Change In Mutual Inductance Research Articles

An Inductance-Based Sensing System for Bellows-Driven Continuum Joints in Soft Robots.

In this work we present a novel, inductance-based system to measure and control the motion of bellows-driven continuum joints in soft robots. The sensing system relies on coils of wire wrapped around the minor diameters of each bellows on the joint. As the bellows extend, these coils of wire become more distant, decreasing their mutual inductance. Measuring this change in mutual inductance allows us to measure the motion of the joint. By dividing the sensing of the joint into two sections and measuring the motion of each section independently, we are able to measure the overall deformation of the joint with a piece-wise constant-curvature approximation. This technique allows us to measure lateral displacements that would be otherwise unobservable. When measuring bending, the inductance sensors measured the joint orientation with an RMS error of 1.1 °. The inductance sensors were also successfully used as feedback to control the orientation of the joint. The sensors proposed and tested in this work provided accurate motion feedback that would be difficult to achieve robustly with other sensors. This sensing system enables the creation of robust, self-sensing soft robots based on bellows-driven continuum joints.

A Study for Control Power System Load Flow by Shield Control of High-TC Superconducting Cable

Objectives: HTS cable was shown high temperature characteristic of the superconducting tape by sharp increase resistance on fault state. This paper proposes by controlling the HTS shield part to stable transmission in power system. Methods/Statistical Analysis: HTS cable was divided mainly three parts that was former, conductor, and shield part. To be performance the HTS cable designed by comparison low error value with real HTS cable property and, developed by controlling shield parts by using mutual inductance change. Findings: The HTS power cable was controlled load flow by adjusting the shield part. Improved the HTS cable was limited current above 64% better than HTS cable in installed the fault current limiter. Therefore, HTS cable could be improved power stability in the power system. Improvements/Applications: The HTS shield control might be controlled power flow and limited fault current. It wasn’t necessary for installing other device by controlling HTS cable shield part. So, proposed the HTS cable model was applied in economic and effective device in power system.

Comprehensive Analysis and Measurement of Frequency-Tuned and Impedance-Tuned Wireless Non-Radiative Power-Transfer Systems

This paper theoretically and experimentally investigates frequency-tuned and impedance-tuned wireless non-radiative power-transfer (WNPT) systems. Closed-form expressions for the efficiencies of both types of systems are presented as functions of frequency and system (circuit) parameters. In the frequency-tuned system, the operating frequency is adjusted to compensate for changes in mutual inductance that occur for variations of transmitter and receiver loop positions. Frequency-tuning is employed for a range of distances over which the loops are strongly coupled. In contrast, the impedance-tuned system employs varactor-based matching networks to compensate for changes in mutual inductance, and to achieve a simultaneous conjugate impedance match over a range of distances. The frequency-tuned system is simpler to implement, while the impedance-tuned system is more complex, but can achieve higher efficiencies. Both of the experimental wireless non-radiative power-transfer systems studied employ resonant shielded loops as transmitting and receiving devices.

Comprehensive Analysis and Measurement of Frequency-Tuned and Impedance-Tuned Wireless Non-Radiative Power-Transfer Systems

This paper theoretically and experimentally investigates frequency-tuned and impedance-tuned wireless non-radiative power-transfer (WNPT) systems. Closed-form expressions for the efficiencies of both types of systems are presented as functions of frequency and system (circuit) parameters. In the frequency-tuned system, the operating frequency is adjusted to compensate for changes in mutual inductance that occur for variations of transmitter and receiver loop positions. Frequency-tuning is employed for a range of distances over which the loops are strongly coupled. In contrast, the impedance-tuned system employs varactor-based matching networks to compensate for changes in mutual inductance, and to achieve a simultaneous conjugate impedance match over a range of distances. The frequency-tuned system is simpler to implement, while the impedance-tuned system is more complex, but can achieve higher efficiencies. Both of the experimental wireless non-radiative power-transfer systems studied employ resonant shielded loops as transmitting and receiving devices.

Design, Modelling& Simulation of Double Sided Linear Segmented Switched Reluctance Motor

This paper presents the modelling, simulation, and speed control aspects of a 3-phase 6/4 linear switched reluctance motor (LSRM) drives. The Linear switched reluctance motor (LSRM) has never been a popular choice for direct-drive linear motion control system; because it is difficult to control and its output has high torque ripples. It is also due to the fact that the actuator's characteristic is highly dependent on its complex magnetic circuit, which is difficult to model, simulate, and control.Fourier series expression of phase self- inductance under the assumption of negligible mutual effect and various losses is introduced to describe the nonlinear dynamic model of SRM.Simulation results have shown the rationality of model and validity of control strategy. By virtue of MATLAB/SIMULINK, the models of various subsystems are achieved and the modelling procedure is described in detail. Linear segmented switched reluctance motor (LSSRM) using full pitched winding can give 40 - 80% higher torque than conventional SRM for the same frame size. This increase in torque is due to the increase in aligned inductance. However, full pitch winding results in high copper loss, and high active weight. Hence, in this paper, single tooth or concentric winding to replace the full pitch winding of LSSRM is proposed. In order to obtain the same flux paths as with full pitch winding, all the three phases must be excited simultaneously. The torque is produced due to changes in mutual inductance. This method of winding results in reduction of copper, and therefore, weight. With such an arrangement, one phase only requires DC supply.

Electrostatically driven tunable radio frequency inductor

An electrostatically driven tunable radio frequency (RF) inductor with large inductance tuning range consisting of electroplated soft magnetic permalloy (Ni80Fe20 alloy) plate was proposed in this paper. The fabricated tunable inductor exhibits a large tunable inductance range up to 77.8%, together with improved quality factor (Q-factor) at high frequencies. Such tunability of inductance and Q-factor was due to the magnetoelectric coupling effect between the soft magnetic permalloy plate and the spiral inductor, which lead to the magnetic flux of the inductor and mutual inductance change. The concept of tuning inductance by using electroplated soft magnetic permalloy has large potential for wide range RFIC applications.

Simplified analysis and evaluation of drive characteristics of fully-pitched winding reluctance motors

Compared to the conventional SRM, fully-pitched winding reluctance motors have a higher salient ratio for given motor dimensions. In addition, since the generated torque of the motor is determined as the product of the rate of change of mutual inductance with respect to a rotor position and winding current amplitude of the corresponding two phases, the motor is suitable for the bipolar current drives. Accordingly, the conventional general-purpose inverter drive of the fully-pitched winding reluctance motor is possible. In this case, the optimum lead angles of voltage play an important role in obtaining the maximum torque and maximum torque/current ratio operations. In this paper, a scheme for determining the optimum angles of voltage without any measurement, and a method for evaluating the drive characteristics in the design stage are proposed by a combination of simple magnetic and electrical analysis. The effectiveness of the proposed analytical scheme is verified by an experiment using a 400-W prototype fully-pitched winding reluctance motor. © 2000 Scripta Technica, Electr Eng Jpn 134(1): 45–52, 2001

Simplified Analysis and Evaluation of Drive Characteristic of Fully-Pitched Winding Reluctance Motors

Compared to the conventional SRM, fully-pitched winding reluctance motors have a higher salient ratio for a given motor dimensions. In addition, since the generated torque of the motor is determined by a product of the rate of change of mutual inductance with respect to a rotor position and winding current amplitude of the corresponding two phases, the motor is suitable for the bipolar current drives. Accordingly, the conventional general purpose inverter drive of the fully-pitched winding reluctance motor is possible. In this case, the optimum lead angles of voltage plays an important role to obtain the maximum torque and maximum torque/current ratio operations.In this paper, the scheme for determining the optimum angles of voltage without any measurement, and, the method to evaluate the drive characteristics in the design stage are proposed by a combination of simple magnetic and electrical analysis. The effectiveness of the proposed analytical scheme is verified by a experiment using a 400W prototype fully-pitched winding reluctance motor.

Self-Sensing Active Suppression of Vibration of Flexible Steel Sheet

In rolling processes, flexible steel sheet is supported by rollers and is bound to produce structural vibration. This vibration can cause severe problems to surface finish and affect the quality of the product. To overcome these problems, active vibration control has been proposed. This usually requires both sensors and actuators. The location of sensors and actuators plays a very important role in active vibration control. Moreover, a reliable sensor can be very expensive. This paper proposes a self-sensing vibration control using a push-pull type electromagnet to control the transverse vibration of the steel plate. The construction of the electromagnet has two types of coils, namely the bias coil and the control coil. Vibration displacement is estimated by using the mutual inductance change between the bias and the control coils. The estimated signal is proportional to the gap displacement. The proportional and derivative signals are fed back to the control coil to reduce the transverse vibration of the steel sheet. The proposed method is applied to a simple test rig to confirm the capability of the device. The results obtained are showing high possibility for reducing steel sheet vibration.

Fully pitched-winding switched-reluctance and stepping-motor arrangements

The paper introduces the concept of using a fully pitched winding in a switched-reluctance or stepping motor. It is demonstrated that such a winding configuration results in more efficient use of the electric circuit, with each phase contributing to torque for more than half of the cycle of rotation. As a result, for many machine configurations significantly greater torques are predicted for a given frame size. In contrast to the short-pitched windings conventionally employed in such machines, the new configuration is shown to derive virtually all its torque from the rate of change of mutual inductance between phases. A number of different idealised current-excitation patterns are investigated, using both unipolar and bipolar excitation, and the mean output torques produced by the various configurations are compared.

Dynamic strength of armature materials under pulsed current conditions (railguns)

A technique for generating tensile strength versus electrical action curves for railgun armature materials under pulsed current conditions is presented. This technique is capable of imposing high strain rates (>10/sup 3/ sec/sup -1/) under pulse current conditions by electromagnetically expanding a wire formed from a candidate armature material. The strain rate is derived by determining the change in mutual inductance between the expanding test wire and fixed reference wire. The experimental technique and results obtained for aluminum and copper armature materials are described. The results indicate that aluminum and copper armature materials maintain a high percentage of room-temperature tensile strength under actual railgun conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Penetration depths of high T c films measured by two-coil mutual inductances

A fundamental parameter of sample quality in epitaxial films of high Tc oxides is the effective penetration depth λ∥ of the superconducting sheet. A contactless audio-frequency method is described, in which an epitaxial YBa2Cu3O7 film is sandwiched between sets of stacked coils, and the procedure is given for computing the complex sheet impedance and hence λ∥ from the change in mutual inductance produced by screening currents in the film. Temperature dependence of the complex impedance is presented.

Accurate determination of the electrical resistivity from mutual inductance measurements

When a conducting specimen is placed inside a coil, the coil impedance changes. For simple coil and specimen geometries, the impedance change can be related to the electrical resistivity of the specimen. This paper describes a variety of methods for the accurate determination of the resistivity of a cylindrical specimen from the measured change in mutual inductance of a cylindrically symmetric coil assembly. The useful range of resistivity extends from about 3 nΩ⋅cm to above 100 μΩ⋅cm. Using the calibration methods that are described, 1% absolute accuracy is not difficult to obtain even when using a coil system only five coil diameters in length. When compared with calculations for the corresponding infinite specimen and coil problem, the measurements are in disagreement by much more than 1%. Approximate calculations and numerical estimates show that axial field gradients are responsible for these differences when the specimen is more than about twice as long as the coils, and that end effects in the specimen are responsible for the differences when the specimen is short compared to the coil length. The effect of losses other than those in the specimen being studied has also been investigated extensively. We find that in many important experimental circumstances, the conventional procedure of subtracting coil system losses with the specimen absent from those with specimen present can be seriously in error. For instance , if the tail of a metal Dewar, a vacuum can, or the pole faces of an electromagnet are placed so that they intercept some of the return flux of the primary coil, the system losses may not be additive. This occurs because the magnitude of the return flux depends upon the screening currents in the specimen (and hence on the presence or absence of the specimen). This problem is discussed from both an analytical and experimental point of view. An experimental system having very small background losses is described and numerous results on specimens of different lengths and diameters are presented. It can be shown that a radial conductivity variation of about 50% or more can be determined by making measurements at a few frequencies, but that the results are not very sensitive to the functional form of the conductivity variation.

Measurement of resistivity change by a mutual inductance method

The resistivity of a nonferromagnetic conductor can be deduced from the change in mutual inductance between two coils when the sample is inserted. A method is described for measuring mutual inductance over a range of frequencies and this can be used to detect change in resistivities of the order of ± 10−13 Ω cm.

Classical skin effect for the undergraduate laboratory

The author describes how the skin depth in the classical skin effect region can be found by measurement of the change in mutual inductance between two coaxial coils, caused by a metal sample being brought into the inner one coil of the coils.

Superconducting Transition Width in Pure Gallium Single Crystals

The superconducting transition in 99.9999% pure gallium single crystals was investigated. The change in mutual inductance at 23 Hz of a pair of coils containing the sample was used to monitor the transition. In long, thin single crystals, the transition was 90% complete in a temperature interval of 2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ \ifmmode^\circ\else\textdegree\fi{}K, a smaller superconducting transition width than is usually reported in the literature. This transition width corresponds to a superconducting penetration depth at 0\ifmmode^\circ\else\textdegree\fi{}K of ${\ensuremath{\lambda}}_{0}\ensuremath{\le}3.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ cm, in agreement with the nuclear-resonance data of Hammond and Knight. Several factors were investigated for possible effects on the transition width. For pure single crystals, the dominant contribution to the transition width was correlated to the relative lengths of the sample and the primary coil. Samples shorter than the primary coil showed substantially broadened transitions, probably caused by a complex nucleation of the superconducting state at the blunt ends of the specimens in the weak (${10}^{\ensuremath{-}2}$-${10}^{\ensuremath{-}3}$-G) primary-coil magnetic field. All effects of damage on the transition width were removed by 40 h of room-temperature annealing, and the transition temperature from specimen to specimen of cut and annealed specimens was the same to within a temperature interval at least as small as the transition width. These results support the suggestion by Gregory, Sheahen, and Cochran that the critical-field curve of gallium may be used as a reliable secondary temperature standard below ${T}_{c}=1.083$\ifmmode^\circ\else\textdegree\fi{}K.

Measurement of electrical resistivity by a mutual inductance method

The resistivity of a sample can be deduced from the change in mutual inductance between two coils when the sample is inserted. It is shown that with simple equipment for measuring mutual inductance over a range of frequencies, the method can be used to measure resistivities from 2 × 10-9 ohm cm upwards, and the necessary functions are tabulated.

An improved inductance method for measuring susceptibilities of small paramagnetic specimens at low temperatures

An apparatus is described with which the susceptibilities of small paramagnetic specimens can be determined at temperatures between 77 and 1.8° K. The measurements are made in terms of the change of mutual inductance produced by moving a specimen inside a coil system, using a Hartshorn bridge operating at 175 c/s to measure the inductance. The chief advantage of this type of apparatus is its simplicity of operation, since it involves no delicate moving parts. The sensitivity and reproducibility of the apparatus were investigated using a specimen of manganous ammonium sulphate and it was found that susceptibilities of the order of 3 × 10-6 c.g.s. units could be measured to an accuracy of 1%. Sources of error are discussed.

On the Measurement of Amplification Given by Triode Amplifiers at Audible and at Radio Frequencies

The measurement of amplification at audible frequencies which is described is a mutual inductance method, the alternating voltage applied between the filament and grid of the first valve being varied by quickly changing the connections to an air-core transformer having two secondaries at right angles, which secondaries are capable of rotation so as to give any desired ratio of the mutual inductances between the primary and the respective secondaries. The source of alternating voltage is a triode circuit having such capacity and inductance in the oscillatory portion as to give currents of a sonic frequency. The standard intensity of note is such as to enable signals to be read with comfort, and is obtained by adjustment of the source of alternating current. The first note is obtained when the telephone is in the anode circuit of an auxiliary valve, and the second when the telephone is transferred to the anode circuit of the last valve of the amplifying set, changes also being made in the applied alternating voltage, and in the connections between the valve circuits. All of these changes are brought about by a six-brush switch in a fraction of a second, so that readings are quickly obtained. The method is compared with a modification of the shunted telephone method, and very good agreement is obtained when the amplifying values are comparatively low. For values of a high order such as 200, it is shown that the two methods are not likely to give the same results, the method described in the Paper being the better one. In the measurement of amplification of a radio-frequency amplifier an undamped train of oscillations is broken up into groups of sonic frequency by shunting intermittently the condenser in the oscillatory circuit by an inductance of low resistance. A sonic train of oscillations is thus produced. The receiving circuit is very similar to that used for audible frequency amplification, but the measurement of the amplifying power is made by quickly varying the current at the source, and not by a change of mutual inductance, between the two circuits.