China
Africa
Explore chapters and articles related to this topic
Control terminology, theory, and tuning
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
Control may be described as open-loop control or closed-loop control. Open-loop control does not use feedback to the controller and is much less common in industrial control. Instead, control is based on time. A good example of open-loop control is a washing machine, where the wash, spin, and rinse cycle times are preprogrammed, based on experience, and there is no feedback to indicate cleanliness has been achieved. For plant operations, automatic backwashing filters may use open-loop control for a cleaning cycle followed by differential-pressure measurement across the filter to determine whether fouling was resolved. A more sophisticated backwashing filter might be programmed to make several open-loop cleaning attempts if the pressure differential does not come within acceptable limits, and the controller may initiate an alarm after several unsuccessful attempts.
Characteristics of Feedback Control Systems
Published in Arthur G.O. Mutambara, Design and Analysis of Control Systems, 2017
In contrast to an open-loop control system, a closed-loop control system utilizes an additional measure of the actual output to compare the actual output with the desired output response. The measure of the output is called the feedback signal. The elements of a general closed-loop feedback control system are shown in Figure 4.3. A closed-loop control system compares a measurement of the output with the desired input (reference or command input). The difference between the two quantities is then used to drive the output closer to the reference input through the controller and actuator. The general block diagram model of a closed-loop control system is shown in Figure 4.4.
Control Systems
Published in Albert Thumann, D. Paul Mehta, Handbook of Energy Engineering, 2020
An open-loop system is a system in which the output has no effect upon the input signal. A clothes dryer may be considered as an open-loop control system in which input is the status of the electric switch (on/off) and the output is the dryness (moisture content) of the clothes. When the dryer is turned on, it runs for a pre-set time and then automatically turns off. The actual moisture content of the clothes has no effect on the on-time.
An active swing suppression control scheme of overhead cranes based on input shaping model predictive control
Published in Systems Science & Control Engineering, 2023
Weiqiang Tang, Erpeng Zhao, Lijuan Sun, Haiyan Gao
The control of overhead cranes has attracted the wide attention of researchers in the communities of mechatronics and control. A great quantity of techniques are available in the literature, and they can be divided into open-loop and closed-loop ones according to the use of information. Open-loop control techniques only need system model information and do not need additional measuring devices, so they are simpler and easier to implement in practice. Input shaping is the most commonly used open-loop control technique in crane swing suppression, proposed by Singer and Seering (1990). This technique fully considers the physical and vibration characteristics of a system, so that the vibration modes in the system are not excited by the input signal, thus the vibration of the system is suppressed fundamentally.
Effect of movable insulation on performance of the Building integrated Semi-transparent Photovoltaic Thermal (BiSPVT) system for harsh cold climatic conditions: a case study
Published in International Journal of Ambient Energy, 2022
Neha Gupta, Pooja Rani, G. N. Tiwari
For automated blinds, a few of the algorithms used are time controlled for orientation and season or are based on a single solar radiation threshold value. This means such blinds are adjusted automatically depending on the amount of direct solar radiation that penetrates inside the room (Inoue and Itoh 1989; Leslie et al. 2005). Newsham (1994) suggested a blind control operation model based on the thermal comfort model assumption which means if the solar radiation with intensity greater than 233 fell on the occupants, the blinds will close. Similarly, Oscar Faber Associates (Foster and Oreszczyn 2001) chose the value of solar intensity to be 300 to represent threshold that occupants would start using the blinds. Recently automated systems may be used in buildings for energy savings and improving the thermal environment of the space. These systems facilitate effective utilisation of solar radiation and natural light. Control strategies for blinds and curtains are mainly divided into open loop and closed loop systems. Closed loop system receives the feedback, whereas open loop system does not. To explain this further, in an open loop system, the photo-sensor is placed only to detect the natural light and therefore is insensitive to the artificial light that it controls (no feedback). Today, there are automated window blinds available that are equipped with photometers either in an open loop or a closed loop control system. An example of a closed loop system can be explained as a series of indoor photosensors integrated with dimmers to maintain illuminance levels (Jain and Garg 2018).
A Behavioral Study of Different Controllers and Algorithms in Real-Time Applications
Published in IETE Journal of Research, 2022
Closed-loop system – In a closed-loop control system, input depends upon output. Due to external disturbances output of the system will change. By connecting the feedback open loop system is transformed into a closed-loop control system. According to the requirement, the output can be maintained as per requirement by using a feedback system. This control system is also referred to as an automated control system. The closed-loop control system was shown below in Figure 2.