Rooflink EN Archives

Simple balise reader for the measuring train

Project insights

The rail network is equipped with balises, i.e. magnetically coupled transponders, which are mounted between the rails of a track. Each of these has a unique identification number. An antenna under the locomotive excites the balise with a 27 MHz RF field, whereupon the balise returns the identification number at 4 MHz. The identification number is used to reliably localise the train for the ETCS train protection system.

Diagnostic train reads balises

To monitor and maintain the infrastructure, SBB uses diagnostic trains that record the condition of the tracks with various sensors and cameras. In addition to odometry and GPS, the balises are also used as fixed objects for locating the diagnostic data on the topology of the infrastructure, as they are entered in the database with their position. For this purpose, SBB has a handful of non-safety-related balise readers in use that are not connected to the train control system.

The balise readers currently in use cannot be reordered as the two current manufacturers of these devices no longer offer support and the devices are no longer in production. For reasons of cost-effectiveness and availability, a new balise reader should be developed that can be produced in a small series at a low price.

Reverse engineering

No documentation exists for the existing balise readers, which is why a supplier’s type was analysed by reverse engineering and compared with the specification of the Eurobalises. The key components are

a TX transmitter at 27.095 MHz as a telepower source, the exact power is unknown, but is around 3 to 5 watts due to the power consumption.
an RX amplifier with a low-pass filter (DC to 5MHz) with an attenuation of -50dB at 27MHz.
a duplexer to separate transmitter and receiver at the antenna.
a Software Defined Radio (SDR) to switch on the transmitter and demodulate the balise signal.
an industrial PC that decodes the signal.

Retrofit: Not just a copy

A retrofit should not only produce a copy, but also learn from the existing system. In the existing balise reader, for example, the transmitter is switched on and off via a USB-attached relay from the software, but could also be controlled directly via the SDR board. In addition, the SDR board is only used for sampling (and demodulation) of the received signals – the data is then decoded on the integrated PC. Many different supply voltages (+5V, +15V, -15V, 24V) are also used. The system architecture is quite complex and takes up valuable space in the measuring train (4U height units in a 19-inch rack).

The new system is to be significantly simplified:

TX control directly on the SDR board
Reduced number of supply voltages (amplifier not symmetrically supplied)
Decoding directly on the SDR board, without a separate PC

The new design has been reduced in size by a factor of 4 (to one height unit in a 19-inch rack) without making any relevant compromises in terms of functionality. Less complexity also means greater reliability and better maintainability.

New system design

In the new balise reader, the 27 MHz signal is generated directly in the SDR board and only amplified by the RF module. As the SDR board works with a clock frequency of 125 MHz, the harmonics are filtered out after the amplifier for a clean output signal.
The received signal is decoded directly in the SDR board. This means that the new system consists of just three essential elements: a power supply unit, the SDR board and the RF front end. The latter was customised for the balise reader.

RF front end

The TX, RX and duplexer paths are integrated in the RF front end. The picture (below) shows the TX path at the bottom and the RX path at the top. On the right is the connection for the antenna. The output power of 35dBm (3.2W) is sufficient to reliably read the balises. The power consumption of the RF module is 700mA/12V.

Software Defined Radio (SDR)

The SDR platform is based on a Red Pitaya board with 125MHz clock and a resolution of 14bit. It is equipped with a Xilinx Zynq 7010 FPGA. The operating system is a Yocto-based Linux with a U-Boot bootloader. Secure software updates are possible at any time via the web interface. The application (decoder) is written in Python3.
During the early development phase, various algorithms for demodulation and decoding were evaluated with the help of GNU Radio and a hardware-in-the-loop setup. In the finished product, the FPGA handles the computationally intensive demodulation, while the subsequent decoding is performed in the Python application.

Websocket application

The application is designed as a web socket server. Compared to an HTTP server, a web socket can also send data on its own when a connection is open without waiting for a new connection from the client. As soon as a balise is recognised, the server sends the identification number and a time stamp. Because the balise is detected several times during the crossing, it is possible to determine very precisely when the balise is in the centre under the reader. The accuracy (jitter) of the time stamp is better than 200 microseconds if the time is synchronised using the Network Time Protocol.

The new balise reader was implemented for SBB and integrated into the OpenTLS measurement application in the diagnostic vehicle. Thousands of balises are reliably read every day. The status or the live log can be called up via a web interface. And thanks to open source code, production data and IP rights, the availability of balise readers for SBB is now guaranteed.

Secure communication thanks to the V-ZUG PKI from SCS

Project insights

All IoT-capable household appliances produced by V-ZUG are equipped with a digital certificate. To make this possible, SCS has set up a public key infrastructure for V-ZUG.

The V-ZUG PKI developed by SCS is integrated into the production of V-ZUG’s IoT-enabled household appliances. As a result, all appliances are equipped with individual and harmonised digital certificates. This forms the basis for securing the appliances and their communication.

The V-ZUG PKI was also integrated into the internal IT landscape of V-ZUG AG. This includes the digital signing of new firmware versions for household appliances. The digital signature ensures that no counterfeit malware gets into circulation.

SCS carried out a proof of concept to ensure smooth project implementation and integration into the IT landscape. All important aspects of the project were checked in advance, thereby minimising the risks in the project.

As the V-ZUG PKI became a core component of the entire IT landscape, SCS developed a holistic security concept. In addition to technical security measures, this also included administrative issues for the operation of the V-ZUG PKI, a detailed authorisation concept and the development of secure work processes. Affected employees were trained by SCS on the basis of the developed security concept.

Overview of the commissioning of V-ZUG appliances in worldwide use. The IOT manufacturer, in this case V-ZUG, obtains a valid certificate from the PKI when manufacturing the appliance. The appliance is delivered with this digital certificate. Customers can put the V-ZUG appliance into operation and connect securely to the V-ZUG IoT cloud (V-ZUG Home).

The root certification authority (root CA) forms the centrepiece of the V-ZUG PKI. It is responsible for providing the digital certificates and digitally signing them. The Root CA was set up and secured in accordance with current security recommendations (based on security standards from ISO/IEC-27002). SCS also developed a concept for the secure storage of the Root CA.

SCS regularly checks the processes and carries out periodic audits of the systems, access authorisations and work processes.

In the event of an unforeseen event that affects the operation of the V-ZUG PKI, SCS has drawn up a disaster recovery plan. This emergency plan ensures that the V-ZUG PKI is up and running again in the shortest possible time.

Further advantages made possible by the V-ZUG PKI:

Value-added services can be activated on individual household appliances
Updates are secured by code signing
Service interfaces are activated for maintenance personnel in a targeted and time-limited manner

Detection of wheel faults with smart algorithms

RLC systems (wheel load checkpoints) measure the weight of passing vehicles as part of the train control equipment (ZKE). The signal curves are influenced by wheel faults. The signal curves can therefore not only be used to determine weight, but also indicate whether wheel faults are present.

In the first approach for determining a wheel error, an easily determined parameter (dynamic coefficient) is calculated from the signal curve of each wheel. If the dynamic coefficient is small, there is no wheel error and if the dynamic coefficient is large, there is a pronounced wheel error.

In the second approach, an algorithm developed by SCS detects flat spots and estimates their length. It utilises the fact that a typical signal curve results from a flat spot that occurs exactly above a sensor. The algorithm searches for this typical signal curve on the measurements. If one is found, it is analysed in more detail by the algorithm in order to estimate the length of the flat spot. To estimate the length, characteristic points must be determined on the signal curve.

In the third approach, the “unwinding” of the wheel is determined, i.e. the outside of the wheel and its condition are shown on a graph. This provides a condition of the wheel over the entire circumference and the individual defects on the tread are visualised. As the sensors on the RLC system do not cover the entire circumference of the wheel, additional sensors are used for processing. The algorithms developed by SCS process the measured data from the individual sensors and then combine them to produce the processing.

The three approaches allow existing wheel defects to be detected and analysed in more detail. Based on the analysis, a recommendation can then be issued for the refurbishment of vehicles with wheel defects.

Cover picture: Heitersberg [CC-BY-SA-4.0] via Wikimedia Commons (cropped)

Retrofits – fit for the future

Project insights

Supercomputing Systems AG has been observing the sub-optimal utilisation of resources in industry for some time now. In the case of electronic devices, from simple cooling units to locomotives, entire new systems regularly have to be procured due to individual outdated components.

In 2009, SCS implemented its first project to counter such partial obsolescence with a retrofit. Thanks to our modernised IT solution, it was no longer necessary to purchase a new complete solution. For public transport in the canton of Zug, it was decided to implement a retrofit instead of buying new ticket vending machines. This pioneering project at the time paved the way for numerous other projects, which a group of experts at SCS specialised in.

In the standard procedure, the system is completely rebuilt. All (partial) components have to be manufactured from scratch. As part of a retrofit, only those components that are no longer usable or require too much energy, for example, need to be replaced

Relevance

Coupled with the opening of the system and its interfaces for the owner and user, this has resulted in a disruptive business model. The original business model of vending machine suppliers with vendor lock-in has been replaced by a customer-orientated model. Access to the source code guarantees investment protection. In addition, further developments can be planned based on requirements and implemented more cost-effectively. This is possible for traffic light systems, lockers, airport infrastructure, railway technology and other industrial systems, for example. All of these infrastructure areas can benefit from retrofits and thus be made fit for the future with minimal investment. SCS is endeavouring to modernise further systems.

Previous implementations in Switzerland: SCS has carried out several retrofits in Switzerland: at tpg (Transport Publics Genevois) in Geneva, at vbl (Verkehrsbetriebe Luzern) in Lucerne and at ZVB (Zugerlandverkehrsbetriebe) in Zug.

Prices / Labels

SCS has received the following awards or labels for these projects:
2018: Swiss Dinno Award(https://www.swissdinno.ch/)
2020: Solar Impulse Efficient Solutions Label(Solar Impulse)

FPGA-based driver assistance systems

Project insights

The development of driver assistance systems, such as a lane departure warning system or traffic jam assistant, involves solving a wide range of problems. For example, the system must be taught to transform pixels into known objects (road surface, road markings, vehicles, pedestrians, etc.). The algorithms required for this are implemented as PC programmes by our customer’s technical experts for research purposes.

As the performance of modern processors and graphics cards was not sufficient at the time of the project to process the video image of an automotive camera in real time with the algorithm, the technical expert was unable to test the functionality of his algorithm in the moving test vehicle. Several such algorithms were implemented by SCS engineers in an FPGA and integrated on our suitable hardware platform. The resulting system enables real-time processing of the video images. In each case, the feasibility was first examined in a feasibility study in close cooperation with the customer’s technical experts and the realisation costs were determined.

SCS then carried out the implementation on FPGA. With the implementation on FPGA, the customer’s technical experts are able to execute their algorithms in the test vehicle in real time. They can combine them into a complete system and test them in real traffic situations. Project insight using the example of the Stixel algorithm: Processing video images on a pixel basis requires the algorithm to handle considerable amounts of data. The Stixel algorithm helps to reduce the amount of data: it summarises the pixels of an image column into “columns”, so-called stixels. It forms pixels from vertical surfaces (in vehicle rear ends, kerbs, …), flat surfaces (roadway, pavement, …) and background.

In addition to data reduction, an initial, rough grouping of the pixels into sub-objects is achieved. This algorithm is mathematically complex and correspondingly computationally intensive. As part of a feasibility study, SCS has succeeded in mapping the algorithm onto a streaming architecture for a low-cost FPGA. It was then implemented on the SCS FPGA box and integrated with other algorithms. Two automotive cameras can now be connected directly. The result, a Stixel image, is available via a network connection for display or further processing on a PC.

The FPGA box from SCS was one of the subsystems of the Mercedes-Benz S-Class INTELLIGENT DRIVE, which was the first car in the world to drive a 100km overland route completely autonomously in a pioneering achievement. The selected route leads from Mannheim through villages and small towns to Pforzheim and has historical significance: exactly 125 years earlier, Bertha Benz demonstrated the suitability of the patented Benz motorised carriage on the same route. The modern S-Class successfully mastered numerous difficult traffic situations.

Text and images provide an insight on the following website:
Pioneering achievement: Autonomous long-distance drive in rural and: Mercedes-Benz S-Class INTELLIGENT DRIVE drives autonomously in the tracks of Bertha Benz