Multivariate statistical process monitoring has been widely used in industry However, traditional algorithms often ignore the dynamic characteristics of actual industry process This study proposes a novel algorithm called multistep dynamic slow feature analysis (MS-DSFA), which has completed the full-condition monitoring of a dynamic system and divided dynamic structures more precisely This algorithm achieves an optimal detection rate according to multiple control limits To enrich the experiments, we select a numerical example, Tennessee Eastman process, and XJTU-SY bearing data sets to verify the universality of the algorithm According to the overall score for optimal detection rates and false alarm rates, MS-DSFA stands out in the comparison of existing algorithms

Multistep Dynamic Slow Feature Analysis for Industrial Process Monitoring

A new, non-contact, planar spiral coil-based inductive displacement sensor is presented in this paper. The proposed sensor employs a fixed planar coil and a movable $U$ -shaped magnetic core. The sensor is designed such a way that the shape of inductance versus displacement $x$ is sinusoidal. Due to this feature, the value of $x$ is obtained easily from the inductance measured without the need of a look-up table, which is not the case for most of the planar coil-based sensors. The proposed sensor has very low sensitivity to vertical misalignment of the core. A phase-sensitive detector-based measurement scheme is employed to measure the inductance. The inductance characteristic of the proposed sensor is symmetric with respect to the center of the coil. A simple capacitive detection scheme to distinguish the position of the core between the two halves of the coil is proposed in this paper. This method enables to extend the sensor range with multiple coils connected in series. A prototype of the proposed sensor has been developed and tested. The sensor has a worst case error of 0.6%. A modified sensor using two coil sets has been developed. The modified sensor has high sensitivity over its entire range, unlike the first prototype. It has a worst case error of 0.2% and a resolution of 6.5 $\mu \text{m}$ . The low-cost sensor developed will be useful for many industrial linear position sensing applications.

Design and Development of a New Non-Contact Inductive Displacement Sensor

Wireless, passive, and cost-efficient monitoring of moisture within packaged food and medicine is important to ensure their safety and freshness. This paper presents paper-based single spiral inductance–capacitance (LC) sensors and a distance-insensitive readout system. The parasitic capacitance of the single-spiral coil is used to form an LC resonant circuit with its inductance. The printing paper is utilized as a humidity sensing material. A model for the LC sensor is analyzed and compared with HFSS simulation, showing the relative error within 6.3%. Nano-silver paste for the single-spiral coil was screen printed on the printing paper. The LC sensors with 4, 6, and 8-turns coils were characterized at relative humidity levels of 15%-90%RH by a readout coil at a fixed position. Comparison shows that the 8-turn sensor has the best linearity with respect to humidity. The sensitivity and response time were measured to be 120 kHz/%RH and 60 minutes, respectively, with the hysteresis errors less than 0.9%. During the practical monitoring, the tested signal frequency will have a shift if the coil’s relative position alters. To weaken the influence of the coil’s position, a readout coil, working at the quasi-resonant with the LC sensor was utilized to enhance the readout, resulting in more stable signal. According to the experimental results, the improved readout system can restrain the frequency shift within 1.1% at a readout distance from 2–50 mm when the ambient humidity is 60%RH.

Low Cost Paper-Based LC Wireless Humidity Sensors and Distance-Insensitive Readout System

Wireless power transfer (WPT) is an enabling technology for electric vehicles (EV), as it eliminates driver intervention during charging. Major challenges to the adoption of WPT systems include coil misalignment and large air-gap WPT, both of which degrade the transfer efficiency. To address these issues, this article presents a compact WPT charger for the rear of an EV, capable of correcting lateral misalignment $\Delta$ x using two integrated electromagnetic coils. The air-gap $\Delta$ y is reduced due to the rear placement of the charging pads. The variation in $\Delta$ y , however, increases due to vehicle parking accuracy, which impacts the operation of the electromagnetic coils. This article proposes a closed-loop three-stage position-correcting control algorithm capable of detecting the impedance and resonant frequency of the system, which, in conjunction with the electromagnetic coils, results in improved vehicle alignment. The experimental prototype achieves a peak dc–dc efficiency of 90.1% at 5 kW WPT. With $\Delta$ y  = 50 mm, the electromagnetic coils laterally align the pads within 1.75 s and correct $\Delta$ x as large as 240 mm. The position-correcting control was successfully demonstrated in four parking scenarios with the charging pads being corrected to within a 10-mm radius of perfect alignment.

Wireless Electric Vehicle Charger With Electromagnetic Coil-Based Position Correction Using Impedance and Resonant Frequency Detection

For efficient power transfer in an inductive power transfer system, the primary coil, placed inside the charging pad, and the secondary coil, kept inside the vehicle pad, must be aligned correctly. Information about the real-time position of the electric vehicle (EV) with respect to the charging pad is required to aid the driver in the alignment of the two coils. This paper proposes a wireless LC -based scheme using three small sensing coils kept close to the primary coil, to detect the position of the EV. Each sensing coil has a capacitor connected to it, forming three LC tank circuits. The measurement circuit, which is connected to the secondary coil, measures the coupling coefficient between the secondary coil and each of the LC coils. Based on these values, the direction in which the EV should be driven to align the two coils is determined. This information is displayed to the driver. A prototype of the proposed scheme is designed and tested. Using the proposed scheme, the primary and the secondary coils are aligned correctly. This is verified by exciting the primary coil of the prototype by a power source at 50 kHz and measuring the induced voltage in the secondary coil, which is found to be the maximum when the two coils are aligned using the proposed scheme.

Sensor System to Aid the Vehicle Alignment for Inductive EV Chargers

A new readout scheme for multiple passive $LC$ sensors based on the impulse response is presented here. A precharged capacitor is discharged through a readout coil which is magnetically coupled to multiple sensor coils. Fast Fourier transform of the resultant oscillatory current through the readout coil is taken, from which the equivalent impedance of the system at different frequencies is computed. The maximum value of the imaginary parts of this impedance occurs at the resonant frequencies of the sensor coils that are coupled. The conventional measurement schemes rely on a frequency sweep approach to determine the resonance frequencies of the sensor coils; that process is inherently time-consuming. A simple, low-cost readout scheme with a fast update rate is proposed. A method to measure the quality factor $Q$ of the sensor coil system is also presented here. Output of the proposed scheme is independent of the variation in the coupling factor $k$ . The measurement resolution of the proposed scheme has been improved using a Gaussian curve fitting approach, which also reduces the effect of noise in the final output. A prototype of the proposed system has been built with a readout coil and three sensors coupled to it and tested. The worst case error observed in the test was less than 0.5%, when the prototype system was tested with a variable capacitor (47 to 345 pF) in the sensor coil. The proposed readout scheme is useful in applications requiring simultaneous wireless monitoring of multiple physical parameters.

An Efficient Readout Scheme for Simultaneous Measurement From Multiple Wireless Passive $LC$ Sensors

This paper presents a simple and efficient interfacing scheme for passive LC sensors, connected to the measurement unit through a magnetically coupled readout and sensor coils. The proposed scheme always measures at or near the parallel resonant frequency $f_{p}$ of the system. The scheme first converts the capacitance of the sensor into a phase angle ( $\phi $ ) between the excitation voltage ( $V_{\textrm {in}}$ ) and the current $I_{1}$ through the readout coil. The final output is given by tan( $\phi $ ), but easily realized using a phase sensitive detector (PSD). The inputs to the PSD are $V_{\textrm {in}}$ and a signal proportional to the $I_{1}$ . This new approach gives the following advantages: 1) it realizes a simple, hardware optimized measurement system, which draws the minimum current from $V_{\textrm {in}}$ as the measurement is at $f_{p}$ ; 2) the time taken for the measurement is much less, compared with the frequency sweep approach; 3) the output is linear; and 4) the output is insensitive to the variations in the coupling coefficient ( $k$ ), for a wide range of $k$ . In addition, a new, but simple method is employed to calibrate the system from the readout coil side. This enables the output to be less sensitive to the variation in the quality factor, coupling coefficient, and resistance of the coil. A prototype of the proposed readout system has been developed and tested for a range of ±5 pF. The output of the interfacing scheme showed a high sensitivity of 5.5°/pF. The worst case linearity noted was 0.52% and the worst case error observed in the test was less than 0.67%.

A Linear and High Sensitive Interfacing Scheme for Wireless Passive LC Sensors

A new, non-contact, planar spiral coil based inductive displacement sensor is presented in this paper. The proposed sensor has a fixed planar coil and a movable U-shaped magnetic core. The coil is designed such that the inductance vs. displacement of the sensor has a predictable characteristic that can be easily represented. The sensor presented has a sinusoidal characteristic, which helps to retrieve the displacement information from the inductance value easily, without the need of a look-up table, which is not the case for most of the sensors that use planar coils. The inductance characteristic for the proposed is symmetric with respect to the center of the coil. A simple method to distinguish the position of the core between the two halves of the coil is proposed in the paper. This not only solves the symmetry problem, but also enables to extend the sensor range with multiple coils connected in series. A Phase-Sensitive Detector (PSD) based measurement is employed to measure the inductance. This approach provides two advantages; (a) very low sensitivity to external interferences and (b) the sensitivity (of output vs. displacement) remain constant even if multiple number of coils are connected in series to increase the range of the sensor. A finite element analysis has been conducted to design the coil and to analyze the effect of vertical movement of the core. A prototype of the proposed sensor and measurement scheme has been developed and tested. The results are presented in the paper. The low-cost sensor presented will be useful for many industrial linear position sensing applications.

Anish Babu

Papers

Design and Development of a New Non-Contact Inductive Displacement Sensor

Sensor System to Aid the Vehicle Alignment for Inductive EV Chargers

An Efficient Readout Scheme for Simultaneous Measurement From Multiple Wireless Passive $LC$ Sensors

A Linear and High Sensitive Interfacing Scheme for Wireless Passive LC Sensors

A wide range planar coil based displacement sensor with high sensitivity