- •Distributed Control Systems (DCS)
- •Fieldbus control
- •Practical PID controller features
- •Manual and automatic modes
- •Output and setpoint tracking
- •Alarm capabilities
- •Output and setpoint limiting
- •Security
- •Digital PID algorithms
- •Introduction to pseudocode
- •Position versus velocity algorithms
- •Note to students
- •Proportional plus integral control action
- •Proportional plus derivative control action
- •Full PID control action
- •Review of fundamental principles
- •Process dynamics and PID controller tuning
- •Process characteristics
- •Integrating processes
- •Runaway processes
- •Lag time
- •Multiple lags (orders)
- •Dead time
- •Hysteresis
- •Before you tune . . .
- •Identifying operational needs
- •Identifying process and system hazards
- •Identifying the problem(s)
- •Final precautions
- •Quantitative PID tuning procedures
- •Heuristic PID tuning procedures
- •Features of P, I, and D actions
- •Tuning recommendations based on process dynamics
- •Tuning techniques compared
- •Tuning a liquid level process
- •Tuning a temperature process
- •Note to students
- •Electrically simulating a process
- •Simulating a process by computer
- •Review of fundamental principles
- •Basic process control strategies
- •Supervisory control
- •Cascade control
- •Ratio control
- •Relation control
- •Feedforward control
- •Load Compensation
- •Proportioning feedforward action
- •Feedforward with dynamic compensation
- •Dead time compensation
- •Lag time compensation
- •Lead/Lag and dead time function blocks
- •Limit, Selector, and Override controls
- •Limit controls
29.16. NOTE TO STUDENTS |
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29.16.4Proportional plus derivative control action
1.Set the controller PV input to 50% (3 volts) and the output value to 50% in manual mode.
2.Configure the controller for reverse action (this is typically the default setting).
3.Configure the PID settings with a proportional (gain) value of 1 (P.B. = 100%) and a derivative value of 1 minute. Set integral action at zero repeats per minute (maximum number of minutes per repeat).
4.Switch the controller mode to “automatic.”
5.Adjust the PV signal to 75% (4 volts) and observe the output. Which way does the output signal move? How does the output signal value compare while you are adjusting the input voltage versus after you reach 4 volts and take your hand o the adjustment knob? How does this action compare with the proportional-only test?
6.Adjust the PV signal to 25% (2 volts) and observe the output. Which way does the output signal move? How does the output signal value compare while you are adjusting the input voltage versus after you reach 4 volts and take your hand o the adjustment knob? How does this action compare with the proportional-only test?
7.Change the controller’s gain setting to some di erent value and repeat the previous two steps. Can you tell which aspect of the output signal’s response is due to proportional action and which aspect is due to derivative action?
8.Change the controller’s derivative setting to some di erent value and repeat those same two steps. Can you tell which aspect of the output signal’s response is due to proportional action and which aspect is due to derivative action?
9.Smoothly vary the input signal back and forth between 0% and 100% (1 and 5 volts). How does the output respond when you do this? Try changing the derivative setting again and re-checking.
10.Switch the controller’s action from reverse to direct, then repeat the previous two steps. How does the output respond now?
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CHAPTER 29. CLOSED-LOOP CONTROL |
29.16.5Full PID control action
1.Set the controller PV input to 50% (3 volts) and the output value to 50% in manual mode.
2.Configure the controller for reverse action (this is typically the default setting).
3.Configure the PID settings with a proportional (gain) value of 1 (P.B. = 100%), an integral value of 1 repeat per minute (or 1 minute per repeat), and a derivative action of 1 minute.
4.Switch the controller mode to “automatic.”
5.Adjust the PV signal to 75% (4 volts) and observe the output. Which way does the output signal move? Does the output signal drift or does it remain the same when you stop changing the PV signal? How does magnitude of the output signal compare while you are changing the input voltage, versus when the input signal is steady?
6.Adjust the PV signal to 25% (2 volts) and observe the output. Which way does the output signal move? Does the output signal drift or does it remain the same when you stop changing the PV signal? How does magnitude of the output signal compare while you are changing the input voltage, versus when the input signal is steady?
7.Change the controller’s gain setting to some di erent value and repeat the previous two steps. Can you tell which aspect of the output signal’s response is due to proportional action, which aspect is due to integral action, and which aspect is due to derivative action?
8.Change the controller’s integral setting to some di erent value and repeat the same two steps. Can you tell which aspect of the output signal’s response is due to proportional action, which aspect is due to integral action, and which aspect is due to derivative action?
9.Change the controller’s derivative setting to some di erent value and repeat the same two steps. Can you tell which aspect of the output signal’s response is due to proportional action, which aspect is due to integral action, and which aspect is due to derivative action?
10.Smoothly vary the input signal back and forth between 0% and 100% (1 and 5 volts). How does the output respond when you do this? Try changing the gain, integral, and/or derivative settings again and re-checking.
11.Switch the controller’s action from reverse to direct, then repeat the previous two steps. How does the output respond now?