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Control is checking current performance against pre-determined standards contained in the plans, with a view to ensuring adequate progress and satisfactory performance. According to Harold Koontz: Controlling is the measurement and correction of performance to make sure that enterprise objectives and the plans devised to attain them are ...
In open-loop control, the control action from the controller is independent of the "process output" (or "controlled process variable"). 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.
For example, construction professionals cannot remove the danger of asbestos when handling the hazardous agent is the core of the task. [3] The most effective control measure is eliminating the hazard and its associated risks entirely. The simplest way to do this is by not introducing the hazard in the first place.
Although feedback is an important aspect of control engineering, control engineers may also work on the control of systems without feedback. This is known as open loop control. A classic example of open loop control is a washing machine that runs through a pre-determined cycle without the use of sensors.
A control loop is the fundamental building block of control systems in general and industrial control systems in particular. It consists of the process sensor, the controller function, and the final control element (FCE) which controls the process necessary to automatically adjust the value of a measured process variable (PV) to equal the value of a desired set-point (SP).
Controlling exposures to occupational hazards is considered the fundamental method of protecting workers. Traditionally, a hierarchy of controls has been used as a means of determining how to implement feasible and effective controls, which typically include elimination , substitution , engineering controls, administrative controls , and ...
The flow control into the tank would be cascaded off the level control. A further example is shown. If a control valve were used to hold level in a tank, the level controller would compare the equivalent reading of a level sensor to the level setpoint and determine whether more or less valve opening was necessary to keep the level constant.
Optimal control is a particular control technique in which the control signal optimizes a certain "cost index": for example, in the case of a satellite, the jet thrusts needed to bring it to desired trajectory that consume the least amount of fuel. Two optimal control design methods have been widely used in industrial applications, as it has ...