Adaptive impedance control of a haptic interface

Teleoperation enables an operator to manipulate remote objects. One of the main goals in teleoperation research is to provide the operator with the feeling of the telepresent object and of being present at the remote site. In order for this to happen, a master robot must be designed as a bilateral control system that can transmit position commands to a slave robot and reflect the interaction force. A newly proposed adaptive impedance algorithm is applied to the force control of a haptic interface that has been developed as a master robot. With the movement of the haptic interface for position command generation, the impedance between an operator and the haptic interface varies dynamically. When the impedance parameters and the dynamics of the haptic interface are known precisely, many model based control theories and methods can be used to control the interface accurately. However, due to the parameters’ variations and the uncertainty in the dynamic model, it is difficult to control the interface precisely. Therefore, this paper proposes a new adaptive impedance control algorithm and experimentally verifies the effectiveness of the algorithm for control of the haptic interface.     

Comparison of impedance at the microelectrode-saline andmicroelectrode-culture medium interface

The impedance characteristics of gold-plated indium-tin-oxide microelectrodes immersed in culture medium (MEM) are described and compared with the impedance characteristics observed when those microelectrodes are immersed in isotonic saline. For microelectrode areas of approximately 100 microns2, applied voltage levels of 5, 50, and 100 mV, and for frequencies of from 100 Hz to 10 kHz the resistance, capacitance, capacitive reactance, and total impedance are given as a function of frequency both in culture medium and in saline. The results, which hold for current densities ranging from 0.45 to 700 pA/microns2, are compared. Also given are the alpha and K values determining the frequency characteristics of the interface resistance and capacitance in medium and in saline.     

New methods for the measurement of cathode interface impedance

Two improved methods for the measurement of cathode interface impedance have been developed, and their limitations have been analyzed. One of these, the complementary network method, is an improvement of a technique disclosed at the IRE National Convention in 1952. The other, the shunt admittance bridge, has not been described previously. Both methods allow the measurement of impedance with both small resistance and short time constant, well below the limit, 50 ohms at 0.1 µsec, of most present equipments. With the development of improved cathode alloys, the measurement of interface impedances having short time constants and low resistances has become important to control this parameter in manufacture and to obtain further improvement. For the complementary-network bridge, the theoretical analysis has shown the extreme importance of minimizing stray inductance in the complementary network. When corrections are applied, the complementary-network bridge has good accuracy, with less than one-ohm error at 10 ohms and 0.05 µsec and lower relative errors for higher resistances. The shunt admittance bridge is most satisfactory when tubes with transconductances greater than 10,000 µmho are to be measured. An impedance transformation is used which allows much easier physical realization of the measurement network than in other interface measurement methods. For tubes with transconductances greater than 10,000 µmho, the shunt admittance bridge will provide accurate time constant and resistance data down to 0.02 µsec and 5 ohms.     

Reducing power bus impedance at resonance with lossy components

Power bus structures in printed circuit boards with solid power and ground planes exhibit resonances. When the power bus is resonant, the power bus impedance can increase dramatically. This paper explores the effect of component equivalent series resistance (ESR) on power bus resonances. General guidelines for selecting an optimum ESR are provided and are supported by laboratory measurements and numerical simulations.     

Modulation method for measuring thermal impedance components of semiconductor devices

The paper describes the modulation method of measuring the thermal impedance of semiconductor devices as well as its implementation. In contrast to the standard method (JESD51-1 standard) which requires heating the device under test by the stepped power, the modulation method uses heating power modulated harmonically. A pulse sequence of heating current, with the pulse length varying harmonically, is passed through the device under test. The p-n junction temperature is measured through a temperature-sensitive parameter, namely a forward voltage drop on the p-n junction between heating pulses at low measuring current. First harmonic of the p-n junction temperature oscillation is determined by the discrete Fourier transform, which allows to determine thermal impedance absolute value and phase at modulation frequency of heating power. An analysis of the dependence of thermal impedance on modulation frequency allows to determine thermal impedance components corresponding to the structural elements of the device under test. Numerical simulation shows that the thermal resistance components on the Foster's network may be determined at the modulation frequencies corresponding to the first derivative minima of the thermal impedance of the real part of frequency dependence. The main characteristics of the device that implements the method are described.     

Direct investigations of the interface impedance of organic field-effect transistors with self-assembled-monolayer-modified electrodes

It has been demonstrated that the modification of electrodes with self-assembled monolayers (SAMs) reduces the contact resistance and improves the device performances of organic field-effect transistors (OFETs). However, it has been difficult to judge if the contact resistance was reduced by the change in the electronic properties or by the change in the morphology of the metal–organic interface caused by the SAM modification because they have been difficult to be separately assessed. We have directly investigated the local impedance and the potential difference at the electrode–channel interfaces of the OFETs with and without modification of the electrodes by a pentafluorobenzenethiol SAM using frequency-modulation scanning impedance microscopy (FM-SIM). The potential profile measurement and the FM-SIM measurement at the interface showed that the improvement of the field-effect mobility in the SAM-modified OFET was caused by the reduction of the energy level mismatch, namely, the hole injection barrier at the source–channel interface, presumably with the reduction of the hole trap sites at the source–channel interface.     

High output impedance current-mode first-order allpass networks with four grounded components and two CCIIs

Eight current-mode first-order allpass networks using second-generation current conveyors (CCII) are presented. Each of the proposed circuits employs two CCIIs, two grounded capacitors and two grounded resistors. The networks offer high output impedances. Experimental results are also included.     

Haptic display with an interface device capable of continuous-time impedance display within a sampling period

Stability of a haptic interface is an important issue in virtual reality because an operator directly touches haptic interface devices. Stability is influenced by the sampling period and the discrete-time property of the control system. For decreasing the sampling system influence, this paper proposes a haptic device with an analog circuit which is placed between the computer and the haptic device. The circuit functions as springs and dampers. The control system can specify stiffness, damping coefficients, and their equilibrium. Since the impedance generated by the electric spring and damper can work continuously within the sampling period, it is effective for making the system more stable. We also develop a control method for displaying a static virtual object with the proposed device. Further, we discuss the effects of the proposed approach analytically, using passivity analysis for a 1-degree-of-freedom display system. Finally, some experimental results in a two-dimensional virtual environment are presented.     

Insensitive high-output impedance minimum configuration SITO-type current-mode biquad using dual-output current conveyors and grounded passive components

This paper presents a high-output impedance current mode single-input and three-outputs (SITO)-type multifunction filter which employs three dual-output current conveyors to simultaneously realize low-pass, high-pass and band-pass responses. The proposed circuit uses grounded-virtually grounded passive components (which makes the circuit ideal for integration and tuning). Moreover, it has low active and passive component sensitivities and does not require critical matching conditions and cancellation constraints.     

High output impedance current-mode third-order Butterworth filter topologies employing unity gain voltage buffers and equal-valued passive components

This paper presents eight new current mode third-order band pass filter topologies employing unity-gain active elements, three resistances and three capacitors. An additional topology is identical to a previously reported one, repeated here for completeness. Using equal passive components, all of the proposed topologies realize third-order BP Butterworth filter function, which can easily be converted to a LP if they are cascaded with an integrator, Therefore, without any component spread the circuits are attractive from the integration point of view. In each of the circuits, except one topology, one of the unity gain cells can be replaced by a second-generation current conveyor to pick up the output current and to obtain a high impedance output. The high output impedance provided by the current conveyor permits easy cascadability for the proposed circuits to construct high-order communication filters. Simulation and experimental results are included to verify theory.     

Differential amplifier input impedance and Blackman's impedance relation

Recently the input impedance of a differential amplifier was derived and discussed. This correspondence derives similar results using a different approach, namely, Blackman's impedance relation, and generalizes earlier observations. The results provide an alternative activeRCrealization of a bilinearRLimpedance. Various all-pass networks are also analyzed.     

电桥测量基础

电桥是精密测量电阻或其他模拟量的一种有效的方法。本文介绍了如何实现具有较大信号输出的硅应变计与模数转换器（ADC）的接口．特别是∑一△ADC。当使用硅应变计时．它是一种实现压力变送器的低成本方案。[编者按]     

Distinguishability in impedance imaging

Impedance imaging systems apply currents to the surface of a body, measure the induced voltages on the surface, and from this information, reconstruct an approximation to the electrical conductivity in the interior. This paper gives a detailed discussion of several ways to measure the ability of such a system to distinguish between two different conductivity distributions. The subtle differences between these related measures are discussed, and examples are provided to show that these different measures can give rise to different answers to various practical questions about system design.     

Quantifying interface states and bulk defects in high‐efficiency solution‐processed small‐molecule solar cells by impedance and capacitance characteristics

The AC properties of high‐efficiency (η = 8.01% under standard 100 mW/cm² AM1.5 illumination) small‐molecule bulk heterojunction (SM BHJ) solar cells (p‐DTS(FBTTh₂)₂/PC₇₀BM) at different DC biases and frequencies of small amplitude (±10 mV) AC signal in the dark at room temperature were investigated in details. We showed the presence of interface states at the heterojunction interface and determined their parameters from the analysis of spectral distributions of real and imaginary components of the measured impedance. The dielectric constant of BHJ ε_BHJ = 2.9 was determined from the geometrical capacitance of totally depleted BHJ layer. We explained quantitatively the effect of interface states and series resistance on the measured C‐V characteristics of the SM BHJ solar cells at both low and high frequencies. The quantitative value of the density of defect states in the bulk N = 1.05 × 10¹⁶ cm⁻³ was determined from the high frequency C‐V characteristic corrected by the effect of the series resistance. Copyright © 2015 John Wiley & Sons, Ltd.     

Origins of the impedance change in impedance cardiography by athree-dimensional finite element model

A three-dimensional finite-element model of the thorax and neck using eight-node trilinear hexahedron elements was constructed to investigate the impedance change associated with various physiological events during systole. A three-dimensional finite-element code was developed to solve the generalized Laplace equation with Dirichlet and homogeneous Neumann boundary conditions. The current in each element as well as potential at each node was calculated. The results suggest that an approximately linear relationship exists between the impedance change and blood volume change in the aorta. This is a promising result since the relationship helps explain the correlation between impedance cardiography and invasive techniques. Impedance changes due to blood volume changes in the aorta and ventricles, the lung-resistivity change, and the blood-resistivity change were calculated for standard impedance electrode configurations     

中介逻辑与中介公理集合论的综述

以中介逻辑演算系统和中介公理集合论为主要内容的中介数学系统是一种在数学基础意义上将精确性量性对象扩展到模糊量性对象的系统,它对数学的逻辑基础和集合论研究产生了重要影响。文中主要从下面3个方面论述：中介数学系统的研究背景;中介数学系统的基本内容及其与经典数学系统的关系,其中简要介绍了中介概念、中介原则、中介逻辑演算系统、中介公理集合论和中介数学系统的研究现状;有关中介逻辑的学术争论,特别围绕中介逻辑是不是一个新逻辑引用了正反双方的意见。此外,还展望了中介数学系统的应用前景。     

变阻抗TEM喇叭天线设计中末端端口阻抗问题的研究

恒阻抗TEM喇叭天线的上、下板之间的间距、板的宽度沿天线轴向呈线性渐变,且喇叭天线的驱动端口、末端端口的宽高比相同。与恒阻抗TEM喇叭天线不同,指数渐变型TEM喇叭天线上下极板之间的间距沿轴向呈指数渐变。研究发现,当指数渐变型TEM喇叭的极板宽度采用不同的渐变形式时,极板宽度线性变化型TEM喇叭天线的驻波比最佳,主射方向远场脉冲峰峰值最大。当天线轴向长度、末端端口高度一定时,天线主射方向远场脉冲峰峰值随着天线末端端口宽度的增大而增大;当末端端口宽度达到一定值时,脉冲峰峰值达到最大值,继续增大末端端口宽度,脉冲峰峰值减小;当天线主射方向远场脉冲峰峰值达到最大值时,天线末端端口阻抗值为215Ω。     

Filtering noncorrelated noise in impedance cardiography

Impedance cardiography (ICG) may be altered by noises as respiration and movement artifacts, mainly during exercise. In this work, a scaled Fourier linear combiner (SFLC) event-related to the R-R interval of ECG is proposed. It estimates the deterministic component of the impedance cardiographic signal and removes the noises uncorrelated to this interval. The impedance cardiographic signal is modeled as Fourier series with the coefficients estimated by the least mean square (LMS) algorithm. Simulations have been carried out to evaluate the filter performance for different noise conditions. Moreover, the method capability to remove uncorrelated noises was also examined in physiological data obtained in rest and exercise, by synchronizing respiration and pedalling with a metronome. Analyzing the ICG power spectrum, it was concluded that the proposed filter could remove the noises that are not synchronized with heart rate     

Antenna impedance in a reentry environment

In-flight measurements of the impedance ofC- andS-band waveguides radiating into a reentry plasma are compared with computed data. The vehicle utilized for the experiment was the Trailblazer II. The measurements were made during the reentry portion of the flight and received byX-band telemetry. The computed data are obtained from the variational formulation for aperture admittance of waveguides radiating into an inhomogeneons plasma medium. The dominant TE10mode is assumed to exist over the aperture. The form employed here utilizes the piecewise solution of Riccatti equations which permits rapid evaluation of the resulting equation for the admittance.