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Figure 51. Real-time software and “soft real-time” interface structure
7.3.5
Motion Control
7.3.6
Slow Loops
Slow loops are non-time critical yet automated control loops. Using these automated control
loops can significantly reduce the burden on the AO system operator from constantly having
to monitor several items..
Some of these loops require outputs from the RTC. These signals within the RTC are
samples at a very high rate and so need to be low-pass “anti-alias” filtered in the RTC before
sending to offloading paths. If this is not possible or desirable in the first version of the RTC,
an alternative is to use the diagnostic stream data coming from the RTC, although this is less
desirable since it may be aliased.
7.3.6.1
Offloading telescope tracking and focus
Path F: Offload woofer to telescope
F.1 Offload to telescope tracking
F.1.1 Extract tip and tilt components of low-pass filtered woofer phase. Note:
these are in actuator space, so a linear transformation is needed to
determine the flat component of the mirror shape in phase space.
F.1.2 Rotate tip and tilt axes to align to telescope RA and Dec axes
F.1.3 Send offloading command to telescope controller (TELCO)
F.2 Offload to telescope focus (natural guide star mode only)
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