PC BASED EXCITATION AND INSTRUMENTATION SYSTEM FOR VIBRATOR

Abstract

Vibration test is one of the enviornmental tests specified in the testing of industrial products like meters, RTDs etc. All relevant standards specify an antilogarithmic sweep rate with a variation in the ranges, of frequency for each standard.The standards also specify a definite peak to peak displacement and acceleration to be maintained constant for different ranges of frequency.These also differ from standard to standard.Vibrator, on which the unit under test is placed,has a responce which varies with frequency and weight placed on it.Hence,as expected, displacement and acceleration of vibrations generated by vibrator also change.The purpose of this work is to generate the desired excitation ,i.e a signal having an antilogarithmic frequency sweep rate over a definite range. Then provide the necessary instumentation and feedback control to fulfil the requirements of constant displacement and acceleration over specific frequency ranges. Displacement has been monitered with the help of LVDT and acceleration with the help of accelerometer. For controlling the displacement and acceleration to a constant value, proportional-integral-derivative control (PID)action has been used. The gains of various control actions are optimized experimentally. Inthis work,it is assumed that the wave shape of vibrations is sinusoidal. The PID control action is giving satisfactory results.