TORSIONAL VIBRATION SIMULATION USING A UNIVERSAL
JOINT
Zhuang Li, Mohsen Nakhaeinejad, Suri Ganeriwala
SpectraQuest Inc., 8201 Hermitage Road, Richmond, VA 23228
Published: Jan 2009
Abstract
A universal joint is a mechanical device which
can transmit torque and rotational motion of two intersecting
shafts. The joint consists of a pair of yokes oriented at 90°
relative to each other. The two yokes are called the driving and
driven yokes. This document introduces the basic theory of the speed
variation caused by a universal joint. Measurements were conducted
using SpectraQuest Torsional Vibration Calibrator. Conclusions can
be drawn from both the theoretical and experimental analyses. A
non-zero joint angle of a universal joint causes the output shaft
speed varies with an averaged speed the same as the input speed. It
is used to simulate the torsional vibration of the output shaft.
The amplitude of the speed variation increases with the joint angle,
and is linearly proportional to the averaged speed. The angular
variation, however, only depends on the joint angle, but is not a
function of the angular speed.
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Introduction
A universal joint is a mechanical device which can transmit torque
and rotational motion of two intersecting shafts. The joint consists
of a pair of yokes oriented at 90° relative to each other. The two
yokes are called the driving and driven yokes.
Experiments were carried out on
the SpectraQuest Torsional Vibration Calibrator (TVC), shown in Fig.
2. The TVC is driven by a 3-HP motor whose speed is controlled by a
VFD. A flywheel is used to stabilize the input shaft speed. The
input and output shafts are connected using a Cardan universal
joint, where the joint angle can be adjusted. A series of holes on
the base plate allow users to adjust the joint angle from -20° to
+20° with an increment of 2.5°.
The angular speed of the output
shaft was measured using a 1024-pulse encoder. The encoder output
was connected to one of the counter/timer channels on the National
Instrument PCI 6221 data acquisition board. The time base and size
of the counter/timer are 80 MHz and 32-bit, respectively. The
counter/timer recorded the time of occurrence each pulse.
Calculating the time variance of the time intervals between pulses
gives the angular speed variation of the output shaft.
Three joint angles were tests: 5°,
10°, and 15°. At each joint angle, the encoder data were collected
at different running speeds.
Fig 1: Cardan universal joint
Fig 2: Torsional Vibration Calibrator
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