Sinusoidal Excitation Research Articles

Design and verification of a new non-contact piezoelectric energy harvester based on a sinusoidal exciting mechanism.

In this paper, a new non-contact rotary piezoelectric energy harvester based on a sinusoidal exciting mechanism has been proposed. The energy transformation is realized in a non-contact form. The sinusoidal orbital rotor can act as a sinusoidal excitation to the contacts, and it can avoid damage to piezoelectric ceramics from direct strikes while bending piezoelectric cantilever beams. After a series of experiments, the prototype demonstrated an excellent output performance. Having explored the influence of the rotation speed on the output voltage, it reaches the peak when the rotation speed is 180rpm and the maximum voltage is 18.6V. The relationship between power and voltage was validated with the rise of resistance at the optimum speed. When the resistance is 10 kΩ, the power that arrives at the peak is 1.35 mW, and the maximum voltage is 12.1V when the resistance is 200 kΩ. Some application experiments have been designed and verify the feasibility of the prototype; it can light up 18 LEDs and power some microelectronic equipment.

Developing Dynamic System Responses Model Based on Nanotechnology by Incorporating the Finite Element Analysis

The dynamic model of complex structure has set incredible progression with the use of finite element analysis (FEA), especially in the field of vibration control and nanotechnology. Main focus of this research is to conduct a frequency analysis in ANSYS and a state space model of the beam under the platform of MATLAB. This allowed a system to develop an active dynamic model for vibration control. To enhance test and analysis of the cantilever beam of Aluminium 6061T6, a new method has been proposed to predict the dynamic response of a cantilever beam under sinusoidal base excitation. This was achieved by creating an analytical model for the cantilever beam using moment and force equilibrium equations. The authenticity of the proposed method was made by comparing the results with experimental data. Additionally, to control vibration, a Proportional-Integral-Derivative (PID) controller was developed using the system model. The FEA in the ANSYS platform provided a cantilever beam model. Also, its mathematical modelling has been done. The proposed method utilizes a novel disturbance rejection control scheme that eliminates an unknown disturbance. Experimental results indicate that the control system results in gradually decreased beam vibration amplitude. The state space approach discussed in the work could be a valuable tool for studying the behaviours of nanomaterials.

Anti-Swaying Control Strategy of Ship-Mounted 3-RCU Parallel Platform Based on Dynamic Gravity Compensation

It is essential to ensure stability during marine transportation or the installation of high center of gravity loads. The heavy loads increase gravity disturbance, affecting the steady-state-error control of the multiple degrees of freedom (DOFs) motion compensation platform. In this paper, we propose a proportional derivative (PD) controller with dynamic gravity compensation (PDGC) for a 3-RCU (revolute–cylindrical–universal) parallel platform to improve the control effect of marine motion compensation for high center of gravity loads. We introduce an evaluation parameter of load stability and a weighting coefficient of anti-swaying control to tune the controller performance. The controller can set its control target between the two, keeping the load contact surface level and allowing the load center of gravity with the least movement. By deriving the Jacobian matrix, the gravity disturbance in the joint space is calculated and is compensated in the controller. First, we verify the control superiority of this controller over the PD controller under sinusoidal excitation in simulation and validate the effectiveness of the proposed anti-swing strategy. Then, the experiments are conducted with random excitation. The root mean square (RMS) value of the load’s residual angle with the proposed controller is reduced to 32.2% and 17.6% in two directions, respectively, compared with the PD controller under class 4 sea state excitation. The proposed method is effective for the anti-swaying control of ship-mounted 3-RCU parallel platforms.

Dual-stage theoretical model of magnetorheological dampers and experimental verification

The theoretical model for predicting the damping characteristics of magnetorheological dampers (MRDs) not only facilitates the optimization of MRD parameters, but also provides assistance for the theoretical design of MRDs. However, some existing models have limitations in fully characterizing the damping characteristics of MRDs. In this paper, the working stage of MRDs was categorized into yield and pre-yield stages based on whether the internal magnetorheological fluid attains the dynamic shear yield state or not, and the Herschel–Bulkley model with pre-yield viscosity (HBPV) and improved polynomial model (IPOL) were employed to respectively characterize the yield and pre-yield stages of MRDs. Subsequently, the HBPV-IPOL model was proposed to characterize the complete damping characteristics of MRDs in low-frequency vibration conditions, with considering the local loss effect of the fluid in the model. To accurately characterize the magnetic induction intensity in the MRD damping channel, employing the steady-state finite element method for magnetic field analysis; on this basis, dividing the damping channel to investigate the variation trends of the magnetic induction intensity in different regions. Simultaneously, the zero-field region hypothesis was proposed to quantitatively consider the influence of minute magnetic induction intensity in the traditional zero-field regions on the damping characteristics of MRDs. Finally, integrating the impact trends of currents in different regions, and employing the HBPV model to determine the impact magnitude of each region within the damping channel on the damping characteristics of the MRD in the yield stage. In the pre-yield stage, polynomial curves were fitted to experimental damping force–velocity curves, and the obtained polynomials were employed to predict the damping characteristics. Extensive experiments have been conducted on MRD samples to assess the predictive performance of the model on MRD damping characteristics under sinusoidal displacement excitation vibration conditions with different excitation currents, vibration frequencies and vibration amplitudes.

Structural robustness and actuation performance of multilayered thin-film actuators based on Ni-Co flexible substrate

This paper presents a comprehensive evaluation of multilayered thin-film actuators based on metal substrates made of Ni and Co alloys. The focus was on improving the structural robustness through appropriate adhesive layers and evaluating their fundamental performance and long-term stability. We conducted nanoscratch testing and scanning electron microscopy to identify the optimal adhesive layers that significantly enhanced the adhesive strength. Following the evaluation, no instances of cracking or peeling were observed in the multilayer thin film where a Ti layer serves as an adhesion mediator between the Ni and Co thin film and the SiO2 and Si3N4 insulating layers. This indicates that this specific layer configuration provides superior structural robustness compared to multilayer thin films with alternative compositions. In addition to enhancing the structural robustness, we comprehensively evaluated the fundamental performance and long-term cyclic stability of the multilayered thin-film actuators. The actuators demonstrated exceptional characteristics including low power consumption, substantial displacements (1.58 mm at 120 mW, corresponding to an input voltage of 5 V), rapid response times, and high operating speeds. The endurance of the actuator was verified through long-term cyclic testing by subjecting it to a sinusoidal excitation for an extensive duration of 1.15 million cycles. This test demonstrated the stability of the actuator in maintaining its functionality and reliability even under prolonged operating conditions. Thereby, the test verified its structural robustness and potential for practical applications.

Unexpected results from structural acoustic optimizations

Optimization algorithms for improving the sound and/or vibration characteristics of something, such as a consumer product, have become ubiquitous. However, using them may occasionally give unexpected and undesirable results. The story of the Herdsman from Aesop’s Fables ends with the following relevant moral: “Be careful what you wish for; your wish may be granted.” While optimization tools effectively minimize an objective function subject to constraints, they may do so in unexpected and undesirable ways. Optimizing with respect to one physical phenomenon may damage other physical phenomena. This presentation reviews optimization problems related to the steady-state response of a vibrating system due to a sinusoidal excitation. To reduce global vibration, the system parameters are varied to maximize the power absorbed by damping elements. The wish is granted. The optimization process maximizes power absorbed by increasing the power that enters the system from the excitation. The result is an unexpected increase in global vibration. This result, as well as similar results and remedies from the controls community, are discussed. [Work supported by ONR under Grant N00014-22-1-2785.]

Nonlinear vibration control of magnetic bearing system considering positive and negative stiffness

The nonlinear dynamics are studied for an active magnetic bearing (AMB) system under the low-frequency sinusoidal excitation, which can affect the operational stability of a high-speed magnetic bearing. A single-degree-of-freedom nonlinear dynamics model of magnetic bearing was developed with a c-type active magnetic bearing as the research target. The characteristics of the magnetic bearing system show positive and negative stiffness for different feedback gains. The amplitude–frequency response curves of the vibration characteristics of the positive stiffness magnetic bearing system were obtained by using the method of multiple scales. The influence of each parameter on the resonance amplitude and nonlinearity of the magnetic bearing system is understood by analyzing the amplitude–frequency response curve. The bifurcation diagram for the rotor with rotor mass, and control parameters is derived from the numerical simulation of the negative stiffness magnetic bearing system. The parameter intervals that cause single-cycle vibration, double-cycle vibration, and chaotic state of the magnetic bearing rotor are discovered by analyzing the bifurcation diagrams of each parameter. The simulation results show that the magnetic bearing system exhibits complex nonlinear dynamic characteristics when it is a negative stiffness system.

Performance analysis of electromagnetic vibration energy harvester under square excitation

Harvesting energy from surrounding vibrations is an effective method for powering various low-power electronic devices. The energy output performance of vibration energy harvesters under some special excitations remains to be investigated. In this paper, a vibration energy harvester (VEH) system based on a rack and pinion mechanism and a bevel gear set is proposed, and a detailed electromechanical coupling modeling of the system under general excitation and square wave excitation is carried out. The energy output characteristics of the proposed system under square wave excitation are explored through simulation and experiment. When the energy output is the target, the priority of adjusting the constituent parameters in the equivalent mass parameter, equivalent damping parameter and equivalent stiffness parameter of the system can be obtained based on the simulation results. The experimental results under periodic square wave excitation force show that the maximum output power of the proposed system is 2.7 W at an amplitude of 4 kN and a frequency of 3 Hz. This is a 55 % increase in the maximum power compared to the sinusoidal excitation under the same conditions. It is demonstrated that the proposed system has great potential to power various low-power electronic devices.

An Inductive Method for Comprehensive Estimation of Temperature-Dependent Electrical and Thermal Properties of Conductive Ferromagnetic Materials

Reliable information about the properties of the processed materials has a significant impact on the effects of their processing. In induction heating processes, this also applies to information about the influence of temperature T on these properties. These are both thermal and electro-magnetic properties. Based on previous studies, a comprehensive experimental method is presented for estimating the temperature characteristics of thermal diffusivity, volumetric heat capacity and resistivity on one measurement station, with particular attention to ferromagnetic materials. The estimation process is carried out on an induction heating stand using forcing signals from an inverter generator. In a computer-controlled cycle that changes the base temperature level, basic measurements of thermal and electrical properties are carried out on a material sample in the form of a cylindrical disk. They are the results of the analysis of the temperature and electromagnetic responses of a material sample to short- and long-term step pulses of a sinusoidal excitation signal with a frequency of approximately 40 kHz. The presented estimation method can be treated as a final method or a preliminary procedure for radically narrowing the variability in decision variables inthe optimization process of simultaneous determination of the sought material characteristics.

Dynamic Characteristics of Bistable Vibration Energy Harvester Incorporating Electromagnetic Generator

Although various vibration energy harvesters have been designed over the past few decades, efforts to develop efficient, broadband energy harvesters continue. This work provides a detailed insight into a bistable vibration harvester subjected to correlated Gaussian white noise, with the friction between the rack and pinion described by the slip-stick model. Using the harmonic balance method, the frequency response curve of the amplitude under different mass ratios is discussed. The system response will be enhanced with an increased mass ratio for sinusoidal excitation, but not in the case of random excitation. By employing the stochastic average of the energy envelope, the dynamical governing equation of the harvester is solved, and the probability density functions (PDFs) under different damping coefficients, nonlinear stiffness of the restoring force, and excitation intensities are derived. The results are compared with those from Monte Carlo simulations (MCS) and show good accuracy. The results reveal the presence of P-bifurcations. When the nonlinear stiffness and damping coefficient vary, the number of peaks in the PDFs of system displacement and velocity changes. By adjusting the system parameters, the motion of the system can be significantly enhanced.

Research on Nonlinear Vibration of Dual Mass Flywheel Considering Piecewise Linear Stiffness and Damping

Nonlinear torsional vibration differential equation of the nested arc-shaped short spring dual mass flywheel (DMF) is established, considering the piecewise linear stiffness and damping of the spring. The first-order approximate analytical solution under sinusoidal excitation and the amplitude–frequency characteristic function are obtained by means of the average method which verified by the Runge–Kutta (R–K) method. The effects of the parameters of input excitation, inertia, and piecewise linear stiffness and damping of DMF on the resonant amplitude, resonant frequency band, and equivalent linear natural frequency of the system are analyzed. The results show that the amplitude–frequency characteristic curve bending and jumping with the changes of excitation frequency and the peak of resonant amplitude can be obviously reduced by increasing the inertia of the primary flywheel and decreasing the inertia of the secondary flywheel. The complex nonlinear dynamic phenomena such as Period 1, quasi-periodic, and chaos are obtained by analyzing the forced vibration response under the different excitation frequencies.

A pulsed bipolar current-mode power supply with high power factor in a single stage for dielectric barrier discharge application

Purpose Dielectric barrier discharge (DBD) is widely used in the treatment of skin disease, surface modification of material and other fields of electronics. The purpose of this paper is to design a high-performance power supply with a compact structure for excimer lamps in electronics application. Design/methodology/approach To design a high-performance power supply with a compact structure remains a challenge for excimer lamps in electronics application, a current-source type power supply in a single stage with power factor correction (PFC) is proposed. It consists of an excitation voltage generation unit and a PFC unit. By planning the modes of the excitation voltage generation unit, a bipolar pulse excitation voltage with a high rising and falling rate is generated. And a high power factor (PF) on the AC side is achieved by the interaction of a non-controlled rectifier and two inductors. Findings The experimental results show that not only a high-frequency and high-voltage bipolar pulse excitation voltage with a high average rising and falling rate (7.51GV/s) is generated, but also a high PF (0.992) and a low total harmonic distortion (5.54%) is obtained. Besides, the soft-switching of all power switches is realized. Compared with the sinusoidal excitation power supply and the current-source power supply, the proposed power supply in this paper can take advantage of the potential of excimer lamps. Originality/value A new high-performance power supply with a compact structure for DBD type excimer lamps is proposed. The proposed power supply can work stably in a wide range of frequencies, and the smooth regulation of the discharge power of the excimer lamp can be achieved by changing the switching frequency. The ideal excitation can be generated, and the soft switching can be realized. These features make this power supply a key player in the outstanding performance of the DBD excimer lamps application.

The spectrally resolved photoluminescence decay in YAG:Er, ZnO and SiO2 crystals

We present an optical setup for measuring spectrally resolved photoluminescence (PL) mean decay time using conventional UV LED with sinusoidal excitation and a phase shift method. The phase sensitive detection was applied on the Er-doped yttrium aluminium garnet single crystal (YAG:Er, grown by the micro-pulling-down method) and hydrothermally grown zinc oxide micro-crystallites (ZnO). Commercial ZnO and silicon oxide (SiO2) microcrystalline powders were measured for comparison. SiO2 powder was annealed in O2 plasma at 500 °C for cleaning. While YAG:Er shows well resolved greenish PL peaks with mean decay time about 15 μs related to the Stark splitting of Er3+ (4f11) states and ZnO micro-powder broad reddish PL with similar PL decay time, the plasma treated SiO2 powder shows weak bluish defect-related PL with significantly faster mean decay times below 100 ns.

Analytical Torque Ripple Reduction Strategy for Flux Modulated Doubly-Salient Reluctance Motor Drives Based on ZSC Harmonic Regulation

Compared to the conventional doubly-salient reluctance motor (DRM) drives, the novel flux modulated DRM (FMDRM) drives can achieve a better overall torque performance due to the dc-biased sinusoidal current excitation. However, previous investigations only focus on the dc-biased and fundamental current components, and the contributions of current harmonics to the torque production are not clear. This paper proposes an analytical torque ripple reduction strategy for open-winding FMDRM drives based on zero-sequence current (ZSC) harmonic regulation. Firstly, the contribution of third-order ZSC harmonic to the electromagnetic torque is investigated together with the dc-biased sinusoidal current components. Secondly, an alternative torque component cancellation method is put forward, where the additional third-order ZSC is utilized to counteract the dominating part of the alternative torque generated by the dc-biased sinusoidal current for torque ripple reduction. Both the amplitude and initial phase angle of the additional third-order ZSC are calculated by the analytical equation of electromagnetic torque. Moreover, the corresponding three-dimensional current distribution is investigated to achieve the desired ZSC regulation. With the proposed scheme, the torque ripple can be effectively suppressed while maintaining high output torque capability and efficiency. Furthermore, experimental results are presented on a three-phase FMDRM prototype to verify the proposed strategy. <fn fn-type="other" id="fn3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> </fn>

Analysis of Coupled Vibration Characteristics of Linear-Angular and Parameter Identification

Abstract A steady-state sinusoidal and distortion-free excitation source is very important for the accuracy and consistency of the calibration parameters of micro-electro-mechanical systems (MEMS) inertial sensors. To solve the problem that the current MEMS inertial measurement unit (IMU) calibration device is unable to reproduce the spatial motion of linear and angular vibration coupling, research topics on the coupling vibration characteristics and parameter identification for an electromagnetic linear-angular vibration exciter are proposed. This research paper used Ampere’s law and Lorentz force to establish the analytical expressions for the electromagnetic force and electromagnetic torque of the electromagnetic linear-angular vibration exciter. Then, the main purpose of this paper is to establish uniaxial and coupled vibration electromechanical analogy models containing mechanical parameters based on the admittance-type electromechanical analogy principle, and the parameter identification model is also obtained by combining the impedance formula with the additional mass method. Finally, the validity of the coupling vibration characteristics and the parameter identification model are verified by the frequency response simulation and the additional mass method, and the relative error of each parameter identification is within 5% in this paper.

Experimental study on damping characteristics of the particle dampers with damping rod and soft inside wall

In the perpendicular simple sinusoidal excitation, the damping characteristics of the soft-wall particle damper with a damping rod were experimentally investigated by controlling the acceleration amplitude and vibration frequency of the damper motion and measuring the force and acceleration signals. The experimental results show that the loss power of the damper increases monotonically with the rise of the excitation acceleration amplitude, and the effective mass shows the change of “gentle decrease-critical point-decrease”. As the driving frequency rises, the loss power progressively decreases, and the effective mass does not change significantly. By analyzing the damping characteristics of different dampers, it shows that the damping effectiveness of the soft inside wall particle damper with a damping rod is obviously better.

Composition Regulation of Potassium Sodium Niobate Thin Films through Post-Annealing under Alkali Element Atmospheres

Amorphous potassium sodium niobate (KNN) films were synthesized at 300 °C through the radio frequency magnetron sputtering method and subsequently crystallized by post-annealing at 700 °C in various alkali element atmospheres (Na and K). The as-deposited film is notably deficient in alkali metal elements, particularly K, whereas the loss of alkali elements in the films can be replenished through annealing in an alkali element atmosphere. By adjusting the molar ratio of Na and K in the annealing atmosphere, the ratio of Na/K in the resultant film varied, consequently suggesting the efficiency of this method on composition regulation of KNN films. Meanwhile, we also found that the physical characteristics of the films also underwent differences with the change of an annealing atmosphere. The films annealed in a high Na atmosphere exhibit large dielectric losses with limited piezoelectric vibration behavior, while annealing in a high K atmosphere reduces the dielectric losses and enhances the piezoelectric behavior. Furthermore, the results of vibration measurement demonstrated that the film annealed in a mixed powder of 25% Na2CO3 and 75% K2CO3 exhibits an optimal vibration displacement of ~400 pm under the sinusoidal excitation voltage of 8 V. This approach of altering the composition of KNN films through post-annealing may introduce the new concept of property design of KNN as well as other similar films.

Smartphone Fast Charger Analysis Based on RLC Circuit Transient Process

In today's era, the widespread adoption of mobile terminals, particularly smartphones, has been facilitated by the rapid advancements in information and communication technology. However, a notable drawback of smartphones is their high-power consumption, necessitating faster charging solutions to enhance user convenience. This paper focuses on the RLC circuit of fast chargers. Initially, it introduces the fundamental principles and associated protocols of fast charging technology, elucidating the operation of integrated circuits within fast chargers and highlighting the advantages of fast charging compared to conventional slow charging methods. Moreover, the paper conducts an in-depth analysis of the transient processes within the pivotal series RLC circuit in fast chargers, encompassing zero-input responses and sinusoidal AC excitation responses. The transient processes are categorized into overdamped, critically damped, or underdamped states based on circuit element parameters, with initial conditions and power supply phase determining whether the circuit transitions directly into a steady-state process when stimulated by sinusoidal AC. This research contributes to a deeper understanding of the RLC circuit within smartphone fast chargers and serves as a valuable reference for advancing the development of fast charging solutions.

Design and analysis of magnetostrictive two-dimensional kinetic energy harvester

Conventional energy harvesters often require high ambient vibration frequencies and can only capture vibration energy in a single direction. To address these issues, this paper designs a magnetostrictive two-dimensional kinetic energy harvester placed under the floor and capable of capturing energy in both vertical and horizontal directions. In order to achieve higher electrical power output at low-frequency input forces, a two-stage force amplification mechanism is designed to amplify the walking kinetic energy of pedestrians and the main parameters of this structure are analyzed and optimized. On the other hand, by constructing different forms of bias magnetic field, the influence of bias magnetic field on the deflection and motion of the internal magnetic domain of Terfenol-D is systematically studied, and the best bias form that can make the material shows the strongest magnetization characteristics is determined. Next, a prototype harvester was built, and an experimental vibration system was set up to test and analyze the output characteristics of the harvester comprehensively. The experimental results show that the harvester produces 21.2 mW of peak output power under sinusoidal excitation at an operating frequency of 4 Hz. Under random excitation, a peak output voltage of 2.64 V and 170 mW peak power was obtained. Under actual pedestrian walking tests, 17.62 mW peak output power is obtained to power low-power devices. The study’s results provide preliminary evidence that the designed magnetostrictive energy harvester can stably harvest kinetic energy from pedestrian walking.

Inkjet printing P(VDF-TrFE-CTFE) actuators for large bending strains

Additive manufacturing of sensors and actuators together with structural materials and electronics will make it possible to fabricate innovative system designs that are overly laborious to realise with conventional methods. While printing of the structural materials and electronics are advancing fast, the additive manufacturing methods for actuators and sensors are in an earlier stage of development. This research will develop a manufacturing process for entirely inkjet printed electroactive polymer (EAP) actuators basing on the P(VDF-TrFE-CTFE) relaxor ferroelectric polymer and Ag electrodes. The process consists of (1) printing an Ag layer on a polyethylene terephthalate (PET) substrate for the bottom electrode; (2) formulating, printing and annealing a P(VDF-TrFE-CTFE) ink for the EAP layer; and (3) printing and sintering an Ag layer on the plasma-treated EAP surface to form the top electrode. Two actuator variations, addressed as DMC and KM512, are manufactured and characterised by their: (a) response to quasi-static excitation (1 Hz sine wave); (b) hysteresis behaviour; (c) actuation amplitude variation with the input voltage; and (d) frequency response. The 18 mm long actuators showed 91.4 µm (DMC, 200 Vpp ) and 224 µm (KM512, 275 Vpp ) deflections in response to 1 Hz sinusoidal excitation, and 1.10 mm (DMC, 113 Hz, 200 Vpp ) and 1.72 mm (KM512, 114 Hz, 200 Vpp ) deflections in resonant operation. It is 55% more quasi-static strain and 470% more resonant strain than in earlier fully inkjet-printed polyvinylidene fluoride (PVDF) -based actuators, and comparable to similar partially inkjet-printed actuators. This is the first time that inkjet printing of all three layers of a relaxor ferroelectric actuator have been achieved.