Post on 13-Jul-2020
FPGA implementation of a video-based system
for GNSS reception characterization along a
railway line
Rihab HMIDA
Fourth International Conference on Railway Technology: Research, Development and Maintenance
3-7 September 2018 | Sitges, Barcelona, Spain
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 2
Context and Goals
Presentation of the system architecture
Presentation of the embedded algorithm
Experiments and Discussion
Conclusion and Future works
Plan
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 3
Satellites transmit
The receiver on the train
receives
The train calculates its
position
The train sends its
position to the server
Global Navigation Satellite Systems
Train location is of main use in railway signaling applications. Currently, sensors are installed along the lines to detect the presence of a train.
However, in order to reduce the global cost of the system relying on balises – including maintenance, the use of Global Navigation Satellite Systems (GNSS) is investigated.
Context and Goals
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 4
Balise !
=> The longer term advantages of such an evolution would be to increase the frequency of the trains and to reduce the energy consumption, thanks to adapted algorithms that optimizes the speed of circulation with respect to the profile of the lines.
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Geographic Data base
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server
Context and Goals
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 5
The EU ERSAT GGC starting project intends to work on methodologies for the GNSS reception characterization of the lines in order to evaluate opportunities of virtual balises concept and its use efficiency.
In applications where high precision is required, the GNSS performance is not enough sufficient because of several errors (atmospheric, multipaths … etc.)
By using complementary sensors measures to aid GNSS positioning, the accuracy can be substantially improved.
Context and Goals
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 6
Context and Goals
Use of sky video recording system in addition to GNSS receiver
Limit the number and time of experimentation compaigns
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr
- Mutli-sensor fusion : use of low-cost, small size and flexible platforms which is a challenge in the next generation of navigation systems.
- Contribution : develop an embedded system that combines and merges different data sets around a novel architecture based on FPGA technology.
FPGA Platform allowing the control of the sensors,
acquisition, synchronization, processing and fusion of coming
data sets
Video Assist Monitor UART
HDMI
HDMI PPS
PC Monitor USB
Ublox GPS
Fish-eye camera
HW logics
SW program
Using FPGA-based system offer designers the maximum flexibility to customize system architecture. Co-designing software and hardware is also an option offered for parallel computation.
Presentation of the system architecture
7
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr
1- Received GNSS and HDMI data are recovered in pipeline and independently within the FPGA circuit to be treated. 2- GNSS data extraction and decoding module. 3- Synchronize received HDMI data with respect to the pulse per second (PPS) signal and GPS time.
8
FPGA circuit
HDMI data
GNSS data
Adaption and Transferring
Deserializing and Transferring
Decoding and Transferring
To SD card
Synchronize and Time-stamp
1 2
3
3
HDMI data 1
Adaption
Transferring
SW
HW
FPGA processing modules
Presentation of the system architecture
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
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- A UART receiver module is developed in VHDL. Serial coming data are collected by bytes, at 54MHz, using a FSM process.
- Video data transmission (PCLK, RGB, audio, synchronization) is performed using FPGA hardware resources. Communication channels (HPD, SDA, CEC, …etc) are performed via the embedded processor of the FPGA
1- Received GNSS and HDMI data are recovered in pipeline and independently within the FPGA circuit to be treated :
Presentation of the system architecture
FPGA processing modules
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 10
Receiver Protocol Specification
1- Received GNSS and HDMI data are recovered in pipeline and independently within the FPGA circuit to be treated. 2- GNSS data extraction and decoding module: Based on the Receiver Protocol Specification that describes GNSS frames contents, a processing diagram is defined to read, identify UBX frames and extract useful data. 3- Synchronize received HDMI data with respect to the pulse per second (PPS) signal and GPS time.
Presentation of the system architecture
FPGA processing modules
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 11
1- Received GNSS and HDMI data are recovered in pipeline and independently within the FPGA circuit to be treated. 2- GNSS data extraction and decoding module. 3- Synchronize received HDMI data with respect to the GPS time. At each PPS signal, a new GPS time is acquired and saved. An image acquisition delay ∆T is calculated using the FPGA clock. When a new image frame is detected, it is time-stamped with a combination of GPS time, image acquisition delay and the clock bias.
Presentation of the system architecture
FPGA processing modules
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr
3
12
1- Received GNSS and HDMI data are recovered in pipeline and independently within the FPGA circuit to be treated. 2- GNSS data extraction and decoding module. 3- Synchronize received HDMI data with respect to the pulse per second (PPS) signal and GPS time.
2
1
1
1
3
Sw
Presentation of the system architecture
FPGA HW/SW design
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 13
Presentation of the embedded algorithm
FPGA Design Flow Diagram
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
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GPS Ublox M8T RS232 output
Patch Antenna GPS Supply
(5V)
RS232 communication
FPGA Board Stratix IV GX
Board Supply (12V)
HDMI-RX and HDMI-TX interfaces
Fish-eye camera HDMI output
Alimentation caméra
Black Magic Recording system
HDMI input/output 2 x SD card (256 GB)
Experiments and Discussion
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
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Experiments and Discussion
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
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TIMEUTC : E2 07 07 0D 0D 39 12 Epoch Timestamp : 1531490242 Image Acquisition Delay : 5B 02 Clock Bias : 3C 06 µs
Delay = Hex2dec (5B 02) × 20 ns = 12,06 µs Clock Bias = 1596 µs
TIMEUTC : 2018/07/13 13:57:18 Hex2dec
Hex2dec
Hex2dec x clock Epoch Timestamp : 1531490242
Experiments and Discussion
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 17
1sec 2sec 3sec 4sec
13:57:18 13:57:19 13:57:20 13:57:21
Experiments and Discussion
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
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Identification LOS / NLOS
Image Classification
Place Satellites on Image
Enhance the precision of the train position based on LOS / NLOS signals classification
Experiments and Discussion
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 19
Interferences ?
Masking
Reflected signals ?
Optimal conditions of GNSS reception
ERSAT GGC ERTMS on SATELLITE Galileo Game Change
Multipath ?
Classify track areas as suitable or not for locating Virtual Balises
Experiments and Discussion
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr 20
The tool will be used in the ERSAT GGC project: Measures and data acquisitions are planned at the beginning of 2019 on train railway lines.
Conclusion
The prototype is almost finalized : lab tool compact and transportable system,
First experiments have been performed on July 2018 to test the system behavior under real environmental conditions,
Methodologies of data fusion and image analysis are post-processed in order to illustrate the potential of the tool,
Perspectives
Amelioration of the real-time recording system : image processing algorithm will be embedded on the FPGA circuit in order to calculate the train position during its running,
Institut français des sciences et technologies des transports, de l’aménagement et des réseaux
www.ifsttar.fr
Thank you for your attention
Rihab HMIDA
IFSTTAR
France
rihab.hmida@ifsttar.fr
www.ifsttar.fr