Distributed Control of Electric Drive Systems via Ethernet

• This thesis is on adapting standard Switched Ethernet for distributed control applications in electric drive systems. The critical issue of Ethernet here is to provide services to real-time applications. The architectural construction of Ethernet is described, where the objective is to summarize the state of the art and indicate the causes of delays. This results in a network configuration suitable for distributed control applications, with no modifications to the protocols, but introducing the correct placement for the Ethernet Switch. A timing analysis on the Switch itself results in useful conclusions on the causes of non-deterministic nature of delays. Further, the delay measurements are taken on a real Switched Ethernet network, which are used to characterize the network. The delays are addressed also in the control systems perspective, as they trigger unwanted performance issues. They set limitations on the performance that can be achieved, even with the best possible controller. The architectures for connecting the nodes of a distributed control system is also studied, which are categorized according to the triggering mechanism. Both the networking and control system perspectives are extended for the delay compensation, where standard delay compensation techniques are experimentally verified on a speed control of a Brushless DC motor drive setup. The Proportional Integral controller with robust tuning techniques and Smith Predictor delay compensation, modified with the algebraic design techniques as well as State Feedback controller deploying on-line delay compensation have been verified. The latter technique proved to be promising but at the cost of time stamped measurements, which require synchronization of clocks at the nodes. This is presently cumbersome with most of the cost effective sensor actuator modules with Ethernet connectivity. Therefore the state feedback method is further improved using a plant model based predictor, where it eliminates the need of time stamped measurements. The stability has been studied and the design methodology is derived, which is proved to be better in simulations. However, the methodology expects the control delay not to exceed the sampling period. The thesis introduces an adaptive sampling scheme to cope with this situation, in which the sampling period is varied on-line depending on the current control delay. Further this methodology is experimentally verified using distributed position control of an XY board via Ethernet. The network connectivity for the motors of the XY board are obtained through Ethernet Ready Sensor Actuator (ERSA) modules designed and manufactured in the course of studies. Finally the general aspects of design, simulation and applications of distributed control systems have been presented.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Nyckelord

adaptive sampling scheme

control delay

delay compensation

distributed control systems

Ethernet

Ethernet ready sensor actuator module

sampling period

Electrical engineering

Elektroteknik

Publikations- och innehållstyp

vet (ämneskategori)

dok (ämneskategori)