Offset Error In P Controller
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mechanical examples are the toilet bowl float proportioning valve and the fly-ball governor. The proportional control system is more complex than an on-off control system like proportional controller steady state error a bi-metallic domestic thermostat, but simpler than a proportional-integral-derivative (PID) control system
Proportional Controller Example
used in something like an automobile cruise control. On-off control will work where the overall system has a proportional offset definition relatively long response time, but can result in instability if the system being controlled has a rapid response time. Proportional control overcomes this by modulating the output to the controlling proportional only control offset device, such as a continuously variable valve. An analogy to on-off control is driving a car by applying either full power or no power and varying the duty cycle, to control speed. The power would be on until the target speed is reached, and then the power would be removed, so the car reduces speed. When the speed falls below
How Integral Controller Eliminates Offset
the target, with a certain hysteresis, full power would again be applied. It can be seen that this looks like pulse-width modulation, but would obviously result in poor control and large variations in speed. The more powerful the engine; the greater the instability, the heavier the car; the greater the stability. Stability may be expressed as correlating to the power-to-weight ratio of the vehicle. Proportional control is how most drivers control the speed of a car. If the car is at target speed and the speed increases slightly, the power is reduced slightly, or in proportion to the error (the actual versus target speed), so that the car reduces speed gradually and reaches the target point with very little, if any, "overshoot", so the result is much smoother control than on-off control. Further refinements like PID control would help compensate for additional variables like hills, where the amount of power needed for a given speed change would vary. This would be accounted for by the integral function of the PID control. Contents 1 Proportional Control Theory 2 Offset Error
mechanical examples are the toilet bowl float proportioning valve and the fly-ball governor. The proportional control system is more complex than integral action in a proportional integral controller an on-off control system like a bi-metallic domestic thermostat, but proportional controller pdf simpler than a proportional-integral-derivative (PID) control system used in something like an automobile cruise control. On-off control
Proportional Control Theory
will work where the overall system has a relatively long response time, but can result in instability if the system being controlled has a rapid response time. https://en.wikipedia.org/wiki/Proportional_control Proportional control overcomes this by modulating the output to the controlling device, such as a continuously variable valve. An analogy to on-off control is driving a car by applying either full power or no power and varying the duty cycle, to control speed. The power would be on until the target speed is reached, and https://en.wikipedia.org/wiki/Proportional_control then the power would be removed, so the car reduces speed. When the speed falls below the target, with a certain hysteresis, full power would again be applied. It can be seen that this looks like pulse-width modulation, but would obviously result in poor control and large variations in speed. The more powerful the engine; the greater the instability, the heavier the car; the greater the stability. Stability may be expressed as correlating to the power-to-weight ratio of the vehicle. Proportional control is how most drivers control the speed of a car. If the car is at target speed and the speed increases slightly, the power is reduced slightly, or in proportion to the error (the actual versus target speed), so that the car reduces speed gradually and reaches the target point with very little, if any, "overshoot", so the result is much smoother control than on-off control. Further refinements like PID control would help compensate for additional variables like hills, w
- The Simplest PID Controller controlguru We have discussed the general proportional only (P-Only) algorithm structure and considered important design and tuning issues associated with implementation. Here we investigate the capabilities of the P-Only controller on our heat exchanger process and highlight http://controlguru.com/p-only-control-of-the-heat-exchanger-shows-offset/ some key features and weaknesses of this simple algorithm. The heat exchanger process used in this study is shown below (click for a large view) and discussed in more detail here. As with all controller implementations, best practice is to follow the four-step design and tuning recipe as we proceed with the study: Step 1: Design Level of Operation (DLO) Real processes display a nonlinear behavior. That is, their process gain (Kp), time constant (Tp) proportional control and/or dead time (Өp) changes as operating level changes and as major disturbances change. Since the rules and correlations we use are based on these Kp, Tp and Өp values, controllers should be designed and tuned for a specific level of operation. The first step in the controller design recipe is to specify our design level of operation (DLO). This includes stating where we expect the set point, SP, and measured process variable, PV, offset error in to be during normal operation. Hopefully, these will be the same values as this is the point of a controller. We also should have some sense of the range of values the SP and PV might assume so we can explore the nature of the process dynamics across that range. For the heat exchanger, we specify that the SP and PV will normally be at 138 °C, and during production, they may range from 138 to 140 °C. Thus, we can state: ▪ Design PV and SP = 138 °C with range of 138 to 140 °C We also should know normal or typical values for our major disturbances and be reasonably confident that they are quiet so we may proceed with a bump test. As shown in the graphic above, the heat exchanger process has only one major disturbance variable (D), a side stream labeled Warm Liquid Flow. We specify that the expected or design value for this stream is: ▪ Expected warm liquid flow disturbance, D = 10 L/min We assume that D remains quiet and at this normal design value throughout the study. Step 2: Collect Data at the DLO The next step in the design recipe is to collect dynamic process data as near as practical to our design level of operation. We have previously collected and document