FR2942608A1 - Hill-start assisting device for motor vehicle, has corrective unit replacing prerecorded sets by other prerecorded sets of reference zones when three among former prerecorded sets are situated outside of three among zones - Google Patents

Abstract

The device has a logic controller controlling a park brake system and actuating unlocking of a locked wheel of a motor vehicle when estimated torque attains a predetermined value. A corrective unit compares prerecorded position/torque sets (P1-P6) with corresponding reference zones (141-146). The corrective unit replaces three among prerecorded position/torque sets (P4-P6) by other prerecorded position/torque sets (P'4-P'6) of three among reference zones (144-146) when the three prerecorded position/torque sets are situated outside of the three reference zones. An independent claim is also included for a method for assisting hill-start of a motor vehicle.

Description

The present invention relates to a device for assisting the starting on a hill of a motor vehicle. It also relates to a method using the device. There is known a manual braking device, called handbrake or parking brake. Such a device makes it possible to ensure mechanically, without external energy supply, that the vehicle is kept in the idle state, even if it undergoes moderate actions intended to set it in motion. In addition, the manual braking device keeps the vehicle in a ramp during a shift gearbox, without the vehicle down, since usually a shift gear ratio is preceded by a disengagement of the motive power which is disconnected from the wheels, leaving the vehicle under the action of the gravity and the inertia of the ramp. In such a so-called hill start maneuver or in similar driving situations, the driver, whose two feet are busy simultaneously operating the clutch pedal and the accelerator pedal, must both hold the vehicle at the same time. stopping on a hill, changing the speed ratio on the gearbox, and balancing the vehicle's re-start against the effect of gravity on the boom. The use of an electric braking device makes it possible to automate this task. The electric parking brake is associated with a computer that allows, according to various operating signals of the vehicle, to achieve the automatic release of the brake without direct intervention of the driver. The document FR 2 828 450 thus describes a hill start assist device which releases the brake when the torque transmitted by the motor to the drive wheels is sufficient to compensate for the effect of the slope. The torque transmitted is estimated from the degree of depression of the clutch pedal.

This estimation is generally carried out using pre-recorded reference data associating with each position of the pedal a corresponding torque value, these data constituting a clutch curve. This data can for example be recorded in a read-only memory, then be updated and copied into a random access memory before being transferred to the computer. A problem that may arise is that the data may be incorrectly recorded, or misread. One can also be faced with problems of corruption or improper calibration of the ROM and / or RAM, such as a segmentation error. These problems can affect the performance of the Hill Start Assist, or even make it impossible to release the Brake Assist during start-up. An erroneous clutch curve can in particular generate a brake release control very late.

The present invention aims to remedy these disadvantages. The subject of the invention is thus a device for assisting the start-up of a motor vehicle equipped with a motor transmitting a torque to driving wheels and a clutch pedal for coupling the motor to the drive wheels. the device comprising: a brake capable of locking and unlocking at least one wheel of the vehicle; means for measuring the position of the clutch pedal; means for estimating the torque transmitted to the driving wheels of the vehicle; according to the measured position of the clutch pedal, using prerecorded position / torque assemblies associating at each position of the pedal a corresponding torque value, - a brake control means capable of actuating the unlocking the wheel or wheels locked when the estimated torque reaches a predetermined value. The device according to the invention further comprises a corrective means capable of comparing each set of prerecorded position / torque with a reference zone, said corrective means being furthermore capable if the position / torque combination is outside the zone. reference, to replace the set position / torque by a set position / torque belonging to the reference area. Thus, in the event of a problem of recording or reading the pre-recorded reference data, the corrective means makes it possible to replace the erroneous data with reference data enabling a correct estimation of the torque transmitted by the motor to the drive wheels. Preferably, a reference zone is associated with each position / torque combination, which makes it possible to obtain a particularly precise correction. In this case, the corrective means is able to compare each set position / torque with its associated reference area, said corrective means being further able, if the set position / torque is outside its associated reference area, to replace the position / torque combination with a position / torque set 25 belonging to its associated reference area. The position / torque assembly replacing the position / torque assembly situated outside its associated reference zone is advantageously the position / torque assembly closest to the position / torque assembly located outside its associated reference zone 30. .

The reference zone may be an area comprising position / position torque assemblies between a predetermined minimum position value and a predetermined maximum position value, and a torque between a predetermined minimum torque value and a predetermined maximum torque value. . The device may comprise a read-only memory in which the position / torque assemblies associating at each position of the pedal a corresponding torque value, an update module able to update the position / torque sets stored in the read-only memory. means for storing the updated position / torque sets in the read-only memory and in a random access memory, as well as a control module using the position / torque sets stored in the random access memory for controlling the brake. The corrective means is advantageously able to act on the position / torque sets read in the read-only memory and on the position / torque sets read in the random access memory. The corrective means may also be able to act on the position / torque sets updated by the update module. The subject of the invention is also a method of assisting the starting of a motor vehicle with a motor transmitting a torque to driving wheels, a clutch pedal enabling the motor to be coupled to the drive wheels, and a brake capable of locking and unlocking at least one wheel of the vehicle, the method comprising: a step of measuring the position of the clutch pedal; a step of estimating the torque transmitted to the driving wheels of the vehicle; according to the measured position of the clutch pedal, using prerecorded position / torque assemblies associating at each position of the pedal a corresponding torque value, - a brake control step, able to actuate the unlocking of the locked wheel (s) when the estimated torque reaches a predetermined value. The method according to the invention further comprises at least one corrective phase, that is to say: a step of comparing each prerecorded position / torque combination with a reference zone, and 10 - if the position / torque is outside the reference area, a step of replacing the position / torque combination by a set position / torque belonging to the reference area. Preferably, a reference zone is associated with each position / torque combination and, if the position / torque combination is outside its associated reference zone, the replacement step advantageously consists of replacing the position / torque combination. torque by a set position / torque belonging to its associated reference area. Other objects, features and advantages of the invention will become apparent on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings, in which: FIG. FIG. 2 shows a clutch curve, and FIG. 3 illustrates in the form of a block diagram a part of an assistance device. at the coast start according to the state of the art, - Figure 4 illustrates in block diagram form a part of a hill start assist device according to the invention, - Figures 5 and 6 illustrate a implementation of the device according to the invention. The device 1, as illustrated in FIG. 1, comprises a computer 2, a slope sensor 3, parking brakes 4 electrically controlled by the computer 2, a sensor 5 making it possible to inform the computer 2 of a request tightening / loosening of the brakes 4, and a sensor 6 of the position of the clutch pedal. The computer 2 is connected to the rest of the vehicle 7 via a connection 8 CAN bus type (Controller Area Network in English) or wired. The remainder 7 of the vehicle comprises conventional members such as the engine or the gearbox, and transmits various parameters of the vehicle to the computer 2, such as, for example, the engine speed, the speed of the vehicle, or the position of the accelerator pedal. .

The torque transmitted by the engine to the driving wheels is estimated according to the position of the clutch pedal. Figure 2 shows an example of a clutch curve representing the torque transmitted by the engine to the driving wheels as a function of the position of the clutch pedal. The curve comprises six points referenced P1 to P6, corresponding to six positions of the clutch pedal. A state-of-the-art hill start aid algorithm, housed in the computer, is illustrated in FIG. 3. The reference data associating with each position of the pedal a corresponding torque value constituting the curve of The clutch illustrated in FIG. 2 are prerecorded in a read-only memory 9. The reference data are thus the coordinates (abscissa and ordinate) of the points P1 to P6 of the curve of FIG. 2. The read-only memory 9 is typically an EEPROM memory. (for Electrically-Erasable Programmable Read-Only Memory in English, or electrically erasable and programmable 6 read-only memory). When the computer is put into operation, the clutch curve is read in the read-only memory 9. During the driving of the vehicle, the clutch curve is then updated with the aid of a module 10 for setting the clutch. day. The update module 10 can for example calculate the update according to the wear of the vehicle. Indeed, the clutch curve changes over time, with the wear of the friction plate lining and the wear of the pressure springs. The clutch curve thus updated is written in read-only memory 9 when the computer is put on standby. It is also written in a RAM 11 during the driving of the vehicle. RAM 11 is typically Random Access Memory (RAM). The clutch curve is then read in the RAM 11 and then transferred to a control module 12 able to decide the appropriate time to send the parking brake release command. Following operation of an erroneous clutch curve, the control module 12 can generate a release control 20 of parking brakes very late. To remedy this, we implement the algorithm according to the invention, as shown in Figure 4, in which the elements identical to those of Figure 3 bear the same references. According to the invention, at least one corrective phase 13 is employed. The corrective phase 13 consists of comparing the data of the clutch curve with reference data, and if data of the clutch curve differ from these data. reference data, to replace them with values in accordance with the reference data. The corrective phase 13 will be described in more detail below.

The reference data are advantageously recorded in a ROM (Read Only Memory in English), not shown. The algorithm preferably implements at least two corrective phases 13. A first corrective phase 13 is implemented during the reading of the clutch curve stored in the read-only memory 9, before updating the curve by the module 10 update. A second corrective phase 13 is advantageously implemented during the reading of the clutch curve stored in the random access memory 11, before the transfer of the curve to the control module 12. The algorithm can also comprise two other phases. corrective 13. A first corrective phase 13 can thus be implemented after the updating of the clutch curve by the update module 10 and before it is written in the read-only memory 9. A second corrective phase 13 can be implementation after updating the clutch curve by the update module 10 and before writing the clutch curve in the random access memory 11. In accordance with the method of the invention, each set of positions / couple is compared to a set of reference areas. To determine the reference areas, it is possible to associate with each point Pi of the clutch curve a reference zone surrounding the point Pi, for example an area centered on Pi. As illustrated in FIG. 5, a reference zone 14 associated with a point Pi of the clutch curve may be a rectangular surface comprising position / position torque sets between a predetermined minimum value of position PipoSMin and a predetermined maximum value of position PiPoSMaX, and of torque between a value predetermined minimum torque PicoupleMin and a predetermined maximum value of torque Picoup, eMax.

Although the illustrated reference zone 14 is rectangular in shape, it can also be imagined that the reference zone 14 is a square, a disk or any other surface centered on the point Pi. The corrective phase is more particularly illustrated in FIG. , which shows a clutch curve comprising 6 points referenced P1 to P6. At each point P1 to P6 is associated a reference zone 141 to 146 predefined by a debugging device. For effective hill start assistance, each point P1 to P6 of the clutch curve must be located in its associated reference area. The points P1 to P3 are located in their associated reference area 141 to 143 respectively. The points P4 to P6, on the other hand, lie outside their associated reference zone 144 to 146 respectively. The method according to the invention then implements a step of replacing the fault point by a point belonging to the reference zone associated with the point in default. The point P4 is outside the zone 144. P4 has an ordinate in accordance with those of the zone 144, but has a lower abscissa than the authorized values. The point P4 is then replaced by the point P'4 which is the point of the zone 144 closest to P4, that is to say of the same ordinate and of the smallest abscissa of the zone 144. The point P5 is located outside the area 145 and above it. P5 therefore has an abscissa according to those of zone 145, but has an ordinate greater than the authorized values. The point P5 is then replaced by the point P'5 which is the point of the zone 145 closest to P5, that is to say of the same abscissa and the highest ordinate of the zone 145. Finally, the point P6 is outside the zone 146, above and to the right of it, which means that P6 has an abscissa and an ordinate greater than the authorized values. The point P6 is then replaced by the point P'6 which is the point of the zone 146 closest to P6, that is to say the point of the highest abscissa and ordinate of the zone 146. Thus, thanks to the device and to the method according to the invention, it is imposed on the clutch curve, during the reading and writing of the RAM and dead memories, to belong, even in the event of memory corruption, to predetermined safety zones. This ensures reliable operation of the clutch curve and hill start assist performance that is acceptable throughout the life of the vehicle.

Claims (9)

REVENDICATIONS1. Device (1) for assisting the start-up of a motor vehicle equipped with a motor transmitting a torque to driving wheels and a clutch pedal for coupling the motor to the drive wheels, the device (1) comprising: - a brake (4) adapted to lock and unlock at least one wheel of the vehicle, - a measuring means (6) of the position of the clutch pedal, - a torque estimation means transmitted to the driving wheels of the vehicle according to the measured position of the clutch pedal, using prerecorded position / torque assemblies associating at each position of the pedal a corresponding torque value, - a means (2) for controlling the brake ( 4), able to actuate the unlocking of the locked wheel or wheels when the estimated torque reaches a predetermined value, characterized in that the device (1) further comprises a corrective means able to compare each prerecorded position / torque set to a zone reference nce (14), said corrective means being further adapted, if the position / torque assembly is outside the reference zone (14), to replace the position / torque combination with a position / torque assembly belonging to the reference area (14). 2. Device (1) according to claim 1, characterized in that a reference zone (14) is associated with each set position / torque, and in that the corrective means is able to compare each set position / torque to its associated reference zone (14), said corrective means being further adapted, if the position / torque combination is outside its associated reference zone (14), to replace the position / torque combination with a position / torque belonging to its associated reference area (14). 3. Device (1) according to claim 2, characterized in that the position / torque assembly replacing the position / torque assembly located outside its associated reference zone (14) is the closest position / torque combination the position / torque set located outside its associated reference area (14). 4. Device (1) according to one of claims 1 to 3, characterized in that the reference zone (14) is an area comprising position / position torque sets between a predetermined minimum position value (PiposMin) and a predetermined maximum value of position (PiposMax), and a torque between a predetermined minimum torque value (PiCoupleMin) and a predetermined maximum torque value (PiCoupleMin) 5. Device (1) according to one of claims 1 to 4, characterized in that it comprises a read-only memory (9) in which are recorded the position / torque assemblies associating at each position of the pedal a corresponding torque value , an updating module (10) able to update the position / torque sets stored in the read-only memory (9), means for storing the updated position / torque sets, in the read-only memory (9) and in a RAM (11), as well as a control module (12) using the position / torque sets stored in the RAM (11) for controlling the brake (4). 6. Device (1) according to claim 5, characterized in that the corrective means is able to act on the position / torque sets read in the ROM (9) and the position / torque sets read in the random access memory (11). ). 7. Device (1) according to claim 6, characterized in that the corrective means is further adapted to act on the position / torque sets updated by the module (10) update. 8. A method for assisting a motor vehicle with a motor transmitting torque to driving wheels, a clutch pedal for coupling the motor to the driving wheels, and a brake ( 4) capable of locking and unlocking at least one wheel of the vehicle, the method comprising: a step of measuring the position of the clutch pedal; a step of estimating the torque transmitted to the driving wheels of the vehicle as a function of the measured position of the clutch pedal, using prerecorded position / torque assemblies associating with each position of the pedal a corresponding torque value, - a brake control step, able to actuate the unlocking of the or locked wheels when the estimated torque reaches a predetermined value, characterized in that the method further comprises: - a step of comparing each prerecorded position / torque set to a reference area (14), and - if the nsemble position / torque is outside the reference area (14), a step of replacing the position / torque combination by a set position / torque belonging to the reference area (14). 9. Method according to claim 8, characterized in that a reference zone (14) is associated with each position / torque combination and in that, if the position / torque combination is outside its associated reference zone. (14), the replacement step is to replace the position / torque combination with a position / torque set belonging to its associated reference area (14).