EP1327761B1 - Process for verifying the operation of two sensors - Google Patents

Description

State of the art

The invention relates to a method for checking the operability of a first and a second encoder, with which independently the angular position of a wave can be determined or with which independently the angular positions of two waves can be determined, the rotational movements are linked together.

• eine sichere und einfache Starterkennung,
• das sichere Erkennen eines Abwürgens des Motors sowie einer Unterdrehzahl,
• eine Drehrichtungserkennung,
• eine schnelle Synchronisation beim Schnellstart,
• die Realisierung eines relativ guten Drehzahlgeber-Notlaufs
• einen Direktstart.

Such a method can be used, for example, in conjunction with internal combustion engines to verify the operability of a speed sensor and an absolute angle encoder, with which the angular position of the motor can be continuously detected. The measuring signals of the speed sensor and the absolute angle encoder are fed to the motor control, where they are evaluated. The information gained in this way makes it possible

• a safe and easy start detection,
• the safe detection of stalling of the engine and an underspeed,
• a sense of rotation,
• a fast synchronization during the quick start,
• the realization of a relatively good speed sensor emergency operation
• a direct start.

By appropriate control and control measures, the operation of the internal combustion engine can then be improved overall. The extensive functionality of modern engine control systems also affects the design of individual engine components. For example, the battery, the starter and the alternator are made smaller, if faster synchronization can be achieved during the quick start. By detecting the direction of rotation, intake manifold couplers can be avoided, so that the intake manifold and the throttle valve must meet correspondingly lower requirements.

To detect the speed is often used in practice a sender wheel with sixty minus two (60 - 2) angle marks in the form of teeth. The sender wheel is firmly connected to the crankshaft and rotates with it. The angle marks are scanned with the help of a sensor, which usually works inductive, magnetoresistive or by utilizing the Hall effect. The current angular position can be determined with the aid of an absolute angle encoder on the camshaft or on the crankshaft. Such an absolute angle encoder is for example in the German Offenlegungsschrift 197 22 016 described.

As already mentioned, a number of functions of the engine control based on a continuous and above all reliable detection of the engine speed and the current angle of rotation. In order to ensure that this information is actually available, the functionality of the corresponding donor must be verifiable.

The GB-A-2 293 897 shows two speed sensors (speed sensors 31 and 33), by means of the speed of the speed of the crankshaft and the rotational speed of an injection pump is detected. When the ratio of the speeds falls outside a predetermined range, an error is detected.

Advantages of the invention

With the present invention, a method of the type mentioned is proposed, with which the functionality of two encoders during their intended use, i. without a separate test run, can be continuously monitored. Accordingly, the method according to the invention allows an immediate diagnosis of the failure of one of the two or both donors.

For this purpose, according to the invention, the angular position of the shaft associated therewith is determined at a first time t1 with the aid of the first encoder. Also at the time t1, the angular position of the shaft assigned to this second transmitter is determined with the aid of the second transmitter. At a second time t2 will be again determined with the aid of the first encoder, the angular position of the first encoder associated shaft and determined by means of the second encoder, the angular position of the second encoder associated shaft. Then the differences between the angular positions determined at the times t1 and t2 are formed for each of the two encoders. The difference signals thus formed are finally compared with each other to detect whether the operability of at least one of the two encoders is disturbed.

According to the invention, it is therefore proposed to check the measurement results of the two encoders on the basis of the measurement results of the other encoder. For this purpose, two angular ranges are compared with each other, which have been determined simultaneously but independently using the two encoders. The angular ranges are determined by respectively forming the difference between the angular position detected at time t2 and the angular position detected at time t1. As a result, at least part of the systematic errors of the respective encoder can be eliminated. By simply comparing the two angular ranges thus determined, it can first be ascertained whether at least one of the two encoders is defective.

According to the invention can be determined not only whether the operability of at least one of the two encoders is disturbed, but also which of the two encoders is defective. For this purpose, the signals detected by the two encoders and / or the These variables are checked independently of each other using at least one plausibility criterion. This plausibility check can always be carried out independently of the comparison of the two differential signals, or even only if it has been recognized that the functionality of at least one of the two encoders is disturbed. An encoder is then recognized as defective if the signals detected by it or the variables determined from these signals do not adequately fulfill the corresponding plausibility criterion. This may also apply to both donors at the same time. In particular, in this case, it proves to be advantageous if the comparison of the difference signals and the verification of the plausibility criteria are repeatedly performed to confirm the result of the comparison and also the plausibility check. Information about the defect of one or both donors is only forwarded in this variant of the method according to the invention when the donor or donors have repeatedly been identified as defective.

As already mentioned, the inventive method consists in checking the functionality of a speed sensor and an absolute angle encoder of an internal combustion engine, the speed sensor operates on the crankshaft of the engine and the absolute angle encoder either on the camshaft or also on the crankshaft of the engine works.

If a sender wheel with sixty minus two (60-2) teeth is used to detect the speed, which is firmly connected to the crankshaft and thus rotates with this, it can be checked to check the plausibility of the speed sensor signal, for example, whether after 58 teeth on Cranking wheel of the crankshaft is detected a reference mark gap of two teeth. Within the scope of the plausibility check of the absolute angle encoder signal, it is possible, for example, to check whether the determined camshaft angle increases monotonically from about 0 ° to 360 ° and jumps back from 360 ° to 0 °.

In this context, it proves useful to determine a tolerance range in which the deviation between the two differential signals, ie between the angular ranges determined with the aid of the two encoders, may move without the functionality of one of the two encoders being recognized as being disturbed , In this variant of the method according to the invention, the operability of at least one of the two encoders is only recognized as disturbed when the two difference signals differ by more than a predetermined tolerance value. If the two encoders work on different shafts, the ratio between the rotational movements of the two shafts must be taken into account when comparing the two differential signals.

It should be noted at this point that, for the purpose of checking the functionality of the two encoders in the context of the method according to the invention, other than the above-mentioned plausibility criteria are also used and, in addition, further plausibility criteria can be checked. Thus, for example, additional plausibility criteria can be checked if at least one encoder has been detected as defective and the comparison of the differential signals is repeated to verify this result.

drawings

Fig. 1

zeigt eine Blockdarstellung einer Anordnung zur Durchführung des erfindungsgemäßen Verfahrens, bei dem die Funktionsfähigkeit eines Drehzahlgebers und eines Absolutwinkelgebers einer Brennkraftmaschine überprüft wird.

Fig. 2

zeigt ein Flussdiagramm zur Erläuterung des erfindungsgemäßen Verfahrens.

As already discussed above, there are various possibilities for embodying and developing the teaching of the present invention in an advantageous manner. For this purpose, reference is made on the one hand to the claims subordinate to claim 1 and on the other hand to the following description of an embodiment of the invention with reference to the drawings.

Fig. 1

shows a block diagram of an arrangement for carrying out the method according to the invention, in which the functionality of a speed sensor and an absolute angle sensor of an internal combustion engine is checked.

Fig. 2

shows a flowchart for explaining the method according to the invention.

Description of the embodiment

At the in Fig. 1 illustrated embodiment, the absolute angle encoder 2 is arranged on the camshaft 1 of the internal combustion engine. The measured value acquisition of the absolute encoder 2 is based here on the Hall effect and a magnetoresistive effect. The speed sensor 4 is arranged on the crankshaft 3 of the internal combustion engine. A sender wheel 3a is fixedly connected to the crankshaft 3 so as to rotate together with it. It includes sixty minus two (60 - 2) teeth. As a speed sensor 4 is an inductive sensor which emits a signal at each tooth flank of the encoder wheel 3a.

The output signal 2 'of the absolute angle encoder 2 is supplied to a first conditioning circuit 5, while the output signal 4' of the speed sensor 4 of a second conditioning circuit 6 is supplied. The output signals 2 "and 4" of the conditioning circuits 5 and 6 are fed to a microcontroller 7, which together with the conditioning circuits 5 and 6 is part of a control unit 8.

The process according to the invention is described below for the in Fig. 1 illustrated embodiment with reference to the flowchart in Fig. 2 explained in more detail.

At a first time t1 or at a first motor position, by means of the speed sensor 4, i. determined on the basis of the detected by this crankshaft (KW) signal, a first KW angle and stored (step 11). In parallel, ie also at the time t1, a first camshaft (NW) angle is determined and stored with the aid of the absolute angle sensor 2 (method step 21). For this, the signal detected by absolute encoder 2 must be converted accordingly. In the same way, at a further second time t2 or at a further second motor position, a second KW angle and a second NW angle are determined and stored (method steps 12 and 22).

gebildet (Verfahrensschritt 13) und aus den NW-Winkelwerten wird ein Differenzwert $$\mathrm{\Delta NW}=\mathrm{NW}-\mathrm{Winkel}2-\mathrm{NW}-\mathrm{Winkel}1$$

gebildet (Verfahrensschritt 23). Der Differenzwert ΔKW stellt den vom Drehzahlgeber erfassten Winkelbereich dar, den die Kurbelwelle zwischen den Messzeitpunkten t1 und t2 bzw. den entsprechenden Messpositionen zurückgelegt hat. Dementsprechend stellt der Differenzwert ΔNW den vom Absolutwinkelgeber erfassten Winkelbereich dar, den die Nockenwelle zwischen den Messzeitpunkten t1 und t2 bzw. den entsprechenden Messpositionen zurückgelegt hatThe KW angle values become a difference value $$\mathrm{DKw}=\mathrm{KW}-\mathrm{angle}2-\mathrm{KW}-\mathrm{angle}1$$

formed (step 13) and the NW angle values is a difference value $$\mathrm{\Delta NW}=\mathrm{northwest}-\mathrm{angle}2-\mathrm{northwest}-\mathrm{angle}1$$

formed (step 23). The difference value .DELTA.KW represents the angular range detected by the rotational speed sensor, which the crankshaft covered between the measuring times t1 and t2 or the corresponding measuring positions. Accordingly, the difference value ΔNW represents the angular range detected by the absolute angle encoder, which the camshaft has covered between the measuring times t1 and t2 or the corresponding measuring positions

Ist die voranstehende Bedingung erfüllt, so wird ein Ausgangssignal 31 erzeugt, das anzeigt, dass beide Geber - Drehzahlgeber und Absolutwinkelgeber - funktionsfähig sind. Andernfalls, also wenn sich die Differenzwerte ΔKW und ΔNW unter Berücksichtigung des Übersetzungsverhältnisses von 0,5 um mehr als den vorgegebenen Toleranzwert TOL unterscheiden, wird erkannt, dass zumindest einer der beiden Geber defekt ist.Now, the two different values .DELTA.KW and .DELTA.NW are compared with each other, wherein the gear ratio between the crankshaft 3 and camshaft 1 - here 0.5 - must be considered. Any existing camshaft adjustments must be taken into account at this point. When comparing the two difference values ΔKW and ΔNW, it is checked whether the two difference values ΔKW and ΔNW differ by more than a predetermined tolerance value TOL, with which mechanical tolerances and measurement inaccuracies are taken into account. For this purpose, it is queried in step 30 whether $$\left(\mathrm{\Delta NW}-\mathrm{TOL}\right)<\left(0.5*\mathrm{DKw}\right)<\left(\mathrm{\Delta NW}+\mathrm{TOL}\right)\mathrm{,}$$

If the above condition is met, an output signal 31 is generated, which indicates that both encoders - speed sensor and absolute angle encoder - are functional. Otherwise, ie when the difference values .DELTA.KW and .DELTA.NW, taking into account the transmission ratio of 0.5 differ by more than the predetermined tolerance value TOL, it is recognized that at least one of the two sensors is defective.

In order to determine which of the two encoders is defective, a plausibility value is determined for each encoder in the exemplary embodiment described here (method steps 41 and 42). The plausibility value for the speed sensor is referred to below as P _KW , while the plausibility value for the absolute angle encoder is referred to as P _NW . To determine a plausibility value, the signal of the affected transmitter or a variable derived from this signal is compared with a plausibility criterion. As a plausibility criterion for the speed sensor signal may be mentioned at this point by way of example that after fifty-eight teeth a reference mark gap of two teeth is detected. One A possible plausibility criterion for the absolute angle sensor signal is that this signal increases monotonically from about 0 ° to about 360 ° and at 360 ° it jumps to 0 °. The plausibility value indicates how well the corresponding plausibility criterion is fulfilled.

The plausibility values P _KW and P _NW ascertained in method steps 41 and 42 are compared with one another in method steps 50, 60 and 70. If P _KW > P _NW (method step 50), then the absolute angle encoder is detected as defective and a corresponding output signal 51 is generated. Accordingly, the rotation rate sensor is detected as defective if P _KW <P _NW (step 60). Also in this case, a corresponding output signal 61 is generated. If the plausibility values P _KW and P _{NW are the} same (method step 70), then both sensors are recognized as defective. However, a corresponding output signal 71 is generated in the present embodiment only when the method steps 11 to 70 have been repeated three times and in all three cases P _KW and P _{NW were the} same.

It should be noted at this point that the method according to the invention can also be designed such that the output signals 51 and 61 are not generated until the method steps 11 to 50 or 60 have been repeatedly executed with the same result.

Claims (5)

1. Method for checking the functional capability of a first and a second sensor (2, 4), with which sensors, independently of one another, the angular position of a shaft can be determined or with which sensors, independently of one another, the angular positions of two shafts (1, 3) can be determined, the rotary movements of said shafts being linked to one another,
   characterized

   - in that at a first time t1 the angular position of the camshaft (1) which is associated with the first sensor (2) is determined by means of the first sensor (2) which is formed as an absolute angle sensor on the camshaft of a vehicle engine, and the angular position of the crankshaft (3) which is associated with the second sensor is determined by means of the second sensor (4),

   - in that at a second time t2 the angular position of the camshaft (1) which is associated with the first sensor (2) is determined by means of the first sensor (2) which is formed as an absolute angle sensor on the camshaft of a vehicle engine, and the angular position of the crankshaft (3) which is associated with the second sensor is determined by means of the second sensor (4),

   - in that the difference between the angular positions which are determined at times t1 and t2 is calculated for each of the two sensors (2, 4), and

   - in that the difference signals formed in this way are compared with one another in order to identify whether the functional capability of at least one of the two sensors (2, 4) is impaired, and

   - at least when the functional capability of at least one of the two sensors has been identified as being impaired, the signals detected by the two sensors and/or the variables determined from these signals are checked independently of one another on the basis of a plausibility criterion in order to identify which of the two sensors is faulty, with, as a plausibility criterion for the absolute angle sensor signal, a check being made as to whether the determined camshaft angle rises monotonically from approximately 0° to 360° and jumps from 360° back to 0°.
2. Method according to Claim 1, characterized in that the functional capability of at least one of the two sensors is identified as being impaired when the two difference signals differ by more than a predefined tolerance value, with the transmission ratio between the rotary movements of the two shafts possibly being taken into account.
3. Method according to Claim 1, characterized in that the method steps cited in Claims 1 and possibly 2 are repeated at least once when at least one of the two sensors has been identified as being faulty, and in that information about the fault is forwarded only when this sensor is repeatedly identified as being faulty.
4. Method according to one of Claims 1 to 3, with both the second sensor and the absolute angle sensor working on the crankshaft of an engine.
5. Method according to Claim 3, characterized in that, as a plausibility criterion for the signal of the second sensor, a check is made as to whether a reference mark gap of two teeth is identified on the sensor wheel of the crankshaft after 58 teeth.

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