In cybernetics and

control theory Control theory is a field of mathematics that deals with the control of dynamical systems in engineered processes and machines. The objective is to develop a model or algorithm governing the application of system inputs to drive the system to a ...

, a setpoint (SP; also set point) is the desired or target value for an essential variable, or process value (PV) of a control system. Departure of such a variable from its setpoint is one basis for error-controlled regulation using negative feedback for automatic control.

Examples

Cruise control The SP-PV error can be used to return a system to its norm. An everyday example is the

cruise control Cruise control (also known as speed control, cruise command, autocruise, or tempomat) is a system that automatically controls the speed of a motor vehicle. The system is a servomechanism that takes over the throttle of the car to maintain a s ...

on a road vehicle; where external influences such as gradients cause speed changes (PV), and the driver also alters the desired set speed (SP). The automatic control algorithm restores the actual speed to the desired speed in the optimum way, without delay or overshoot, by altering the power output of the vehicle's engine. In this way the SP-PV error is used to control the PV so that it equals the SP. A widespread use of SP-PV error control is the

PID controller A proportional–integral–derivative controller (PID controller or three-term controller) is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuou ...

. Industrial applications Special consideration must be given for engineering applications. In industrial systems, physical or process restraints may limit the determined set point. For example, a reactor which operates more efficiently at higher temperatures may be rated to withstand 500°C. However, for safety reasons, the set point for the reactor temperature control loop would be well below this limit, even if this means the reactor is running less efficiently.

References

Classical control theory Control devices Control engineering Control loop theory Cybernetics Process engineering {{Tech-stub

Examples

See also

References