1,721,186 research outputs found
Robust design of a composite air spindle
No full textIf the spindle shaft of an air spindle system is made of high-stiffness carbon fiber composite material, the spindle system will be dynamically robust because the maximum rotating speed of a spindle (or rotor) system is usually restricted by the critical whirling vibration frequency of the spindle shaft, which is proportional to (EI/m)(0.5) (E: Young's modulus, I: 2nd moment of inertia of shaft cross section, and m: mass per unit length of spindle). In this paper, a composite air spindle system composed of a high-modulus carbon fiber composite shaft, powder-containing epoxy composite squirrel cage rotor, and aluminum tool holder is introduced. For the optimal design of the composite air spindle system, the stacking sequence and thickness of the composite shaft were determined by considering the fundamental natural frequency and deformation of the system. Then the dynamic characteristics of the composite spindle system were compared with those of a conventional steel air spindle system
Performance of high speed air spindle motor equipped with composite squirrel cage rotor
No full textThe dynamic characteristics of a built-in motor type air spindle system can be improved by the reduction of mass of squirrel cage rotor because the critical whirling vibration frequency of a high speed air spindle system is highly dependent on the rotor mass of motor and the spindle specific bending modulus. In this paper the rotor of an AC induction motor was manufactured using magnetic powder containing epoxy composite whose density is half of conventional metal rotor and the motor shaft was made of high modulus carbon fiber epoxy composite material. In order to enhance the magnetic flux of the composite squirrel cage rotor of the motor, a steel core was inserted into the composite rotor. The magnetic behavior of composite squirrel cage rotor was analyzed with respect to shapes and positions of the conductor bars and the steel core of the rotor, and the optimal configuration for the dynamic performance of the rotor system was proposed. (C) 2002 Elsevier Science Ltd. All rights reserved
Influence of the steel core of composite squirrel cage rotor on motor performance
No full textSince the critical whirling vibration frequency of high speed built-in type motor spindle systems is dependent on the rotor mass of the built-in motor and the spindle specific bending modulus, the rotor and the shaft were manufactured using magnetic powder contained epoxy and high modulus carbon fiber epoxy composite, respectively. In order to enhance the magnetic flux of the composite squirrel cage rotor of an AC induction motor, a steel core was inserted into the composite rotor. The motor parameters of the developed composite rotor system were obtained from the no-load and blocked rotor tests and the effect of thickness of the steel core on the motor performance was investigated. From the magnetic analysis, the optimal steel core size for the dynamic characteristics of the rotor system mounted on the carbon fiber epoxy composite spindle was determined
Assessing chronic disease progression using non-homogenous exponential regression Markov models
No full textImprovement of the dynamic properties of a steel-composite hybrid flexspline of a harmonic drive
No full textThe harmonic drive is a special gear-drive speed reduction system whose operation principle is based on elastic deformation rather than rigid-body motion of the general gearing system. I;rom the components of the harmonic drive, the flexspline is the key element for the transmission of motion. It must be flexible in the radial direction, but must be stiff in the torsional direction to accurately transmit rotational motion. Because the contradictory dual role of the flexspline cannot be satisfied effectively with conventional isotropic materials, but can be achieved with anisotropic composite materials, in this paper the cup section of the flexspline was hybridly manufactured by laying-up composite material on the inside surface of the steel cup section. The static and dynamic characteristics of the hybrid flexspline were investigated with respect to the fibre volume fraction, stacking sequence and the mass ratio of the composite to steel. (C) 1997 Elsevier Science Ltd
Composite rotor for high-speed induction motors
No full textIn order to improve the dynamic characteristics of 3-phase AC induction motors, the squirrel cage rotor for a high speed builtin type motor spindle system was designed and manufactured with powder containing epoxy composite material and an aluminum squirrel cage. The Young's modulus, coefficient of thermal expansion (CTE), resistivity and magnetic permeability of the epoxy containing ferrite powder and iron powder were measured with respect to powder volume fraction to determine the optimum powder volume fraction. Then the epoxy powder composite rotor was manufactured by embedding the aluminum squirrel cage into the composite. Finally, the dynamic and electrical performances of the AC induction motor equipped with the developed composite rotor were measured and compared with those of a conventional AC induction motor. (C) 2000 Published by Elsevier Science Ltd
Optical Kerr effect in a direction-switched fiber laser gyroscope
No full textThe operation of a direction-switched mode-locked fiber laser gyroscope is described, We observed a large bias in the beat: frequency output, and found that it was caused by the optical Kerr effect when the two counterpropagating pulses in the laser cavity have different optical powers. The beat frequency bias was 65 Hz per 1 mW of power difference when the scale factor of the gyroscope was 0.43 kHz/(degrees/s). We found that a small amount of backscattering in the laser cavity could result in random fluctuations in the beat frequency. It is shown that the random frequency noise can be suppressed efficiently by applying push-pull phase modulation in the laser cavity
A programmable 3.2-GOPS merged DRAM logic for video signal processing
No full textIEEE Transactions on Circuits and Systems For Video Technology Sep. 2000.This paper proposes a programmable high-performance architecture of datapath in the merged DRAM logic (MDL) for video signal processing. A model of a datapath in the programmable MDL is generated, and two basic parameters, total reguired clock cycles (TRCC) and DRAM access rate (DAR), are defined by analysis of the model. Design guidelines are suggested for the optimized video signal processor based on the modeling and analysis of the MDL, The inverse discrete cosine transform (IDCT) and motion compensation (MC) of the video signal processing are analyzed in the MDL architecture. Two measures, TRCC and DAR, are determined such that the data bandwidth between DRAM and logic is not a bottleneck in the MDL architecture. The efficient datapath is designed based on these design guidelines. The datapath has processing units (ALU, MAC, and Barrel Shifter) with splittabilities of data and multi-port SRAM, The maximum performance of the proposed datapath with 200-MHz clock frequency is 3.2 GOPS for 8-bit video signals, which can deal with decoding high-level (1920 x 1080) in MPEG, The proposed MDL architecture has 2.1-4.8 times higher performance compared with conventional dedicated hardware chips. It can also be used for other multimedia signal processing due to its programmability
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