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suciently realistic cooling curve, the effects of which can be discerned in figure
5. The current applied to the motor is controlled by a high-level control system,
which in the simulation is a simple fixed sequence of instructions. The purpose
of the simulation is to demonstrate the action of the innate immune system
components, and thus the implementation of a neuro-endocrine controller was
not deemed necessary.
It is important to note that decisions are taken by the TLRs without the in-
tervention of the high level control system, and they have to be considered as the
first response of the immune system. The high level control system might then be
influenced to change its behaviour depending on the inflammation present in the
system through a scheme such as the neuro-endocrine controller outlined above
(see section 3.4). In this model a more simplistic high-level control mechanism
is used, but importantly it
is
affected by the inflammation level and modifies
the requested current taking this inflammation level into account. This is a very
simplistic remediation mechanism.
5Rsus
Figure 4 shows how increasing current causes an increase in inflammation. The
oscillations in the inflammation are due to the action of the TLRs switching the
cooling fans and the motors themselves on and off. The effect of the inflammation
is also to reduce the currents requested by the high level control system using a
simple inversely proportional relationship (see Figure 6). The high-level control
system is at the same time always attempting to return the motor currents to
the requested levels.
Figure 5 shows the temperature of one motor over a period of time varying with
the current. For a current of 0
.
1, after reaching the limit temperature of 40 (this
value was fixed arbitrarily) a response is performed by the TLR which causes the
fan to switch on. This operation causes the temperature of the motor to decrease.
However the high level control system is trying to return current to the requested
level. Considering a current of 0
.
1 the fan is always able to control the temperature.
This pattern can also be seen when the current is 0
.
2. A different case occurs when
the current is 0
.
5, this means that the high level control system is driving the motor
at a high rate in order to fulfill its aim. This causes the TLR to activate the fan and
frequently switch off the motor to prevent damage.
Figure 6 shows the effects of varying current over time in different motors
and the resultant inflammation level. In this experiment motor1 simulates the
occurrence of a fault, resulting in excessive current at time step 500. This causes
the inflammation level to rise in steps as the requested current increases at time
steps 1000 and 1500. The dramatic increase in inflammation at time step 2000 is
due to the failure of the fan to cool motor1 and subsequent coincidental failure
of motor2 and motor3. This inflammation comes from the activity of TLRs 2
and 3 as they activate the other fan and switch off the motors when required. At
time step 2500 the faults are removed from the motors and the system returns
to normal operation. This type of over-current condition can result from sticky
