For certain control systems, it is necessary to readjust some instruments in the closed loop circuit periodically. In this case, a sampling control system in which the plant is controlled continuously by the PI(D) controller at the interval (T-h) and controlled by the hold element at the other interval (h) as shown Fig. 1 and 2, must be investigated.
Corresponding to the system performance index Q which is given as the integral of squared error, this report graphically gives the functional relationship of Q to the system parameters, (T-h)/T, L (plant dead time), k_c and T_c (controller's gain and integral time) by using analogcomputation. Fig. 5∼Fig. 7 are the main results of this report and give contour lines of Q with respect to the above mentioned parameters.
By using these graphs, the proposed system can be synthesized almost perfectly in the case of T/T_p (T_p is the plant time constant) is equal and nearly equal to 1/10. In addition, Fig. 8 shows that there are interesting cases in which the proposed system is superior to the continuous control system.