METHOD AND DEVICE FOR DETERMINING A MOTOR REFERENCE TORQUE OF A MOTOR VEHICLE

Abstract

A method is for determining the engine reference torque, used in a controller of a motor vehicle, of the engine of the motor vehicle, wherein the engine reference torque is determined by estimation. A value for the mass of the motor vehicle and a motor vehicle velocity value determined at each of two different times during acceleration of the motor vehicle are determined. An engine power of the engine is calculated from these values, and a value for the engine reference torque is estimated via the calculated engine power on the basis of power and torque curves, which are stored as a function of the speed of the engine.

Claims

1. A method for determining an engine reference torque (MRM), used in a controller of a motor vehicle, of an engine of the motor vehicle, the method comprising: determining a value for a mass (m) of the motor vehicle and a motor vehicle velocity value (v(t1), v(t2)) determined at each of two different times (t1, t2) during acceleration of the motor vehicle; calculating an engine power (P; P) of the engine from the value for the mass (m) and the motor vehicle velocity value (v(t1), v(t2)); and, estimating a value for the engine reference torque (MRM) via the calculated engine power (P; P) on a basis of power and torque curves, which are stored as a function of a speed (n.sub.M) of the engine.

2. The method of claim 1, wherein the two different times (t1, t2) are chosen to be so close to one another in time that acceleration values (a(t1), a(t2)) of the motor vehicle at the two different times (t1, t2) do not differ significantly from one another.

3. The method of claim 1, wherein the value for the mass (m) of the motor vehicle is determined from pneumatic spring pressures measured at the motor vehicle.

4. The method of claim 1, wherein the engine power (P) is calculated as follows: $P=\frac{m}{2}.Math.\frac{{v\left(t2\right)}^2-{v\left(t1\right)}^2}{t2-t1}$ wherein P is the engine power, m is the determined value of the mass of the motor vehicle, v(t1) is the value of the motor vehicle velocity determined at time t1, and v(t2) is the value of the motor vehicle velocity determined at time t2.

5. The method of claim 1, wherein, when calculating the engine power (P), at least one of following correction factors are taken into account: correction factor corr.sub.a,rot, which represents an acceleration of rotating masses of the motor vehicle; correction factor corr.sub.R, which represents a rolling resistance of the wheels of the motor vehicle; correction factor corr.sub.L, which represents an air resistance of the motor vehicle; correction factor corr.sub.St, which represents a climbing resistance of a gradient of a road used by the motor vehicle, and, correction factor corr.sub.div, which represents further frictional resistances.

6. The method of claim 1, wherein the engine reference torque (MRM) is estimated repeatedly; and, at least one of state models of the motor vehicle are taken into account and recursive or iterative estimation algorithms are applied.

7. The method of claim 1, wherein the engine reference torque (MRM) is estimated repeatedly; and, a Kalman filter is applied.

8. The method of claim 1, wherein the two different times (t1, t2) are checked for suitability and, if it is established that one of the two different times (t1, t2) is unsuitable, the associated motor vehicle velocity value (v(t1), v(t2)) is discarded or filtered out.

9. The method of claim 8, wherein, when checking the suitability of the two different times (t1, t2), signals from a braking system of the motor vehicle are taken into account; and, the signals indicate unsuitable motor vehicle behavior.

10. The method of claim 8, wherein, when checking the suitability of the two different times (t1, t2), signals from a controller of an anti-lock braking system or an electronic braking system are taken into account; and, the signals indicate unsuitable motor vehicle behavior.

11. The method of claim 8, wherein the signals include at least one of a brake actuation signal for signaling brake actuation and an activation signal for signaling activation of an anti-lock braking system.

12. The method of claim 1 further comprising: calculating a climbing resistance via an inclination sensor; calculating a correction factor corr.sub.St, which represents the climbing resistance, in dependence upon the climbing resistance; and/or, when an inclination is recognized via a gradient angle, generated by the inclination sensor, that is outside a predetermined range, a motor vehicle velocity value determined at a same time is excluded or declared to be unsuitable.

13. The method of claim 1, wherein the engine power (P) is continuously calculated repeatedly and a maximum value (Pmax) of the engine power is determined by replacement of an already existing maximum value (Pmax) of the engine power with a greater calculated value of the engine power (Pneu), provided that the greater calculated value (Pneu) has previously been evaluated as being reliable.

14. The method of claim 1, wherein measured engine speed information (n.sub.M) or engine speed information (n.sub.M) derived from information about an engaged gear and a wheel speed (N.sub.R) is used; and, the engine reference torque is determined from the engine speed information (n.sub.M) and the engine power (P).

15. The method of claim 1, wherein the engine reference torque (MRM) is continuously estimated repeatedly and a maximum value (MRM) of the engine reference torque is determined by replacement of an already existing value (MRMalt) for the maximum value with a greater estimated value of the engine reference torque (MRMneu), provided that the greater estimated value of the engine reference torque (MRMneu) has been evaluated as being reliable.

16. A device for determining an engine reference torque, used in a controller of a motor vehicle, of an engine of the motor vehicle, the device comprising: a computer configured to calculate an engine power (P, P) of the engine from a value for a mass (m) of the motor vehicle and from motor vehicle velocity values (v(t1), v(t2)) obtained at two different times (t1, t2) during acceleration of the motor vehicle; and, an estimator configured to estimate a value for the engine reference torque (MRM) via the calculated engine power (P, P) on a basis of power and torque curves, which are stored as a function of the speed (n.sub.M) of the engine.

17. A controller of a braking system of a motor vehicle, the controller comprising: a processor; a non-transitory computer readable storage medium having program code stored thereon; said program code being configured, when executed by said processor, to: determine a value for a mass (m) of the motor vehicle and a motor vehicle velocity value (v(t1), v(t2)) determined at each of two different times (t1, t2) during acceleration of the motor vehicle; calculate an engine power (P; P) of an engine from the value for the mass (m) and the motor vehicle velocity value (v(t1), v(t2); and, estimate a value for the engine reference torque (MRM) via the calculated engine power (P; P) on a basis of power and torque curves, which are stored as a function of a speed (n.sub.M) of the engine.

18. A controller of a braking system of a motor vehicle, the controller comprising the device for determining the engine reference torque of the engine of the motor vehicle of claim 16.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0049] The invention will now be described with reference to the drawings wherein:

[0050] FIG. 1 shows an embodiment of a device according to the disclosure for determining the engine reference torque of the engine of a motor vehicle;

[0051] FIG. 2 shows an embodiment of a method according to the disclosure for determining the engine reference torque using a device according to FIG. 1;

[0052] FIG. 3 shows an embodiment of an arrangement of the device shown in FIG. 1 outside a controller which uses the engine reference torque; and,

[0053] FIG. 4 shows an embodiment of an alternative arrangement of the device shown in FIG. 1 inside a controller which uses the engine reference torque.

DETAILED DESCRIPTION

[0054] FIG. 1 shows an embodiment of a device 10 according to the disclosure for determining the engine reference torque of the engine of a motor vehicle.

[0055] The engine of a motor vehicle is understood as being the engine system, which in the simplest case includes only a combustion engine but in more highly developed engine systems, for example hybrid vehicles, includes the totality of the drive units, for example a combustion engine as well as one or more electric motors, which serve to drive the vehicle. Depending on the operating mode, a hybrid vehicle is driven either only by the electric motor or motors or the combustion engine or simultaneously by the combustion engine and the electric motor or motors. The engine reference torque denotes the maximum torque of all the drive units together.

[0056] The device 10 is part of a motor vehicle, in particular part of one of its system components.

[0057] The device 10 includes a computer 12 and an estimator 14.

[0058] The computer 12 receives various variables and parameters, in particular a value for the mass m of the motor vehicle and two motor vehicle velocity values v(t1), v(t2) obtained at different times t1 and t2. The motor vehicle velocity values v(t1), v(t2) can be determined, for example, from wheel speeds, which are obtained from wheel speed sensors. Such wheel speed sensors are generally installed in vehicles which have an anti-lock braking system or an electronic braking system. The vehicle velocity values v(t1), v(t2) can, for example, also be transmitted directly to the device 10 by a controller of an anti-lock braking system or of an electronic braking system.

[0059] The mass m of the motor vehicle can be determined, for example, from pneumatic spring pressures measured at the motor vehicle. For this purpose, a pressure in the pneumatic spring system is measured and the mass m of the motor vehicle is calculated from the measured pressure.

[0060] Determination of the mass m of the motor vehicle is expedient in particular in the case of commercial vehicles, since the load of a commercial vehicle can change significantly and a loaded commercial vehicle can therefore reach a multiple of the mass of the same commercial vehicle without a load.

[0061] The computer 12 first calculates an engine power P from the values of the mass m and the motor vehicle velocity values v(t1), v(t2) via the equation

[00003]$P=\frac{m}{2}.Math.\frac{{v\left(t2\right)}^2-{v\left(t1\right)}^2}{t2-t1}.$

[0062] Preferably, the engine power so calculated is considered to be only a preliminary value P, which is corrected by one or more of the correction factors by multiplication of the preliminary value P by one or more of the correction factors.

[0063] The correction factors include the following variables: [0064] a correction factor corr.sub.a,rot, which represents an acceleration of rotating masses of the motor vehicle, [0065] a correction factor corr.sub.R, which represents a rolling resistance of the wheels of the motor vehicle, [0066] a correction factor corr.sub.L, which represents an air resistance of the motor vehicle, [0067] a correction factor corr.sub.St, which represents a climbing resistance of a gradient of the road used by the motor vehicle, [0068] a correction factor corr.sub.div, which represents further frictional resistances.

[0069] The value for the engine power P that is outputted by the computer 12 is therefore given by multiplication of the preliminary value P by the correction factor corr.sub.a,rot, the correction factor corr.sub.R, the correction factor corn, the correction factor corr.sub.St and/or the correction factor corr.sub.div.

[0070] The computer 12 can receive further variables and parameters, such as the inclination or gradient a of the vehicle, which can be measured via an inclination sensor.

[0071] The computer 12 can further receive the speed of the engine n.sub.M determined by measurement orwhere presentthe speeds of further motors, in particular in the case of hybrid vehicles.

[0072] The computer 12 can further receive the speed of a wheel n.sub.M or speeds of a plurality of wheels determined by measurement. The computer 12 can further receive information about the engaged gear G. The computer 12 is able to derive the engine speed from the information about the engaged gear G and from the determined wheel speed n.sub.M.

[0073] The computer 12 further receives information about any interventions for actuation of the wheel brakes or the engine speed from an anti-lock braking system ABS, an electronic braking system EBS, an electronic stability control system ESP, an anti-slip regulation system ASR and/or an engine drag torque control system MSR. From this information, it is derived whether the vehicle velocity values v(t1), v(t2) used are suitable or unsuitable within the context of the estimation of the engine reference torque. These motor vehicle velocity values v(t1), v(t2) are generally unsuitable if they have been determined during an intervention of one of these systems. If it is established that the motor vehicle velocity values v(t1), v(t2) are unsuitable, either the power calculation is not carried out at all or a power value P that has been obtained is discarded.

[0074] The computer 12 transmits suitable power values P to the estimator 14. The estimator 14 estimates a value for the engine reference torque MRM via the calculated engine power P on the basis of power and torque curves 16, which are stored as a function of the speed of the engine n.sub.M. This value is processed further by the device 10, optionally taking account of state models of the motor vehicle and/or recursive and interactive estimation algorithms, for example using a Kalman filter.

[0075] Finally, the device 10 provides a value for the engine reference torque MRM to one or more controllers of the motor vehicle, such as, for example, a controller for engine drag torque control, an ABS controller or an EBS controller.

[0076] FIG. 2 shows an example of a procedure 20 for determining the engine reference torque MRM.

[0077] After the start 22 of the method 20, method parameters are first initialized in an initialization step 24.

[0078] In a determination step 26, a value m of the mass of the motor vehicle is determined as described above, for example on the basis of pressures in the pneumatic suspension system.

[0079] In a further determination step 28, a motor vehicle velocity value v(t1), v(t2) is determined at each of two different times t1 and t2 during acceleration of the motor vehicle.

[0080] In a checking step 30, it is checked whether the acceleration of the motor vehicle was approximately equal at the two times, in order to ensure that an approximately constantly accelerated movement of the motor vehicle is present. If that is not the case, the procedure branches back to determination step 28 via branch 32.

[0081] If an approximately constantly accelerated movement of the motor vehicle is present, it is checked in a further checking step 34 whether times t1 and t2 as well as the motor vehicle velocity values v(t1), v(t2) are suitable. To this end, it is checked whether the times were sufficiently close together that a constantly accelerated movement can be assumed with sufficiently high accuracy. In additionas explained aboveit is checked whether any interventions by driver assistance systems, such as by an anti-lock braking system ABS, an electronic braking system EBS, an electronic stability control system ESP, an anti-slip regulation system ASR and/or an engine drag torque control system MSR, were present at times t1 and t2, in order to declare the vehicle velocity values v(t1), v(t2) to be unsuitable if appropriate.

[0082] Furthermore, when an inclination is recognized via a gradient angle, generated by the inclination sensor, that is outside a predetermined range, a motor vehicle velocity value determined at the same time is excluded or declared to be unsuitable.

[0083] If it has been established that the values, in particular the motor vehicle velocity values, used are unsuitable, the procedure branches back to determination step 28 via branch 36.

[0084] In a calculation step 38, a preliminary value for the engine power P is calculated from the mass m of the motor vehicle as well as the motor vehicle velocity values v(t1), v(t2) and the time difference t2t1 of the two times t1 and t2.

[0085] In a following correction step 40, the preliminary value for the engine power P is corrected by multiplication by one or more of the above-mentioned correction factors.

[0086] In a checking step 42, it is checked whether the calculated and optionally corrected instantaneous engine power Pneu is greater than a previously calculated and optionally corrected engine power Palt. If that is the case, the method branches to replacement step 44, in which a previously stored maximum value Pmax is replaced with the instantaneous value for the engine power Pneu, and the method continues with an estimation step 46.

[0087] If, however, it is established in checking step 42 that the calculated and optionally corrected instantaneous engine power Pneu is not greater than a previously calculated and optionally corrected engine power Palt, replacement step 44 is skipped and the method continues with estimation step 46.

[0088] In estimation step 46, the engine reference torque MRM is estimated. Since steps 28, 30, 34, 38, 40, 42 and 44, which have been discussed, are continuously carried out repeatedly, the engine reference torque is also estimated repeatedly. State models of the motor vehicle can here be used, and/or recursive or iterative estimation algorithms can be incorporated, for example by Kalman filters. Unsuitable values can be recognized and filtered out.

[0089] In a checking step 48, it is checked whether the instantaneously estimated engine reference torque MRMneu is greater than the previously estimated engine reference torque MRMalt. If that is the case, the method branches to replacement step 50, in which a previously stored engine reference torque MRMalt is replaced with the instantaneously estimated engine reference torque MRMneu, and the method continues with determination step 28.

[0090] If, however, it is established in checking step 48 that the instantaneously estimated engine reference torque MRMneu is not greater than the previously estimated engine reference torque MRMalt, replacement step 50 is skipped and the method continues with determination step 28.

[0091] FIG. 3 shows an arrangement of the device 10 shown in FIG. 1 outside a controller 60, which receives the engine reference torque MRM from the device 10 and uses it. Via a data link 61, data, in particular the parameters explained in connection with FIG. 1, can be exchanged between the controller 60 and the device 10.

[0092] FIG. 4 shows an alternative arrangement of the device 10 shown in FIG. 1 inside such a controller 62 which uses the engine reference torque MRM.

[0093] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

LIST OF REFERENCE SIGNS (PART OF THE DESCRIPTION)

[0094] 10 device [0095] 12 computer [0096] 14 estimator [0097] 16 power and torque curves [0098] 20 procedure [0099] 22 start [0100] 24 initialization step [0101] 26 determination step [0102] 28 determination step [0103] 30 checking step [0104] 32 branch [0105] 34 checking step [0106] 36 branch [0107] 38 calculation step [0108] 40 correction step [0109] 42 checking step [0110] 44 replacement step [0111] 46 estimation step [0112] 48 checking step [0113] 50 replacement step [0114] 60 controller [0115] 61 data link [0116] 62 controller [0117] m mass of the motor vehicle [0118] t1 time [0119] t2 time [0120] v(t1) motor vehicle velocity value at time t1 [0121] v(t2) motor vehicle velocity value at time t2 [0122] a(t1) motor vehicle acceleration value at time t1 [0123] a(t2) motor vehicle acceleration value at time t2 [0124] corr.sub.a,rot correction factor representing the acceleration of rotating masses of the motor vehicle [0125] corr.sub.R correction factor representing the rolling resistance of the wheels of the motor vehicle [0126] corr.sub.L correction factor representing the air resistance of the motor vehicle [0127] corr.sub.St correction factor representing the climbing resistance [0128] corr.sub.div correction factor representing further frictional resistances [0129] inclination/gradient [0130] N.sub.M engine speed [0131] N.sub.R wheel speed [0132] G gear [0133] MRM engine reference torque [0134] MRMneu instantaneous engine reference torque [0135] MRMalt previous engine reference torque [0136] P engine power [0137] P preliminary engine power [0138] Pneu instantaneous engine power [0139] Palt previous engine power [0140] Pmax maximum engine power [0141] ABS anti-lock braking system [0142] EBS electronic braking system [0143] ESP electronic stability control system [0144] ASR anti-slip regulation system [0145] MSR engine drag torque control system