Rev E Mar 2022
Page 18
Chapter 3 Installation
3.9 Controller Schematic Diagram
The PPC001 controller and PFM450 focus mount is a closed-loop position control
system with a digital PID controller and dual notch filters. The PFM450 actuator
contains a capacitive position sensor for accurate position measurement. The sensor
is driven from a sine wave generator, the AC output signal of the actuator is
demodulated and sampled by a precision 18 bit A/D converter. The output from the
capacitive sensor is linearized in the digital domain and for maximum accuracy the
linearizing curve is individually matched to the sensor. The setpoint position is
maintained by a PID controller whose coefficients can be tuned to optimize system
response. The PID controller is followed by a dual notch filter that, when enabled,
dampens the natural mechanical resonance exhibitied by the mass and elasticity of
the actuator.
Fig. 3.8 System Schematic - Part 1
PFM500
Synchronous
Demodulator
EXT IN BNC
EXT OUT BNC
18 bit ADC
24 bit ADC
20 bit DAC
24 bit ADC
18 bit DAC
Low-pass
Filter
Divide by 15
Sine Wave
Generator
To Linearization
See Fig 3.6
From Open/Closed Loop
see Fig. 3.6
High voltage amplifier
-30 to +150 V
