In general terms, actuators are devices which transform an input signal (usually an electrical signal) into motion. Examples of actuators include solenoids, pistons, motors and robots used in intelligent transport systems (ITS) applications, including vehicle brakes and moving barriers. Motors are mostly used when circular motions are needed, but can also be used for linear applications by transforming circular to linear motion with a bolt and screw. Some actuators are intrinsically linear, such as piezoelectric actuators.
Communications, particularly data communications, are the key to the development of effective ITS. All ITS are composed of a series of building blocks, or system elements, which communicate with each other. A straightforward definition of a communication link is that it's a channel which enables information which is generated in one location to be conveyed to another location. Communication links can be very simple (e.g. a piece of wire joining two circuits inside a piece of electronic equipment) or very complex (e.g. the system which conveys a signal from a TV camera above a motorway to the decoder in a control room via a satellite located 24,000 miles above the equator).
Communication links can be fixed links, using wires or optical fibres to convey information. However, others include an air path communications link (e.g. where there's a need to communicate with moving vehicles). The volumes of data to be transferred over these links can be substantial, particularly if the system design necessitates the transmission of maps, pictorial data or large databases.
Computer data storage, often called storage or memory, refers to computer components, devices and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer, that of information retention. It's one of the fundamental components of all modern computers and, coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s.
In contemporary usage, memory usually refers to a form of semiconductor storage known as random access memory (RAM) and sometimes other forms of fast but temporary storage. Similarly, storage today more commonly refers to mass storage - optical discs, forms of magnetic storage like hard disks, and other types slower than RAM but of a more permanent nature. Historically, memory and storage were respectively called primary storage and secondary storage.
The contemporary distinctions are helpful because they're also fundamental to the architecture of computers and ITS in general.
One element of an ITS is where a person interacts with, for example, a ticket machine, screen or steering wheel. This is known as the human-machine interface (HMI). 'Interface' is a hardware concept appropriate to a hardware-systems-oriented view of ITS. 'Interaction' is a wider concept involving all aspects of a user (e.g. a driver, a passenger or a traffic controller) in their use of a system. This can involve psychological and physical interaction, behavioural changes and even wider sociological factors. These 'softer' elements are increasingly important in the implementation of ITS.
Human factors (or ergonomics) is a systems-oriented discipline concerned with the fundamental understanding of interactions among people and other system elements, and the application of appropriate methods, theory and data to improve human well-being and overall system performance. Human factors is extremely important in the design of displays, but is also more generally important in the design of ITS systems and services.
A positioning system is a mechanism for determining the location of an object in space. Technologies for this task range from worldwide coverage with metre accuracy to workspace coverage with sub-millimetre accuracy.
Positioning systems can be broken down into more fundamental building blocks involving computers/memory/communications, for example, but they're identified as a useful building block because they're nearly always present in ITS.
ITS may make use of a variety of positioning techniques and technologies including, for example, Gyro, dead reckoning, rrestrial radio Cellular radioWi-Fi. However, the most ubiquitous form found in ITS involves satellite-based location (GPS - Global Positioning System, GNSS - Global Navigation Satellite System).
The EU Member States have agreed to develop and operate a new satellite navigation system called Galileo, which is expected to become operational around 2015.
Other Location Systems
Since the first computers appeared in the 1940s, computing power has continued to increase rapidly as processing methods and integration have evolved.
A central processing unit (CPU) is a machine that can execute computer programs. This broad definition can easily be applied to many early computers that existed long before the term CPU ever came into widespread usage. The form, design and implementation of CPUs have changed dramatically since the earliest examples, but their fundamental operation has remained much the same and processors are found throughout ITS.
A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For accuracy, all sensors need to be calibrated against known standards. Sensors are used in everyday objects such as touch-sensitive elevator buttons and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors including cars, machines, aerospace, medicine, manufacturing and robotics.
A sensor's sensitivity indicates how much the sensor's output changes when the measured quantity changes. Technological progress allows more and more sensors to be manufactured on a microscopic scale. In ITS, sensors are used, for example, to measure distance to objects (e.g. for collision warning systems) and to detect the presence or features of objects (e.g. vehicle classification systems).
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