Sanjay Lall

State-Space Decentralized Control

November 10, 2009

• The paper An Explicit State-Space Solution for a Decentralized Two-Player Optimal Linear-Quadratic Regulator by John Swigart and me addresses the decentralized linear-quadratic control problem. Here we show that the optimal policy is not as might be expected; each player has to do more than simply estimate the states that they cannot observe. In other words, the simplest separation principle does not hold for decentralized control.

Presidential Award

December 19, 2008

• It is a great honor to receive the Presidential Early Career Awards for Scientists and Engineers (PECASE). I was nominated by the National Science Foundation, and the award was presented at the White House on December 19, 2008. Press releases describing the award were issued by the White House and the National Science Foundation. There is also a Stanford News article.

Adaptive Optics

May 14, 2008

• The image on the right shows a single star observed using adaptive optics, and that on the left shows the same star observed without it. The experiment is presented in the paper Experimental Validation of Single-Iteration Multigrid Wavefront Reconstruction at the Palomar Observatory by Laurent Lessard, Douglas MacMynowski, Matthew West, Antonin Bouchez, and me. The paper Warm-started Wavefront Reconstruction for Adaptive Optics by Laurent Lessard, Matthew West, Douglas MacMynowski and me analyzes the achievable error for warm-started multigrid algorithms in large adaptive-optics systems for telescopes. We address the underlying linear estimation problem, which must be solved at very high rates.

George S. Axelby Award

December 15, 2007

• The paper A Characterization of Convex Problems in Decentralized Control by Mike Rotkowitz and me was awarded the George S. Axelby Outstanding Paper Award by the IEEE Control Systems Society. The award is given annually to recognize outstanding papers published in the IEEE Transactions on Automatic Control during the preceding two years. The paper gives conditions under which one can use convex optimization to synthesize minimum-norm decentralized controllers. Here are the slides for the talk I gave at Keith's birthday workshop.

Networked Markov Decision Processes

September 17, 2007

• The paper Optimal Control of Distributed Markov Decision Processes with Network Delays by Sachin Adlakha, Ritesh Madan, me, and Andrea Goldsmith shows that for certain networked problems there are easily computable finite memory optimal controllers.

Systems with Delays

July 1, 2007

• The paper Positive Forms and Stability of Linear Time-Delay Systems by Matthew Peet, Antonis Papachristodoulou and me gives a simple way to construct polynomial Lyapunov functions for systems with delays.

Event-Based Sampling

October 5, 2006

• The paper A Constant Factor Approximation Algorithm for Event-Based Sampling by Randy Cogill, Joao Hespanha and me gives a simple bound on the performance of an event-based sampling method. The idea here is that when communication is constrained to be infrequent, event-based sampling can achieve better estimator performance than periodic sampling.

Workshop Photos

October 5, 2006

• Some photos from the workshop SDP Relaxations and Algebraic Optimization in Control which Pablo Parrilo and I presented at MTNS in July 2006.

Symmetries

October 5, 2006

• Here is the latest version of the paper On Structured Semidefinite Programs for the Control of Symmetric Systems by Randy Cogill, Pablo Parrilo, and me. It shows how symmetries in linear systems may be exploited when using convex programming for controller synthesis.

Keith Glover's 60th Birthday

April 25, 2006

• The workshop celebrating Keith's birthday was wonderful! Take a look at the picture of my student Mike and my advisorial ancestors. There are also some more photos.

Control Performance Bounds without Solving the Hamilton-Jacobi Equation

March 20, 2006

• The latest paper, Suboptimality Bounds in Stochastic Control: A Queueing Example gives a simple way to compute upper and lower bounds on the performance of stochastic control systems. A particularly interesting aspect of this work is that any function may be used as an approximate Hamilton-Jacobi solution; better choices give better bounds.

Best Student Paper, CDC 2005

December 2005

• Mike Rotkowitz and Randy Cogill won the best student paper prize at the IEEE Conference on Decision and Control in December 2005. The paper A Simple Condition for the Convexity of Optimal Control over Networks with Delays.