Chapter 1
Introduction

Humans are a remarkable species. For most of our history, we have used our intellectual ability to create and develop many different tools and processes to assist us and ease our lives. Since the days our ancestors discovered how to control fire, around 300,000 years ago, we have achieved an exponential technological progress. From the invention of wheeled vehicles, around 6,000 years ago, to the transistor, invented just 70 years ago, many were the technological advances that have drastically changed the way we experience and perceive our reality.

The last few decades have seen an unprecedented surge of technological advancement, particularly in the area of computer science, resulting in some of the most revolutionary human inventions yet: we have developed personal desktop and portable computers, as well as a global network that interconnects all kinds of computerized devices, aptly called the Internet. Despite the fact that they have been in existence for an extremely short time, these technologies have transformed, and will continue to transform, the way our world and society work, at a very fundamental level and at an incredibly fast pace.

1.1 The Rise of Cyber-Physical Systems

Interestingly, once the Internet was in place, we quickly achieved the power to extend it to our traditional tools and appliances, which then became "interconnected". One of the first "tools" ever connected to the Internet was the Carnegie Mellon University Computer Science Department's Coke Machine, in the early 1980s [19], which was able to report its stock and label it as "cold" or not, depending on how much time it had been inside the machine. An idea began to spread: a vision of an interconnected world where information on most everyday objects was accessible.

Since then, scientists and engineers have developed this idea into a concept that is known as the "Internet of Things" (IoT). The idea started small, considering scenarios where radio-frequency identification allowed the "tagging" and managing of objects by computers. Each object would carry a radio-frequency identification (RFID) tag, a small, traceable chip which could be wirelessly scanned by a nearby RFID reader. The RFID tag enabled the automatic identification of the object and allowed it to be traced/managed through the Internet.

The continued advances in miniaturization allowed us to go beyond the simple tagging and identification of everyday objects. As predicted by Gordon Moore, back in 1965, the amount of computing power in integrated circuits has been doubling every 18 months for the last 50 years [20]. The remarkable work of computer industry engineers and scientists has led to many new technologies. The continuous integration of computational resources into all kinds of objects made our tools "intelligent". Everything from light bulbs to refrigerators, microwaves, and coffee machines will soon be connected to the Internet. In fact, some studies estimate that we will have an IoT with 26 billion connected devices by 2020 [21].

We can see evidence of this trend all around us. The Internet now interconnects a large number of highly heterogeneous devices, from traditional desktop PCs to laptops, tablets, and smartphones.

For example, the area of sensing technologies and wireless sensor networks (WSNs) is becoming increasingly prominent. WSNs are composed of dozens or even hundreds of autonomous "sensor nodes", small computerized devices that are capable of collecting physical world data and forwarding it by means of wireless communication. They can be used to monitor environmental luminosity, temperature, pressure, sound, and many other parameters, and can be spatially distributed in an ad hoc fashion. These technologies have been receiving a great deal of attention from the research community due to their potential in almost every application area. In fact, WSN deployments can now be found in many industrial, medical, and domestic environments. Recent studies in WSNs have brought great advancements in this area, namely in terms of energy efficiency and integration capabilities, with sensors being provided as services [22 23], accessible through the Internet [24]. Sensors are now indispensable devices, for they allow us to collect data from real-world phenomena, handle this data in digital form, and ultimately extend the Internet to the physical world.

In fact, the number of sensors that nowadays can be deployed on humans can turn them into walking sensor networks. Humans can use smart-shirts; carry a smartphone with several sensors and networking capabilities (e.g. global system for mobile communications (GSM), Bluetooth, long-term evolution (LTE)); and use Google glasses, iPods, smart watches, and shoes with sensors. In terms of sensing applied to individual users, Bosch Sensory Swarms and the Qualcomm Swarm Lab at UC Berkeley estimate that the number of sensors in personal devices can add up to 1000 wireless sensors per person, to be deployed over the next 10 to 15 years [25], resulting in large amounts of data being available for processing, and allowing a wide range of sensing applications to be deployed. This reality depends, of course, on the drastic reduction of sensor production costs, which are expected to come down to negligible values over time, as with most silicon-based hardware [26].

As for automated actuation, the world has seen a gradual increase in the number of installed robots per year. The 2015 World Robot Statistics study, issued by the International Federation of Robotics (IFR) [27], indicates that the total number of professional service robots sold in 2014 rose by 11.5% compared to 2013, from 21,712 to 24,207 units. IFR expects that, for the 2015-2018 period, sales of service robots for professional use will increase to about 152,375 units, while sales of robots for personal use will reach about 35 million units, with a total estimated value of about $40 billion. Global sales of industrial robots, on the other hand, will experience a yearly growth of 15% until 2018, while the number of sold units will double to around 400,000.

Interwoven with the concept of IoT is the concept of cyber-physical systems (CPSs), which consist in the sensing and control of physical phenomena through networks of devices that work together to achieve common goals. These CPSs represent a confluence of robotics, wireless sensor networks, mobile computing, and the IoT, to achieve highly monitored, easily controlled, and adaptable environments.

The IoT and CPS concepts have been pushed by two distinct communities. IoT was initially developed using a computer science perspective, mostly supported by the European Commission. The goal was to develop a network of smart objects with self-configuration capabilities on top of the current Internet. This development effort included hardware, software, standards, and interoperable communication protocols and languages that describe these intelligent devices [28]. IoT builds on several requirements, namely the development of intelligence in devices, interfaces and services; the assurance of security and privacy; systems integration; communication interoperability; and data "semantization" and management [29].

On the other hand, the concept of CPSs was initially supported by the US National Science Foundation (NSF). CPSs stem from an engineering perspective and concern the control and monitoring of physical environments and phenomena through sensing and actuation systems consisting of several distributed computing devices [30]. These systems are mostly interdisciplinary, requiring expertise and skills in mathematical abstractions (algorithms, processes) that model physical phenomena, smart devices and services, effective actuation, security and privacy, systems integration, communication, and data processing [31].

Thus, IoT tended to focus more on openness and the networking of intelligent devices, while CPSs were more concerned with applicability, modeling of physical processes, and problem solving, often through closed-looped systems. While their core philosophy and focus were initially different, their many similarities, such as intensive information processing, comprehensive intelligent services, and efficient interconnection and data exchange, have led to both terms being used interchangeably [32] without clearly identified borders [30].

CPSs combine elements from robotics, wireless sensor networks, and mobile computing, among others, to achieve specific goals. From industrial applications that monitor and actuate on several industrial processes, to social applications that aggregate data from various users in order to achieve goals, such as reducing pollution and traffic in metropolitan areas, CPSs can encompass a multitude of domains. For example, improvement of personal health can be achieved through body networks that integrate the user's vital signs and activity levels with environmental information on pollutants or noise to suggest healthier and more pleasant walking routes, restaurants, and leisure activities. CPSs can also be used in transportation, as many modern vehicles feature cruise control systems that maintain the automobile's speed or perform parking maneuvers, not to mention autonomous driving. All these systems combine sensors, actuators, and the computational capabilities of the devices to achieve the desired results. In fact, these sensors and actuators can be used not only in individual objects but also in structures and buildings in order to monitor, for example, their structural health.

While IoT and CPS technologies do exist, current systems...