In science, computing, and engineering, a black box is a system which can be viewed in terms of its inputs and outputs (or transfer characteristics ), without any knowledge of its internal workings. Its implementation is "opaque" (black). The term can be used to refer to many inner workings, such as those of a transistor , an engine , an algorithm , the human brain , or an institution or government .
30-424: A black box is a device, object, or system whose inner workings are unknown; only the "stimuli inputs" and "output reactions" are known characteristics. Black box may also refer to: Black box To analyze an open system with a typical "black box approach", only the behavior of the stimulus/response will be accounted for, to infer the (unknown) box . The usual representation of this "black box system"
60-460: A black box can be written in a table, in which, at each of a sequence of times, the states of the box's various parts, input and output, are recorded. Thus, using an example from Ashby , examining a box that has fallen from a flying saucer might lead to this protocol: Thus, every system, fundamentally, is investigated by the collection of a long protocol, drawn out in time, showing the sequence of input and output states. From this there follows
90-408: A black box is based on the "explanatory principle", the hypothesis of a causal relation between the input and the output . This principle states that input and output are distinct, that the system has observable (and relatable) inputs and outputs and that the system is black to the observer (non-openable). An observer makes observations over time. All observations of inputs and outputs of
120-403: A control loop including sensors , control algorithms, and actuators is arranged in an attempt to regulate a variable at a setpoint (SP). An everyday example is the cruise control on a road vehicle; where external influences such as hills would cause speed changes, and the driver has the ability to alter the desired set speed. The PID algorithm in the controller restores the actual speed to
150-417: A dynamical system . Its name comes from the information path in the system: process inputs (e.g., voltage applied to an electric motor ) have an effect on the process outputs (e.g., speed or torque of the motor), which is measured with sensors and processed by the controller; the result (the control signal) is "fed back" as input to the process, closing the loop. In the case of linear feedback systems,
180-430: A feedback controller is used to automatically control a process or operation. The control system compares the value or status of the process variable (PV) being controlled with the desired value or setpoint (SP), and applies the difference as a control signal to bring the process variable output of the plant to the same value as the setpoint. For sequential and combinational logic , software logic , such as in
210-405: A programmable logic controller , is used. Fundamentally, there are two types of control loop: open-loop control (feedforward), and closed-loop control (feedback). In open-loop control, the control action from the controller is independent of the "process output" (or "controlled process variable"). A good example of this is a central heating boiler controlled only by a timer, so that heat
240-629: A closed loop control system according to the British Standards Institution is "a control system possessing monitoring feedback, the deviation signal formed as a result of this feedback being used to control the action of a final control element in such a way as to tend to reduce the deviation to zero." A closed-loop controller or feedback controller is a control loop which incorporates feedback , in contrast to an open-loop controller or non-feedback controller . A closed-loop controller uses feedback to control states or outputs of
270-550: A series of mechanical actuators in the correct sequence to perform a task. For example, various electric and pneumatic transducers may fold and glue a cardboard box, fill it with the product and then seal it in an automatic packaging machine. PLC software can be written in many different ways – ladder diagrams, SFC ( sequential function charts ) or statement lists . On–off control uses a feedback controller that switches abruptly between two states. A simple bi-metallic domestic thermostat can be described as an on-off controller. When
300-772: Is a data flow diagram centered in the box. The opposite of a black box is a system where the inner components or logic are available for inspection, which is most commonly referred to as a white box (sometimes also known as a "clear box" or a "glass box"). The modern meaning of the term "black box" seems to have entered the English language around 1945. In electronic circuit theory the process of network synthesis from transfer functions , which led to electronic circuits being regarded as "black boxes" characterized by their response to signals applied to their ports , can be traced to Wilhelm Cauer who published his ideas in their most developed form in 1941. Although Cauer did not himself use
330-439: Is always used when testing the black box model. Data has to be written down before it is pulled for black box inputs. Black box theories are those theories defined only in terms of their function. The term can be applied in any field where some inquiry is made into the relations between aspects of the appearance of a system (exterior of the black box), with no attempt made to explain why those relations should exist (interior of
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#1732834160359360-532: Is an electronic technology that uses fuzzy logic instead of the two-value logic more commonly used in digital electronics . The range of control system implementation is from compact controllers often with dedicated software for a particular machine or device, to distributed control systems for industrial process control for a large physical plant . Logic systems and feedback controllers are usually implemented with programmable logic controllers . The Broadly Reconfigurable and Expandable Automation Device (BREAD)
390-401: Is applied for a constant time, regardless of the temperature of the building. The control action is the switching on/off of the boiler, but the controlled variable should be the building temperature, but is not because this is open-loop control of the boiler, which does not give closed-loop control of the temperature. In closed loop control, the control action from the controller is dependent on
420-473: Is even wider in application than professional studies: The child who tries to open a door has to manipulate the handle (the input) so as to produce the desired movement at the latch (the output); and he has to learn how to control the one by the other without being able to see the internal mechanism that links them. In our daily lives we are confronted at every turn with systems whose internal mechanisms are not fully open to inspection, and which must be treated by
450-593: Is going on to understand the mechanism of the brain, progress in treatment is also being made by observing patients' responses to stimuli. Control system A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops . It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial control systems which are used for controlling processes or machines. The control systems are designed via control engineering process. For continuously modulated control,
480-547: Is held in an inner situation away from facile investigations. The black box element of the definition is shown as being characterised by a system where observable elements enter a perhaps imaginary box with a set of different outputs emerging which are also observable. In humanities disciplines such as philosophy of mind and behaviorism , one of the uses of black box theory is to describe and understand psychological factors in fields such as marketing when applied to an analysis of consumer behaviour . Black Box theory
510-431: Is still in use as a programming method for PLCs. Logic controllers may respond to switches and sensors and can cause the machinery to start and stop various operations through the use of actuators . Logic controllers are used to sequence mechanical operations in many applications. Examples include elevators, washing machines and other systems with interrelated operations. An automatic sequential control system may trigger
540-410: The black box is an abstraction representing a class of concrete open system which can be viewed solely in terms of its stimuli inputs and output reactions : The constitution and structure of the box are altogether irrelevant to the approach under consideration, which is purely external or phenomenological. In other words, only the behavior of the system will be accounted for. The understanding of
570-401: The black box). In this context, Newton's theory of gravitation can be described as a black box theory. Specifically, the inquiry is focused upon a system that has no immediately apparent characteristics and therefore has only factors for consideration held within itself hidden from immediate observation. The observer is assumed ignorant in the first instance as the majority of available data
600-458: The box, there is active feedback in the box/observer relation, promoting what in control theory is called a feed forward architecture. The modeling process is the construction of a predictive mathematical model , using existing historic data (observation table). A developed black box model is a validated model when black-box testing methods ensures that it is, based solely on observable elements. With back testing, out of time data
630-419: The control of complex continuously varying systems. Basically, a measurement in a fuzzy logic system can be partly true. The rules of the system are written in natural language and translated into fuzzy logic. For example, the design for a furnace would start with: "If the temperature is too high, reduce the fuel to the furnace. If the temperature is too low, increase the fuel to the furnace." Measurements from
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#1732834160359660-417: The desired speed in an optimum way, with minimal delay or overshoot , by controlling the power output of the vehicle's engine. Control systems that include some sensing of the results they are trying to achieve are making use of feedback and can adapt to varying circumstances to some extent. Open-loop control systems do not make use of feedback, and run only in pre-arranged ways. Closed-loop controllers have
690-700: The following advantages over open-loop controllers: In some systems, closed-loop and open-loop control are used simultaneously. In such systems, the open-loop control is termed feedforward and serves to further improve reference tracking performance. A common closed-loop controller architecture is the PID controller . Logic control systems for industrial and commercial machinery were historically implemented by interconnected electrical relays and cam timers using ladder logic . Today, most such systems are constructed with microcontrollers or more specialized programmable logic controllers (PLCs). The notation of ladder logic
720-426: The fundamental deduction that all knowledge obtainable from a Black Box (of given input and output) is such as can be obtained by re-coding the protocol (the observation table ); all that, and nothing more. If the observer also controls input, the investigation turns into an experiment (illustration), and hypotheses about cause and effect can be tested directly. When the experimenter is also motivated to control
750-467: The methods appropriate to the Black Box. (...) This simple rule proved very effective and is an illustration of how the Black Box principle in cybernetics can be used to control situations that, if gone into deeply, may seem very complex. A further example of the Black Box principle is the treatment of mental patients. The human brain is certainly a Black Box, and while a great deal of neurological research
780-527: The process output. In the case of the boiler analogy this would include a thermostat to monitor the building temperature, and thereby feed back a signal to ensure the controller maintains the building at the temperature set on the thermostat. A closed loop controller therefore has a feedback loop which ensures the controller exerts a control action to give a process output the same as the "reference input" or "set point". For this reason, closed loop controllers are also called feedback controllers. The definition of
810-554: The real world (such as the temperature of a furnace) are fuzzified and logic is calculated arithmetic, as opposed to Boolean logic , and the outputs are de-fuzzified to control equipment. When a robust fuzzy design is reduced to a single, quick calculation, it begins to resemble a conventional feedback loop solution and it might appear that the fuzzy design was unnecessary. However, the fuzzy logic paradigm may provide scalability for large control systems where conventional methods become unwieldy or costly to derive. Fuzzy electronics
840-437: The temperature in the room (PV) goes below the user setting (SP), the heater is switched on. Another example is a pressure switch on an air compressor. When the pressure (PV) drops below the setpoint (SP) the compressor is powered. Refrigerators and vacuum pumps contain similar mechanisms. Simple on–off control systems like these can be cheap and effective. Fuzzy logic is an attempt to apply the easy design of logic controllers to
870-426: The term, others who followed him certainly did describe the method as black-box analysis. Vitold Belevitch puts the concept of black-boxes even earlier, attributing the explicit use of two-port networks as black boxes to Franz Breisig in 1921 and argues that 2-terminal components were implicitly treated as black-boxes before that. In cybernetics , a full treatment was given by Ross Ashby in 1956. A black box
900-404: Was described by Norbert Wiener in 1961 as an unknown system that was to be identified using the techniques of system identification . He saw the first step in self-organization as being to be able to copy the output behavior of a black box. Many other engineers, scientists and epistemologists, such as Mario Bunge , used and perfected the black box theory in the 1960s. In systems theory ,
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