Method and device for determining the mass of a motor vehicle, and a motor vehicle with a device of this type

Abstract

A method for determining the mass m of a motor vehicle, in particular a commercial vehicle, is based on the principles of power mechanics. In order to determine the vehicle mass in a simple way as accurately as possible while driving, a speed v of the motor vehicle is determined and a drive power P.sub.A of the motor vehicle is determined. The mass m of the motor vehicle can then be determined from the speed v and the drive power P.sub.A. A device applies such a method, and a motor vehicle includes such a device.

Claims

1. A method for controlling a vehicle control system comprising the following steps: determining a speed (v) of the motor vehicle for two mutually different instants (t.sub.0, t.sub.1) separated by a time interval in which driving resistances (F.sub.L, F.sub.R, F.sub.St) belonging to the instants (t.sub.0, t.sub.1) are assumed not to differ between the instants (t.sub.0, t.sub.1); determining drive powers (P.sub.A0, P.sub.A1) of the motor vehicle for the two instants (t.sub.0, t.sub.1), each of the drive powers (P.sub.A) being determined as follows:
P.sub.A=(M.sub.engM.sub.fric)*.sub.eng*, with P.sub.A being one of the drive powers (P.sub.A0, P.sub.A1), M.sub.eng being a drive torque of the engine, M.sub.fric being a frictional torque of the engine, .sub.eng being an angular velocity of the engine, and being a parameterized efficiency of the drivetrain; determining an estimated mass (m) of the motor vehicle from the speeds (v.sub.0, v.sub.1) and from the drive powers (P.sub.A0, P.sub.A1) at the two instants (t.sub.0, t.sub.1); supplying electronic information representative of the estimated mass (m) to a vehicle control system, the vehicle control system being at least one of an anti-lock brake system or an electronically controlled brake system; and operating the vehicle control system based on the electronic information.

2. The method according to claim 1, wherein a power (P.sub.R) for overcoming the driving resistances is determined, and the estimated mass (m) of the motor vehicle is further determined from the speed (v), a current drive power (P.sub.A) and the power (P.sub.R) for overcoming the driving resistances, the difference between the current drive power (P.sub.A) and the power (P.sub.R) for overcoming the driving resistances corresponding to the change in the kinetic energy of the motor vehicle.

3. The method according to claim 1 wherein the speed (v) of the motor vehicle is determined by means of a measured wheel rotational speed signal (n).

4. The method according to claim 1, wherein the power (P.sub.R) for overcoming the driving resistances is determined from a sum of individual driving resistances (F.sub.L, F.sub.R, F.sub.St) multiplied by the speed (v) of the motor vehicle.

5. The method according to claim 1, wherein the estimated mass (m) of the motor vehicle is determined from the speed (v) and a current drive power (P.sub.A) by using a recursive estimation algorithm, wherein the recursive estimation algorithm is carried out by a Kalman filter or by a recursive least squares estimator (RLS filter).

6. The method according to claim 1, wherein a mean value ({circumflex over (m)}) is formed from at least three measured values for the estimated mass (m) of the motor vehicle, the calculation of the mean value ({circumflex over (m)}) being performed taking account of the variance of the respective measured values for the estimated mass (m) of the motor vehicle, the mean value ({circumflex over (m)}) being supplied to the vehicle control system as the electronic information representative of the estimated mass (m).

7. An electronic processor for determining an estimated mass (m) of a motor vehicle, the device configured for determining a speed (v) of the motor vehicle for two mutually different instants (t.sub.0, t.sub.1) separated by a time interval in which driving resistances (F.sub.L, F.sub.R, F.sub.St) belonging to the instants (t.sub.0, t.sub.1) are assumed not to differ between the instants (t.sub.0, t.sub.1), for determining drive powers (P.sub.A0, P.sub.A1) of the motor vehicle for the two instants (t.sub.0, t.sub.1), with each of the drive powers (P.sub.A) being determined as follows:
P.sub.A=(M.sub.engM.sub.fric)*.sub.eng*, with P.sub.A being one of the drive powers (P.sub.A0, P.sub.A1), M.sub.eng being a drive torque of the engine, M.sub.fric being a frictional torque of the engine, .sub.eng being an angular velocity of the engine, and being a parameterized efficiency of the drivetrain, and for determining the estimated mass (m) from the speeds (v.sub.0, v.sub.1) and from the drive powers (P.sub.A0, P.sub.A1) at the two instants (t.sub.0, t.sub.1), the device comprising an interface for supplying electronic information representative of the estimated mass (m) to a vehicle control system, the vehicle control system being at least one of an anti-lock brake system or an electronically controlled brake system; and for causing the vehicle control system to operate based on the electronic information.

8. The electronic processor according to claim 7, further configured for determining a power (P.sub.R) for overcoming driving resistances, wherein the device determines the estimated mass (m) from the speed (v), a current drive power (P.sub.A) and further from the power (P.sub.R) for overcoming the driving resistances.

9. The electronic processor according to claim 7, further configured for determining the estimated mass (m) of the motor vehicle by a recursive estimation algorithm, wherein the recursive estimation algorithm is carried out by a Kalman filter or by a recursive least squares estimator (RLS filter).

10. The electronic processor according to claim 7, further configured for determining a mean value ({circumflex over (m)}) from at least three different measured values of the estimated mass (m) of the motor vehicle, a variance of the measured values being taken into account in each case.

11. A motor vehicle comprising a vehicle control system, the vehicle control system being at least one of an anti-lock brake system or an electronically controlled brake system, and an electronic processor for determining an estimated mass (m) of the motor vehicle, the device configured for determining a speed (v) of the motor vehicle, for determining drive powers (P.sub.A0, P.sub.A1) of the motor vehicle for two instants (t.sub.0, t.sub.1), each of the drive powers (P.sub.A) being determined as follows:
P.sub.A=(M.sub.engM.sub.fric)*.sub.eng*, with P.sub.A being one of the drive powers (P.sub.A0, P.sub.A1), M.sub.eng being a drive torque of the engine, M.sub.fric being a frictional torque of the engine, .sub.eng being an angular velocity of the engine, and being a parameterized efficiency of the drivetrain for determining the estimated mass (m) from the speed (v) and from the drive powers (P.sub.A0, P.sub.A1) at the two instants (t.sub.0, t.sub.1), and for supplying electronic information representative of the estimated mass (m) to the vehicle control system, wherein the vehicle control system is configured to operate based on the electronic information.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further embodiments of the invention are evident from the exemplary embodiments explained in more detail with the aid of the drawing, in which:

(2) FIG. 1 shows a block diagram for explaining the method according to the invention for determining the mass of a motor vehicle, and

(3) FIG. 2 shows a flowchart for explaining the formation of the mean value in accordance with the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 shows a block diagram for explaining the method according to the invention for determining the mass m of a motor vehicle. Calculating means 2 which determine a mass m of the motor vehicle with the aid of a plurality of input variables are provided for carrying out the method.

(5) Firstly means 4 for determining the speed v and also means 6 for determining the drive power P.sub.A are provided for the input variables required for determining the mass m. It is possible in this case to use any desired procedure to determine the required input variables within the scope of the present invention.

(6) In contrast to conventional methods for determining the mass m of a motor vehicle, it is the principles of power mechanics on which the method is based, rather than the equation of motion. The invention has recognized that the drive power P.sub.A can be determined merely via the engine torques M.sub.eng, M.sub.fric by taking account of the angular velocity of the engine .sub.eng with the aid of the means 6.

(7) Various approaches are considered in the calculating means 2 for determining the mass m of the motor vehicle. If the device has suitable means 8 for determining the power P.sub.R for overcoming the driving resistances, said power P.sub.R is passed on to the calculating means 2. However, this requires that the individual driving resistances F.sub.L, F.sub.R, F.sub.St of the motor vehicle be known.

(8) If this is not the case, a timer 10 is used to determine two instants t.sub.0, t.sub.1 which lie as close to one another as possible so that the driving resistances F.sub.L, F.sub.R, F.sub.St at both instants t.sub.0, t.sub.1 are substantially identical. To be specific, if the instants t.sub.0, t.sub.1 lie sufficiently close to one another it can be assumed that the driving resistances F.sub.L, F.sub.R, F.sub.St also have not changed substantially within this short time period.

(9) The calculating means 2 are configured in such a way as to determine the mass m of the motor vehicle in accordance with Equation (9) from the speeds v.sub.0, v.sub.1 of the motor vehicle at the two instants t.sub.0, t.sub.1 and from the drive powers P.sub.A0, P.sub.A1.

(10) In this case, moments of inertia of the rotating masses which are required for the determination of the rotational energy are estimated or stored as vehicle parameters.

(11) In order to minimize the number of erroneous calculations of the mass m of the motor vehicle, it is preferable to apply a recursive estimation algorithm 11 in the calculating means 2 to determine the mass m. This is because, for example, the values for the mass m of the motor vehicle can be corrupted by noisy signals and/or by rapidly varying driving resistances. The recursive estimation algorithm 11 minimizes the error square of the estimation error. It is advantageous that in this case previous measured values also feature in the current estimation, which means there is more information available for the estimation.

(12) One embodiment of the invention provides that the recursive estimation algorithm 11 is the least squares algorithm, also known as RLS algorithm. This algorithm is known per se to the person skilled in the art and is therefore not explained further here.

(13) An alternative embodiment of the invention provides that the recursive estimation algorithm 11 is the Kalman algorithm. Said algorithm is likewise known to the person skilled in the art and is therefore not explained further here.

(14) On the basis of the above named recursive estimation algorithm 11, which is applied in the calculating means 2 to determine the mass m of the motor vehicle, the mass m output by the calculating means 2 is already advantageously a measured value of high quality.

(15) Said measured value for the mass m is passed on to a further means 12 for determining a mean value and stored, in order to minimize the risk of a faulty calculation, particularly due to outliers in the measured values.

(16) FIG. 2 shows a flowchart for explaining the formation of mean values applied in block 12 of FIG. 1. Via a connecting branch 22, the start icon is connected to a query icon 24 which queries whether three measured values are present for the mass m. As long as there are not three measured values available for the mass m, a no signal 26 is passed on to block 28, which signals waiting for further measured values for the mass m. The end icon 30 is reached via a connecting branch 32 from block 28, and the method can begin again.

(17) If, however, it is recognized from the query icon 24 that three measured values are present for the mass m, a yes signal 34 is passed on to a block 36, in which a mean value is calculated from the three measured values. Said mean value is calculated by taking account of the variance of the individual measured values using the reciprocal of the variance as weighting factor.

(18) In order to prevent outliers that may be present in the measured values of the mass m from corrupting the mean value to be formed, the mean value calculated in the block 36 is passed onto a query icon 40 via a branch 38. Here, it is checked whether at least one of the measured values of the mass m differs by a predetermined value from the mean value calculated in block 36.

(19) If this is not the case, a no signal 42 is passed onto a block 44 in which the value to be output for the mass m of the motor vehicle is equated to the previously calculated mean value. The end icon 30 is then reached via a branch 46.

(20) If, however, it is recognized from the query icon 40 that at least one measured value for the mass m differs from the mean value, a yes signal 48 is passed on to a further query icon 50. It is checked here whether only one measured value for the mass m differs significantly from the mean value.

(21) If this is not the case, that is to say if more than one measured value differs significantly from the mean value, a no signal 52 is passed on to a block 54 in which the measured values for the mass m for said measurement path are discarded. The end icon 30 is subsequently reached via a branch 56, and the method can be started again.

(22) In the case when only one measured value for the mass m differs significantly from the mean value, the query icon 50 passes on a yes signal 58 to a block 60. A new mean value is then calculated in the block 60 taking account of the variance from two remaining measured values of the mass m, that is to say the measured value which differs significantly from the previously calculated mean value is discarded.

(23) The newly determined mean value is passed on by a branch 62 to a block 64, in which the value to be output for the mass m of the motor vehicle is equated to the newly determined mean value. The end icon 30 is then reached via a branch 66.

(24) Once the end icon 30 is reached, the means 12 illustrated in FIG. 1 for determining a mean value of the previously determined value to be output for the mass m of the motor vehicle is output as averaged vehicle mass {circumflex over (m)}. Said estimated value {circumflex over (m)} of the vehicle mass is preferably made available as input variable to a control algorithm of the motor vehicle. This can, for example, be an ABS or EBS controller. However, further controllers for which the vehicle mass is of interest are also possible to conceive.

(25) A possible application of the method explained in accordance with FIG. 2 is the recognition of outliers in the estimation of the vehicle mass m. However, the method for forming a mean value can be applied in order to improve the accuracy of any static vehicle parameter. In this case, the parameters can be measured or be estimated by means of suitable algorithms. The accuracy of the vehicle parameters is advantageously improved with the method according to the invention by relatively simple calculation steps.

(26) Since the calculation of the mass m of the motor vehicle is based according to the invention on the drive power P.sub.A, the determination of the tractive force is advantageously eliminated. The method according to the invention can advantageously be used in the case of motor vehicles having conventional drivetrains as well as all-wheel and hybrid drives.

(27) All the features named in the above description and in the claims can be combined both individually and in any desired combination with the features of the independent claims. The disclosure of the invention is therefore not limited to the combinations of features described and/or claimed. However, all reasonable combinations of features within the scope of the invention have to be regarded as disclosed. While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.

LIST OF REFERENCE SYMBOLS (PART OF THE DESCRIPTION)

(28) 2 Calculating means 4 Means for determining the speed v 6 Means for determining the drive power P.sub.A 8 Means for determining the power P.sub.R for overcoming the driving resistances 10 Timer 11 Recursive estimation algorithm 12 Means for determining a mean value 22 Connecting branch 24 Query icon 26 No signal 28 Block (wait) 30 End icon 32 Connecting branch 34 Yes signal 36 Block (mean value) 38 Branch calculated mean value 40 Query icon (outliers) 42 No signal 44 Block (assignment) 46 Branch to the end icon 48 Yes signal 50 Query icon 52 No signal 54 Block (discard measured values) 56 Branch to the end icon 58 Yes signal 60 Block (mean value) 62 Branch mean value 64 Block (assignment) 66 Branch to the end icon F.sub.L Air resistance of the motor vehicle F.sub.R Rolling resistance of the motor vehicle F.sub.St Slope resistance of the motor vehicle m Mass of the motor vehicle {circumflex over (m)} Mean value of the mass m M.sub.eng Drive torque of the engine M.sub.fric Frictional torque of the engine n Wheel rotational speed signal P.sub.A Drive power P.sub.A0 Drive power at instant t=0 P.sub.A1 Drive power at instant t=1 P.sub.R Power for overcoming the driving resistances t.sub.0 First instant t.sub.1 Second instant v Speed of the motor vehicle v.sub.0 Speed at instant t=0 v.sub.1 Speed at instant t=1 Parameterized efficiency of the drivetrain .sub.eng Angular velocity of the engine