ISA CAP Advanced Techniques & Methods 2

Question 1

Which model predictive control (MPC) feature distinguishes it from conventional PID control?

Accepted Answer

It optimizes over a future prediction horizon subject to constraints

Answer

MPC explicitly optimizes manipulated variables over a receding prediction horizon while satisfying process and equipment constraints.

Question 2

In cascade control, which loop is tuned first and why?

Accepted Answer

The secondary (inner) loop, because it must respond faster than the primary

Answer

The secondary (inner) loop is tuned first because it must be sufficiently fast to reject disturbances before the primary loop responds.

Question 3

What is the primary purpose of a Smith Predictor in a control loop?

Accepted Answer

To compensate for large dead time in the process

Answer

The Smith Predictor uses a process model to remove dead time from the closed-loop characteristic equation, enabling better control of processes with large time delays.

Question 4

When applying the Internal Model Control (IMC) design method, the IMC filter time constant (λ) is adjusted primarily to trade off:

Accepted Answer

Closed-loop speed of response versus robustness to model error

Answer

Increasing λ slows the closed-loop response but provides greater robustness when the process model is imperfect.

Question 5

In a ratio control scheme for blending two streams, the ratio controller output adjusts which variable?

Accepted Answer

The setpoint of the controlled stream flow controller

Answer

The ratio controller multiplies the measured wild (uncontrolled) stream flow by the desired ratio to set the setpoint for the controlled stream flow controller.

(ISA CAP) ISA Certified Automation Professional Practice Test

(ISA CAP) ISA Certified Automation Professional Practice Test

ISA CAP Advanced Techniques & Methods 2