Tham khảo tài liệu 'ogata - modern control engineering part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | The entire analysis in this section was made by using the two-degrees-of-freedom control system shown in Figure 10-20. As a matter of course the entire analysis here can be applied to one-degree-of-freedom control systems by assuming G c2 to be zero. Requirements on robust design in terms of the Bode diagram. It is possible to place conditions on the Bode diagram of the open-loop transfer function to satisfy the conditions imposed on sensitivity steady-state errors and sensor noise. The requirement on small 5 ct in low-frequency region specifies the minimum bound for low-frequency gain and the requirement on low sensor noise sensitivity to be small places an upper bound on the high-frequency gain. An acceptable Bode diagram of the open-loop transfer function is shown in Figure 10-22. The gain crossover frequency must be located near the required bandwidth and the slope of the magnitude curve at the gain crossover frequency must be -20 dB decade. Concluding comments. The ideas to evaluate the control system performance based on the sensitivity function Sịj ừ and complementary sensitivity function T jc j were developed during the mid 1970s and late 1980s. Such developments gave the old frequency-response methods a new modern look. Recent advances in -infinity control robust control and the like are based in part on the frequency-response approach. Figure 10-22 Requirements on robust design in the Bode diagram. dB a Small IGclGpl 1 EXAMPLE PROBLEMS AND SOLUTIONS A-10-1. Describe briefly the dynamic characteristics of the PI controller PD controller and PID con- troller. Solution. The PI controller is characterized by the transfer function Gc s Kp l -U Tisi The PI controller is a lag compensator. It possesses a zero at 5 ---1 T and a pole at s the characteristic of the PI controller is infinite gain at zero frequency. This improves the steadystate characteristics. However inclusion of the PI control action in the system increases the type number of the .
