Showing papers on "Damping torque published in 1977"

Vibration damper for a torque converter lock-up clutch

Abstract: A vibration damper for a torque converter lock-up clutch wherein a wide angle of relative movement between the input and output members of the clutch is provided. The damper has radially spaced, staged resilient members disposed in parallel torque transmitting relation between stages in a manner to permit the primary stage only to transmit torque during a predetermined amount of relative angular movement and permit the secondary stage to pick up torque transmission for further predetermined relative angular movements.

Unifying approach to the static torque of stepping-motor structures

Abstract: Important stepping-motor structures are compared and their logical relationship to a basic doubly-salient machine is demonstrated. This leads to a single expression for holding torque, applicable to the majority of motors, comprising a product of the following terms: (a) a theoretical limiting mean torque, (b) a factor allowing for finite excitation, (c) the fraction of rotor volume effectively utilised on any one step, (d) a shape factor for the torque/angle curve. The analysis is cast in dimensionless form, both in respect of component terms in the torque expression and of motor variables. In particular, a critical value of m.m.f., calculable from gap geometry, is shown to be the significant unit of applied excitation. Advantages offered by this approach are quick calculation, a ready means of comparing different motors and insight into physical behaviour. Sample calculations are presented for a variety of motors and several individual problems discussed. Support for the theory is also provided by a range of experimental work and an appraisal of commercial data.

Feedback control for reduction of cogging torque in controlled current AC motor drives

Abstract: A decogging feedback control for current source inverter motor drives uses a change of instantaneous torque feedback signal with no dc component that is a function of only the instantaneous pulsating component of measured torque. The change of torque signal modulates the voltage applied to the dc link and therefore the dc link current to materially reduce the detrimental cogging torque pulsations and stabilize the motor, and can be switched out at a low frequency above which it is not needed so that the motor can respond properly to rapid variations in torque.

Mathematical Model of the Torque Characteristics for Hydraulic Motors

Abstract: In the mathematical model described in this paper, the following friction components are considered: (1) friction torque proportional to operating pressure, (2) viscous friction torque proportional to rotational speed and viscosity of fluid and (3) constant friction torque independent of operating conditions. The friction component which is proportional to operating pressure decreases with an increase of the rotational speed. This effect is also considered in this model. Therefore this mode can represent the whole torque performance from start to maximum speed.

Torque limiting drive with slip monitor

Abstract: A vehicle includes drive wheels and a motor connected thereto with torque controlling apparatus and a slip indicating device. Excessive slip indications per unit time are monitored and cause reduction in the torque applied by the motor until the slipping is overcome at which time torque is gradually increased.

Mechanisms of damping

Abstract: Bridges subjected to dynamic testing have commonly shown relatively small variation of damping (expressed as the effective instantaneous logarithmic decrement) with amplitude This is clearly closer to the theoretical solution for viscous or idealised hysteretic damping than to the solution of the classic simple friction-damped system Nevertherless, the magnitude of the observed damping is such that in many cases friction must make a major contribution to the dissipation of the energy of oscillation Some indication is given of the possible magnitude of hysteretic effects, including cases where an apparently hysteretic behaviour arises although the actual dissipative mechanism is frictional To assist understanding of the way practical factors modify the classic friction damping model, the results are presented of an extended analysis of the effect of friction in more complex system /Author/

Quality checking system for a threaded fastener assembly

Abstract: A method for measuring the relationship between the angle of rotation of a threaded fastener and the torque applied to the threaded fastener and for detecting variations in the rate of increase of torque with respect to the corresponding angular displacement of the fastener within predetermined torque limits, the first torque limit being the lowest threshold torque that is experienced as the threaded fastener is tightened, the next higher torque limit being a calibrated starting point torque intermediate the lower torque limits for the zone of the desired maximum torque values for the fastener and the threshold torque, the next two higher torque limits defining the torque zone representing the desired maximum torque to be applied to the fastener to assure a quality assembly.

The Damping Characteristics of Vibration Isolators Used in Gas Turbines

Abstract: The linear and nonlinear damping performance of a common type of gas-turbine vibration isolator, consisting of a squeeze-film journal bearing in parallel with a linear retainer spring, is computed and used to prescribe limits to the use of linear damping coefficients.

Torque control system for wind energy conversion devices

Abstract: Automatic torque control of wind energy conversion devices is provided through the utilization of turbine reaction torque. In the preferred embodiment, the frame of the driven machine is arranged to be rotatable through a limited angle. As rated torque of the system is exceeded, a force proportional to the turbine reaction torque is exerted by said frame to adjust the turbine aerodynamic configuration in such a manner as to reduce the torque error to substantially zero.

On the damping decrement for non-linear oscillations

Abstract: The logarithmic damping decrement is obtained as a function of arbitrary non-linear restoring forces and arbitrary, but small, non-linear damping forces. General expressions are obtained for both amplitude-dependent and speed-dependent damping. The special case of a cubic restoring force with quadratic amplitude-dependent damping and the special case of a cubic restoring force with quadratic speed-dependent damping are considered in detail. The results of the analysis suggest how experimental data can be utilized to identify and evaluate the damping parameters for a given non-linear oscillator.

Counting device impulse activator with torque limiter

Abstract: This invention comprises an actuator for a mechanical counting device for cording and storing data. This actuator includes a weight having an eccentric center of mass which is freely pivotable in one plane within pre-set limits in response to an externally applied impulse force of a predetermined magnitude to apply a torque force within prescribed limits to a shaft which, upon rotation thereof under the influence of such torque force, actuates the counter mechanism to record a count. Means are provided to apply counter torque force of a constant predetermined magnitude to the shaft, so that the counter is actuated only in response to a resultant torque force of a predetermined magnitude generated by the impulse. Torque limiting means are also provided to permit operation of the counter within an impulse band or range greater than the band or range achievable without use of such torque limiting means.

Torque reaction motor performance evaluation

Abstract: A torque reaction test system for evaluating the performance characteristics of a test motor by detecting its inertial reaction torque to acceleration and deceleration of the rotor. In one embodiment a test motor, typically at a final assembly stage and contained within a housing where it is inaccessible, is mounted in a rotatable fixture and the torque reaction of the test motor when accelerated and decelerated is obtained. The torque reaction is plotted against time or speed. A torque balance loop provides a feedback current which maintains the test motor housing within the fixture at a predetermined point of rotation and which provides an indication of torque reaction. A further embodiment provides a dynamometer in which a test motor is driven by a drive motor for a rapid run-up time and the torque response characteristics are plotted as a function of time or speed to provide nondestructive determination of system parameters.

Vibration damping system for high yield speed centrifuges - having both electromagnetic and mechanical damping components

Abstract: Rotor motion of high speed centrifuges is stabilised by a damping system. There is no mechanical connection between the rotor and its surroundings and the restraining force necessary to maintain the rotor on its rotational axis is provided by means of magnetic forces. The damping system is provided partly or completely by mechanical, hydraulic or hydropneumatic forces acting on the rotor. This damping functions partly or completely through a damping/bearing system mechanically connected to the rotor and which rotates with it but has no mechanical connection to the surroundings. A ring of solid material rotates with the rotor and is connected to it by a series of springs and wires to form flexible connections. This permits motion relative to the rotor and the vibration is damped hydraulically, hydropneumatically or by eddy currents. For use on high speed centrifuges operating at >=1000 revolutions per second above in which the rotor has velocities of 500 m/s or over. The problems with existing systems (a) for effective magnetic damping it is not always possible to keep the physical gap close enough for magnetic forces to be effective (b) the stabilising forces being too low, the damping to poor (c) further variation the stabilising forces occurs if the gap increases due to elastic deformation of the rotor. The system overcomes these problems.

Controlling method of elevator

Abstract: PURPOSE:To provide a method of regulating an elevator in such a manner that a damping torque is produced after a residual voltage may not be produced.

Pairwise analysis of dynamic stability in large power systems

Abstract: The method suggested involves computation of synchronizing and damping torque coefficients of oscillating generators selected in pairs in a large interconnected system and the use of these values to construct a model to represent the dynamics of the entire system. This method, shown to give acceptable results, saves a considerable amount of storage space and computation time.