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Temperature Control in Large Buildings
Published in William S. Levine, Control System Applications, 2018
Clifford C. Federspiel, John E. Seem
Several manual tuning and autotuning methods are based on the response to a step change in the controller output. Open-loop step tests should be run in the high-gain region of the process. Running the step test in the high-gain region helps ensure that the control system remains stable for other regions of operation. (The process gain is equal to the ratio of the steady-state change in the process output to the change in the controller output following a step change in the controller output). For systems with a large amount of hysteresis in the controlled device, the user should stroke the controlled device to reduce the effect of hysteresis on the step test. Figure 2.12 shows how to reduce the effect of hysteresis for a step change in the positive direction. Initially,the controller output should move in a negative direction. Then, the controller output should move in the positive direction until it is back to the initial position. The step change in controller output should take place after the process output returns to a nearly steady-state condition. A similar procedure should be used for a step change in the negative direction.
Practical Control of Nonlinear Processes
Published in Jose A. Romagnoli, Ahmet Palazoglu, Introduction to Process Control, 2020
Jose A. Romagnoli, Ahmet Palazoglu
We remember that for a linear (or linearized) process, the process gain reflects how much the output variable changes for a change in the input variable, that is, kp=ΔyΔu
Uncertainty analysis of transfer function of proton exchange membrane fuel cell and design of PI/PID controller for supply manifold pressure control
Published in Indian Chemical Engineer, 2019
Srinivasarao Divi, S. H. Sonawane, Shantanu Das
The reaction curve method is preferred because less effort is required to develop an approximated FOPTD model from highly complex system. The PEM Fuel cell control oriented model which is approximated to FOPTD model of general form is given by Seborg D. E. et al. [13]. The parameters of FOPTD model shown in Equation (11) are determined by the method proposed by Sundaresan. K. R. et al. [10].The parameters of FOPTD model are obtained by the following equationswhere and are the time when the responses are 35.3% and 85.3% of the final value respectively. The process gain is found by calculating the ratio of the steady state change in output to the size of the input step change.The open loop step response of the PEM fuel cell model is in the s-shaped curve and the FOPTD model parameters can be found from the Equations (12), (13) and (14) are as follows.