Design and Control of Interconnected Systems Raffaello D’Andrea Cornell University
Examples • Power generation and distribution • Vehicle platoons • Satellite formation flight • Paper processing • Adaptive optics • MEMS data storage • Optical switching • “Smart” structures and so on. . . Common thread: • Distributed sensing and actuation capabilities • Highly structured interconnection topology
General Problem Class CONTROLLER PLANT wi yi vi ~ wi Gi di zi yi ui ~ Gi ui Requirements: Stability, performance, robustness ~ vi
Simplest case: Homogeneous Systems Basic building block, one spatial dimension
PERIODIC CONFIGURATION
BOUNDARY CONDITIONS
INFINITE EXTENT SYSTEM
2 D, 2 D BOUNDARY CONDITIONS
2 D, 1 D BOUNDARY CONDITIONS
2 D, NO BOUNDARY CONDITIONS
Results for linear and piece-wise linear systems Theorem: If the following semidefinite program has a solution: where N and the are fixed, and only a function of the basic building block, then all interconnected systems are well-posed, stable, and D’Andrea ’ 98, D’Andrea & Dullerud ‘ 03
Basic building block: control design Design controller that has the same structure as the plant:
PERIODIC CONFIGURATION
2 D, 2 D BOUNDARY CONDITIONS
Properties of design • Controller has the same structure as the plant • Finite dimensional, convex optimization problem • Optimization problem size is independent of the number of units
Arbitrary interconnections, heterogeneous components
Arbitrary interconnections, heterogeneous components
Theorem: the interconnected system is well-posed, stable, and if the following coupled semidefinite programs have a solution: if the subsystems are not interconnected: Langbort, Chandra, & D’Andrea ’ 03 Chandra, Langbort, & D’Andrea ‘ 03
Theorem: the interconnected system is well-posed, stable, and if the following coupled semidefinite programs have a solution: if the subsystems are not interconnected: Langbort, Chandra, & D’Andrea ’ 03 Chandra, Langbort, & D’Andrea ‘ 03 When working with linearized dynamics, results generalize to control system design
Summary • Semidefinite programming a powerful tool for control design and analysis of interconnected systems • Generalization of powerful results for single systems: linear, piece-wise linear, nonlinear • Leads to distributed semidefinite programs, whose structure is captured by interconnection topology