First Order Open-Loop Systems

First Order Open-Loop Systems

Control System ClassificationAn open-loop control system utilizes an actuating device to control the process directly without using feedback.

A closed-loop feedback control system uses a measurement of the output and feedback of the output signal to compare it with the desired output or reference.

Actuating DeviceProcessOutputDesired Output ResponseDesired Output Response

MeasurementOutput

ControllerProcess

ComparisonSingle Input Single Output (SISO) System

Control System ClassificationOpen-Loop Control System

Missile Launcher System

Control System Classification

Closed-Loop Feedback Control SystemMissile Launcher System

Turntable Speed ControlApplication: CD player, computer disk driveRequirement: Constant speed of rotationOpen loop control system:

Block diagram representation:

Turntable Speed ControlClosed-loop control system:

Block diagram representation:

Open Loop Systemcontrol system in which no measurement of the system output is used to alter the controloperates without feedback and directly generates the output in response to an input signal.control actions taken are independent of system output fluid characteristicsa true open-loop system can not engage in machine learning and also cannot correct any errors that it could makemay not compensate for disturbances in the system3/23/2015Page 7

First-order systemControl system which has a first-order Laplace transform functionOrder of function: highest exponential power

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1st Order SystemsThe 1st order system is represented by the differential equation

Eq.1where e(t) = outputr(t) = inputa0, a1, b0 = constants

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Dividing the equation by a0, then

whereT = time constant (dimension of time) K = static sensitivity

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Taking the Laplace transform for the equation

Transform function of a 1st order system:

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Example of 1st Order Open-Loop SystemIn the case of open-loop control of the room temperature according to the figure,the outdoor temperature will be measured by a temperature sensor and fed into a control device.

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Comparison to Closed-Loop SystemIn the case of closed-loop control of the room temperature as shown in the figure,the room temperature is measured and compared with the set-point value. If the room temperature deviates from the given set-point value, a controller (C) alters the heat flow. All changes of the room temperature, e.g. caused by opening the window or by solar radiation, are detected by the controller and removed.

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Response of the first order system

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Example

Control of the Transient Response of Control Systems

Control of the Transient Response of Control Systems

Control of the Transient Response of Control Systems

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