Self-Balancing Signal Conditioning Circuit for a Novel Noncontact Inductive Displacement Sensor
TL;DR: Error analysis and simulation studies presented here bring out the pitfalls that have to be avoided to obtain an optimal design for linear or angular displacement sensing.
Abstract: A noncontact inductive type displacement sensor is presented here. The sensor is realized with an inductive voltage divider possessing a floating wiper operated by a self-balancing feedback type signal conditioning circuit. The output of the self-balancing signal conditioning circuit is: 1) linear to the displacement of the floating wiper and 2) independent of the coupling capacitance that arises due to the air gap between the inductive element and the floating wiper. Error analysis and simulation studies presented here bring out the pitfalls that have to be avoided to obtain an optimal design for linear or angular displacement sensing. Experimentation on an emulated sensor and results obtained from a prototype angle sensor built and tested establish the efficacy of the proffered technique.
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TL;DR: This article presents a PM linear resolver that generates orthogonal back-EMFs as the sinusoidal and cosine (SIN/COS) signals and the train position can be measured by decoding the PM back- EMF.
Abstract: In the maglev train electric drive system, the linear electric machine is a welcome solution. However, for long railways, the mover position measurement is an issue, especially when the train speed is very high, e.g., 600 km/h. The position measurement method of the mover must be simple and precise at high speeds while maintaining a low cost for industrial applications. The principle of the stator permanent magnet (stator-PM) machine provides evidence that the magnets and windings can be mounted on the mover of the linear resolver, leaving a simple secondary-side structure on the railway. With this idea, this article presents a PM linear resolver that generates orthogonal back-EMFs as the sinusoidal and cosine (SIN/COS) signals. The train position can then be measured by decoding the PM back-EMF. On the other hand, the high-frequency injection is imposed to solve the mover position measurement at zero speed and low speed. This PM linear resolver is prototyped with printed circuit board windings instead of regular coil windings. The dedicated decoding firmware is developed to evaluate the measurement performance up to 60 km/h in the lab setup.
19 citations
Additional excerpts
...Some Mega Hz solutions [14]–[16] are proposed for rotary and linear resolvers, in which the super HF signals are applied to the position measurement, providing precise rotor/mover position information regardless of...
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TL;DR: In this article, a direct digital output non-contact inductive type displacement transducer employing the popular successive approximation register (SAR) method of conversion is presented, where the digital output is proportional to the displacement of the contactless (floating) wiper and is unaffected by the variations in the coupling capacitor that is formed between the Wiper and the inductive element.
Abstract: A direct digital output non-contact inductive type displacement sensor whose principle of operation alone was presented earlier, is analyzed to ascertain parameters that influence the errors in the output. Further, its efficacy is established through results obtained from a prototype unit built and tested. The proposed direct digital output non-contact inductive displacement transducer employs the popular successive approximation register (SAR) method of conversion. The digital output is proportional to the displacement of the contactless (floating) wiper and is unaffected by the variations in the coupling capacitor that is formed between the wiper and the inductive element. Test results on a prototype transducer indicated a worst-case error of 0.9 %.
6 citations
Cites background from "Self-Balancing Signal Conditioning ..."
...The self-balancing scheme proposed in [6], [7] uses a voltage-controlled amplifier (VCA) and provides an analog output that is independent of the value of Cc....
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...While the output in [7], is affected by the gain and offset errors...
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TL;DR: This model adopts a non-linear polynomial algorithm rather than the simple linear Look-Up Table (LUT) method, which provides more accurate distance estimation compared to the previous work and achieves real-time and high-accuracy computation within a wide temperature range with low hardware resource consumption.
Abstract: The non-linear characteristic of a non-contacting Inductive Proximity Sensor (IPS) with the temperature affects the computation accuracy when measuring the target distance in real time. The linear model based method for distance estimation shows a large deviation at a low temperature. Accordingly, this paper presents a non-linear measurement model, which computes the target distance accurately in real time within a wide temperature range from −55 °C to 125 °C. By revisiting the temperature effect on the IPS system, this paper considers the non-linear characteristic of the IPS measurement system due to the change of temperature. The proposed model adopts a non-linear polynomial algorithm rather than the simple linear Look-Up Table (LUT) method, which provides more accurate distance estimation compared to the previous work. The introduced model is fabricated in a 0.18 μm Complementary Metal Oxide Semiconductor (CMOS) process and packaged in a CQFN40. For the most commonly used sensing distance of 4 mm, the computed distance deviation of the Application-Specific Integrated Circuit (ASIC) chips falls within the range of [−0.2,0.2] mm. According to the test results of the ASIC chips, this non-linear temperature compensation model successfully achieves real-time and high-accuracy computation within a wide temperature range with low hardware resource consumption.
5 citations
Cites background from "Self-Balancing Signal Conditioning ..."
...A novel noncontact inductive displacement sensor [16] is realized with a self-balancing signal conditioning circuit, whose output is linear to the displacement of the floating wiper....
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01 Dec 2017
TL;DR: The topology of a successive approximation type digital converter is suitably altered so that a floating-wiper inductive displacement sensor becomes an integral part of the SADC.
Abstract: A successive approximation type direct displacement to digital converter suitable for a floating-wiper inductive displacement sensor is proposed here. The topology of a successive approximation type digital converter (SADC) is suitably altered so that a floating-wiper inductive displacement sensor becomes an integral part of the SADC. The successive approximation logic results in the final digital output directly proportional to the displacement of the floating wiper. The hardware and logic are so designed that the final digital output is independent of the interfering inputs. The results obtained from simulation studies establish the efficacy of the proposed technique.
2 citations
Cites background from "Self-Balancing Signal Conditioning ..."
...The coupling capacitor Cc can and will vary as the wiper moves (popularly known as jitter) and hence special signal conditioning is required to make the output independent of this coupling capacitance [4] – [7]....
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...The scheme presented earlier [6], [7] requires a voltage controlled amplifier (VCA) and hence exhibits appreciable nonlinearity....
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...INTRODUCTION Inductive displacement sensors are widely employed for the measurement of linear or angular displacements [1] – [7]....
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TL;DR: In this paper , the authors analyzed the sensor's working principle and designed some radial sensors with different nominal air gaps and coil turns, and studied the effects of the nominal air gap and coil turn on the sensor coil's output voltage and sensitivity through the finite element simulation and experiments.
Abstract: The self-inductive displacement sensor has been widely used in active magnetic bearing systems for its excellent performance. However, there is a lack of studies on this sensor’s output characteristics according to the voltages directly from the coils, not from the processing circuit. Therefore, it needs to be further studied to improve the sensor theory and provide technical guidance for the sensor design. This paper analyzed the sensor’s working principle and designed some radial sensors with different nominal air gaps and coil turns. Then the effects of the nominal air gap and coil turns on the sensor coil’s output voltage and sensitivity were studied through the finite element simulation and experiments. According to the results, the number of coil turns could hardly affect the sensor’s static output voltage and sensitivity. The sensor sensitivity in the linear measurement range is proportional to the reciprocal of the nominal air gap length, but it is much less than the theoretical value. The results of this paper provide a valuable reference for the theoretical analysis and structural design of the self-inductive displacement sensor.
1 citations
References
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Book•
29 Dec 1998
TL;DR: In this paper, the authors present a characterization of measurement characteristics, including time and frequency measurements, as well as the properties of different types of measurements, such as thermal, chemical, and signal processing.
Abstract: Measurement Characteristics. Spatial Variables Measurement. Time and Frequency Measurement. Mechanical Variables Measurement Solid. Mechanical Variables Measurement Fluid. Mechanical Variables Measurement Thermal. Electromagnetic Variables Measurement. Optical Variables Measurement. Radiation Measurement. Chemical Variables Measurement. Biomedical Variables Measurement. Signal Processing. Displays. Control. Appendices. Index.
1,010 citations
"Self-Balancing Signal Conditioning ..." refers methods in this paper
...INDUCTIVE type sensors are widely used for the measurement of physical quantities such as linear or angular displacement by utilizing the changes in the inductance of a coil [1]....
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TL;DR: In this paper, the authors present a systematic, complete, and consistent presentation of the technological innovations, recent implementations and current trends regarding the analog distance and travel sensing offered by noncontacting inductive sensors for industrial applications.
Abstract: Noncontacting inductive sensors are applicable on a large scale for position detection or travel measurement in industrial applications. Reasons for such broad acceptance in many sectors of industry are noncontact and wear-free sensing of the target (any metal object), reliability and robustness, resistance to fouling, water tightness and compact size. The present work is intended to be a systematic, complete, and consistent presentation of the technological innovations, recent implementations and current trends regarding the analog distance and travel sensing offered by noncontacting inductive sensors for industrial applications. It starts with the fundamentals of inductive sensing and presents the physical basics gained by modern analytic and simulation methods, as well as high-level integrated circuits for inductive sensors. The following sections deal with present-day inductive analog proximity sensors and with the distinctive technological innovation offered by the new inductive linear displacement sensors and with miniaturization results achieved through consistent integration.
112 citations
"Self-Balancing Signal Conditioning ..." refers background in this paper
...Such sensors are in vogue for a variety of applications such as automation [2], underwater lift-gate control [3], force measurement in robots [4], absolute position sensing [5], and position control in mechatronic systems [6]....
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01 Jan 1995
TL;DR: In this paper, a very linear oscillator is used in the processing circuit to convert the position quantity to a period-modulated signal which can be read out directly by a microcontroller.
Abstract: A novel smart resistive-capacitive angular position sensor is presented. The main advantages of this low-cost system are its simplicity, high stability and high reliability. A very linear oscillator is used in the processing circuit to convert the position quantity to a period-modulated signal which can be read out directly by a microcontroller. The system does not need an A/D converter. The nonlinearity of the smart angular position sensor system is less than /spl plusmn/0.3% (/spl plusmn/0.9/spl deg/) over the range of 270. >
56 citations
"Self-Balancing Signal Conditioning ..." refers methods in this paper
...This circuit can also be used as an interface for the resistive potentiometric displacement sensor with a floating slide [7]....
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...The issues mentioned above are equally applicable to the conventional resistive potentiometer type displacement sensors and were solved by using a resistive displacement sensor with a floating slide [7]....
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TL;DR: In this paper, a noncontact, low-cost, and reliable inductive sensor for angular displacement measurement is presented. But the sensor is not suitable for work in harsh industrial environments.
Abstract: This paper introduces a noncontact, low-cost, and reliable inductive sensor for angular displacement measurement. It is suitable to work in harsh industrial environments. The sensor has simple structure consisting of three key parts: a ferromagnetic stator, which is a pure plane; a ferromagnetic rotor, which has face slots; and four layers of planar copper coils, including primary and secondary coils. Primary coils are supplied with two orthogonal 4000-Hz ac, and secondary coils output a signal whose phase is proportional to angular displacement. Primary coils are designed with sinusoidal shape, so that magnetic field between the stator and rotor has approximately sinusoidal distribution, and finally linearity between the phase variation of output signal and angular displacement is well helped by this design. The structure and working principles of the sensor are explained in detail. Moreover, a sensor model was simulated to verify the feasibility of the sensor working principles and a sensor prototype was designed for actual experiment. At last actual experiment results are given and analyzed, showing that the sensor prototype has achieved accuracy better than ±12 arcsec in the range of 0°-360°, and this kind of sensor may have a better performance by improving the layout of primary coils and front-end signal-process circuit.
46 citations
"Self-Balancing Signal Conditioning ..." refers methods in this paper
...Schemes such as oscillators for rotary potentiometers [9]–[11], resonant oscillator bridges [5], and phase measurement [12] have been proposed for inductive sensors but they are not suitable for an IVD with a floating wiper....
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TL;DR: This paper presents a low cost precise and reliable inductive absolute position measurement system that is suitable for rough industrial environments, offers a high inherent resolution, can measure target position over a wide measurement range, and can potentially measure multiple target locations simultaneously.
Abstract: 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.
44 citations
"Self-Balancing Signal Conditioning ..." refers background or methods in this paper
...Such sensors are in vogue for a variety of applications such as automation [2], underwater lift-gate control [3], force measurement in robots [4], absolute position sensing [5], and position control in mechatronic systems [6]....
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...Schemes such as oscillators for rotary potentiometers [9]–[11], resonant oscillator bridges [5], and phase measurement [12] have been proposed for inductive sensors but they are not suitable for an IVD with a floating wiper....
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