thin profile and low stiffness of the connecting parts. Stiffness research of various types of joints is needed to study element failure, machine error or connection failure which causes the collapse of cold rolled steel structures. Analysis is needed for cantilever structures, because the maximum deflection that occurs in cantilever structures is greater than that of simply supported beam structures. The shape and type of cold rolled steel joints greatly affect the stiffness and stability of cold rolled steel structures so that the strength of several types of joints must be studied. The purpose of this study was to analyze the stiffness of the test results under the influence of bending loads on each type of cold rolled steel beam-column connection. Cold steel C channel profile with a thickness of 0.75 mm is used as the object in this study. The beam-column structure is assembled with various kinds of connections, including direct screw connections, screw-gusset plates, screw-angle plates, and screw-angle plate-gusset plates. This research shows addition of the elbow plate increases the strength of the test object by means of a screw connection and gusset plate to the load. However, the results of the maximum load in the experiment still have not reached the maximum load of the analysis results. In the screw connection the damage that occurs is tearing in the connecting plate (tear out), in the gusset plate connection the damage that occurs is the collapse of the gusset plate, in the screw-angled plate connection there are 2 damages, where the damage starts with a tear in the connecting plate ( tear out) and followed by damage to the screw that is damaged (pull out).

Energy Harvesting from Vibrating Cantilever Structure of Different Base Materials using Piezoelectric Material: Theoretical and Experimental Approach

Energy conversion from one form to the other forms the basis for many inventions. Non utilized energy of mechanical vibration has attracted many researchers to focus on energy harvesting from vibrating structures. Piezoelectric material when attached to a vibrating structure converts mechanical energy into electrical energy. Today, harvesting energy ranges from micro level to macro level and has obtained its importance in wide range of real time application such as from low powered electronic devices to solar, wind and hydroelectric energy systems, respectively. The current work presents a detailed theoretical and experimental study on a cantilever type beam structure embedded with piezoelectric material on different base materials to understand micro level energy harvesting. Euler Bernoulli beam theory based mathematical model is excited with an impulse load at the free end for a broader frequency spectrum analysis. Finally, the proposed energy harvesters, cantilever specimens of three different base materials are ranked based on their maximum voltage and maximum instantaneous power outputs experimentally for the given impulse excitation. Out of three base materials considered steel and copper-based energy harvesters generated a maximum voltage output of 0.16mV and 0.13mV, respectively which corresponds to a maximum instantaneous power output of approximately 1.96nW and 1.69nW, respectively. Aluminum-based energy harvester performed the least among the three contributing to 0.81nW.

Output Estimation and Failure Detection in Cantilever Bimorph Actuator Using Transmissibility Operators

Abstract In this article, we investigate how to identify faulty sensors in piezoelectric actuators used for precise positioning. Four sensors are distributed along the actuator’s cantilever structure to measure the deflection (displacement) at various points. We suggest identifying the sensor and detecting the fault in one of the sensors, which is thought to be faulty or producing a degraded signal. To address this, we suggest using transmissibility operators, which are mathematical estimators that estimate sensor measurements based on another set of sensor measurements within the same system. This estimation is highly robust against any external excitations/disturbances, as well as any unknown nonlinearities or unmodeled dynamics. The estimation robustness allows failure detection to be carried out even in significant actuator hysteresis nonlinearity and outside disturbance. Simulation results with various sensor fault conditions verified the suggested strategy.

Development and Optimization of a Two-Degree-of-Freedom Piezoelectric Harvester Based on Parallel Cantilever Structure With Magnetic Coupling

Development and Optimization of a Two-Degree-of-Freedom Piezoelectric Harvester Based on Parallel Cantilever Structure With Magnetic Coupling

Production of piezoelectric cantilever using MEMS-based layered manufacturing technology

Piezoelectric cantilever is widely preferred in many fields due to its small size, simple and perfect design, easy control process, easy integration with integrated circuits. The tip displacement is the most important character of piezoelectric cantilever and many models have been used for characterization. These models are only suitable for piezoelectric cantilever structures of the same length and layer thickness. In this study, a new model is proposed to estimate the tip displacement of a micro-electro-mechanical system (MEMS) based piezoelectric cantilever with layers of different lengths and thicknesses. Modeling was carried out in COMSOL Multiphysics software in 3D format with reference to the bimorph structure. The fabrication of the piezoelectric cantilever was made by Stereolithography (SLA), which is one of the additive manufacturing methods. Theoretical, simulated and real-time experiments were carried out to measure the tip displacement of the piezoelectric cantilever. An electrical characterization experiment was set up to measure tip displacement under constant voltage of the cantilever in real-time experiments. This setup includes an optical microscope and digital camera to observe displacements in the probe station. As a result of the characterization, it was found that the cantilever produced a maximum 14.98 µm tip displacement of 900 µm length, 225 µm width and 40 µm thickness under 10 V voltage. In addition, it has been determined that the tip displacement of the piezoelectric cantilever is directly proportional to the length and inversely proportional to the layer thickness. The results show that the model is in good agreement with the finite element method (FEM) simulation, theoretical and experimental measurements.

Structural Optimization and Mechanical Simulation of MEMS Thin-Film Getter-Heater Unit.

A MEMS thin-film getter-heater unit has been previously proposed for the vacuum packaging of a Micro-Electro-Mechanical System (MEMS) device, where the floating structure (FS) design is found to be obviously more power-efficient than the solid structure (SS) one by heat transfer capacity simulation. However, the mechanical strength of the FS is weaker than the SS by nature. For high temperature usage, the unit structure must be optimized in order to avoid fracture of the cantilever beam or film delamination due to strong excessive stress caused by heating. In this paper, COMSOL is used to simulate the stress and deformation of the MEMS thin-film getter-heater unit with the cantilever structure. By comparing various cantilever structures, it is found that a model with a symmetrically-shaped heater and edge-center-located cantilever model (II-ECLC model) is the most suitable. In this model, even when the structure is heated to about 600 °C, the maximum stress of the cantilever beam is only 455 MPa, much lower than the tensile strength of silicon nitride (Si3N4, 12 GPa), and the maximum deformation displacement is about 200 μm. Meanwhile, the interfacial stress between the getter and the insulating layer is 44 MPa, sufficiently lower than the adhesion strength between silicon nitride film and titanium film (400-1850 MPa). It is further found that both the stress of the cantilever structure and the interfacial stress between the getter and the insulating layer beneath increase linearly with temperature; and the deformation of the cantilever structure is proportional to its stress. This work gives guidance on the design of MEMS devices with cantilever structures and works in high temperature situations.

ICANTILEVER ARCHITECTURAL STRUCTURES OF MODERN BUILDINGS AND STRUCTURES WITH A UNIQUE IMAGE OF OVERCOMING GRAVITY

The article reveals the features of cantilever architectural structures on a number of examples from foreign and domestic author's architecture. The article reveals the features of cantilever architectural structures on a number of examples from foreign and domestic author's architecture. Architectural cantilever structures create a unique imagery of overcoming gravity and ignoring the static laws of building mechanics. Therefore, with the development of architectural and construction engineering technologies, modern architects have exceptional opportunities for designing buildings and structures with cantilever volumes of considerable size and weight. The objects of foreign and domestic architecture given in the article speak of the close collaboration of architects and designers, when the complex and laborious search for a special imagery of cantilever structures is inextricably linked with the tasks of a sustainable balance of extraordinary cantilever structures. From the given structural diagrams and volumetric compositional solutions of cantilever architecture objects, the following stand out: inclined "falling" type; solution in the form of a cantilever "loop"; "folding" of elongated buildings with cantilever extensions; "pulling" V -shaped in terms of design in a significant console. At the present stage in architectural and construction practice, such issues of the use of cantilever structures as: research in terms of optimizing their mass, taking into account stability; features of the impact of the design of cantilever structures in modern architecture; analysis of the structural safety of cantilever elements in conditions of extreme wind; cantilever structures in modern construction, etc. Images of buildings and structures that contradict the laws of statics become the leading volumetric compositional solution in a number of buildings of modern architecture.

Non-coplanar misalignment optical waveguide cantilever sensor with a monotonic response in a large operation range.

This paper reports a non-coplanar misalignment optical waveguide cantilever sensor realizing a monotonic response with a large operation range. A 1×2 Y-branch optical power splitter cantilever structure was designed, and one of the branches was reduced in thickness at the end, as a non-coplanar structure with respect to another. The misalignment coupling of the two branches due to the thickness of one branch leads to a monotonic response of an optical waveguide cantilever sensor. The simulation results showed a monotonic response with a sensitivity of 6×10-4 n m -1 in a large operation range of -1 to 1µm.

Performance of Glued Two-Layer Beams in Cantilever Structures under Abrasive Wear

Performance of Glued Two-Layer Beams in Cantilever Structures under Abrasive Wear

Integrated Structural Monitoring Method of Photogrammetry and Fiber Bragg Grating Sensors With Two Cases Study

This study proposes a novel monitoring method that combines photogrammetry and fiber Bragg grating (FBG) sensors, which provide overall shape measurement and high-precision strain sensing, respectively. A system was built and tested on a cantilever structure and a gantry crane model; it used two industrial cameras and six or 11 FBG sensors pasted along the beam. Formulas are derived and finite-element simulations of beam strain are presented, along with theoretical derivations of the relationship between image-point displacement (IPD) and 3-D spatial displacement. A series of monitoring experiments were conducted, combining FBG sensing and photogrammetry to monitor the beam under various loads. The strain and deflection curves of the beam based on FBG sensors and photogrammetry were obtained and compared. The bendings measured by photogrammetry were consistent with the strains measured by FBG sensors. To describe the relationship between the beam’s displacements at the marked points monitored by photometry and local strains, an H matrix is proposed. The proposed system allows real-time and long-term monitoring of critical structures, thereby increasing their safety.