Snezana M. Djuric

A Novel Approach to Extending the Linearity Range of Displacement Inductive Sensor

This paper presents a meander-type displacement inductive sensor, usable for the detection of small displacements (less than 0.5 mm) in the plane. It also describes design, realization, and the input inductance measurement of sensor. A displacement in two directions can be detected by using two sensor elements, each having a pair of meander coils. In each pair, one of the coils is fixed and between its terminals the input inductance was measured, while the other coil is short-circuited. If one coil is moved above the other, in directions of x - and z -axes, coupling between the coils will change, as well as the input inductance, which serves as a measure of displacement. In order to achieve better linearity of the sensor, longitudinal gaps are inserted in the middle of each conductive segment of one fixed coil. Four sets of inductive sensors were realized: without gap and with three different gaps. Planar, low-cost PCB technology was chosen for our prototype. In addition, an improved model of the inductive sensor is proposed. The input inductance of displacement sensor was calculated and compared with measured values. A good agreement was found.

Design, Modeling, and Analysis of a Compact Planar Transformer

This paper presents a new design of a planar transformer. Over the surface of a flat core, meander-type design was engraved, so that symmetrically adjusted primary and secondary coils, of the same meander-type, can fit into the engraved design. Primary and secondary coils were covered with another flat core consequently forming a compact planar transformer. Windings of primary and secondary coils are printed on both sides of PCB. Conductive stripes of a winding from upper and bottom layer are connected by vias. The transformer was analyzed when the primary and secondary coils were without a core and with a core. High frequency parameters of the transformer were obtained by finite element modeling software and Impedance Analyzer HP4194A in the frequency range from 50 kHz to 1 MHz. The transformer is intended to be used in DC-DC converters (for switching frequency up to several hundred kHz).

Inductive Displacement Sensor for Force Measuring in Humanoid Robotic Application: Testing the Invariance on Angular Displacement

Abstract— A planar displacement inductive sensor, usable in robotics, is presented in the paper. The sensor is composed of two sensor elements. The first sensor element detects vertical displacement while the second sensor element detects horizontal displacement. Combining information from these two sensor elements, it is possible to determine displacement in a plane. Sensor element is a pair of meander coils. One coil is a fixed coil and has the input while the other coil is short-circuited and moves in x-z plane. The variation of input inductance between coils serves as a measure of displacement. The goal of this paper is to show that the variation of the input inductance is invariant to angular displacement of a moving coil, which is important for implementation of the sensor in humanoid robot’s foot. Calculated results were obtained using a new simulation tool developed in MATLAB.

Performance Analysis of a Planar Displacement Sensor With Inductive Spiral Coils

In this paper, a planar displacement sensor with inductive spiral coils is presented. The sensor is composed of two inductive coils of spiral shape. One coil is a stationary coil with input terminals, whereas the other coil is a moving (short-circuited) coil. The moving coil physically moves with respect to the stationary coil in x-z and y-z planes. The input inductance changes when the moving coil moves with respect to the stationary coil and it is measured between the terminals of the stationary coil. The inductive operating principle of the sensor was tested using the prototypes fabricated in printed circuit board technology. Two prototypes were designed and fabricated: the prototype without a gap in the stationary coil and the prototype with the gap inserted in the segments of the stationary coil.

A Compact Planar Transformer With an Improved Winding Configuration

A compact planar transformer with an improved winding configuration has been designed and fabricated. Meander-type design was engraved over the surface of a planar ferrite core, so that the primary and secondary windings can fit into the engraved design. The planar core, with the primary and secondary windings fit into it, was covered with another ferrite core, thus forming a compact planar transformer. Apical type AV polyimide film of 0.025 mm thickness is used between the windings to prevent short circuit. A coupling coefficient of >0.93 was achieved, while the primary and secondary inductance was ~1600 nH. A coupling coefficient for air core transformer with the windings of identical geometry was >0.35 and the inductance of the windings near 160 nH. Fabricated transformer prototype has significantly higher coupling coefficient and inductance of the windings in comparison with the previously developed planar transformer of the similar design.

A novel application of planar‐type meander sensors

Purpose – The purpose of this paper is to test the measurement performances of a planar‐type meander sensor installed in robot foot in order to examine its potential application as ground reaction force sensor.Design/methodology/approach – A planar‐type meander sensor is composed of two pairs of meander coils. Variation of input inductance between coils serves as a measure of small displacements in a plane. Pairs of meander coils are installed in an actuated robot foot to measure displacements proportional to normal or tangential components of ground reaction force which acts upon the foot. The sensor was modeled by the concept of partial inductance and a new simulation tool was developed based on this concept.Findings – Pairs of meander coils were tested against angular displacements, and results showed that the sensor gives correct information about displacement regardless how the foot touches the ground with its whole area. Deviations between position of computed and real acting point of ground reactio...

Analysis of the Coupling Effect in Different Meander-Type Winding Planar Transformers

In this paper, planar printed-circuit board (PCB) transformers with different winding arrangements are presented. Three different arrangements of the primary and the secondary meander-type windings are designed and fabricated. The electrical parameters of the transformers for all three designs are analyzed and compared. A significant increase of inductance of the primary and the secondary winding is achieved with an appropriate meander-type winding arrangement. In the frequency range of interest, the inductance is approximately 145 nH for the first design, whereas the inductance is approximately 1250 nH for the second and the third design. The coupling coefficient is 0.14 for the first design, whereas it is around 0.9 for the second and the third design. The transformer of the proposed design is to be used in low-power DC/DC converters; therefore, the core with high permeability Ferroxcube 3C90 was chosen. In addition, the transformers of the same winding arrangements were tested with Ferroxcube 3F3 core.

Displacement inductive sensor: Simulation tool algorithm

This paper presents a planar displacement inductive sensor for the detection of small displacements (less than 0.5 mm) in a plane, usable in robotics. It also describes design, realization and the input inductance measurement of the sensor. Displacement in two directions could be detected using two sensor elements. Each element consists of a pair of meander coils. The variation of input inductance between coils serves as a measure of displacement. In order to achieve a wider measurement range of the sensor, gaps were inserted in a coil of sensor element. An additional extending of the measurement range was achieved by analyzing structures with less turns of meander coils, as well increasing width of conductive segments of the coil with inserted gaps. A new simulation tool in MATLAB for evaluation of the input impedance of the sensor was developed. A brief explanation of simulation tool algorithm was presented.

Characterization and modelling of miniature ferrite transformer for high frequency applications

Purpose – Significant achievements in ferrite material processing enable developments of many ferrite devices with a wide range of power levels and working frequencies, which make demands for new characterization and modelling methods for ferrite materials and components. The purpose of this paper is to introduce a modelling and measurement procedure, which can be used for the characterization of two‐port ferrite components in high frequency range.Design/methodology/approach – This paper presents a commercially available ferrite component (transformer) modelling and determination of its electrical parameters using in‐house developed software. The components are measured and characterized using a vector network analyzer E5071B and adaptation test fixture on PCB board. The parameters of electrical equivalent circuit of the ferrite transformer parameters are compared with values extracted out of measured scattering parameters.Findings – A good agreement between modelled and extracted electrical parameters of...

Detection of ground reaction force using a miniaturized inductive displacement sensor

In this paper, we present a miniaturized version of a previously developed ground reaction force sensor. The sensor is composed of two pairs of meander coils detecting displacement in a plane. One pair of coils determines vertical displacement, proportional to normal force distribution, while the other pair of coils determines horizontal displacement, proportional to tangential force distribution. The advantage of miniaturized sensor is easier implementation in the foot of humanoid robot due to its dimensions. A new simulation tool was developed to accurately calculate the input inductance variation.