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Control Engineering - A guide for beginners - Chapter 4

Tham khảo tài liệu 'control engineering - a guide for beginners - chapter 4', kỹ thuật - công nghệ, tự động hoá phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 4 Control loops with continuous controllers 4.1 Operating methods for control loops with continuous controllers The previous chapters dealt with the individual elements of a control loop the process and the controller. Now we consider the interaction between these two elements in the closed control loop. Amongst other things the stable and unstable behavior of a control loop should be examined together with its response to setpoint changes and disturbances. In the section on Optimization we will come across the various criteria for adjusting the controller to the process. We also often refer to the static and dynamic behavior of the control loop. The static behavior of a control loop characterizes its steady state on completion of all dynamic transient effects i.e. its state long after any earlier disturbance or setpoint change. The dynamic behavior on the other hand shows the behavior of the control loop during changes i.e. the transition from one state of rest to another. We have already discussed this kind of dynamic behavior in Chapter 2 The process . When a controller is connected to a process we expect the process variable to follow a course like that shown in Fig. 42. Fig. 42 Transition of the process variable in the closed control loop JUMO FAS 525 Edition 02.04 63 4 Control loops with continuous controllers - After the control loop is closed the process variable x should reach and hold the predetermined setpoint w as quickly as possible without appreciable overshoot. In this context the run-up to a new setpoint value is also called the setpoint response. - After the start-up phase the process variable should maintain a steady value without any appreciable fluctuations i.e. the controller should have a stable effect on the process. - If a disturbance occurs in the process the controller should again be able to control it with the minimum possible overshoot and in a relatively short response time. This means that the controller should also exhibit a good .