资料介绍
Continuous processes have been controlled by
feedback loops since the late 1700’s. In 1788, James
Watt used a flyball governor on his steam engine to
regulate its speed. The Taylor Instrument Company
implemented the first fully functional Proportional,
Integral and Derivative (PID) controller in 1940.
Although feedback control has come a long way since
James Watt, the basic approach and system elements
have not changed. There are several elements within a
feedback system; for discussion purposes, we will use
a home heating temperature control system as our
model in the descriptions below.
• Plant – The physical heating and cooling parts of
the system.
• Sensors – The devices (thermistors measuring
temperature) that measure the variables within
the Plant.
• Setpoint – This is a value (i.e., 70 degrees),
which is converted to a voltage that the process
drives towards.
• Error Signal – This is the difference between the
response of the Plant and the desired response
(Setpoint). In a house, the thermostat may be set
to 70 degrees, but the temperature is actually
65 degrees, therefore resulting in an error of
5 degrees (Error = Setpoint – Measured). AN937
Implementing a PID Controller Using a PIC18 MCU
Author: Chris Valenti Disturbances
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