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Vodafone Group Research and Development Accelerates Development of Onboard Road Usage Charging System
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Global positioning satellite (GPS) technology has enabled governments to implement improved methods of collecting tolls for road usage. Today, onboard systems equipped with GPS receivers can automatically determine the exact location of a vehicle and determine if it is traveling on a road or in a region that requires a toll.
Vodafone Group Research and Development has a successful track record in the area, developing and delivering road usage charging applications for more than ten years. They use MathWorks tools for Model-Based Design to develop highly accurate road usage charging applications that can be implemented on a range of target platforms.
"MathWorks tools for Model-Based Design enable us to simulate each step of the process, which ensures higher design quality and more confident, better-informed design decisions," explains Christian Birle, senior technology manager at Vodafone Group "And, generating code from a single model enables us to port the solution to various hardware targets with less effort and time."
Challenge
Vodafone’s road usage charging application needed to meet the requirements of the European Committee for Standardization for a pan-European interoperable solution as well as for regional service providers. Road usage charging requires precise location of the vehicle in relation to chargeable areas or sectors.
The onboard unit (OBU) uses a GPS receiver to determine the position and speed of the vehicle. The system also includes a GSM/GPRS module for communication, a smart card reader, and a database with geographical information.
Vodafone required a development environment to design, model, and simulate the entire system before generating embedded code for the OBU. After implementing six different hardware platforms in the past ten years to address evolving system needs, Vodafone needed to easily adapt their solution to different hardware platforms.
"With Simulink and Real-Time Workshop Embedded Coder, we design complex real-world applications and generate efficient embedded code for a complete stand-alone system."Christian Birle,
Vodafone
Solution
Using MathWorks tools for Model-Based Design, Vodafone designed a complete road usage charging application and automatically generated and deployed code onto an ARM7 32-bit microprocessor in an automotive supplier’s OBU.
The team first used Simulink to develop a central model that included linked modules for control, human/machine interface, communications, GPS preprocessing, route identification, and data logging. Independent teams worked on the various subsystems and accessed the version control capabilities of RCS directly from Simulink.
During the system design phase, the team used a standard PC running Simulink and Stateflow to design, simulate, and debug their control algorithms, meeting the system’s technical requirements.
Vodafone engineers used Stateflow to develop an event-driven control flow for each module in the system, such as a route identification module that identifies all motorway sections correlated to incoming GPS positions.
They tested the algorithms on the same PC, which served as a rapid prototyping target to verify functionality of the controller model in a real environment.
Vodafone engineers equipped their PCs with a GPS receiver, a mobile phone, and a smart card reader connected via serial ports. They wrote S-function device drivers to connect each device as a block within the Simulink model. They ran hardware-in-the-loop simulations to conduct their first road tests, which enabled them to verify and prove system functionality.
The team used Real-Time Workshop Embedded Coder to automatically generate C code for the OBU. They also used Real-Time Workshop Embedded Coder to specify parameters, such as stack size and debugging level, further refining and tuning the system for the embedded target.
Finally, they downloaded the executable code to the ARM7 system.
"Real-Time Workshop Embedded Coder generated C code that was error-free and efficient—so much so that our team only needed to write code for our device drivers," reports Dr. Christian Robl, system architect at Vodafone Group R&D.
Currently, the system is undergoing a one-year trial test in 50 vehicles.
Results
- Hardware-independent solution delivered. "With Simulink, the final application model can be mapped to different targets without modification, providing a central source for the entire system design and avoiding the overhead of synchronizing different models with different targets," says Birle.
- 100% recognition rate achieved. During the first simulated tests of the application, a 96.9 percent recognition rate was achieved. After improving the geographical data and fixing minor modeling errors, the second test resulted in 99.3 percent recognition rate. The final round of improvements yielded 100 percent accurate charging in simulation, which Vodafone confirmed with several onsite field tests.
- Development time reduced by months. Vodafone developed the complete road usage charging software on the OBU in just 12 months compared to an estimated 18 months. "Simulating and implementing with the same model enables algorithm changes for extensions or bug fixes to be proven quickly. The debugging features of Simulink during simulation enabled fast and accurate analysis of the model because all signals, variables, and states are accessible. Moreover, target changes can be made in a matter of days not months," says Robl.
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