CONTROLLING A VEHICLE'S SPEED LIMITER FUNCTION DURING REVERSE MOTION

Abstract

A method is implemented in a vehicle comprising wheels, a powertrain providing torque to at least two drive wheels, and a speed limiting function designed to prevent the vehicle from moving in reverse at a speed exceeding the absolute value of a first chosen threshold. This method includes a step (10-30) in which, when a slippage situation involving at least one drive wheel is detected, the first threshold is replaced by a second chosen threshold having an absolute value greater than the absolute value of the first threshold. Figure 3

Description

Title of the invention: CONTROL OF A VEHICLE'S SPEED LIMITING FUNCTION DURING REVERSE MOTION Technical field of the invention

[0001] The invention relates to vehicles comprising at least two drive wheels and a speed limiting function, and more specifically the control of this speed limiting function during reverse gear. State of the art

[0002] Some wheeled vehicles (generally of the automobile type) include a powertrain (or PWM) capable of providing torque for at least two drive wheels of a drive train, and a speed limiting function (or VLS (“Vehicle Speed ​​Limiter” - safety function)).

[0003] In some of the vehicles described above, the speed limiter function is arranged to prevent the vehicle from reversing at a speed exceeding a chosen threshold. This limiter is intended to allow the driver to control the vehicle's trajectory when reversing. For example, this threshold may be -30 km / h (in which case the vehicle is prevented from reversing at more than 30 km / h).

[0004] However, such a restriction can pose a problem in certain situations during a vehicle's operation.

[0005] Indeed, when the vehicle is reversing on a surface covered with mud or snow, the speed restriction in reverse generally does not allow the drive wheels to reach a sufficient rotational speed to evacuate the mud or snow trapped in the tire treads, and therefore the vehicle can become immobilized.

[0006] Similarly, when the vehicle is reversing on a surface that does not offer the same grip to its right wheels as to its left wheels, the speeds of the right and left drive wheels of the same drive axle can be very different. For example, when grip is lower on the right wheel of an axle, the differential associated with that axle will send all the power of the powertrain to the right wheel, and therefore the left wheel will not turn, or will turn very little. However, since the speed regulation (imposed by the speed limiter) is based on the average speed of the drive wheels, the vehicle's actual speed remains low and can prevent it from moving because the left drive wheel has zero speed and the right drive wheel has a speed equal to twice the regulated speed.

[0007] The invention therefore aims in particular to improve the situation. Presentation of the invention

[0008] In particular, it proposes for this purpose a control method intended to be implemented in a vehicle comprising wheels, a powertrain (or PMT) capable of providing torque for at least two drive wheels, and a speed limiting function capable of preventing the vehicle from moving in reverse at a speed having an absolute value greater than an absolute value of a first chosen threshold.

[0009] This control method is characterized by the fact that it includes a step in which, when a situation of slippage of at least one drive wheel is detected, the first threshold is replaced by a second threshold chosen and having an absolute value greater than the absolute value of the first threshold.

[0010] Thanks to the invention, after the establishment of the second threshold the drive wheels can turn fast enough to allow the vehicle to move, and therefore the latter is no longer at risk of being immobilized, which is likely to satisfy its driver and to strengthen the safety of the vehicle and its passengers.

[0011] The control method according to the invention may include other features which may be taken separately or in combination, and in particular:

[0012] - in its step, the sliding situation can be detected by performing an action which is chosen from an analysis of information sent by a vehicle trajectory control function, a comparison of ongoing wheel rotation speeds, and comparisons of wheel speed gradients at a third threshold;

[0013] - in its step, the first threshold can be replaced by the second threshold when the a slippage situation is detected for at least a first chosen duration;

[0014] - in its step, the first threshold can be replaced by the second threshold in progressively decreasing the signed value of the first threshold (or increasing its absolute value) until reaching the second threshold;

[0015] - in its stage, when the sliding situation is no longer detected after the after replacing the first threshold, we can continue to use the second threshold for a second chosen duration, and after this second duration has elapsed we can replace the second threshold with the first threshold;

[0016] - in its stage, when an absolute value of a current speed of the vehicle is greater than the absolute value of the second threshold while using this second threshold, the second threshold can be replaced by the first threshold;

[0017] - in the presence of one of the last two options, in its step, one can replace the second threshold by the first threshold by progressively increasing the signed value of the second threshold (or by increasing its absolute value) until reaching the first threshold.

[0018] The invention also proposes a computer program product comprising a set of instructions which, when executed by processing means, is proper to implement a control method of the type presented above, in a vehicle comprising wheels, a powertrain (or PWM) capable of providing torque for at least two drive wheels, and a speed limiting function capable of preventing the vehicle from moving in reverse at a speed having an absolute value greater than an absolute value of a first chosen threshold, to control the speed limiting function in the presence of a situation of slippage of at least one drive wheel.

[0019] The invention also proposes a control device intended to equip a vehicle comprising wheels, a powertrain (or PWM) capable of providing torque for at least two drive wheels, and a speed limiting function capable of preventing the vehicle from moving in reverse at a speed having an absolute value greater than an absolute value of a first chosen threshold.

[0020] This control device is characterized by the fact that it includes at least one processor and at least one memory arranged to perform the operations consisting, when a situation of slippage of at least one drive wheel is detected, of triggering a replacement of the first threshold by a second threshold chosen and having an absolute value greater than the absolute value of the first threshold.

[0021] The invention also proposes a vehicle, possibly of the automobile type, comprising:

[0022] - wheels (of which at least two are drive wheels),

[0023] - a powertrain (or powertrain) capable of providing torque for at least two-wheel drive,

[0024] - a speed limiting function designed to prevent the vehicle from moving in reversing at a speed whose absolute value is greater than the absolute value of a first chosen threshold, and

[0025] - a control device of the type presented above. Brief description of the figures

[0026] Other features and advantages of the invention will become apparent from an examination of the detailed description below, and the accompanying drawings, in which:

[0027] [Fig. 1] schematically and functionally illustrates an example of an embodiment of a vehicle comprising a control device according to the invention, a computer controlling a speed limiting function, and a purely electric powertrain associated with a supervisory computer,

[0028] [Fig.2] schematically and functionally illustrates an example of an embodiment of a speed limiting function calculator comprising an example of an embodiment of a control device according to the invention, and

[0029] [Fig.3] schematically illustrates an example of an algorithm implementing a control method according to the invention. Detailed description of the invention

[0030] The invention aims in particular to provide a control method, and an associated DC control device, intended to enable the control of a speed limiting function of a wheeled vehicle V, when the latter (V) is moving (or rolling) in reverse.

[0031] In what follows, vehicle V is considered, by way of non-limiting example, to be of the automobile type. For example, it is a car, as illustrated in [Fig. 1]. However, the invention is not limited to this type of wheeled vehicle. It relates in fact to any type of vehicle comprising wheels (of which at least two are driven), a powertrain (or powertrain) capable of supplying engine torque to at least one set of driven wheels, and a speed limiting function.

[0032] Furthermore, in what follows, by way of non-limiting example, the powertrain is considered to be purely electric (and therefore includes at least one electric drive machine). However, the powertrain could be hybrid (for example, thermal and electric).

[0033] Furthermore, in the following, by way of non-limiting example, the electric powertrain comprises a single electric drive machine MME supplied with electrical energy by an electrical power source BP constituting a power (or "main" or "traction") battery, rechargeable (at least during charging phases). However, each electric drive machine MME could be supplied with electrical energy by a fuel cell (for example, a hydrogen fuel cell).

[0034] Finally, in what follows, by way of non-limiting example, we consider that the electric drive machine MME is associated with a single set of driven wheels Tl, and therefore the transmission chain only allows a two-wheel drive mode (traction or propulsion). However, the transmission chain could include two sets of driven wheels Tl to allow a four-wheel drive (or 4x4) mode.

[0035] A vehicle (with wheels) V comprising a DC control device according to the invention and a purely electric GMP transmission chain (and therefore comprising (here) a single electric motor machine MME), an on-board network RB, a service battery BS, an electrical power supply source (here a power (or main or traction) battery) BP, a CV converter, a CS supervisory computer, and a CM machine computer is schematically represented in [Fig.1].

[0036] The CV converter is of the DC / DC type (“Direct Current / Direct Current”). It is therefore responsible for converting a direct current from a first voltage to a second voltage.

[0037] The RB on-board network is an electrical power supply network to which electrical (or electronic) equipment (or components) that consume electrical energy are coupled.

[0038] The auxiliary battery BS is responsible for supplying electrical power to the vehicle's electrical system RB, supplementing, in this case, that supplied by the converter CV, which is powered by the power supply BP via a power grid, and sometimes replacing, in this case, the converter CV. For example, this auxiliary battery BS can be configured as a very low voltage type battery (typically 12 V, 24 V, or 48 V). It is rechargeable at least by the converter (current) CV. In the following, by way of non-limiting example, the auxiliary battery BS is considered to be a 12 V lithium-ion type.

[0039] The transmission chain has a GMP which is, here, purely electric and therefore includes, in particular, an electric drive machine MME, a drive shaft AM, and a transmission shaft AT.

[0040] Here, "electric drive machine" means an electric machine arranged to provide a motor torque, defined by a torque setpoint, to move the vehicle V when it is supplied with electrical energy (here) by the electrical power supply BP (this is referred to as supplying a positive output torque), and possibly to recover regenerative braking torque to decelerate the vehicle V (this is referred to as supplying a negative output torque).

[0041] The operation of the powertrain is supervised by a supervisory control unit (CS). The control of the electric drive unit (MME) is ensured by the machine control unit (CM), notably based on a setpoint provided by the supervisory control unit (CS) defining the motor torque that the latter (CS) wants the electric drive unit to deliver. It should be noted that the machine control unit (CM) and the supervisory control unit (CS) communicate with each other, for example via a vehicle communication network (V), possibly multiplexed.

[0042] The electric drive machine MME is coupled to the motor shaft AM to provide it with motor torque by rotational drive when it is (here) supplied with electrical energy by the power supply BP via the power grid. This motor shaft AM is coupled to a reduction gear RD, which is also coupled to the drive shaft AT, itself coupled to a first set of wheels Tl. Here, the first set Tl is associated with the electric drive machine MME and therefore comprises right-hand drive wheels R1D and left-hand drive wheels R1G, and it is preferably coupled to the drive shaft AT via a differential DV.

[0043] It should be noted that the first train Tl (here, the motor) is located in the front PVV section of the vehicle V, and is therefore referred to hereafter as the front train. However, in a variant, this first train Tl could be the second train T2, which is located in the rear PRV section of the vehicle V.

[0044] Here, the second train T2 (rear) is not associated with a driving machine and is therefore not driven. It comprises non-driving wheels right R2D and left R2G.

[0045] The power supply BP is here a power (or main or traction) battery which may, for example, include electrical energy storage cells, possibly electrochemical (for example, lithium-ion (or Li-ion) or Ni-MH or Ni-Cd type). Also, for example, the power supply BP may be of the low voltage type (typically 450 V or 600 V by way of illustration). But it could also be of the medium voltage or high voltage type.

[0046] The CV converter is also responsible, here, during the driving phases of the vehicle V, for converting part of the electrical current stored in the electrical power supply BP to supply converted electrical current to the on-board network RB and the auxiliary battery BS (to recharge it).

[0047] It will be noted, as illustrated non-limitingly in [Fig.1], that the CV converter can be part of a CH charger responsible for controlling the recharging of the BP power supply source.

[0048] It should also be noted that in the example illustrated, but not limited to, in [Fig. 1], the vehicle V also includes a distribution box BD to which the auxiliary battery BS, the converter CV, and the on-board network RB are coupled. This distribution box BD is responsible for distributing the electrical energy stored in the auxiliary battery BS or produced by the converter CV into the on-board network RB to power the electrical components (or equipment) connected to the on-board network RB, according to power demands received (in particular from the powertrain control unit CS).

[0049] The vehicle V also includes a safety function for speed limiting (or SVL) arranged to prevent it from moving (or rolling) in reverse at a speed which has an absolute value greater than the absolute value of a first threshold s1 chosen, and which can be replaced by a second threshold s2 as will be seen later.

[0050] For example, and as illustrated, but not limited to, in [Fig. 1], this speed limiting function can be controlled by a dedicated CFB computer. However, this speed limiting function could also be controlled by another computer on board the vehicle V, such as, for example, the CS monitoring computer. or a computer providing at least one driver assistance function (or AD AS (“Advanced Driver Assistance System”)).

[0051] Also, for example, and as illustrated, but not limited to, in [Fig. 1], the vehicle V may also include a trajectory control function (of the ADAS type), for example, of the ESP (“Electronic Stability Program”) or ESC (“Electronic Stability Control”) type. This trajectory control function is responsible for controlling the trajectory of the vehicle V by acting on its braking system and possibly on the engine power supplied by the powertrain. Furthermore, this trajectory control function is controlled by a dedicated CCT computer.

[0052] As mentioned above, the invention proposes in particular a control method intended to allow control of the speed limiting function when the vehicle V is moving (or driving) in reverse.

[0053] This (control) method can be implemented at least partially by the DC control device (illustrated at least partially in Figures 1 and 2), which for this purpose comprises at least one PR1 processor, for example a digital signal processor (or DSP), and at least one MD memory. This DC control device can therefore be implemented as a combination of electrical or electronic circuits or components (or "hardware") and software modules (or "software"). For example, it could be a microcontroller.

[0054] The MD memory is random access memory (RAM) to store instructions for the implementation by the PR1 processor of at least part of the control process. The PR1 processor may comprise integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or wireless connections. An integrated (or printed) circuit is defined as any type of device capable of performing at least one electrical or electronic operation.

[0055] In the example illustrated, but not limited to, in Figures 1 and 2, the DC control device is part of the CFB function controller. However, this is not mandatory. The DC control device could comprise its own dedicated controller, or it could be part of another controller installed in the vehicle V and performing at least one other function, such as the CS monitoring controller.

[0056] As illustrated non-limitingly in [Fig.3], the (control) method according to the invention includes a step 10-30 which is implemented each time the vehicle travels (or moves) in reverse.

[0057] Step 10-30 of the method includes a substep 20 in which, when a slippage situation of at least one drive wheel Tl is detected, the first wheel is replaced (for example, the DC control device triggers a replacement of the first wheel). threshold if by a second threshold s2 chosen and having an absolute value greater than the absolute value of the first threshold if.

[0058] It is important to note that the first si and second s2 thresholds have negative values ​​because they correspond to reverse speeds. Therefore, the absolute value Is2l of the second s2 threshold is greater than the absolute value Is11 of the first si threshold, but the second s2 threshold is less than the first si threshold (i.e., si > s2, but Is11 < Is2l).

[0059] Thus, thanks to this temporary replacement of the first threshold si by the second threshold s2, the drive wheels (here R1D and R1G) can rotate fast enough to allow the vehicle V to move. In particular, they can rotate fast enough to clear mud or snow trapped in the treads of their tires in order to regain traction. In other words, the vehicle V is no longer at risk of becoming immobilized, which is likely to satisfy its driver and enhance the safety of the vehicle and its passengers.

[0060] For example, the first threshold si can be between -20 km / h and -40 km / h. As an illustrative example, the first threshold si can be equal to -30 km / h. However, other values ​​for the first threshold si can be used. For example, this first threshold si can be chosen during the development or testing phase of a vehicle similar to vehicle V.

[0061] Also, for example, the second threshold s2 can be between -50 km / h and -70 km / h. As an illustrative example, the second threshold s2 can be equal to -60 km / h. But other values ​​for the second threshold s2 can be used. For example, this second threshold s2 can be chosen during the development or testing phase of a vehicle similar to vehicle V.

[0062] Also, for example, step 10-30 of the process may also include a substep 10 in which one (for example, the DC control device) can detect the slipping situation by performing an action chosen from:

[0063] - an analysis of information sent by the trajectory control function of the vehicle V, and more specifically here by the CCT computer,

[0064] - a comparison of the rotational speeds of wheels R1D, R1G, R2D and R2G during the process of vehicle V (here, driven and non-driven), and

[0065] - comparisons of the velocity gradients of wheels R1D, R1G, R2D and R2G at a third threshold.

[0066] Also, for example, the analysis of information may be intended to determine which information is representative of ongoing regulation carried out by the trajectory control computer CCT, and therefore indicates that a slip situation has been detected and is being processed.

[0067] It will be understood that by comparing the rotational speeds of the wheels R1D, R1G, R2D and R2G it is possible to know if one of them has a speed significantly higher than those of the other wheels and therefore characteristic of a sliding motion.

[0068] It will also be understood that if the velocity gradient of a wheel is greater than a third threshold, this is characteristic of a slip in progress of this wheel.

[0069] Furthermore, it should be noted that the aforementioned list of three possibilities for detecting a slip situation is neither limiting nor exhaustive.

[0070] Also, for example, in substep 20 of step 10-30, the control device (e.g., the DC control device) can replace the first threshold si with the second threshold s2 when a slip condition is detected for at least a first chosen duration dl. This option is intended to avoid replacing the first threshold si with the second threshold s2 when the slip condition is very short or because a value of a parameter used during detection is abnormal for a very short time. In other words, this option allows confirmation of actual wheel slippage.

[0071] Also, for example, the first duration dl can be between 300 ms and 800 ms. As an illustrative example, the first duration dl can be equal to 500 ms. But other values ​​for the first duration dl can be used. For example, this first duration dl can be chosen during the development or testing phase of a vehicle similar to vehicle V.

[0072] Also, for example, in substep 20 of step 10-30, the first threshold si can be replaced by the second threshold s2 by progressively decreasing the first threshold si until the second threshold s2 is reached (or by increasing the absolute value of the first threshold si until the absolute value of the second threshold s2 is reached). As an illustrative example, this decrease (or increase in absolute value) can be linear. This option is intended to prevent a sudden change in the vehicle's behavior. For example, in the event of a sudden wheel slippage, the wheel rotation speed should not be allowed to increase too suddenly so as not to startle the driver.

[0073] It should also be noted that step 10-30 may include, as illustrated non-limitingly in [Fig. 3], a substep 30 in which, when the slip situation is no longer detected after the replacement of the first threshold si, one (for example, the DC control device) may continue to use the second threshold s2 for a second chosen duration d2, and after the elapse of this second duration d2, one (for example, the DC control device) may replace the second threshold s2 with the first threshold si. This option is intended to avoid returning to the initial situation (with the first threshold if) while a new slip situation reappears rapidly after the end of detection of the previous slip situation.

[0074] Also, for example, the second duration d2 can be between 500 ms and 2 s. As an illustrative example, the second duration d2 can be equal to 1 s. However, other values ​​for the second duration d2 can be used. For example, this second duration d2 can be chosen during the development or testing phase of a vehicle similar to vehicle V.

[0075] Also, for example, in substep 20 of step 10-30, when the absolute value of the current speed of vehicle V is greater than the absolute value of the second threshold s2 while this second threshold s2 is in use, the second threshold s2 can be replaced by the first threshold s2 (for example, by the DC control device). It will be understood that the second threshold s2 should no longer be used for limiting the speed of vehicle V when its current speed (V) in reverse becomes too high. Furthermore, it should be noted that the current speed of vehicle V can be determined by any technique known to those skilled in the art, and in particular by measurements on the non-drive wheels (here R2D and R2G).

[0076] Also, for example, in substep 20 or 30 of step 10-30, the second threshold s2 (for example, the DC control device) can be replaced by the first threshold si by progressively increasing the second threshold s2 until it reaches the first threshold si (or by decreasing the absolute value of the second threshold s2 until it reaches the absolute value of the first threshold si). As an illustrative example, this increase (or decrease in absolute value) can be linear. This option is intended to avoid a sudden change in the behavior of vehicle V. For example, when returning to a surface with better traction, the drive wheels (here R1D and R1G) should not be slowed down too quickly so as not to surprise the driver or risk causing wheel slippage.

[0077] It will also be noted, as illustrated non-limitingly in [Fig.2], that the computer of the CFB bridle function (or the computer of the DC control device) may also include a mass memory MM1, in particular to store at least the information representative of a slip situation, the information representative of an end of a slip situation, and the possible current speed of the vehicle V, as well as any intermediate data involved in all its calculations and processing.Furthermore, this CFB bridle function calculator (or the DC control device calculator) may also include an IE input interface to receive at least information representative of a slip situation, information representative of the end of a slip situation, and the possible current speed of the vehicle V, to use them in calculations or processing, possibly after having shaped and / or demodulated them and / or. amplified, in a manner known per se, by means of a PR2 digital signal processor. In addition, this CFB clamping function calculator (or the DC control device calculator) may also include an IS output interface, in particular to deliver each message (or command) of replacement of the first threshold si by the second threshold s2 (or a threshold of an intermediate value between si and s2), each message (or command) of replacement of the second threshold s2 by the first threshold si (or a threshold of an intermediate value between s2 and si).

[0078] It will also be noted that the invention also proposes a computer program product (or computer program) comprising a set of instructions which, when executed by processing means of the type of electronic circuits (or hardware), such as for example the PR1 processor, is suitable for implementing the control method described above to control the clamping function in the presence of a slipping situation of at least one drive wheel Tl of the vehicle V.

Claims

Demands

1. A control method for a vehicle (V) comprising i) wheels, ii) a powertrain suitable for providing torque to at least two drive wheels (Tl), and iii) a speed limiting function suitable for preventing said vehicle (V) from moving backward at a speed having an absolute value greater than an absolute value of a first chosen threshold, characterized in that it comprises a step (10-30) in which, when a situation of slippage of at least one drive wheel (Tl) is detected, said first threshold is replaced by a second chosen threshold having an absolute value greater than said absolute value of said first threshold.

2. Method according to claim 1, characterized in that in said step (10-30) said slip situation is detected by performing an action selected from an analysis of information sent by a trajectory control function of said vehicle (V), a comparison of current rotational speeds of said wheels, and comparisons of speed gradients of said wheels at a threshold.

3. Method according to claim 1 or 2, characterized in that in said step (10-30) said first threshold is replaced by said second threshold when said slip situation is detected for at least a first chosen duration.

4. A method according to any one of claims 1 to 3, characterized in that in said step (10-30) said first threshold is replaced by said second threshold by progressively decreasing said first threshold until said second threshold is reached.

5. A method according to any one of claims 1 to 4, characterized in that in said step (10-30), when said slip situation is no longer detected after the replacement of said first threshold, said second threshold is continued to be used for a second chosen duration, and after the elapsed duration of said second threshold is replaced by said first threshold.

6. A method according to any one of claims 1 to 4, characterized in that in said step (10-30), when an absolute value of a running speed of said vehicle (V) is greater than the absolute value of said second threshold while said second threshold is being used, said second threshold is replaced by said first threshold.

7. Method according to claim 5 or 6, characterized in that in said step (10-30) said second threshold is replaced by said first threshold by progressively increasing said second threshold until said first threshold is reached.

8. Product computer program comprising a set of instructions which, when executed by processing means, is suitable for implementing the control method according to any one of claims 1 to 7, in a vehicle (V) comprising i) wheels, ii) a powertrain suitable for providing torque to at least two drive wheels (Tl), and iii) a speed limiting function suitable for preventing said vehicle (V) from moving backward at a speed having an absolute value greater than an absolute value of a first chosen threshold, for controlling said speed limiting function in the presence of a slip situation of at least one drive wheel (Tl).

9. Control device (DC) for a vehicle (V) comprising i) wheels, ii) a powertrain capable of supplying torque to at least two drive wheels (Tl), and iii) a speed limiting function capable of preventing said vehicle (V) from moving in reverse at a speed having an absolute value greater than an absolute value of a first chosen threshold, characterized in that it comprises at least one processor (PR1) and at least one memory (MD) arranged to perform the operations consisting, when a slip situation of at least one drive wheel (Tl) is detected, of triggering a replacement of said first threshold by a second chosen threshold having an absolute value greater than said absolute value of the first threshold.

10. Vehicle (V) comprising i) wheels, ii) a powertrain capable of supplying torque to at least two drive wheels (Tl), and iii) a speed limiting function capable of preventing said vehicle (V) from moving backward at a speed having an absolute value greater than an absolute value of a first chosen threshold, characterized in that it further comprises a control device (DC) according to claim 9.

Images