ADAPTIVE CONTROL OF MOTOR VEHICLE POWERTRAIN

Abstract

A method and system for blending between different torque maps of a vehicle in a smooth and progressive manner. Blending is delayed if the vehicle driver cannot detect that blending is taking place, for example, when the difference between a source map and target map is below a predetermined threshold.

Claims

1. A method of blending between different characteristics of accelerator pedal position and output torque in a vehicle, the method comprising: detecting a first operating mode of the vehicle, and applying a source torque characteristic associated with the first operating mode; changing to a second operating mode of the vehicle, and selecting a target torque characteristic associated with the second operating mode; progressively blending, by an electronic control system of the vehicle, the first operating mode source torque characteristic to the second operating mode target torque characteristic over time; wherein the blending is delayed if the difference between the source characteristic and the target characteristic at the instant position of the accelerator pedal is below a pre-determined threshold.

2. The method according to claim 1, wherein the blending is delayed by gradual commencement or gradual termination thereof.

3. The method according to claim 1, wherein blending is delayed by suspension thereof.

4. The method according to claim 1, comprising completing blending from the source torque characteristic to the target torque characteristic within a predetermined period.

5. The method according to claim 1, comprising detecting a change to the second operating mode.

6. The method according to claim 1, wherein the first operating mode source torque characteristic comprises a source torque map associated with the first operating mode, and the second operating mode target torque characteristic comprises a target torque map associated with the second operating mode.

7. The method according to claim 1, wherein the first operating mode source torque characteristic comprises a source torque value associated with the first operating mode and the instant position of the accelerator pedal, and the second operating mode target torque characteristic comprises a target torque value associated with the second operating mode and the instant position of the accelerator pedal.

8. A method of blending between different characteristics of accelerator pedal position and output torque in a vehicle, the method comprising: detecting a first operating mode of the vehicle, and applying a source torque characteristic associated with the first operating mode; changing to a second mode of the vehicle and selecting a target torque characteristic associated with the second operating mode; progressively blending, by an electronic control system of the vehicle, the first operating mode source torque characteristic to the second operating mode target torque characteristic over time; wherein the blending is delayed if the position of the accelerator pedal is substantially unchanging.

9. The method according to claim 8, comprising completing blending from the source torque characteristic to the target torque characteristic within a predetermined period.

10. The method according to claim 8, comprising detecting a change to the second operating mode.

11. An electronic control system of a vehicle for blending between different characteristics of accelerator pedal position and output torque by reference to a plurality of torque characteristics held within a memory, the system being configured to: detect a first operating mode of the vehicle and apply a source torque characteristic associated with the first operating mode; detect a change in the operating mode of the vehicle from the first operating mode to a second operating mode and select a target torque characteristic associated with the second operating mode; and blend from the first operating mode source torque characteristic to the second operating mode target torque characteristic over time, the system being further configured to delay blending if a difference between the first and second torque characteristics is below a predetermined threshold.

12. The system according to claim 11, further configured to delay blending by gradual commencement or gradual termination thereof.

13. The system according to claim 11, further configured to delay blending by suspension thereof.

14. The system according to claim 11, further configured to complete blending within a predetermined period.

15. The system according to claim 11, wherein the first operating mode source torque characteristic comprises a source torque map associated with the first operating mode, and the second operating mode target torque characteristic comprises a target torque map associated with the second operating mode.

16. The system according to claim 11, wherein the first operating mode source torque characteristic comprises a source torque value associated with the first operating mode and an instant accelerator pedal position, and the second operating mode target torque characteristic comprises a target torque value associated with the second operating mode and the instant accelerator pedal position

17. A vehicle comprising the electronic control system according to claim 11, and a system for automatically changing the operating mode of the vehicle according to different conditions of use, whereby one of the plurality of torque characteristics is selected for each operating mode.

18. An electronic control system of a vehicle for blending between different characteristics of accelerator pedal position and output torque by reference to a plurality of torque characteristics held within a memory, the system being configured to: detect a first operating mode of the vehicle and apply a source torque characteristic associated with the first operating mode; detect a change in the operating mode of the vehicle from the first operating mode to a second operating mode of the vehicle and select a target torque characteristic associated with the second operating mode; and blend from the first operating mode source torque characteristic to the second operating mode target torque characteristic over time, the system being further adapted to delay blending if the position of the accelerator pedal is substantially unchanging.

19. The system according to claim 18, further configured to complete blending within a predetermined period.

20. A vehicle comprising the electronic control system according to claim 18, and a system for automatically changing the operating mode of the vehicle according to different conditions of use, whereby one of the plurality of torque characteristics is selected for each operating mode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0046] FIG. 1 is a schematic illustration of a known motor vehicle;

[0047] FIGS. 2 and 3 illustrate graphically the blending of engine torque between different vehicle modes;

[0048] FIG. 4 is a schematic illustration of a motor vehicle according to an embodiment of the present invention;

[0049] FIG. 5 indicates torque progression during a blend from one operating mode to another;

[0050] FIG. 6 shows zones of delayed blending where a torque difference is below a threshold; and

[0051] FIG. 7 shows suspension of blending with reference to the characteristics of FIG. 6.

DETAILED DESCRIPTION

[0052] With reference to the drawings, FIG. 4 is a schematic illustration of a motor vehicle 201 according to an embodiment of the present invention. Like features of the vehicle 201 of FIG. 4 to those of the vehicle 101 of FIG. 1 are shown with like reference numerals prefixed numeral 2 instead of numeral 1. Thus engine 121 of the vehicle 101 of FIG. 1 corresponds to engine 221 of the vehicle 221 of FIG. 4.

[0053] The vehicle 201 has a VCU 201C programmed with accelerator pedal progression maps that are used to determine engine torque T as a function of accelerator pedal position P. In the embodiment of FIG. 4 the modes include modes A and B having accelerator pedal progression maps with characteristics A and B, respectively, as described above and illustrated in FIG. 2.

[0054] FIG. 5 illustrates blending of cautious characteristic A of accelerator position P and engine torque T to aggressive characteristic B. As noted above, characteristics A and B represent different vehicle operating modes. The blend progresses generally in the direction of arrow E at a constant rate of 7 Nm/s although other values are also useful. Any advance of accelerator position toward maximum (100%) or release toward minimum (0%) will provide engine torque at the intermediate torque characteristic that has been reached. Three intermediate torque characteristics defined in the blending process are labeled in FIG. 5, being characteristic C1 (assumed at time t1 after blending has commenced), characteristic C2 (assumed at time t2 after blending has commenced) and characteristic C3 (assumed at time t3 after blending has commenced).

[0055] Thus for example an advance of accelerator pedal position from 30% to 50% at time t3 after blending has commenced results in a change in torque characteristic from point C to point D, along the intermediate line C3 of FIG. 5.

[0056] Other kinds of blending may be applied, for example where blending from one torque value to another along the vertical axis of FIG. 2 is conducted at a steady rate so that the shape of the initial characteristic is maintained until the new characteristic is reached. Thus, in blending from characteristic A to characteristic B of FIG. 2, the intermediate characteristics might follow the form of characteristic A over a range of pedal positions above and below which the new characteristic (B) is followed. It is to be understood that at the transition point between characteristics a discontinuity in engine torque T as a function of pedal position P may be experienced. Thus, in the embodiment of FIG. 4 a given change of accelerator pedal position P before blending is complete may result in a change of torque characteristic from that of mode A to that of mode B or from that of mode B to that of mode A between the start and end positions of the accelerator pedal 261. In other words, over part of the range of movement of the accelerator pedal 161 the VCU 201C may follow characteristic A and over another part of the range of movement the VCU 201C may follow characteristic B. In contrast, in the embodiment of FIG. 4 having intermediate characteristics C of the form illustrated in FIG. 5, a relatively smooth transition from one characteristic to another is effected. Other arrangements are also useful.

[0057] Some embodiments of the present invention are not limited to a particular form of blending process from one torque characteristic to another save that it should provide a progressive change from one torque characteristic to another. Each such characteristic may represent a vehicle operating mode as discussed above. In some embodiments the torque characteristics represent only different respective operating modes.

[0058] According to one embodiment of the invention the blend is delayed in the event that a blend is commanded automatically by the VCU 201C and the accelerator pedal position P is substantially unchanging. Thus, in some embodiments blending is delayed until the accelerator pedal 261 is moved by the driver. The manner in which the delay is implemented under these conditions will be described in more detail below.

[0059] It can be seen from FIG. 2 that at accelerator pedal positions of 0% and 100% of travel, all torque characteristics coincide. Between these end positions of the torque characteristics, the torque characteristics diverge between extremes represented in this example by lines A and B.

[0060] If the blend is delayed, the instant characteristic is applied to throttle pedal position P, so that for example a paused blend may correspond to characteristic C2 of FIG. 5. In the event the blend has not yet commenced but a delay has been imposed due to lack of movement of the accelerator pedal 261 since a mode change took place, the instant characteristic may correspond to that of the mode in which the vehicle has been operating (the source mode) prior to the command to assume a new mode (the target mode). The instant characteristic applies (i.e. is maintained) until a change in the accelerator pedal position P subsequently exceeds a threshold value, in which case the blend proceeds in the required direction, for example from characteristic A to characteristic B.

[0061] The blend may pause several times before a transition between modes is completed, assuming that no further change of vehicle mode is sensed or commanded.

[0062] As well as delaying blending due to lack of change of P as a function of time, the VCU 201C may delay the blend if accelerator pedal position P approaches the zero or 100% end position. For example delaying (pausing) of blending may be implemented when the accelerator pedal position P is at less than 10% and more than 90% of pedal travel. Pausing may also be implemented if the difference between the target and source accelerator pedal position characteristics is relatively small, for example less than 5% at any intermediate position of the accelerator pedal 161.

[0063] FIG. 6 illustrates pausing of the blend if the torque difference between the instant torque F and target torque G is small. Accelerator pedal position (P) is plotted against output torque (T). In this case the two pedal progression maps (F, G) are quite similar, and cross over at around the mid-position of the accelerator pedal 161. It is to be understood that, in the embodiment shown, at less than 5% advance of the accelerator pedal 161, between 45 and 55% advance, and above 95% advance, blending is delayed. In this example the instant and target torque separation is about 5% in the delay range, but the limit may be selected according to any desired result so that blending is delayed if the change of map demanded automatically by the VCU 201C has too small a torque difference to be noticed by the vehicle driver.

[0064] Thus in practice slight changes of accelerator pedal position P, where the change in the position of the accelerator pedal 161 causes the delay region of the map to be entered, will substantially pause blending substantially at the characteristic that the blend has reached, until such time that the accelerator pedal position P sufficiently departs from the region associated with the pause. For example, with reference to FIG. 5, blending may substantially pause at C2 until the accelerator pedal 161 is moved sufficiently at which time blending will continue to C3 and eventually reach characteristic B. Blending may also be paused in the reverse direction of torque change, for example from operating mode B to operating mode A.

[0065] FIG. 7 corresponds to FIG. 6, and shows blending according to the torque maps F, G. Blending (B) is represented by a minimum or suspended rate (state 0) and a maximum rate (state 1).

[0066] It can be seen from FIG. 7 that blending (B) is suspended at 0-5% accelerator pedal position because in this instance the torque difference between maps F, G is below a threshold of 5%. If the amount of accelerator pedal depression P is then increased, the blending rate B ramps up to the maximum rate as a function of accelerator pedal position P, by reference to a look-up table. In some alternative embodiments, in addition or instead the blending rate B may ramp up to the maximum rate as a function of time once the pedal position P is not within a range in which blending is suspended. Blending may continue at the maximum rate until suspension is again indicated at accelerator pedal positions P between 45 and 55% of full deflection. The same procedure occurs above 55%, as illustrated.

[0067] As the accelerator pedal 261 approaches a region of deflection in which suspension is indicated, the rate of blending may reduce as a function of pedal position P again by reference to a look-up table. In some embodiments, in addition or instead the rate of blending may reduce as a function of time as the accelerator pedal 261 approaches or enters a region in which suspension is indicated. The rate at which blending is introduced and withdrawn may be variable in some embodiments. This is indicated by the slopes of the blending rate characteristic between state 0 and state 1 shown in FIG. 7. The blending rate as a function of accelerator pedal position P when blending is being introduced or withdrawn is determined according to the instant difference between the respective torque maps in the embodiment illustrated in FIG. 7 although other arrangements are also useful. In the embodiment of FIG. 7 this rate is, for simplicity, illustrated as a straight line (constant rate of increase or decrease). Thus the rate of introduction and withdrawal may be proportional to the difference between the source and target maps. However, the rate of introduction or withdrawal of blending as a function of pedal position P can follow any other suitable desirable shape and provide, for example, an exponential rate of increase or decrease. Other arrangements are also useful.

[0068] Embodiments of the present invention have the advantage that a driver will not be surprised by a change in accelerator pedal position/engine torque output characteristic of a vehicle 201 following a mode change implemented automatically by the VCU 201C (as opposed to a change implemented in response to a user command to change mode). This is because, according to some embodiments of the invention, under conditions in which a driver does not change the accelerator pedal position P and/or in which the difference in output torque between the source and target modes is less than a prescribed value, the blending rate is reduced (and in some embodiments blending is substantially suspended or stopped). Blending may be substantially stopped, or the rate of blending reduced to a sufficiently low value, until one or more prescribed conditions are met. The rate of blending when blending is reduced may be determined as a value that is sufficiently low that a driver will not be surprised by a change of accelerator pedal progression characteristic (due to the continuation of blending) when the driver next moves the accelerator pedal. An accelerator pedal may remain in a condition of substantially zero advancement with a driver's foot removed from the pedal for a not insignificant period of time under certain circumstances, for example when a vehicle is stopped at traffic lights, or a driver has paused to view scenery or wildlife. Accordingly, a driver's mental memory of the accelerator pedal progression map will fade with time, and the driver will not be surprised by a change in pedal progression map when the driver subsequently depresses the accelerator pedal.

[0069] Throughout the description and claims of this specification, the words comprise and contain and variations of the words, for example comprising and comprises, means including but not limited to, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

[0070] Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0071] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.