Double-magnetic-circuit two-end symmetric excitation cylindrical closed magnetic field type low frequency vibration calibration table with eddy current compensation

Abstract

The invention provides a double-magnetic-circuit two-end symmetric excitation cylindrical closed magnetic field type low frequency vibration calibration table with eddy current compensation, belonging to the field of vibration measurement technology. A cylindrical closed type magnetic field structure design is provided. Two cylindrical permanent magnets are symmetrically installed at two ends of a center magnet yoke and face magnetic poles. Two symmetric closed magnetic circuits are formed by magnet yokes. The magnetic induction intensity distribution with high uniformity is generated in air gaps. After a working coil is energized, the working coil is affected by Lorentz force in a magnetic field, and precisely controllable electromagnetic drive force is generated. The surfaces of the magnet yokes adjacent to the air gaps are provided with an array type micro structure in the form of deep trenches, and the eddy current loss can be effectively inhibited. The organic integration design of air lubricated guide technology is employed, and outstanding electromagnetic drive mechanical performance and high movement guide precision are obtained at the same time. According to the double-magnetic-circuit two-end symmetric excitation cylindrical closed magnetic field type low frequency vibration calibration table, large stroke, high thrust, a linear electromagnetic driving force characteristic and high movement guide precision can be considered, and a high precision and large stroke high performance low frequency vibration calibration table technical scheme is provided for low-frequency / ultra-low frequency vibration calibration.

Description

technical field [0001] The invention belongs to the field of vibration calibration devices, and mainly relates to a cylindrical closed magnetic field type low-frequency vibration calibration table with symmetrical excitation at both ends of a double magnetic circuit for eddy current compensation. Background technique [0002] In the field of vibration measurement technology, the vibration calibration table that generates standard vibration signals is the core equipment to achieve high-precision vibration calibration, and it is also an important equipment that constitutes the national vibration measurement technology system. The high-precision vibration calibration table generally adopts the form of electromagnetic vibration table. In recent years, aerospace, building bridges, earthquake prevention and disaster reduction and other fields have raised the need for low-frequency / ultra-low-frequency vibration calibration. In order to improve the signal-to-noise ratio of the stan...

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Problems solved by technology

[0005] The disadvantages of the above two technical solutions are: 1) the cylindrical outer yoke needs to be processed in the long inner dimension, which is difficult to process and difficult to guarantee the accuracy; 2) when the cylindrical permanent magnet is used, the through hole needs to be processed on the permanent magnet And it is fixed on the yoke by non-magnetic bolts, the assembly is complicated and will affect the magnetic circuit; when a cylindrical permanent magnet is used, it is difficult to sinter, process, magnetize and assemble a large-sized cylindrical permanent magnet; 3) The cylindrical outer yoke needs to be set on the central yoke. If the permanent magnet is magnetized first and then assembled, the assembly is very difficult and the assembly accuracy is difficult to guarantee; if the permanent magnet made of AlNiCo material is used, it can be assembled first and then assembled. Magnetization method, but due to the low coercivity of AlNiCo material permanent magnets, the performance is not good, which seriously restricts the mechanical properties and indicators

[0007] The shortcomings of this technical solution are: 1) The electromagnetic drive structure is composed of multiple structural combinations and splicing, and the structure is complex; the small permanent magnet needs to be installed on the wedge-shaped pole piece by glue or other methods, which is complicated to assemble and difficult to ensure. Accuracy; 2) The static magnetic induction intensity at a certain position in the air gap is directly related to the working point of the permanent magnet at that place, and the uniformity of the magnetic field in the entire air gap is difficult to guarantee, and the requirements for the consistency of the materials and processes of the small permanent magnets are relatively high. High; 3) The permanent magnet directly faces the air gap, and the additional magnetic field generated after the working coil is energized will have a forced magnetization or demagnetization effect on it. When a large current is passed through the working coil, it is easy to cause irreversible demagnetization of the permanent magnet ;4) When the working coil is energized, the magnetic flux on one side of the coil increases and the magnetic flux on the other side decreases. Since the permanent magnet directly faces the air gap, the magnetic circuit on the side where the magnetic flux increases is easy to saturate. The increased magnetic flux is less than the decreased magnetic flux on the other side, resulting in a decrease in the average magnetic induction at the location of the coil, which in turn distorts the waveform of the generated standard vibration signal

[0009] (1) It is difficult to ensure the uniformity of the magnetic induction intensity distribution of the main magnetic circuit in the long air gap

Before the coil is energized, the permanent magnet is excited to form a stable distribution of the magnetic induction intensity of the main magnetic circuit. As the stroke of the vibration calibration table increases, it is difficult to ensure the uniformity of the magnetic field in the long air gap, which directly affects the linearity of the output electromagnetic driving force after the coil is energized. Some researchers try to compensate by adjusting the current waveform, but the effect is difficult to guarantee, especially for the compensation of high-order magnetic field non-uniformity errors. At present, no effective and highly practical compensation method has been proposed at home and abroad.

[0010] (2) The armature reaction after the working coil is energized restricts the linearity of the output electromagnetic driving force and the distortion of the output vibration waveform index

[0011] (3) It is difficult to process and assemble long yokes and large-size permanent magnets, and the accuracy is difficult to guarantee

[0013] In summary, restricted by the above problems, it is difficult to make further breakthroughs in the waveform distortion and other indicators of the standard low-frequency vibration generated by the existing technical solutions, and it is difficult to meet the high-precision calibration of low-frequency / ultra-low-frequency vibration, especially the next generation with very low frequency and The Need for Vibration Calibration of Ultra-Precise Features

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