The construction of the amplitude-frequency characteristic of a magnetically controlled hydraulic bearing under the influence of a constant magnetic field on a magnetorheological fluid (MRF) in throttle channels at different temperatures is considered. The eigenfrequencies of the hydraulic bearings at different temperatures of the MRF and the connected masses in the magnetorheological transformer are determined. Keywords: hydraulic bearing, magnetorheological fluid, throttle channels, magnetorheological transformer, viscosity, connected mass, amplitude-frequency characteristic. gord349@mail.ru, oxulkovs@mail.ru
When designing electric drives based on brushless DC motors with permanent magnets (BLDC), which have low level torque pulsations, the problem of modelling non-standard topological solutions appears. The known models of BLDC motors are either based on the assumptions about the symmetry of the stator pa-rameters of the electric motor and/or the ideal form of the phase back-EMF waveform, which reduce the accuracy of evaluating the effectiveness of the proposed solutions or prove unusable for modelling an operation of the electric motor with a non-standard semiconductor converter. It is necessary to develop a mathematical model of the BLDC motor-based electric drive that takes into account the structural features of the electric motor and allows for semiconductor converter configuration variability. The model is designed in the Matlab Simulink environment. The verification is carried out by comparing the modelling results with experimental data obtained previously by other researchers. The proposed method for generating phase back-EMF in the BLDC motor model provides the possibility for the user to set the EMF form templates independent for each phase. The proposed method for stator circuit simulating provides the user with access to each of the stator windings leads as well as with the possibility of asymmetric determination of each parameter of the electric motor. Upon verification, it has been shown that the difference in the control points between the simulated and experimental speed-torque curves does not exceed 3,5 %. The developed model allows analyzing the static and dynamic characteristics of operation modes of non-standard topology BLDC motor-based electric drives taking into account the stator pa-rameters asymmetry and the real phase back-EMF waveform. The specified features of the model allow exploring the operation of the designed electric drive, taking into account the BLDC motor and converter design. The model can be applied when checking atypical design decisions and when changing the set parameters of the electric drive and restrictions on working conditions and target functions to refine the control system algorithms and automate the search for optimal parameters of the motor and the semiconductor converter.
The article proposes a mathematical model of temperature control of a multi-phase gas-hydraulic vibration isolator due to application of gas-regulated heat pipe. During the operation of the vibration isolator with magnetorheological transformers, mechanical energy is absorbed, which is converted into heat. The use of a gas-controlled heat pipe ensures the removal of heat from the object, the creation of an isothermal zone inside it and the temperature stabilization of the object. This ensures the preservation of the working properties of the magnetorheological fluid, in particular, its viscosity, and practically stabilizes the parameters of the amplitude-frequency characteristic of the vibration-insulator, regardless of the time of continuous operation and the ambient temperature. The article presents experimental methods for determining the thermal coefficient and rate of heating of a vibration-isolator, which allows making reasonable design decisions in the design of vibration protection systems.
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