lbt sw workshop. tucson, 2-6 oct 2006 a. riccardi - the lbt adssec units1 the two lbt adaptive...

LBT SW workshop. Tucson, 2-6 Oct 2006

A. Riccardi - The LBT AdsSec units 1

The two LBT adaptive secondary units(LBT672a, LBT672b)

A. Riccardi, M. Xompero, L. Busoni, D ZanottiINAF-Osservatorio Astrofisico di Arcetri



LBT672 units in LBT

2x8.4m mirrors

Each AdSec:672 actuators911mm diam.



LBT672 layoutHexapod

Interface flange andstructural support

3 cooled electronicsboxes

Fixed hexapodCold-plate and

actuator supportAstatic levers

50mm thick Zerodurreference-plate

1.6mm thick deformableZerodur shell

Accelerometers



Current Status

at Microgate premises at ADS premises



Control electronics

Communication Board (1x backplane)

DSP control Board (14x backplane)

Reference Signal Generator Board (1x backplane)
















Liquid cooled crates, each comprehending 2 backplanes (3x)

Distribution boards

Actuators

Gap

Thin mirrorReference signal

Power

± 48V, 35 A

Real timecomm link2.9 Gbit/s

Daisy chain connection



Coil

3 cooled electronics boxes2 crates/box84 custom DSP boards2 DSP/board - 8 acts/board32-bit floating-point 470Mmac/s78 Gmac/s parallel computer -> WF reconstructor5.3 GB internal memory for diagnostic data storage (1.8min history at 1kHz)

Gigabit Ethernet SwitchDiagnostic communication linkTo the AOsupervisor 300Mbit/s



LBT672 connections within FLAO

AUXILIARY BATTERY 6U

POWER SUPPLY 9U

HEXAPOD CONTROLELECTRONICS 6U

3U

3U

ETHERNET SWITCH 2U

FIELD I/O 3U

GENERAL SWITCH 3U

HEXAPOD CABLES

HEXAPOD CABLES

FREE

42U

spider-armrack

Tel. p

ow

er

TCS

AO Supervisor

TCS

BCU of W-unit

LBT672crates

Hexapod

RT commConf/diag commPower Lines

Acc

ele

r.(5

00

Hz)

WFS

data

(m

ax

1kH

z)

Fast diag. m,p,f,etc(~100Hz)

Slow diag. T,V,etc (~1Hz)

Mode to offloadand alert level



LBT672 with multiple AO systems

Tel. p

ow

er

AUXILIARY BATTERY 6U

POWER SUPPLY 9U

HEXAPOD CONTROLELECTRONICS 6U

3U

3U

ETHERNET SWITCH 2U

FIELD I/O 3U

GENERAL SWITCH 3U

HEXAPOD CABLES

HEXAPOD CABLES

FREE

42U

TCS

AO Supervisor

TCS

BCU of W-unit

spider-armrack

LBT672crates

Hexapod

BCU of LBTI

BCU of NIRVANA

AO-selector BCU

RT commConf/diag commPower Lines



LBT672 as finite state machine

See CAN 486f007 and Lorenzo’s presentation



LBT672 in the FLAO SW structureAOSupervisor

Adaptive Secondary MirrorA0Arbitrator

Wavefront Sensor

IDLCORE

IDL Ctrl

AdsecArb

WFSArb

AOS

…

…

PSF

OSS

…

MirrDiagHARDWARE

FIRMWARE

TCS

WFSDiag

HARDWARE

FIRMWARE

HW CtrlHW Ctrl

See Xompero

See Busoni See Busoni

RT

com

m



Control electronics as WF Reconstructor

• Real-time reconstructor on-board:– W slopes modal reconstruction and filtering in <50us:

mt=A0st+…+Anst-n-B1t-1…Bmt-m

• Moreover:– Mode to actuator command computation: c=Mm– Actuator force computation– Actual position and force at steady state for each command

step (mean and rms value)• All above data are stored at 1kHz in circular buffers in the

internal memory for diagnostics (1.8min before wrap-around of buffers)

• AOSupervisor downloads the stored diagnostic data with decimation (~100Hz) to check behavior of AO loop and dangerous status of shell



Diagnostics in seeing limited mode

• In fixed (seeing limited) mode or when the loop is temporary opened a zero delta command is internally generated and triggered in order to keep the diagnostics running



Safety of the shall

• Hardware protection (<1ms response time) – Coils switched off when global power of actuator current driver goes

beyond a user defined threshold

• Software protection (1kHz) at firmware level.WFS slope vector is not applied when (notified to AOSupervisor):– Modes or delta_modes exceed a user defined threshold

– Same for actuator commands and delta_commands

– Same for actuator forces

• Software protection (5-10Hz). Coil switched off(?) when:– Max tensile stress is beyond a user define threshold (computed from

FEA model)

Shall is fragile! Needs diagnostics continuously run



Accelerometers issue

• Accelerometer signals are sampled by AdSec control electronics and TT is computed (~500Hz)

• Accelerometers have been designed for AdSec internal use. No full rate signal exportation (telemetry?) is currently possible. Decimation? Only spectral features? TBD

• TT signal from accelerometers is used as open-loop command for the tilt shell (added to optical tip-tilt WFS signal)

• As usual, Open Loop signals are affected by severe calibration issues. The level of effectiveness of the correction has not been tested yet.



Chopping issues

• Chopping sync/trigger signal is not yet defined• Measurements on P45 give: 5Hz with 90% duty cycle,

but…• Do not expect same AO settling time as for W:

– 5as PtV (±2.5as): 90um largest actuator gap:30um capsens blind region+10um AO stroke+50um Chop

– W operates with 70um gap: we measured <1ms settling time

– At 100um gap we measured 1.7ms settling time



See more in the following presentations

• See more details on AdSec functionality (in terms of finite state machine) from Lorenzo’s presentation

• See more details on AdSec diagnostics software implementation from Lorenzo’s presentation

• See more details on AdSec configuration, calibration and setting software from Marco’s presentation

lbt sw workshop. tucson, 2-6 oct 2006 a. riccardi - the lbt adssec units1 the two lbt adaptive...

Documents

x backplanedsp control

backplane communication

adsp control board

lbt adssec unitssafety

lbt adssec unitslbt672

lbt adssec unitslbt672

adsec control electronics

tbdtt signal