Everything you need to know about the systems engineering V-Model
What Is the Systems Engineering V-Model (V-Cycle)?
The V-Model — also called the V-cycle — is a systems engineering framework that lays out a project’s entire lifecycle in the shape of a “V.” The left side of the V walks down from high-level requirements to detailed component design; the right side walks back up, integrating and testing each level against the requirement it was built to satisfy. Originally developed by the German government for planning system development projects, the V-Model (V-cycle) is now used across automotive, aerospace, and software engineering as a way to keep every design decision traceable back to a requirement and every test traceable back to the design decision it verifies.
What does systems engineering do?
The goal of a system engineer is to oversee the engineering, business, and management aspects of a project or system. System engineers usually work transdisciplinary to ensure a successful realization of a project and are engaged from conception to completion of a project. System engineers are also responsible for analyzing and resolving system challenges to find more productive ways to meet project needs.
What is a systems engineering example?
Systems engineering procedures are used in complex and large projects. Depending on the size and complexity of the project, will depend on the number of system engineers required to manage a project. For example, an automobile can have over 30,000 individual parts/components. As a result, a vehicle is broken down into commodities such as exterior, interior and electrical. Each commodity will have a system engineer responsible for integration/engineering/performance and cost all the part of that specific commodity. There is also a vehicle-level system engineer (program engineering manager) who ensures that all the commodity system engineers work together to achieve the program goals. To successfully execute their responsibilities, systems engineers use a wide range of tools that include modeling and simulation, requirements analysis (such as Quality Function Deployment), and meetings to manage complexity.
What industries use the V-Model?
V-Model is one of the widely used by various industries such as automotive, aerospace, computer and robotics. The V-Model is a system engineering approach that was developed by the German government for planning and implementing system development projects. The V-Model is a high-level overview of the entire lifecycle of a project, laid out in an easy to view format.
How is the V-Model used in system development?
The V-model is a representation of system development that highlights verification and validation steps in the system development process. System engineers follow the V model from the initial concept to end of production. It looks at both technical and economic aspects to develop a system or project that meets the customers’ needs. The left side of the ‘V’ describes the steps that lead to definition and requirements of a project, its systems and its subsystem. The right side of the “V” describes the steps for integrating and validating each subsystem, system, and project.
Verification vs. Validation in the V-Model
The two arms of the V map directly onto two distinct engineering questions. Verification asks, “Are we building the product right?” — it confirms that each design output (a drawing, a CAD model, a prototype) correctly satisfies the specification that was written for it one level down on the left side of the V. Validation asks, “Are we building the right product?” — it confirms that the finished system actually meets the customer’s real-world needs, not just the written requirement. In the automotive V-Model below, verification happens at each rung going up the right side (component test, subsystem test, system test), while final vehicle validation — confirming the completed vehicle meets the original vehicle concept and customer expectations — happens at the top of the V.
V-Model vs. Waterfall vs. Agile
The V-Model is often confused with the Waterfall model since both move through sequential phases, and it’s sometimes contrasted with Agile, which iterates instead of following a single linear path. The table below summarizes the key differences.
| Basis | V-Model (V-Cycle) | Waterfall | Agile |
|---|---|---|---|
| Structure | Sequential, with each development phase paired to a matching test phase | Sequential, one phase completed before the next begins | Iterative, short repeating cycles (sprints) |
| Testing | Planned in parallel with design, starting on day one | Happens only after implementation is complete | Continuous, built into every sprint |
| Best suited for | Complex, safety-critical, hardware-heavy programs like vehicle development | Well-understood projects with stable, unchanging requirements | Software projects where requirements are expected to evolve |
| Flexibility to change | Low — changes ripple across the paired left/right steps | Very low | High |
Describe 10 characteristics of the systems engineering “V” model specific to the automotive industry.
The system engineering “V” model is used to show all the key steps in the product life cycle. The 10 characteristics of the system engineering “V’ model are:
- Advanced design and planning– during this stage the general assembly is created, establishing the vehicle’s preliminary architecture and characteristics. Some of these characteristics include but are not restricted to vehicle type (architecture) the propulsion system (ICE vehicle or BEV) and the location of the drive wheels (FWD, RWD, AWD). The performance targets are also developed as well as the expected market and a list of references and competitive vehicles it will compete against in the market.
- Vehicle concept- during this stage the goal is to understand the design and engineering challenges. A business plan is created which covers the projected sales volume, the planned life of the new vehicle, the vehicle program timing, the location(s) this vehicle will be built and the tooling plan, and the financial plan (expected cost, required capital, projected revenue, estimated profit). This all information is presented to senior management to get consent before proceeding.
- Product concept – during this stage individual designers and integration engineers work with various engineers to create the vehicle concept. This involves the following 3 steps, creating 2D (typical sections) and full 3D CAD models with the best assumptions. Creating full vehicle renderings or videos, which portray what the vehicle would look like in actual life. Finally, also creating physical mock-ups such as seating bucks which engineering and upper management can physically touch and sit in. These seating bucks can be made from foam, clay wood, or fiberglass combinations.
- Systems–during this step, each engineering team is working on their vehicle system can be configured to fit within the vehicle based on exterior and interior styling requirements. The teams are also working to see how the various systems interface with each other to meet all functional, ergonomics, quality, and safety program requirements.
- Subsystems- during this phase engineers being to create a more detailed design of the subsystems inside of each system. This step is straddled in time with the systems step.
- Components– during this phase engineers being to create a more detailed design of the components inside of each subsystem. This step is straddled in time with the subsystems and systems step. During this step, you also manufacture components and test that they meet their functional characteristics and requirements.
- Assembled subsystems– Components are assembled to form subsystems, which are tested to ensure that they meet their functional characteristics and requirements.
- Assembled systems-subsystems are assembled to create systems and tested. Corresponding assemblies are also tested to make sure they meet their functional characteristics and requirements.
- Assembled product– systems are assembled to create a vehicle. These initial vehicles are the first drivable prototypes. These first vehicles are tested to make sure the vehicle meets its characteristics and requirements. Issues that may arise are pushed back to the corresponding component, subsystem, or system to correct before the start of regular production.
- Operation and refinement– vehicles are produced and shipped to dealerships and sold. During this period vehicles are purchased, used, and maintained by the customers and serviced by the dealerships. Vehicles may also be refined with a minor or major update.
- Retirement and disposal– the vehicle is pulled from the market, which marks the end of the production of the vehicle. The assembly plant and all the equipment and tools are recycled or retooled for the next vehicle cycle.
This ten-step outline is the theory behind the process. To see what these stages actually look like in practice—how a real vehicle program moves from a spider chart of program assumptions through clay models, CAD, and Class A surfacing—see our complete walkthrough of the automotive design process.
References:
- Tim Weilkiens, CHAPTER 1 – Introduction, Editor(s): Tim Weilkiens, The MK/OMG Press,
Systems Engineering with SysML/UML, Morgan Kaufmann, 2007, Pages 1-22, ISBN 9780123742742,
https://doi.org/10.1016/B978-0-12-374274-2.00001-8.
(https://www.sciencedirect.com/science/article/pii/B9780123742742000018) - Automotive Product Development: A Systems Engineering Implementation, by Vivek D. Bhise. ISBN: 978-1-4987-0681-0. Publisher: CRC Press, Boca Raton, FL: CRC Press, 2017. (APD)
Frequently Asked Questions
What is the systems engineering V-Model?
The systems engineering V-Model is a project lifecycle framework shaped like a “V.” The left side breaks a system down from high-level requirements into detailed component designs; the right side builds back up, integrating and testing each level against the requirement it was designed to satisfy.
Why is the V-Model also called the V-cycle?
“V-Model” and “V-cycle” refer to the same framework. The name comes from the shape of the diagram: time runs left to right while the level of detail runs down and back up, tracing the letter V, which is why the process is also called the V-cycle.
What is the difference between verification and validation in the V-Model?
Verification asks “are we building the product right?” and confirms a design output meets its own written specification. Validation asks “are we building the right product?” and confirms the finished system actually meets the customer’s real-world needs, not just the paper requirement.
How does the V-Model differ from Waterfall and Agile?
Like Waterfall, the V-Model moves through sequential phases, but it pairs every design phase with a matching test phase planned from day one rather than testing only after implementation. Agile, by contrast, iterates in short repeating sprints rather than following a single linear path, which suits projects where requirements are expected to change.
How is the V-Model applied to automotive product development?
In automotive development, the V-Model runs from advanced design and vehicle concept, down through product concept, systems, subsystems, and components, then back up through assembled subsystems, assembled systems, and the assembled vehicle, ending in operation, refinement, and eventual retirement and disposal.
What industries use the V-Model?
The V-Model is widely used in automotive, aerospace, computer, and robotics development, and in any complex program where design decisions need to stay traceable to requirements and every test needs to trace back to the design decision it verifies.
