PID Controller Design, Tuning, And Troubleshooting

Question 1

Performance criteria for closed loop systems

Answer 1

1. The closed loop system must be stable.
2. The effects of disturbance are minimized providing good disturbance rejection.
3. Rapid smooth responses to setpoint changes are obtained (good set point tracking).
4. Steady state error(offset) is eliminated.
5. Excessive control action is avoided.
6. The control system must be robust- insensitive to changes in process conditions and to inaccuracies in the process model.

Question 2

Direct Synthesis

Answer 2

Feedback controller design is based on a process model and closed loop transfer function

Question 3

Important advantage of the direct synthesis method

Answer 3

It provides valuable insight into the relationship between the process model and the resulting controller

Question 4

When are time-delay approximations less accurate?

Answer 4

When the time delay is relatively large compared to the dominant time constant of the process

Question 5

Advantage of the IMC design method

Answer 5

It allows model uncertainty and tradeoffs between performance and robustness to be considered in a more systematic fashion.