摘要:实际的控制系统,有一个饱和特性。当控制变量达到某一值时,系统的输出变量不再生长时,系统进入饱和区。这就要求系统的控制变量,必须限制在一定范围内,有时会是有限的控制量的变化率。
e system to decreased stability , dynamic response slower. Integral action often combined with the other two regulation law , composition PI regulator or PID regulator .
Differential (D) control: differential control , the controller output and input error signal differential ( ie, the error rate of change ) is proportional to the relationship . Automatic control system to overcome the error in the adjustment process oscillation may occur even instability . The reason is due to a larger inertia components ( links ) or with a lag (delay) component , can inhibit the effect of the error , the change is always behind the change of the error . The solution is to change the role of suppressing error "ahead ", that the error approaches zero , the role of inhibition of error should be zero . That is, the controller only the introduction of the " ratio " item is often not enough , the proportional term is only used amplified magnitude of the error , and the current need to increase the "Item" , the prediction error can trends , so , a proportional + differential controller , the error can be suppressed in advance the control action is zero , or even negative , thus avoiding a serious overshoot amount charged . So have a greater inertia or lag controlled object , proportional + derivative (PD) controller can improve the system in the regulation of the process dynamics.
Differential regulation : Differential effects reflect the rate of change of the error signal system , with foresight , to anticipate trends deviation , thus generating a control lead role in the deviation has not yet formed, the differential regulation has been eliminated. Therefore, it can improve the dynamic performance. In the differential time choosing the right circumstances, can reduce overshoot, reduce regulation time . Differential effects on noise disturbance amplification, so too strong plus differential regulation of anti-jamming disadvantage. In addition , differential response is change rate, and when the input does not change, the differential output is zero effect . Derivative action can not be used alone , you need to adjust the laws of the other two combined to form PD or PID controllers
PID controller parameter tuning of the control system design of the core content. It is based on the characteristics of the controlled process to determine PID controller proportional coefficient , integral time and derivative time size. PID controller parameter tuning in many ways, summed up in two categories : First, theoretical calculations entire titration . It is mainly based on the mathematical model of the system , through theoretical calculations to determine the controller parameters. This method of calculation of the resulting data may not be directly used , it must be adjusted by means of engineering and modifications . Second, the tuning method works , it mainly relies on engineering experience directly in the control system for the test , and the method is simple, easy to grasp, in engineering practice is widely used.
PID controller tuning method works , mainly the critical ratio , reaction and decay curve method . Three methods have their own characteristics , the common denominator is through testing , and then follow the empirical formula works tuning the controller parameters . But no matter which method the resulting controller parameters are required in the actual operation
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