A Noncontact Angle Sensor Based on Eddy Current Technique
01 Apr 2020-IEEE Transactions on Instrumentation and Measurement (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 69, Iss: 4, pp 1275-1283
TL;DR: This paper presents the design and development of a novel, linear, eddy current-based noncontact angle sensor with 360° range that has no electrical contact to the rotary part and its output is immune to moisture, dust, and oil.
Abstract: This paper presents the design and development of a novel, linear, eddy current-based noncontact angle sensor with 360° range. Although the eddy current proximity sensors are known for high reliability, resolution, and insensitivity to moisture and oil, the approach has not been exploited to develop full-circle range angle sensors with such features. The proposed sensor consists of a rotary conducive hollow tube (e.g., made of aluminum) part and a stationary part with four identical flexible coils. The tube has a simple but special groove. The position of the groove modifies the value of the inductance of the stationary coil as a function of the sensing angle. The design is such that the inductance of each coil varies linearly for a specified range of the angle. From this piecewise linear characteristic, an output that is linear for the full-circle range is obtained using a simple yet effective algorithm. A suitable signal conditioning circuit is developed to obtain an output that is proportional to the change in the inductance of the coil. In order to optimize the design, first, the sensor structure was studied using finite-element analysis. Then, a prototype of the sensor was built and tested in the laboratory. The prototype sensor has a resolution of 0.08° and a maximum nonlinearity of 0.25%. The possible sources of error of the sensor have been analyzed and quantified. The sensor has no electrical contact to the rotary part and its output is immune to moisture, dust, and oil.
Citations
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TL;DR: A critical review of advancements made in the area of non-contact angle sensing in the last two decades shows significant progress that has been achieved in the performance aspects of angle sensors, overcoming the challenges introduced by new and specific applications.
Abstract: This paper presents a critical review of advancements made in the area of non-contact angle sensing in the last two decades. Angular position sensing is an essential function in most of the engineering systems associated with industries such as automotive, robotics, process, and aircraft. The review shows significant progress that has been achieved in the performance aspects of angle sensors, overcoming the challenges introduced by new and specific applications. Progress is also visible in effectively utilizing the emerging allied technologies on the sensing and electronics field for the development of high-end angle sensors. As a part of the review, the important sensing techniques utilized for the angle sensors are identified and carefully looked at the advantages and limitations of those. Besides, the potential areas for improvements are also suggested. The important techniques employed to design and develop the angle sensors are based on capacitive, inductive, magneto-resistive, and optical schemes. Signal conditioning circuits, analog or digital, or a combination of it, are necessary to derive the best from the sensing elements. They play a vital role in the overall performance of the sensor. The review addresses the advancement in the sensing element, methodology, and signal conditioning aspect in detail. In this review, the important angle sensors reported are evaluated against the performance parameters such as range, resolution, linearity, accuracy, sensitivity, power consumption, complexity, cost, manufacturability, and reliability.
45 citations
Cites background or methods from "A Noncontact Angle Sensor Based on ..."
...The existing electronic interface for eddy current angle sensors measures the impedance of the sensing coils as it changes as a function of angular displacement [48]....
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...In order to measure the inductance independent of coil resistance, circuits described in [48] and [126] are well suited....
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...The resolution of the eddy current sensors is a function of the skin depth of the target material [48]....
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...These could be used for sensors where the change in self-inductance is used to sense the angle information [48], [49], [52], [53]....
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...The circuit incorporated a phase-sensitive detector (PSD), which has outputs corresponding to the in-phase and quadrature components of coil voltages, and quadrature output will be proportional to the inductive reactance Xeq [48]....
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TL;DR: Results show that the root mean square angular error of a single axis within a range of ±14° is approximately 20 min, which suggests the feasibility of the proposed method.
Abstract: Precision spherical joint is a spherical motion pair that can realize rotation with three degrees of freedom. This joint is widely used in robots, parallel mechanisms, and high-end medical equipment, as well as in aerospace and other fields. However, the rotation orientation and angle cannot be determined when the joint is in passive motion. The real-time determination of the rotation orientation and angle is crucial to the improvement of the motion control accuracy of the equipment where the joint is installed in. In this study, a new measurement method that utilizes eddy current sensors is proposed to identify the special features of the joint ball and realize angle measurements indirectly. The basic idea is to manufacture the specific shape features on the ball without affecting its movement accuracy and mechanical performance. An eddy current sensor array is distributed in the ball socket. When the ball head rotates, the features on the ball opposite to the sensor, as well as the output signal of every eddy current sensor, change. The measurement model that establishes the relationship between the output signal of the eddy current sensor array and the rotation direction and angle of the ball head is constructed by learning and training an artificial neural network. A prototype is developed using the proposed scheme, and the model simulation and feasibility experiment are subsequently performed. Results show that the root mean square angular error of a single axis within a range of ±14° is approximately 20 min, which suggests the feasibility of the proposed method.
9 citations
Additional excerpts
...It also can be used to detect angle [22,23] and thickness [24]....
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TL;DR: A novel position sensor for pneumatic and hydraulic cylinder applications is presented in this article, and the conical solid iron core conical in shape surrounded by axisymmetric coils is an essential part of the proposed position sensor.
Abstract: A novel position sensor for pneumatic and hydraulic cylinder applications is presented in this article. The solid iron core conical in shape surrounded by axisymmetric coils is an essential part of the proposed position sensor. The axisymmetric coils are used for excitation and voltage measurements. The conical solid iron core is annealed to homogenize the magnetic properties and to increase the permeability of the conical solid iron core. This improves the performance of the position sensor in terms of sensitivity and linearity. Analytical and finite-element analyses are utilized along with measurements in order to analyze the performance of the position sensor. The position sensor performs measurements of excitation coil inductance and pickup coil voltages. Various frequencies are considered for the analysis and for the measurements. The measurement results show that the maximum linearity error is about 4% for the manufactured sensor and is calculated to have a maximum value of 1% for the theoretical model. The achievable resolution of the proposed sensor is about 0.4 mm.
6 citations
Cites background from "A Noncontact Angle Sensor Based on ..."
...CONTACTLESS linear and angular position detection of target objects is always a challenging issue [1]–[3]....
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TL;DR: Zhang et al. as mentioned in this paper proposed a measurement method for the rotation angle of the spherical joint based on the extreme learning machine (ELM) artificial neural network and four eddy current sensors.
Abstract: This paper proposes a measurement method for the rotation angle of the spherical joint based on the extreme learning machine (ELM) artificial neural network and four eddy current sensors. Aiming at the problems of small range and low accuracy in the early three-eddy-current angle measurement prototype, the position matching scheme of four eddy current sensors is researched, a new prototype is developed through simulation analysis, and ELM neural network substitutes the previous generalized regression neural network (GRNN) for building a new measurement model. The modelling training and comparison test are completed in the self-developed high-precision angle calibration device. Experimental results show that the new prototype not only covers a ±20° measurement range but also promotes measurement accuracy, and the standard deviation of the single-axis measurement drops to $3^{\prime }$ within the range of 5°–15°. It provides a relatively high-precision measurement method for real-time, multi-axis active detection of spherical joint space rotation angle error.
6 citations
TL;DR: In this paper, a non-contact vertical inductive torque sensor was built and investigated, and the effect of different rotors on the nonlinear characteristics of the sensor was analyzed based on the simulation results.
6 citations
References
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01 Jul 2012
TL;DR: In this paper, a simple differential eddy current sensor for measuring small rotation angle is presented and experimentally investigated, where the output signal is obtained from changing active areas of a rotatable copper plate with two legs inserted into gaps of a magnetic circuit.
Abstract: A simple differential eddy current sensor for measuring small rotation angle is presented and experimentally investigated. The output signal is obtained from changing active areas of a rotatable copper plate with two legs inserted into gaps of a magnetic circuit. Test results show this kind of sensor has a resolution of 8µrad over the effective measurement range of ±7000µrad.
2 citations
"A Noncontact Angle Sensor Based on ..." refers background in this paper
...A differential eddy current angle sensor has been developed, and the details are given in [26], but the range is very small....
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TL;DR: In this paper, the authors developed a code for efficient resolution of an electromagnetic problem modeling, especially, for the analysis of probe response due to the eddy current process, and the validation of developed code was made.
Abstract: The eddy current testing can be used such as a perfect tool to characterize defects in conducting materials. However, in the latest years, an important progress was made in the development of software for the eddy current testing simulations. Evaluation of the NDT modeling tools is the principal goal of this study. Main concerns of the aeronautic industry and the potential contribution of modeling are discussed and illustrated. Simulation by finite element method is realized with the aim to calculate the electromagnetic energy of interaction between coil and tested part that enables to deduce the impedance response. The objective of this work is the development of a code for efficient resolution of an electromagnetic problem modeling, especially, for the analysis of probe response due to the eddy current process. The validation of developed code was made. The obtained results converge quickly towards the solution given by the (FEMM) code with an average error of 0.018 for real parts of impedance and 0.004 for imaginary parts. The presented results in this work serve to illustrate that the proposed method is practical and they are also of some intrinsic interest especially in the control of aluminum tubes used in aeronautics.
2 citations
"A Noncontact Angle Sensor Based on ..." refers background in this paper
...To study a system with a homogeneous conductor placed in the time-varying external magnetic field, Maxwell’s equation listed in the following can be used [29], [30]: ∇ × H = σ E + ∂ ∂ t εE (5)...
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