7.3.1. On-line systems

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The main reason for using an on-line system is the speed and high processing capabilities, which has a digital computer. This includes which data is transferred to the computer, it processed and out of the hand actuator. During the entire cycle is usually under a millisecond. So monitoring a system where the processes are changing rapidly it is almost impossible without the use of a digital computer. In addition to real-time can be monitored and predicted tendencies that may arise in the process. In this way it is easy to intervene and avoid alarming situation. Unlike the above code off-line processing that lasted till the results would be almost useless.

The quality of interventions in the system will depend on the quality of the algorithm have been developed to manage the process, and then entered into the form of software in the computer. In very complex systems it may happen that these programs are not covered everything possible situations occurring in the life and work can occur. You can not anticipate everything. For this reason sometimes the on-line system to avoid a state of the process is displayed only person who decides what to do. But it may happen that the manager made inappropriate conclusion despite the quality information that depict him. To avoid this increasingly introducing EXPERT systems, i.e. digital computers with software support that uses the knowledge base, conceived by a team of top experts in the process which is to be monitored. Such a system, which may or may not be on-line facilitator to help in critical situations make the best decision.

Thus, some relationships can not be monitored without the on-line monitoring system with digital computer, because no other tool does not have the speed and power of a computer that can change the fast emerging in the process of responding immediately.

Elements of intelligent behavior are very important feature of these systems. Under these thoughts on adaptability and managing systems (computers) in the changed situation in relation to the program known and defined, and this means that the system must recognize the change outside of the defined framework, adapt and adopt a more or less adequate solution to the system behaved within defined borders. So in such situations is not required, but the ideal solution first acceptable.


Example II

On-line system for monitoring traffic on the road crossing with sensors and digital computers.

 Traffic management
Figure 7.3.3 Traffic management of vehicles.  

On a busy intersection will be installed in the roadway or the road sensors, capacitive, electromagnetic or mechanical type, or a combination thereof may be necessary to register the passage of vehicles. Passage of vehicles in this example is a process, and the measured mean the intersection. Vehicle traffic at the intersection with the sensors 'monitor' digital computer. Executive devices that are computer controlled traffic lights. The main task of the efficient management of traffic through the intersection. Whether the sensors are placed closer to the intersection, or there will be more along the road depends on the structure of the system and the type of intersection (the center of the city, a suburb of ...), and the method of regulating traffic on the algorithm computer program support.

The computer will accept all data on the speed of the vehicle to let's say 60 km/hour. All values beyond that point to the anomaly and the computer to repeat the measurement. If you do not get acceptable data computer must repeat measurement (some fool vehicles has 100 km/hour), but if the result is again necessary to run a diagnostic program to establish the functionality of the system and if the system is malfunctioning excluded from the function to set all signals to the 'yellow' and sends it to the master level notice 'of a defect'. If we add the various traffic conditions during the working day, holidays and the like can be seen that the complexity of the algorithm should be developed.

Apart from the above computer needs to determine whether it is indeed on the lights according to the order (again, some sensors in the traffic light). In case of failure again runs a diagnostic program. All this is done in a very short time intervals, which are almost meaningless to the weather changes traffic. The essence of the functioning of the system is that throughput in certain directions at the intersection of regulating the flow of vehicles in certain directions and to failure to give priority to the direction in which current flow is greatest. What if there is no vehicle (night)? Simply, they can light up in red light at the traffic lights and the status is changed by the first vehicle that comes along from any direction.

Therefore, the system monitors the flow of traffic, analyze changes and adapts to the new situation in the best possible way. In this consists its 'intelligence'. In this example, no mention is yet another important feature-reliability. In critical processes, space flight, one management system is not sufficient regard to reliability. Then there are two or more identical systems one of which is active and others are working in the background and mimic control, but their results are compared wrapped it with an active system. If it is found that the currently active system makes a mistake in relation to back-up system (due to some malfunction), one automatically takes over management of the reserve and by then the active system is turned off.


Terminology

Dates are in IT area specifically because it has not yet developed an unambiguous terminology. But few terms should be defined although in the literature and find a different name from above for the same thing. Notwithstanding the above we have:

When the code of the process must not be allowed to come to a complete interruption, you should provide the ability to manually control the process until the on-line process does not qualify. Of course it is a case where there is no reserve of the guide system or when they are unable to take control. Yellow blinking light that will be in the transport system manually from the traffic light to traffic light is one of the most primitive examples of solving such problems.

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