28176 Parallax Inc, 28176 Datasheet - Page 258

• Manufacturer Part Number: 28176
• Description: KIT PARTS PROCESS CONTROL W/TEXT
• Manufacturer: Parallax Inc

Specifications of 28176

• Accessory Type: Process Control
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: BASIC Stamp® 2 and Board of Education
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

well as the driving conditions.
chapter.
Conditions (or disturbances on our system) can change very rapidly; such as when the car
suddenly encounters a hill. Or may be very slow; such as tire wear reducing efficiency.
PID control can measure and take action on:
The sum of these three evaluations comprises the output drive in an attempt to maintain a
system in equilibrium. Figure 8-1 illustrates the evaluation and control of a system for
PID control.
The classic PID formula for calculating the controller output is as follows:
or
Where:
*(Earlier E was used for Energy. Symbols have multiple uses).
1. How far from the setpoint a system is, or the magnitude of the error.
2. The duration for which an error remains.
3. How quickly an error occurs in the system, or the "rate" of change.
DRIVE
Co = controller output or drive
Bias = User defined drive
E = Amount of Error*
t= Time
K
K
K
dE = Change in error
dt = Change in time
Co
P
I
D
= integral gain
PID
= proportional gain
= derivative gain
=
TOTAL
Bias
= DRIVE
+
K
P
E
+
BIAS
K
I
Keep this example in mind as you continue through this
+ DRIVE
∫
Edt
+
K
PROPORTIONAL
D
dE
dt
+ DRIVE
INTEGRAL
+ DRIVE
DERIVATIVE