scholarly journals Effect of System Parameters on Natural Frequency of the Pelton Turbine

2018 ◽  
Vol 4 ◽  
pp. 75-81
Author(s):  
Laxman Motra ◽  
Sanjeev Karki
Keyword(s):  
Natural Frequency ◽  
Rotational Speed ◽  
Turbine Unit ◽  
Continuous System ◽  
System Model ◽  
System Parameters ◽  
Pelton Turbine ◽  
Backward Whirl

The effect of diameter, length and rotational speed of shaft, and mass of runner-buckets assembly on the natural frequency of the Pelton turbine unit was analyzed. Effect of the decisive parameters on the natural frequency of the unit showed that it was directly proportional to the diameter of the shaft and inversely proportional to the length of the shaft and mass of the runner-buckets assembly. For the continuous system model, when the rotational speed of the shaft increased, the natural frequency for the forward whirl also increased but the natural frequency decreased for the backward whirl.

Vibration of Bending-Torsion Coupled Resonance in a Rotor

2013 ◽  
Author(s):  
Hiroyuki Fujiwara ◽  
Tadashi Tsuji ◽  
Osami Matsushita
Keyword(s):  
Numerical Simulations ◽  
Natural Frequency ◽  
Torsional Vibration ◽  
Rotational Speed ◽  
Coupling Effect ◽  
The Other ◽  
Resonance Phenomenon ◽  
Horizontal Direction ◽  
Bending Vibration ◽  
Rotor Systems

In certain rotor systems, bending-torsion coupled resonance occurs when the rotational speed Ω (= 2π Ωrps) is equal to the sum/difference of the bending natural frequency ωb (= 2π fb) and torsional natural frequency ωθ(= 2πfθ). This coupling effect is due to an unbalance in the rotor. In order to clarify this phenomenon, an equation was derived for the motion of the bending-torsion coupled 2 DOF system, and this coupled resonance was verified by numerical simulations. In stability analyses of an undamped model, unstable rotational speed ranges were found to exist at about Ωrps = fb + fθ. The conditions for stability were also derived from an analysis of a damped model. In rotational simulations, bending-torsion coupled resonance vibration was found to occur at Ωrps = fb − fθ and fb + fθ. In addition, confirmation of this resonance phenomenon was shown by an experiment. When the rotor was excited in the horizontal direction at bending natural frequency, large torsional vibration appeared. On the other hand, when the rotor was excited by torsion at torsional natural frequency, large bending vibration appeared. Therefore, bending-torsion coupled resonance was confirmed.

Eigensensitivity of Planetary Gear Free Vibration Properties

1999 ◽  
Author(s):  
Jian Lin ◽  
Robert G. Parker
Keyword(s):  
Kinetic Energy ◽  
Free Vibration ◽  
Natural Frequency ◽  
Vibration Mode ◽  
Planetary Gear ◽  
Planetary Gears ◽  
System Parameters ◽  
Frequency Sensitivity ◽  
Vibration Properties ◽  
Inertia Parameters

Abstract The natural frequency and vibration mode sensitivities to system parameters are rigorously investigated for both tuned and mistimed planetary gears. Parameters under consideration include support and mesh stiffnesses, component masses, and moments of inertia. Using the well-defined vibration mode properties of tuned (cyclically symmetric) planetary gears [1], the eigensensitivities are calculated and expressed in simple, exact formulae. These formulae connect natural frequency sensitivity with the modal strain or kinetic energy and provide efficient means to determine the sensitivity to all stiffness and inertia parameters by inspection of the modal energy distribution. While the terminology of planetary gears is used throughout, the results apply for general epicyclic gears.

Dynamics of a Continuous System With Clearance and Motion Limiting Stops

1999 ◽  
Author(s):  
P. Metallidis ◽  
S. Natsiavas
Keyword(s):  
Piecewise Linear ◽  
Research Work ◽  
Continuous System ◽  
Continuous Model ◽  
Equation Of Motion ◽  
Model System ◽  
Periodic Motions ◽  
System Parameters ◽  
Rigid Rods ◽  
The Stability

Abstract The present study generalises previous research work on the dynamics of discrete oscillators with piecewise linear characteristics and investigates the response of a continuous model system with clearance and motion-limiting constraints. More specifically, in the first part of this work, an analysis is presented for determining exact periodic response of a periodically excited deformable rod, whose motion is constrained by a flexible obstacle. This methodology is based on the exact solution form obtained within response intervals where the system parameters remain constant and its behavior is governed by a linear equation of motion. The unknowns of the problem are subsequently determined by imposing an appropriate set of periodicity and matching conditions. The analytical part is complemented by a suitable method for determining the stability properties of the located periodic motions. In the second part of the study, the analysis is applied to several cases in order to investigate the effect of the system parameters on its dynamics. Special emphasis is placed on comparing these results with results obtained for similar but rigid rods. Finally, direct integration of the equation of motion in selected areas reveals the existence of motions, which are more complicated than the periodic motions determined analytically.

scholarly journals Comparative Analysis of Polarimetric SAR Calibration Methods

2018 ◽  
Vol 10 (12) ◽  
pp. 2060 ◽  
Author(s):  
Yoon Jung ◽  
Sang-Eun Park
Keyword(s):  
Comparative Analysis ◽  
Calibration Method ◽  
System Model ◽  
Synthetic Aperture ◽  
Polarimetric Sar ◽  
Alos Palsar ◽  
Polarimetric Synthetic Aperture Radar ◽  
System Parameters ◽  
Calibration Methods ◽  
Polarimetric Calibration

In the diverse applications of polarimetric Synthetic Aperture Radar (SAR) systems, it is a crucial to conduct polarimetric calibration, which aims to remove the radar system distortion effects prior to utilizing polarimetric SAR observations. The objective of this study is to evaluate the performance of different polarimetric calibration methods. Two widely used methods, the Van Zyl and Quegan methods, and one recently proposed method, such as the Villa method, have been selected among various calibration methods in literature. The selected methods have basic differences in their assumptions that are applied to the polarimetric system model. In order to evaluate the calibration performances under different system parameters and ground characteristics, comparative analysis of the calibration results were conducted on synthetic polarimetric SAR data and ALOS PALSAR quad-pol mode data. Based on the experimental results, the advantages and limitations of different methods were clarified, and a simple hybrid calibration method is presented to further improve the polarimetric calibration performance.

scholarly journals The Design of Follow-up Hydraulic Muffler Based on Spring-Damp Regulating Device

2019 ◽  
Vol 79 ◽  
pp. 01006
Author(s):  
Chang-ji Shan ◽  
Yi-duo Bian ◽  
Ting-ting Dai ◽  
Cai Yan ◽  
Guo-fang Du ◽  
...  
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Rotational Speed ◽  
Pulsation Frequency ◽  
Attenuation Effect ◽  
Static And Dynamic Characteristics ◽  
Section Area

The follow-up hydraulic muffler can make the natural frequency of the muffler equal to systematic pulsation frequency in time by changing the section area of the quality chamber so as to achieve the best attenuation effect. In this paper, a spring-damp regulator is installed on the basis of the hydraulic muffler, and the static and dynamic characteristics of the follow-up hydraulic muffler are analyzed by measuring the rotational speed of the pump with the sensor. The results show that the hydraulic muffler based on the spring-damp regulator can effectively attenuate the pulsation.

The Simulation of Robot Control Based on CMAC Neural Network PID Control Algorithm

2013 ◽  
Vol 336-338 ◽  
pp. 659-663
Author(s):  
Jian Li Yu ◽  
Ya Zhou Di ◽  
Lei Yin
Keyword(s):  
Neural Network ◽  
Pid Control ◽  
Robot Control ◽  
Control Algorithm ◽  
External Disturbance ◽  
System Model ◽  
Robot System ◽  
System Parameters ◽  
Cmac Neural Network ◽  
Neural Network Pid

According to the problem of nonlinear and uncertainty in robot control, this paper proposes a PID control algorithm based on CMAC neural network model, for the elimination of the influence of uncertainty caused by robot system parameters and external disturbance. The simulation results show that this algorithm can effectively overcome the uncertainties and external disturbance of robot system model, this algorithm has good robustness and stability, its performance is superior to the traditional PID control algorithm.

A Study of Nonlinear Behavior of Flexible Tool and Workpiece in Turning Operation With Regenerative Effect Under Internal and Primary Resonance Conditions

2020 ◽  
Vol 15 (6) ◽  
Author(s):  
Arnab Chanda ◽  
Santosha K. Dwivedy
Keyword(s):  
Cutting Force ◽  
Natural Frequency ◽  
Resonance Condition ◽  
Primary Resonance ◽  
Flexible Tool ◽  
Turning Operation ◽  
System Parameters ◽  
Regenerative Effect ◽  
Excited Vibration ◽  
Cylindrical Workpiece

Abstract In this work, the nonlinear dynamic behavior of turning operation has been studied considering flexible tool and thin cylindrical workpiece. The system is taken as a two-degree-of-freedom system with nonlinear stiffness and is subjected to self-excited vibration because of the regenerative effect. The cutting force is considered to be a combination of a constant and periodic force in addition to the force due to the regenerative effect. The regenerative effect during turning operation is included in the mathematical model, resulting in a nonlinear delay differential equation. Here, the natural frequency of the workpiece is assumed to be closed to that of the tool, leading to 1:1 internal resonance. Further, the frequency of the time-varying cutting force is assumed to be closed to the natural frequency of the workpiece giving rise to primary resonance condition. The nonlinear responses and the stability of the tool and the workpiece have been determined using a higher-order method of multiple scales (MMS) under internal and primary resonance conditions. The solution of the equation of motion using the MMS is validated by comparing the solution obtained using the numerical method. The effect of the tool and workpiece stiffness nonlinearities on steady-state frequency responses and stability is investigated, and system parameters are also identified to have stable turning operation. This work will find applications in estimating the system parameters for chatter-free turning operation with a flexible tool and workpiece when their dynamic compliances are comparable.

Tool Oscillation and the Formation of Lobed Holes in a Quasi-Static Model of Reaming

1999 ◽  
Author(s):  
Philip V. Bayly ◽  
Keith A. Young ◽  
Jeremiah E. Halley
Keyword(s):  
Eigenvalue Problem ◽  
Natural Frequency ◽  
Cutting Speed ◽  
Static Model ◽  
Viscous Damping ◽  
Backward Whirl ◽  
Static Approach ◽  
Hole Profile

Abstract A quasi-static model of reaming is used to explain oscillation of the tool during cutting and the resulting roundness errors in reamed holes. Tools with N evenly-spaced teeth often produce holes with N+1 or N-1 “lobes”. These profiles correspond, respectively, to forward or backward whirl of the tool at N cycles/rev. Other whirl harmonics (2N cycles/rev, e.g.) are occasionally seen as well. The quasi-static model is motivated by the observations that relatively large oscillations occur at frequencies well below the natural frequency of the tool, and that in this regime the wavelength of the hole profile is largely independent of both cutting speed and tool natural frequency. In the quasi-static approach, inertial and viscous damping forces are neglected, but the system remains dynamic because regenerative (time-delayed) cutting and rubbing forces are included. The model leads to an eigenvalue problem with forward and backward whirl solutions that closely resemble the tool behavior seen in practice.

A Continuous System Model of Adrenocortical Function

1968 ◽  
pp. 141-184 ◽  
Author(s):  
F. E. Yates ◽  
R. D. Brennan ◽  
J. Urquhart ◽  
M. F. Dallman ◽  
C. C. Li ◽  
...  
Keyword(s):  
Continuous System ◽  
System Model ◽  
Adrenocortical Function

Blade-Shaft Coupled Resonance Vibration by Using Active Magnetic Bearing Excitation

2008 ◽  
Author(s):  
Norihisa Anegawa ◽  
Hiroyuki Fujiwara ◽  
Osami Matsushita
Keyword(s):  
Natural Frequency ◽  
Rotational Speed ◽  
Critical Speed ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Dynamic Vibration Absorber ◽  
Blade Vibration ◽  
Lower Natural Frequency ◽  
Damped System ◽  
Spring System

The turbine generator requires sufficient reliability as a major component of the power plant. The rotor dynamics calculates the critical speed of the shaft-bearing system for design to avoid appearance of the critical speed, while the blade dynamics calculates the natural frequency of the blade to avoid nX resonance. For longer blades, however, the lower natural frequency requires that the design of the shaft and blade takes into account the coupling of the blade vibration mode with nodal diameter k = 0 and k = 1 with the vibration of the shaft. The present work analyzes the coupling of the parallel motion of the shaft with the in-plane vibration of the blade within k = 1 modes. More specifically, the existence of an unstable region due to coupling and the coupled resonance in an eight-blade (N = 8) where each blade is assumed to be a 1-DOF mass-spring system were analyzed in detail. Analysis was also made on the forced vibration of a stable damped system. At a rotational speed Ω = |ωs − ωb|, the vibration of the shaft was limited to a relatively small amplitude due to anti-resonance points resulting from the dynamic vibration absorber effect, while the resonance of the blades was relatively big amplitude. A violent coupled resonance resulting from the dynamic absorber effect of the blades and shaft was observed at a rotational speed Ω = ωs + ωb. The resonance in blade vibration at Ω = |ωb − ωs| was experimentally confirmed.

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