Clarifying PID control types~
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Hello, everyone! These past few days I’ve had some free time, so I studied PID control theory. However, while reviewing the IM documentation related to Yokogawa systems, I found that Yokogawa offers multiple approaches for PID control, with different parameters used in each approach, which is quite confusing. I hope everyone can help me understand this better! Yokogawa offers three types of PID control: 1. PID, 2. I-PD, 3. PI-D. 1.PID: the proportional term, integral term, and derivative term are all based on the error. (Deviation = Input value – Set value) 2.I-PD: The proportional term is the input value PV, the integral term is also the input value PV, and the derivative term is the deviation. 3.PI-D: The proportional term is the deviation, the integral term is the input value PV, and the derivative term is the deviation. What is the difference between these three control methods in practical applications? I tried to conduct simulations on the simulation system, but due to its extremely fast response time, it was almost impossible to observe any effects. I hope everyone can discuss this together. I’ve basically forgotten all the calculus I learned in college; it’s really difficult for me to understand the derivation formulas for PID now. I’m ashamed. . . . .
1.PID: Proportional term, integral term, derivative term – all are deviations. (Deviation = Input value – Set value) 2.I-PD: The proportional term is the input value PV, the integral term is also the input value PV, and the derivative term is the deviation. 3.PI-D: The proportional term is the deviation, the integral term is the input value PV, and the derivative term is the deviation. The normal description is as follows: the proportion is adjusted based on the magnitude of the deviation, integration is adjusted depending on whether there is a deviation, and differentiation is adjusted according to the rate of change of the deviation. In the three situations given as examples by the original poster, there are all instances where the rules are violated; how can this be explained? I’m also seeking an expert to provide an explanation. :)
Theoretically, that’s what it is, but that’s exactly what the Yokogawa system manual states. For different PID control types, the components of the proportional and integral terms vary, and this is what finds me strange. Also, could you explain the formula for PID? ? ? Looking at these formulas with calculus now, they’re completely incomprehensible. . . .
I don’t see the formula; I happen to want to learn it as well.
P-proportional control is the simplest form of control. The output of its controller is proportional to the input error signal. When only proportional control is used, there is a steady-state error in the system output. An automatic control system is considered to have a steady-state error, or simply a system with steady-state error, if there is a steady-state error after it reaches steady state. To eliminate steady-state error, an “integral term” must be introduced into the controller. The integral term corresponds to the time-integral of the error; as time increases, this integral term grows. In this way, even if the error is small, the integral term increases over time; it drives the output of the controller to increase, thereby further reducing the steady-state error until it becomes zero. Therefore, a proportional-plus-integral (PI) controller enables the system to have no steady-state error after reaching steady state. In the process of adjusting to overcome errors, motion control systems may experience oscillations or even instability. This is due to the presence of components with high inertia or those that introduce delay; such components serve to suppress errors, but their responses always lag behind the changes in the errors. The solution is to make the change in the error-suppression effect \"proactive\"; that is, when the error is close to zero, the error-suppression effect should be zero. In other words, it is often insufficient to introduce only the “proportional P” term in the controller; the role of the proportional term is merely to amplify the magnitude of the error. What is needed now is the “derivative term”, which can predict the trend of error changes. In this way, a controller with proportional + derivative control can bring the error-suppression control action to zero in advance, or even to a negative value, thereby preventing severe overshoot of the controlled variable. Therefore, for controlled objects with high inertia or lag, a Proportional P + Integral I + Derivative D (PID) controller can improve the dynamic characteristics of the system during the regulation process. If one has a solid foundation in mathematics, it is recommended that the original poster take a close look at this article: http://www.doc88.com/p-93841458969.html