Design of Semi-Physical Fault Simulation Platform for Antarctic Telescopes
Shihai Yang*a,b, Yun Lia,b,c, Dandan Xua,b,c, Jiajia Wua,b,c a. National Astronomical Observatories/Nanjing Institute of Astronomical Optics&Technology
Chinese Academy of Sciences, 188 Bancang Street, Nanjing 210042, P. R. China b. Key Laboratory of Astronomical Optics & Technology, Nanjing Institute of Astronomical Optics & Technology c. University of Chinese Academy of Sciences, Beijing 100049, China
ABSTRACT
More and more astronomical instruments have been installed in Antarctica because of good seeing. Due to adverse circumstances, remote location and unattended, a high fault rate was found in these astronomical instruments in Antarctica. To ensure the reliable operation of these instruments is one of critical technology problems. This paper presents an experimental platform with semi-physical simulation technique for Antarctic Telescopes. The platform helps the research for fault detection, fault diagnosis method, fault handling and so on. It consists of fault simulation system and fault diagnosis and self-recovery system. Furthermore, the platform can be used as fault diagnosis unit for Antarctic telescope directly.
Figure 1. AST3-1 & AST3-2 in Dome A Figure 2. AST3-2 working in Dome A
More and more astronomical instruments have been installed in Antarctica because of good seeing. Dome A (the highest point on the Antarctic Plateau) is an excellent site for astronomical observation on earth, which would be as good as Dome C or even better[1-[3]. So far Antarctic Survey telescopes (AST3-1&AST3-2)[4], Chinese Small Telescope Array (CSTAR) have been installed at Kunlun Station shown in Fig.1. Large optical/infrared Antarctic telescopes are planned at home and abroad due to the excellent conditions for astronomical observation in Antarctic[2]. At the same time, auxiliary equipment has been installed in Dome A, such as automatic meteorological station, energy platform called PLATO-A[5], etc.
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Every coin has its two sides and Dome A is no exception. The natural conditions is very good for astronomical observation but it’s harsh for the astronomical instruments. It’s extremely cold there. The temperature in Dome A can reach -80℃. Dome A is a plateau at an altitude of 4096m. This means thin air and low air pressure.
Electronic devices, optical system and mechanical system are influenced by the extreme climate. For instance, sensors, computers, controllers and communication apparatus are sensitive to temperature and air pressure. The Antarctic telescopes are built on the ice and snow. As a result, the grounding resistance of the control system is large. Lacking of reliable grounding has serious negative effect on the anti-interference ability of the telescope. Antarctic is somewhat similar as space. Strong radiation and single-event upset effect can cause large scale integrated circuit dysfunction.
In short, due to the adverse circumstances, remote location and unattended, a high fault rate would be found in the large Antarctic astronomical telescopes.
Fault shutdown is unacceptable because the Antarctic telescopes are unattended in Dome A due to Kunlun station is not a perennial station for researchers in winter. The telescopes are maintained by Chinese Antarctic inland exploration team annually.
To ensure the reliable operation of the telescopes is one of critical technology problems because of the adverse circumstances.
So we have designed an experimental platform with semi-physical simulation technique for Antarctic Telescopes. The platform helps the research for fault detection, fault diagnosis, fault handling and so on. It consists of fault simulation system and fault diagnosis and self-recovery system. Furthermore, the platform can be used as fault diagnosis unit for Antarctic telescope directly. According to the experience comes from the Antarctic Survey Telescope-AST3, Chinese Small Telescope ARray for Antarctic Dome A-CSTAR and so on, the fault simulation system produces signals like faults or latent faults occur. The fault diagnosis and self-recovery system check and analysis the fault signals. At the same time, self-recovery technology can be used to recover the malfunctioning parts. In the fault diagnosis and self-recovery system, there is an evaluation system, which evaluates user’s method of fault diagnosis and self-recovery. The numerical evaluation values are saved in hard disk and shown on the screen. By this way, users can test his own method of fault diagnosis and self-recovery on the platform. The experimental platform is designed for the astronomical instruments at Dome A, especially for the 2.5m Antarctic telescope on anvil, which named KDUST[6], i.e. Kunlun Dark UniverSe Telescope. Undoubtedly, the experimental platform is valuable to other Antarctic instruments. The experimental platform has been completed and it is being debugged for the third telescope of AST3.The system is reliable and easy to operate.
2. DESIGN OF HARDWARE
Figure 3 shows the structure of the semi-physical fault simulation platform, which consists of fault simulation system and fault diagnosis and self-recovery system.
The fault simulation system is organized around the core of an Industrial PC and an UMAC (Universal Motion and Automation Controller). The hardware of the system also includes monitor, serial communication server, IO, relays, programmable power supplies, network switch, etc. Two modes of communication. One is Ethernet, the other is RS485. The computer is IPC-610H, which is made up of I7-2600 CPUs as the computing elements, using double full-switched Giga-Ethernet for its interconnection. One Ethernet port is used for the interconnection with devices, such as UMAC, programmable power supplies and sensors. The other is for the interconnection with fault diagnosis and self-recovery system. Using the Ethernet cable supplied, connect one end of the cable to the Ethernet port on the IPC and the other end to network switch (MOXA Nport5650-8-DT). IP sections are different for these two Ethernet ports. It should be noted that the RS485 protocol of sensors and programmable power supplies is translated to Ethernet protocol by a serial communication server, MOXA EDS-208A-M-ST-T. It can simplify the software and the flexibleness of access control is enhanced.
UMAC is a powerful computer made by Delta Tau. The UMAC Turbo is composed of a 3U-format Turbo PMAC2 CPU Board. The CPU is Motorola DSP 56303 and a set of accessory boards in 3U-format, all plugged in a common UBUS backplane and installed inside a 3U format rack. For example, the PMAC Accessory ACC-65E is a general-purpose input/output board, providing 24 lines of self-protected optically isolated inputs and 24 lines of self-protected optically
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isolated outputs. The PMAC Accessory ACC-28E is a 4-ch 16-bit analog to digital converter interface board and it provides a means for precision voltage measurement. The analog signal of position sensor, e.g. LVDT, is received and transformed to digital signal by ACC-28E. Furthermore, the position sensor faults of focusing and electromagnetic interference (EMI) will be simulated by using the card.
PCLD-885 is a 16-ch power relay board with 16 single-pole single-throw (SPST) relays. And the high-power relay handles up to 6A@250VAC. According to the command of UMAC, ACC-65E commands PCLD-885 to open or close, simulating many faults such as the positive over-travel limit of RA (right ascension), DEC (declination) and Focusing, the negative over-travel limit of RA, DEC and Focusing, short circuit, circuit break, and so on.
UMAC
Sensors
Data Acquisition Network
Motors
Fault Diagnosis and Self-recovery System Fault Simulation System
Mount Communication SystemAuxiliary EquipmentSoftware
RA DEC Focusing
Drivers
DefrostingCCD
warmerTemperature
ControlBlower Cameras Networks Serial Comms
Communication（Ethernet/RS485）
Communication（Ethernet/RS485）
Figure 3. The structure of the semi-physical fault simulation platform
The model of programmable power supplies is 4NIC-CK60（0~50V，60W）. The programmable power supplies are used to simulate the power faults of mirror defrosting system and temperature control system.
The fault diagnosis and self-recovery system is organized around the core of a ruggedized Industrial PC. The hardware of the system also includes monitor, serial communication server, IO, current and voltage sensors, inertial measurement unit, network switch, etc. Two modes of communication. One is Ethernet, the other is RS485. All devices meets the environmental specifications in Antarctic, e.g. operating temperature is -20℃ to 20℃ in cabinet and -80℃ to -40℃ outside.
The computer is FPC-7601 made by ARBOR, which is made up of I5-3320M (2.6GHZ) CPUs as the computing elements, using double full-switched Giga-Ethernet for its interconnection. And the operation temperature of the computer is -20℃~ 80℃.
The way of signal acquisition in the fault diagnosis and self-recovery system is the same as the way in the fault simulation system. The RS485 protocol of sensors and programmable power supplies is translated to Ethernet protocol
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by a serial communication server, MOXA EDS-208A-M-ST-T. It can simplify the software and the flexibleness of access control is enhanced.
Current and voltage sensors are used, including ZH-4062-14F3 (6-ch AC current sensor), ZH-4223-14F3 which is DC current and voltage sensor and ZH-40061-14F3 which is 6-ch AC voltage sensor. The total current of the fault diagnosis and self-recovery system, the current of programmable power supplies, the current of RA, the current of DEC and the current of blower are measured individually by ZH-4062-14F3. The total voltage of the fault diagnosis and self-recovery system, the voltage of programmable power supplies, the voltage of RA, the voltage of DEC and the voltage of blower are measured individually by ZH-40061-14F. The current and voltage of IPC, temperature control system, defrosting system and focusing system are measured by ZH-4223-14F3.
MW-MU500, i.e. inertial measurement unit, outputs the position of the telescope via RS485, including pitch angle, roll angle, yaw angle, three-dimensional accelerations and angular velocities. MW-MU500 is installed on the tube of the telescope, the signal of which is received by IPC. The abnormalities of position, angular velocity and acceleration will be detected by the inertial measurement unit. The fault diagnosis and self-recovery system can be used as fault detection device of Antarctic telescope. The data of the inertial measurement unit is an important reference to judge encoders of telescope and resolvers of motors.
There are two working modes for the semi-physical fault simulation platform. One is fault simulation mode, the other is true working mode on Antarctic telescope.
Mode 1 involves fault simulation system and fault diagnosis & self-recovery system. Fault simulation system and fault diagnosis & self-recovery system interconnect with each other via Ethernet and IO cables. The software of fault simulation and the software of fault diagnosis & self-recovery work at the same time. Mode 1 is used for the research of fault diagnosis, fault analysis and self-recovery.
Mode 2 involves fault diagnosis & self-recovery system only. A network cable connect the switch, EDS-208A-M-ST-T of fault diagnosis & self-recovery system to the switch of Antarctic telescope. And the fault simulation system don’t work anymore.
AMP
Electric control box
Power
XP1000
IPC
Fault diagnosis & self-recovery system
故障分析及无缝智能自愈系统
AMP
国家自然科学基金项目南极大口径望远镜潜隐故障预警及无缝智能自愈策略的研究
Keyboard
AMP
Electric control box
Power
XP1000
Fault simulation system
故障模拟系统
国家自然科学基金项目南极大口径望远镜潜隐故障预警及无缝智能自愈策略的研究
Keyboard
6
UMAC
Monitor
Switch
PDU
Monitor
PDU
AMP
Switch
IPC
Figure 4. The cabinets of the semi-physical fault simulation platform
Fault diagnosis & self-recovery system can be configured as two modes, i.e. self-recovery actively mode and no-recovery mode. In no-recovery mode, only fault analysis will be performed. In self-recovery actively mode, self-recovery will carry on actively based on fault analysis, using the researcher’s own algorithm. Furthermore, fault detection and
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fault analysis are evaluated by referring to the real faults’ explanation from the fault simulation system via Ethernet. And the effects of self-recovery can be evaluated too.
In mode 2, Fault diagnosis & self-recovery system works alone as the unit of fault handling for Antarctic telescope. The effects of self-recovery are evaluated based on the data collected after self-recovery is performed. And information is saved on the local hard disk as a TXT file, including time of fault detection, fault data, name and location of the fault, reasons of judgment, self-recovery or not, consuming time including self-recovery algorithm calculation and execution, data acquisition after self-recovery and the evaluation of self-recovery effects. At the same time, these messages are shown on the screen. These messages are sent back to the control center in China.
Figure 5. The photos of the real semi-physical fault simulation platform
In order to fulfill the functions above easily, the cabinets of the semi-physical fault simulation platform are designed as two solo cabinets, which are shown in Figure 4. And the photos of the real semi-physical fault simulation platform are shown in Figure 5.
3. SOFTWARE
Software of the semi-physical fault simulation platform can be used very flexibility and compatibility with fine human computer interaction. All data are acquired and analyzed on line automatically. The software can realize fault simulation, data collecting and memory, data or curve displaying, Ethernet/RS485 correspondence, initialization, etc.
Software of the semi-physical fault simulation platform consists of the fault simulation program which runs on the IPC of the fault simulation system, the fault diagnosis & self-recovery program which runs on the IPC of the fault diagnosis & self-recovery system, and the real-time executive program which runs on UMAC.
The fault data of the system comes from the experience of AST3-1 and AST3-2. According to user’s command, the fault simulation program produces fault signals and transmits them to the fault diagnosis & self-recovery program. The fault diagnosis system will analyze these signals and determine the fault type and location quickly and accurately. The reason and the solution of the fault are also obtained by searching the right match fault cause in the expert system knowledge database.
The flow diagram of the software of the semi-physical fault simulation platform is shown in Figure 6.
If self-recovery is needed, the system will command the controller to run programs and devices according to the solution. If there is no match fault cause in the expert system, the knowledge database can be updated real time. That’s means the expert system is extensible itself.
The expert system is made up of the parts as follows, knowledge database, inference engine, explanation facility and user interface.
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Common Fault Types
Telescope Fault
r Motor darlege
r Overload
r Excessive following error
r Hardware limo
r Poston sensor
Other Equipment
r Blower fault
r ITO low power
r mirror heating power
r mo0eorirg mmera
r To extend
computer/software
TCC crash
IPC crash
r Timer cant open
r Record time error
r I0.6/IO =2 no return
Communlaton
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r oaa exchange error
r Temperature module
r Irdium comnuniohon
'r Network congestion
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The software monitors the status of the telescope and alarms, if necessary. It collects signals by sensors and controller. Researchers can set thresholds for key items that, if crossed, could threaten the health of telescope. The system will alarm by light and sound.
Choice fault model
Implementing the algorithm of self-recovery
Initialization and Hardware self-inspection
Fault model 1 Fault model 2 Fault model NFault model N-1……Fault model 3
Fault feature extraction
Fault Simulation Program
End
Hardware and software work
Evaluating performance
Adding fault features
Adding fault types
Fault diagnosis & self-recovery program
Normal？
Y
N
Alarm
Figure 6. The flow diagram of the software of the semi-physical fault simulation platform
The interfaces of the semi-physical fault simulation platform are shown in Figure 7.
The fault simulation program and the fault diagnosis & self-recovery program are written by VS2010 combining SQL Server2005 database and based on Windows 7 OS. Windows 7 is not a real-time OS. So hard real-time control tasks are fulfilled by the real-time executive program which runs on UMAC. Software on upper computer is one level above program which runs on UMAC in the control hierarchy.
Figure 7. The interface of the semi-physical fault simulation platform
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4. CONCLUSIONS
An experimental platform with a semi-physical simulation technique is proposed and developed. The research achievements are shown as follows: An experimental platform with a semi-physical simulation technique is developed for the control system of Antarctic telescope, which consists of two systems, i.e. fault simulation system and fault diagnosis & self-healing system. Furthermore, the fault diagnosis & self-healing system can be used as fault diagnosis unit for Antarctic telescope directly. The platform helps the research for fault detection, fault diagnosis method, fault handling and so on. The experimental platform will benefit the future large Antarctic telescopes such as 2.5m Kunlun Dark Universe Survey Telescope (KDUST).
ACKNOWLEDGEMENTS
The authors are grateful for the support by the National Natural Science Foundation of China (Grant No. 11373052, Grant No. 11403065 and Grant No. 11190013) for their financial support. The authors are also grateful for the support by the National Basic Research Program of China (973 Program) (No. 2013CB834901).
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