Simulation of a vibrating reed exciter for thickening different fabrics in weaving loom
Keywords:permanent magnets, vibration exciters, damping, stiffness, dynamic analysis
A new weaving loom vibrating mechanism excited electromagnetically has been elaborated and presented in the article. The aim of the study has been to analyze the changes of electrical and dynamical parameters of vibrating system comprising the weaving loom with the reed forced to the vibrations by the special exciter. The magnetic field in the magnetic circuit of the exciter has been consisted of a steel core, the two steel pole pieces, permanent magnet and air gaps. In the air gaps of the magnetic circuit there have been arranged the serially connected coil segments, with a counter wound windings. It has been used the Nd-Fe-B permanent magnet. In an electrical circuit, which includes copper windings of the coil segments, alternating current flows, causing generation of the resultant electro-dynamic force exciting the motion of the coil segments along their axis. Using Finite Element Method a model of the exciter has been elaborated for calculation of changes in the resultant inductance of the exciter coils with the increasing the coils displacement against the stator and with increasing the current flowing in the coil windings. During analysis it has been used the axisymmetrical model, making the analysis simpler. The mesh of triangular finite elements has been created automatically by the commercial program FEMM. The appropriate boundary conditions, material parameters and extortion were introduced into the model. Based on the obtained results it has been assumed the constant value of coil inductance for the range of analyzed coil displacements, which have been smaller than 1 mm. Also the calculation model for the vibrating reed system has been elaborated and shown in the article. The electrical and dynamical parameters of the vibrating system have been simulated under conditions of thickening the fabrics of different thickness and supply with ac power. It has been analyzed the waveforms of the current in the exciter coils and their changes as the function of dynamic parameters of the created fabric. It has been also studied the influence of supply voltage and parameters of the created fabric for the peak values of current flowing in the exciter coils. It has been obtained the waveforms of the vibrational motion of the reed for various parameters of the created fabrics. It has been analyzed the reduction of the operating amplitude of the vibrational motion with respect to the start-up amplitude. It has been concluded, that the reduction of the operating amplitudes of the reed vibrating movement occurs together with the values of dynamic parameters of the thickened fabric. In extreme cases, for fabrics characterized by relatively high damping and significant stiffness it reaches 50%. It has been also noted, that during thickening the fabrics with typical dynamic parameters, the operating amplitude of the reed vibrating motion reaches 70 - 90% of the peak start-up amplitude. Also the peak values of flowing current have been observed during the start-up and during the operating movement of the reed in the extreme position of weaving loom. It also have been observed, that the peak value of the flowing current during the phase of operating vibratory motion of the reed in-creases with the stiffness and the mean value of current increases with the damping coefficient of thickened fabric.