scholarly journals Piezoelectric Shunt Stiffness in Rhombic Piezoelectric Stack Transducer with Hybrid Negative-Impedance Shunts: Theoretical Modeling and Stability Analysis

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3387
Author(s):  
He ◽  
Zheng ◽  
Zhao ◽  
Wu
Keyword(s):  
Coupled System ◽  
Analytical Framework ◽  
Negative Stiffness ◽  
Negative Capacitance ◽  
Control Engineering ◽  
Locus Method ◽  
In Series ◽  
The Stability ◽  
Stiffness And Damping ◽  
Piezoelectric Shunt

Negative-capacitance shunted piezoelectric polymer was investigated in depth due to its considerable damping effect. This paper discusses the novel controlled stiffness performance from a rhombic piezoelectric stack transducer with three hybrid negative-impedance shunts, namely, negative capacitance in series with resistance, negative capacitance in parallel with resistance, and negative inductance/negative capacitance (NINC) in series with resistance. An analytical framework for establishing the model of the coupled system is presented. Piezoelectric shunt stiffness (PSS) and piezoelectric shunt damping (PSD) are proposed to analyze the stiffness and damping performances of the hybrid shunts. Theoretical analysis proves that the PSS can produce both positive and negative stiffness by changing the negative capacitance and adjustable resistance. The Routh–Hurwitz criterion and the root locus method are utilized to judge the stability of the three hybrid shunts. The results point out that the negative capacitance should be selected carefully to sustain the stability and to achieve the negative stiffness effect of the transducer. Furthermore, negative capacitance in parallel with resistance has a considerably better stiffness bandwidth and damping performance than the other two shunts. This study demonstrates a novel electrically controlled stiffness method for vibration control engineering.

Optimal Parameters and Characteristics of Shunted Piezoelectric System with Negative Capacitance in Series

2010 ◽  
Vol 44-47 ◽  
pp. 3812-3817
Author(s):  
Wen Qun Zhang ◽  
Xin Yue Wu ◽  
Wen Cao
Keyword(s):  
Dynamic Stiffness ◽  
The Other ◽  
Effective Bandwidth ◽  
Negative Capacitance ◽  
Optimal Parameters ◽  
Low Frequencies ◽  
Vibration Isolators ◽  
System Optimal ◽  
In Series ◽  
The Stability

Piezoelectric system shunted with proper negative capacitance in series has low dynamic stiffness. According to frequency characteristic equations of the piezoelectric system, optimal parameters and characteristics of both shunted series structures were deduced and compared theoretically. One is negative-capacitance and resistance in series, and the other is negative-capacitance, resistance and inductance in seires. It presented that high damping characteristic can be obtained at low frequencies when shunted with series negative-capacitance. If proper inductance is included in shunt circuit, effective bandwidth could be extended and the peak of amplitude of response is decreased, what’ more, the stability of this structure is enhanced. This technology can be used in vibration isolators or sensors and the shunt structure including inductance is recommended.

scholarly journals A Bio-Inspired Compliance Planning and Implementation Method for Hydraulically Actuated Quadruped Robots with Consideration of Ground Stiffness

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2838
Author(s):  
Xiaoxing Zhang ◽  
Haoyuan Yi ◽  
Junjun Liu ◽  
Qi Li ◽  
Xin Luo
Keyword(s):  
Harmonic Oscillation ◽  
Ground Surface ◽  
Legged Locomotion ◽  
Soft Ground ◽  
Quadruped Robots ◽  
In Series ◽  
Reaction Forces ◽  
Implementation Method ◽  
The Stability ◽  
Natural Dynamics

There has been a rising interest in compliant legged locomotion to improve the adaptability and energy efficiency of robots. However, few approaches can be generalized to soft ground due to the lack of consideration of the ground surface. When a robot locomotes on soft ground, the elastic robot legs and compressible ground surface are connected in series. The combined compliance of the leg and surface determines the natural dynamics of the whole system and affects the stability and efficiency of the robot. This paper proposes a bio-inspired leg compliance planning and implementation method with consideration of the ground surface. The ground stiffness is estimated based on analysis of ground reaction forces in the frequency domain, and the leg compliance is actively regulated during locomotion, adapting them to achieve harmonic oscillation. The leg compliance is planned on the condition of resonant movement which agrees with natural dynamics and facilitates rhythmicity and efficiency. The proposed method has been implemented on a hydraulic quadruped robot. The simulations and experimental results verified the effectiveness of our method.

scholarly journals A Theoretical Model for the Transmission Dynamics of the Buruli Ulcer with Saturated Treatment

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Ebenezer Bonyah ◽  
Isaac Dontwi ◽  
Farai Nyabadza
Keyword(s):  
Human Population ◽  
Reproduction Number ◽  
Buruli Ulcer ◽  
Coupled System ◽  
Model Parameters ◽  
The Public ◽  
Treatment Function ◽  
Medical Facilities ◽  
The Stability ◽  
Saturated Treatment

The management of the Buruli ulcer (BU) in Africa is often accompanied by limited resources, delays in treatment, and macilent capacity in medical facilities. These challenges limit the number of infected individuals that access medical facilities. While most of the mathematical models with treatment assume a treatment function proportional to the number of infected individuals, in settings with such limitations, this assumption may not be valid. To capture these challenges, a mathematical model of the Buruli ulcer with a saturated treatment function is developed and studied. The model is a coupled system of two submodels for the human population and the environment. We examine the stability of the submodels and carry out numerical simulations. The model analysis is carried out in terms of the reproduction number of the submodel of environmental dynamics. The dynamics of the human population submodel, are found to occur at the steady states of the submodel of environmental dynamics. Sensitivity analysis is carried out on the model parameters and it is observed that the BU epidemic is driven by the dynamics of the environment. The model suggests that more effort should be focused on environmental management. The paper is concluded by discussing the public implications of the results.

Selective Wave Filtering in Time-Modulated Elastic Metamaterials

2018 ◽  
Author(s):  
Yiwei Xia ◽  
Giuseppe Trainiti ◽  
Alper Erturk ◽  
Massimo Ruzzene
Keyword(s):  
Single Port ◽  
Negative Capacitance ◽  
Time Modulation ◽  
Piezoelectric Patch ◽  
Flat Bands ◽  
Elastic Metamaterials ◽  
In Series ◽  
Port System ◽  
Opening And Closing ◽  
Time Periodic

We implement periodic stiffness time-modulation in a beam with piezoelectric patches and switchable shunted negative capacitance. The shunted negative capacitance circuits, connected in series with each piezoelectric patch through a switch, soften the structure. By alternatively opening and closing the switch, the beam’s stiffness effectively oscillates periodically between two values. We present a simplified theoretical model of time-periodic beams and describe the occurrence of flat bands in the dispersion diagrams. We show that a narrowband reflection from a time-modulated domain can be obtained for a broadband incident wave, hence qualifying the modulated domain as a single-port system with tunable response. We validate our theoretical findings by comparing time-domain simulations with experimental measurements of transient wavefields through scanning Doppler laser vibrometry.

A Variable Viscosity Approach for the Analysis of Steady State and Dynamic Characteristics of Two-Lobe Journal Bearing With TiO2 Based Nanolubricant

2017 ◽  
Author(s):  
Ashutosh Kumar ◽  
Sashindra Kumar Kakoty
Keyword(s):  
Steady State ◽  
Dynamic Characteristics ◽  
Journal Bearing ◽  
Volume Fraction ◽  
Variable Viscosity ◽  
Flow Coefficient ◽  
Viscosity Model ◽  
Nano Lubricant ◽  
The Stability ◽  
Stiffness And Damping

Steady-state and dynamic characteristics of two-lobe journal bearing, operating on TiO2 based Nano-lubricant has been obtained. The effective viscosity is obtained by using Krieger-Dougherty viscosity model for a given volume fraction of nanoparticle in the base fluid. Various bearing performance characteristics are then obtained by solving modified Reynolds equation for variable viscosity model and couple stress model. The stiffness and damping coefficients are also determined for various values of the volume fraction of the nanoparticle in the nanofluid. Results reveal that load carrying capacity and flow coefficient increase whereas friction variable decreases without affecting the stability condition of two-lobe journal bearing operating on TiO2 based nanolubricant. On the other hand attitude angle and dynamic coefficients remains constant for all the values of volume fraction of nanoparticle.

Initiative Cooperation: Exploring a New Intergovernmental Model for Dealing with Risk of Tobacco Monopoly Administrative Law Enforcement

2021 ◽  
Vol 7 (5) ◽  
pp. 3003-3011
Author(s):  
Xu Jing
Keyword(s):  
Law Enforcement ◽  
Local Governments ◽  
Central Government ◽  
Analytical Framework ◽  
Administrative Law ◽  
Risk Society ◽  
Survey Method ◽  
Local Officials ◽  
The Stability ◽  
Tobacco Monopoly

Objective: The risk of administrative law enforcement is slowly being exposed to the public. The law enforcement of tobacco monopoly administration plays an important role in maintaining the stability of tobacco market and promoting the benign development of tobacco industry. However, due to the combination of subjective and objective factors, there are many risks in the process of tobacco monopoly law enforcement, which seriously affect the effectiveness of tobacco monopoly law enforcement. In risk society, risk has the characteristics of fluidity and cross-region, which increases the difficulty of administrative law enforcement among local governments. The purpose of this paper is to explore a new model to deal with the risk of local government enforcement against tobacco monopoly administration. Methods: The research adopted the field survey method, 75 local officials were interviewed, including 68 effective interviews and 7 invalid interviews, then analyzed the manifestations of passive cooperation through multiple cases. Results: We found that when risk of tobacco monopoly administrative law enforcement occur frequently, local intergovernmental still choose not to cooperate or cooperate passively at the request of the central government. By analyzing the forms of passive cooperation, we established an analytical framework of initiative cooperation and worked out three elements of initiative cooperation: trust, consensus and tacit understanding. Conclusion: Initiative cooperation is the highest form of cooperation and the best choice for local intergovernmental to deal with risk of tobacco monopoly administrative law enforcement.

The Sound Transmission Through a Baffled, Thin, Finite, Elastic Plate by Using Boundary Integral Equations

1999 ◽  
Author(s):  
Yasuhito Kawai
Keyword(s):  
Integral Equations ◽  
Elastic Plate ◽  
Boundary Integral Equations ◽  
Sound Transmission ◽  
Coupled System ◽  
Boundary Integral ◽  
Image Method ◽  
Thin Elastic Plate ◽  
Control Engineering ◽  
Sound Fields

Abstract The prediction of sound transmission through a thin elastic plate such as a window is an important problem in the field of noise control engineering. Integral equations which express sound fields in infinite half spaces which are divided off by the baffle and the elastic plate are introduced and combined with the equation of plate vibration to solve as a coupled system. The image method is used in every equation to reduce unknown functions and boundaries which should be considered. Some numerical examples are solved numerically to examine the method.

scholarly journals Study on dynamic characteristics of gas films of spherical spiral groove hybrid gas bearings

2019 ◽  
Vol 233 (8) ◽  
pp. 1169-1181
Author(s):  
Chenhui Jia ◽  
Haijiang Zhang ◽  
Shijun Guo ◽  
Ming Qiu ◽  
Wensuo Ma ◽  
...  
Keyword(s):  
Pressure Effect ◽  
Dynamic Pressure ◽  
Iteration Algorithm ◽  
Unstable State ◽  
Gas Bearings ◽  
Damping Coefficients ◽  
The Stability ◽  
Stiffness And Damping ◽  
Film Stiffness ◽  
Gas Bearing

According to the gas film force variation law, when the bearing axis is slightly displaced from the static equilibrium position, displacement and velocity disturbance relation expressions for the gas film force increment are constructed. Moreover, combined with the bearing rotor system motion equation, calculation model equations for the gas film stiffness and damping coefficients are established. The axial and radial vibration and velocity of the gas bearings during operation are collected. The instantaneous stiffness and damping coefficients of the gas film are calculated by the rolling iteration algorithm using MATLAB. The dynamic changes in the gas film stiffness and damping under different motion states are analyzed, and the mechanism of the gas film vortex and oscillation is studied. The results demonstrate the following: (1) When the gas bearing is running in the linear steady state in cycle 1, the dynamic pressure effect is enhanced and the stability is improved by increasing the eccentricity; when the gas supply pressure is increased, the static pressure effect is enhanced and the gas film vortex is reduced, but the oscillation is strengthened. (2) With the increase in rotational speed, the gas film vortex force gradually exceeds the gas film damping force, and the stability gradually worsens, causing a fluctuation in the gas film stiffness and damping, following which singularity occurs and a half-speed vortex is formed. Meanwhile, the gas film oscillation is intensified, and the rotor enters the nonlinear stable cycle 2 state operation. (3) As the fluctuation of the film force increases, the instantaneous stiffness and damping oscillation of the film intensifies, most of the stiffness and damping coefficients exhibit distortion, and the rotor operation will enter a chaotic or unstable state. Therefore, the gas bearing stiffness and damping variation characteristics can be used to study and predict the gas bearing operating state. Finally, measures for reducing the vortex and oscillation of the gas film and improving the stability of the gas bearing operation are proposed.

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