China
Africa
Explore chapters and articles related to this topic
Controls
Published in Carl Bozzuto, Boiler Operator's Handbook, 2021
The term loop is used to describe parts of a control system, as in a control loop. Each control loop is like a circle. There is no end to it. The parameter to be controlled (process variable) is sensed by the controller, which com-pares that value to the set point. It then adjusts its output accordingly. The change in output produces a change in the process variable. The controller compares that new value to the set point to change its output again. A control loop contains a controller, a device to measure the process variable, a source of set point, and an output device that controls the flow and anything else that changes the value of the process variable or the set point. A control loop can be as simple as a level controller, consisting of a controller with an internal set point adjustment, a level transmitter (LT), and a control valve. A complicated control loop could have similar devices in combination with a large number of computers located in different parts of the plant. The practical limit of a loop is at the devices that affect the process variable. Any one of those devices can be part of another control loop.
Heating and Cooling Energy
Published in Michael Frank Hordeski, Hydrogen & Fuel Cells: Advances in Transportation and Power, 2020
The control may go beyond basic proportional temperature control and to integral or derivative control. In this case, the integral or derivative is used to calculate the amount that the temperature is from the setpoint. The control action is now limited to avoid overshooting the setpoint and the oscillations that cause delays in control response. These delays can often occur with proportional control. Derivative control is often used in dynamic applications such as pressure control. Derivative control will measure the change of speed in the controlled condition and adjust the action of the control algorithm to respond to this change. The use of a combined Proportional, Integral and Derivative (PID) control loop allows the control variable to be accurately maintained at the desired levels with very little deviation. A combined sequence like PID can be used to integrate the control of several pieces of heating and cooling equipment to provide a more efficient and seamless operation. Combining this type of more accurate control with networking has been an important advance in building control.
Controls
Published in Kenneth E. Heselton, Boiler Operator’s Handbook, 2020
Now we can define a loop. We use the term loop to describe parts of a control system because each control loop is like a circle; there’s no end to it. The parameter we’re trying to control (process variable) is sensed by the controller which compares that value to the setpoint then adjusts its output accordingly. The change in output produces a change in the process variable and the controller compares that new value to the setpoint to change its output again. A control loop contains a controller, a device to measure the process variable, a source of setpoint, an output device that controls the flow and anything else that changes the value of the process variable or the setpoint.
Explainable AI for Security of Human-Interactive Robots
Published in International Journal of Human–Computer Interaction, 2022
Antonio Roque, Suresh K. Damodaran
Figure 2 shows a control loop, which is central to the control-theoretic approach to modeling security Roque et al. (2016); Giraldo et al. (2018). A simple example of a control loop is a thermostat, where the sensor is a thermometer, and the controller is a simple mechanism that is set to a desired temperature using a set point. In this case, the “system” is the home or office environment, whose temperature is detected by the sensor. If the sensor detects that the environment is too cold, then the controller actuates a heater, which increases the temperature of the system (i.e., the environment). If the sensor detects that the environment is too warm, then the controller actuates a cooler, which decreases the temperature of the system/environment. The environment temperature is monitored by the sensor, which again continues to use the controller to adjust the temperature.
Nonlinear Optimal Control for the Translational Oscillator with Rotational Actuator
Published in Cybernetics and Systems, 2021
The performance of the proposed nonlinear optimal (H-infinity) control scheme for the model of the TORA has been tested through simulation experiments. The obtained results are depicted in Figures 3–10. The real values of the state variables of the system are depicted in blue, the estimated values are printed in green, while the related setpoints are plotted in red. It can be considered that in all experiments fast and accurate tracking of the reference setpoints has been achieved. For the implementation of sensorless feedback control, the H-infinity Kalman Filter has been used as a robust state estimator. Using the H-infinity Kalman Filter, a state estimation-based implementation of the control method has been enabled. This allows the reliable functioning of the control loop after receiving measurements from a small number of sensors.
Introducing a system theoretic framework for safety in the rail sector: supplementing CSM-RA with STPA
Published in Safety and Reliability, 2020
Ross Dunsford, Mikela Chatzimichailidou
The steps that one needs to take to implement the STPA hazard analysis are given in Table 2. Figure 3 (Leveson & Thomas, 2018) depicts a generic control loop, which is used for the creation of the hierarchical safety control structure mentioned in STPA Step (2a). A controller provides control actions to control some process and to enforce constraints on the behaviour of the controlled process. The control algorithm represents the controller’s decision-making process and determines the control actions to provide. The controller generates a hypothesis about the controlled process by using the information in the process model. Process models include beliefs about the process being controlled and other relevant aspects of the system or the environment and they can be updated by feedback used to observe the controlled process (Leveson & Thomas, 2018). The overall aim of the control loop is to keep the process operating within predefined limits or set points (the goal) despite disturbances to the process. The principle is not to restrict changes, but to preserve a dynamic equilibrium (Dokas, Feehan, & Imran, 2013).