Evolvable hardware (EH) is a field focusing on the use of

evolutionary algorithm In computational intelligence (CI), an evolutionary algorithm (EA) is a subset of evolutionary computation, a generic population-based metaheuristic optimization algorithm. An EA uses mechanisms inspired by biological evolution, such as reproduct ...

s (EA) to create specialized

electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

without manual engineering. It brings together reconfigurable hardware, evolutionary computation,

fault tolerance Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the ...

and

autonomous systems An autonomous robot is a robot that acts without recourse to human control. The first autonomous robots environment were known as Elmer and Elsie, which were constructed in the late 1940s by W. Grey Walter. They were the first robots in history t ...

. Evolvable hardware refers to hardware that can change its architecture and behavior dynamically and autonomously by interacting with its environment.

Introduction

In its most fundamental form an

manipulates a population of individuals where each individual describes how to construct a candidate circuit. Each circuit is assigned a fitness, which indicates how well a candidate circuit satisfies the design specification. The evolutionary algorithm uses stochastic operators to evolve new circuit configurations from existing ones. Done properly, over time the evolutionary algorithm will evolve a circuit configuration that exhibits desirable behavior. Each candidate circuit can either be simulated or physically implemented in a reconfigurable device. Typical reconfigurable devices are field-programmable gate arrays (for digital designs) or

field-programmable analog array A field-programmable analog array (FPAA) is an integrated circuit device containing computational analog blocks (CAB) and interconnects between these blocks offering field-programmability. Unlike their digital cousin, the FPGA, the devices tend to ...

s (for analog designs). At a lower level of abstraction are the field-programmable

transistor array Transistor arrays consist of two or more transistors on a common substrate. Unlike more highly integrated circuits, the transistors can be used individually like discrete transistors. That is, the transistors in the array are not connected to e ...

s that can implement either digital or analog designs. The concept was pioneered by Adrian Thompson at the University of Sussex, England, who in 1996 used an FPGA to evolve a tone discriminator that used fewer than 40 programmable logic gates, and had no clock signal. This is a remarkably small design for such a device, and relied on exploiting peculiarities of the hardware that engineers normally avoid. For example, one group of gates has no logical connection to the rest of the circuit, yet is crucial to its function.

Motivation

In many cases, conventional design methods (formulas, etc.) can be used to design a circuit. But in other cases, the design specification doesn't provide sufficient information to permit using conventional design methods. For example, the specification may only state desired behavior of the target hardware. In other cases, an existing circuit must adapt—i.e., modify its configuration—to compensate for faults or perhaps a changing operational environment. For instance, deep-space probes may encounter sudden high radiation environments, which alter a circuit's performance; the circuit must self-adapt to restore as much of the original behavior as possible.

Finding the fitness of an evolved circuit

The fitness of an evolved circuit is a measure of how well the circuit matches the design specification. Fitness in evolvable hardware problems is determined via two methods: * extrinsic evolution: all circuits are simulated to see how they perform, * intrinsic evolution: physical tests are run on actual hardware. In extrinsic evolution, only the final best solution in the final population of the evolutionary algorithm is physically implemented, whereas with intrinsic evolution every individual in every generation of the EA's population is physically realized and tested.

Future research directions

Evolvable hardware problems fall into two categories: original design and adaptive systems. Original design uses evolutionary algorithms to design a system that meets a predefined specification. Adaptive systems reconfigure an existing design to counteract faults or a changed operational environment. Original design of digital systems is not of much interest because industry already can synthesize enormously complex circuitry. For example, one can buy intellectual property cores to synthesize USB port circuitry, ethernet microcontrollers and even entire RISC processors. Some research into original design still yields useful results, for example genetic algorithms have been used to design logic systems with integrated fault detection that outperform hand designed equivalents. Original design of analog circuitry is still a wide-open research area. Indeed, the analog design industry is nowhere near as mature as is the digital design industry.

Adaptive system An adaptive system is a set of interacting or interdependent entities, real or abstract, forming an integrated whole that together are able to respond to environmental changes or changes in the interacting parts, in a way analogous to either conti ...

s has been and remains an area of intense interest.

References

External links

NASA-DoD-sponsored conference 2004

NASA-DoD-sponsored conference 2005

NASA/ESA Conference on Adaptive Hardware and Systems (AHS-2006)

* NASA used a genetic algorithm to design a nove
antenna
(se
PDF
paper for details)
Evolutionary Electronics at the University of Sussex
Electronic design