Applying Model-Based Design to Commercial Vehicle Electronics Systems

Abstract

Commercial vehicle manufacturers face unique challenges for the development of vehicle electronics systems. For one, customers typically have unique requirements coupled with an expectation of high reliability. Vehicle electronics is often the enabler for customized features. Ensuring that the vehicle will perform as demanded and promised adds a degree of burden on the vehicle manufacturers. Furthermore, the verification and testing of a large number of unique electronic system configurations is very expensive and time-consuming. This paper will explore how ModelBased Design can be used to meet these challenges and provide a high degree of confidence for both the manufacturer and the customer that requirements have been met. It will discuss factors to consider to support configurability, approaches for defining a system architecture that facilitates reuse, and capabilities for modeling state-based systems. VEHICLE ELECTRONICS ENGINEERING CHALLENGES While the powertrain provides the propulsion necessary to perform the required work, vehicle electronics, which include such functions as lighting, operator comfort and assistance, display, power management, and security and safety systems, provide important differentiation in terms of operator comfort, convenience and productivity. As a result, the embedded electronic content in commercial vehicles continues to grow, which leads to the complexity that comes with managing multiple electronic control modules (ECUs). Additionally, many commercial vehicles are developed for a wide range of applications requiring significant customization. It is not atypical for every vehicle that rolls off the assembly line to be unique. Developing, testing and maintaining a large number of custom vehicle configurations pose a significant challenge in terms of both cost and time-tomarket. The challenge manifests itself in the need to leverage the benefits of vehicle electronics while effectively managing the increased system complexity and customizations required to service the diverse needs of the customers. WHAT IS MODEL-BASED DESIGN The traditional development process for vehicle electronics is characterized by Use of paper specification generated from requirements gathered from various sources Building physical prototypes for design. Writing code manually to implement control algorithms and complex logic. Dependence on test vehicles for verification and validation. Figure 1: Traditional Vehicle Electronics Development Process, where design, implementation, and test are done by individual team each suffering from barrier of communication to its supplier and customer. A significant problem with this process is that errors in specification are often not discovered until final validation, which leads to specification change, redesign, re-implementation, and re-validation. Consequently, cost of fixing errors is high [1]. Because of the many vehicle electronics configurations in commercial vehicles, complete test coverage of the design is practically impossible using test vehicles. As a result, errors may be “leaked” into products, leading to field repairs. Model-Based Design emerged from the need to reduce development cost and improve product quality at the same time, while the complexity of vehicle electronics multiples. In Model-Based Design, a model of the system being developed serves as the common thread throughout the development process, from requirements capture to final validation. As an executable specification, this system model is refined throughout the development process. Simulation is used at each process step to verify whether the design meets the requirements. Code generation is used for implementing control algorithm and complex logic, thus eliminating errors introduced by writing source code by hand. Figure 2: Development Process with Model-Based Design Since its introduction, Model-Based Design has become widely adopted in the development of electronic control systems, powertrain and vehicle alike for commercial vehicle applications. Examples of applying ModelBased Design to commercial vehicles have been extensively highlighted in past SAE technical papers or presented at conferences in the automotive industry [2] [3] [4]. The remaining sections of this paper will provide a set of guidelines for applying Model-Based Design to vehicle electronics applications, with emphasis on system architecture and modeling state-based systems. Typical scenarios for implementation and verification are also described to provide a complete description of Model-Based Design.