阅读说明：本技术 一种基于Halbach阵列式线圈的涡流探头 (Eddy current probe based on Halbach array coil ) 是由 田中山 仪林 杨昌群 牛道东 梁伽铭 于 2021-09-09 设计创作，主要内容包括：本发明是一种基于Halbach阵列式线圈的涡流探头。所述探头包括：第一线圈、第二线圈、第三线圈、第四线圈和第五线圈；所述第一线圈、第三线圈和第五线圈水平放置；所述第二线圈和第四线圈竖直放置；在第一线圈的一端通入电流,产生磁场；在第二线圈的一端通入电流,产生磁场；在第三线圈的另一端通入电流,产生磁场；在第四线圈的不同端子通入电流,产生磁场；在第五线圈中通入通第一线圈相同的电流,产生磁场；将磁感线密集的一侧作为涡流探头位移测量方向。(The invention relates to an eddy current probe based on a Halbach array coil. The probe includes: a first coil, a second coil, a third coil, a fourth coil and a fifth coil; the first coil, the third coil and the fifth coil are horizontally arranged; the second coil and the fourth coil are vertically arranged; one end of the first coil is connected with current to generate a magnetic field; one end of the second coil is connected with current to generate a magnetic field; the other end of the third coil is connected with current to generate a magnetic field; current is introduced into different terminals of the fourth coil to generate a magnetic field; the current which is the same as that of the first coil is led into the fifth coil to generate a magnetic field; and taking the side with the dense magnetic induction lines as the displacement measurement direction of the eddy current probe.)

1. An eddy current probe based on a Halbach array coil is characterized in that: the probe includes: a first coil, a second coil, a third coil, a fourth coil and a fifth coil;

the first coil, the third coil and the fifth coil are horizontally arranged; the second coil and the fourth coil are vertically arranged; one end of the first coil is connected with current to generate a magnetic field; one end of the second coil is connected with current to generate a magnetic field; the other end of the third coil is connected with current to generate a magnetic field; current is introduced into different terminals of the fourth coil to generate a magnetic field; the current which is the same as that of the first coil is led into the fifth coil to generate a magnetic field;

and taking the side with the dense magnetic induction lines as the displacement measurement direction of the eddy current probe.

2. The Halbach array coil based eddy current probe according to claim 1, wherein: and the winding directions of the first coil, the second coil, the third coil, the fourth coil and the fifth coil are the same.

3. The Halbach array coil based eddy current probe according to claim 2, wherein: the displacement of the detected conductor is related to the equivalent impedance of the detection coil, the equivalent impedance Z of the detection coil is related to the geometric parameters of the coil, the frequency f of the excitation signal and the displacement x of the detected conductor, and is related to the electrical conductivity sigma and the magnetic permeability mu of the detected conductor, and the equivalent impedance of the detection coil is expressed by the following formula:

Z＝f(R_b,R_a,h,N,f,x,σ,μ)

wherein R is_bIs the outer radius of the coil; r_aIs the inner radius of the coil; h is the thickness of the coil; n is the number of turns of the coil.

Technical Field

The invention relates to the technical field of eddy current sensors, in particular to an eddy current probe based on a Halbach array type coil.

Background

The eddy current sensor can realize high-precision measurement of internal defects and micro-displacement of a measured object based on the principle of eddy current mutual inductance effect of the eddy current sensor and a conductive medium, and is characterized by good long-term working reliability, high sensitivity, strong anti-interference capability, non-contact measurement, high response speed and no influence of media such as oil, water and the like. Therefore, the method is widely applied to the fields of nondestructive testing, high-precision measurement and the like of metal equipment.

However, the current eddy current sensor is limited by technical bottlenecks such as coil structure and parameter optimization, and has the defects of poor sensitivity, insufficient linearity, urgent need for improvement of detection accuracy under abrupt temperature field, and the like, so that the application of the current eddy current sensor in the high-accuracy detection field in the extreme environment is limited. Therefore, the improvement of the sensitivity and the detection accuracy of the eddy current sensor becomes the key for solving the problems.

The coil is used as a core component of the eddy current sensor, is mainly used for generating a magnetic field for exciting eddy current in a measured medium, and converts a detected physical quantity into an impedance electric signal through magnetic field energy coupling with the measured medium. The structural form and the impedance parameter essence determine the spatial distribution characteristic of the detection magnetic field, and directly influence the sensitivity and the detection precision of the eddy current sensor.

At present, common coil structures are mainly divided into typical planar single coils, spatial multi-coils, orthogonal rectangular cylinder coils and unconventional flexible coils. Because the distribution characteristics of the spatial magnetic field of each type of coil are obviously different, the application fields of the coils are also obviously different. The magnetic field intensity generated by the coil is not large enough in the ubiquitous situation, and the reason is that the magnetic induction lines cannot be well concentrated, so that the sensitivity and the detection precision of the eddy current sensor are directly influenced.

Disclosure of Invention

Aiming at the defects of the existing coil structure, the invention provides an eddy current probe based on a Halbach array type coil, and the invention provides the following technical scheme:

an eddy current probe based on a Halbach array coil, the probe comprising: a first coil, a second coil, a third coil, a fourth coil and a fifth coil;

the first coil, the third coil and the fifth coil are horizontally arranged; the second coil and the fourth coil are vertically arranged; one end of the first coil is connected with current to generate a magnetic field; one end of the second coil is connected with current to generate a magnetic field; the other end of the third coil is connected with current to generate a magnetic field; current is introduced into different terminals of the fourth coil to generate a magnetic field; the current which is the same as that of the first coil is led into the fifth coil to generate a magnetic field;

and taking the side with the dense magnetic induction lines as the displacement measurement direction of the eddy current probe.

Preferably, the first coil, the second coil, the third coil, the fourth coil and the fifth coil are wound in the same direction.

Preferably, the displacement of the conductor under test is related to the equivalent impedance of the detection coil, the equivalent impedance Z of the detection coil is related to the geometric parameters of the coil, the frequency f of the excitation signal and the displacement x of the conductor under test, and is related to the electrical conductivity σ and the magnetic permeability μ of the conductor under test, and the equivalent impedance of the detection coil is expressed by the following formula:

Z＝f(R_b,R_a,h,N,f,x,σ,μ)

wherein R is_bIs the outer radius of the coil; r_aIs the inner radius of the coil; h is the thickness of the coil; n is the number of turns of the coil.

The invention has the following beneficial effects:

the invention discloses an eddy current probe design based on a Halbach array type coil. On the basis of a parallel cylindrical single coil, coil arrangement in a Halbach array form is innovatively adopted, permanent magnets in different magnetizing directions are arranged according to a certain rule, magnetic lines of force can be converged on one side of the magnet, and the magnetic lines of force are weakened on the other side of the magnet, so that an ideal unilateral magnetic field is obtained, the magnetic field on one side of the unilateral magnetic field is obviously enhanced, a stronger eddy current effect can be induced, and the measurement accuracy and resolution of micro displacement are improved.

Drawings

FIG. 1 is a diagram of array coil placement;

FIG. 2 is a simulation diagram of the magnetic field of a Halbach array coil.

Detailed Description

The present invention will be described in detail with reference to specific examples.

The first embodiment is as follows:

referring to fig. 1 to 2, the present invention provides an eddy current probe based on a Halbach array coil, and the present invention provides an eddy current probe based on a Halbach array coil. Aiming at the defects of the existing coil structure, the invention discloses an eddy current probe design based on a Halbach array type coil, which is oriented to the field of high-precision measurement of micro-displacement. On the basis of a parallel cylindrical single coil, coil arrangement in a Halbach array form is innovatively adopted, permanent magnets in different magnetizing directions are arranged according to a certain rule, magnetic lines of force can be converged on one side of the magnet, and the magnetic lines of force are weakened on the other side of the magnet, so that an ideal unilateral magnetic field is obtained, the magnetic field on one side of the unilateral magnetic field is obviously enhanced, a stronger eddy current effect can be induced, and the measurement accuracy and resolution of micro displacement are improved.

The technical scheme adopted by the invention is an eddy current probe design based on Halbach array type coils, and is characterized in that the coils are arranged according to the desired unilateral magnetic field direction (namely the displacement measurement direction of an eddy current sensor), as shown in figure 1. The 5 coils with the same winding direction are arranged as a figure, the first coil 1, the third coil 3 and the fifth coil 5 are horizontally arranged, the second coil 2 and the fourth coil 4 are vertically arranged and respectively connected with currents at different terminals (the first coil 1 and the third coil 3 are connected with currents at different terminals, the second coil 2 and the fourth coil 4 are connected with currents at different terminals, and the first coil 1 and the fifth coil 5 are connected with currents at the same terminals), and a magnetic field with the direction as the figure is generated according to the Faraday's electromagnetic induction theorem.

The coil placement mode generates a strong magnetic field below the attached drawing (in the displacement measurement direction), and the simulation result is shown in fig. 2. The magnetic field on one side of the arrangement is obviously enhanced and can be used as the measuring end of the eddy current probe. The magnetic field intensity enhanced by the coil design can generate enhanced eddy current induction in the tested conductor, so that the measurement accuracy and the resolution of the eddy current sensor are improved.

The Halbach array type coil is designed to be used for enhancing the eddy current probe of the magnetic field intensity in the displacement measurement direction, the coil can generate a magnetic field by introducing current into the coil, the direction of the magnetic field corresponds to the polarization direction of the Halbach array magnet, and the coil is correspondingly arranged to achieve the effect of the Halbach array. Through this coil design structure, can make displacement measurement direction magnetic field intensity reinforcing to minimum coil quantity makes magnetic field intensity maximize, and the opposite side magnetic field is less, can reduce this side and carry out the influence that the micro displacement measurement produced.

Through adopting above-mentioned structural design, strengthened the magnetic field intensity of displacement measurement direction greatly, at the measurement process, stronger eddy current effect can be induced at surveyed conductor inside in the magnetic field, has improved eddy current sensor's measurement accuracy and resolution greatly.

As shown in fig. 2, the side with dense magnetic induction lines is used as the displacement measurement direction of the eddy current probe. When the eddy current probe is fixed and the measured conductor moves close to or away from the probe, an eddy current effect can be generated in the measured conductor. The strength of the eddy current effect is related to the magnetic field strength there. When the probe is close to the probe, the magnetic field intensity is increased, and the eddy current effect is enhanced; when the probe is far away from the probe, the magnetic field intensity is small, and the eddy current effect is weakened. Because the current vortex is alternating current, the current vortex can generate an induced magnetic field, and the direction of the induced magnetic field is opposite to the direction of the original magnetic field according to Lenz's law, thereby attempting to weaken the original magnetic field of the coil. The size of the induced magnetic field is influenced by the size of the eddy current, and the displacement of the metal object to be detected and the internal defects influence the size of the eddy current, so that the size of the induced magnetic field is influenced, and finally, the impedance of the coil is changed.

According to the eddy current principle, the displacement of the conductor under test is related to the equivalent impedance of the detection coil, and the equivalent impedance Z of the detection coil is related to the geometric parameters of the coil, the frequency f of the excitation signal and the displacement x of the conductor under test, and also to the electrical conductivity σ and the magnetic permeability μ of the conductor under test, so the equivalent impedance of the detection coil can be written as:

Z＝f(R_b,R_a,h,N,f,x,σ,μ)

in the formula: r_bIs the outer radius of the coil; r_aIs the inner radius of the coil; h is the thickness of the coil; n is the number of turns of the coil.

According to the above formula, if the geometric parameters of the coil and the frequency of the excitation signal are fixed, and the electrical conductivity and magnetic permeability of the measured conductor are also kept unchanged, the equivalent impedance of the coil is only related to the displacement of the measured conductor. And fixing all parameters except the measured conductor displacement by using a control variable method, and designing a signal conditioning system of the sensor by using the relation that the measured conductor displacement and the equivalent impedance of the coil are single-valued functions to finish the design of the eddy current displacement sensor.

The above is only a preferred embodiment of the eddy current probe based on the Halbach array coil, and the protection range of the eddy current probe based on the Halbach array coil is not limited to the above embodiments, and all technical schemes belonging to the idea belong to the protection range of the invention. It should be noted that modifications and variations which do not depart from the gist of the invention will be those skilled in the art to which the invention pertains and which are intended to be within the scope of the invention.