The idea of an automated pantograph inspection system started in 2008 when Banedanmark, a Danish railroad infrastructure owner, needed a solution to address overhead wire teardowns. Image House started working on a prototype and installed it in Denmark two years later.
In 2013, Image House PantoInspect was founded as a separate company with a goal of improving the prototype to make it ready for export to other railroad infrastructure owners around the world.
The PantoSystem Concept
We install the PantoSystem above the rail tracks. Using the principles of laser triangulation, we can detect and measure any damage with millimeter precision. Several laser rangers measure the distance to the nearest object below the scanner at 30,000 times per second. When a train is below the scanner, it goes into an armed state, ready to fire a line laser. In that exact moment, the pantograph head is below the line laser, the line laser is activated, and the system takes several images of the pantograph head.
A train is usually travelling with a velocity between 50 km/h to 200 km/h. We designed the PantoSystem to work at any speed, which makes it easy for the customer to install at any site. A pantograph usually has two carbon strips to conduct electricity between the catenary wire and the pantograph. These carbon strips are typically 4 cm wide, so at 200 km/h the system has less than 1 ms to find the carbon strip and take several images before the pantograph has passed the scanner. Thus, the system must have a deterministic response time and low latency to record data at the exact time the pantograph is present.
The Initial Work
The first scanner used dedicated components (PCBs) to analyze the laser rangers distance data and send out a digital trigger signal to the line lasers and cameras. This worked well for the first prototype, but we soon realized that every installation site was different. In addition, many different types of pantographs exist. If we wanted to easily install the scanner and support a variety of customers, we needed a different solution.
The Compact Scanner: Going From Custom PCBs to a Configurable Single-Board RIO
Because every site is different, we constantly needed modifications to the PCB, which cost money and time. We chose the sbRIO-9607 from NI to replace the custom PCB. The sbRIO-9607 performs great in a small form factor. It comes equipped with the latest Xilinx Zynq processor so we can easily adjust the trig algorithm. This means we can use the same PantoSystem for all customers just by updating the FPGA code.
Developing the RIO Code
One challenge for a small company is the limited possibility of hiring experts in every field: Windows client written in C#, real-time condition in C, FPGA in VHDL, and more. Using Single-Board RIO, one person can complete the entire task without any knowledge of hardware description languages or placing and routing
tools. The host code is written in C#, so we had to determine how to communicate from the Single-Board RIO target to the host. We decided to use standard TCP/IP protocol, which is well defined in both LabVIEW and C#. We had this easy way to communicate with the Single-Board RIO, so we decided to send even more data and debug information to the host client. This was never possible with the original design. With all this new information, we could gain a deeper understanding of the special cases that led to incorrect trig times (and thus useless images). By analyzing the data, we could learn the noise patterns that vary depending on weather, and thus build up a more robust trig algorithm in the FPGA. The improved algorithm benefits existing customers, as we could easily deploy it remotely since it did not require psychical hardware changes.
Figure 3 shows a badly damaged pantograph spotted using the PantoSystem. The system generated an automated alarm, and the train operator lowered the pantograph and drove to the depot before any further damage happened.
The recorded data is sent to a remote server for image processing, which is one of PantoInspect’s core competences. We install PantoSystems in different outdoor environments around the world, where factors such as sun, shadows, rain, snow, and more, heavily affect the measurements. Based on years of experience, we have improved analysis to detect these environmental conditions, so we can compensate for them and thus obtain a millimeter-precise accuracy.
The NextGen Scanner: The New Feature
Powered by Single-Board RIO, it is possible to do firmware updates to the scanners. This means PantoInspect can sell service agreements, thus adding additional profit to the company while improving the system to the benefit of our customers.
The latest feature we introduced is a 3D scan of the carbon strip. This feature is only possible due to the strict timing in the FPGA, which we use to take multiple images of the line laser with several cameras and stitch them together to create a 3D image.
What Is Next?
Thanks to the flexible nature of the Single-Board RIO and the easy-to-use graphical development environment of LabVIEW, we are ready to deploy the PantoSystem to a wide range of customers. We just succeeded in installing the scanners in Germany and proved the system can be used for both trains and trucks. This opens up an entirely new business case, which uses the same hardware not only at different sites, but also for different applications.
With the introduction of the PantoSystem, PantoInspect significantly reduced the amount of overhead wire teardowns caused by bad pantographs. The PantoSystem has been a huge success, and we have already exported it to Australia, South Africa, and Germany. Thanks to NI products, we could deliver a high-tech product in a short time with a small team.
During a one-month test period, we verified that the system captures 99 percent of all passes correctly and analyzes 99.5 percent out of these correctly with no false alarms. These numbers are market leading, and one of the reasons why the PantoSystem has been widely adopted as the pantograph inspection solution.
Doyle, Shane; Bastucescu, Codruta and Vale, Tim.
"Pantograph condition monitoring system for automated maintenance inspections and prevention of overhead wiring tear downs"
In: CORE 2016: Maintaining the Momentum. Melbourne: Railway Technical Society of Australasia, 2016: 178-187.
Availability: <https://search.informit.com.au/documentSummary;dn=428761745848037;res=IELENG> ISBN: 9781922107800.
Alex Emil Munkhaus
Image House PantoInspect