DE102009008520B4 - Method and apparatus for validating the output of a position sensor - Google Patents

Abstract

A method for validating the output of a position sensor, the method comprising using a first position sensor (53) to provide (105) an output of the position of a first component (52), using the measured position of the first component (52) for generating (120 ) a prediction of the position of a second component (62) coupled to the first component (52), comprising measuring (110) the position of the second component (62) using a second position sensor (63), characterized in that the method furthermore the steps of comparing (130) the position of the second component (62) derived from the output of the second sensor (63) with the predicted position of the second component (62) and using (135) the result of the comparison as an indication of the correctness the output from the second position sensor (63), the method further comprising measuring (115) at least one temperature and adjusting (125) the predicted position of the second component (62) based on the measured temperature.

Description

This invention relates to motor vehicles, and more particularly to an apparatus and method for validating the output of a position sensor.

For vehicles with manual transmission equipped with automatic stop-start control of the engine, which are often referred to as micro-hybrid vehicles, it is desirable to maximize fuel economy by automatically switching off and whenever possible Restarting the engine is used. Currently in the market in neutral, stop-in-neutral (SIN) systems are used, but these systems do not maximize fuel economy because many drivers wait in a stationary vehicle with the vehicle in gear. Under these conditions, no SIN shutdown is triggered, and a strategy for deactivating when a gear is engaged (SIG, short for Stop-in-Gear) is required.

To use a SIG stop-start strategy, however, it is necessary to ensure that the powertrain is disengaged to prevent accidents from occurring or undesirable vehicle movement from occurring. SIG stops and starts would typically be triggered when both the clutch and brake pedal are depressed, possibly while in gear. However, in order to ensure that such a strategy is safe, the stop-start logic must only be able to start the engine when the drive train is completely disengaged when it receives a restart request initiated by the driver, for example by releasing the brake pedal as this prevents the vehicle from jerking or moving during starting. When the engine shutdown conditions have been met (e.g. vehicle speed is zero and the clutch and brake pedals are depressed), the SIG conditions should prevent the engine from shutting down if the driveline is not fully disengaged to ensure that the engine can be restarted.

Further, if the stop-start strategy allows for system-initiated restarts, such as when the battery needs to be charged or there is an A / C request, then starting should only be allowed when the drivetrain is disengaged. This is necessary in order to prevent the occurrence of undesired vehicle movement, which could have very serious consequences, during a starting process triggered by the system. This is why there is a safety-critical requirement that the drive train must be disengaged when the SIG is switched off and restarted.

By using a position sensor to measure the position of a slave cylinder piston that is used to engage and disengage a clutch, it is possible to determine if the clutch is disengaged, but due to the complexity of the clutch and the clutch actuation system, ensuring that the clutch is disengaged is important is not easy and it is imperative that the output of the position sensor is validated due to the safety-critical nature of the application.

From the DE 695 15 469 T2 an actuating device for a motor vehicle clutch is known. The actuating device there is hydraulically connected to a slave cylinder. The position of the actuating device and the slave cylinder are each recorded by a sensor system.

It is an object of this invention to provide an apparatus and method for validating the output of a position sensor.

According to a first embodiment of the invention, a method for validating the output of a position sensor is provided, the method comprising: using a first position sensor to provide an output of the position of a first component, using the measured position of the first component to predict the Generating the position of a second component connected to the first component, measuring the position of the second component using a second position sensor and comparing the position of the second component derived from the output of the second sensor with the predicted position of the second component and using the result of the comparison as an indication of the correctness of the output of the second position sensor.

If the position of the second component derived from the output of the second sensor lies in predetermined tolerance bands of the predicted position, the output of the second position sensor can be validated as reliable.

If the position of the second component derived from the output of the second sensor lies outside predetermined tolerance bands of the predicted position of the second component, the output of the second position sensor can be validated as unreliable.

The method may further include measuring at least one temperature and adjusting the tolerance bands based on the measured temperature.

The method further includes measuring at least one temperature and adjusting the predicted position of the second component based on the measured temperature.

The first component can be a piston of a clutch master cylinder, the second component can be a piston of a clutch slave cylinder and the two components are connected by means of a hydraulic connection therebetween.

According to a second embodiment of the invention, a clutch system is provided which comprises a clutch, a hydraulic clutch actuation system and an electronic control device, the hydraulic clutch actuation system having a master cylinder with a master cylinder piston, a slave cylinder with a slave cylinder piston, a hydraulic connection that connects the master cylinder with the slave cylinder connects, a first position sensor for measuring the position of the master cylinder piston and for supplying a signal indicating the measurement to the control unit, a second position sensor for measuring the position of the slave cylinder piston and for supplying a signal indicating the measurement to the electronic control unit, wherein the electronic control unit operable to use the measured position of the master cylinder piston to generate a prediction of the position of the slave cylinder piston from the output of the second sensor s compares the derived measured position of the slave cylinder with the predicted position of the slave cylinder piston and uses the result of this comparison as an indication of the correctness of the output of the second position sensor.

If the position of the slave cylinder piston derived from the output of the second sensor lies within predetermined tolerance bands of the predicted position, the electronic control unit can be operated in such a way that it validates the output of the second position sensor as reliable.

If the position of the second component derived from the output of the second sensor lies outside predetermined tolerance bands of the predicted position of the second component, the electronic control unit can be operated in such a way that it validates the output of the second position sensor as unreliable.

The electronic control device can also be operated in such a way that it determines at least one temperature and adjusts the tolerance bands on the basis of the measured temperature.

The electronic control device of the invention is also operable to determine at least one temperature and adjust the predicted position of the slave cylinder based on the measured temperature.

Determining at least one temperature can include measuring at least one temperature or can include predicting at least one temperature by modeling or calculation.

• 1 eine schematische Darstellung eines Micro-Hybrid-Kraftfahrzeugs mit einem Stopp-Start-System;
• 2 ein schematisches Diagramm einer Kupplung und eines Kupplungsbetätigungssystems, welche in dem in 1 gezeigten Micro-Hybrid-Fahrzeug verwendet werden;
• 3 ein Übersichtsflussdiagramm, das die zum Steuern des Betriebs eines Verbrennungsmotors, der einen Teil des in 1 gezeigten Fahrzeugs bildet, verwendeten Maßnahmen zeigt;
• 4 ein Übersichtsflussdiagramm, das ein Verfahren zum Bereitstellen eines Hinweise auf den Einrückzustand der in 2 gezeigten Kupplung zeigt;
• 5 ein Flussdiagramm, das ein erfindungsgemäßes Verfahren zum Validieren eines Ausgabesignals von einem Kupplungsnehmerzylinder, der einen Teil des in 2 gezeigten Kupplungsbetätigungssystems bildet, zeigt;
• 6 ein Flussdiagramm, das eine erste Ausführungsform eines Verfahrens zum Ermitteln einer aktuellen Nullstellung eines Kolbens eines Kupplungsnehmerzylinders, der einen Teil des in 2 gezeigten Kupplungsbetätigungssystems bildet, zeigt;
• 7 ein Flussdiagramm, das eine zweite Ausführungsform eines Verfahrens zum Ermitteln der aktuellen Nullstellung des Kolbens des Kupplungsnehmerzylinders zeigt;
• 8 ein Flussdiagramm, das ein Verfahren zum Ermitteln einer Schwellenverschiebung zeigt, die erforderlich ist, um ein Ausrücken der in 2 gezeigten Kupplung zu erzielen;
• 9 ein Flussdiagramm, das ein Verfahren zum Ermitteln des Einrückrückzustands der in 2 gezeigten Kupplung zeigt;
• 10 eine schematische Darstellung der Bewegung eines Kolbens eines Kupplungsnehmerzylinders, der einen Teil des in 2 gezeigten Kupplungsbetätigungssystems bildet;
• 11 eine Tabelle, die während des in 7 gezeigten Betriebs eines Verfahrens erhaltene hypothetische Werte zeigt; und
• 12 eine Tabelle, die während des in 6 gezeigten Betriebs eines Verfahrens erhaltene hypothetische Werte zeigt.

The invention will now be described by way of example with reference to the accompanying drawings. Here show:

• 1 a schematic representation of a micro-hybrid motor vehicle with a stop-start system;
• 2 FIG. 3 is a schematic diagram of a clutch and clutch actuation system used in the FIG 1 shown micro-hybrid vehicle can be used;
• 3 Fig. 3 is a high level flowchart showing the processes involved in controlling the operation of an internal combustion engine that forms part of the in 1 vehicle shown forms, shows measures used;
• 4th Figure 3 is a high level flow diagram illustrating a method of providing an indication of the state of engagement of the in 2 shows the coupling shown;
• 5 a flowchart showing a method according to the invention for validating an output signal from a clutch slave cylinder which is part of the in 2 shows the clutch actuation system shown;
• 6th a flowchart showing a first embodiment of a method for determining a current zero position of a piston of a Clutch slave cylinder, which is part of the in 2 shows the clutch actuation system shown;
• 7th a flowchart showing a second embodiment of a method for determining the current zero position of the piston of the clutch slave cylinder;
• 8th FIG. 3 is a flow chart showing a method for determining a threshold shift required to disengage the in FIG 2 to achieve coupling shown;
• 9 FIG. 3 is a flowchart illustrating a method for determining the state of engagement of the in 2 shows the coupling shown;
• 10 a schematic representation of the movement of a piston of a clutch slave cylinder which forms part of the in 2 forms clutch actuation system shown;
• 11 a table that was created during the in 7th operation of a method shown shows hypothetical values obtained; and
• 12th a table that was created during the in 6th operation of a method shown shows hypothetical values obtained.

With particular reference to 1 and 2 is a motor vehicle 5 with an engine 10 shown of a multi-speed manual transmission 11 drives. The gear 11 is with the engine 10 through a coupling system 50 by a driver of the motor vehicle 5 with the help of a clutch pedal 25th is manually engaged or disengaged, driving connected.

The gear 11 has a shift lever (not shown) which is movable between a plurality of positions, including at least one position in which a gear forming part of the multi-speed transmission is selected and a neutral position in which no gears of the multi-speed transmission are selected. When the shift lever is moved to the neutral position, the multi-speed transmission is in place 11 is said to be in a neutral state in which no drive can be transmitted through the multi-speed transmission and when the shift lever is moved to an in-gear position, the multi-speed transmission is located 11 is said to be in a gear state in which drive can be transmitted through the multi-speed transmission.

An engine starter in the form of an integrated starter generator 13th is with the engine 10 drivingly connected and is in this case by a flexible drive in the form of a drive belt or a drive chain 14th with a crankshaft of the engine 10 tied together. The starter generator 13th is connected to a source of electrical energy in the form of a battery 15th connected to starting the engine 10 is used and recharged by the starter-generator when it operates as an electric generator. It goes without saying that the starter generator 13th by a starter motor to start the engine 10 could be replaced.

While the engine is starting 10 drives the starter generator 13th the crankshaft of the engine 10 on, and at other times the starter generator is powered by the engine 10 driven to generate electrical power.

A driver-operated on-off device in the form of a key-operated ignition switch 17th is used to control the overall operation of the engine 10 used. Ie if the engine 10 is running, the ignition switch is located 17th in an "on" position (key-on) and when the ignition switch is on 17th is in an "off" position (key off), the motor can 10 do not walk. The ignition switch 17th Also includes a third current position for manually starting the engine 10 is used. It will be understood that other devices can be used to provide this functionality and that the invention is not limited to the use of a key operated ignition switch.

An electronic control unit 16 is connected to: the starter generator 13th , the engine 10 , a shift lever sensor 12th , which is used to monitor whether the transmission 11 is in neutral or engaged, a vehicle speed sensor 21 , which is used to measure the speed of rotation of an impeller 20th serves, a brake pedal position sensor 24 used to monitor the position of a brake pedal 23 serves, a clutch master cylinder position sensor 53 used to monitor the position of a master cylinder piston 53 and indirectly the position of the clutch pedal 25th serves, with which the master cylinder piston is mechanically connected, a clutch slave cylinder position sensor 53 , which is used to monitor the position of the slave cylinder piston 62 and a throttle position sensor 19th used to monitor the position of an accelerator pedal 18th serves.

The position of the master and slave cylinder pistons 52 and 62 can from the sensors 53 , 63 can be measured using any number of position sensing technologies such as and without limitation PLCD and Hall Effect.

The accelerator 18th provides a driver input of the required power output of the engine 10 . When the accelerator 18th is moved out of a rest position, it is, as they say, in a stepped position or in a stepped state.

It goes without saying that the term shift lever sensor is not limited to a sensor that monitors the position of the shift lever, but rather any device that can provide feedback as to whether the transmission is in operation 11 is engaged or in neutral, and that a shift lever sensor is not a must for a SIG stop-start system.

Similarly, the term brake pedal sensor is not limited to a sensor that monitors the position of the brake pedal, but rather any device that provides feedback as to whether an operator of the motor vehicle is present 5 Press the brake pedal 23 has exercised the brakes of the motor vehicle 5 to operate. For example, the brake pedal sensor could measure the pressure of the fluid in monitor one or more brake lines. When the brake pedal 23 has been pedaled enough to apply the brakes, it is said to be in a stepped condition or position

Referring now in particular to 2 it can be seen that the coupling system 50 a clutch 2 and a hydraulic actuation system that controls the clutch 2 with the clutch pedal 25th connects, includes. The hydraulic actuation system includes a mechanical link that is the clutch pedal 25th with the master cylinder piston 52 of the main cylinder 51 connects, a hydraulic connection or line 55 having an output from the master cylinder 51 with one end of a slave cylinder 61 connects in which the slave cylinder piston 62 Slidably installed, and a mechanical connection 65 from the slave cylinder piston 62 to a release bearing 6th that is used to make the clutch 2 to move in and out selectively.

It goes without saying that a shift of the clutch pedal in the direction of the arrow “clutch pedal travel” in 2 corresponding shifts D _master and D _{slave of} the main and slave piston 52 and 62 generated in a clutch disengaging direction.

The coupling 2 is in this case a clutching / disengaging friction clutch and includes a cover and spring assembly 3 , a printing plate 4th and a clutch disc 7th that is between the thrust washer 4th and the flywheel 8th attached to a crankshaft (not shown) of the engine. The coupling 2 is of conventional construction and is not described in detail, it is only necessary at this point to know that a movement of the release bearing 6th in the direction of arrow D _Clutch through the slave cylinder piston 62 is movement in a clutch disengaging direction and the opposite movement is movement in a clutch engaging direction. Sometime during the range of motion of the release bearing 6th the state of the clutch changes 2 from a disengaged state in which there is essentially no torque by means of the clutch from the engine 10 to the gearbox 11 can be transmitted to an engaged condition in which significant torque can be transmitted. This clutch engagement position is often referred to as the slip point. The value of the torque depends on many factors, including the mechanical relationship between the motor 10 and the drive wheels (not shown), the friction in the drive train, the friction between the running wheels and the road, vary from vehicle to vehicle, but generally speaking it is a torque that, when applied, generates a jerk that is generated by a driver of the motor vehicle can be noticed and is typically in the range of 3 to 10 Nm.

The electronic control unit 16 receives multiple signals from the engine 10 , including a signal that indicates the speed of the engine 10 from a speed sensor (not shown), and sends signals to the engine used to control engine shutdown and start-up 10 be used. In this case the engine is 10 a spark ignition engine 10 and that of the electronic control unit 16 The signals sent are used to control a fuel supply system (not shown) for the engine 10 and an ignition system (not shown) for the engine 10 used. Would be the engine 10 is a diesel engine then only the fuel delivery to the engine would be controlled. The electronic control unit 16 may include various components including a host computer, storage devices, timers, and signal processing devices for converting the signals from those to the electronic control unit 16 connected sensors in data received from the electronic control unit 16 to control the operation and in particular the automatic stop and start of the engine 10 be used. It is also understood that the electronic control unit 16 can be formed from several individual electronic control units that communicate with one another in order to achieve the required functionality.

During normal engine operation, the electronic control unit is 16 operable to the the engine 10 to regulate the fuel supplied and to adjust the ignition system so that the engine 10 the spark plugs deliver sparks at the right time to produce the desired engine torque.

The electronic control unit 16 controls the operation of the engine 10 which can be operated in two modes, a first or stop-start-run mode and a second or manual mode.

The one used to determine if the engine 10 is operated in the second operating mode or in the first operating mode, the primary factor serving is whether the motor vehicle 5 emotional. When the motor vehicle 5 moves, the motor is operated in the second operating mode and the motor 10 is constantly running and when the motor vehicle 5 does not move, the motor will 10 operated in the first mode in which an automatic stop-start operation of the engine takes place, provided that other factors described below indicate that the stop-start operation is possible.

In the first or the stop-start operating mode, the engine is 10 from the electronic control unit 16 stopped and started in a targeted manner without intervention by the driver when one or more predetermined stop and start conditions of the engine are present. These shutdown and start conditions are based on those provided by the electronic control unit 16 from the throttle sensor 19th , the brake sensor 24 , the coupling system 50 and the shift lever sensor 12th received signals. The position or state of the clutch 2 , the accelerator pedal 18th , the brake pedal 23 and the transmission 11 are all different automotive variables used to control the operation of the engine 10 can be used. It will be understood that many other variables can be used including, but not limited to, PAS pump operating status, brake vacuum sensor output, manual stop-start inhibit switch.

When the engine 10 works in the second mode, it runs continuously as long as the ignition switch is on 17th remains in the "on" position, and the motor 10 is made by manually operating the ignition switch 17th stopped and started.

It is true that the measurement of the motor vehicle speed is described above with reference to the use of a wheel sensor 21 as such sensors are already often present on a motor vehicle as part of an anti-lock braking system, but it will be understood that other suitable means can be used to measure the speed of the motor vehicle 5 to determine, for example, a sensor that measures the speed of rotation of an output shaft of the transmission 11 measures.

Referring now to 3 an overview flowchart of the methodology is shown which is used to determine whether stop-start or the first operating mode is possible.

The process continues at step 30th one where the ignition key is 17th is in the "off" position and remains in this state until the ignition key 17th at step 31 is moved to the "on" position, causing the motor 10 at step 32 starts.

Then at step 33 determines whether the conditions for stop-start are met. One of these conditions can be whether the vehicle is 5 moves above a predetermined speed and, as far as this invention is concerned, also includes the state of engagement of the clutch 2 .

If one ignores all other conditions that may have to be met, if the condition of the clutch 2 is determined as "disengaged", then the conditions for SIG stop-start operation are met and the process moves to step 35 before where the first operating mode is selected, but when the state of the clutch 2 is determined as "engaged", then the conditions for the stop-start operation are not met and the process moves to step 34 where the second or normal operating mode is selected.

After the steps 34 and 35 moves the procedure to step 36 before to determine if the ignition key is 17th is still in the "on" position. If the key is still “On” then the procedure returns to step 33 back, but if it is determined that the ignition key is in the "off" position, the method ends at step 37 .

Referring now to 4th A high level flowchart of a method is shown that includes a number of related routines used to determine the state of engagement of the clutch 2 required are.

The process continues at step 31 on when the ignition key is moved to an "on" position, then step 100 determines whether the output of the slave cylinder position sensor 63 is reliable.

If it is determined that the slave cylinder position sensor 63 is not reliable, then the procedure advances to step 150 before where a flag is set to zero. It goes without saying that in practice the flag for “key on” can be set to zero in order to provide a uniform start condition. The procedure then moves to step 500 where the state of the flag is communicated to the stop-start control system as an indication of whether the first or second mode of operation is to be selected. In the example shown, setting the flag to zero always results in the stop-start system selecting the second operating mode. The procedure then moves to step 600 before where it is determined whether the ignition key is 17th is still in the "on" position and if so the procedure returns to step 100 otherwise the procedure ends at 1000.

However, if at step 100 it is determined that the slave cylinder position sensor 63 is reliable, then the process advances 100 to step 200 before where a current zero position for the slave piston 62 is determined.

The procedure then moves to step 300 before, where a required displacement _threshold (X THRES) is determined from the zero position of the slave piston to ensure disengagement.

Then at step 400 determines whether a measured displacement of the slave piston 62 exceeds the displacement _threshold (X THRES) and if so then the flag is set to one, otherwise the flag is set to zero.

Then the procedure moves to step 500 before where the state of the flag is communicated to the stop-start control system as an indication of whether the first or second mode of operation must be selected. In the example shown, setting a flag to zero always causes the stop-start system to select the second operating mode, and setting a flag to one always causes the stop-start system to select the first operating mode. Then the procedure moves to step 600 before where it is determined whether the ignition key 17th is still in the "on" position and, if so, the procedure returns to step 100 otherwise the procedure ends at 1000.

It will be understood that the opposite flag logic could be used or some other form of indicator could be used, for example the method of step 34 or step 35 of the in 3 procedure shown, depending on whether the test is at 400 passed or failed, and step 150 could output “GO TO Step 34 " be.

Referring now in particular to 5 there is a method according to the invention, as in step 100 in 4th shown in more detail.

In summary, the positions of the pistons are stated 52 , 62 the master and slave cylinders 51 , 61 of the hydraulic clutch release system with the help of the master and slave cylinder position sensors 53 and 63 measured, the output signals from these sensors to the electronic control unit 16 be transmitted. The electronic control unit is operable to receive the information from the master cylinder position sensor 53 measured master cylinder piston position with that of the slave cylinder position sensor 63 measured slave cylinder piston position to verify or confirm the position of the slave cylinder piston 62 to offer.

When it is confirmed that the slave cylinder piston 62 is where it is expected, then it is assumed that the output signal is from the slave cylinder position sensor 63 is a reliable indication of the slave cylinder piston position.

It goes without saying that after the first master data has been set for the vehicle 5 the outputs from the two position sensors 53 , 63 Can be calibrated for absolute zero by the main and slave pistons 52 , 62 to the end of their respective cylinder 51 , 61 be moved from which they are moved when the clutch pedal 25th is kicked or a sensor adjustment arrangement is used to achieve these baseline values.

Now referring back to 5 will at step 105 the position of the master cylinder piston 52 with the help of the master cylinder position sensor 53 measured and then at step 115 a system temperature is determined. The system temperature can be obtained from one or more temperature sensors located at various locations in the clutch actuation system, from either or both of the master and slave cylinder position sensors 53 and 63 are obtained when a temperature signal from the temperature compensation circuits that these sensors 53 , 63 assigned, can be obtained, or can be obtained by modeling or computation.

Then at step 120 from the electronic control unit 16 a predicted slave cylinder position from that from the master cylinder position sensor 53 received signal.

Two methods of making this prediction are possible.

In a first option, the master cylinder piston position is used as input to a polynomial or series of polynomials making up a spline, a single filter or a single transfer function, and the output from the polynomial, spline, filter or transfer function is used as a Estimation or prediction of slave cylinder piston position used.

A second option uses the master cylinder piston position sensor as input to two lookup tables. The first of these lookup tables generates a value for the corresponding maximum expected slave cylinder piston position, and the second of these lookup tables generates a value for the corresponding expected minimum position of the slave cylinder piston.

Then at step 125 the prediction of the slave cylinder position corrected for temperature. This is desirable because of several factors influencing the relationship between the position of the master cylinder piston 52 and the position of the slave cylinder piston 62 However, by far the most important of these factors is temperature, which causes an expansion and contraction of the hydraulic fluid used to transmit motion and force from the master cylinder 51 to the slave cylinder 61 is used, and an expansion / contraction of the to connect the master and slave cylinders 51 and 61 the pipes used. The expansion of these tubes requires additional fluid to fill the same, which is known as the "volume loss effect", and is the main reason for differences between the master and slave cylinder piston positions.

As the transfer function or relationship that is used to predict the position of the slave cylinder piston 62 must contain the full range of possible noise factors, and the temperature range that occurs during the use of the vehicle 5 occurs, is likely to be wide, in order to be stable over the entire temperature range, a wide tolerance band must be used to prevent the test from failing when the slave cylinder position sensor 63 actually works normally. The danger of using a wide tolerance band is that a problem that is not related to the temperature will not be detected because it is too small with respect to the tolerance band required to take temperature fluctuations into account.

Therefore, by including a temperature sensor or temperature model to provide control algorithms with temperature information, the temperature factor can be effectively eliminated, allowing a smaller tolerance band to be used to account for other noise factors and thereby the responsiveness of the system to actual errors in the operation of the slave cylinder position sensor 63 reinforced.

It goes without saying that in practice the steps 120 and 125 can be combined, ie the transfer function or the relationship used to predict the position of the slave cylinder piston 62 include temperature compensation, but are shown separately as it would be possible, although not desirable, to rely on the steps 115 and 125 to do without and to use large tolerance bands to take temperature fluctuations into account.

Now referring back to 5 will at step 130 the predicted position (P _pred ) of the slave cylinder piston 62 with the measured by the slave cylinder position sensor 63 at step 100 derived position compared, and at step 135 it is determined whether the measured position (Pmeas) is within predetermined upper and lower tolerance limits.

oder unter Verwendung der vorstehenden Vorhersage und Grenzwerte: - $$\text{Ist 14}\text{,95}<{\text{P}}_{\text{meas}}<\text{15}\text{,05}?$$

For example, if the predicted position is 15 mm and the tolerance limits are + or -0.05 mm, then the comparison would have been at step 130 the following form: - $${\text{Is P}}_{\text{pred lower limit}}<{\text{P.}}_{\text{meas}}<{\text{P.}}_{\text{pred upper limit}}?$$

or using the prediction and limit values above: - $$\text{Is 14}\text{, 95}<{\text{P.}}_{\text{meas}}<\text{15th}\text{, 05}?$$

If the answer to the test is YES, then the method moves to step 140 before, and if the answer is NO, the procedure advances to step 145 before.

It should be understood that in practice this comparison is a comparison of digital data or voltage values and not actual dimensions.

When the procedure goes to step 140 is advanced, this indicates that the slave cylinder position sensor 63 has been verified and can be used, and thus the method goes to step 200 back to the main proceedings. If the procedure is reversed to step 145 advanced then this indicates that the verification process failed and, although not shown, an error flag could be set. The procedure then returns to step 150 back to the main procedure, indicating that the engine must be operated in the second or normal operating mode because of the output of the slave cylinder position sensor 63 cannot be trusted.

The at step 130 and 135 The comparisons described above can be performed on a continuous or repetitive basis after "key-in" or only when a number of input conditions are met.

An example of an input condition is when the master cylinder piston 52 is within a certain part of its range, such as near the engaged or disengaged end stop.

Other examples of the input conditions are when the speed of the master cylinder piston 52 is below a certain threshold or when the speed of the slave cylinder piston 62 is below a certain threshold.

While the clutch 2 is moved between the fully engaged and fully disengaged positions, the piston engages 62 of the slave cylinder 61 a short distance back, typically on the order of 8 mm. The slave cylinder 61 however, has a much larger range of possible travel, typically on the order of 24mm, and the smaller range of motion of 8mm will move during the life of the clutch when the clutch is engaged 2 wears out or is replaced (see 10 ), within this larger range.

The effect of clutch wear consists in moving the slave cylinder to the rest or zero position 62 when the clutch 2 indented fully to the left, as in 10 is shown, and this movement of the zero position must be compensated if measurement errors are to be avoided.

A procedure is required to minimize the rest position of the slave cylinder piston 62 determine whereby the effect of this movement of the smaller area within the larger area is canceled when the output of the slave cylinder position sensor 63 should be used to actually give an indication of the state of engagement of the clutch 2 admit. 6th shows a first embodiment 200a of a procedure 200 to provide such a minimum zero position, thereby eliminating or compensating for the effects of clutch wear.

The procedure 200a starts at step 31 , ie when the ignition switch 17th is moved to an "on"position; the first measure taken by the method is to set a current offset value Z equal to a maximum zero offset value M.

The maximum zero offset value is measured at a value greater than or equal to the absolute slave cylinder piston position at the extremely possible point of movement of the slave cylinder piston 62 in the disengaged direction (which as in 10 shown in this case is 24 mm). This has the effect that when the key is switched on before the clutch is actuated 2 indicates that the clutch is engaged, regardless of its actual state. This is the preferred safety condition in a stop-start system as it prevents unsafe starting of the engine.

The position of the slave cylinder piston 62 is constantly by the slave cylinder position sensor 63 monitored, and the minimum zero offset value Z of the slave cylinder piston 62 will be like at step 210 displayed saved.

For those skilled in the art it will be understood that although there is at step 210 would be possible to determine the fully engaged position and then the position of the slave cylinder piston 62 to measure, in practice, the position of the piston 62 is constantly measured and the minimum displacement position of the piston 62 is used as the engaged position.

Then at step 215 the new measurement of zero offset Z _NEW with the one currently in the electronic control unit 16 stored value of zero offset compared.

If the new value of zero offset Z _{NEW is} less than the currently stored value of zero offset Z, then the method moves to step 220 otherwise the procedure advances to step 225 before.

At step 220 the value of zero offset Z is set to be equal to the new value of zero offset value Z _NEW , and the method moves to step 230 before, whereas at step 225 the value of zero offset remains unchanged and Z is set equal to the existing value of Z, and the method then advances to step 230 .

At step 230 it is determined whether the ignition switch 17th is still in the "on" position and if so then the procedure returns to step 210 back but when the ignition switch 17th is now "Off", the procedure ends at step 240 .

This procedure ensures that if the clutch wears out 2 the zero offset value Z is adjusted to make the actual zero value equal to the position of the slave cylinder piston 62 maintain when the clutch 2 is fully engaged and there is no shifting of the clutch pedal 25th is present. If this method is not used, the slave cylinder position sensor output would be 63 if the clutch is worn 2 would have an increasing error and would indicate that the slave cylinder piston is 62 hasn't moved as far as he actually did. This poses a problem when the output of the slave cylinder position sensor 63 is used to control other vehicle characteristics, such as stop-start based on the clutch engagement condition, since the position of the slave cylinder piston 62 must be determined with a high degree of accuracy (less than 0.1 mm) in order for the engagement state of the clutch 2 can be determined accurately and reliably.

It goes without saying that the loop 210 , 215 , 220 , 230 , 210 or 210 , 215 , 225 , 230 , 210 is repeated as long as the ignition switch 17th remains in the "on" position.

Referring now to 7th there is a second embodiment of a method 200 to determine a zero offset value for the slave cylinder piston 62 that with the method described above with respect to the steps 31 until 230 corresponds and is therefore not described again in detail with regard to these steps.

This method 200b the second embodiment is used when the release bearing 6th or the clutch 2 includes an automatic wear compensation feature to counteract the effects of clutch wear. A such device works after a series of coupling processes, either when the coupling 2 is in the process of engaging to the effects of wear on the clutch disc 7th to compensate, and thus the effect is as in 10 is shown moving the zero offset position Z a predetermined amount, such as 0.1 mm, away from the fully engaged position.

Now referring back to 7th from step 230 the process ends at step 240 when the ignition switch 17th is off, but when the ignition switch 17th is still one, the procedure advances to step 250 before where it is determined whether the clutch 2 has been in operation since the last process cycle.

If the clutch has not been operated, ie if it has been fully engaged or remained fully disengaged, then the method advances to step 210 however, if there was a clutch operation, that is, if it was disengaged and then engaged, then the method advances to step 260 before, where a small value S is added to the currently stored value of zero offset Z. The procedure then moves to step 210 before.

The effect of the perturbation or increment S is best with reference to 11 and 12th evident.

Referring first to 11 can view the tabulated outputs of the various steps in the process 200b using hypothetical values of M = 25 mm, Z _NEW = 0.8 mm and S = 0.2 mm. It will be understood that no actual dimensions are intended to be used to perform this procedure; this method can be performed using digital data or a value such as electrical voltage, but actual measured values are used for the purpose of illustration.

In the upper half of the table it can be seen that the effect of the increment S on the value of zero offset Z is determined by the steps 215 until 230 expressed decreasing algorithm is canceled. That is, Z remains at 8.0 for this range of repetitions, which is insufficient for wear to have occurred and for which no self-adjustment by the release bearing 6th or the clutch 2 assigned automatic wear compensation mechanism has taken place. It goes without saying that if there is clutch wear, the value Z _NEW decreases and thus with step 215 the result would be YES and Z _NEW would be set as the new z-value; if z. B. the new fully engaged position of the slave piston 62 at step 210 is measured as 7.95 mm and the current value of Z is 0.8 mm, then the test is at 215 passed and Z is set at 7.95 mm.

The lower half of the table shows the situation when a self-adjustment by the release bearing 6th or the clutch 2 assigned automatic wear compensation mechanism has taken place. In this case, an adjustment of 0.1 mm has been made. The effect of this is that the test is at step 215 is passed because 8.1 mm is smaller than 8.2 mm, and then at step 220 updated the zero offset value to 8.1 mm. Therefore, the effect of the automatic wear adjustment was enhanced by the in 7th shown procedures 200b compensated.

Referring now to 12th is the situation shown when that in 6th shown procedures 200a with a clutch 2 or a release bearing 6th with wear compensation is used.

The top half of the table is the same as in 11 shown, but the lower half of the table is different, since no increment S step is used in this method.

Therefore, the method occurs after automatic adaptation by the clutch 2 or the release bearing 6th of 0.1 mm as before in step 215 with a Z _NEW value of 8.1 mm and, since the Z value was not incremented by the value S, remains at 0.8 mm, the test at 215 is not passed and therefore the zero offset Z remains 0.8 mm, and regardless of how many automatic adjustments are made, this is the case because there is no way that the zero offset Z is increased by the algorithm, only that it is decreased by it or kept the same. This causes every time an automatic adjustment by the clutch 2 or the release bearing 6th occurs, an increasing error is generated and the slave cylinder position sensor 63 incorrectly indicates that the slave piston 62 is closer to the disengaged position than it actually is, and thus there is a risk that it will be determined that the clutch is engaged 2 is disengaged when it actually remains indented. It will be understood that this error will only be corrected when the next "key-on" cycle is started.

In summary, the ratchet algorithm works as follows: if an absolute slave cylinder piston position is detected that is further in the engaged direction than the currently maintained offset value, then the ratchet algorithm replaces the currently maintained zero offset value with the newly measured value . Thus, the currently maintained value is always the most engaged position that is detected in this key cycle.

The zero offset value maintained by the ratchet can be used as a "zero offset" to determine the relative position of the slave cylinder piston 62 to be calculated by subtracting the zero offset Z from the absolute slave cylinder piston position, as described in more detail below.

In some circumstances it may be preferable to prevent the ratchet algorithm from working. For example, at high engine speeds, a deformation of clutch components, such as the diaphragm spring, can lead to slave cylinder piston positions, which incorrectly indicate the fully engaged position of the slave piston 62 give. Under these or other circumstances, “freezing” the ratchet algorithm can prevent errors. If it is frozen, the ratchet mechanism does not update its currently maintained value and thus, for example using the values given above, measuring an incorrect value of Z _NEW = 7.5 mm has no effect since the zero offset Z at 0.8 mm is frozen.

As explained above, the zero offset Z is set every time the clutch is engaged 2 disengaged or engaged, perturbed or incremented to any movement of the slave cylinder piston caused by the clutch's automatic or self-adjusting mechanism 2 is effected to balance. The perturbation is applied by adding a small amount S, typically in the range 0.1 mm and 0.2 mm, to the zero offset Z, which has the effect of being the zero point of the relative range of the slave cylinder piston 62 move in the disengaged direction with respect to the absolute range. The fault is triggered every time the clutch is released 2 is disengaged and then subsequently engaged, but the automatic adjustment mechanism does not adjust every time the clutch is disengaged 2 is disengaged and then engaged, and typically many miles can be traveled by the vehicle between adjustments. However, disturbances that occur on occasions when no automatic adjustment takes place are quickly eliminated by the ratchet algorithm. The magnitude of the perturbations or increments must be chosen to be slightly larger than the adjustments made by the automatic adjustment mechanism so that the adjustments are in a single perturbation.

To provide an inexpensive and reliable method of determining the engagement state of a clutch 2 provide, the inventors have recognized that the displacement of the slave cylinder piston 62 from its fully engaged position can be used to provide a value indicating whether the clutch is 2 is engaged or disengaged. The term engaged or disengaged in this context means whether there is a predetermined amount of torque through the clutch 2 is transmitted.

• Fertigungsschwankungen von Stück zu Stück, Anordnungsunterschiede, Verschleiß,
• Umweltbedingungen wie zum Beispiel Temperatur und Sensorgenauigkeit. Dies stellt sicher, dass ein einziger Schwellenwert für „Kupplung ausgerückt“ pro Fahrzeuglinie kalibriert werden kann, so dass die Notwendigkeit des Lernens des Punkts des Ausrückens/Einrückens der Kupplung vermieden wird.

The solution presented here is determined based on the output from the slave cylinder position sensor 63 showing the linear position of the slave cylinder piston 62 measures whether the clutch 2 is in a disengaged state. The procedure proposed here is intended to indicate that the clutch 2 is disengaged when the detected position of the slave cylinder piston 62 goes beyond a threshold value on its way. This threshold must be calibrated so that all tolerances in the clutch actuation system 50 and the clutch 2 must be taken into account, and these tolerances include:

• Manufacturing fluctuations from piece to piece, differences in arrangement, wear and tear,
• Environmental conditions such as temperature and sensor accuracy. This ensures that a single "clutch disengaged" threshold can be calibrated per vehicle line, avoiding the need to learn the point of clutch disengagement / engagement.

Of these variables, the most important is temperature, as temperature fluctuations affect not only the physical size of components, but also the friction properties of the clutch 2 . That is why in 8th has shown a method that compensates for temperature-related errors, thereby improving the accuracy with which the desired displacement threshold can be calculated.

The procedure 300 starts at step 31 representing a "key-on"event; the next step is to measure the temperature of the clutch actuation system 50 with one or more key positions. This can be done using a number of dedicated temperature sensors or can be done using an output from a temperature compensation circuit of the slave cylinder position sensor 63 can be achieved. Regardless of the method used, this temperature value will be used at step 320 is used to obtain a temperature compensated value of the displacement _threshold X THRES which is used to determine the state of engagement of the clutch.

The in step 320 The methods used are many, but can include: Using a model of the clutch actuation system to determine the displacement of the slave cylinder piston 62 that is required to make sure the clutch 2 is disengaged; experimental data stored in one or more lookup tables that can be used to determine the displacement of the slave cylinder piston 62 determine what is needed to ensure the clutch 2 is disengaged; and estimating the temperature of the clutch 2 and / or the clutch actuation system based on the ambient temperature combined with other sensor signals or information contained in the electronic control unit 16 such as engine torque, engine speed, vehicle speed, etc.

It goes without saying that step 320 comprises at least one algorithm to determine the position of the slave cylinder piston 62 with the state of engagement of the clutch 2 to correlate, and that this algorithm or algorithms is / are modified in order to input the measured temperature from step 310 to consider.

Then at step 330 the value of the temperature-compensated displacement _threshold value X THRES in the electronic control unit 16 saved for further use. Then the process ends 300 at step 340 .

Referring now to 4th and 9 there is a procedure 400 to determine the state of engagement of the clutch 2 disclosed.

The procedure 400 starts at step 31 representing a "key-on"event; then at step 410 with the help of the slave cylinder position sensor 63 the measured displacement (X _MEAS ) of the slave cylinder piston 62 measured from its absolute zero position.

Then at step 420 an actual displacement of the slave cylinder piston 62 calculated by using one of the above with reference to 6th and 7th described procedure 200a and 200 b generated zero offset Z is subtracted from the measured value of the displacement.

XACT =

die tatsächliche Verschiebung des Nehm erzyl inderkolbens;

XMEAS =

die von dem Nehmerzylinderstellungssensor gemessene Verschiebung; und

Z =

Null Offset.

That means X _ACT = XMEAS-Z where

XACT =

the actual displacement of the cylinder piston;

XMEAS =

the displacement measured by the slave cylinder position sensor; and

Z =

Zero offset.

Then the procedure moves to step 430 before where the actual displacement X _{ACT of} the slave cylinder piston 62 with the method described above and in 8th procedure shown 300 determined displacement threshold is compared.

• Ist X_ACT > X_TRHES wird verwendet, um zu ermitteln, ob die Kupplung 2 eingerückt oder ausgerückt ist.

Ie the test: -

• If X _ACT > X _TRHES is used to determine whether the clutch is on 2 is engaged or disengaged.

It will be understood that there can be two threshold values for taking into account the effects of hysteresis, one for each direction of the sensor signal. That is, if the signal was increasing, one threshold would be used, and if the signal was decreasing, a second threshold would be used.

If the test passes, the procedure advances to step 450 before and the flag is set to one (1) indicating that the clutch is disengaged, but if the test is at step 430 fails, the flag at step 460 is set to zero (0), indicating that the clutch has been determined 2 is indented.

10 shows the situation when X _{ACT is} greater than X _THRES , ie the actual displacement of the slave cylinder piston 62 is greater than the threshold shift, and the method would therefore determine that the clutch 2 is disengaged.

After the steps 450 and 460 moves the procedure to step 470 and the control returns to the in 4th step shown 500 return to the main flow routine.

The methods described above are illustrative examples, and the steps therein may be performed sequentially, synchronously, simultaneously, or in a different order depending on the application, if necessary.

It will be understood by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments, it is not limited to the disclosed embodiments and that one or more modifications of the disclosed embodiments or alternative embodiments could be devised without departing from the scope of the Invention as set out in the appended claims.

Claims (9)

A method for validating the output of a position sensor, the method comprising using a first position sensor (53) to provide (105) an output of the position of a first component (52), using the measured position of the first component (52) for Generating (120) a prediction of the position of a second component (62) coupled to the first component (52), comprising measuring (110) the position of the second component (62) using a second position sensor (63), characterized in that, that the method further comprises the steps of comparing (130) the position of the second component (62) derived from the output of the second sensor (63) with the predicted position of the second component (62) and using (135) the result of the comparison as an indication on the accuracy of the output from the second position sensor (63), the method further comprising measuring (115) at least one temperature and adjusting (125) the predicted position of the second component (62) based on the measured temperature. Procedure according to Claim 1 , characterized in that if the position of the second component (62) derived from the output of the second sensor (63) falls within predetermined tolerance bands of the predicted position, the output of the second position sensor (63) is validated as reliable. Procedure according to Claim 1 or 2 characterized in that if the position of the second component (62) derived from the output of the second sensor (63) falls outside predetermined tolerance bands of the predicted position of the second component (62), the output from the second position sensor (63) is validated as unreliable . Procedure according to Claim 2 or 3 , characterized in that the method further comprises adjusting the tolerance bands based on the measured temperature. Method according to one of the Claims 1 until 4th , characterized in that the first component is a piston (52) of a clutch master cylinder (51), the second component is a piston (62) of a clutch slave cylinder (61) and the two components (52, 62) are coupled to one another by a hydraulic connection therebetween are. A clutch system comprising a clutch (2), a hydraulic clutch actuation system and an electronic control unit (16), the hydraulic clutch actuation system comprising a master cylinder (51) with a master cylinder piston (52), a slave cylinder (61) with a slave cylinder piston (62), a hydraulic connection which connects the master cylinder (51) with the slave cylinder (61), a first position sensor (53) for measuring the position of the master cylinder piston (52) and for supplying a signal indicating the measurement to the electronic control unit (16), a second Position sensor (63) for measuring the position of the slave cylinder piston (62) and for supplying a signal indicating the measurement to the electronic control unit (16), characterized in that the electronic control unit (16) can be operated in such a way that it is the measured position of the master cylinder piston (52) is used to predict the position of the slave cylinder piston s (62) to generate the measured position of the slave cylinder (51), which is derived from the output of the second sensor (63), compares with the predicted position of the slave cylinder piston (62) and the result of this comparison as an indication of the correctness the output of the second position sensor (63) is used, wherein the electronic control unit (16) can still be operated to determine at least one temperature and adjust the predicted position of the slave cylinder (61) based on the measured temperature. Coupling system according to Claim 6 , characterized in that if the position of the slave cylinder piston (62) derived from the output of the second sensor (63) falls within predetermined tolerance bands of the predicted position, the electronic control unit (16) can be operated in such a way that it receives the output from the second position sensor ( 63) validated as reliable. Coupling system according to Claim 6 or 7th , characterized in that if the position of the slave cylinder piston (62) derived from the output of the second sensor (63) falls outside of predetermined tolerance bands of the predicted position of the slave cylinder piston (62), the electronic control unit (16) can be operated in such a way that it outputs of the second position sensor (63) validated as unreliable. Coupling system according to Claim 7 or 8th , characterized in that the electronic control device (16) can still be operated to adjust the tolerance bands on the basis of the measured temperature.

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