Model-Based Design of a Power Window System: Modeling, Simulation, and Validation Sameer M. Prabhu and Pieter J. Mosterman The MathWorks, Inc. 3 Apple Hill Dr. Natick, MA 01760 Abstract The need to bring innovative, high-quality products to market faster is driving the use of models during the design and realization process. Model-based design provides efficiencies in product development that enable companies to deliver products on time, remain within budget, and fulfill initial requirements. The latest model-based design tools can also generate prototype and production code from a model automatically, significantly decreasing development time. This paper applies the model-based design process to the design of a power window control system and considers various aspects of the validation process via testing both during simulation and physical realization. 1. Introduction Given competitive temporal and cost constraints, developing a product on time and within budget requires a systematic approach to design and realization. A systematic approach ensures that the final product meets the initial requirements and lets engineering teams with different specializations work together and communicate between stages in the overall process. In addition, this approach also ensures that the design process and the final product are documented for maintenance and future development. The systematic design and realization process in the aerospace and automotive industries is typically represented by a V diagram as shown in Figure 1 (e.g., see [3,4]). Each of the two branches of the V corresponds to distinctly different activities: 1. The left branch captures the decomposition of the initial system requirements into subsystems and components that are specified and implemented at a detailed level. 2. The right branch represents the realization of these subsystems and components and their integration. In the traditional approach, engineering teams observe strict boundaries between their design activities and they communicate by passing design documents back and forth. This approach has the following drawbacks: 1. Documents can be unwieldy and unsuitable for recording functionality. 2. It is difficult to keep the documentation synchronized with the current state of the design. 3. Once the design is approved, coding the application becomes a separate, manual activity. 4. When documents are used as deliverables and shared electronically, engineers often duplicate efforts. It is difficult to trace the source of errors along a paper trail. Engineering teams have turned to model-based design and realization to address these problems. The model- based approach lets them address increasing product complexity, more stringent performance requirements, and shorter product development cycles. By using models in the early design stages, engineers can create what are known as "executable specifications" that enable them to immediately validate and verify specifications against the requirements. Validation ensures that the requirements are correct and that they represent the intended behavior. Verification ensures that the outputs of each step satisfy the steps inputs (i.e., the system satisfies its requirements). Less formally, verification checks whether the model is built correctly and validation checks