Open-loop controller

Open-loop controller

An open-loop controller, also called a non-feedback controller, is a type of controller that computes its input into a system using only the current state and its model of the system.

A characteristic of the open-loop controller is that it does not use feedback to determine if its output has achieved the desired goal of the input. This means that the system does not observe the output of the processes that it is controlling. Consequently, a true open-loop system can not engage in machine learning and also cannot correct any errors that it could make. It also may not compensate for disturbances in the system.

For example, an irrigation sprinkler system, programmed to turn on at set times could be an example of an open-loop system if it does not measure soil moisture as a form of feedback. Even if rain is pouring down on the lawn, the sprinkler system would activate on schedule, wasting water.

Open-loop control is useful for well-defined systems where the relationship between input and the resultant state can be modeled by a mathematical formula. For example determining the voltage to be fed to an electric motor that drives a constant load, in order to achieve a desired speed would be a good application of open-loop control. If the load were not predictable, on the other hand, the motor's speed might vary as a function of the load as well as of the voltage, and an open-loop controller would therefore be insufficient to ensure repeatable control of the velocity.

An example of this is a conveyor system that is required to travel at a constant speed. For a constant voltage, the conveyor will move at a different speed depending on the load on the motor (represented here by the weight of objects on the conveyor). In order for the conveyor to run at a constant speed, the voltage of the motor must be adjusted depending on the load. In this case, a closed-loop control system would be necessary.

An open-loop controller is often used in simple processes because of its simplicity and low cost, especially in systems where feedback is not critical. A typical example would be a conventional washing machine, for which the length of machine wash time is entirely dependent on the judgment and estimation of the human operator. Generally, to obtain a more accurate or more adaptive control, it is necessary to feed the output of the system back to the inputs of the controller. This type of system is called a closed-loop system.

See also

References

Kuo, Benjamin C. (1991). Automatic Control Systems (6th ed.). New Jersey: Prentice Hall. ISBN 0-13-051046-7.


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Open-loop controller — Un open loop controller, también llamado non feedback controller, es un tipo de controlador que procesa su entrada en un sistema usando solamente el estado actual y este modelo del sistema. Una característica del controlador open loop es de que… …   Wikipedia Español

  • Open-loop — may refer to: Open loop controller of a dynamical system Open loop model in game theory Open loop rhetorical device This disambiguation page lists articles associated with the same title. If an …   Wikipedia

  • Controller (control theory) — In control theory, a controller is a device which monitors and affects the operational conditions of a given dynamical system. The operational conditions are typically referred to as output variables of the system which can be affected by… …   Wikipedia

  • Closed-loop transfer function — A closed loop transfer function in control theory is a mathematical expression (algorithm) describing the net result of the effects of a closed (feedback) loop on the input signal to the circuits enclosed by the loop. Contents 1 Overview 2… …   Wikipedia

  • PID controller — A block diagram of a PID controller A proportional–integral–derivative controller (PID controller) is a generic control loop feedback mechanism (controller) widely used in industrial control systems – a PID is the most commonly used feedback… …   Wikipedia

  • Boost controller — Boost control is the principle of controlling the boost level produced in the intake manifold of a turbocharged or supercharged engine by affecting the air pressure delivered to the pneumatic and mechanical wastegate actuator. Boost controllers… …   Wikipedia

  • Motor controller — A motor controller is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor.[1] A motor controller might include a manual or automatic means for starting and stopping the motor,… …   Wikipedia

  • Closed-loop pole — Closed loop poles are the positions of the poles (or eigenvalues) of a closed loop transfer function in the s plane. The open loop transfer function is equal to the product of all transfer function blocks in the forward path in the block diagram …   Wikipedia

  • Closed loop — may refer to: A feedback loop, often found in: Control theory#Closed loop transfer function, where a closed loop controller may be used Electronic feedback loops in electronic circuits PID controller, a commonly used closed loop controller Closed …   Wikipedia

  • Radio Network Controller — The Radio Network Controller (or RNC) is the governing element in the UMTS radio access network (UTRAN) responsible for control of the Node Bs, that is to say the base stations which are connected to the controller. The RNC carries out radio… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”