Delta MMC120 - Manual (Page 140)

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the wave guide as the pulse reaches the magnetic field of a magnet. The
twist takes time to be sensed at the transducer head. It is this time that is
measure by the controller board and it is proportional to the distance
between the transducer head and the magnet.
NOTE: Balluff and Temposonics rods are both MDTs whereas any
linear measurement device can be a LDT.
Open Loop Mode: The drive output is set to a value with out any corrective action taken
by the PID routine.
PID:Proportional Integral Derivative. A simple algorithm used by the motion controller
to reduce the error between the target and actual position, pressure, etc.
The three words of this acronym represent the three types of gains used for
controlling a system. See PID Loop below.
PID Loop:The process of repeatedly executing the PID routine
Error: = Target - Actual
E0: Current Error, Error for current Target and Actual
E1: Previous Error, Error for previous Target and Actual
U0: Current output
U1: Previous output
Kp: Proportional Gain
Ki: Integral Gain
Kd: Differential Gain
Proportional Term: U0p = Kp * E0
Integral Term: U0i = U1i + Ki * E0
Differential Term: U0d = ( E0 - E1 ) * Kd
The Sum is: U0 = U0p + U0i + U0d
The PID LOOP is:
DO FOREVER
WAIT FOR NEXT TIME PERIOD
READ ACTUAL FROM POSITION OR PRESSURE SENSOR
E0 = TARGET - ACTUAL
U0p = Kp * E0
U0i = U1i + Ki * E0
U0d = ( E0 - E1 ) * Kd
U0 = U0p + U0i + U0d
E1 = E0
CALCULATE NEXT TARGET POSITION
END