Artificial intelligence tools can aid sensor systems
At least seven artificial intelligence (AI) tools can be useful when applied to sensor systems: knowledge-based systems, fuzzy logic, automatic knowledge acquisition, neural networks, genetic algorithms, case-based reasoning, and ambient-intelligence. See diagrams.
Seven artificial intelligence (AI) tools are reviewed that have proved to be useful with sensor systems. They are: knowledge-based systems, fuzzy logic, automatic knowledge acquisition, neural networks, genetic algorithms, case-based reasoning, and ambient-intelligence. Each AI tool is outlined, together with some examples of its use with sensor systems. Applications of these tools within sensor systems have become more widespread due to the power and affordability of present-day computers. Many new sensor applications may emerge, and greater use may be made of hybrid tools that combine the strengths of two or more of the tools reviewed.
The tools and methods reviewed here have minimal computation complexity and can be implemented with small sensor systems, single sensors, or system arrays with low-capability microcontrollers. The appropriate deployment of the new AI tools will contribute to the creation of more competitive sensor systems and applications. Other technological developments in AI that will impact sensor systems include data mining techniques, multi-agent systems, and distributed self-organizing systems. Ambient sensing involves integrating many microelectronic processors and sensors into everyday objects to make them “smart.” They can explore their environment, communicate with other smart things, and interact with humans. Advice provided aims to help users cope with their tasks in intuitive ways, but the repercussion of such integration into our lives is difficult to predict. Using ambient intelligence and a mix of AI tools is an effort to use the best of each technology. The concepts are generically applicable across industrial processes, and this research is intended to show that the concepts work in practice.
Creating smarter sensor systems
Sensor systems can be improved using artificial intelligence (AI).  AI emerged as a computer science discipline in the mid 1950s, [2,3] and it has produced a number of powerful tools that are useful in sensor systems for automatically solving problems that would normally require human intelligence. Seven such tools are here: knowledge-based systems, fuzzy logic, inductive learning, neural networks, genetic algorithms, case-based reasoning, and ambient-intelligence.
AI systems have been improving,  and new advances in machine intelligence are creating seamless interactions between people and digital sensor systems. Although the introduction of AI into industry has been slow, it promises to bring improvements in flexibility, reconfigurability, and reliability. New machine systems are exceeding human performance in increasing numbers of tasks. As they merge with us more intimately, and we combine our brain power with computer capacity to deliberate, analyze, deduce, communicate, and invent, then we may be on the threshold of a new age of machine intelligence. 
AI (or machine intelligence) combines a wide variety of advanced technologies to give machines an ability to learn, adapt, make decisions, and display new behaviors.  This is achieved using technologies such as neural networks,  expert systems, [8,9] self-organizing maps,  fuzzy logic,  and genetic algorithms,  and that machine intelligence technology has been developed through its application to many areas where sensor information has needed to be interpreted and processed, for example:
- Assembly [1, 14]
- Biosensors 
- Building modeling 
- Computer vision 
- Cutting tool diagnosis 
- Environmental engineering 
- Force sensing 
- Health monitoring 
- Human-computer interaction [19, 20]
- Internet use [21, 22]
- Laser milling 
- Maintenance and inspection [25, 26]
- Powered assistance [23, 24]
- Robotics [27, 28]
- Sensor networks 
- Teleoperation. [33, 34]
These developments in machine intelligence are being introduced into ever more complex sensor systems. The click of a mouse, the flick of a switch, or the thought of a brain might convert almost any sensor data to information and transport it to you. Recent examples of this research work are provided, which include work at the University of Portsmouth. Seven areas where AI can help sensor systems follow.
1. Knowledge-based systems
Knowledge-based (or expert) systems are computer programs embodying knowledge about a domain for solving problems related to that domain.  An expert system usually has two main elements, a knowledge base and an inference mechanism. The knowledge base contains domain knowledge which may be expressed as a combination of ‘IF–THEN' rules, factual statements, frames, objects, procedures, and cases. An inference mechanism manipulates stored knowledge to produce solutions to problems. Knowledge manipulation methods include using inheritance and constraints (in a frame-based or object-oriented expert system), retrieval and adaptation of case examples (in case-based systems), and the application of inference rules (in rule-based systems), according to some control procedure (forward or backward chaining) and search strategy (depth or breadth first). 
A rule-based system describes knowledge of a system in terms of IF… THEN... ELSE. Specific knowledge can be used to make decisions. These systems are good at representing knowledge and decisions in a way that is understandable to humans. Due to the rigid rule-base structure they are less good at handling uncertainty and are poor at handling imprecision. A typical rule-based system has four basic components: a list of rules or rule base, which is a specific type of knowledge base; an inference engine [35, 36] or semantic reasoner, which infers information or takes action based on the interaction of input and the rule base; temporary working memory; and a user interface or other connection to the outside world through which input and output signals are received and sent. 
The concept in case-based reasoning is to adapt solutions from previous problems to current problems. These solutions are stored in a database and can represent the experience of human specialists. When a problem occurs that a system has not experienced, it compares with previous cases and selects one that is closest to the current problem. It then acts upon the solution given and updates the database depending upon the success or failure of the action.  Case-based reasoning systems are often considered to be an extension of rule-based systems. They are good at representing knowledge in a way that is clear to humans, but they also have the ability to learn from past examples by generating additional new cases.
2. Case-based reasoning
Case-based reasoning has been formalized for purposes of computer reasoning as a four-step process:
1) Retrieve: Given a target problem, retrieve cases from memory that are relevant to solving it. A case consists of a problem, its solution, and, typically, annotations about how the solution was derived.
2) Reuse: Map the solution from the previous case to the target problem. This may involve adapting the solution as needed to fit the new situation.
3) Revise: Having mapped the previous solution to the target situation, test the new solution in the real world (or a simulation) and, if necessary, revise.
4) Retain: After the solution has been successfully adapted to the target problem, store the resulting experience as a new case in memory.
Critics argue that it is an approach that accepts anecdotal evidence as its main operating principle. Without statistically relevant data for backing and implicit generalization, there is no guarantee that the generalization is correct. However, all inductive reasoning where data is too scarce for statistical relevance is inherently based on anecdotal evidence. 
The concept in case-based reasoning (CBR) is to adapt solutions from previous problems to current problems. These solutions are stored in a database and represent the experience of human specialists. When a problem occurs that a system has not experienced, it compares with previous cases and selects one closest to the current problem. It then acts upon the solution given and updates the database depending upon the success or failure of the action.
CBR systems are often considered to be an extension of rule-based systems.  As with rule-based systems, CBR systems are good at representing knowledge in a way that is clear to humans; however, CBR systems also have the ability to learn from past examples by generating additional new cases. Figure 1 shows a CBR system.
Many expert systems are developed using programs known as “shells,” which are ready-made expert systems complete with inferencing and knowledge storage facilities but without the domain knowledge. Some sophisticated expert systems are constructed with the help of “development environments.” The latter are more flexible than shells in that they also provide means for users to implement their own inferencing and knowledge representation methods. [Some details about expert systems shells and development environments are in Ref. 40.]
Expert systems are probably the most mature among tools mentioned here, with many commercial shells and development tools available to facilitate their construction. Consequently, once the domain knowledge to be incorporated in an expert system has been extracted, the process of building the system is relatively simple. The ease with which expert systems can be developed has led to a large number of applications of the tool. In sensor systems, applications can be found for a variety of tasks, including selection of sensor inputs, interpreting signals, condition monitoring, fault diagnosis, machine and process control, machine design, process planning, production scheduling, and system configuring. Some examples of specific tasks undertaken by expert systems are:
- Assembly 
- Automatic programming 
- Controlling intelligent complex vehicles 
- Planning inspection 
- Predicting risk of disease 
- Selecting tools and machining strategies 
- Sequence planning 
- Controlling plant growth. 
[More information on the technology of expert systems is in 3, 49.]
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