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In control systems, sliding mode control (SMC) is a nonlinear control method that alters the dynamics of a nonlinear system by applying a discontinuous control signal (or more rigorously, a set-valued control signal) that forces the system to "slide" along a cross-section of the system's normal behavior.
Direct digital control is often used to control heating, ventilating, and air conditioning devices such as valves via microprocessors using software to perform the control logic. Such systems receive analog and digital inputs from the sensors and devices and, according to the control logic, provide analog or digital outputs. [1] These systems ...
In variable-flow hydronic systems, reducing pump speed or staging of pumps with boilers and chillers to suit part-load conditions is an energy efficient method of control. [ 5 ] VAV (variable air flow) systems meet the needs of large modern commercial-use buildings, with internal spaces divided into open-plan areas.
For example, a symbol of a pump can show the operator that the pump is running, and a flow meter symbol can show how much fluid it is pumping through the pipe. The operator can switch the pump off from the mimic by a mouse click or screen touch. The HMI will show the flow rate of the fluid in the pipe decrease in real time.
A water chiller [1] is a device used to lower the temperature of water. Most chillers use refrigerant in a closed loop system to facilitate heat exchange from water where the refrigerant is then pumped to a location where the waste heat is transferred to the atmosphere. However, there are other methods in performing this action.
A sail switch, vane switch or flow switch is a mechanical switch that is actuated on or off in response to the flow or non-flow of a fluid such as air or water. [1] A sail switch typically operates through the use of a paddle or a diaphragm which gets displaced due to the force of fluid or air moving past it. Sail switches find application in ...
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A pressure switch is a form of switch that operates an electrical contact when a certain set fluid pressure has been reached on its input. The switch may be designed to make contact either on pressure rise or on pressure fall. Pressure switches are widely used in industry to automatically supervise and control systems that use pressurized fluids.