ROCTSA (simulation module) and the similarity
calculator (learning module).
Note: we chose the duration of a temporal constraint
of period type (d) is 5ms.
During the simulation module, the set of normal
and abnormal CTS are recorded in the CTS base to
form the learning base. Figure 5 shows various
examples of CTS instances with the different
attributes of the learning base. It describes 10
instances labeled as normal behaviors of the turntable
and 7 instances labeled by the various failures as
previously described.
Instance 5 of the learning base is a normal CTS which
corresponds to this rule:
(In, ↑S4, nct)* (↑S4, ↓c4, [80, 85])* (↓c4, ↑c5,
[2816, 2821])* (↑c5, ↓S4, [6912, 6917])* (↓S4, ↓c5,
[80, 85])* (↓c5, ↑c4, [2816, 2821]) -> N
This signature describes the passage through the
different states of path A (introduced above). It
implies that if the rising edge of the S4 actuator (↑S4)
occurs followed by the occurrence of the falling edge
of sensor c4 (↓c4) satisfying the time constraint [80,
85] with respect to ↑S4, the occurrence of the rising
edge of the sensor c5 (↑c5) satisfying the constraint
[2816, 2821] with respect to ↓c4, the occurrence of
the falling edge of the S4 actuator (↓S4) satisfying the
constraint [6912, 6917] with respect to ↑c5 of the
falling edge of the sensor (↓c5) satisfying the
constraint [80, 85] with respect to ↓S4 and the rising
edge of sensor c4 (↑c4) satisfying the constraint
[2816, 2821] with respect to ↓c5, then we
the normal behavior of the system.
Instance 11 of the learning base is an abnormal
CTS which corresponds to this rule:
(In, ↑S4, nct)*(↑S4, ↑c5, [2896, 2901])-> F2
It implies that if the rising edge of the S4 actuator
(↑S4) occurs followed by the occurrence of the rising
edge of sensor c5 (↑c5) satisfying the time constraint
[2896, 2901], then we can deduce the faulty behavior
F2. The learning module uses these past experiences
to add new CTS to the CTS base (to promote
learning).
Example: We propose to add an nCTS and search the
most similar using our similarity calculator.
ROCTSA starts generating an nCTS:
nCTS: (↑c4, ↑S4, [65664,65669])* (↑S4, ↓c4, [80,
85])-> ?
It does not exist in the CTS base. Consequently,
the similarity calculator can be launched. The nCTS
inherits the (normal or faulty) behavior of the CTS
which has the minimum distance and will be stored in
the CTS Base. In this example, CTS 6 has the
minimum distance (D=0.166). Therefore, the nCTS
inherits the normal behavior of CTS 6 and is stored in
the CTS Base
.
6 CONCLUSIONS
In the context of diagnoses, we suggest a new
approach based on past experiences which couples a
simulation with learning for automatic acquisition
and update of a set of CTS. We present ROCTSA
algorithm allowing to model the normal behavior of
the system to diagnose as a set of normal CTS and the
faulty behavior as a set of abnormal CTS. A learning
module is introduced to learn new CTS and to update
the CTS base. The proposed approach has many
advantages: (i) An easy update for the CTS Base.
Indeed, when a new behavior occurs in the APS, a
new CTS will be added to the CTS base that models
this new behavior. (ii) It is a generic approach that can
be applied to any APS. (iii) It does not require the
presence of an expert who might be reluctant to
acquire a CTS base. As a prospect, to improve the
expressiveness of ROCRSA, we will express the
absence of events (negation operators). Then, we will
use this work to introduce a distributed approach for
complex system diagnoses. It will be based on a
multi-agent architecture which decomposes the
system to be diagnosed into subsystems. Each
subsystem will be supervised through an agent which
is responsible for the acquisition of its CTS Base and
its local diagnosis.
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