Wideband PPT Class Φ2 Inverter using Phase-Switched Impedance Modulation and Reactance Compensation

2021 ◽  
pp. 1-1
Author(s):  
Zikang Tong ◽  
Lei Gu ◽  
Juan Rivas-Davila
Keyword(s):  
Impedance Modulation

scholarly journals Estimation of the Two Degrees-of-Freedom Time-Varying Impedance of the Human Ankle

2018 ◽  
Vol 12 (1) ◽  
Author(s):  
Evandro Ficanha ◽  
Guilherme Ribeiro ◽  
Lauren Knop ◽  
Mo Rastgaar
Keyword(s):  
Degrees Of Freedom ◽  
Mechanical Impedance ◽  
Heel Strike ◽  
Time Varying ◽  
Two Degrees Of Freedom ◽  
Impedance Modulation ◽  
Ankle Stiffness ◽  
Human Ankle ◽  
Stiffness And Damping ◽  
And Inversion

An understanding of the time-varying mechanical impedance of the ankle during walking is fundamental in the design of active ankle-foot prostheses and lower extremity rehabilitation devices. This paper describes the estimation of the time-varying mechanical impedance of the human ankle in both dorsiflexion–plantarflexion (DP) and inversion–eversion (IE) during walking in a straight line. The impedance was estimated using a two degrees-of-freedom (DOF) vibrating platform and instrumented walkway. The perturbations were applied at eight different axes of rotation combining different amounts of DP and IE rotations of four male subjects. The observed stiffness and damping were low at heel strike, increased during the mid-stance, and decreases at push-off. At heel strike, it was observed that both the damping and stiffness were larger in IE than in DP. The maximum average ankle stiffness was 5.43 N·m/rad/kg at 31% of the stance length (SL) when combining plantarflexion and inversion and the minimum average was 1.14 N·m/rad/kg at 7% of the SL when combining dorsiflexion and eversion. The maximum average ankle damping was 0.080 Nms/rad/kg at 38% of the SL when combining plantarflexion and inversion, and the minimum average was 0.016 Nms/rad/kg at 7% of the SL when combining plantarflexion and eversion. From 23% to 93% of the SL, the largest ankle stiffness and damping occurred during the combination of plantarflexion and inversion or dorsiflexion and eversion. These rotations are the resulting motion of the ankle's subtalar joint, suggesting that the role of this joint and the muscles involved in the ankle rotation are significant in the impedance modulation in both DP and IE during gait.

Detection of Contact-Type Damages by Utilizing Nonlinear Piezoelectric Impedance Modulation of Self-Excited Structures

2013 ◽  
Author(s):  
Arata Masuda ◽  
Yuya Ogawa ◽  
Akira Sone
Keyword(s):  
Damage Detection ◽  
Wave Field ◽  
High Frequency ◽  
Detection Method ◽  
Piezoelectric Sensor ◽  
Frequency Wave ◽  
Contact Type ◽  
Impedance Modulation ◽  
Excited Oscillation ◽  
Piezoelectric Impedance

This paper presents an improvement of a nonlinear piezoelectric impedance modulation (NPIM)-based damage detection method, a damage-sensitive, baseline-free structural health monitoring technique proposed by the authors, by introducing self-excited oscillation. The NPIM-based damage detection utilizes the modulation of high-frequency wave field of structures caused by the contact acoustic nonlinearity at the damaged part. In this study, the high-frequency wave field is induced as a self-excited oscillation of the structure by positively feed-backing the strain signal measured by a surface-bonded piezoelectric sensor, followed by a phase-shift in 90 degrees and a nonlinear element consisting of a saturation element and a negative linear gain. The induced self-excitation can have multiple stable limit cycles at certain eigenmode frequencies, and one can switch among them by inputting an auxiliary excitation signal into the feedback loop. The current flowing through the piezoelectric sensor is measured to detect its modulation due to the stiffness fluctuation due to the existence of the contact-type damage. Experiments using a specimen with a simulated damage are conducted to examine the performance of the self-excitation circuit and its applicability to the NPIM-based damage detection method.

Estimation of the 2-DOF Time-Varying Impedance of the Human Ankle

2017 ◽  
Author(s):  
Evandro Ficanha ◽  
Guilherme Aramizo Ribeiro ◽  
Lauren Knop ◽  
Mohammad Rastgaar Aagaah
Keyword(s):  
Degrees Of Freedom ◽  
Muscle Activation ◽  
Stance Phase ◽  
Impedance Control ◽  
The Body ◽  
Time Varying ◽  
Ankle Impedance ◽  
Impedance Modulation ◽  
Human Ankle ◽  
Vibrating Platform

The human ankle plays a major role in locomotion as it the first major joint to transfer the ground reaction torques to the rest of the body while providing power for locomotion and stability. One of the main causes of the ankle impedance modulation is muscle activation [1, 2], which can tune the ankle’s stiffness and damping during the stance phase of gait. The ankle’s time-varying impedance is also task dependent, meaning that different activities such as walking at different speeds, turning, and climbing/descending stairs would impose different profiles of time-varying impedance modulation. The impedance control is commonly used in the control of powered ankle-foot prostheses; however, the information on time-varying impedance of the ankle during the stance phase is limited in the literature. The only previous study during the stance phase, to the best of the authors knowledge, reported the human ankle impedance at four points of the stance phase in dorsiflexion-plantarflexion (DP) [1] during walking. To expand previous work and estimate the impedance in inversion-eversion (IE), a vibrating platform was fabricated (Fig. 1) [3]. The platform allows the ankle impedance to be estimated at 250 Hz in both DP and IE, including combined rotations in both degrees of freedom (DOF) simultaneously. The results can be used in a 2-DOF powered ankle-foot prosthesis developed by the authors, which is capable of mimicking the ankle kinetics and kinematics in the frontal and sagittal planes [4]. The vibrating platform can also be used to tune the prosthesis to assure it properly mimics the human ankle dynamics. This paper describes the results of the preliminary experiments using the vibrating platform on 4 male subjects. For the first time, the time-varying impedance of the human ankle in both DP and IE during walking in a straight line are reported.

Electrical Detection of Protein Biomarkers Using Nanoneedle Biosensors

2012 ◽  
Vol 1414 ◽  
Author(s):  
Rahim Esfandyarpour ◽  
Hesaam Esfandyarpour ◽  
Mehdi Javanmard ◽  
James S. Harris ◽  
Ronald W. Davis
Keyword(s):  
Physical Adsorption ◽  
Ionic Current ◽  
Microfluidic Channel ◽  
Protein Detection ◽  
High Sensitivity ◽  
Receptor Protein ◽  
Label Free ◽  
Electrical Detection ◽  
Protein Biomarkers ◽  
Impedance Modulation

Abstract:Here we present the development of an array of electrical nano-biosensors in a microfluidic channel, called Nanoneedle biosensors. Then we present the proof of concept study for protein detection. A Nanoneedle biosensor is a real-time, label-free, direct electrical detection platform, which is capable of high sensitivity detection, measuring the change in ionic current and impedance modulation, due to the presence or reaction of biomolecules such as proteins or nucleic acids. We show that the sensors which have been fabricated and characterized for the protein detection. We have functionalized Nanoneedle biosensors with receptors specific to a target protein using physical adsorption for immobilization. We have used biotinylated bovine serum albumin as the receptor and sterptavidin as the target analyte. The detection of streptavidin binding to the receptor protein is also presented.

scholarly journals Towards altering sound frequency at will by a linear meta-layer with time-varying and quantized properties

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yumin Zhang ◽  
Keming Wu ◽  
Chunqi Wang ◽  
Lixi Huang
Keyword(s):  
Super Resolution ◽  
Wave Frequency ◽  
Einstein Relation ◽  
Time Varying ◽  
Underwater Communication ◽  
Impedance Modulation ◽  
Measured Ratio ◽  
Resolution Imaging ◽  
Human Hearing ◽  
At Will

AbstractWave frequency is a critical parameter for applications ranging from human hearing, acoustic non-reciprocity, medical imaging to quantum of energy in matter. Frequency alteration holds the promise of breaking limits imposed by the physics laws such as Rayleigh’s criterion and Planck–Einstein relation. We introduce a linear mechanism to convert the wave frequency to any value at will by creating a digitally pre-defined, time-varying material property. The device is based on an electromagnetic diaphragm with a MOSFET-controlled shunt circuit. The measured ratio of acoustic impedance modulation is up to 45, much higher than nonlinearity-based techniques. A significant portion of the incoming source frequency is scattered to sidebands. We demonstrate the conversion of audible sounds to infrasound and ultrasound, respectively, and a monochromatic tone to white noise by a randomized MOSFET time sequence, raising the prospect of applications such as super-resolution imaging, deep sub-wavelength energy flow control, and encrypted underwater communication.

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