Navigating the Automotive Systems Engineering Workflow: The V-Model Explained

V-model inside Model Based Systems Engineering. How to navigate in this model.

Welcome to MBSE Explained! As vehicles evolve into complex systems-of-systems—especially in the EV and autonomous driving space—having a robust, structured development process isn't just a good idea; it's essential for success, safety, and efficiency. From my experience as a systems architect in the automotive world, I've seen firsthand how a clear workflow can mean the difference between a smooth launch and a project plagued by integration nightmares.

One of the most foundational and enduring frameworks in automotive development is the Systems Engineering V-Model. While some see it as traditional, its principles of rigorous definition and verification are more relevant than ever. In this post, we'll break down the V-Model, explore each stage of the process, and discuss how modern practices like MBSE are giving it a new lease on life. Let’s dive into the roadmap that turns an idea into a road-ready electric vehicle.

What is the Systems Engineering V-Model?

At its core, the V-Model is a graphical representation of a systems development lifecycle. It illustrates the relationship between the project definition phases (the left side of the V) and their corresponding testing and integration phases (the right side of the V).

Imagine building a complex EV powertrain. You wouldn't just start soldering components together. You'd begin with high-level goals, break them down into detailed technical specifications, design the architecture, and then start building. The V-Model formalizes this logic.

• The Left Side: Represents decomposition and definition. It moves from abstract concepts down to concrete design details.
• The Right Side: Represents integration and verification. It moves from individual components back up to the complete, validated system.
• The Bottom Point: Represents the implementation phase, where individual units or software modules are created based on the most detailed designs.

This structure ensures that for every design decision made, a corresponding verification or validation activity is planned.

The Left Side of the V: Defining and Designing the System

This is where we translate a market need into a buildable product. It’s a top-down process of increasing detail and refinement.

1. Customer Requirements

This is the starting point—the "why" behind the project. These requirements are often captured from market research, stakeholders, and potential users. They are typically high-level and express what the user wants the system to do.

• Example: "The EV must have a real-world driving range of at least 450 km on a single charge."
• Example: "The infotainment system should seamlessly connect with both Android Auto and Apple CarPlay."

These are needs, not technical solutions. The goal here is to capture the voice of the customer accurately.

2. System Requirements

Here, we translate the customer's wishes into testable, technical specifications—the "what." This phase is critical and requires deep engineering knowledge. We define functional requirements (what the system does) and non-functional requirements (how it does it, e.g., performance, safety, reliability).

• Customer Need: "450 km range."
• System Requirement: "The vehicle shall be equipped with a high-voltage battery pack with a minimum usable capacity of 75 kWh."
• System Requirement: "The combined powertrain efficiency shall exceed 88% under the WLTP test cycle."
• System Requirement: "The system must comply with functional safety standard ISO 26262 ASIL-B."

This is where MBSE starts to shine. Instead of just writing documents, we can capture these requirements in a model and begin linking them to the functions they enable.

3. System Architecture

Once we know what the system must do, we define how it will be structured. This is the blueprint. We break the system down into major logical and physical subsystems and define their interfaces and interactions.

• Example: To meet the powertrain requirements, the architecture might include:
  • A Battery Management System (BMS) to monitor cell health and state of charge.
  • A DC/DC Converter to supply low-voltage power.
  • An Inverter to convert DC battery power to AC for the motor.
  • A Traction Motor.
  • A Vehicle Control Unit (VCU) to orchestrate their behavior.

In an MBSE approach, this is where we would use SysML diagrams (like Block Definition Diagrams and Internal Block Diagrams) to formally model these components, their ports, and the data they exchange. This model becomes the single source of truth for all teams involved.

The Right Side of the V: Proving It Works

The right side mirrors the left. As we integrate the built components, we perform tests at each level to verify that we've met the requirements defined on the other side.

1. System Integration & Verification

• Corresponds to: System Architecture
• Question: Do all the components we designed work together correctly?

Here, we integrate the subsystems (BMS, Inverter, Motor, etc.) and test their interfaces. This is often done using Hardware-in-the-Loop (HIL) or Software-in-the-Loop (SIL) simulation before the full vehicle is available. We verify that the VCU can command the inverter correctly and that the BMS is reporting accurate data. The goal is to catch integration bugs early.

2. System Validation

• Corresponds to: System Requirements
• Question: Does the fully integrated system meet its technical specifications?

Once the entire system (e.g., the complete vehicle) is assembled, we validate it against the system requirements. We put the car on a dynamometer to measure its efficiency and on a test track to validate its performance. Does the battery pack deliver 75 kWh? Does the system meet its ISO 26262 safety goals? We are validating that we built the system right.

3. Customer Acceptance / Validation

• Corresponds to: Customer Requirements
• Question: Did we build the right system that satisfies the customer?

This is the final and most important test. Does the finished EV actually achieve a 450 km range in real-world driving conditions? Does the infotainment system connect to phones without glitches? This phase validates that the final product meets the original user needs that started the entire process.

The V-Model in the Modern MBSE World

The V-Model provides a logical and traceable structure that is perfect for safety-critical systems. When you combine it with MBSE, you supercharge its capabilities. The system model becomes a central hub that formally links customer needs to system requirements, to architectural components, and finally, to verification test cases.

This digital thread makes it incredibly powerful to perform impact analysis. If a customer requirement changes, you can instantly see every system requirement, component, and test case that is affected. This is a game-changer compared to managing traceability across thousands of lines in disconnected documents and spreadsheets.

Conclusion

The Systems Engineering V-Model is more than just a diagram; it's a disciplined workflow that brings order to the chaos of automotive development. By systematically defining requirements, designing an architecture, and then verifying each step during integration, it provides the traceability needed to build safe, reliable, and complex vehicles.

For modern EV development, pairing the V-Model's structure with the connected, holistic view of MBSE creates a powerful combination for tackling next-generation challenges.

What are your thoughts on the V-Model in automotive engineering? Share your experiences in the comments below!

At MBSE Explained, we're dedicated to simplifying systems for smarter EVs.