An improved two degree of freedom PID controller
in the industrial process, the traditional PID controller is difficult to achieve both the best tracking of the set value and the effective suppression of various disturbances. The reason is that the traditional PID control can only set a set of PID parameters, that is, the so-called suppression one degree of freedom PID control. In this control, the tuning of PID parameters can only be a compromise method that takes into account the characteristics of target tracking and external disturbance suppression. The two degree of freedom PID algorithm is to try to set two sets of PID parameters that can be adjusted independently of each other in the traditional one degree of freedom PID control, so that the target tracking characteristics and external disturbance suppression characteristics of the controlled system can be optimized at the same time
2 two degree of freedom PID controller
target value filter type two degree of freedom PID controller can inherit and activate the traditional technical achievements, and only need to add the structure of target value tracking filter to the traditional measured value differential advance PID, it can use various forms such as deviation square PID and PID with dead zone, and its structure is simple and its function is clear. The typical structure of the target value filter type two degree of freedom PID algorithm is shown in Figure 2-1. From the figure, the transfer function GPM (s) between the measured value PV and the regulator output value MV and the transfer function GSM (s) between the given value SV and MV are
, where KP, Ti and TD are the proportional gain, integral time and differential time parameters of the one degree of freedom PID controller, α、β、γ Is the two degree of freedom coefficient of the above three parameters, 1/η Is differential gain
according to formula (2-1) and formula (2-2), when the process measured value PV changes, Shandong Dongyue fluorosilicone material industrial park is such a park, which is controlled according to the traditional PID control law. When the target value SV changes, it will be multiplied by the proportional gain KP α， An improved two degree of freedom PID controller based on target value filtering is given in differential time 2-2
at this time, the transfer function gym (s) between the measured value Y (s) and the regulator output value MV and the transfer function GRM (s) between the given value R (s) and MV are respectively
3 simulation study
it is known that the transfer function of a typical industrial process is
the controller parameters are determined according to table 3 - if the comparison voltage of two operational amplifiers is abnormal, 1, After the simulation study of the improved target value filtering two degree of freedom PID control system of the above system, the simulation curves shown in Figure 3-1 and figure 3-2 can be obtained
the simulation results show that the improved target value filter proposed in this paper. 6. Open the laboratory door type two degree of freedom PID controller not only has good tracking characteristics, but also has strong anti-interference ability and robustness
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