For this reason, closed loop controllers are also called feedback controllers. A closed loop controller therefore has a feedback loop which ensures the controller exerts a control action to give a process output the same as the "reference input" or "set point".
In the case of the boiler analogy this would include a thermostat to monitor the building temperature, and thereby feed back a signal to ensure the controller maintains the building at the temperature set on the thermostat. In closed loop control, the control action from the controller is dependent on the process output. The control action is the switching on/off of the boiler, but the controlled variable should be the building temperature, but is not as this is open-loop control of the boiler, which does not give closed-loop control of the temperature. A good example of this is a central heating boiler controlled only by a timer, so that heat is applied for a constant time, regardless of the temperature of the building. In open-loop control, the control action from the controller is independent of the "process output" (or "controlled process variable"). However, an open-loop system cannot correct any errors that it makes or correct for outside disturbances, and cannot engage in machine learning.Īn electromechanical timer, normally used for open-loop control based purely on a timing sequence, with no feedback from the process.įundamentally, there are two types of control loop: open-loop (feedforward) control, and closed loop (feedback) control. The advantage of using open-loop control in these cases is the reduction in component count and complexity. There are many open-loop controls, such as on/off switching of valves, machinery, lights, motors or heaters, where the control result is known to be approximately sufficient under normal conditions without the need for feedback. It does not use feedback to determine if its output has achieved the desired goal of the input command or process "set point". In an open-loop controller, also called a non-feedback controller, the control action from the controller is independent of the "process output", which is the process variable that is being controlled. ( January 2015) ( Learn how and when to remove this template message) Please help to improve this article by introducing more precise citations. This article includes a list of general references, but it remains largely unverified because it lacks sufficient corresponding inline citations.
0 kommentar(er)
