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Model-Based Design for Embedded Systems- Part 18

Model-Based Design for Embedded Systems- P18: This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. | 146 Model-Based Design for Embedded Systems 6.1 Introduction Embedded systems and networked embedded systems play an increasingly important role in today s society. They are often found in consumer products e.g. in automotive systems and cellular phones and are therefore subject to hard economic constraints. The pervasive nature of these systems generates further constraints on physical size and power consumption. These product-level constraints give rise to resource constraints on the implementation platform for example limitations on the computing speed memory size and communication bandwidth. Because of economic considerations this is true in spite of the rapid hardware development. In many applications using a processor with a larger capacity than strictly necessary cannot be justified. Feedback control is a common application type in embedded systems and many wireless embedded systems are networked control systems that is they contain one or several control loops that are closed over a communication network. The latter is particularly common in cars where several control loops e.g. engine control traction control antilock braking cruise control and climate control are partly or completely closed over a network. Embedded control systems are also becoming increasingly complex from the control and computer implementation perspectives. Today even quite simple embedded control systems often contain a multitasking real-time operating system with the controllers implemented as one or several tasks executing on a microcontroller. The operating system typically uses concurrent programming to multiplex the execution of the various tasks. The CPU time and in the case of networked control loops the communication bandwidth can hence be viewed as shared resources for which the tasks compete. Sampled control theory normally assumes periodic sampling and negligible or constant input-output latencies. When a controller is implemented as a task in a real-time operating system .