Data processing: artificial intelligence – Knowledge processing system – Knowledge representation and reasoning technique
Patent
1997-09-26
2000-04-04
Hafiz, Tariq R.
Data processing: artificial intelligence
Knowledge processing system
Knowledge representation and reasoning technique
706 51, 706 52, G06F 1700
Patent
active
060472782
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The efficient development of reliable software for reactive systems, which controllers of all types are, is nowadays a primary aim. FIG. 1 shows a schematic layout of a system comprising a controller and a process to be controlled. The controller must be designed in such a way that the process assumes only admissible states. The controller is fed input values, for example sensor values, at the inputs, these values being referred to as input states below. At the outputs, the controller outputs output values, referred to below as output states, which influence the process in such a way that it can assume only the admissible states.
During the programming of such memory-programmable controllers (programmable logic controllers), the following prescriptions must be observed in each case: to say what is effected by each individual output state of the controller, and how the sensor values which are supplied to the controller are to be interpreted. sequences. combinations of states or specific geometric configurations are to be avoided, specific actuators must only be activated if associated prior conditions (interlocks) are satisfied, etc.
These prescription are in each case available in a different, mostly informal, form. The technical problem is then to program a controller in such a way that it corresponds to the prescriptions.
By contrast with control engineering tasks, in which the theory knows about specific (standard) control algorithms, depending on process models, discrete control tasks have to be newly programmed in each case.
The programming of memory-programmable controllers is nowadays carried out in the manner in which the programmer defines the logical combinations according to which the output states are determined from the input states and the program states.
In order to program sequences there exist appropriate constructs of programming languages, in order to describe so-called step chains and parallel sequences. In each case, however, it is up to the programmer to ensure compliance with the function and the safety conditions. In other words, the relationship between the program and the abovementioned prescriptions is not documented explicitly.
One problem in the case of this procedure is the susceptibility to error, for even in the case of medium-sized systems the multiplicity of the possible system states is virtually incomprehensibly large; this means that cases are almost always overlooked, and programs have to be rewritten, with considerable effort, during the commissioning.
Even more serious is the problem that each rewrite, be it because of an error, because of changed environmental conditions or because of new requirements, impacts on the entire software--that is to say there is no mechanism which keeps the effects of a change local or else marks only those points impacted by a change.
SUMMARY OF THE INVENTION
The invention is based on the object of generating a controller from an application-related specification of a control task.
In general terms the present invention is a method for the automatic generation of a control algorithm, for a controller of a process. A non-deterministic automaton, which describes all the physically possible modes of behavior of the controller, is defined. The permitted state transitions of the process to be influenced by the controller are described. The automaton is set such that it satisfies prescribed safety conditions. In order to set the safety conditions, the largest subset that can be stabilized of the state set that is specified to be admissible is determined iteratively. The transfer function of the automaton is set such that in each case only those consequential states are selected which lie within this largest set that can be stabilized. The automaton is set such that it satisfies the function of the system comprising controller and process.
Advantageous developments of the present invention are as follows.
In order to comply with the safety conditions for the system comprising controller and process, the followin
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Hafiz Tariq R.
Khatri Anil
Siemens Aktiengesellschaft
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