Analog Circuit Modeling in SystemC

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The theoretical aspects of the modeling have been discussed in part-1 of this paper. The part-II of the paper deals with the practical implementation of analog fuzzy logic based systems (FLS). The designing of a fuzzy logic based system has been automated by the development of a software tool, FACDEng, the Fuzzy Analog Controller Design Engineer. The designs proposed by FACDEng are based on easily available and inexpensive operational amplifiers and a few more passive components. The FACDEng does not need the FLS designer to be an expert in fuzzy logic or an analog circuit design expert. FACDEng also generates net lists of the designed modules. These net lists allow the designer to simulate the designs in OrCAD and verify the performance of designs in few minutes. The design time is considerably shortened, thus allowing the designer to focus on practical implementations and validation of the models. Further the tool has academic value as it can help instructor in classroom teaching of the fuzzy systems designs. The tool is expected to be made available to designers free of charge.

IEEE Transactions on Fuzzy Systems, 1997

Sampled-analog circuit techniques are exploited in an application-specific integrated fuzzy controller design. A circuit library comprising a sample-and-hold amplifier, positive and negative ramp amplifiers, an inference cell, adder, and weighted adder amplifiers, and a divider unit was developed for this purpose. Any expert system of piecewise linear input membership functions, conjunctive rules and singleton output classes can be implemented with this library. The library was implemented in a 1.2 m double-metal double-poly CMOS technology. Test results indicate excellent linearity and accuracy in full 5-V railto-rail operation in all units. A controller of four inputs, 16 rules, and two outputs fabricated with these library units occupies 1.76 mm 2 silicon. Test results indicate full functionality. The measured speed, 85 k samples per second, is limited by the unbuffered outputs. Sampling rate can be increased by 50% in those applications where pipelining is permissible. Index Terms-Controller, sampled analog. I. INTRODUCTION F UZZY logic has been developed over the past three decades into a widely applied technique in classification and control engineering. This logic can be implemented in one of the following forms: 1) software simulation, which is highly cost effective if volume production is not demanded, and neither portability nor processing speed is critical; 2) microprocessor or microcontroller implementation, which is most suitable for low-volume production of slow but portable systems; 3) using a field-programmable or reconfigurable fuzzy processor chip, which offers high speed to portable systems in low-volume production; 4) using an application-specific (ASIC) fuzzy processor chip, which offers high speed in a cost-effective way for portable systems in high-volume production [1]. Quite obviously, the last two of these implementation styles require fuzzy-specific chip design. Indeed, numerous simulated or partially integrated architectures have been proposed in the past decade to fulfill this need [2]-[12]. Publications on fully integrated fuzzy-system chips, however, are relatively rare. One of these involves a digital fuzzy-controller [13].

IEEE Transactions on Fuzzy Systems, 1997

This paper discusses architectural and circuit-level aspects related to hardware realizations of fuzzy controllers. A brief overview on fuzzy inference methods is given focusing on chip implementation. The singleton or zero-order Sugeno's method is chosen since it offers a good tradeoff between hardware simplicity and control efficiency. The CMOS microcontroller described herein processes information in the current-domain, but input-output signals are represented as voltage to ease communications with conventional control circuitry. Programming functionalities are added by combining analog and digital techniques, giving rise to a versatile microcontroller, capable of solving different control problems. After identifying the basic component blocks, the circuits used for their implementation are discussed and compared with other alternatives. This study is illustrated with the experimental results of prototypes integrated in different CMOS technologies.

1996 IEEE International Symposium on Circuits and Systems. Circuits and Systems Connecting the World. ISCAS 96

This paper describes a programmable fuzzy controller chip designed with mixed-signal IC techniques. Its input and output signals are analog to directly interact with the information from the real world. The programmability interface is digital and the output signal is also given in digital format to allow easy embedding into digital processing environments. Experimental results from a prototype integrated in a 2.4-µm CMOS process are included.

1998 Midwest Symposium on Circuits and Systems (Cat. No. 98CB36268), 1999

A mixed-signal VLSI circuit that efficiently maps the processing required for a Fuzzy Knowledge-Based Controller (FKBC) is presented. The proposed architecture is constituted by digitallyprogrammable continuous-time blocks to perform inference and switched-current memory cells to store in current-mode the partial information resulting form its pipeline operation. This FKBC is intended to provide multidimensional nonlinearfunction approximation for switching power converters optimum control. Details of a new pulse-width-modulated defuzzyfication scheme are included. Transistor level post-layout simulation results for a 0.8 µm CMOS technology are included which validate the different blocks operation, their compatibility and the feasibility of the sequential architecture.

Journal of Integrated Circuits and Systems, 2004

A digitally programmable analog Fuzzy Logic Controller (FLC) is presented. Input and output signals are processed in the analog domain whereas the parameters of the controller are stored in a built-in digital memory. Some new functional blocks have been designed whereas others were improved towards the optimization of the power consumption, the speed and the modularity while keeping a reasonable accuracy, as it is needed in several analogue signal processing applications. A nine-rules, two-inputs and one-output prototype was fabricated and successfully tested using a standard CMOS 2.4μ technology, showing good agreement with the expected performances, namely: a 2.7% RMSE, from 2.22 to 5.26 Mflips (Mega fuzzy logic inferences per second) at the pin terminals (@CL=13pF), 933 μW power consumption per rule (@Vdd=5V) and 5 bits of resolution. Since the circuit is intended for a subsystem embedded in an application chip (@CL≤ 5pF) up to 8 Mflips may be expected.

2008 First International Conference on Emerging Trends in Engineering and Technology, 2008

Limits to precision impose limits to the complexity of analog circuits, hence fuzzy analog controllers are usually oriented to fast low-power systems with low medium complexity. This paper presents a strategy to preserve most of the advantages of an analog implementation, while allowing a marked increment in system complexity. A digitally-programmable analogue Fuzzy Logic Controller (FLC) is presented. are usually oriented to fast low-power systems with low medium complexity. This paper presents a strategy to preserve most of the advantages of an analog implementation, while allowing a marked increment in system complexity. A digitally-programmable analogue Fuzzy Logic Controller (FLC) is presented. The circuits have been simulated using Tanner Tools.

Proceedings Design, Automation and Test in Europe, 1998

A new approach to mixed-signal circuit interfacing based on fuzzy logic models is presented. Due to their continuous rather than discrete character, fuzzy logic models offer a significant improvement compared with the classical D-A interface models. Fuzzy logic D-A interfaces can represent the boundary between the digital and analogue worlds accurately without a significant loss of computational efficiency. The potential of mixed-signal interfacing based on fuzzy logic is demonstrated by an example of spike propagation from the digital to analogue world. A model of inertial propagation delay and non-linear DC gain suitable for fuzzy logic gates is also suggested.

Analog Integrated Circuits and Signal Processing, 2000

A mixed analog-digital fuzzy logic inference processor chip, designed in a 0.35-µm CMOS technology, is presented. The analog fuzzy engine is based on a novel current-mode CMOS circuit used for the implementation of fuzzy partition membership functions. The architecture consists of a 3 inputs-1 output analog fuzzy engine, internal digital registers to store the parameters of the fuzzy controller, and a digital subsystem that allows the programmability of the fuzzy controller via an I 2 C interface. The architecture, circuits, and some Cadence Spectre simulations are presented.

This paper shows a method to implement fuzzy controllers with analog electronic circuits. A fuzzy controller is defined by a collection of fuzzy IF-THEN rules and a set of membership functions characterizing the linguistic terms associated with the input and output of the fuzzy controller. In this paper an electronic circuit with Operational Amplifiers is designed from a set of membership functions and fuzzy IF-THEN rules.