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22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Diamond Light Source Beam Stabilization Feedback System
Mark Heron, Head of Control Systems
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Beam Stabilization Feedback System
• Describe Orbit Stabilization feedback system applied to Diamond Storage Ring – Requirements – Feedback Process– Feedback Controller– Communication Controller– Computation – Structure– Installation – Performance
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Requirements• Overall requirement
– To stabilise the electron beam in the SR to maximise photons on the experiment sample
• Detail requirements for Beam Stabilization Feedback System – For the photon beam position to be reproducible fill to fill of SR– To keep the photon beam stable on the sample – To keep the electron beam stable to better than 10% of dimensions in X
and Y and 10% opening angle
– Over a time scale of 10s mSec to days
mmx 3.121231.0 radradx 4.2241.0' mmy 6.04.61.0 radrady 4.041.0'
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Requirements
• Long term - Years/Months– Ground settling– Season changes
• Medium - Days/Hours– Sun and Moon– Day-night variations (thermal)– Rivers, rain, water table, wind– Synchrotron radiation– Refills and start-up– Sensor motion– Drift of electronics– Local machinery– Filling patterns
• Short - Minutes/Seconds– Ground vibrations
• Traffic, Earth quakes – Power supplies– Injectors– Insertion devices– Air conditioning– Refrigerators/compressors– Water cooling– Beam instabilities in general
• There are a number of ongoing beam disturbances to suppress
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Feedback Process
7 x X and 7 x Y per Cell ( Total of 336) BPM Positions (Sensors)
7x X and 7 x Y per Cell (Total of 336) Corrector Magnets (Actuators)
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Feedback Process• Orbit feedback is an example of a cross-directional control problem • Each sensor and actuator can be reasonably assumed to have the same
dynamics• The response the linear map from actuator effort to sensor position
Regulators [168]Vector
ProductΣ Σ
Vector BPM Setpoints [168]
Vector DC Setpoints [168]
Inverse Response Matrix
Accelerator
Vector of BPM Positions[168]
Vector of Corr Magnet
Values[168]
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Feedback Process
• Orbit Feedback is made up of three parts– Feedback algorithm
• Maintains required stability
– Communication Controller• Take data from 168 x 2 BPM monitors distributed over 561m to
Computation Nodes
– Computation Nodes for feedback algorithm• Calculate correction values in real-time• Write correction values to the power supplies for the magnets
• Realise the required performance sample rate Fs=10kHz– All of above in ~100usec
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Feedback Controller• Response Matrix maps from
actuators ( Corrector Magnets) to monitors (BPMs)
• For Feedback we need to go from monitors (BPMs) to actuators ( Corrector Magnets)
• Use Signal Value Decomposition of the Response Matrix to get the pseudo Inverse Responsive Matrix
• This is ill-conditioned hence increases sensitivity to BPMs noise. Apply regularization to scale the singular values in calculating the pseudo-inverse
• Regularized pseudo Inverse Responsive Matrix gives a robust map from monitors ( BPMs) to actuators (Corrector Magnets)
Response Matrix
Inverse Response Matrix
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
FOFB Latencies / Bandwidth
• Libera BPM Group delay of FIR: 148 µs• Libera BPM Group delay of 2 IIR: < 71 µs• Distribution of data around ring: 50 µs• DMA transfer to CPU: 49 µs• Conversion integer to float : 5 µs• Matrix multiplication 2*7*168: 4 µs• PID controller : 1 µs• Write into PS controller: 3 µs• Total: < 331 µs
• Magnet/chamber estimated to have 500 Hz BW• Bandwidth of PS controller currently limits loop
(set to 100Hz, but programmable)
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
• Measure the plant open loop characteristic– First order response plus delay
• At Ts= 100usec the delay ~4 x Ts
Orbit Feedback: Feedback Open Loop Response
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Feedback Controller• Use an Internal Model Controller (IMC) which uses a process model in
the feedback loop to remove process effects from the feedback loop• IMC gives a single parameter to optimise and leads to better
performance and robustness than the traditional controllers (PID) on systems with a delays.
• Built a model for SISO version of the system, plant model and gain controller
• Optimised for stability and robustness – Determined by Gain and Phase margins
Σ
Σ
ΣGc Controller
GPM Process Model
Gp Process
Y Output
Disturbance DU Input on Process
R Set Point
E Error
Internal Model Controller
_
_
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Communication Controller• Requirements for communications
– Move the data from 168 BPMs to the Computation nodes in deterministic time
• Performance– Time budget 50usec
• Reliability of data transfer– Cope with data loss, but can’t retransmit
• Resilience to loss of connection(s) or node(s)– Need to recover or resume operation from loss of nodes or
connections• Considered using standard product or protocols
– Reflective memory – MAC/IP/TCP/UDP don’ fit well with above
• Commercial solutions didn’t meet requirements hence designed the Communication Controller
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Communication Controller
• Each Node is connected to at least 2 other Nodes• At start of frame, a Node (Libera BPM unit) forwards its data on each link • All data received on any input link forwarded once on all outputs• Same basic design used inside Libera BPM and inside Computation Node receiver
• Low latency, high reliability communication network. • Utilise the available Xilinx FPGA Rocket IO interface on Libera BPM.• Designed a packet forwarding Communication Controller in VHDL
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Communication Controller
Packet payload (20 Bytes)
• 32 bit ID, time frame count, status, flags
• 32 bit x-Position [nm]
• 32 bit y-Position [nm]
• 32 bit BPM Sum
• 32 bit Time Stamp [nsec]
SOP 20 Bytes data CRC32 EOP idle
Packet Framing (10 Bytes)
• 16 bit SOP
• 32 bit CRC32
• 16 bit EOP
• 16 bit idle
Define communication packet 30 bytes
• Bit rate of 2.5Gbps gives link speed incl. 8b/10b = 250MB/s• Packet transmission time for 30 Byte @ 250MB/s = 120ns• Minimal total transmission time 2 planes (168 * 120nsec) = 20.16us
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Click to start Click to finish
BPM 1 DATA
COMPUTE NODEALL BPM DATA
BPM 2 DATA BPM 3 DATA BPM 4 DATA
COMPUTE NODEALL BPM DATA
Communication Frame No 1
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Communication Frame No 2
Click to start Click to finish
COMPUTE NODEALL BPM DATA
COMPUTE NODEALL BPM DATA
BPM 1 DATA BPM 2 DATA BPM 3 DATA BPM 4 DATA
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Click to start Click to finish
COMPUTE NODEALL BPM DATA
COMPUTE NODEALL BPM DATA
Communication Frame No 3
BPM 1 DATA BPM 2 DATA BPM 3 DATA BPM 4 DATA
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Click to start Click to finish
COMPUTE NODEALL BPM DATA
COMPUTE NODEALL BPM DATA
Communication Frame No 4
BPM 1 DATA BPM 2 DATA BPM 3 DATA BPM 4 DATA
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Communication Controller
Computation Node
BPM MonitorsOne Cell
• Actual network is connected as Torus• Data distribution < 40usec • Robust to loss of link(s) or node(s)
– With loss of links or nodes the propagation delay increases but with 50usec budget .
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Computation• Data move from Communication Controller interface into
processor memory • Computation aspects breaks down into 3 parts
– Mapping from monitor to actuator space • Matrix multiplication
– Appling the IMC regulator• Realised as a 5th order IIR on each of 168 x 2 actuator inputs
• Multiply accumulate – Appling rate of change limiter and bounds checking to
preserve the beam and enable smooth starting and stopping
• Logic and arithmetic • Data move from processor to Power Supplies.
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Computation•Use MVME5500 for embeded VME Systems
•Features– 1GHz MHz MPC7455 PowerPC Processor– Cache 32K L1, 256K L2, 2 MB L3– Gigabit Ethernet and Fast Ethernet Port
– Two PCI 64-bit/66 MHz PMC-Sockets •To interface Communication Controller
•AltiVec Coprocessor – Fixed-length vector operation– Single Instruction Multiple Data– Optimized for digital signal processing
•Multiply, Multiply-accumulate– 2.2 Gigaflops/sec
•Use VxWorks as RTOS
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Computation
168
168
CorrectorsInverse Response
Matrix BPM
= *
168
7
CorrectorsSub Matrix of Inverse
Response Matrix BPM
= *
• Using AltiVec processor – Full Response Matrix x2
multiplication take 96 usec
• Partition the problem– Calculate 1/24th of the corrector
values ie one Cells worth in 4usec
– Regulation takes 1usec on PPC processor
• But requires 24 processors boards – Fits well with the distributed
nature of the problem
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Pro
cess
or
Controls Network
PS VME crate
eBPM eBPM eBPM eBPM eBPM eBPM eBPM
Cell -m
Cell -n Cell +n
Cell +m
Orbit Feedback: Structure (one of 24 cells)
14 Corrector PSUs
PSU 1 PSU 14
PS
U I
F
PS
U I
F…
Event Network
FB
Pro
cess
or
PM
C R
ock
et
IO
Eve
nt
Rx
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Installation (one of 24 cells)
Computation Node
Corrector power supplies
BPM Monitors
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Controller Performance
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Performance
60mA
Suppressionof beam motion
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Orbit Feedback: Performance
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Communications Controller Availability
• The Diamond Communication controller is now being used on Soleil, Delta and ESRF
• Its available from Diamond (without support) or from ITech as an option on the Libera BPM with commercail support
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Acknowledgement
• This is the work of many people. • Including Diamond Control Systems Group, Steven Duncan (Oxford
University), Leo Breuss (Super Computing Systems) and others.
22/4/2009 Mark Heron
Diamond Light Source Beam Stabilization Feedback System
Questions?