## Objectives

Define and explain the purpose of a process control system, identify the impact of changes in process parameters on a process control system, and explain the components of the block diagram and its usefulness as a tool.

Explain open- and closed-loop control, describe the application of open-loop control and the advantages of closed-loop control, explain feedback control and the operation and performance of closed-loop control, and describe process stability and the criteria for judging the quality of closed-loop control.

Describe how proportional control systems work with regards to the definite position of the final control element, describe the relationship of proportional band to gain, define direct- and reverse-acting controllers, and describe the proportional control characteristics.

Describe the advantages and disadvantages of proportional-and- integral control systems, explain how proportional-and-integral control systems work and the effects of various changes on controller output, and determine the effects of errors caused by disturbances on the process control system.

Compare proportional-and-integral control mode and proportional-and-derivative control mode and explain how proportional-and-derivative control works. also describe the controller output with the effect of derivative action, proportional-only action, proportional-and-derivative output, and error signal; and explain the impact of different derivatives times on the process response.

Explain the role of PID control in an application; recall the different types of controllers; identify the causes of open-loop waveforms; and determine the effects of PID mode on the process control.

Explain which two methods are used to determine the settings for the controller, describe stability as it relates to response and speed, explain the procedures for adjusting controller tuning, describe the information concerning the process needed for open-loop tuning methods obtained from the process reaction curve and describe the two methods used to extract information provided by process reaction curves.

Describe the Ziegler-Nichols controller tuning method and the dampened oscillation method, and explain the disadvantages of the ultimate period method and the dampened oscillation method.

Explain how to read a frequency response curve, explain the effects of adjusting the length of the proportional band in the curve, explain the effect of adjusting the width of the integral and derivative sections in the curve, and describe how the notch tuning procedure is performed for tuning a controller in service.

State the important forms of advanced control methods, explain how cascade control works, explain the advantages of feedforward control over feedback control, and describe the function and process of ratio control.

Describe the basic types of pneumatic and hydraulic actuators and their operating characteristics, explain the functions of valve positioners, and describe the purpose of a split-range control and an I to P transducer.

Explain the function of the final control element in a process control system, describe the designs of globe valves, butterfly valves, gate valves, and dampers, describe valve characteristics, and explain the purpose of using variable speed drives, or VSDs.