7/15/2013 7:57 AM | |
Posts: 39 Rating: (9) |
Hello, What Is PID Controller & How it is work? |
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7/15/2013 8:44 AM | |
Joined: 3/18/2008 Last visit: 12/8/2023 Posts: 1750 Rating: (272) |
The WIKI says following: A proportional-integral-derivative controller (PID controller) is a generic control loop feedback mechanism (controller) widely used in industrial control systems. A PID controller calculates an "error" value as the difference between a measured process variable and a desired setpoint. The controller attempts to minimize the error by adjusting the process control inputs. The PID controller calculation algorithm involves three separate constant parameters, and is accordingly sometimes called three-term control: the proportional, the integral and derivative values, denoted P, I, and D. Simply put, these values can be interpreted in terms of time: P depends on the present error, I on the accumulation of past errors, and D is a prediction of future errors, based on current rate of change.The weighted sum of these three actions is used to adjust the process via a control element such as the position of a control valve, a damper, or the power supplied to a heating element. In the absence of knowledge of the underlying process, a PID controller has historically been considered to be the best controller.By tuning the three parameters in the PID controller algorithm, the controller can provide control action designed for specific process requirements. The response of the controller can be described in terms of the responsiveness of the controller to an error, the degree to which the controller overshoots the setpoint, and the degree of system oscillation. Note that the use of the PID algorithm for control does not guarantee optimal control of the system or system stability. Some applications may require using only one or two actions to provide the appropriate system control. This is achieved by setting the other parameters to zero. A PID controller will be called a PI, PD, P or I controller in the absence of the respective control actions. PI controllers are fairly common, since derivative action is sensitive to measurement noise, whereas the absence of an integral term may prevent the system from reaching its target value due to the control action. The PID control scheme is named after its three correcting terms, whose sum constitutes the manipulated variable (MV). The proportional, integral, and derivative terms are summed to calculate the output of the PID controller. Defining as the controller output, the final form of the PID algorithm is: where
The proportional term produces an output value that is proportional to the current error value. The proportional response can be adjusted by multiplying the error by a constant Kp, called the proportional gain constant. The proportional term is given by: DroopBecause a non-zero error is required to drive it, a proportional controller generally operates with a steady-state error, referred to as droop.[note 1] Droop is proportional to the process gain and inversely proportional to proportional gain. Droop may be mitigated by adding a compensating bias term to the setpoint or output, or corrected dynamically by adding an integral term. The contribution from the integral term is proportional to both the magnitude of the error and the duration of the error. The integral in a PID controller is the sum of the instantaneous error over time and gives the accumulated offset that should have been corrected previously. The accumulated error is then multiplied by the integral gain () and added to the controller output. The integral term is given by: The integral term accelerates the movement of the process towards setpoint and eliminates the residual steady-state error that occurs with a pure proportional controller. However, since the integral term responds to accumulated errors from the past, it can cause the present value to overshoot the setpoint value (see the section on loop tuning). The derivative of the process error is calculated by determining the slope of the error over time and multiplying this rate of change by the derivative gain Kd. The magnitude of the contribution of the derivative term to the overall control action is termed the derivative gain, Kd. The derivative term is given by: Hope you will go through this basic of PID which explains basic of PID irrespective of PLC. |
VANDE MATARAM..... |
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This contribution was helpful to3 thankful Users |
7/15/2013 9:35 AM | |
Joined: 4/20/2007 Last visit: 9/19/2024 Posts: 727 Rating: (43) |
LMGTFY |
This contribution was helpful to3 thankful Users |
7/15/2013 11:20 AM | |
Posts: 39 Rating: (9) |
thanx Amit |
7/15/2013 8:45 PM |
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Posts: 95 Rating: (10) |
hi check this link /tf/WW/en/Posts/74506#top |
Last edited by: muffi at: 7/15/2013 8:46 PM |
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7/16/2013 5:57 AM | |
Joined: 10/19/2012 Last visit: 4/17/2022 Posts: 315 Rating: (9) |
You want to learn the theory or your are talking about FB in STEP7? |
7/16/2013 7:53 AM | |
Posts: 621 Rating: (10) |
Hello in this thread hdhoseini link see that.
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