U.S. patent application number 15/784438 was filed with the patent office on 2018-02-22 for method for diagnosing an electrical circuit.
This patent application is currently assigned to PLASTIC OMNIUM ADVANCED INNOVATION AND RESEARCH. The applicant listed for this patent is Arnd LANGENSTEIN, Francois-Regis LAVENIER, Mircea MATEICA, Gerd MEYERING. Invention is credited to Arnd LANGENSTEIN, Francois-Regis LAVENIER, Mircea MATEICA, Gerd MEYERING.
Application Number | 20180052197 15/784438 |
Document ID | / |
Family ID | 45723851 |
Filed Date | 2018-02-22 |
United States Patent
Application |
20180052197 |
Kind Code |
A1 |
LAVENIER; Francois-Regis ;
et al. |
February 22, 2018 |
METHOD FOR DIAGNOSING AN ELECTRICAL CIRCUIT
Abstract
A method for diagnosing an electrical circuit including at least
one electrical device, an actuator for the device controlled by a
high side actuating switch and a low side actuating switch, and at
least one additional switch not in series with any of the HS or LS
switch, the method including: to each of the possible statuses of
the circuit, giving a code; sequentially putting the circuit in at
least some of these statuses for a given time period; during each
of these periods, measuring voltage and/or current in different
parts of the circuit and giving a code to the measurement; and
establishing a diagnosis of correct functioning or of a
malfunctioning of at least some elements of the circuit according
to a pre-established correlation between the status codes and the
measurement codes.
Inventors: |
LAVENIER; Francois-Regis;
(Exincourt, FR) ; MATEICA; Mircea; (Timisoara,
RO) ; MEYERING; Gerd; (Haren, DE) ;
LANGENSTEIN; Arnd; (Essen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LAVENIER; Francois-Regis
MATEICA; Mircea
MEYERING; Gerd
LANGENSTEIN; Arnd |
Exincourt
Timisoara
Haren
Essen |
|
FR
RO
DE
DE |
|
|
Assignee: |
PLASTIC OMNIUM ADVANCED INNOVATION
AND RESEARCH
Brussels
BE
|
Family ID: |
45723851 |
Appl. No.: |
15/784438 |
Filed: |
October 16, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13819087 |
May 7, 2013 |
9823293 |
|
|
PCT/EP11/64493 |
Aug 23, 2011 |
|
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15784438 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 31/40 20130101;
G01R 31/2829 20130101; G01R 31/72 20200101; G01R 31/2836 20130101;
G01R 31/343 20130101 |
International
Class: |
G01R 31/28 20060101
G01R031/28; G01R 31/40 20060101 G01R031/40 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 2010 |
EP |
10 174 212.0 |
Dec 17, 2010 |
EP |
10 195 575.5 |
Claims
1. (canceled)
2. A method for diagnosing an electrical circuit including at least
one electrical device, an actuator for the device controlled by a
high side (HS) actuating switch and a low side (LS) actuating
switch, and at least one additional switch not being in series with
any of the HS actuating or LS actuating switch, the method
comprising: giving a status code to each of a plurality of possible
statuses of the circuit; sequentially putting the circuit in at
least some of the plurality of possible statuses for a given time
period; during each given time period measuring voltage and/or
current in different parts of the circuit and giving a measurement
code to the measurement; and establishing a diagnosis of correct
functioning or of a malfunctioning of at least some elements of the
circuit according to a pre-established correlation between the
status codes and the measurement codes; wherein both the HS
actuating switch and the LS actuating switch of the actuator
comprise an additional switch or diagnosis switch in parallel with
the actuating switch.
3. A method according to claim 2 comprising: defining a three digit
status code, each digit having three possible values.
4. A method according to claim 3 comprising: defining a six digit
measurement code; listing the different possible errors to be
detected; and establishing tables giving the measurement codes
associated with different status codes and the possible errors
associated therewith for each possible diagnosis condition.
Description
CROSS-REFERENCE OF PRIOR APPLICATIONS
[0001] This application is a Continuation application of U.S.
application Ser. No. 13/819,087, filed May 7, 2013, which is the
National Stage of PCT/EP11/064493, filed Aug. 23, 2011, and claims
priority under 35 U.S.C. 119 to European Application Nos. EP 10 174
212.0 filed Aug. 26, 2010 and EP 10 195 575.5 filed Dec. 17, 2010,
the entire contents of which of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present application relates to a method for diagnosing
an electrical circuit and in particular, an electrical circuit for
at least one component of an SCR system like a BLDC motor of a pump
intended for aqueous urea solutions, an injector, a line or a tank
heater for such a system.
Description of Related Art
[0003] Legislation on vehicle and heavy goods vehicle emissions
stipulates, amongst other things, a reduction in the release of
nitrogen oxides NO.sub.x into the atmosphere. One known way to
achieve this objective is to use the SCR (Selective Catalytic
Reduction) process which enables the reduction of nitrogen oxides
by injection of a reducing agent, generally ammonia, into the
exhaust line. This ammonia may derive from the pyrolytic
decomposition of an ammonia precursor solution, whose concentration
may be the eutectic concentration. Such an ammonia precursor is
generally a urea solution.
[0004] With the SCR process, the high levels of NO.sub.x produced
in the engine during combustion at optimized efficiency are treated
in a catalyst on exiting the engine. This treatment requires the
use of the reducing agent at a precise concentration and of extreme
quality. The solution is thus accurately metered and injected into
the exhaust gas stream where it is hydrolysed before converting the
nitrogen oxide (NO.sub.x) to nitrogen (N.sub.2) and water
(H.sub.2O).
[0005] In order to do this, it is necessary to equip the vehicles
with a tank containing an additive solution (generally an aqueous
urea solution) and also, with a pump for conveying this solution to
the exhaust pipe.
[0006] The OBD II requirements from CARB (California Air Resources
Board, which is responsible for the OBDII specification) request
explicitly that all components have to be diagnosed each power
cycle i.e. every time the engine is switched on and off (thus also
in cold conditions when the pump is not activated) and also,
periodically (for instance: every 30 minutes).
[0007] In order to do that, current and/or voltage measurements can
be used. However, since generally the components have (or are
connected to) a rather complicated electrical circuit comprising
different branches and devices, a single static measurement of the
voltage and/or current in the different branches or devices will
note enable to differentiate from one error to another.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention aims at solving that problem by
providing such a method i.e. a diagnostic method allowing to detect
which part of the circuit is malfunctioning. It is based on the
idea of putting switches in the circuit in order to be able to
sequentially activate and deactivate some branches thereof so as to
put said circuit in different statuses during each of which several
current/voltage measurements are performed. By correlating the
statuses and the measurements, it appears to be possible to
differentiate most (and sometimes even all) of the errors one from
another.
[0009] For this purpose, the present application relates to a
method for diagnosing an electrical circuit comprising at least one
electrical device and an actuator for said device controlled by a
high side (HS) switch and a low side (LS) switch (which actually
are the actuating switches of the device), according to which:
[0010] the system is provided with at least one additional switch
not being in series with any of the HS or LS switch: [0011] to each
of the possible statuses of the circuit, a code is given; [0012]
the circuit is sequentially put in at least some of these statuses
for a given time period; [0013] during each of these periods, the
voltage and/or the current is measured in different parts of the
circuit and a code is given to said measurement; [0014] a diagnosis
of correct functioning or of a malfunctioning of at least some
elements of the circuit is established according to a
pre-established correlation between the status codes and the
measurement codes.
[0015] The method of the invention applies to an electrical circuit
i.e. an electrical wiring system comprising at least one electrical
device (magnetic coil, heater, pump . . . ) which is actuated (put
ON or OFF i.e. through which current is circulated or not) thanks
to an actuator which is therefore connected respectively to a power
supply (like a battery in the case of a circuitry on board of a
vehicle, like one of an SCR system) through a high side (HS) switch
and to the ground through a low side (LS) switch. In some
embodiments, in order to save parts and money, at least 2 actuators
of 2 different devices may share the same LS switch.
[0016] According to the invention, each HS and LS switch can be in
at least 2 different statuses (activated when the switch is closed,
and inactivated when the switch is open) and the system comprises
at least one additional switch not in series with said HS and LS
switches in order to increase the number of statuses and
measurements in order to be able to maximize error detection and
recognition (differentiation). The number of different statuses of
the complete electrical circuit corresponds in fact to the number
of possible combinations of the statutes of each switch.
[0017] Generally, the method of the invention is implemented via at
least one PCB (Printed Circuit Board) comprising the above
mentioned switches. This or these PCBs are generally connected to a
controller that actuates the switches, records the measurement
signals, generates the status and measurement codes and performs
the diagnosis by correlating the status codes and the measurement
codes.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0018] The present invention will be described in more details with
reference to some embodiments supported by the Figures and Tables
attached to the present specification, the features of which are
not intended to limit the scope of the invention.
[0019] FIG. 1 shows a first electrical circuit to which a method
according to a first embodiment of the invention can be
applied.
[0020] FIG. 2 shows Table 1,
[0021] FIG. 3 shows Table 2, tables 1 and 2 show the measurement
steps of said method and how a code is generated accordingly.
[0022] FIGS. 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7 show Tables 3.1,
3.2, 3.3, 3.4, 3.5, 3.6, 3.7 which show how a status code is
associated to the different measurement steps.
[0023] FIG. 5 shows Table 4, which shows the types of errors that
can be detected in the method of that embodiment.
[0024] FIG. 6 shows Table 5, which shows the possible measurement
codes associated with each status code and the possible errors
associated therewith.
[0025] FIG. 7 shows a repetitive activation sequence that can be
used in practice.
[0026] FIGS. 8.1 and 8.2 show the logic diagrams leading to the
detection and identification of the errors.
[0027] FIG. 9 show Table 6, which is a summary of said errors and
codes associated therewith.
[0028] FIG. 10 shows a second electrical circuit to which a method
according to a second embodiment of the invention can be
applied.
[0029] FIG. 11 shows Table 7,
[0030] FIG. 12 shows Table 8, tables 7 and 8 show the measurement
steps of said method and how a code is generated accordingly.
[0031] FIGS. 13.1, 13.2, 13.3, 13.4 show Tables 9.1, 9.2, 9,3, 9.4,
which show how a status code is associated to the different
measurement steps.
[0032] FIG. 14 shows Table 10, which shows the types of errors that
can be detected in the method of that embodiment.
[0033] FIG. 15.1, 15.2, 15.3, 15.4, 15.5, 15.6, 15.7, 15.8, 15.9,
15.10 shows Tables 11.1, 11.2, 11.3, 11.4, 11.5, 11.6., 11.7, 11.8,
11.9, 11.10 which show the possible measurement codes associated
with each status code and the possible errors associated
therewith.
[0034] FIGS. 16 to 30 show the logic diagram leading to the
detection and identification of the errors.
[0035] FIG. 31 shows a third electrical circuit to which a method
according to a third embodiment of the invention can be
applied.
[0036] FIG. 32 shows Table 12,
[0037] FIG. 33 shows Table 13, tables 12 and 13 show the
measurement steps of said method and how a code is generated
accordingly.
[0038] FIGS. 34.1, 34.2, 34.3 show Tables 14.1, 14.2, 14.3, which
show how a status code is associated to the different measurement
steps.
[0039] FIG. 35 shows Table 15, which shows the types of errors that
can be detected in the method of that embodiment.
[0040] FIG. 36 shows Table 16, which shows the possible measurement
codes associated with each status code and the possible errors
associated therewith.
[0041] FIGS. 37 and 38 show the logic diagram leading to the
detection and identification of the errors.
DETAILED DESCRIPTION OF THE INVENTION
[0042] As explained above, the method of the invention can be
applied to (parts of) electrical circuits of systems that must be
diagnosed periodically like SCR systems on board of vehicles.
[0043] A device to which the method of the invention can be
applied, is for instance the motor of a pump, for instance a pump
which supplies reducing agent (urea/water solution generally) in
exhaust gases of an engine, preferably onboard of a vehicle.
[0044] One type of pump that is very efficient is composed of a
rotary pump driven by a brushless direct current (BLDC) motor. In
such a motor, the rotor is rotated by the sequential switching
(activating according to a defined timing) of electromagnetic coils
placed in the stator. Each of these coils is generally connected to
a power supply and to the ground.
[0045] The main errors that can happen on such a motor are the
following: [0046] shortcut of one phase to power supply [0047]
shortcut of one phase to ground [0048] one phase disconnected.
[0049] In order to diagnose this motor, i.e. to check its correct
functioning, some algorithms and methods using them have been
provided, which are relatively easy to implement while the pump is
running (rotating). However, recently, some car manufacturers have
emitted the requirement to be able to diagnose said pump also when
it is not rotating. Also, a requirement has come up as to detecting
the nature of the error.
[0050] Hence, according to a first embodiment, the present
application relates to a method for diagnosing a motor comprising
at least 3 electrical phases (A, B, C) connected in star, according
to which: [0051] each phase is sequentially activated (connected to
a power supply), then grounded, while the others remain
inactivated; [0052] to each activation and grounding step, a status
code is given; [0053] during each activation and grounding step,
the voltage is measured in each of the phases and a code is given
to said measurement; [0054] a diagnosis of correct functioning or
of malfunctioning of each of the phases of the motor is established
according to a correlation table between the status codes and the
measurement codes.
[0055] The motor to which this embodiment of the invention applies
is preferably a BLDC motor comprising at least one magnetic coil in
each phase and which is generally controlled by a controller. This
motor may be an internal or external rotor motor. Preferably, it is
an internal rotor motor. Preferably, and each phase comprises at
least one magnetic coil.
[0056] The stator of this motor comprises at least 3 coils in order
to have at least 3 phases which may be assembled in star or
triangle configuration. This stator therefore comprises, in
general, a multiple of 3 coils, generally 3, 6 or 9. Good results
have been obtained with a motor having an internal rotor and a
stator comprising 9 coils positioned uniformly around the rotor,
and being connected so as to form 3 phases (i.e. each phase (A, B
or C) comprising 3 coils, and said coils being uniformly positioned
around the rotor in the order A, B, C, A, B, C, A, B, C).
[0057] The method of this embodiment of the invention gives good
results with motors having 3 phases (A, B, C) connected in
star.
[0058] The motor to which it applies is preferably designed in
order to be able to operate a pump and preferably, a pump able to
rotate in two opposite rotational directions, one generally
corresponding to supplying a feed line with liquid and the other
generally corresponding to a purge of the feed line (and of the
accessories found therein). In practice, this may be easily
achieved by reversing the activation sequence of the coils
(phases).
[0059] Preferably, the rotary pump is of the gear pump type. These
pumps actually have the advantage of providing identical pumping
efficiency in both directions of rotation.
[0060] The controller of this pump is a control module (generally
comprising a PID (proportional-integral-derivative) regulator and a
motor rotational speed controller) and an electric power supply
unit which preferably supplies the motor with the power required to
rotate it at the desired speed and which enables its direction of
rotation to be reversed, where necessary.
[0061] Most particularly preferably, an ECM (Electronic Control
Module) sends to the pump controller, a CAN (Controller Area
Network) message or a PWM (Pulse Width Modulation) control signal
having a duty cycle that varies as a function of the desired
operating conditions for the pump and the controller then acts on
the motor to apply said operating conditions to the pump. Such a
system is the subject of Application FR 0700358 in the name of the
Applicant, the subject of which is incorporated by reference in the
present application.
[0062] The pump controller interprets this CAN message or PWM-type
signal and, depending on the CAN information or on the duty cycle,
stops the pump or switches the phases (the coils) in order to
regulate the pressure requested or in order to purge the system or
in order to heat the pump.
[0063] The motor to which the method according to this embodiment
of the invention applies is preferably intended to a pump for
pumping (transporting) a liquid in freezing conditions, that is to
say when the temperature reaches a low temperature threshold and
when the liquid is capable of freezing or solidifying. These may,
for example, be aqueous solutions. One liquid to which the present
invention applies particularly well is urea.
[0064] The term "urea" is understood to mean any, generally
aqueous, solution containing urea. The invention gives good results
with eutectic water/urea solutions for which there is a quality
standard: for example, according to the standard DIN 70070, in the
case of the AdBlue.RTM. solution (commercial solution of urea), the
urea content is between 31.8% and 33.2% (by weight) (i.e. 32.5
+/-0.7 wt %) hence an available amount of ammonia between 18.0% and
18.8%. The invention may also be applied to the urea/ammonium
formate mixtures, also in aqueous solution, sold under the trade
name Denoxium.TM. and of which one of the compositions
(Denoxium-30) contains an equivalent amount of ammonia to that of
the AdBlue.RTM. solution. The latter have the advantage of only
freezing from -30.degree. C. onwards (as opposed to -11.degree.
C.), but have the disadvantages of corrosion problems linked to the
possible release of formic acid and a less available market
(whereas urea is widely used and readily available even in fields
such as agriculture). The present invention is particularly
advantageous in the context of eutectic water/urea solutions.
[0065] Preferably, the motor to which the method of this embodiment
of the invention applies has a preheating mode during which current
is passed through at least one coil (preferably, through all of
them) but in a way such that the rotor doesn't rotate. On the
contrary, during the operation of the pump, current passes through
the coils according to a sequence such that the electromagnetic
force or forces generated have a tangential component so as to
create a permanent rotational torque. In the case of a motor having
3 coils, it is sufficient, for example, to activate each coil in
turn, in a given direction (clockwise or anti-clockwise), while
deactivating the other 2, to generate such a torque. In the case of
a pump with 9 coils and 3 phases as described above, each phase can
be activated in turn for instance.
[0066] In order not to generate a permanent torque while getting a
heating effect, it is possible, during each heating cycle, to
activate the coils (phases) according to a given sequence (time
scheme) not generating any torque, or randomly.
[0067] Alternatively, during each heating cycle, some of the coils
(phases) may be powered constantly, while some others are not. This
embodiment is preferred because in the former one, at each switch
(change of coils which are activated), a punctual torque is
generated, which can lead to mechanical tensions if the pump is
actually blocked with frozen liquid. In an even more preferred
embodiment, the coils which are permanently powered during each
heating cycle are memorized by the controller and in the next
heating cycle, at least some of them are put at rest while others
(at rest in the first heating cycle) are activated. This embodiment
has the advantage of being simpler and of not ageing too much
specific coils i.e. of spreading the wear owed to the heating
process on all the coils. For example, in the above described pump
with 9 coils and 3 phases, the following heating cycles may be
repeated (in terms of phases activated continuously during a given
cycle): A & B, A & C, B & C. Alternatively, the
controller may randomly choose 2 phases to power in each heating
cycle.
[0068] It results from the above that the method of this embodiment
of the invention can also be applied while the pump is
preheating.
[0069] The method according to this embodiment of the invention
will be described more in detail below for the specific case
(example) of a 3 phase BLDC motor, the electric circuitry of which
is depicted in FIG. 1 attached. This example is purely illustrative
and none of the specific features thereof (number of phases, codes
used, specific algorithms . . . ) should be seen as limiting the
scope of the invention.
[0070] The hardware associated with that circuitry provides the
following possibilities: [0071] one high side driver for each
phase, which allows to perform the activation steps [0072] one low
side driver for each phase, which allows to perform the grounding
steps [0073] one current measurement plus over current
detection/protection. Hence, that circuitry comprises 3 actuators
(one for each phase of the motor) having each their HS and LS
switch.
[0074] The sequence of steps applied while the pump is not
rotating, satisfies the following needs: [0075] all phases need to
be activated to allow shortcut to ground/open load detection [0076]
no command or low side activation is needed to detect shortcut to
power supply.
[0077] This sequence hence comprises the following steps:
[0078] Step 1--High side phase A active
[0079] Step 2--None of the phases are active (all sides of all
phases are inactive).
Alternatively phase A low side may be active i.e. phase A may be
grounded.
[0080] Step 3--High side phase B active
[0081] Step 4--None of the phases are active (all sides of all
phases are inactive).
Alternatively phase B low side may be active i.e. phase B may be
grounded.
[0082] Step 5--High side phase C active
[0083] Step 6--None of the phases are active (all sides of all
phases are inactive).
Alternatively phase C low side may be active i.e. phase C may be
grounded.
[0084] Grounding one phase may allow reaching quicker 0V (i.e. to
unload the phases in between two activation steps) but implies a
risk of over current in case of shortcut to battery.
[0085] Using this sequence, the pump will not turn and no
activation is visible from the outside. The initial phase where all
the preliminary checks (e.g power supply) are done is not described
in this sequence, but is applied in practice.
[0086] During each of the above mentioned steps, the voltage is
measured in each of the phases and a code is generated according
Tables 1 and 2 attached. As can be seen from these Tables, after a
given phase has been activated or grounded, the voltage is measured
in the commanded phase and in the 2 other ones and to each of the 3
measurements, a one digit code is given so that for each of the
above mentioned steps, a measurement code with 3 digits is
generated. In our example, this one digit code is 0 if the measured
voltage U is below a given minimum (0.1V in our example), 1 if it
is above a given value (9V in our example) and 2 if there is an
over current detection. The values of 0.1 and 9V are calibration
parameters which must be adapted to the OEM specifications.
[0087] Besides, to each step of the sequence, a status code is
associated as set forth in Tables 3.1 to 3.7. This code is a 6
digit code indicating which side (low or high) of which phase has
been activated. More precisely: all 6 digits are equal to 0 in step
0, one of them is equal to 1 in step 1, while the others are equal
to 0; and the same for each step, the digit being equal to 1 (while
the others are equal to 0) being different for each step.
[0088] The errors defined in Table 4 can be detected as follows:
[0089] shortcuts to power supply will be detected when none of the
BLDC motor phases are commanded and a certain voltage is measured
on any of the phases. Alternatively the low sides could be used to
avoid timing problems (pull-downs should bring the actual voltage
to 0 faster than no command); [0090] shortcuts to ground are
detected when 1 phase is commanded (high side active) and we have
an over current shutdown OR the commanded phase voltage remains at
a very low voltage. When a phase is shorted to ground, the measured
value will remain to 0 when we try to activate it. Additionally the
over current protection will get activated (timing of the over
current protection is depending on the actual circuit) [0091] open
circuits are detected when one phase is commanded (high side
active) and no voltage is measured on the other phases.
Additionally, when another phase than the not connected one is
commanded, the not connected phase will show 0V. When a phase is
not connected, the measured value will switch to VBAT value when we
try to activate it. But since the phase is disconnected, the VBAT
will not "go" to the other phases
[0092] Table 5 shows the possible measurement codes associated with
each status code and the possible errors associated therewith. In
this Table, x stands for 0 or 1.
[0093] To perform the motor diagnosis every 300 ms, the repetitive
activation sequence showed in FIG. 7 can be used, in which each
phase is activated sequentially for 50 ms.
[0094] For each individual state, the logic diagram of FIG. 3 is
used, leading to the detection and identification of the errors set
forth above according to the correlation of Table 5 and the
explanations above, summarized (and translated into codes) in Table
6 (noting that in this table, 2xx is taken instead as 200 like in
Table 5, just for adding an additional safety margin). As can be
seen in this Table, correct functioning is diagnosed when all
phases are inactive when not activated, and when they are all
active when one is active. In all other cases, there is a
malfunctioning the nature of which (short circuit to power or
ground, or open circuit) can be detected based on the association
between status code and measurement code. This method can be
generalized to any motor with a star connection of 3 phases.
[0095] According to a second embodiment, the method of the
invention may be applied to 2 actuators of 2 separate devices which
share a common LS switch (which is interesting from an economical
point of view but which renders diagnosis more difficult). In this
embodiment, each HS and LS comprises an additional switch (also
called diagnosis switch) which is in parallel with the actuating
switch.
[0096] These devices may be 2 different functional parts of an SCR
system, like for instance to 2 different heaters, to a heater and a
pump . . .
[0097] The method according to this embodiment of the invention
will be described more in detail below for the specific case
(example) of an electrical circuit comprising a line heater (for
instance: the heater used to heat up the urea feed line) and a
transfer pump (pump used to transfer pump from a passive, storage
reservoir to an active, heated one), and which is depicted in FIG.
10 attached. Again, this example is purely illustrative and none of
the specific features thereof (codes used, specific algorithms . .
. ) should be seen as limiting the scope of the invention.
[0098] As for the first embodiment, the method requires, in order
to be implemented, the following preliminary steps: [0099] defining
a measurement code but this time, according to Tables 7 and 8
attached, the measurement code is a 6 digit code (instead of a 3
digit code); [0100] defining a status code according to Tables 9.1
to 9.4, which this time is a 3 digit code, each digit having 3
possible values (0, 1 or R) [0101] listing the different possible
errors to be detected, as in Table 10 attached [0102] establishing
so called "True tables" giving the measurement codes associated
with different status codes and the possible errors associated
therewith for each possible diagnosis condition (while both line
heater and transfer pump are inactivated (=OFF DETECTION); when
only one of them is activated (=line heater ON DETECTION or
transfer pump ON DETECTION) or when both are activated (transfer
pump & line heater ON DETECTION)).
[0103] To implement the method according to this embodiment of the
invention, the circuit is successively put in different statuses,
the sequence of which depends on the condition in which the system
is (OFF, line heater or transfer pump ON, both ON). These sequences
are listed in the logic diagrams of FIGS. 16 to 30 attached, which
also illustrate how different errors can be detected and
differentiated one from another.
[0104] A third embodiment of the present invention may be applied
to the actuator of a single device having an actuating switch. In
this embodiment also, both the HS and the LS of the actuator
comprises an additional switch (also called diagnosis switch) which
is in parallel with the actuating switch.
[0105] This embodiment is illustrated in the case of an SCR tank
heater by FIGS. 31 to 38 and Tables 12 to 16 attached: [0106] FIG.
31 showing the concerned electrical circuit [0107] tables 12 and
13, the measurement steps and code generation [0108] Tables 14.1 to
14.3, the status code association [0109] Table 15, the types of
errors that can be detected [0110] Table 16, the association
between measurement codes and status codes and the possible errors
associated therewith [0111] FIGS. 37 and 38, the logic diagram
leading to the detection and identification of errors.
* * * * *