IJSRP, Volume 5, Issue 1, January 2015 Edition [ISSN 2250-3153]
Christian C. Mbaocha, Lakpah Emmanuel A, Jonathan A. Emmanuel
In industrial applications, when considering the performance of Computer Numerical Control (CNC) machines, it is worthy to note that the dimensional accuracies as well as surface finishes of parts produced by the machine tool rely strongly on the accuracy of the motion that each axis of the machine.The overall accuracy of the CNC machine tool is determined by the mechanical characteristics of the machine as well as the characteristics of the control system driving the individual tool. To maintain the quality of the finished product, it is necessary to optimise and sustain the level of accuracy of the machine tools so that defective parts can be prevented in manufacturing. A CNC Machine is programmed to travel along a predetermined path, and any deviation from the programmed path would constitute an error. The purpose of this project is to design a three-term (Proportional, Integral, and Derivative) digital controller to optimally improve the movement and accuracy of the control valve in anelectro-hydraulic servo-valve control system used in a numerical machine tool control and to accurately position the machine tool in the desired location on the workpiece. The three-term controller is designed to improve the phase margin lower than 0.498o degree, less than 5 percent overshoot , a settling time below 0.0141 seconds and a rise time less than 5 seconds when subject to a unit step input, which reduces the damping ratio below 0.182.