Effect Of Coulomb Friction Research Articles

The steady state response of a servosystem taking stiction and coulomb friction into consideration

The effects of stiction and coulomb friction on the steady state response of a servosystem are studied, by using a simple friction characteristic. It is shown that the gain characteristic has the same form as that of a first order linear system except in the case where the ratio of stiction to the input torque amplitude is very close to unity. It is also shown that the phase angle at high frequencies aproaches a value less than 90°, thus improving the system stability.

Analysis of Two-Dimensional Motion Resisted by Coulomb Friction

The effect of Coulomb (dry) friction between surfaces of adjacent machine members, either in preventing relative sliding motion or in absorbing energy when relative motion does occur, has traditionally been analyzed on a one-dimensional basis. The two-dimensional analysis presented in this paper shows how the effectiveness of Coulomb friction in preventing relative sliding motion is greatly reduced by eccentric loading, and how the effectiveness of Coulomb friction in absorbing the energy of an oscillation may be greatly reduced by the addition of a second oscillatory or unidirectional motion. The results of the analysis are correlated with experimental data.

Effect of Coulomb Friction on the Forced Vibration of a System with Elastically Supported Viscous Damper

The analysis on the forced vibration of a system with elastically supported viscous damper whose damping is accompanied by the Coulomb friction is a very complicated one, for the reason that its every cycle is composed of two different kinds of motions and that seven boundary conditions are needed to solve it. In this paper, the author presents certain characters of the vibration of a system with optimum damping and Coulomb friction, the calculation of which is carried out by a digital computer. It became clear from the results of the analysis and the experiments that, while the Coulomb friction is smaller than the disturbing force, the amplitude seems to grow larger continuously from infinite damping curve to the optimum damping one as the frequency increases, but in the case where the friction overcomes the disturbing force, a jumping phenomenon of the amplitude occurs at a fixed place corresponding to the amount of friction.

Effect of Coulomb Friction on the Vibrations of a System with Elastically Supported Viscous Damper : 1st Report, Free and Transient Vibrations

In this report, the effect of Coulomb friction brought about from the packing gland of the damper on the free and transient vibrations of the above system is considered with respect to some numerical examples. The result shows (1) that a cycle of free vibration consits of two motions, one the motion when the friction is infinite and the other the motion with combined Coulomb friction and viscous damping, and (2) that the transient state while the system runs over a bump (shaped like a portion of sinusoidal curve) is regarded as a chain of fragmentary pieces of the two kinds of motion stated above. The existence of the motion when the damper is momentarily stuck-up gives a negative effect on the diminishing of the amplitude of the free-vibration of the system, but comparing the transient states with those of the system with no friction, a larger decrement of the amplitude of the initial response may occur in some cases according to the combination of the magnitude of friction, height of projection and the passing speed over it.

Effect of Coulomb Friction on the Vibrations of a System with Elastically Supported Viscous Damper : 2nd Report, Forced Vibration

The analysis on the forced vibration of the system with elastically supported viscous damper whose damping is accompanied by the Coulomb friction is a very complicated one, for the reason that its every cycle is composed of two different kinds of motion as stated in the 1st report and that seven boundary conditions are needed to solve it. In this paper, the author presents certain characters of the vibration of the system with optimum damping and Coulomb friction, the calculation of which is carried out by a digital computer. It became clear from the results of the analysis and the experiments that, while the Coulomb friction is smaller than the disturbing force, the amplitude seems to grow larger continuously from infinite damping curve to the optimum damping one as the frequency increase, but in the caee where the friction overcomes the disturbing force, the jumping phenomenon of the amplitude occurs at a fixed place corresponding to the amount of friction.

Describing functions representing the effect of inertia, backlash, and coulomb friction on the stability of an automatic control system - I

A first study is presented of the effect of backlash and coulomb friction upon the stability of an automatic feedback control system. The system consists of a mechanical linkage in which the load member is subjected to a restraining force. Describing functions that represent the load response for finite values of inertia, backlash, and coulomb friction between the load and an external surface are derived analytically. An example illustrates the conditions under which nonlinearities cause sustained oscillations in a given system, and how the Nyquist criterion can be used to obtain frequency and amplitude of the oscillations.

The effect of coulomb friction in the planestrain compression of a plastic-rigid material

The plane-strain compression of a plastic-rigid material is analysed on the assumption that the frictional conditions between the platens and the material aie such that the shear stress is the same fraction of the normal stress everywhere on the platen surface,unless this value attains the yield shear stress of the metal, which it can never exceed. This is the condition known as Coulomb friction, the ratio being defined as the coefficient of friction μ. The solution has been determined by a geometrical method recently proposed by Prager (1958) for integral ratios of platen breadth/material thickness of 7 and 3, and for values of the coefficient of friction of 0.05, 0.1, 0.15, 0.225, 0.8 and the limiting value of 1 1+ 1 2 π , above which value the yield shear stress is always attained along the complete zone of contact. Comparison is made with an approximate theory in which the state of stress is assumed constant across any section. A simple test is described by means of which the coefficient of friction for material being deformed under plane strain conditions may be determined.

Effects of friction in an optimum relay servomechanism

A recently proposed relay servo-mechanism employs maximum torque at all times, with the sense of the torque determined by a comparison of the error and the square of the error rate. With correct switching and no friction, this system gives the minimum possible response time for a step input with the specified inertia and maximum torque. A theoretical study of the effects of Coulomb or viscous friction is described in this paper. The degradation of the step-function response as a result of friction is measured by the change in response time, integrated absolute error, and integrated squared error. It is found that moderate amounts of friction can be tolerated with only a small loss in performance, if a slight change is made in the switching device.

The effect of friction on the behaviour of servo mechanisms at creep speeds

Position-control servo mechanisms are frequently required to operate smoothly through a very wide range of speeds; the limitation to smooth running at creep speeds is invariably imposed by the non-linear friction in the bearings, gears, etc., associated with the output shaft. The object of the paper is to outline two methods of investigating the effects of static and Coulomb friction on the minimum smooth-running speed of a position-control system. The first method follows closely some recent work on non-linear mechanics and is particularly suited to the non-linear friction problem because it provides a qualitative picture of the behaviour of a system; the method has been applied to a simple mechanical filter-system. The second method uses the differential analyser to solve the non-linear differential equations describing the behaviour of the system. The use of the differential analyser for this problem presents some interesting features, and the running procedure of the machine for the case of the mechanical filter has been described in some detail.Some results are presented which were obtained with the differential analyser in connection with the behaviour of a typical automaticfollowing radar servo-system incorporating a metadyne-controlled motor at creep speeds. It is pointed out that, notwithstanding the rather special and complex nature of the system for this example, it is probable that the general nature of the results will not differ appreciably when other systems are used.

The Effect of Coulomb Friction on the Performance of Servomechanisms

The Effect of Coulomb Friction on the Performance of Servomechanisms

Dynamic Behavior and Design of Servomechanisms

Abstract This paper aims to set forth the criteria that are important in the design of certain servomechanisms and to show how certain analytical procedures can be applied to almost any problem to define quantitatively the properties that the control should have in order to make the servomechanism perform in the manner desired. The nomenclature used is essentially that proposed by Draper (1). It is used in the treatment of the problem of synthesizing a controller for a servomechanism whose controlled member is to be rotated and can be defined in terms of inertia plus viscous and coulomb friction, plus a load torque. The broad objective of the designer is assumed to be that of designing a controller which will keep the dynamic error in controlled angular position of the controlled member a minimum under certain operating conditions. The transient and steady-state error for certain forms of motion, the criteria for stability, the effects of viscous friction, coulomb friction and load torques on the desired performance, and other related matters are treated. Several nondimensional charts and tables are included in the paper and show quantitatively the performance of any particular servomechanism with a controlled member of the kind treated, when the system has the various forms of control.