FR2867736A1 - Windshield wiper blade`s movement detecting method for motor vehicle, involves determining minimum/maximum current intensity corresponding to movement of blade in end/middle positions, from current intensity measured by sensor - Google Patents

Abstract

The method involves measuring intensity of supply current of a motor driving a wiper blade, using a current sensor. A minimum and/or maximum of intensity of the supply current is determined from the measured intensity, where the minimum intensity corresponds to movement of the blade in one of two end positions of its movement and the maximum intensity corresponds to the movement of the blade in a middle position. Independent claims are also included for the following: (A) a method of automatically detecting a fault in the detection of movement of a windshield wiper blade of a motor vehicle (B) a method of controlling movement of the windshield wiper blade towards its rest position (C) a data storage medium having instructions for performing a method of detecting movement of a windshield wiper blade (D) a control unit for controlling a wiper blade movement device for motor vehicle.

Description

Methods of detection, control and survey

  failure of a wiper blade, a recording medium and a control unit for their implementations.

  More specifically, the invention relates to a windscreen wiper blade of a motor vehicle moved in a reciprocating movement between two extreme positions of its stroke by an electric motor powered current.

  Until now, the position of the wiper blade is detected using a detector capable of measuring the position of one of the mechanical parts used to move the blade. Typically this detector detects a particular angular position of the motor shaft which moves the blade.

  Such detectors are expensive and bulky.

  The invention aims to remedy this drawback by proposing a method for detecting the position of the wiper blade that does not require a direct measurement of the position of one of the mechanical parts used to move the wiper blade.

  The subject of the invention is therefore a detection method, characterized in that it comprises a step of recording the evolution of the intensity of the motor supply current over time, this intensity being representative of the position broom along its stroke, and a step of determining, from these readings, a minimum and / or a maximum of intensity, each minimum corresponding to the passage of the broom in one of the extreme positions of its race and each maximum corresponding to the passage of the blade in its middle position.

  In the above method, the passage of the blade in an extreme or middle position of its stroke is only detected from the information recorded by a current sensor. It is therefore no longer necessary to use known detectors capable of directly measuring the position of a mechanical part used to move the blade.

  According to other additional features taken alone or in combination, the method according to the invention is characterized in that: the determination step comprises: a construction operation of a model for predicting the evolution of the intensity of the current over time, 2867736. 2 - an operation of predicting the moment when the intensity of the current passes through a minimum and / or a maximum using the model of prediction built and the evolution of the intensity of the currently detected current, and - a step of measuring the time interval remaining before reaching this predicted instant; the determination step comprises an operation of posteriori observation of the evolution of the intensity in order to record the moment at which the intensity of the current has passed through a minimum and / or a maximum.

  The invention also relates to a method for automatically revealing a failure in the detection of the passage of a wiper blade of a motor vehicle in a rest position, this blade being moved by an electric motor in a movement back and forth and the rest position corresponding to an extreme or middle position of its stroke, characterized in that it comprises: - a first step of detecting the passage of the brush in the rest position by implementing a detecting method according to the invention, - a second step of detecting the passage of the blade in the rest position using a rest position detector, this detector being able to detect the presence of the blade in the position resting by directly raising the position of at least one mechanical part displaced by the electric motor, and - a step of indicating a failure if the information provided by the two stages of detection are not concordant.

  The invention also relates to a method for controlling the movement of a wiper blade towards its rest position, the rest position corresponding to an extreme or middle position of its stroke, this method comprising: a step control of stopping the movement of the blade when the rest position of the blade is detected, characterized in that it comprises: - a step to automatically reveal a failure in the detection of the passage of the blade in the rest position carried out at using a method according to the invention, and - if a failure is revealed, a step of controlling the stop of the movement of the blade only when the passage of the blade in the rest position is detected using of a detection method according to the invention.

  The invention also relates to an information recording medium, characterized in that it comprises instructions for the implementation of at least one of the methods according to the invention when these instructions are executed by a computer electronic.

  The invention also relates to a control unit of a device for moving a wiper blade for a motor vehicle, characterized in that this unit uses any of the methods according to the preceding characteristics.

  The invention will be better understood on reading the following description given solely by way of example and with reference to the drawings in which: FIG. 1 is a schematic illustration of the architecture of a displacement device of a wiper blade and a control unit of this device according to the invention, - Figure 2 is a flowchart of a method of detecting the passage of a wiper blade in FIG. 3 is a graph illustrating the typical evolution of the intensity of a feed current of the wiper blade moving device of FIG. 1, and Figure 4 is a flowchart of a method of controlling the movement of a wiper blade to a rest position according to the invention.

  FIG. 1 represents a windshield 2 of a motor vehicle equipped with a wiper blade 4 capable of moving between two extreme positions 6 and 8. Here the position 6 is the rest position of the blade 4 and position 8 is the wiper limit position. Given the uncertainty in the exact location of positions 6 and 8, these positions are represented here by bands. Indeed, the exact location of positions 6 and 8 depends on many parameters such as the speed of movement of the vehicle, the wind etc. To move the blade 4 between these two extreme positions, a conventional device 10 for moving the blade 4 is provided. Only the elements of this device 10 necessary for understanding the invention will be described here.

  The device 10 comprises a controllable electric motor 12 and a crank mechanism 14.

  The motor 12 is able to drive in rotation a shaft 16 mechanically coupled to an input of the mechanism 14.

  The mechanism 14 has an output coupled to the blade 4. This mechanism 14 is able to transform the rotary movement 360 of the shaft 16 into a movement back and forth of the blade 4 between the two extreme positions 6 and 8.

  The device 10 also comprises a detector 18 capable of indicating that the blade 4 is in the rest position. For this purpose, typically, the shaft 16 comprises a conductive strip for locating the rest position and the detector 18 is able to detect this conductive strip.

  The device 10 is controlled by a control unit 20. This unit 20 comprises a control output connected to the motor 12 and two data acquisition inputs respectively connected to the detector 18 and to a current sensor 24. This unit 20 is made in a conventional manner using a programmable electronic computer 26 associated with a memory 28 comprising instructions to execute. Here, the memory 28 includes the instructions necessary to carry out the methods of FIGS. 2 and 4.

  The sensor 24 is able to measure the intensity of the motor supply current 12.

  A first mode of operation of the unit 20 to detect the passage of the brush 4 in the position 8 will now be described with reference to FIG.

  When stopped, the broom 4 is in its rest position. As soon as the start of the device 10 is controlled, the unit 20 executes in parallel a motor control process 40 and a process for detecting the position of the blade 4. More precisely, in this mode of operation, the process 42 estimates the moment of passage of the blade 4 in position 8.

  The process 40 for controlling the movement of the blade in a back and forth motion between positions 6 and 8 is conventional and will not be described here.

  During the execution of the process 42, the unit 20 continuously records and records, during a step 50, the intensity of the current measured by the sensor 24 to know the evolution of the current over time. A graph 52 in FIG. 3 includes a curve 54 representing a typical example of the evolution of the intensity of this current over time. The x-axis of graph 52 is graduated in milliseconds and the y-axis is graduated in amperes. The instant 0 on the abscissa axis corresponding to the start time of the device 10.

  In parallel with step 50, the unit 20 establishes the moment at which the blade 4 leaves its rest position. For this purpose, it uses, for example, the information delivered by the detector 18.

  As soon as the brush 4 has left the rest position, at time to, the unit 20 proceeds to a step 54 for initializing a clock capable of measuring the elapsed time t from the instant to. This elapsed time is representative of the position of the blade 4 along its stroke and therefore corresponds to an estimate of the position of the blade 4.

  Then, during a step 56, the unit 20 calculates the value of a threshold SI corresponding to the average intensity of the supply current of the motor 12 when the blade 4 is in its rest position. This threshold is represented by a line S1 in FIG. 3. For this purpose, for example, the unit 20 calculates the average of the values recorded by the sensor 24 between the moment when the wiper reaches the position 6 and the instant to .

  Then, in a step 58, the unit 20 waits for a predetermined time interval éT1 to elapse before continuing the execution of the process 42. The value of the interval 6T1 is chosen so that the Broom 4 has traveled more than 50% of its stroke between positions 6 and 8. 6T1 will be, for example, equal to 700 ms.

  When the waiting step 58 is completed, the unit 20 determines in advance a time tp of passage of the blade 4 in the position 8 during a step 60. For this, the unit 20 begins by building, during an operation 62, a model for predicting the evolution of the intensity of the current. This is made possible because the evolution of the current substantially describes a parabola between two successive instants where the blade is in an extreme position of its stroke. In addition, it has been found that each minimum intensity corresponds, alternately, to the presence of the blade 4 in the position 6 or 8.

  During the operation 62, the unit 20 selects, during a sub-operation 64, four points, situated for example at regular intervals, on the curve 54 between the instant to and the current instant t. These points are represented by black dots 68 on curve 54. From these dots 68, four groups of three dots are constructed.

  Then, during a sub-operation 66, for each group of points a polynomial of degree two passing through these three points is calculated. This polynomial corresponds to the equation of a parabola.

  The unit 20 then selects, during a sub-operation 70, the polynomial constructed during the sub-operation 66 which best represents the evolution of the intensity between the times t 0 and t. For this purpose, three evaluation points are selected between the points 68. These evaluation points are represented by white points 72 on the curve 54. The difference between these evaluation points and the predicted value for these three points using each of the polynomials constructed is calculated. The polynomial selected as the prediction model is the one that makes it possible to obtain the smallest deviations from the three evaluation points chosen.

  The parabola corresponding to the polynomial thus selected is represented on the graph 52 by a portion of parabola 74.

  The fact of using four points 68 instead of the three necessary to construct a polynomial of degree 2 here makes it possible to limit the consequences due to an erroneous measurement or to an aberrant value of the intensity of the current at a given point.

  Once the prediction model is constructed, the unit 20 proceeds to an operation 76 for calculating the instant tp using this prediction model. This amounts to calculating the next instant for which curve 54 will go through a minimum. Here, the value of the instant tp is chosen equal to the instant at which the dish 74 intersects the line Si. This instant can be easily determined from the equation of the parabola 74.

  Once the value of the instant tp has been estimated in advance, the unit 20 measures, during a step 80, the time interval remaining before reaching the predicted instant tp.

  Here, this remaining time interval is measured using the clock initialized in step 54.

  A second mode of operation of the unit 20 for controlling the movement of the blade 4 towards its rest position will now be described with reference to the method of FIG. 4 in the particular case where the rest position corresponds to the position 6.

  Initially, the activation of the device 10 is controlled by the user. The unit 20 then performs in parallel a method 100 to reveal a failure of the detector 18 and a conventional method of controlling the movement of the blade 4 between the positions 6 and 8.

  In the method 100, the unit 20 executes in parallel two steps 106 and 108 for detecting the presence of the blade 4 in the rest position 6.

  In step 106, each time the detector 18 detects the presence of the blade 4 in its rest position, the instant tk where this event occurs is stored.

  During step 108, the evolution of the intensity of the current measured by the sensor 24 is recorded and recorded permanently, during an operation 110, so as to be able to reconstruct a curve of the evolution of the intensity such as the curve 54 of FIG. 3. Then, with a slight delay time with respect to the execution of the step 110, the unit 20 determines, during an operation 112, the moments when the intensity passes by a minimum using the recorded curve. For this, the unit 20 observes the evolution of the intensity and calculates using conventional methods the moment when the intensity has passed through a minimum. As indicated above, the moments when the intensity is minimal, correspond to one of the extreme positions of the stroke of the blade 4.

  In order to discriminate a moment ta when the blade 4 is in the position 6 of a time tp during which the blade 4 is in the position 8, a counter is incremented by one, during an operation 114, each time a minimum is detected. Thus, the instant ta corresponds to an even value of the counter.

  Each moment ta therefore corresponds to the moment when the presence of the blade 4 is detected in its rest position.

  Then, during a step 116, the unit 20 compares the information obtained during the steps 106 and 108. For this purpose, the unit 20 verifies that the instant tk at which the detector 18 indicates the presence of the brush 4 in the rest position is close to the moment ta. The instants tk and ta will be considered close if they are separated from each other by a pre-established time interval 3T4.

  Typically, the value of the interval 6T4 will be less than 100 ms and preferably greater than 50 ms.

  If the instants tk and ta are close, this means that the detector 18 is functioning correctly and the process returns to the steps 106 and 108. In the opposite case, the detector 18 does not operate correctly and the unit 20 proceeds to a step 120 of indication of detector failure 18.

  When the unit 20 receives a deactivation command of the device 10, the unit 20 interrupts the execution of the method 102 and proceeds to a step 130 of controlling the stop of the blade 4 in its rest position. For this purpose, the unit 20 checks, during an operation 132, the presence of a failure indication for the detector 18. If no indication of failure is present, then the unit 20 controls, when an operation 134, stopping the device 10 when the detector 18 indicates that the blade 4 is in the position 6.

  In the opposite case, the unit 20 controls, during an operation 136, the stopping of the device 10 immediately after the passage of the blade 4 has been detected during the step 108. The step 136 therefore corresponds to a degraded control mode of the device 10 stop which stops the device 10 when the blade 4 is close to the position 6.

  The process of Figure 4 has several advantages over similar known methods.

  First, the method of detecting a failure proposed here is faster and more efficient than known methods. Indeed, the known methods essentially consist in detecting a failure of the detector 18 if no passage of the blade 4 in the position 6 has been detected in a time interval greater than or equal to that required for the blade 4 to go one way. complete return between the positions 6 and 8. Here, the indication of a failure of the detector 18 can be achieved well before the blade 4 has made a complete round trip between the positions 6 and 8.

  In addition, this method makes it possible to discriminate between a failure of the detector 18 and the motor 12.

  The method of FIG. 4 also represents the advantage, compared with similar known methods, of allowing the brush 4 to stop in a position that does not disturb the driver even if the detector 18 is faulty.

  Here, the method of FIG. 4 has been described in the particular case where, during step 136, the movement of the blade 4 is stopped as soon as the instant ta of passage in the position 6 is detected from the previously recorded values. intensity. Alternatively, to stop the brush 4 with greater accuracy in the position 6, the moment ta is not determined a posteriori but a priori. For this purpose, the step 108 is for example replaced by the method of Figure 2 adapted to the case where it is the passage in the position 6 is detected.

  Advantageously, the unit 20 will implement the method of FIG. 2 only to perform the operation 136.

  In the above methods, the estimate of the position of the blade 4 is represented by the time elapsed since the last minimum intensity occurred. However, it should be noted that it is possible to calculate from the elapsed time and the speed of movement of the blade the distance that the blade has traveled since its last passage in one of its extreme positions. Therefore, it is possible to convert the value of the elapsed time into an angular position of this broom. However, in the methods described here, the use of an elapsed time as a measure of the position of the blade simplifies the process, since precisely it is not necessary to convert the time elapsed into another unit such as, for example, an angular position value. This simplification makes it possible to execute the processes described here more quickly.

  Here, the process 42 has been described in the particular case where it uses a detector 18 to record the moment of passage of the blade in the position 6. Alternatively, during the process 42, the moment when the blade 4 passes by the position 6 is also detected using the intensity of the motor supply current. Indeed, the passage of the brush 4 in the position 6 also corresponds to a minimum of intensity. In this variant, the process 42 does not require the use of a detector such as the detector 18.

  Here, the process 42 and the step 108 have been described in the particular case of detecting the extreme positions of the stroke of the blade 4. In a variant, this process and this step are adapted to detect the passage of the blade 4 in the middle of the blade. his race. Indeed, the middle of the race of the brush 4 corresponds to a maximum of the evolution of the intensity of the current over time. Therefore, in this variant, the steps of determining a minimum are replaced by steps of determining a maximum.

  Finally, it will be noted that unlike the value of the intensity of the current which depends on the type of motor and its control, the presence of an extremum in the evolution of the current does not depend on the characteristics of the motor 12. The methods described herein can be applied to different engines without the need for significant adaptation of the various parameters of these methods.

Claims (7)

  1. A method of detecting the passage of a windscreen wiper blade in an extreme or middle position of its stroke, for a wiper blade of a motor vehicle, this broom being moved in a movement of comes between these two extreme positions by an electric motor powered current, characterized in that it comprises: - a step (50) of the evolution of the intensity of a current of supply of a motor d driving the broom over time, and - a step (60) of determining, from these readings, a minimum and / or a maximum of intensity, each minimum corresponding to the passage of the broom in one of the extreme positions of its stroke and each maximum corresponding to the passage of the blade in its middle position.   2. Method according to claim 1, characterized in that the determining step (60) comprises: - an operation (62) for constructing a model for predicting the evolution of the intensity of the current over time an operation (76) for predicting the moment when the intensity of the current passes through a minimum and / or a maximum using the prediction model constructed and the evolution of the current intensity currently recorded. and a step (80) of measuring the time interval remaining before reaching this predicted instant.   3. Method according to claim 1, characterized in that the determining step (112) comprises a posteriori observation operation of the evolution of the intensity to record the moment at which the intensity of the current has passed through. a minimum and / or a maximum.   4. A method for automatically revealing a failure in detecting the passage of a wiper blade of a motor vehicle in a rest position, this broom being moved by an electric motor in a back and forth motion and the rest position corresponding to an extreme or middle position of its stroke, characterized in that it comprises: a first step (108) for detecting the passage of the blade in the rest position by implementing a method according to any one of claims 1 to 3, - a second step (106) for detecting the passage of the brush in the rest position using a rest position detector, this detector being able to detect the presence of the broom in the rest position by directly raising the position of at least one mechanical part displaced by the electric motor, and - a step (120) of indicating a failure if the information provided by the two steps of d tection are not concordant.   5. A method of controlling the movement of a wiper blade towards its rest position, the rest position corresponding to an extreme or middle position of its stroke, this method comprising: a step (130) of controlling the wiper blade; stopping the movement of the blade when the rest position of the blade is detected, characterized in that it comprises: - a step (100) to automatically reveal a failure in the detection of the passage of the blade in the rest position carried out at using a method according to claim 4, and - if a failure is revealed, a step (136) of controlling the stop of the movement of the blade only when the passage of the blade in the rest position is detected at using a process in accordance with any one of Claims 1 to 3.   6. Support (28) for recording information, characterized in that it comprises instructions for the execution of any of the methods according to claims 1 to 5, when these instructions are executed by an electronic computer.   7. Unit (20) for controlling a device for moving a wiper blade for a motor vehicle, characterized in that this unit uses any of the methods according to claims 1 to 5.