The Control System for the X-FEL Undulators

M. E. Bräuer 07.05.2005The Control System for the X-FEL Undulators

The Control System for the X-FEL Undulators

Martin E. Bräuer, DESY Hamburg, HASYLAB

Outline: • Requirements

and Concept• Components• Our Prototype• Measurements• Summary


Requirements and Concept

• synchronized gap movements• comprise the modular setup =>

cells• high reliability• allow complex movement-

schemes• movements with high dynamics• long-term availability of

components

Cell

Segment:• 4 synchronized motors• gap: ≤ 1µm precision• single-motor operation

(“taper”)• speed: (0,02 .. 20)mm/s• force: ≤ 160kN

Segment

cell i-1 cell i

Intersection

Intersection:• ≤ 5 control variables

(i.e.: position, current..)• value: f(gap) • synchronized: ≤ 10 µm

gap• cycle-time: ≤ 5 ms


.. complex movements

Various “patterns” need maximum flexibility !

Taper-mode:

Diagnostics: Have ≥1 device switched-on at a time

=> Move quickly (>30 devices in an undulator!)


Industrial Controls:• robust• productivity• fast markets (10y = an age !)• cheap• a huge market: O(200) German

companies &• safe

$/a91055

Secure investments:• Truly open standards (CANopen,

SERCOS, RS232, EtherCAT)• Vendor independent• Multi-Vendor environments

Industrial components


Motors

Stepper

• Rotating magnets

• Static coils

1/1 step

1/2 step

1/4 step

1/8 step

1/16 step

1/32 step

1/64 step

Stepper: Assume a rotor following

encoder

currentvelocityposition

Servo-controller

encoder

? ??

fieldbus

Servo: Measure the rotor angle

Synchron-Servo-Motor:

1kW !1€

• From the automation market

• 300 .. 1000000 W

• Cheap, robust, well understood


Encoder Systems

Measure the linear position of each axis=> The encoder determine the

accuracy/resolution

• Open, incremental encoders => reference-switch/mark needed

• Optical reading of a ribbon

• 20µm period length => sin,cos Signal @ 1Vpp

• Electronic “oversampling” (x4096) => linear “steps”

• Resolution: ok, precision?

• Operating them ‘close’ to a beam

• Singular point of precision

• Mounting?

• ULE (ZERODUR-like) mountings => compensate thermal deviations


Control-System

… …

cell i

high resolution encoder

motors

(multiturn) rotational encoder

local control CPU

(general network)

real-time network

coilsmotors (i.e. stepper)

I/O signals (fieldbus-devices in cell (opt.)Dezentral periphery

prec. analog out

(SERCOS drives for Intersection)

moto

r co

ntr

olle

r and a

mp

lifier

Intersection

Intersection not fully defined need maximal flexibility


Safety issues

• Needed feature in industrial solutions• Bus sensitive to many errors• Robustness (no false alarms required

(HERA!)• Additional measures allways possible

• Axis synchronization has a high priority in commercial systems

• “It is all software” Yes, get this from professionals!

• We have to define procedures• No problems found yet• Commissioning phase “interesting”• Have to foresee a indiv. Taper• Several devices will be used in Petra III

InterlocksPersonal-safetyRadiation safety

To be defined later..

Total:4x 132kW


The Protoype


Hardware Details

Terminals: IO and Intersection

12mm

CPU

Controller / amplifier

Power / safety

4x PWM output4x 0..10v (0.01% prec.)4x stepper (one mounted)


Measured Data: Precision Encoder vs. Motor 1

Rotor (incl. offset to get picture)

1 Axis and master (thin)

0.5µm tsample = 1ms

Time [s]

pos

= g

ap/2

[m

m]


Measured Data: Precision Encoder vs. Motor 2

Rotors (incl. offset to get picture)

4 Axis and master

50µm

150µm ! one bad spindle (known)

Encoders & servo-loops: loose requirements on mechanics


First stress tests

High precision – with

137mm ‘walk’

0.5µm

one axis

all axis


First stress tests

17x open/close cycleswith highest speed

0.5µm

v: 272mm in 12.5s


Summary

• First electro-mechanical prototype working

• System got up successfully (HarWi / MTU still there)

• Found a good supplier

• Measurements ongoing

• No showstoppers found yet

• The control system can be used rather widely

• >10x faster than Profibus• Based on ethernet• Existing (support/interest by >170 companies)• Open (fully documented)• Have only 1 bus !• > 50µs tasks with I/O, 12000 dig. IO in 350µs,

100 Servos-Axis in 100µs

OutlookNew fieldbus: EtherCAT:

The Control System for the X-FEL Undulators

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