MULO Story: Open Source Single-seater Electric Tricycle Made in Switzerland
Prof Dr Luc Blecha CC-BY-SA stories share
Prof Blecha shares the story of MULO, an open-source, single-seater electric tricycle designed to deliver sustainable daily mobility. He provides details about sucessful adoption of Arcadia MBSE method using Capella integrated with requirements management in ReqView.
Driving Innovation in Sustainable Mobility
Prof. Luc Blecha, the storyteller, is an Associated Professor at HEIG-VD. He teaches system engineering and mechanical engineering and his research is focused on sustainable mobility solutions. As co-founder and former CTO of Almatech SA, Luc contributed to major achievements like CHEOPS, the Swiss exoplanet telescope launched in 2019. Between 2021 and 2023, he also developed a revolutionary hydrogen powered, fast and energy saving ferry called ZESST. Luc is passionate about driving the energy transition and turning innovative ideas into real solutions for a sustainable future.
Small is Beautiful
Students and scientists at the University of Applied Sciences and Arts of Western Switzerland set themselves the challenge of developing MULO – a single-seater electrical tricycle with low CO2 emission.
The project has three operational missions:
- Cover the daily mobility needs of Swiss car drivers, which averages 30 km per person.
- Respect planetary limits, with a focus on limiting global warming and CO2 emissions.
- Empower people to maintain, repair, and even build their own MULO by making all relevant information open source.
MBSE – Efficient Way to Develop and Share Information
Model Based Systems Engineering (MBSE) is a highly effective way to simultaneously develop innovative systems while documenting and sharing self-explanatory information.
We have chosen to use the Architecture Analysis & Design Integrated Approach (ARCADIA) using Capella, an open source MBSE software. ARCADIA is a system and software architecture engineering method based on architecture-centric and model-driven engineering activities. ARCADIA promotes a viewpoint-driven approach (as described in ISO/IEC 42010) and emphasizes a clear distinction between needs and solutions.
Following the ARCADIA method, MULO is developed, documented, and shared at four hierarchical levels:
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Operational Level defines what the user has to accomplish with MULO.
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System Level defines what MULO has to accomplish for the user to fulfill the operational objectives.
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Logical Level defines how MULO works to fulfill system expectations.
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Physical Level defines how MULO is built.
This methodology guided the design team throughout the development process while documenting the different interactions between functional requirements. MULO's architecture was created from top to bottom, flowing down top-level missions to each subsystem's hardware. At each level, complexity increases, describing and anticipating in greater detail the function of each subsystem.
The resulting Physical Architecture Diagram (PAD) provides a complete overview of MULO, including the interactions between different subsystems and full traceability up to the global project missions. The CO2 footprint of each subsystem is determined using the EcoDesign plugin for Capella developed by OBEO. The plugin allows interaction with the EcoInvent database using the open-source software OpenLCA.
How to Efficiently Include Textual Requirements in MBSE?
It is often not efficient to model every single requirement in MBSE. Regulatory requirements are typically those that make the system model more complex, less readable, and more difficult to maintain. In such cases, it is preferable to keep the regulatory requirements in text form.
ReqView is the ideal tool for managing textual requirements. First, ReqView complies with safety-critical and information security standards. Second, ReqView has Git capabilities, which guarantee safe and efficient version control and team working. Finally, ReqView can easily be tailored to your exact needs, with easy-to-use user interfaces and wizards.
In our case, we created a global System Requirements Specification (SysRS) based on the ISO 29148 standard templates, a global Glossary document, and subsystem-specific requirements documents when needed. The global SysRS gathers all EU regulations for L5e vehicles, while the Glossary contains a database of technical terms. The glossary definitions can be easily referenced in all other documents using hyperlinks.
We have added custom attributes in the SysRS to match our traceability needs. In particular, we added Verification Method, Compliance Status, Justification Level, and Justification Document References. These custom attributes help us better understand the status of our design with regard to regulations and trace every non-compliance.
Another key capability of ReqView is the export-to-ReqIF feature. This enabled us to transfer all our textual requirements managed in ReqView to Capella, thus creating a unified model with all functional and textual requirements. Allocating the requirements to subsystem hardware provides the design team with a very useful way to see all applicable functional and textual requirements for a particular subsystem.
We also appreciate the export-to-HTML feature of ReqView, which fits effortlessly into MULO's project website. As an open-source project, it is crucial to share the latest information in the most effective and user-friendly way and to ease the review process. Textual requirements are thus published while maintaining all traceability and documentation links.
Conclusion
MULO is developed using state-of-the-art systems development tools. Capella MBSE centralizes all system information, while ReqView manages all textual requirements. OpenLCA is used for the life cycle assessment of MULO. Finally, information is published on the project website.
ReqView made it possible to include textual requirements in the system model thanks to the export-to-ReqIF feature. The textual requirements are then allocated to subsystems inside the system model. This is crucial for us to maintain a single source of truth, which is a key benefit of MBSE. It also enables a global export of the full system model, including textual requirements, to HTML for lossless publication on MULO's website.
We would like to express our highest regards to the ReqView team, who provide high-quality software that greatly helped our design team to develop and document efficiently MULO.
