Improved Model of Radial Vibration in Switched Reluctance Motor Including Magnetic Saturation

This paper proposes an improved method for the prediction of radial vibration in switched reluctance motor(SRM)considering magnetic saturation.In this paper,the basic modeling principle is briefly introduced,it is based on the derivation that the peak acceleration is dependent on the product of phase current and current gradient idi/dt.However,the derivation may cause errors due to saturation effect.Thus in this paper,the discrete sample data are firstly acquired based on DC pulse measurement method,by which electromagnetic,torque and peak acceleration characteristics can all be acquired.Then the entire peak acceleration characteristics are obtained by improved Least Square Support Vector Machine(LSSVM).Based on the obtained static peak acceleration characteristics,the time-varied radial vibration model is established based on superposition of natural oscillations of dominant vibration modes.Finally,a simulation model is built up using MATLAB/Simulink.The good agreement between simulation and experiment shows that the proposed method for modeling is feasible and accurate,even under saturation.In addition,since LSSVM does not need any prior knowledge,it is much easier for modeling compared with other existing literatures.

RADIAL VIBRATIONS OF AXISYMMETRICALLY LOADED STEPPED PRESSURE VESSELS

Differential equations of free/forced radial vibrations of axisymmetrically loaded stepped pressure vessels are established by using singular functions. Furthermore, their general solutions are solved, the expression of vibration mode function and frequency equations on usual supports are derived with W operator and the forced response of such vessels are calculated.

Radial vibration of a slit-type annular ultrasonic concentrator

The radial vibration characteristic of an annular ultrasonic concentrator with multi- slits is studied. Based on the electro-mechanical analogy and by introducing an area ratio coef- ficient, the radial vibrational equivalent circuit and the frequency equation of the concentrator are derived. The radial displacement amplitude magnification factor of it is obtained. By nu- merical calculating, the relationship between the radial displacement amplitude magnification factor, the resonance frequency of the concentrator at the first and second resonance and its radius ratio are investigated. Also, the relationship between the radial displacement amplitude magnification factor, the resonance frequency of the concentrator and the length, the angle and the number of the silts are analyzed. It is illustrated that a maximum of displacement ampli- tude magnification factor of the concentrator appears with the increase of the radius ratio, and the amplitude magnification factor increase as the length, the angle and the number of the silts increase, while the radial resonance frequency of the concentrator decreases as the length, the angle and the number of the silts increase. The theoretical resonance frequencies are in good agreement with that of the FEM simulations and measurement.

Theoretical analysis and experimental validation of radial cascaded composite ultrasonic transducer

A radial cascaded composite ultrasonic transducer is analyzed.The transducer consists of three short metal tubes and two radially polarized piezoelectric ceramic short tubes arranged alternately along the radial direction.The short metal tubes and the piezoelectric ceramic short tubes are connected in parallel electrically and in series mechanically,which can multiply the input sound power and sound intensity.Based on the theory of plane stress,the electro-mechanical equivalent circuit of radial vibration of the transducer is derived firstly.The resonance/anti-resonance frequency equation and the expression of the effective electromechanical coupling coefficient are obtained.Excellent electromechanical characteristics are determined by changing the radial geometric dimensions.Two prototypes of the transducers are designed and manufactured to support the analytical theory.It is concluded that the theoretical resonance/anti-resonance frequencies are consistent with the numerical and experimental results.When R_(2) is at certain values,both the anti-resonance frequency and effective electromechanical coupling coefficient corresponding to the second mode have maximal values.The radial cascaded composite ultrasonic transducer is expected to be used in the fields of ultrasonic water treatment and underwater acoustics.

Synergistically enhancing the piezoelectric activity and Curietemperature of CaBi_(4)Ti_(4)O_(15) ceramics via co-doping Gd/Mn at theA/B-site

As a typical Aurivillius-type compound, CaBi_(4)Ti_(4)O_(15) (CBT) is considered a strong competitor among hightemperature piezoelectric materials, but it is difficult to achieve both high piezoelectric activity and a high Curie temperaturefor CBT. In this work, the method of double-ion co-substituting at different crystalline sites was used to modify the electricalproperties of CBT. The Gd/Mn co-doped CBT ceramics with the chemical formula of Ca_(1−x)Gd_(x)Bi_(4)Ti_(4)O_(15)+0.2 wt% MnO_(2)(CBT–100xGM, x = 0–0.11) were prepared via the conventional sintering process. The phase and valence band structures,chemical compositions and microstructures, dielectric and ferroelectric properties, electrical conduction behaviors, andelectroelastic and piezoelectric properties of the ceramics were characterized. The doping concentration effects of Gd^(3+)were analyzed according to the composition-dependent structures and properties of CBT–100xGM. The donor substitutionof Gd^(3+) for Ca^(2+) at the A-site reduced the tolerance factor of the perovskite-like structure and decreased the concentration ofintrinsic oxygen vacancies. While Mn^(3+) tended to substitute for Ti4+ at the B-site, the extrinsic oxygen vacancies are limitednear the defect center of Ti(Mn) because of the formation of ( ‒MnTi')• as defect dipoles. The thermal depoling behavior ofthe CBT–100xGM ceramics between 300 and 700 ℃ was explained by the thermodynamic characteristics of the defectdipoles. The optimized composition with x = 0.08 (CBT–8GM) had a high TC ≈ 809 ℃ and a high piezoelectric coefficient(d33) ≈ 23 pC/N, as well as a piezoelectric voltage constant (g33) value of up to 21.5×10^(−3)(V·m)/N. Moreover, it can maintaina residual d33 ≈ 80% after being annealed at 700 ℃. This good anti-thermal depoling ability endows this material with greatapplication potential in high-temperature piezoelectric devices with operating temperatures exceeding 500 ℃. Thesynergistic enhancement in the piezoelectric activity and Curie temperature of CBT can be attributed mainly to the donorsubstituting effect of Gd^(3+) at the A-site, as well as the decreased elastic compliance contributed by MnO_(2) as the B-sitedopant.