1.6 Summary

You should now be able to formulate a control problem in terms of the following:

• Control objective

• Inputs (manipulated or disturbance)

• Outputs (measured or unmeasured)

• Constraints (hard or soft)

• Operating characteristics (continuous, batch, semibatch)

• Safety, environmental, and economic issues

• Control structure (feedback, feed forward)

You should also be able to sketch control and instrumentation diagrams, and control block diagrams. In addition, you should be able to recommend whether a control valve should be fail-open or fail-closed.

The following terms were introduced in this chapter:

• Actuator

• Air-to-close

• Air-to-open

• Algorithm

• Control block diagram

• Control valve

• Controller

• Deadtime or time-delay

• Digital

• Fail-closed

• Fail-open

• Gain

• Integrating process

• Model

• Process gain

• Process and instrumentation diagram

• Sensor

• Setpoint

The abstract notions of states, inputs, outputs, and parameters were introduced and are covered in more detail in Chapter 2. The examples used were as follows:

1.1 Surge Tank

1.2 Taking a Shower

1.3 Liquid Surge Vessel Model