CONTROL OF PASSAGE THROUGH RESONANCE ZONE FOR 1-ROTOR VIBRATION UNIT WITH TIME-VARYING LOAD

The speed-gradient algorithms for controlled passage through the resonance zone of the one-rotor vibration unit are studied by computer simulation. The objective of the study is to analyze dependence of the control performance on the loading mode and the electric drive dynamics. In order to obtain an algorithm better suitable for practical implementation the theoretically designed algorithm is simplified by simplifying the expression for the total energy. First of all, we neglect the terms corresponding to the kinetic and potential energy of the load, since there are no load mass sensors on the stand. the term containing the inclination angle of the platform is neglected. In addition, the platform inclination angle and dynamics of the drives were neglected too. Efficiency of the proposed simplified algorithm for different loading modes, including linear loading with different loading rates and sine-shaped oscillatory loading.

THE SYSTEM OF FORMING THE CONTROL MODE OF THE ELECTRIC DRIVE DURING THE START-UP OF THE VIBRATION MACHINE

The above resonance vibration machines are widely used in various industries, but have a number of shortcomings associated with increasing of the oscillations amplitude when passing the resonance zone during start-up. It is noted that to reduce the oscillations amplitude and quickly pass the resonance zone, it is advisable to use a frequency-controlled electric drive with the formation of additional control effects. Features of frequency start of the electric drive of the vibration machines are noted. The structure of the electric drive control system during passing the resonance zone in the process of starting the above resonance vibration machine in the form of a block-scheme is proposed. The algorithm of operation of the control system is given.

Numerical Investigation of Sloshing Under Roll Excitation at Shallow Liquid Depths and the Effect of Baffles

Sloshing is relevant in several applications like ship tanks, space and automotive industry and seiching in harbours. Due to the relationship between ship and sloshing motions and possibility of structural damage, it is important to represent this phenomenon accurately. This paper investigates sloshing at shallow liquid depths in a rectangular container using experiments and RANS simulations. Free and forced sloshing, with and without baffles, are studied at frequencies chosen specifically in proximity to the first mode natural frequency. The numerically calculated free surface elevation is in close agreement with observations from experiments. The upper limit of the resonance zone, sloshing under different filling depths and roll amplitudes and sloshing with one, two and four baffles are also investigated. The results show that the extent of the resonance zone is reduced for higher filling depth and roll amplitude. It is also found that the inclusion of baffles moves the frequency at which the maximum free surface elevation occurs, away from the fundamental frequency. Finally, a submerged baffle is found to dissipate more energy compared to a surface piercing baffle and that the effect of several submerged baffles is similar to that of a single submerged baffle.

ROM of Superharmonic Resonance of Fourth Order of Electrostatically Actuated Clamped MEMS Circular Plates: Voltage Response

This paper investigates the voltage-amplitude response of superharmonic resonance of fourth order of electrostatically actuated clamped MEMS circular plates. The system consists of flexible MEMS circular plate parallel to a ground plate. Hard excitations (voltage large enough) and AC voltage of frequency near one eight of the natural frequency of the MEMS plate resonator lead it into a superharmonic resonance. Hard excitations produce actuation forces large enough to produce resonance away from the primary resonance zone. There is no DC component in the voltage applied. The partial differential equation of motion describing the behavior of the system is solved using two modes of vibration reduced order model (ROM). This model is solved through a continuation and bifurcation analysis using the software package AUTO 07P which produces the voltage-amplitude response (bifurcation diagram of the system, and a numerical integration of the system of differential equations using Matlab that produces time responses of the system. Numerical simulations are conducted for a typical MEMS silicon circular plate resonator. For this resonator the quantum dynamics effects such as Casimir effect or Van der Waals effect are negligible. Both methods show agreement for the entire range of voltage values and amplitudes. The response consists of an increase of the amplitude with the increase of voltage, except around the value of 4 of the dimensionless voltage where the resonance shows two saddle-node bifurcations and a peak amplitude about ten times larger than the amplitudes before and after the dimensionless voltage of 4. The softening effect is present. The pull-in voltage is reached at large values of the dimensionless voltage, namely about 14. The effects of damping and frequency on the voltage response are reported. As the damping increases, the peak amplitude decreases for the resonance. However, the pull-in voltage is not affected. As the frequency increases, the resonance zone is shifted to lower voltage values and lower peak amplitudes. However, the pull-in voltage and the behavior for large voltage values are not affected.

On the divergence of first-order resonance widths at low eccentricities

ABSTRACT Orbital resonances play an important role in the dynamics of planetary systems. Classical theoretical analyses found in textbooks report that libration widths of first-order mean motion resonances diverge for nearly circular orbits. Here, we examine the nature of this divergence with a non-perturbative analysis of a few first-order resonances interior to a Jupiter-mass planet. We show that a first-order resonance has two branches, the pericentric and the apocentric resonance zone. As the eccentricity approaches zero, the centres of these zones diverge away from the nominal resonance location but their widths shrink. We also report a novel finding of ‘bridges’ between adjacent first-order resonances: at low eccentricities, the apocentric libration zone of a first-order resonance smoothly connects with the pericentric libration zone of the neighbouring first-order resonance. These bridges may facilitate resonant migration across large radial distances in planetary systems, entirely in the low-eccentricity regime.

Selected Tribological Properties and Vibrations in the Base Resonance Zone of the Polymer Composite Used in the Aviation Industry

The revolution in the global market of composite materials is evidenced by their increasing use in such segments as the transport, aviation, and wind industries. The innovative aspect of this research is the methodology approach, based on the simultaneous analysis of mechanical and tribological loads of composite materials, which are intended for practical use in the construction of aviation parts. Simultaneously, the methodology allows the composition of the composites used in aviation to be optimized. Therefore, the presented tests show the undefined properties of the new material, which are necessary for verification at the application stage. They are also a starting point for further research planned by the authors related to the improvement of the tribological properties of this material. In this article, the selected mechanical and tribological properties of an aviation polymer composite are investigated with the matrix of L285-cured hardener H286 and six reinforcement layers of carbon fabric GG 280P/T. The structure of a polymer composite has a significant influence on its mechanical properties; thus, a tribological analysis in the context of abrasive wear in reciprocating the movement for the specified polymer composite was performed. Moreover, the research was expanded to dynamic analysis for the discussed composite. This is crucial knowledge of material dynamics in the context of aviation design for the conditions of resonance vibrations. For this reason, experimental dynamical investigations were performed to determine the basic resonance of the material and its dynamics behavior response. The research confirmed the assumed hypotheses related to the abrasive wear process for the newly developed material, as well as reporting an empirical evaluation of the dependencies of the resonance zone from the fabric orientation sets.