Title: Efficient and Robust Techniques for the Simulation of Fast/Slow Systems Speaker: Ting Mei, University of MinnesotaDate/Time: Monday, August 7, 2006, 9:00 – 10:00 am Location: CSRI Building, Room 90 (Sandia NM) Brief Abstract: Signals with widely separated time scales arise in many electrical systems. For such systems, conventional SPICE-like transient simulation is often extremely inefficient. One category of efficient techniques of solving fast/slow systems is envelope-following methods. However, envelope-following methods face special challenges when applied to oscillators because of their fundamental property of dynamically-changing frequencies. In this talk, we present a novel and robust approach for oscillator envelope following. Our method combines, unifies and extends ideas from two prior oscillator envelope-following approaches, Petzold's method and the WaMPDE. Our technique uses two extra system unknowns, as well as two extra ``phase condition'' equations, to track quantities related to dynamical frequency/time-period changes. These advances confer significant robustness without appreciable computational overhead. Furthermore, we show that a modification of our technique can extend its applicability to non-autonomous circuits, with the help of an efficient least squares solution technique. This leads to a general purpose approach which is much easier to solve than previous phase condition based envelope-following method, further improving numerically robustness dramatically. We validate our method on a variety of autonomous and non-autonomous circuits, including a PLL in transition to lock. Our technique provides speedups of of 1-2 orders of magnitude over transient simulation, while obtaining results that are equally or more accurate.CSRI POC: Scott Hutchinson, (505) 845-7996 |