Shaft Torsional Vibration Research Articles

Active Vibration Control of a Motor System by H∞ Control

This paper treats the vibration control of a motor system which has a motor and a load connected with a flexible shaft. This system often generates a shaft torsional vibration. To suppress this vibration, we propose a new approach based on H∞ control theory. For comparison, we also constructa PI control system based on classical control theory. The results of several experiments show that the H∞ control system is more effective in suppressing the vibration than the PI control system.

Active Vibration Control of a Motor System by Using H.INF. Control Theory.

This paper considers the vibration control of a motor system which has a motor and a load connected with a flexible shaft. However, this system often generates a shaft torsional vibration. Traditional methods of treating this problem to adjust the PID controller so that the closed-loop frequency response is slower than that of the vibration mode. On the other hand, one method has already been proposed in which the vibration is suppressed by a disturbance observer. This paper proposes a new approach based on H∞ control theory. For comparison, a PI control system based on classical control theory also is constructed. The results of several experiments show that compared with the PI control system, the H∞ control system is effective in suppressing the vibration. Further, the H∞ controller obtained in the study consists of a PI controller and a series compensator that functions as an active vibration controller.

Methods of investigating torsional vibrations of shafts of mobile compressor stations

Methods of investigating torsional vibrations of shafts of mobile compressor stations

Monitoring of exciter shaft torsional vibrations

First Page

Single and multi-purpose optimization of vibrating Timoshenko shafts

Optimization of transversely vibrating shafts with respect to eigenfrequencies, with constraints on the design variables, has been almost fully investigated in recent years - as far as the Bernoulli-Euler equation of motion is concerned. In the present paper, Timoshenko's equations are applied, i.e. the effects of shear and rotational energy are taken into account in the calculation of the transverse vibration modes and frequencies of the shaft. This is done via a finite element formulation. The sensitivity analysis of the transverse vibration frequencies is based on analytical differentation of the stiffness- and mass matrices. The computer program developed provides the user with an option to suppress the Timoshenko effects, such that the analysis can be carried out within the Bernoulli-Euler theory as well and then comparisons can be made. Torsional vibrations of shafts are also considered, computing the vibration modes and natural frequencies by means of a finite difference approach. Again, the sensitivity analysis is carried out analytically. Objective functions and behavioral constraints are selected from fundamental frequencies, higher order frequencies and differences between adjacent frequencies of the vibrational types considered. The cross-sectional area function of the shaft is used as the design variable and the total volume of structural material is assumed to be given, along with some sizing constraints. The shafts considered may be equipped with non-structural disks and flexible supports. Several examples are presented and some notable differences between optimized Timoshenko and Bernoulli-Euler shafts derived.

Impact of Shaft Torsionals in Steam Turbine Control

Shaft torsional vibrations are discussed along with their effect on steam turbine-generator control following severe supply-network disturbances and the destabilization of shaft torsional modes through the action of high-speed electrohydraulic controllers. It is shown that shaft flexibility can exert a significant influence on steam turbine-generator response following a severe supply-system disturbance, particularly when the turbine has nonlinear valve stroking and fast valving. The effect can be minimized by the careful location of a speed sensor along the turbine shaft and by filtering speed or acceleration signals to reduce the speed input of troublesome low-frequency torsional vibrations to an insignificant level. The effect of shaft torsionals on control system response to an islanding situation and on the above mentioned destabilization is evaluated. Digital implementation of steam-turbine control systems in relation to quantization, sampling, response time in protection systems, and software integrity is examined. >

A Microprocessor-Based Motor Speed Regulator Using Fast-Response State Observer for Reduction of Torsional Vibration

A new state observer, which is suitable for microprocessor-based motor drives, and its application to suppression control of shaft torsional vibration are described. A distinct feature of the state observer is that a fast-response load torque estimation is obtained by processing the detected motor current and the encoder output pulses by a hardware circuit for each encoder pulse generation. Suppression control of the shaft torsional vibration is achieved by calculating a compensation signal from the estimated load torque with the microprocessor software. A microprocessor-based speed regulator for dc motor drives, which utilizes the state observer and suppression control of the shaft torsional vibration, was developed for evaluation purposes and tested with a 15-kW dc motor. The load torque of the motor can be estimated accurately, even with a 15-Hz vibration frequency, and the torsional vibration can be eliminated with the proposed suppression control.

Torsional vibration of shafts coupled by mechanisms

The paper is concerned with torsional vibration of a system composed of two parallel shafts coupled together by a number of mechanisms. The analysis has been done by using both non-linear and approximate linear equations. It is shown that there are three predominant sources of vibrations: (i) the tendency to different speed fluctuations of each mechanism; (ii) difierent mode configurations of the shafts; (iii) the fact that the inertia and the stiffness of the system are not varying proportionally to one another. The instability regions, the vibration amplitude and the range of fluctuation of the driving torque for a double crank-and-rocker mechanism are illustrated graphically.

Electrical Damping and its Effect on Accumulate Fatigue Life Expenditure of Turbine-Generator Shafts Following Worst-Case Supply System Disturbances

The paper examines the effect electrical phenomena has on damping torsional vibrations of turbine-generator shafts resulting from severe disturbances on the system supply. The effect system impedance and power factor has on time constants for decay of predominant shaft torsional vibrations and on fatigue life expenditure of the shaft following worstcase events is investigated. The impact pole slipping resulting from delayed fault clearance has on peak shaft torque and on accumulative fatigue life expenditure of the shaft is also examined.

Heat propagation due to torsional vibration of shafts

Torsional vibration of rotating shafts can yield substantial temperatures in the shaft due to heat generated from material damping. It has been recently observed that such a situation in electric generators can lead to insulation failures and machine outages. In the study reported here forced torsional vibration is assumed, and both lumped mass and continuous systems are considered. The hysteretic model for material damping is used to yield the heat generation in the elastic deformation range and an elastoplastic material is assumed in the plastic range. The heat conduction equation is solved for a cylindrical shaft with surface cooling. Closed form solutions and expressions for the maximum temperatures and the maximum surface temperatures are obtained and tabulated for design purposes. It is shown that substantial temperatures can develop in shafts undergoing torsional vibration.

Characteristic Frequencies and Mode Shapes for TurboGenerator Shaft Torsional Vibrations

Fundamental to the study of turbogenerator shaft torsional vibrations, as occur in subsynchronous resonance and high speed reclosing, is the calculation of the characteristic frequencies and associated mode shapes of the vibrations. A calculation procedure is discussed which is based on distributed ed system concepts and does not require matrix eigenvalue-eigenvector routines as does the conventional method based on lumped inertia and compliance. The procedure is of value in the analysis and simulation of torsional vibrations.

Subsynchronous Resonance and Torsional Stresses in Turbine-Generator Shafts

A brief introduction to the phenomenon of sustained oscillation of a power system at subsynchronous frequencies is presented. Such oscillations result from the application of capacitors used for series compensation of transmission lines. A state-space model is employed to represent the action of subsynchronous armature currents on turbine- generator shaft torsional vibrations. A digital simulation program for the analysis of turbine generator shaft characteristics based on the state-space model is outlined. Two examples based on typical system parameters are given.

A pocket calculator program for some simple vibration problems

An earlier buckling program [1] has been adapted to give the natural frequencies and mode shapes for free axial vibrations of bars, transverse vibrations of taut wires and torsional vibrations of shafts. The cross section of the bar, wire or shaft can vary at intervals along its length, and so can its distributed mass (or inertia for the shaft), which is allowed for in a classically exact way. Lumped masses (or rotors for shafts) and spring supports can be attached anywhere along the length, and the ends can be free or clamped. The program just fits on a Hewlett-Packard HP-25 pocket calculator, which can store only 49 program steps and 13 numbers.

Compact distributed inertia solution for free torsional vibrations of shaft and rotor system

A method is presented for finding the natural frequencies and modes for free torsional vibrations of a shaft with attached rotors. The distributed inertia of the shaft is represented “exactly”, according to classical theory. The method cannot miss any required natural frequency. The method is illustrated by a program for a programmable calculator. About 150 registers of program and data storage are required for a ten rotor system.

Damping of Torsional Vibrations by Dry Friction

The problem of damping out structural vibrations by the use of dry (Coulomb) friction, already discussed in relation to beam-like structures in a previous paper (1)†, is here considered in relation to the torsional vibrations of shafts.

On the Torsional Vibrations of the Shafts System Having a Periodically Variable Moment of Inertia : Specially the Bad Effect of the Finite Length of the Connecting Rod on the Ranges of the Unstable Vibration

This paper presents the effects of the finite length of the connecting rod on the ranges of unstable vibrations for the torsional vibrations of the shafts systems having a periodically variable moment of inertia and viscous damping force. In studying this problem, we established a differential equation containing a parameter λ, which is the ratio of the crank radius to the length of connecting rod, and a damping parameter δ. We solved this equation by the method of successive approximation, and as the results we obtained the following two remarkable points. First, in the case of no damping, there arise the unstable vibrations in the vicinities of the number of revolutions of shaft 2Ner, 2/3Ner and 1/2Ner in addition to the vicinity of Ner, which corresponds to the ordinary critical speed for torsional vibrations of shaft. Secondly, we pointed out by considering δ that the unstable ranges were reduced and there exists the "ranges of taking along by (Mitnahmebereich(6))" over the unstable ranges, though it is not too much to say that there is no literature considering the damping parameter δ.

Elastic Torsional Vibration of Crank Shaft Torsional Vibration of No-Damping (No.1)

Elastic Torsional Vibration of Crank Shaft Torsional Vibration of No-Damping (No.1)

Month in the Patent Office

336,795. Indicating and recording torsional vibration of shafts. Gerard, I. J., and Carter, B. C, Royal Aircraft Establishment, South Farnborough, Hampshire, and Mansell, H. C, Rathgar, Ashley Road, Walton‐on‐Thames. Oct. 17, 1929. No. 31565. [Class 106 (ii).] Dynamometers, rotary transmission: with recording‐apparatus.—Comprises a construction of the type in which the torsional vibrations of a shaft are used to tilt a mirror reflecting a beam of light on to a screen of photographic plate.

Corrigendum: The torsional vibration of shafts and shaft systems

Corrigendum: The torsional vibration of shafts and shaft systems

The torsional vibration of shafts and shaft systems

Problems of torsional oscillation frequently arise in the various branches of engineering and present difficulties in the way of their solution.The investigation of four and more masses is involved and calls for a considerable expenditure of time.In the present paper the general theory of torsional oscillation is first reviewed, and a method is then evolved by which the investigation of any number of vibrating masses is considerably simplified. A worked example is appended to illustrate its application.