lhc collimators motor drive control & position readout and survey

LHC Collimators Motor Drive control &

Position Readout and survey

AB/ATB/LPE 8/11/2006

R. Losito, AB/ATB - Collimators Controls Review, 18/12/2006

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OUTLINE

Collimators’ requirements Motor movements Position Readout and Survey

PXI and Alternatives Motor Drive Control Position Readout

Conclusions


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The Collimator Control Architecture


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OUTLINE



Conclusions


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Collimators’ requirements

Motor Drive Control The jaws of the collimators are moved by

stepping motors, to ensure repeatability of the movement within the uncertainty defined by the mechanical play.

Mechanical play has been measured to be below 30 µm on all the collimators received so far.

Cumulated error due to mech. play to be compensated by either re-alignment to position sensor reading or by step-counter reset on home position (mechanical end-stop)


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Collimators’ requirements Motor Drive Control

Each jaw is moved by two motors. The two jaw supporting shafts are rigidly connected to

the jaw. Skew movements are executed by (slightly) deforming

the structure of the jaw. It is recommendable (for a number of reasons) to

synchronize as much as possible the two axes. Qualitatively we verified a very different vibration

regime from no synchronisation (> msec: lot of noise) to good synchronisation (~0.1 msec: no noise at all)

11stst requirement requirement: synchronisation of two motors of the same jaw better than 1 msec


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Motor Drive Control Jaws’ positions need to be controlled at 20

µm level (if possible)

At 2 mm/sec, 20 µm 10 msec.

Synchronisation across the different collimators is implemented by CSS, that sends triggers to each MDC (no CERN timing card required in low-level).

Local or external accurate clock is required to keep the jaws synchronised in between two triggers.


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Motor Drive Control

Trigger delay

Start jitter

Profile duration

Stop jitter

Trigger delay: <1ms

Start jitter: <1ms

Stop jitter: <10ms

Profile duration: ~15÷30 minutes

Provided by CSS and daisy chained on different LLFE (jitter < 1 µsec)Determined by platform chosen.

Determined by local clock


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Motor Drive Control: additional feature Movement during phases of acceleration will

be driven through functions sent by the CSS

The MDC will have to be able to execute profiles of movement with a duration up to 30 minutes (max delay between two successive triggers sent to CSS).

The MDC shall be able to download a new profile from the CSS while still executing another profile


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Motor Drive Control : Summary Synchronisation within same jaw: <1 msec

Synchronisation from jaw to jaw, all along the movement function: < 10 msec

The MDC shall be able to download a new profile from the CSS while still executing another profile


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OUTLINE



Conclusions


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Collimators’ requirements Position Readout and Survey

It is required to read and transmit the position of each position sensor (LVDT) at a rate of 50 Hz (minimum) or 100 Hz (wish).

The function of position sensors is SAFETY. The PRS will raise an interlock in case the collimator position goes too far for example during automatic Beam based alignment.

Position to be compared with Limit Function managed through MCS

That gives 10 ms to read the signals, clean them from noise, calculate the position, compare it with the limit function and raise the interlock.


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Acquisition speed: At 250 kS/sec (16 bits), and 1000

point acquired, reading 1 channel takes 4 msec.

Each PRS has a minimum of 28 channels to read (for LVDTs).

Simultaneous sampling (no MUX) is therefore mandatory to keep 100 Hz (or even 50)!!!


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Position Readout and Survey Summary

~250 kS/sec (16 bits)

Simultaneous sampling


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OUTLINE



Conclusions


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PXI and Alternatives

PXI OPEN Industrial standard governed by a

consortium of ~70 companies, lead by National Instruments but including bigs like Keithley, Rohde & Schwarz, Agilent.

Countless applications in Industry, Scientific institutions (NASA, ESA, ESO…), Military (control of helicopters), and for control of Nuclear plants.

Used at CERN for Magnet testing (SM18), no use (to my knowledge) for accelerator controls


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PXI


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PXI Triggering with 1 ns skew

Internal clock (10 MHz) stability down to 45 ppb

High data rate: 132 MB/s, we need less than 1

High reliability backplane connectors (Compact PCI).

Compatibility with new PCI Express standard (giving up to 6 GB/s data rate and high frequency clocks > 20 MHz).


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PXI : Generic configuration 2 x 8 slot chassis for 1 (few cases), 2 (90% of

the installation) or 3 collimators (point 3).

3 collimators x chassis is going to be very challenging because of the reduced space in the available racks. Even if investment cost would be lower, maintenance would be a nightmare.

PXI n. 1 : Motor Drive Controls: Motor control, resolvers, end stroke switches,

interlocks, trigger

PXI n. 2: Position Readout and Survey LVDTs, Interlocks, trigger.


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PXI : Motor Drive control Based on FPGA.

1 FPGA x collimator (Motor and resolver). Very practical to port the configuration among 1, 2 or 3 collimators per chassis.

FPGA provides speed (reacts and executes commands within 80 µsec) and reliability. Should we need further functionalities in the future we just reprogram it.


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PXI : Position readout and Survey Generation of sinusoids at different

frequency. Probably based on FPGA (if not, standard DAQ,

which absorbs more CPU resources)

LVDT reading ADC, algorithm and comparison to limit function in

the CPU.


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PXI and Alternatives PXI : CPU

Based on 2 GHz INTEL Core DUO T2500 Dual core processor

2 Gbytes RAM

1 Gbyte Solid State disk (instead of hard disk)

Possibility of remote software reboot.

OS: Pharlap

Language: Labview RT


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MTBF

NI Model MTBF (hours) MTBF (years) Temperature Prediction Model

5000 hours

8 Slot PXI -1042 112573 22.5 25 Bellcore I ssue Level I I

NI PXI 8196RT 124400 24.9 25 Bellcore I ssue Level I I

NI PXI 7833R 301262 60.3 25 Bellcore I ssue 6

NI 9425 1256699 251.3 25 Bellcore I ssue Level I I



NI 9476 4594340 918.9 -40 Bellcore I ssue Level I I

PXI 6653 577156 115.4 25 Bellcore I ssue Level I I


cRI O 9263 397584 79.5 70 Bellcore I ssue Level I I

cRI O 9263 1732619 346.5 25 Bellcore I ssue Level I I

cRI O 9263 5064634 1012.9 -40 Bellcore I ssue Level I I



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PXI : FESA

No solution available to run it on Pharlap.

With the help of Clara Gaspar (PH) and the support of National Instruments we succeeded to compile DIM under Pharlap and LynxOs.

DIM Server runs on PXI, Client on LynxOs.

IT/CO supports DIM for the experiments.

National Instruments agreed to support DIM under Pharlap (or any future OS) for 20 years.

NI solution (“shared variable”) to publish data under Linux to be available in March 2007. If fast enough we can get rid of DIM. FESA Gateway (and CSS) will have to run under Linux.


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PXI : FESA

Latency: ~6 ms

PXI

MDC or PRS(Labview RT)

DIM Server

PC Gateway: Linux or LynxOS

CSS DIM ClientFESA Server


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PXI : FESA

Latency : ? (to be measured in March)

PXI


Shared Variable Server

PC Gateway: Linux

CSSShared

Variable client

FESA Server


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VME : FESA

Latency : ~ 6 ms

PXI


FESA Server

PC Gateway: Linux or LynxOs

CSS FESA Client


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VME: Motor controller:

Delta-τau (USA): up to 16 axes

Analog Input: ICS (USA): 32 channels, 24 bits at 100kS/S

simultaneous sampling.

Proof of principle done (it works).

It’s more expensive, less flexible (we cannot re-program the motor controller if needed)

Slower ( no 100 Hz).

Implies manpower from CO (Drivers).


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VME: Measured Performance

Stepping motor Controller 12 axis

Trigger delay 0.44 ms

Start Jitter 0.44 ms

Stop Jitter 0.44 ms an external 100 kHz reference clock is needed (to be provided by CSS). Clock integrity in daisy chain?

CPU RIO 3 Positioning monitor frequency 50 Hz with 14 LVDTs (2 collimators)

FESA Commands transfer rate ~6 ms average updating time (to be confirmed)

Data Acquisition transfer rate (under measurement)



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PXI: Measured Performances

FPGA card Trigger delay 80 us

Start Jitter Few us

Stop Jitter 30 us after 20 minutes profile

CPU PIV 2.0 Ghz

Positioning monitor frequency

At least 100 Hz with 14 LVDTs (2 collimators) and with the LVDT signals processing in the system

DIM-FESA gateway

Commands transfer rate 6 ms average updating time with 100 bytes command

Data Acquisition transfer rate

2 ms average updating time with 1000 bytes data block



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Name Features Price [EUR]

Crate (x2)

ELMA, System 11, 7U 19” x 7U x 290mm, 12 slots

6’150.-

CPU (x2)

CES, RIO3 Low-cost PowerPC 8’900.-

AI ICS-110BL-32 32ch x 108kHz 10’470.-

AO ICS-115-16 16ch x 100kHz 8’290.-

Controller

Delta Tau, Turbo PMAC2

12 AxisTrigger delay = 0.44ms

6’430.-

Total 46’670.- Eur/CHF: 1.56 Total = 72’805 CHF x 2 coll. Phase 1 = 54 systems: 3.93 MCHF Problem 14U !!!!


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PXI :

For 54 systems (2 PXI x 2 Collimators) cost is ~2.5 MCHF (~41000 CHF x 2 coll.)

Cost is therefore 63% of VME

This price includes also cables, Patch panels and optocoupled fan-outs (not included in VME slides)


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PXI : Drawbacks

PROBLEM Strategy

Not a standard AB/CO hardware

Long term (20 years) support negotiated with NI. Open standard. Backward compatibility of new NI hardware. OS update not more than once / ~5 years

No AB/CO supported solution to install FESA on Pharlap

DIM

Shared variable


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PXI Solution VME Solution

Motion Synchronization Few tens us <1 msMotion Trigger Delay 84 us 0.44 msTuning: motion commands updating time

10÷20 ms 5 ÷10 ms

Position survey frequency > 100 Hz > 50 HzReliability No experience New cards used

Space requirements Very compact solution We have to buy special VME crate 400 mm deep

Drawbacks Not supported by AB/CO

New cards not supported by AB/CO

Price for 2 coll. ~45000 CHF >72000 CHF

Purchasing time Approved by Finance Committee

market survey



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Conclusions

Specificity of the LL control system is a direct consequence of tight specifications (high accuracy, high speed, synchronisation).

PXI flexible, cheap and reliable No known experience in accelerator

operation. Known problems identified and solved. SPS

test confirmed robustness of the system VME alternative solution exist, but 40%

more expensive.

lhc collimators motor drive control & position readout and survey

Documents

different collimators

synchronisation msec

mechanical play

good synchronisation

lot of noise

different vibration

cern timing card

external accurate clock