7.3.1. On-line systems

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 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.

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:

• Basic measured size
  These values were obtained directly from sensors located to monitor the process in a some environment.
• Derived measured size
  These are the values that arise working or combining one or more direct values obtained from the sensor. It is a kind of synthesized values.
• Parameters
  A set of basic and derived measurement files that fully describes the process.
• Measurement
  Involves measuring the size of an elementary or displayed to the user. Can directly measure the size of a process (temperature, pressure, speed ...). The speed with which the measured data is not decisive, but accuracy, which can be increased with the help of computers (correction, eliminating the effect of the environment, etc.). Measuring the electrical work with the open loop, and perform ga mostly uniprocessor computer systems.
• Regulation
  Process of setting up one size to the desired value. There must be a closed loop. Measured value is analyzed through feedback in a closed loop, analyze the actual and desired values, and using the device corrects executive real value and seeks to achieve the smallest possible difference between them. Of course, the computer is part of a system of regulation.
• Monitoring
  It refers to the simultaneous measurement and display of a large number of different process parameters and their interactions. Computer system does not make decisions about intervention on the process but gives good quality and quick information about his condition. Therefore, it is an open loop as to the difference in measurements to monitor and many derived quantities obtained from several measured values.
• Conducting
  Higher step when monitoring on the basis of the data obtained occasionally intervene in the process. Automatic actions are not represented, and if they are, they are of minor importance.
• Management
  Principles as those conducting but is made almost completely automatic impact on the process. It is mainly used in less complex processes for which it is possible to make the appropriate algorithms and entered into the computer as a kind of program support. While the probability of unforeseen and therefore the situation is uninvolved process states must be meaningless.

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.