Pid Control Loop - MOGlabs ARF021 Manual

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6.2 PID control loop

ing circuit should be used to ensure that the signal fed into the
does not exceed the ±1 V modulation input tolerance, as
ARF/XRF
this can damage the input
For convenience, MOGL
( B3120 ) available as an optional extra, which provides:
1. Manual offset adjustment, ±10 V
2. Analog offset subtraction (e.g. from
3. Variable analog gain
4. Monitor outputs for both photodetector and error signals
5. Output protection, to prevent exceeding ±1 V.
6. 10 MHz bandwidth
The ARF/XRF implements the feedback control via a standard
(proportional integral differential) function:
( ) = G
where ( ) is the input error signal, ( ) is the feedback response,
and G is the overall modulation gain. The gain constants
are floating-point values in the range [0 1) which correspond to
proportional, integral and differential terms respectively. Typical
values are = 0 03
Earlier versions of the firmware also included a distinct "anti-windup"
gain, which has since been replaced by a saturating integrator for
simplicity.
When optimising a
achievable loop bandwidth is limited by the propagation delay of the
entire signal processing chain, not just the modulation bandwidth.
This includes the impulse response of the
signal-processing electronics, as well as the
ADCs .
abs produces a signal-conditioning board
( ) + G
0
0 8, = 0 01
PID control loop, it should be kept in mind that the
Chapter 6. PID stabilisation
DAC output)
(τ) τ + G
0 15 and = 0.
AOM , photodetector and
ARF/XRF .
PID