PLC-Based Machine Interlock System for PLS 2-GeV Storage Ring
Byoung R. Park, Jin W. LEE, and I. S. Ko
Pohang Accelerator Laboratory, POSTECH
Pohang, 790-784, Korea
system now works very well to meet our requirement.
The machine interlock system consists of two layers; thecentral PLC layer for data processing and the local PLC
layer for device scanning and control. Major machinecomponents under the supervision of the machine interlock
system include magnets, magnet power supplies, vacuum
devices, SR injection system, and RF system. Central PLC
system is based on GE- Fanuc-90/70 series PLC modules
and local PLC system is based on GE-Fanuc-90/70 series
PLC modules. Central PLC system is duplicated for faulttolerant operation. Data network called Genius-Bus
between central PLC system and local PLC system is also
duplicated. Local PLC units are distributed in local control
sheds around storage ring building for distributed control.
There is a large interlock status display panel in the main
control room to display major interlock status information.
It displays major subsystem interlock information such as
beam current, lifetime, subsystem interlock status, linacinterlock status, beam line interlock status, etc.
Application software is developed using Logic-master90
running on a PC. We can also monitor or debug themachine interlock system on-line by using Logic-master90.
The PC is linked with central PLC system via a RS232C
port.

Abstract
A machine interlock system (MIS) is developed for thePohang Light Source (PLS) 2-GeV storage ring and is used
to prevent machine components from undergoing damagesby abnormal machine conditions. The MIS consists of twolayers; central PLC layer for data processing and local PLC
layer for device scanning and control. The MIS is based on
GE-Fanuc-90/70 or 90/30 series programmable logic
controllers (PLC). There is a large interlock status display
panel in the main control room to display major interlock
status information. Application software is developed
using Logicmaster90 running on a PC.
1 Introduction
The Pohang Light Source (PLS) 2-GeV storage ring is athird-generation light source that has been under normal
operation for beam line users since September 1995[1].
We have developed a machine interlock system (MIS)
for the PLS 2-GeV storage ring to prevent machinecomponents from undergoing damages by abnormalmachine conditions. The field installation of interlock
system was completed in August 1994. After some modification and upgrade works during machine commissioning
period from September 1994 to July 1995, the interlock

Supervisor

Hot Standby
PWR

PWR

CPU GBC GBC

Mode Selection
Control PanelInterlock Status Display Panel

CPU GBC GBC CMM

S911

S911

RS-232C

Local PLC Unit #170
PWR BSM 70
I/O I/O
S911

Personal SafetyInterlock System

Computer
LM 90/70

Panel Controller Unit
PWR

CentralLayer

CPU CMM 30
S91 I/O
130I/O

30
I/O

30
I/O

30
I/O

30 30
I/O I/O

RS-232C
LM 90/30

Data Link(Genius Bus)

Main Control RoomSR Bldg. Local Control ShedLocal PLC Unit #3Local PLC Unit #2Local
Layer

PWR BSM 70 70
I/O I/O
S911

70
I/O

70
I/O

70 70
I/O I/OSCU

DeviceLayer

MPS

PWR BSM70 70
I/O I/O
S911

70
I/O

70
I/O

70
I/O

SCU

Devices &Equipments

SR Cell #12, 1, 2, 3 ,RF Bldg.,
Injector, Beam Line

MPS

Local PLC Unit #4
PWR BSM 70 70
I/O I/O
S911

70
I/O

70
I/O

70
I/O

SCU : Signal Conditioning Unit
BSM : Remote I/O Scanner
GBC : Genius Bus Controller
CMM : Communication Module
PWR : Power Supply
PSIS : Personal Safety Interlock System
MPS : Magnet Power Supply

SCU

Devices &Equipments

SR Cell #4, 5, 6, 7, 8,LCW, Beam LineMPS

Devices &Equipments

SR Cell #9, 10, 11,
MPS Bldg., Beam LineFig. 1: Configuration Diagram of Machine Interlock System for the PLS 2-GeV storage ring.

linked to a PLC unit via RS232C channel which controls
interlock status display panel. CMM711 module is used for
RS232C communication interface. The central PLC system
is placed in a small room next to the main control room.

2 System configuration and hardware
The machine interlock system (MIS) for the PLS 2-GeV
storage ring consists of two layers; central PLC system andlocal PLS system. There is a large interlock status display
panel that displays major machine interlock status
information. There is a PC used for application softwaredevelopment and on-line monitoring and control ofinterlock system. The overall system configuration
diagram is shown in Fig. 1.

2.2 Local PLC system
Local PLC system directly scans machine components
attached to it. It has various I/O modules to interface
machine components. It sends scanned data to central PLC
system via a data network called Genius-Bus. It also sends
out interlock signals to machine components according tocontrol data from central PLC system.
Local PLC system consists of 4 PLC units. These unit
are based on GE-Fanuc-90/70 series PLC modules. Each oflocal PLC units consists of a crate, a power supply module,
Genius-Bus interface module (BEM731) and some I/O
modules. Local PLC unit #1 is used for the control of asmall control panel in the main control room by which
operator can select operation mode of interlock system.
This unit is also interfaced to personal safety interlock
system (PSIS). PLC units #2 - #4 are placed in local
control sheds around storage ring building and directly
connected to machine components.

2.1 Central PLC system
Central PLC system gathers status information ofmachine components from local PLC system. If any abnormal condition exists, the central PLC system sends out
control data to local PLC system that actually generates
interlock signals to interlock machine components.
The central PLC system consists of two PLC units; mainunit and hot-standby unit. If main PLC unit is out of order,
hot standby unit takes over the role of the main one. Mainand hot-standby PLC units are implemented with GEFanuc-90/70 series PLC modules. The main PLC unit
consists of a crate, a power supply module, a CPU module(CPU-771), two Genus-Bus controller modules (BEM731),
and a communication module (CMM711). The central PLC
system is linked to local PLC system through a data
communication network called Genius-Bus. This network
is duplicated for fault tolerant operation. BEM731 module
is used for Genius-Bus interface. The central PLC unit is

2.3 Display panel system
There is a large interlock status display panel in the maincontrol room. The panel size is 2.2 meter high and 3.2
meter wide. This panel displays major interlock status
3200mmStatus Display Panel
West
Gate

2.0000Beam Energy

LR6GeV

Beam Current

200.250

Beam Life Time

#7

LR7mA

VAC
MPS
MAG

12 : 40hrs

LR5
#6

GV

GV

#5VAC
MPS
MAG

VAC
MPS
MAG

VAC
MPS
MAG IW2

LR8OPERATION MODE

LR4GVLR3IW1

INJECTION MODE
STORAGE MODESuperDoorGVNorth
Gate

StorageRingVAC
MPS
MAG#9VACUUM

RFBld.

VAC
MPSMAG

M P S

GVVAC
MPS
MAG RF

#10GV

L C W

VAC
MPS

#11#12LR11LR12LG B/LEastGate

Linear Accelerator
LW3LW2BSY

GUN
STARTLW4GUNGV

GV MAG

MD1 MD2 MD3 MD4 MD5 MD6 MD7 MD8 MD9 MD10 MD11MD12Fig. 2: Layout of Interlock Status Display Panel.

#1LR1SouthGate

VUV B/LLR2White B/L

VAC
MPS
MAG

IW3LR10INJECTOR

LW1NIM B/L

#2GV

F

#3VAC
MPSMAG

LR9LAMPTESTVACMPSMAG
GVMACHINE STATUS

R#4X-lay, EXAFS B/LVACMPSMAGGVmin#82200mm

SAXS B/LGVMIS Software Configration

Pause

SearchCall - Magnet

Injection

Call - Magnet

Storage

Call - Magnet

Call - Magnet

Call - MPS

Call - MPS

Call - MPS

Call - MPS

Call - PGM- Photon
Call - Chamber- Photon
Call - Chamber- Photon
Call - Chamber

Call - PGM

Call - PGM

Call - PGM

Call - BG
Call - BL
Call - RF
Call - LCW
Pause
INT-Chain

Call - BG

Call - BG

Call - BG

Call - IJ-MPS

Call - IJ-MPS

Call - BL

Call - BL

Call - BL

Call - RF

Call - RFCall - RF

Call - LCW

Call - LCW

Call - LCW

Storage
INT-Chain

SearchINT-Chain

Injection
INT-Chain

Fault Latch

Fault Latch

Fault Latch

Reset

MPS-INTMPS(#1 - #12 Cell,MPS BLDG.)
Gate Valve
PGM, BG
Injector
LCW

SR all Cell MPS- LCW status- each Cell Magnet- each Cell MPS
MPS BLDG. MPS- SR all Cell MPS- MPS Bldg. MPS- LCW status

RF
INT-Chain
Injector
INT-Chain
Gate Valve
close(by Vacuumfault)
SR Vacuum
Fault toBeam Line
Fault Latch

Fig. 3: Software Configuration.
information such as beam current, lifetime, subsysteminterlock status, linac interlock status, beam line interlockstatus, etc. The layout of interlock status display panel isshown in Fig. 2. This panel was built using small mosaic
graphic modules for easy panel layout modification andexpansion. There is a dedicated PLC controller unit for
display panel control. This unit gets needed display
information from central PLC system via a RS232C serial
communication port. This unit is implemented with GEFanuc-90/30 series modules. This unit consists of a crate, apower supply module, a CPU module (CPU311), a communication module (CMM311), and some I/O modules.
2.4 Development PC
We use Logicmaster90 software package running on aPC/Windows-95 to develop application software. This PC
is linked to central PLC system via RS232C communication link. We can also monitor and debug interlock
system on on-line using Logicmaster90.

Pause Mode

Search Mode

Normal Path

3 Software features
3.1 Application software
Application software consists of four blocks; PAUSE,SEARCH, INJECTION, STORAGE, MPS_INT, andRESET. The PAUSE block is activated in machine shutdown or maintenance period. It drives pause modeinterlock chain when abnormal machine conditions aredetected. The SEARCH block is activated during machine
search time. It drives search mode interlock chain. TheINJECTION block is activated during beam injection time.
This block drives injection mode interlock chain. The
STORAGR block is activated when machine is in beamstorage mode. It drives storage mode interlock chain. TheMPS_INT block is activated when one of PAUSE,SEARCH, and STORAGE blocks drives its interlockchain. The MPS_INT block actually drives interlock
signals related with magnet power supplies. The RESETblock clears up all interlock signals on pending.

Injection ModeInterlock PathFig. 4: Interlock System Mode Change Flow.

Storage Modeclear

ResetInterlock chain
preset1Cell Chamber Temp.
12Cell Chamber Temp.
1Cell Photon Stop Temp.
12Cell Photon Stop Temp.

Vacuum normal

1Cell Gate Valve Status
12Cell Gate Valve Status
1Cell PGM/BG Status
12Cell PGM/BG Status
1Cell Magnet Thermo.

Magnet normal

12Cell Magnet Thermo.
1 Cell MPS Statue

SR Ready

MPS normal

12 Cell MPS Statue
MPS BLDG. MPS Status

PSI station
RF normal

RF System Status
RF System Status(spare)

Beam Line station
LCW normal

Cooling Water (LCW)

Linac station

Front End #1
Front End #n

Front End safe

Septum MPS
Injection kicker MPS

Injector normal

Beam Line Ready
PSIS Ready
Linac Ready
Injection On

Injection Ready

Beam On

Fig. 5: Interlock Logic Flow for beam-on Condition.

Application software configuration is shown in Fig. 3.
3.2 Operation mode
The machine interlock system is operated in one of four
operation modes; pause, search, injection, and storage
modes. These modes are selected by the operator by using
a control panel placed in the main control room. The
operation mode flow of interlock system is shown in Fig.
4, and interlock logic flow for beam-on ready condition isshown in Fig. 5.
The pause mode is selected during machine shut-down ormaintenance time. If the pause mode says that the machine
is OK, the operator can select the search mode. If thesearch mode says the machine is OK, the injection modecan be selected. In this mode, the beam injection can bestarted. If desired beam current is stored in the storage
ring, the interlock system goes into storage mode.

4 Conclusion
A PLC-based machine interlock system for PLS 2-GeV
storage ring was developed. At initial operation stage, theinterlock system was somewhat unstable. To make thesystem stable, we made some software modification andadded some hardware modules. Now, the interlock systemshows very stable and reliable operational characteristics.
Acknowledgments
This work is supported by Ministry of Science andTechnology and Pohang Iron & Steel Co. , Korea.
References[1]I. S. Ko, et. al., "Control System of PLS 2-GeV
Storage Ring," in these proceedings.