Fundamentals of RTOS-Based Digital Controller Implementation

Abstract

Digital controllers are increasingly designed and built using commercial off-the-shelf (COTS) hardware and software components. This is a result of the availability of high-performance, low-cost microcontrollers, specialized embedded processors, and various real-time operating systems (RTOSs). The wide selection of RTOSs does not necessarily translate into an increased availability of systems that are capable of facilitating the construction of controllers meeting the performance and stability requirements demanded by the mechatronics applications. A primary contributing factor to that disparity is that the design goals of many RTOSs focus on the overall system response time and may neglect other timing constraints in the controller.This chapter examines the major components of an RTOS and the implementation of the controller using those components from a computing science perspective. By introducing the various operating system concepts and the way in which these concepts affect the digital controller design, this chapter aims to aid control engineers in better understanding an RTOS. With this knowledge, design decisions can be made to compensate for the deficiencies in the underlying software platform. This chapter also provides a survey of the results of the various research topics in the field of computer-controlled systems design. The contribution of this chapter is its synthesis of topics from control engineering theory with concepts from real-time systems in the RTOS context. We thus aim to help the control engineer to develop a systematic approach to the implementation of control systems using either a COTS RTOS or an open source-based research RTOS.The main objective of this chapter is to assist the control engineer in architecting the controller implementation while taking into consideration the issues that are present in the underlying supporting RTOS, thus creating an optimal design.