On the torque generated in a servo valve torque motor using permanent magnets

Urata, Eizo

doi:10.1243/0954406jmes584

Cited by 26 publications

(22 citation statements)

References 10 publications

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“…These directly affect the output performance of servo valves [1][2][3][4][5]. Some research has been conducted on the dynamics and control of hydraulic torque motors.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Field and Torque Output of Packaged Hydraulic Torque Motor

et al. 2018

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Hydraulic torque motors are one key component in electro-hydraulic servo valves that convert the electrical signal into mechanical motions. The systematic characteristics analysis of the hydraulic torque motor has not been found in the previous research, including the distribution of the electromagnetic field and torque output, and particularly the relationship between them. In addition, conventional studies of hydraulic torque motors generally assume an evenly distributed magnetic flux field and ignore the influence of special mechanical geometry in the air gaps, which may compromise the accuracy of analyzing the result and the high-precision motion control performance. Therefore, the objective of this study is to conduct a detailed analysis of the distribution of the magnetic field and torque output; the influence of limiting holes in the air gaps is considered to improve the accuracy of both numerical computation and analytical modeling. The structure and working principle of the torque motor are presented first. The magnetic field distribution in the air gaps and the magnetic saturation in the iron blocks are analyzed by using a numerical approach. Subsequently, the torque generation with respect to the current input and assembly errors is analyzed in detail. This shows that the influence of limiting holes on the magnetic field is consistent with that on torque generation. Following this, a novel modified equivalent magnetic circuit is proposed to formulate the torque output of the hydraulic torque motor analytically. The comparison among the modified equivalent magnetic circuit, the conventional modeling approach and the numerical computation is conducted, and it is found that the proposed method helps to improve the modeling accuracy by taking into account the effect of special geometry inside the air gaps.

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“…These directly affect the output performance of servo valves [1][2][3][4][5]. Some research has been conducted on the dynamics and control of hydraulic torque motors.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Field and Torque Output of Packaged Hydraulic Torque Motor

et al. 2018

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“…Urata [10][11][12][13][14] has done much useful and significant research on the effects of unequal air gap, magnetic reluctance and leakage flux of permanent magnets, and magnetic stiffness of torque motors. In recent years, Dasgupta and Murrenhoff 15 gave a comprehensive model of a closed-loop servo valve-controlled hydromotor drive system by using the bondgraph simulation technique.…”

Section: Introductionmentioning

confidence: 99%

A seventh-order model for dynamic response of an electro-hydraulic servo valve

Liu

Jiang

2014

Chinese Journal of Aeronautics

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In this paper, taking two degrees of freedom on the armature-flapper assembly into account, a seventh-order model is deduced and proposed for the dynamic response of a two-stage electro-hydraulic servo valve from nonlinear equations. These deductions are based on fundamental laws of electromagnetism, fluid, and general mechanics. The coefficients of the proposed seventhorder model are derived in terms of servo valve physical parameters and fluid properties explicitly. For validating the results of the proposed model, an AMESim simulation model based on physical laws and the existing low-order models validated by other researchers through experiments are used to compare with the seventh-order model. The results show that the seventh-order model can reflect the physical behavior of the servo valve more explicitly than the existing low-order models and it could provide guidance more easily for a linear control design approach and sensitivity analysis than the AMESim simulation model.

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“…Servo valve torque motors of this type first appeared on the market in the 1950s and have been widely used since then. The structure and function of the servo valve torque motor has been explained in texts [1][2][3][4] and in a recent paper of the present author [5]; hence, they will not be repeated here.…”

Section: Introductionmentioning

confidence: 99%

“…Texts [1][2][3][4] and research papers [5][6][7][8][9][10] explaining servo valves have assumed a symmetric structure of the torque motors for their servo valves, or torque motors having equal air-gaps. To the author's best knowledge, literature relating to the influence of inequality of air-gaps is not available, except for a note by the author [11], or at least is not common.…”

Section: Introductionmentioning

confidence: 99%

Influence of unequal air-gap thickness in servo valve torque motors

Urata

2007

Proceedings of the Institution of Mechanical Engineers, Part C:

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The current paper considers servo valve torque motors having four air-gaps. An ideal for these types of torque motors is to have four equal air-gaps at free state. However, real servo valve torque motors have unequal air-gaps due to production errors. Because the influence of the inequality of air-gaps is not clear, servo valve manufacturers have made great efforts to establish the equality of the air-gaps. The current paper gives a prospect on how an imbalance of air-gaps changes the flux densities in the air-gaps and the resultant torque characteristic. An important result of the paper is that some of the air-gap imbalance induces a torque change of magnitude of second-or higher-powers of the imbalance. The imbalance of the air-gaps due to different pole heights results in an offset proportional to the magnitude of the imbalance. These results can be used for setting a tolerance limit for air-gap thickness.

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On the torque generated in a servo valve torque motor using permanent magnets

Cited by 26 publications

References 10 publications

Magnetic Field and Torque Output of Packaged Hydraulic Torque Motor

Magnetic Field and Torque Output of Packaged Hydraulic Torque Motor

A seventh-order model for dynamic response of an electro-hydraulic servo valve

Influence of unequal air-gap thickness in servo valve torque motors

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