טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentZaslavsky Ron
SubjectSampled-Data H2 Estimation Problems
Motivated by Tensegrity Structures
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Leonid Mirkin
Full Thesis textFull thesis text - English Version


Abstract

Control and estimation in large-scale spatially distributed systems is an emerging topic in the control literature. Technological developments make it feasible to incorporate large arrays of sensors and actuators into various products. This opens new opportunities and poses new challenges for control theory. The main challenge is the need to handle a huge number of control channels, which is not (and, probably, will not be) feasible using existing (centralized) control strategies. Decentralized schemes could be a remedy, yet the development of numerically reliable analytical design methods with decentralized controller structure is still an open problem.  


This thesis puts forward an alternative approach based on spatial clustering. The idea is first to aggregate, using a simple finite memory algorithm, sensed information from a group of closely located sensors into a single signal (spatial sampling). This results in a substantially smaller number of measurements entering the controller, which therefore can process this information in a centralized fashion and produce a number of control signals. Each of these signals is then post-processed, using again simple finite memory algorithms, and locally distributed by a group of closely located actuators (spatial hold functions). This kind of controller can be analyzed and designed by the tools from sampled-data control theory. The main technical challenge in the transition from temporal to spatial sampling is the need to handle relaxed causality (Spatial dynamics do not need to be causal.).  


Several steps toward the solution of the spatial clustering problem are presented, in two parts. The first (Unstable-unit-cell tensegrity plate design), motivates the problem by presenting an example of spatially distributed system requiring a huge number of sensors and actuators to function properly. The second part (Sampled-data estimation, with relaxed causality), presents the solution of the estimation version of the spatial clustering problem. The feasibility of the UUTP topology has been proven, and an algorithm for the design of UUTPs with many members has been developed. Several sampled-data estimation problems with relaxed causality constraints and generalized sampling devices have been solved. We solved the H2 sampled-data fixed-interval and fixed-lag estimation (smoothing) problems. Similar to the sampled-data Kalman filter case, a discrete algebraic Riccati equation is solved, the non-causal estimators are made of a cascade of discrete-time LTI filter and a stationary generalized hold, and their pulse response is inherently consistent. Unlike the Kalman filter, the estimators pulse response is continuous, and the hold function depends on the sampler parameters.