Communications in Embedded Control Systems

点击翻译按钮获取中文摘要

Egerstedt, MagnusCCR-0207411Communications in Embedded Control Systems - Project SummaryThis project investigates how different embedded software and hardwarecomponents should communicate with each other in order for the overall, globalsystem to behave in a satisfactory way. The main area of investigation is theinformation theoretic content of the transmitted signals, i.e. a study of howmany bits of information need to be transmitted between the different componentsin order to make the physical system meet its specifications. For instance,autonomous robotic systems are normally relaying on a variety of heterogeneoussensors, and the question then becomes, which of the sensors are needed? Andfurthermore, is it possible to compress the data in a systematic way, e.g. usingvirtual sensors, so that information that is not essential to the current task,or mode of operation, can be discarded?Since the sensory data needed for accomplishing a certain task depends both onthe control law, the dynamics of the system, and the complexity of the task,information theory provides a tool for treating questions concerning sensor andactuator selection and control mode design in a unified way. This project isfocused on the following two enabling areas of research:1. Modeling of the information theoretic content of the symbolic, computergenerated inputs used for controlling continuous, mechanical devices.2. Selection of embedded sensors and actuators for a multi-agent, roboticsystem. This selection is done so that the control system meets itsspecifications in the presence of bandwidth constraints, i.e. so the robotsmaintain formation while avoiding obstacles in the environment.In this project computer generated, or linguistic control commands are modeledas strings of mode descriptions that can be read by trigger based hybridsystems. In other words, models for software based control of physical,continuous devices are developed in such a way that the actual control signalshave a clear information theoretic content in terms of code lengths, thusconnecting the field of multi-modal control with that of information theory.This model enables the investigation of component integration issues. Since eachsensor or actuator contributes to the total number of bits needed for coding thecontrol signals, by minimizing the code lengths subject to the constraint thatthe system should behave in a satisfactory way, a natural measure of whatcomponents are needed in the current mode of operation is derived. Furthermore,the explicit focus on code lengths has immediate implication on coding theory,i.e. a theory for how the information shared between different embeddedcomponents should be represented is a direct consequence of this research.The information theoretic approach to control theory under investigation in thisproject has a number of potential applications outside the field of embeddedcontrol. For instance, in teleoperated robotics the control signals aretransmitted over communication channels in which the presence of channel noisemakes it preferable to transmit instructions that are as short as possible. Arelated problem arises in the area of minimum attention control, where anattention functional is defined as a measure of the control variability.