Massimo Petricca

An automated framework for generating variable-accuracy battery models from datasheet information

Models based on an electrical circuit equivalent have become the most popular choice for modeling the behavior of batteries, thanks to their ease of co-simulation with other parts of a digital system. Such circuit models are actually model templates: the specific values of their electrical elements must be derived by the analysis of the specific battery devices to be modeled. This process requires either to measure the battery characteristics or to derive them from the datasheet. In the latter case, however, very often not all information are available and the model fitting becomes then unfeasible. In this paper we present a methodology for deriving, in a semi-automatic way, circuit equivalent battery models solely from data available in a battery datasheet. In order to account for the different amount of information available, we introduce the concept of “level” of a model, so that models with different accuracy can be derived depending on the available data. The methodology requires only minimal intervention by the designer and it automatically generates MATLAB models once the required data for the corresponding model level are transcribed from the datasheet. Simulation results show that our methodology allows to accurately reconstruct the information reported in the datasheet as well as to derive missing ones.

Imprecise arithmetic for low power image processing

Sometimes reducing the precision of a numerical processor, by introducing errors, can lead to significant performance (delay, area and power dissipation) improvements without compromising the overall quality of the processing. In this work, we show how to perform the two basic operations, addition and multiplication, in an imprecise manner by simplifying the hardware implementation. With the proposed “sloppy” operations, we obtain a reduction in delay, area and power dissipation, and the error introduced is still acceptable for applications such as image processing.

Power efficient design of parallel/serial FIR filters in RNS

It is well known that the Residue Number System (RNS) provides an efficient implementation of parallel FIR filters especially when the filter order and the dynamic range are high. The two main drawbacks of RNS, need of converters and coding overhead, make a serialized implementation of the FIR filter potentially disadvantageous with respect to filters implemented in the conventional number systems. In this work, we show a number of solutions which demonstrate that the power efficiency of RNS FIR filters implemented serially is maintained in ASIC technology, while in modern FPGA technology RNS implementations are less efficient.

Automated generation of battery aging models from datasheets

The de-facto standard approach in battery modeling consists of the definition of a generic model template in terms of an equivalent electric circuit, which is then populated either using data obtained from direct measurements on actual devices or by some extrapolation of battery characteristics available from datasheets. These models typically describe only intra-cycle effects, that is, those manifesting within a single charge/discharge cycle of a battery. However, basic battery dynamics, during a single discharge, cannot provide a true estimate of the actual lifetime of the battery, e.g., how its usability decreases due to long-term and irreversible effects, such as the fading of capacity due to aging or to repeated cycling. While some solutions in the literature provide answers to this problem by proposing suitable models for these effects, they do not provide solutions for how to incorporate them into a generic model template. In this work we propose a method to include inter-cycle battery effects into a reference model template in an automated way, and using solely data reported by battery manufacturers. Flexibility and accuracy of the proposed strategy are demonstrated by modeling a commercial lithium iron phosphate battery, whose datasheet provides long-term capacity fading information.

Computer-aided design of electrical energy systems

Electrical energy systems (EESs) include energy generation, distribution, storage, and consumption, and involve many diverse components and sub-systems to implement these tasks. This paper represents a first step towards the computer-aided design for EESs, encompassing modeling, simulation, design and optimization of these systems. CAD for EESs is a challenging task that mandates a multidisciplinary and heterogeneous approach. We identify similarities and differences between electrical energy systems and electronics systems in order to inherit as much as possible the profound legacy resources of electronic design automation (EDA). We introduce fundamental concepts, from the general problem formulation to the development and deployment of efficient, scalable, and versatile CAD and EDA methods and framework for the optimal or near-optimal EESs.

Degrading precision arithmetic for low power signal processing

Sometimes reducing the power dissipation of resource constrained electronic systems, such as those built for deep-space probes or for wearable devices is a top priority. In signal processing, it is possible to have an acceptable quality of the signal even introducing some errors. In this work, we analyze two methods to degrade the precision of arithmetic operations in DSP to save power. The first method is based on disabling the lower (least-significant) portion of the datapath by clock-gating and forcing zeros. The second method is based on lowering the supply voltage and re-designing the carry-chains in the datapath to adapt to the increased delays.

Characterization of RNS multiply-add units for power efficient DSP

In the past decades, the Residue Number System (RNS) has been adopted in DSP as an alternative to the traditional twos complement number system (TCS) because of the savings in area, higher speed and reduced power dissipation. In this work, we perform a comprehensive Design Space Exploration (DSE) for a fused multiply-add unit by taking into account four metrics: area, delay, power consumption, and switching activity. The results of the DSE are verified against the TCS and RNS implementation of parallel FIR filters of different characteristics. In both the DSE and the filter implementation, we consider two design corners: maximum speed and minimum area. The experimental results demonstrate that for high data rates and high order filters, the RNS implementation is more power efficient than the TCS because of the reduced switching activity and the larger amount of low-power cells placed in the unit.

Truncated multipliers through power-gating for degrading precision arithmetic

When reducing the power dissipation of resource constrained electronic systems is a priority, some precision can be traded-off for lower power consumption. In signal processing, it is possible to have an acceptable quality of the signal even introducing some errors. In this work, we apply power-gating to multipliers to obtain a programmable truncated multiplier. The method consists in disabling the least-significant columns of the multiplier by power-gating logic in the partial products generation and accumulation array.

Design of large polyphase filters in the Quadratic Residue Number System

In this work, we revisit the implementation of polyphase filter banks in Quadratic Residue Number System (QRNS) for banks with a large number of channels by developing a new design methodology suitable for large systems required in the new generation of satellites. Furthermore, we compare the QRNS filter bank with an equivalent bank implemented in the traditional Complex Twos Complement System (CTCS) in terms of throughput, area and power dissipation. The results for large filter banks confirm the earnings in power consumption by using the QRNS.

Multiple Constant Multiplication through Residue Number System

Several algorithms have been developed over the years to reduce the number of additions needed for Multiple Constant Multiplication (MCM) and optimize the area. In this work, we present an approach to MCM which is based on the properties of the Residue Number System (RNS). Experimental results on a set of digital filters, which represent a typical application of MCM, show that the proposed RNS method has a lower power dissipation in most cases, and a reduced area for high throughput filters.