Learning ObjectivesThe definitions of the following terms: input, output, feedback, error, open loop, and closed loop.Requirements of good control systemAdvantages and disadvantages of open-loop control systems with an exampleAdvantages and disadvantages of close-loop control systems with an exampleFeedforward and feedback system

Control theory and control systems engineering are concerned with the understanding and control of forces of nature to benefit humans.Control is relevant to a wide variety of engineering systems, both in terms of system design and analysis. Control engineering spans the disciplines of mechanical, electrical, chemical, civil and environmental engineering. It is also relevant to computer science, especially AI.Examples of systems for which control engineering is applicable include manufacturing, energy, transportation, fluids, communications, robots, and complex dynamical systems.

Requirements Of A Good Control SystemAccuracy SensitivityRepeatability HysteresisDisturbanceStability Speed Bandwidth Oscillation

Control System TerminologyInput - Excitation applied to a control system from an external source.Output - The response obtained from a systemFeedback - The output of a system that is returned to modify the input.Error - The difference between the input and the output.

Control System TerminologyManipulated variable The output of the controller is the manipulated variable that controls the output of the plant.Disturbance It is the undesired input. e. g. noiseFeedback element It produces feedback signal proportional to controlled output.

Types of Control SystemsOpen-LoopA system in which the control action is totally independent of the output of the systemSimple control system which performs its function without concerns for initial conditions or external inputs.

Types of Control SystemsClosed-Loop (feedback)Uses the output of the process to modify the process to produce the desired result.Continually adjusts the process.

Viscosity control system(open loop)BACK PRESSURE VALVEHEATER FILTERTRANSDUCERSTEAMOILTANKMAIN ENGINEMANUAL CONTROL

Open Loop SystemCONTROLLERPLANTREFERENCEINPUTCONTROLLEDOUTPUT

Viscosity control system(close feedback loop)BACK PRESSURE VALVEHEATER FILTERTRANSDUCERSET POINT12-14 CSTSTEAMOILTANKMAIN ENGINEMEASURED VALUE AND FEEDBACK+-CONTROLLER MANIPULATEDVARIABLE

Negative Feedback (closed loop) Control SystemCONTROLLERCONTROLLING DEVICEFEEDBACK ELEMENT+-OUTPUTREFERENCEINPUTPROCESS

Viscosity control system(close feedforward loop)BACK PRESSURE VALVEHEATER FILTERTRANSDUCERSET POINT12-14 CSTSTEAMOILTANKMAIN ENGINEMEASURED VALUE AND FEEDBACK+-SUMMATIONRELAYCONTROLLER

Feedforward (closed loop) Control SystemCONTROLLERFEEDFORWARD ELEMENT+DISTURBANCECONTROLLERCONTROLLING DEVICEFEEDBACK ELEMENT+-REFERENCEINPUT++PROCESS

Advantages of a Open-Loop System Simple in construction and DesignEconomicEasy for maintenance

Dis-advantages of a Open Loop System Inaccurate and unreliable Accuracy depends on calibration.Sensitive to parameters variationsOutput of the system changes due to environmental conditions, internal disturbances.

Advantages of a Closed-Loop System Increased AccuracyIncreased ability to reproduce output with varied input.Reduced Sensitivity to DisturbanceSelf-correcting minimizes effects of system changes.Smoothing and FilteringSystem induced noise and distortion are reduced.

Dis-advantages of a Closed-Loop System Complicated in designMaintenance is costlier.System may become unstable

Open Vs. Closed Loop Systems Open LoopHighly sensitive to environmentSimple DesignAccuracy dependant on calibrationUnlikely to become unstableSmall bandwidthClosed LoopLess sensitive to changes in environmentComplex in designMore accurateSmooth responseCan become unstableLarge bandwidth

Questions?

Dynamically or actively command, direct, or regulate themselves or other systems. Discuss Slide1. Introduction: a. Most equipment have some form of a controller to make it function. b. Most have something more than just an on/off switch as a controller. c. Two major types of controllers in use:

2. Open-Loop. a. Performs its action without regard to the output or any external input. Example: The controller on a washing machine. a. It will run the washer through the cycle without regard for the cleanliness of the clothes in the machine, if there is soap in the machine, temperature of the water, how much clothes are in the machine, etc.

3. Closed-Loop (Feedback) a. Senses the output of the controller or process. b. Uses this output to change the process to meet the desired result. c. Controller can determine how accurate the output is or if it producing the desired result. d. Control action depends on the output of the system.Example: Aircraft auto Pilot set to keep plane at altitude.1. Introduction: a. Most equipment have some form of a controller to make it function. b. Most have something more than just an on/off switch as a controller. c. Two major types of controllers in use:

2. Open-Loop. a. Performs its action without regard to the output or any external input. Example: The controller on a washing machine. a. It will run the washer through the cycle without regard for the cleanliness of the clothes in the machine, if there is soap in the machine, temperature of the water, how much clothes are in the machine, etc.

3. Closed-Loop (Feedback) a. Senses the output of the controller or process. b. Uses this output to change the process to meet the desired result. c. Controller can determine how accurate the output is or if it producing the desired result. d. Control action depends on the output of the system.Example: Aircraft auto Pilot set to keep plane at altitude.1. Increased Accuracy a. Ability to faithfully reproduce the output.

2. Reduced Sensitivity to Disturbances a. Ability of the system to produce the same output repeatedly in spite of variations and fluctuations within the control system (worn gears, sticky components etc.) b. Changes within the system are reduced and the effects of the changes can be minimized.

3. Smoothing and filtering. Undesirable effects of noise and distortion within the system are reduced.

4. Increased Bandwidth. Can operate satisfactorily over a wide range of frequencies or variations in the input.

1. Increased Accuracy a. Ability to faithfully reproduce the output.

2. Reduced Sensitivity to Disturbances a. Ability of the system to produce the same output repeatedly in spite of variations and fluctuations within the control system (worn gears, sticky components etc.) b. Changes within the system are reduced and the effects of the changes can be minimized.

3. Smoothing and filtering. Undesirable effects of noise and distortion within the system are reduced.

4. Increased Bandwidth. Can operate satisfactorily over a wide range of frequencies or variations in the input.

1. Increased Accuracy a. Ability to faithfully reproduce the output.

2. Reduced Sensitivity to Disturbances a. Ability of the system to produce the same output repeatedly in spite of variations and fluctuations within the control system (worn gears, sticky components etc.) b. Changes within the system are reduced and the effects of the changes can be minimized.

3. Smoothing and filtering. Undesirable effects of noise and distortion within the system are reduced.

4. Increased Bandwidth. Can operate satisfactorily over a wide range of frequencies or variations in the input.

1. Increased Accuracy a. Ability to faithfully reproduce the output.

2. Reduced Sensitivity to Disturbances a. Ability of the system to produce the same output repeatedly in spite of variations and fluctuations within the control system (worn gears, sticky components etc.) b. Changes within the system are reduced and the effects of the changes can be minimized.

3. Smoothing and filtering. Undesirable effects of noise and distortion within the system are reduced.

4. Increased Bandwidth. Can operate satisfactorily over a wide range of frequencies or variations in the input.