الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The precision control of linear feed axes in machine tools is examined in this
thesis. As well as simulating the ball screw feed drive system and studying it′s
frequency response. Various parameters effect on the dynamic behavior of the ball screw system have been investigated. Ball screw feed drive system is used in high speed machine tools due to their high efficiency. Estimation of the dynamic behavior of ball screw feed drive mechanism is very important in the
industrial processes in order to get high demand for precision and accuracy in
machine tools. Optimizing the drive operation can provide significant cost
savings. The mathematical modeling provides an important information about
frequency response when applying different levels of table mass, stiffness of the
nut, axial stiffness of the ball screw shaft and torsional stiffness of the ball screw on the system, to describe the effects of these parameters on the system dynamic behavior. A four degree of freedom system, lumped parameter model is used for
modeling a single axis ball screw feed drive system and use it to study and
analyze vibrations in this model. The study of dynamic response of ball screw
feed drive system provides a better performance control and better understanding of ball screw dynamics.
The experimental setup consists of two subsystems, which are the mechanical
and electrical subsystem. The required components are used for the construction
of the ball screw feed drive system. There are many laboratory experiments that
have been conducted to study the effect of velocities and masses on the vibrations of the device. The position displacement measurements were performed to study the positioning accuracy of the device. The amplitudes of vibrations in the presence of looseness in the bolts have been discussed. The effect of velocity in the amplitude of vibration and the effect of varying masses on the frequency were performed as well. These different experiments were studied to analyze the effect of different factors on the device performance, as well as an attempt to control and reduce the vibration values.
Using the simulation of the system, it was found that by increasing the stiffness of the nut, the axial and torsional stiffness of the screw shaft, the value of the frequency increases, and therefore the vibration is controlled by the change
in the values of the natural frequencies of the system. A relationship between the
viscous damping coefficient of the guide way of the working table and the amplitude of vibration was carried out. Thus, the vibration value can be controlled by changing the damping value of the system.
Two encoders were used to determine the error in the linear motion that the table moves, and thus an open loop control circuit was made to determine the actual error in the linear motion. The experimental results of the device were
studied and used to deduce a relationship between velocity and vibration amplitude. Thus, this relationship can be used to reach a specific vibration value by changing the velocity of the device.
The highest velocity of the motor has the highest effect in errors of displacements. In general, in case of the presence of looseness in one bolt, the value of the amplitude of vibration decreased. In case of the presence of looseness in the three bolts and four bolts simultaneously. The damping effect became less and consequently the vibration amplitude of the system increased.