Theoretical investigations on the linear and nonlinear damping force for an eddy current damper combining with rack and gear

Abstract

To study the damping characteristics of a new type of eddy current damper with rack and gear recently proposed by the authors, the damping torque for the eddy current damper with rack and gear was theoretically investigated based on some fundamental assumptions, including evenly distributed magnetic field on a conductor plate and no magnetic leakage. A linear relationship between damping torque and velocity was obtained. Numerical simulations by using COMSOL Multiphysics were conducted to evaluate the accuracy of the linear theoretical formula. When angular velocity is less than 30 rad/s, it seems that the linear theoretical results agree well with the numerical results, and maximum relative error between them is about 6.58%. Then, by using COMSOL Multiphysics, a series of parametric studies on damping torque, including the effects of the air gap, the thickness of a back iron plate, the location and number of permanent magnets, and the thickness of a conductor plate, were carried out to further examine the linear theoretical formula. The results show the effects of the air gap and back iron plate on the relative error between linear theoretical and numerical results can be ignored, whereas the location and number of permanent magnets and the thickness of the conductor plate have significant influences on the relative error. Finally, a nonlinear theoretical formula was obtained by introducing three modified coefficients into the linear theoretical formula, and its accuracy was verified in some typical cases. It is proved that there is sufficient accuracy to adopt the nonlinear theoretical formula in preliminary design of the eddy current damper with rack and gear to determine the main structural parameters.

A novel 500 kN axial eddy current damper using rack and gear mechanism: Design, testing, and evaluation

“…Among them, the PMs are fixed on the stators, and the stators are fixed on the gear box. Note that the PMs are arranged along the radial direction of the conductors, which is different from recent studies of the authors 34,35 . This arrangement is beneficial to reduce the deformation of the rotors and improve the manufacturing accuracy of dampers.…”

“…The rack and gear mechanism, a mature industrial product with low cost and strong reliability, can be used to replace the ball screw mechanism to achieve similar motion amplification. Li et al 34,35 proposed a new type of damper that combines eddy current damping with the rack and gear mechanism, which can be installed between the superstructure and foundation to reduce the seismic responses of base isolated structures. Furthermore, the required inertia force realized by the apparent mass can also be achieved by the rack and gear mechanism, which provides a novel way for structural vibration control.…”

“…Note that the PMs are arranged along the radial direction of the conductors, which is different from recent studies of the authors. 34,35 This arrangement is beneficial to reduce the deformation of the rotors and improve the manufacturing accuracy of dampers. The stators and rotors are both made of low-carbon steel materials, which also act as the back irons of the PMs and conductors, respectively.…”

Development and Application of a Power Law Constitutive Model for Eddy Current Dampers

“…The accuracy of the Wouterse constitutive model has been validated by researchers. For example, Li et al [22,23] employed the Wouterse constitutive model to characterize the damping behavior of rack and gear ECD mechanisms, and the theoretical and mechanical property test results exhibited good agreement with the Wouterse constitutive model. However, the Wouterse constitutive model poses a significant drawback when performing finite element analysis (FEA) for dynamic response.…”

A Review of Recent Developments in Permanent Magnet Eddy Current Couplers Technology

“…PMECCs use an electromagnetic field as the medium of power transmission, and have the characteristics of contactless torque transmission, removal of torque ripple, smooth dynamic process, and adjustable speed, and can be used as couplings, dampers, brakes, and speed governors. Over the past few decades, both academia and industry have witnessed the rapid development of PMECCs, which have been widely used for high-efficiency, adjustable, speed power transmission [1], non-contact braking [2][3][4], vibration absorption and damping [5][6][7][8][9], the removal of cogging torque and torque ripple in wind turbines [10][11][12][13][14][15], automotive variable flow water pumps [16], the torque-speed characteristic measurement of electric motors or vehicles [17,18], and even in vehicles as a mechanical differential [19].…”