Showing papers on "Damping torque published in 1971"

Torque Pulsations in Induction Motors with Inverter Drives

Abstract: Torque pulsations in induction motors would have an average value of zero and therefore are generally neglected by inverter induction machine system designs. A simple equivalent circuit method is presented for estimating the magnitude of torque fluctuations under steady-state operating conditions based on single-phase equivalent circuits. The method indicates that torque fluctuations are due mainly to the interaction of fundamental flux in the air gap at harmonic rotor currents. Inverters producing a 6-stepped voltage waveform, the predominant pulsating torque is at the sixth harmonic and the magnitude of the fluctuation is independent of operating frequency, provided that constant volts per Hz is maintained. The method is extendable to PWM inverter-machine systems with similar conclusions with respect to variation of torque over the input frequency range. However, for the PWM inverter with a fixed number of pulses per cycle, the torque pulsations can approach or exceed full-load average torque. The method outlined is simple and amenable to hand calculations.

Influence of damping in vibration isolation

Abstract: : ;Contents: Introduction; Vibration isolation with viscous damping; Vibration isolation with coulomb damping; Vibration isolation with quadratic damping; Vibration isolation with velocity-nth power damping; Vibration isolation with hysteretic damping; Vibration isolation with combined viscous and coulomb damping.

Vibration damper test machine

Abstract: A vibration damper test machine including a rotary mass elastic system and characterized by electromagnetic means for exciting the system in the form of an oscillating torque of resonant frequency to produce large torsional vibrations at an end of the system adapted to receive a torsional vibration damper. The electromagnetic excitation means is arranged such that an excitation frequency corresponding to a predetermined order of vibration and an excitation torque corresponding to the order of vibration amplitude can be induced into the mass elastic system to simulate conditions existing in a particular engine. An observed excessive amount of strain on the system at resonance provides an indication of malfunction of the damper.

Electronic torque measurement system

Abstract: A wrenching and torque inspection apparatus including a rotary power wrench having its housing fixed to a support by a resilient member forming part of an electronic torque measuring system for measuring the reaction torque load on the wrench housing. The torque measurement signal is used to operate an indicator, such as a light, recorder and may be used to stop the wrench at a predetermined value of torque.

Step motor damping method and apparatus

Abstract: A step motor damping apparatus and method which provide electrical damping of the step motor motion. A damping control signal is derived from the electromotive force induced in certain stator pole windings of the step motor by the moving motor armature. A damping force on the armature is produced by energizing the same or other motor poles in response to the damping signal.

Ship rolling at zero speed in random beam seas with nonlinear damping and restoration

Abstract: A theoretical method is developed for estimating the root-mean-square of nonlinear roll for surface ships at zero speed under the influence of random beam seas. The nonlinearities considered include both "square'law" damping and a "Duffing-type" stiffness. An explicit relationship is derived for the rms nonlinear roll in terms of the linear roll variance and the ratios of nonlinear to linear damping and restoration coefficients. The method is illustrated by two examples stemming from earlier studies of similar problems.

Temperature compensated adjustable damper unit

Abstract: An adjustable damper unit is provided which exerts a restraining torque on a shaft, the torque being directly proportional to the angular velocity of the shaft. Damping is provided by a magnetic restraint on a drag cup driven through the magnetic field of a permanent magnet by planetary gears. An external adjusting ring controls the magnitude of the magnetic restraint and thereby controls the damping rate.

Control moment gyroscope with integral torque control

Abstract: A vehicle control mounted moment gryoscopic apparatus which employs a closed loop torque feedback system and includes a gyroscopic rotor disposed within a shell-like housing. The rim of the shell-like housing functions as the inner gimbal assembly and is coupled to a half-ring cantilevered middle gimbal assembly. The middle gimbal assembly is connected through a spindle to a flexure plate within a base gimbal assembly. Torque sensors are affixed to the flexure plate and provide torque feedback signals in accordance with the magnitude of the actual torques applied between the vehicle and the gyroscopic apparatus. The torque feedback signals are combined in a summing device with torque command signals to produce differential torque signals proportional to the difference between the torque command signals and the applied torque signals. Control law circuits translate the differential torque signals into controlled torque signals that are applied to torquers which drive the inner and middle gimbal assemblies in a direction that provides a substantial reduction in the magnitude of the differential torque signals.

Variable Parameter Nutation Damper for SAS-A

Abstract: This paper presents design objectives, functional description and in-flight performance of a variable parameter nutation damper for a dual-spin satellite. The damper consists of a torsion wire mounted pendulum which includes the capability of command changing the pendulum resonant frequency and damping constant in order to obtain optimum spin axis stabilization for both a dual-spin and single-spin spacecraft dynamical condition. State-of-theart features of this damper include: 1) taut-band suspension, for a pendulous mass, which has no mechanical friction of hysteresis, 2) magnetic circuit for changing the torque constant of the taut-band thereby changing the damper natural frequency, 3) chargeable magnet system for varying the damping coefficient, and 4) 7-bit optical readout for telemetering the damper motion. The damper weights 2.7 Ib and draws 20 mw power when functioning for dual-spin conditions. The minimum nutation damping time constant in this mode is 12 min with a predicted spin axis pointing accuracy of 1 min of arc. Stabilization to better than 2 min of arc has been achieved in orbit.

Torque testing screwdriver with automatic torque indicating means

Abstract: A torque-testing screwdriver is disclosed which includes a blade, a handle, a spring for transmitting torque from the handle to the blade, a scale for indicating the amount of torque transmitted from the handle to the blade, and an indicating contact which continuously enables a signal device during the torque test and which automatically positions itself opposite the scale reading representing the maximum resistive torque exerted by the screw under test.

Engine torque control system

Abstract: The engine horsepower is computed as a function of the engine fuel flow rate and the engine torque is derived by the division of the horsepower signal by a signal functionally related to the engine speed. The actual torque of the engine is compared to a torque set point and upon a given deviation from the set point, corrective signals are actuated to return the actual torque to its set point. Upon too great a deviation, an alarm is actuated and the engine is completely unloaded. When used with ambient uprated engines, a temperature signal representing engine capability is used to limit the torque set point to its maximum allowable setting. Upon loss of the signal representing engine capability, the allowable torque is reduced as though there were no up-rating of the engine. The fuel flow computer utilizes signals from the differential pressure of the fuel, the static pressure of the fuel and the temperature of the fuel to produce a signal indicative of the square root of the product of the two pressure parameters divided by a signal functionally related to the fuel temperature.

Analysis of M125 Booster Mechanism

Abstract: : A mathematical analysis of the M125 booster safety and arming mechanism is presented It provides a better insight into the mode of operation of the M125 and the effect of certain design parameter variations on the mechanism's performance This analysis was made in support of product improvement efforts on the S and A device for the M514A1E1 artillery proximity fuze Equations of motion involving 33 design and operating parameters of the mechanism and both phases of the rotor's movement are developed and discussed In developing an expression for the damping torque due to escapement action, it is assumed that the rotor's angular velocity is proportional to the square root of the driving torque Computations for the damping coefficient are based on a prior detailed dynamic analysis of the escape wheel and pallet covering their six phases of motion per cycle The final equations of motion are nonlinear; digital simulation methods were therefore used for their solution Illustrated and discussed are time, rate, and turns-to-arm versus spin speed; also, displacement, velocity, and acceleration are considered as a function of time at high- and low-spin rates (100 and 30 rps)

A Mathematical Model for Predicting the Damping Time of a Mercury Damper

Abstract: : The mercury damper is a device for damping the nutation of a rotating body. This report explains how a mercury damper works, and derives a simple expression for the damping time.

Passive damping of the forced precession motion of a two-body satellite

Abstract: Two-body satellite of axisymmetric rigid bodies interconnected by lossy universal joint, calculating transient oscillation damping of forced precession under external torque