Inductive Position Sensor Research Articles

Компенсация формы неидеальных сигналов индуктивных датчиков положения ротора для бесконтактных двигателей постоянного тока

Компенсация формы неидеальных сигналов индуктивных датчиков положения ротора для бесконтактных двигателей постоянного тока

Frequency response characterization of ironless inductive position sensors with long cables

The two linear position sensors used to determine the position of the European Organization for Nuclear Research; Large Hadron Collider collimator’s jaws with respect to the beam are the linear variable differential transformer and the ironless inductive position sensor. The latter was designed as an alternative to the former since the linear variable differential transformer exhibits a position error in magnetic environments. The ironless inductive position sensor is an air cored, high-precision linear position sensor, which is by design immune to external DC or slowly varying magnetic fields. Since the ironless inductive position sensor is required to have no on-board electronics, the raw signal has to be carried through long cable lengths and this may lead to performance degradation. This paper focuses on a set of experimental measurements conducted to assess the ironless inductive position sensor’s sensitivity at different frequencies with long cable lengths. This is critical for the sensor`s correct operation in the Large Hadron Collider`s collimators. Furthermore, to gain a better understanding, the ironless inductive position sensor’s frequency response is compared with a commercial off-the-shelf linear variable differential transformer.

Influence of External Conductive Objects on the Performance of an Ironless Inductive Position Sensor

The ironless inductive position sensor (I2PS) is a novel device that measures high-precision linear position without being affected by radiation and external magnetic fields. Built on the basis of the linear variable differential transformer, the I2PS senses the variation of flux linkage between the supply and sense coils which is related to the linear position of the moving coil. This paper characterizes the magnetic performance of the I2PS through a detailed analysis of the impact of axisymmetrical external conductive objects on the sensor. This characterization is performed through a set of finite element simulations and through dedicated experiments. Axisymmetrical conductive objects result in offset voltages, but the differential measurement techniques combined with high-resolution calibration curves mitigate this effect.

An Inductive 2-D Position Detection IC With 99.8% Accuracy for Automotive EMR Gear Control System

In this paper, the analog front end (AFE) for an inductive position sensor in an automotive electromagnetic resonance gear control applications is presented. To improve the position detection accuracy, a coil driver with an automatic two-step impedance calibration is proposed which, despite the load variation, provides the desired driving capability by controlling the main driver size. Also, a time shared analog-to-digital converter (ADC) is proposed to convert eight-phase signals while reducing the current consumption and area to 1/8 of the conventional structure. A relaxation oscillator with temperature compensation is proposed to generate a constant clock frequency in vehicle temperature conditions. This chip is fabricated using a 0.18- $\mu \text{m}$ CMOS process and the die area is 2 mm $\times 1.5$ mm. The power consumption of the AFE is 23.1 mW from the supply voltage of 3.3 V to drive one transmitter (Tx) coil and eight receiver (Rx) coils. The measured position detection accuracy is greater than 99.8 %. The measurement of the Tx shows a driving capability higher than 35 mA with respect to the load change.

Evaluation Algorithms for Linear Position Sensors Assisted by Artificial Neural Network

An artificial neural network assisted compact linear inductive position sensor is presented. The sensor operates with a long primary printed circuit coil excited with periodically alternating current, and with multiple secondary printed circuit coils possessing different induced voltages as a position of a metallic or resonant target moving along the coil system. The secondary coil signals are phase sensitively demodulated, digitized and passed to the input layer of an artificial neural network trained to estimate the position of the target, its distance from the sensor and the signal quality.

Performance Analysis of the Ironless Inductive Position Sensor in the Large Hadron Collider Collimators Environment.

The Ironless Inductive Position Sensor (I2PS) has been introduced as a valid alternative to Linear Variable Differential Transformers (LVDTs) when external magnetic fields are present. Potential applications of this linear position sensor can be found in critical systems such as nuclear plants, tokamaks, satellites and particle accelerators. This paper analyzes the performance of the I2PS in the harsh environment of the collimators of the Large Hadron Collider (LHC), where position uncertainties of less than 20 µm are demanded in the presence of nuclear radiation and external magnetic fields. The I2PS has been targeted for installation for LHC Run 2, in order to solve the magnetic interference problem which standard LVDTs are experiencing. The paper describes in detail the chain of systems which belong to the new I2PS measurement task, their impact on the sensor performance and their possible further optimization. The I2PS performance is analyzed evaluating the position uncertainty (on 30 s), the magnetic immunity and the long-term stability (on 7 days). These three indicators are assessed from data acquired during the LHC operation in 2015 and compared with those of LVDTs.

Impact evaluation of environmental and geometrical parasitic effects on high-precision position measurement of the LHC collimator jaws

Measuring the apertures of the Large Hadron Collider (LHC) collimators, as well as the positions of their axes, is a challenging task. The LHC collimators are equipped with high-precision linear position sensors, the linear variable differential transformers (LVDTs). The accuracy of such sensors is limited by the peculiar parasitic effect of being rather sensitive to external magnetic fields. A new type of inductive sensor, the Ironless Inductive Position Sensor (I2PS), that keeps the advantages of the LVDTs but is insensitive to external magnetic fields has been designed, constructed, and tested at CERN. For this sensor, a detailed description of parasitic effects such as high-frequency capacitances and the presence of conductive shields and electric motor, in the surroundings is given, from analytical, numerical, and experimental viewpoints. In addition, proof is given of the I2PS’s radiation hardness. The aim of this paper is to give a complete and exhaustive impact evaluation, from the metrological viewpoint, of these parasitic effects on these two fundamental sensor solutions.

Analysis and Validation of a Planar High-Frequency Contactless Absolute Inductive Position Sensor

This paper presents a low cost precise and reliable inductive absolute position measurement system. It is suitable for rough industrial environments, offers a high inherent resolution (0.1%-0.01% of measurement range), can measure target position over a wide measurement range, and can potentially measure multiple target locations simultaneously. The basic position resolution is improved by adding two additional finer pitched receive channels. The sensor works on principles similar to contactless resolvers. It consists of a rectangular antenna printed circuit board and a passive LC resonant circuit. A mathematical model and the equivalent circuit of this kind of sensor are explained in detail. Such sensors suffer from transmitter to receiver coil capacitive crosstalk, which results in a phase sensitive offset. This crosstalk will be analyzed by measurements. Moreover, the mechanical transducer arrangement, the measurement setup, and the measured results will be presented.

Contactless high frequency inductive position sensor with DSP read out electronics utilizing band-pass sampling

This paper presents a precise, reliable, low cost and contactless inductive absolute position measurement system for rough industrial environments. It offers a high inherent resolution (0.04 % of antenna length), and measures absolute position over a relative wide measurement range. The main property for this kind of sensor is its good immunity to external noise and target misalignment off the measurement axis. The measurement range and the precision are extended by adding additional and finer pitched receive coils. This sensor works on similar principles as resolvers but consists of a rectangular antenna PCB, a small moveable passive LC resonant circuit and a signal processing unit. Furthermore, the used read out electronics utilizes under-sampling to demodulate the sensor output signals and the corresponding position is estimated from a lookup table (LUT) implemented on a digital signal processor (DSP) to avoid singularities in the inverse tangent and cotangent calculation. Moreover, the mechanical transducer arrangement, the signal condition electronics design and measurement results of the transmitter to receiver signal coupling and relative position error will be presented.

Modeling and Compensation of Thermal Effects on an Ironless Inductive Position Sensor

The ironless inductive position sensor can be the ideal candidate for linear position sensing in harsh environment and in the presence of external magnetic fields. Starting from the validated electromagnetic characteristics, this paper presents a model of thermal effects influencing the sensor's position reading and an effective algorithm to compensate them. The compensation is performed without affecting the nominal sensor's functioning and without using additional temperature probes, which would complicate the sensor's assembly. The model constitutes the basis of this algorithm, which is then validated through experimental measurements on a custom ironless position sensor prototype.

Project of Economically Profitable Technological Process of Production of Rotor and Stator Plates of Inductive Position Sensor by Blanking and Roll Bending

Project of Economically Profitable Technological Process of Production of Rotor and Stator Plates of Inductive Position Sensor by Blanking and Roll Bending

Modeling of High-Frequency Electromagnetic Effects on an Ironless Inductive Position Sensor

The ironless inductive position sensor (I2PS) is a five-coil air-cored structure that senses the variation of flux linkage between supply and sense coils and relates it to the linear position of a moving coil. In air-cored structures, the skin and proximity effect can bring substantial variations of the electrical resistance, leading to important deviations from the low-frequency functioning. In this paper, an analysis of the effect of high-frequency phenomena on the I2PS functioning is described. The key-element is the modeling of the resistance as a function of the frequency, which starts from the analytical resolution of Maxwell's equations in the coil's geometry. The analysis is validated by means of experimental measurements on custom sensor coils. The resulting model is integrated with the existing low-frequency analysis and represents a complete tool for the design of an I2PS sensor, framing its electromagnetic behavior.

Real-Time High-Precision Reading Algorithm for the Ironless Inductive Position Sensor

This paper presents a novel reading algorithm for an ironless inductive position sensor which exhibits immunity to single-frequency interference (both for high and low frequency signals). This algorithm is based on the three-parameter sine fitting, whose performances have been enhanced with proper windowing function design. The proposed algorithm exhibits high precision and suitability for real-time implementation. The performances of the new algorithm are tested on simulated and measured signals and the results are discussed in detail. The algorithm has been finally tested and validated on a real-time target.

Novel Solution for Flexible Inductive Position Sensor

Novel Solution for Flexible Inductive Position Sensor

Design optimization of an ironless inductive position sensor for the LHC collimators

The Ironless Inductive Position Sensor (I2PS) is an air-cored displacement sensor which has been conceived to be totally immune to external DC/slowly-varying magnetic fields. It can thus be used as a valid alternative to Linear Variable Differential Transformers (LVDTs), which can show a position error in magnetic environments. In addition, since it retains the excellent properties of LVDTs, the I2PS can be used in harsh environments, such as nuclear plants, plasma control and particle accelerators. This paper focuses on the design optimization of the sensor, considering the CERN LHC Collimators as application. In particular, the optimization comes after a complete review of the electromagnetic and thermal modeling of the sensor, as well as the proper choice of the reading technique. The design optimization stage is firmly based on these preliminary steps. Therefore, the paper summarises the sensor's complete development, from its modeling to its actual implementation. A set of experimental measurements demonstrates the sensor's performances to be those expected in the design phase.

Inductive verses capacitive sensors

Both capacitive and inductive position sensors use a non-contact technique to measure position; both use AC electrical phenomena and both can be built using printed circuit boards. This article looks at the fundamental physics behind each technique and outlines the consequent strengths and weaknesses of each approach.

Electromagnetic Analysis and Validation of an Ironless Inductive Position Sensor

The ironless inductive position sensor is a linear position sensing structure, which exhibits intrinsic immunity to external magnetic fields since it is characterized by air-cored windings. This new solution may be of major interest for applications where external magnetic fields can be a source of interference. In this paper, an analytical model of the working principle of the sensor is proposed. The effect of the moving coil flux on the overall sensed magnetic flux is described. The model is preliminarily verified by simulations on a finite-element structure of the sensor, in order to assess its soundness. Finally, experimental measurements on a custom sensor's prototype give the definitive benchmarking of the model as a valid design tool, in the framework of the design and synthesis of the device.

Optimization and Modeling of Ink-Jet Printed Flexible Position Sensor

This paper presents how geometrical and technological parameters of inductive angular position sensor, fabricated on flexible substrate, influence its characteristics. In our earlier work, the angular position sensor has been already presented but for 60° stroke. In presented work, the design and optimization have been performed for 90° stroke, which is extensively used, for example, in automotive applications. For three different designs of meander rolled coils, width of segments, substrate thickness and relative distance between outer and inner coils have been changed in order to find optimal sensor structure. The proposed sensor is low-cost, easily fabricated and its parameters can be adapted for different angular strokes and applications.

Characterization of Magnetic Immunity of an Ironless Inductive Position Sensor

The ironless inductive position sensor is a novel linear position-sensing device that should exhibit immunity to external magnetic fields while simultaneously guaranteeing high-precision measurements in harsh environments. This paper focuses on the characterization of the sensor's working principle and magnetic field immunity. The sensor is tested, with both voltage and current supply, with different dc and slowly varying magnetic field patterns in order to prove its immunity and analyze the differences and similarities between the two supply cases. The measurements are performed with a test bench on a custom prototype, which is especially manufactured for this purpose.

A Compact Inductive Position Sensor Made by Inkjet Printing Technology on a Flexible Substrate

This paper describes the design, simulation and fabrication of an inductive angular position sensor on a flexible substrate. The sensor is composed of meandering silver coils printed on a flexible substrate (Kapton film) using inkjet technology. The flexibility enables that after printing in the plane, the coils could be rolled and put inside each other. By changing the angular position of the internal coil (rotor) related to the external one (stator), the mutual inductance is changed and consequently the impedance. It is possible to determine the angular position from the measured real and imaginary part of the impedance, in our case in the frequency range from 1 MHz to 10 MHz. Experimental results were compared with simulation results obtained by in-house developed software tool, and very good agreement has been achieved. Thanks to the simple design and fabrication, smaller package space requirements and weight, the presented sensor represents a cost-effective alternative to the other sensors currently used in series production applications.