Prof. Whitcomb (Uncle Louie) steps in and hoods our three most recent PhDs

Hooding2015

Shahin Sefati, Alican Demir, and Mert Ankarali (left to right, Hopkins gold regalia) were hooded today by  ME Professor Louis Whitcomb (Yale regalia). Sadly, I am out of town and didn’t get to do it myself, but was very happy that my colleague and academic brother stepped up and did the honors for me!

-Noah

Two LIMBS students tie the knot!

As proof that the LIMBS lab has a friendly lab culture (maybe too friendly?), LIMBS members Alican Demir and Erin Sutton tied the knot on January 3, 2015. All joking aside, warm congratulations, Alican and Erin!

Alican & Erin's Wedding

Alican’s Practice Talk for IROS Workshop on Active Touch

PhD Student Alican Demir presented his research at an IROS 2014 workshop on “Active Touch in Animals and Robots“.

Special thanks to our collaborators, Jean-Michel Mongeau and Bob Full.

LIMBS Lab (past and present) at IROS 2014

From right-to-left Jusuk Lee (graduated 2009), Alican Demir (will graduate 2014),  Vinutha Kallem (graduated 2008), and Vinutha’s husband Pranava. What a great reunion!

limbs-iros2014

 

Here are Vinutha and Jusuk in front of a million dollar door in Chicago:

jusuk-vinutha-iros2014

Time for Control

In engineering and mathematics, t is the quintessential independent variable: an immutable quantity in terms of which all other variables depend. Most control systems do require a clock, but clocks have been engineered with such low drift rates that for all practical purposes, imperfections in chronometry have been largely ignored.

Biological systems do not have it so easy. Biological clocks were not “engineered” on top of a physical phenomenon like the oscillation of a quartz crystal. Rather, biological wetware must keep time over many scales using physiological, neural, and biochemical mechanisms. Biological clocks are typically described as nonlinear dynamical systems exhibiting limit cycle behavior where the phase of the system advances monotonically with the passage of time. For example, circadian rhythms and other longer-term processes highlight the importance of external cues in the timekeeping process. Circadian and circannual rhythms, for example, are regulated by changes in daylength, temperature, and other environmental cues.

So, while uncertainty in time is justifiably neglected in the design and analysis of most engineering control systems, perfect timekeeping is a poor assumption for the modeling and analysis of biological control systems. Indeed, timekeeping during simple human motor control tasks involves errors of around 10% of the movement cycle duration. Despite this extremely high level of temporal imprecision, the overwhelming majority of computational models of the human motor control makes the implicit assumptions that time is known. Who knows what happens to any of these analyses when our assumption about perfect timekeeping is relaxed?

These three papers begin to address this question:

S. M. LaValle and M. B. Egerstedt, “On time: Clocks, chronometers, and open-loop control,” in Proc. IEEE Int. Conf. on Decision Control, 2007, pp. 1916–1922.

S. G. Carver, E. S. Fortune, and N. J. Cowan, “State-estimation and cooperative control with uncertain time,” in Proc. Amer. Control Conf., 2013, in press.

A. Lamperski and N. J. Cowan, “Time-changed linear quadratic regulators,” in Proc. Euro. Control Conf., 2013, in press.

Written by Noah J. Cowan with Eric S. Fortune, Andrew Lamperski and Sean G. Carver.