I had the opportunity to attend the AMPLab winter retreat in Asilomar, near Monterey. It’s was a rare opportunity to interact with the broader community of AMPLab affiliates: graduate students, postdocs, faculty members, and industry sponsors. There were dozens of companies represented including Amazon, Google, Intel, Facebook, Samsung, and others. The three-day event included talks, poster sessions, panel discussions, and plenty of time to interact with the 120+ attendees. Overall a great success! On the right is a photo taken at the nearby beach with Me, Ben, Mahdi, and Dimitris.

I attended the Workshop on Future Directions in Networks, Optimization & Controls at USC. This one-day event following CDC featured 20-minute talks by professors, poster presentations by graduate students and postdocs, and a panel discussion on the future of research and education in controls. I had a great time — there were many big names in attendance, and the intimate venue was a relief from the chaos of CDC. Many thanks go out to the organizers Petros, Rahul, Urbashi, and Ashutosh for inviting me and for putting together a successful event on such short notice! On the right is a photo of some ex-Berkeley colleagues in attendance (Eilyan, me, Ashutosh, Melanie, and Mahdi). At the workshop, I presented a poster on my recent work with Ben Recht and Andy Packard on the topic of optimization and robust control. My poster is available here and a preprint of the work is available here.

I attended the 2014 Conference on Decision and Control in Los Angeles. I must say this was one of the best CDC’s I have ever attended. The venue was very nice, there was an abundance of high-quality talks, and all the organized events (breaks, receptions, banquet) were well planned and executed. Kudos to the organizers! It was also my first time visiting downtown LA. Although I spent most of my time in and around the conference hotel, I still got a taste for the surreal scale of things. Exhibit A: a 12-story-tall ad for the movie Interstellar (a great movie, incidentally!). At the conference, I presented the paper “State-space solution to a minimum-entropy H-infinity optimal control problem with a nested information constraint”. This work provides an extension of the DGKF result (see my recent post about this) to a setting in which there are two cascaded plants controlled by cascaded controllers that must be simultaneously designed. Slides are available here. Chris Meissen also presented the paper “Performance certification of interconnected nonlinear systems using ADMM”, co-authored by me, Murat Arcak, and Andrew Packard. The paper generalizes the results reported at ACC’14 (see my post) to nonlinear systems by using sum-of-squares (SOS) tools.

The paper “An Algebraic Approach to the Control of Decentralized Systems” by me and Sanjay Lall will appear in the December 2014 issue of the IEEE Transactions on Control of Network Systems. The paper describes a purely algebraic treatment of the notion of quadratic invariance, which can be used to analyze decentralized control problems. This new viewpoint is powerful because it allows one to work with rational transfer functions, for example, without the need for an underlying topology or norm. A more spaced-out and legible version of the paper is also available on arXiv, and the final published version of the paper is available here.

During the month of October, I traveled to various schools throughout Southern California to give talks. Here is the list:

• ComNetS Seminar at the University of Southern California
• Systems and Control Research Seminar at UCLA
• Optimization and Control Seminar at UC San Diego
• CMS Seminar at Caltech
• CCDC Seminar at UC Santa Barbara

I had a wonderful time and I am grateful to each of these schools for hosting me during my visits. Pictured on the right is the Sun God, one of the many statues on the UC San Diego campus. The talks I gave were about my recent work with Andy Packard and Ben Recht on the topic of using robust control to analyze and design optimization algorithms. A preprint of this work is available on arXiv.

I recently attended the 2014 Workshop on Uncertain Dynamical Systems in Amsterdam. Most of the attendees were from Europe, which made the workshop a unique opportunity to meet and hear from researchers that I had previously only known “on paper”. I gave two talks, both about projects that are still in the works, but for which we just recently posted preprints. The first talk was about state-space solutions to decentralized control problems (arXiv), and the second was about an application of IQC theory to the analysis and design of optimization algorithms (arXiv).

I attended a very special workshop at Caltech this past week. The occasion was a celebration of the 20th anniversary of the CDS program (Control + Dynamical Systems), and also marked the launch of Caltech’s new CMS department (Computing + Mathematical Sciences). It was also an opportunity to celebrate some birthdays: Richard Murray’s 50th, John Doyle’s 60th, and Karl Åström’s 80th. The workshop was a great opportunity to hear about current research as well as future outlook, all from leaders in the field.

I also managed to get a photo of what I’m calling my “extended academic family” — In the first photo from left to right are: my current postdoc advisor Andy Packard, former postdoc advisor Anders Rantzer, my PhD advisors Sanjay Lall and Matt West, Sanjay’s PhD advisor Keith Glover, me, and current collaborator Ben Recht. In the second photo are the authors of arguably the most influential modern control theory paper (Doyle, Glover, Khargonekar, Francis). Incidentally, this paper, known nowadays as DGKF, was published exactly 25 years ago.

I attended the 2014 American Control Conference in Portland, Oregon. On the right is a photo of the iconic Mount Hood taken outside the city on I-84. At the conference, I spoke at the workshop entitled “40 Years of Robust Control 1978 to 2018”. Chris Meissen also presented the paper “Performance certification of interconnected systems using decomposition techniques”, co-authored by me and Andrew Packard. The paper describes a framework for analyzing interconnected systems. Performance certification is typically a difficult problem that scales poorly. The approach we propose uses a distributed optimization technique to find a global performance certificate by only ever solving local certification problems. The approach is very fast and scalable, but it is only sufficient in the sense that it may fail to find a certificate even if one exists.

Two papers submitted to CDC’14 in Los Angeles! The first paper is by Chris Meissen, me, Murat Arcak, and Andrew Packard and is called “Performance certification of interconnected nonlinear systems using ADMM”. It is a generalization of a previous paper that will be presented at ACC in June. The second paper is called “State-space solution to a minimum-entropy H-infinity optimal control problem with a nested information constraint” and finds an explicit solution to the two-player H-infinity control problem. The solution has a beautiful structure, but requires solving a pair of coupled algebraic Riccati equations. I show in the paper that a simple iterative scheme can find the fixed point very efficiently. The paper is also available on arXiv.

Two recently submitted journal papers have been accepted for publication as full papers! I have uploaded revised versions of the papers, available via the links below. These versions are not yet final, but there will likely not be any further major changes. The first paper is “Optimal control of two-player systems with output feedback” which will appear in TAC. The second paper is “An algebraic approach to the control of decentralized systems” which will appear in TCNS.