Metric Based Multi-Timescale Control for Reducing Power in Embedded Systems

Abstract

Digital control for embedded systems often requires low-power, hard real-time computation to satisfy high control-loop bandwidth, low latency, and low-power requirements. In particular, the emerging applications of Micro Electro-Mechanical Systems (MEMS) sensors, and their increasing integration, presents a challenging requirement to embed ultra-low power digital control architectures for these lithographically formed micro-structures. Controlling electromechanical structures of such a small scale, using naive digital controllers, can be prohibitively expensive (both in power and cost for portable or battery operated applications.) In this paper, we describe the potential for control systems to be transformed into a set of co-operating parallel linear systems and demonstrate, for the first time, that this parallelization can reduce the total number of instructions executed, thereby reducing power, at the expense of controlled loss in control fidelity. Since the error tolerance of linear feedback control systems is mathematically well-posed, this technique opens up a new, independent dimension for system optimization. We present a novel Computer-Aided Design (CAD) method to evaluate control fidelity, with varying timescales on the controller, and analyze the trade-off between performance and power dissipation. A CAD Metric for control fidelity is proposed and we demonstrate the potential for power savings using this decomposition on two different control problems.