METHOD FOR DETERMINING AN ACTUAL MASS OF A VEHICLE, CONTROL SYSTEM IMPLEMENTING SUCH A METHOD, AND VEHICLE COMPRISING SUCH A CONTROL SYSTEM

Abstract

A method for determining an actual mass of a vehicle, includes: determining a reference relationship of a deceleration of the vehicle having a known mass with respect to a brake demand; executing braking with a predetermined brake demand; detecting an actual deceleration of the vehicle when using the predetermined brake demand; determining an actual relationship of the actual deceleration of the vehicle with respect to the predetermined brake demand; and determining the actual mass of the vehicle by correlating the actual relationship and the reference relationship.

Claims

1-15. (canceled)

16. A method for determining an actual mass of a vehicle, the method comprising: determining a reference relationship of a deceleration of the vehicle having a known mass with respect to a brake demand; executing braking with a predetermined brake demand; detecting an actual deceleration of the vehicle when using the predetermined brake demand; determining an actual relationship of the actual deceleration of the vehicle with respect to the predetermined brake demand; and determining the actual mass of the vehicle by correlating the actual relationship and the reference relationship.

17. The method of claim 16, wherein the reference relationship is determined by performing the following: determining a reference mass of the vehicle; executing a reference braking of the vehicle with a predetermined brake demand; detecting a deceleration of the vehicle having the reference mass depending on the predetermined brake demand; and determining the reference relationship by correlating the deceleration of the vehicle and the predetermined brake demand.

18. The method of claim 16, wherein the reference relationship of the deceleration of the vehicle is determined based on an official minimum requirement for a relationship of the deceleration of the vehicle and the brake demand.

19. The method of claim 16, wherein a range of the brake demand is determined such that the reference relationship and the actual relationship are respectively linear and expressed by a slope of a straight line in a diagram having an abscissa indicating the brake demand and an ordinate indicating the deceleration, and wherein the actual mass is calculated based on the reference mass, a slope of a straight line expressing the reference relationship, and a slope of a straight line expressing the actual relationship.

20. The method of claim 19, wherein the range of the brake demand is defined such that no blocking of wheels of the vehicle occurs.

21. The method of claim 16, wherein the brake demand is defined by a brake actuation force of a brake of the vehicle.

22. The method of claim 16, wherein the brake demand is defined by a pressure of an operating fluid actuating on a brake actuator of a brake of the vehicle.

23. The method of claim 22, wherein the pressure is an output pressure of a trailer control module.

24. The method of claim 16, wherein the brake demand is defined by an operating current of an electric brake actuator of a brake of the vehicle.

25. The method of claim 24, wherein the operating current is based on an electrical brake demand or an electrical trailer brake demand sent by a towing vehicle.

26. The method of claim 16, wherein the known mass is a maximum permissible mass of the vehicle.

27. The method of claim 16, wherein the actual deceleration of the vehicle is detected by means of a wheel-based vehicle speed signal.

28. A control system for determining an actual mass of a vehicle, comprising: a control apparatus configured to perform the following: determining a reference relationship of a deceleration of the vehicle having a known mass with respect to a brake demand; executing braking with a predetermined brake demand; detecting an actual deceleration of the vehicle when using the predetermined brake demand; determining an actual relationship of the actual deceleration of the vehicle with respect to the predetermined brake demand; and determining the actual mass of the vehicle by correlating the actual relationship and the reference relationship.

29. The control system of claim 28, wherein the control system includes an acceleration sensor configured to detect an acceleration in direction of travel of the vehicle.

30. A vehicle, comprising: a control system for determining an actual mass of a vehicle, wherein the control system is configured to perform the following: determining a reference relationship of a deceleration of the vehicle having a known mass with respect to a brake demand; executing braking with a predetermined brake demand; detecting an actual deceleration of the vehicle when using the predetermined brake demand; determining an actual relationship of the actual deceleration of the vehicle with respect to the predetermined brake demand; and determining the actual mass of the vehicle by correlating the actual relationship and the reference relationship.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 shows a principle illustration of a vehicle according to the invention.

[0040] FIG. 2 shows a diagram illustrating various relationships of a deceleration with respect to a brake demand.

[0041] FIG. 3 shows a flowchart of a method for determining an actual mass of a vehicle according to the invention.

[0042] FIG. 4 shows a flowchart of a method for determining a reference relationship.

DETAILED DESCRIPTION

[0043] FIG. 1 shows a principle illustration of a vehicle 1, in particular a towing vehicle. The vehicle 1 comprises four wheels 2 respectively provided with a brake 3. The brakes 3 are respectively provided with a brake actuator 4 which is actuated by an operating fluid having an adjustable pressure. In an alternative embodiment, the vehicle 1 consists of a vehicle combination of tractor unit and a trailer or of another combination. In further alternative embodiments, the brake actuators 4 respectively comprise an electromechanical brake actuator and are actuated by electric current.

[0044] The vehicle 1 further comprises a control system 5 configured to implement a method according to the invention. Additionally, the vehicle 1 comprises an acceleration sensor 6 configured to detect a deceleration of the vehicle 1 in a direction of travel d of the vehicle 1. In alternative embodiments, the vehicle 1 is not provided with the acceleration sensor 6 but with a velocity sensor and a device for detecting time, and the deceleration of the vehicle 1 is determined from a wheel-based vehicle speed signal, e.g., used by a brake control system or another vehicle control system.

[0045] FIG. 2 shows a diagram illustrating various relationships of a deceleration Ax with respect to a brake demand bd. The diagram has an abscissa indicating the brake demand bd and an ordinate indicating the deceleration Ax of the vehicle 1 in the direction of travel d of the vehicle 1.

[0046] Three straight lines L.sub.1, L.sub.2, L.sub.3 indicate three different relationships of a respective deceleration Ax of the vehicle 1 with respect to the brake demand bd for three different masses m.sub.1, m.sub.2, m.sub.3 or weights of the vehicle 1.

[0047] As long as no wheel 2 is blocking, the deceleration Ax of the vehicle 1 is directly proportional to a braking force, in particular, to a sum of braking forces of the brakes 3, more particularly to a sum of actuation forces generated by the brake actuators 4 [A.sub.x=f(F.sub.br)]. It can be assumed that the actuation force of the brakes 3 is directly proportional to a brake demand bd and, therefore, the deceleration A.sub.x is directly proportional to the brake demand bd. Thus, the relationships are respectively indicated by straight lines, in particular, the straight lines L.sub.1, L.sub.2, L.sub.3 for the different masses m.sub.1, m.sub.2, m.sub.3.

[0048] The brake demand bd defines the brake actuation force of the brake 3 of the vehicle 1. In particular, the brake demand bd is defined by a pressure of the operating fluid actuating on the brake actuator 4 of the brake 3. In alternative embodiments, an output pressure of a foot brake valve of the vehicle 1 or an output pressure of a trailer control module or valve is used for the determination of the relationship. In further alternative embodiments, with the electromechanical brake actuator, the brake demand and, therefore, the brake actuation force are defined by an operating current of an electric brake actuator 4 of the brake 3 of the vehicle 1, or by an electrical brake demand in the vehicle 1 or an electrical trailer brake demand sent by a towing vehicle, in particular, via a bus system, more particular, via a communication network like CAN specified in ISO 11992.

[0049] Since, as mentioned above, the deceleration A.sub.x is directly proportional to the brake actuation force as long as no wheel 2 is blocking, the range of the brake demand is defined such that no blocking of the wheels 2 of the vehicle 1 occurs. In alternative embodiments, the range is defined such that blocking of the wheels 2 can occur, however, the range in which blocking occurs is excluded from the determination of the actual mass.

[0050] Based on the straight lines L.sub.1, L.sub.2, L.sub.3 defining the relationship of the deceleration A.sub.x of the vehicle 1 with respect to the brake demand bd, the relationship can be indicated by a slope .sub.i of the straight lines L.sub.1, L.sub.2, L.sub.3.

[00001]$\begin{array}{cc}{}_1{m}_1={}_2{m}_2={}_3{m}_3={}_i{m}_i& \left(1\right)\end{array}$ [0051] wherein m.sub.i is a mass (or corresponds to a weight) of the vehicle and m.sub.1>m.sub.2>m.sub.3.

[0052] From the diagram, it is to be seen that the lower the mass, the greater the deceleration for an identical defined brake demand bd.

[0053] When a reference slope .sub.r of a straight line is determined for a known reference mass m.sub.r in advance as a reference relationship, the actual mass m.sub.a can be determined by correlating of the actual slope .sub.a, i.e., the actual relationship, and the reference slope .sub.r. In particular, the actual mass m.sub.a can be calculated by the equation

[00002]$\begin{array}{cc}{m}_a=m_r\frac{{}_r}{{}_a}& \left(2\right)\end{array}$ [0054] wherein [0055] m.sub.a is the actual mass, [0056] m.sub.r is the reference mass. [0057] .sub.a is the actual slope, and [0058] .sub.r is the reference slope.

[0059] FIG. 3 shows a flowchart of a method for determining an actual mass of a vehicle according to the invention.

[0060] In use, in step S1, a reference relationship of a deceleration Ax of the vehicle 1 having a known mass, i.e., the reference mass m.sub.r, and, therefore, a known weight, is determined with respect to a brake demand bd in advance. This reference relationship is determined by test measurements and it is indicated by the slope .sub.r. The known mass is selected as to be a maximum permissible mass of the vehicle 1 in order to achieve a result as exact as possible, nevertheless, in alternative embodiments, also known masses less than the maximum permissible mass of the vehicle 1 are possible.

[0061] Then, in step S2, a braking with a predetermined brake demand is executed and, in step S3, an actual deceleration of the vehicle 1 when using the predetermined brake demand is detected.

[0062] Subsequently, in step S4, the actual relationship of the actual deceleration of the vehicle 1 with respect to the predetermined brake demand is determined and indicated as the actual slope .sub.a.

[0063] A range of the brake demand is determined such that the reference relationship and the actual relationship are respectively linear, particularly such that no blocking of the wheels 2 of the vehicle 1 occurs. Alternatively, the range of the brake demand is determined such that also non-linear relationships are possible, however, such sub-ranges are excluded from the determination of the slope .sub.r.

[0064] Finally, in step S5, the actual mass m.sub.a of the vehicle 1 is determined by correlating the actual relationship and the reference relationship, in particular, calculated by the above-described equation 2.

[0065] FIG. 4 shows a flowchart of a method for determining a reference relationship. In step S1.1, a reference mass m.sub.r of the vehicle 1 is determined. This determination is performed by weighing the vehicle 1 or, alternatively, by calculating based on known information.

[0066] Further, in step S1.2, a reference braking of the vehicle 1 with a predetermined brake demand bd is executed. For an enhanced determination, multiple reference brakings with different predetermined braking demands bd are executed. In step S1.3, the deceleration of the vehicle 1 having the reference mass m.sub.r is detected depending on the predetermined brake demand bd and, in step S1.4, the reference relationship is determined by correlating the deceleration Ax of the vehicle 1 and the brake demand bd.

[0067] Alternatively, the reference relationship is calculated based on known characteristics of the vehicle, in particular, based on the reference mass m.sub.r, further alternatively, by a brake performance calculation, or based on an official minimum requirement for a relationship of the deceleration of the vehicle 1 and the brake demand. Using the minimum requirement for the relationship means that relationship is determined based on the minimum relationship of, e.g., a pressure of an operating fluid and a relationship of a sum of brake forces and a normal force of a lane, which minimum relationship directly corresponds to the deceleration of the vehicle 1 in a range without blocking wheels 2. The official minimum requirements are disclosed in, e.g., the Regulation No 13 of the Economic Commission for Europe of the United Nations (UN/ECE) ECE R 13, Revision 8 or Federal Motor Vehicle Safety Standard No. 121 FMVSS No. 121, issued on Oct. 1, 2011.

[0068] Although the present invention has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations combinations or equivalents that fall within the scope of the present invention.

THE LIST OF REFERENCE SIGNS IS AS FOLLOWS

[0069] 1 vehicle [0070] 2 wheel [0071] 3 brake [0072] 4 brake actuator [0073] 5 control system [0074] 6 acceleration sensor [0075] Ax deceleration [0076] bd brake demand [0077] d direction of travel [0078] m.sub.a actual mass [0079] m.sub.r reference mass [0080] m.sub.i mass of vehicle [0081] .sub.a actual slope [0082] .sub.i slope [0083] .sub.r reference slope