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Case Study Details
B.4 Full List of Examined Fault Scenarios
Legend
Fz1 : Gravity on the left lever.
d1 : Arm of the left lever.
t1 : Torque exerted by Fz1 * d1.
Fz2 : Gravity on the right lever.
d2 : Arm of the right lever.
t2 : Torque exerted by Fz2 * d2.
Fm : Force caused by the motor.
dm : Arm of the motor.
tm : Torque exerted by the motor (Fm * dm).
Figure B.2: Forces and torques on the frontal stand.
Gravity exerts torques on both the left (torque t1) and right (torque t2) lever of the frontal stand
(Stand). These two torques should be complemented with a third torque exerted by the motor in
order to control the angular acceleration of the stand. This acceleration is used by the speed controller
CTR_speed to enable the controlling of the speed. This controller uses a table to determine
what current it has to set (Iset) in order to achieve a certain acceleration at a particular position 1 .
So, the difference between the speed setpoint (Vset) and the actual speed (Vact) results in a certain
desired acceleration (e_sp). This acceleration is combined with the current position (Pact) in order
to lookup the associated current setpoint Iset. Here starts the third and final control loop. It is responsible
for controlling the current at setpoint Iset. In order to do so it requests a certain current
of the MVR(forward) 2 that has a circuit with the Motor/Brake. The actual current (Iact) on this
circuit is measured by means of a ampere meter and led back to the current controller CTR_current.
Because the current is flowing on this circuit the motor exerts a torque (Tm). The torque resultant
makes that the stand will rotate at a certain speed to a certain position. The speed can be measured
by the MVR(feedback). And by leading the signal Vact_analog back to the controller (Vact) the
speed control loop has been closed. The closing of the outer position loop is done by measuring the
real position. For this purpose a potentiometer and encoder (Potmeter/Encoder) have been
assembled upon the rotating axle. When rotated, these components output a voltage. The signals of
the potentiometer and encoder are combined in order to achieve a certain accuracy (and to do error
detection). The LUC_extension(feedback) contains a AD-converter to digitize the analog signal
and lead it back to the controller (LUC_extension(controller)). The position controller will use
this value (Pact) once again to calculate the (nominal) position error.
B.4 Full List of Examined Fault Scenarios
Table B.2 shows the fault scenarios that are considered in the work for this thesis:
S1-S11: presented in the thesis, table 5.4 and table 5.6.
1 Note that when the Stand rotates the arms of the left and right gravitational torques change. In order to keep the
speed constant the torque that the motor has to generate has to change likewise.
2 Note that both occurrences of MVR denote the same FRU. It is only a logical decomposition. The same holds for
the LUC Extension FRU.
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