Method and control unit for determining an angle between longitudinal axes of component vehicles of a tractor-trailer combination

A method for determining an angle between a longitudinal axis of a first, leading component vehicle and a longitudinal axis of a second, trailing component vehicle. For at least one wheel axle or wheel axle group of the first, leading component vehicle a travel speed and/or an angular speed of the wheel axle or wheel axle group concerned is determined, and for at least one wheel axle or wheel axle group of the second, trailing component vehicle a travel speed and/or an angular speed of the wheel axle or wheel axle group concerned is determined. From the travel speeds and/or angular speeds determined for the wheel axles or wheel axle groups of the first, leading component vehicle and of the second, trailing component vehicle, the angle between the longitudinal axes of the first, leading component vehicle and the second, trailing component vehicle is then calculated.

FIELD OF THE INVENTION

The invention concerns a method for determining an angle between longitudinal axes of a tractor-trailer combination of component vehicles and a control unit for implementing the method.

BACKGROUND OF THE INVENTION

For the operation of tractor-trailer combinations consisting of a number of component vehicles, the component vehicles of which are not rigidly connected but, rather, articulated to one another by a coupling, it is important in various operating situations to know the angle enclosed by the longitudinal axes of the component vehicles of the tractor-trailer combination, for example during maneuvering, parking, starting off and braking. Until now a simple and accurate determination of such an angle between the longitudinal axes of the component vehicles of a tractor-trailer combination consisting of a number of articulated component vehicles has presented difficulties.

From DE 10 2013 013 584 A1 it is known to determine an angle between a trailer and a tractor of an articulated tractor-trailer combination by a no-contact measurement technique. For that purpose sensors are built into the trailer, these sensors being in the form of near-field radar sensors, ultrasonic sensors, light sensors or Lidar sensors.

A further method with the help of which an angle between longitudinal axes of the component vehicles of an articulated tractor-trailer combination can be determined, is known from DE 10 2008 057 027 A1. According to this a special sensor system is again used, by means of which the relative position between the component vehicles of the tractor-trailer combination can be determined. In this case the sensor system comprises two rangefinders.

SUMMARY OF THE INVENTION

Starting from there, the purpose of the present invention is to provide a new type of method for determining an angle between longitudinal axes of a tractor-trailer combination of component vehicles, as well as a control unit for implementing the method.

That objective is achieved by a method as described below.

According to the invention, for at least one wheel axle or wheel axle group of the first, leading component vehicle a travel speed and/or an angular speed of the wheel axle or wheel axle group concerned is determined, and for at least one wheel axle or wheel axle group of the second, trailing component vehicle a travel speed and/or an angular speed of the wheel axle or wheel axle group concerned is determined, and from the determined travel speeds and/or angular speeds of the wheel axles or wheel axle groups of the first, leading component vehicle and of the second, trailing component vehicle the angle between the longitudinal axes of the first, leading component vehicle and the second, rear component vehicle is calculated.

With the method according to the invention it is possible, on the basis of travel speeds and/or angular speeds of the wheel axles or wheel axle groups of the component vehicles of the vehicle tractor-trailer combination, to calculate the angle between the longitudinal axes of the component vehicles. The method according to the invention does not need any special system of sensors for determining the angle between the longitudinal axes of the component vehicles. Rather, the travel speeds and/or angular speeds of the wheel axles or wheel axle groups of the component vehicles can be determined from data which are in any case available for control purposes, in particular from wheel rotation speeds of the wheels of the respective wheel axle or wheel axle group and if necessary from a travel speed and a steering angle of a steered axle of the vehicle tractor-trailer combination.

According to a first advantageous further development of the invention the angle α between the longitudinal axes of the first, leading component vehicle and the second, rear component vehicle is calculated from the travel speeds and angular speeds using the following equation:

tan⁡(αi)=vi+1*Li,K⁢⁢2*ωi-vi*Li+1,K⁢⁢1*ωi+1vi+1*vi+Li,K⁢⁢2*Li+1,K⁢⁢1*ωi+1*ωi
in which vi+1is the travel speed and ωi+1is the angular speed of a wheel axle or wheel axle group of the first, leading component vehicle, viis the travel speed and ωiis the angular speed of a wheel axle or wheel axle group of the second, trailing component vehicle, Li+1,K1is a geometrical dimension of the first, leading component vehicle, Li,K2is a geometrical dimension of the second, rear component vehicle, and i is a count variable.

By using the above, generally valid equation, the travel speeds and angular speeds of axles or wheel axle groups of two adjacent, coupled component vehicles of a vehicle tractor-trailer combination can be used to compute the angle between the longitudinal axes of the component vehicles in a simple and reliable manner.

According to a second, alternative advantageous further development of the invention the angle α between the longitudinal axes of the first, leading component vehicle and the second, trailing component vehicle can be calculated from the angular speeds determined using the following equation:
α=∫(ωi+1−ωi)dt+α0
in which ωi+1is the angular speed of a wheel axle or wheel axle group of the first, leading component vehicle, ωiis the angular speed of a wheel axle or wheel axle group of the second, trailing component vehicle, and α0is an initialization value.

With this further development of the invention as well, the angle between the longitudinal axes of two adjacent, coupled component vehicles of a vehicle tractor-trailer combination can be computed, but this further development of the invention uses the angular speeds of the wheel axles or wheel axle groups of the component vehicles of the tractor-trailer combination exclusively, but not their travel speeds. However, an initialization value is required, which for the exact determination of the angle between the longitudinal axes of the component vehicles of the tractor-trailer combination must be known as precisely as possible and/or initialized from time to time when defined operating conditions of the tractor-trailer combination exist.

The control unit according to the invention is also described below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention concerns a method and a control unit for determining an angle between longitudinal axes of a tractor-trailer combination consisting of a plurality of component vehicles.

Below, the invention is described with reference to example embodiments in which the component vehicles are articulated mechanically. However, the invention can also be used when the component vehicles of a tractor-trailer combination are coupled virtually.

FIG. 1shows a first example of a tractor-trailer combination comprising coupled component vehicles1,2, namely a trailing component vehicle1and a leading component vehicle2. In the example embodiment shown the trailing component vehicle1has two non-steered and non-rotating wheel axles3,4, which form a wheel axle group5. The leading component vehicle2has a rear wheel axle6and a front wheel axle7, the rear wheel axle6being a non-steered and non-rotating wheel axle whereas in contrast the front wheel axle7of the leading component vehicle2is a steered and non-rotating axle. The term non-rotating wheel axle should be understood to mean a wheel axle the orientation of whose longitudinal axis relative to the longitudinal axis of the component vehicle concerned is fixed, in contrast to a drawbar axle, and can consequently not be rotated about a vertical axis.

The two component vehicles1and2are mechanically articulated to one another at a coupling point8, so that during driving operation the orientation or relative positions of the two component vehicles can change.

FIG. 2shows a single-track model for the tractor-trailer combination ofFIG. 1, wherein the two-track wheel axle group5and the two-track wheel axles6,7are in each case reduced to a single track, namely in such manner that the virtual, single-track wheel axle group5lies on a longitudinal central axis9of the trailing component vehicle1and the virtual, single-track wheel axle6of the leading component vehicle2lies on a longitudinal central axis10thereof. The longitudinal central axes9and10of the component vehicles1and2of the tractor-trailer combination enclose an angle α. In addition,FIG. 2shows an angle β that corresponds to the steering angle of the steered axle7of the leading component vehicle2.

The value v1is the travel speed of the wheel axle group5of the trailing component vehicle1. The value ω1is the angular speed of this wheel axle group5. The value v2is the travel speed of the wheel axle6of the leading component vehicle2. The value ω2is the angular speed of this wheel axle6. The value v corresponds to the travel speed of the steered wheel axle7of the leading component vehicle. In additionFIG. 2shows a number of characteristic geometrical dimensions of the tractor-trailer combination represented byFIG. 1, namely the dimension L1,K2being the distance of the wheel axle group5of the trailing component vehicle1from the coupling point8of the two component vehicles1,2, the dimension L2,K1being the distance of the wheel axle6of the leading component vehicle2from the coupling point8, and the dimension L2,K2being the distance between the two wheel axles6,7of the leading component vehicle2.

The tractor-trailer combination represented inFIGS. 1 and 2can be, for example, a tractor-trailer unit with a tractor vehicle and a semi-trailer. Furthermore, the tractor-trailer combination represented inFIGS. 1 and 2can be an articulated bus or a passenger car with a trailer.

A further tractor-trailer combination with two mechanically articulated component vehicles1,2is shown inFIG. 3, whileFIG. 4shows a single-track model for this tractor-trailer combination. InFIGS. 3 and 4the leading component vehicle2again has a non-steered and non-rotating rear wheel axle6and a steered, non-rotating front wheel axle7. The trailing component vehicle1has a rear, non-steered and non-rotating wheel axle3and in addition a rotatable drawbar axle11. The two component vehicles1,2are coupled to one another at the coupling point8by means of a so-termed drawbar of the drawbar axle11.

It can be seen fromFIG. 4that the single-track model for the tractor-trailer combination ofFIG. 3has two significant angles α1and α2, namely the angle α1between the longitudinal central axis9of the trailing component vehicle1and the drawbar axis12of the drawbar, and the angle α2between the drawbar axis12and the longitudinal central axis10of the leading component vehicle2. InFIG. 4the values v1and ω1are, respectively, the travel speed and angular speed of the wheel axle3of the trailing component vehicle1. The values v3and ω3are the travel speed and angular speed of the rear wheel axle6of the leading component vehicle2. The values v2and ω2are the travel speed and angular speed of the drawbar axle11. InFIG. 4the geometrical dimension L1,K2corresponds to the distance between the rear wheel axle3and the front drawbar axle11of the trailing component vehicle1. The dimension L2,K2corresponds to the distance between the drawbar axle11and the coupling point8. The dimension L3,K1corresponds to the distance between the coupling point8and the rear wheel axle6of the leading component vehicle2.

The tractor-trailer combination inFIGS. 3 and 4can for example be a tractor-trailer combination of a truck and a trailer with a drawbar, or a tractor-trailer combination of an agricultural tractor and an agricultural trailer with a drawbar.

FIG. 5shows a further tractor-trailer combination of two component vehicles1,2coupled at a coupling point8, such that inFIG. 5the trailing component vehicle1has two non-steered, non-rotating wheel axles3,4that form a wheel axle group5, and such that the leading component vehicle2as well has two non-steered, non-rotating wheel axles13,14that form a wheel axle group15. The tractor-trailer combination inFIG. 5can for example consist of two coupled trailers, so that the leading trailer2can then be coupled to a tractor vehicle (not shown).

FIG. 6shows the single-track model for the tractor-trailer combination inFIG. 5, wherein the longitudinal central axes9,10of the two component vehicles1,2again enclose an angle α. The values v1and ω1are, respectively, the travel speed and the angular speed of the wheel axle group5, whereas the values ω2and v2are, respectively, the angular speed and the travel speed of the wheel axle group15. The geometrical dimension L1,K2corresponds to the distance between the wheel axle group5of the trailing component vehicle1and the coupling point8, whereas the geometrical dimension L2,K1corresponds to the distance between the coupling point8and the wheel axle group15of the leading component vehicle2.

FIG. 7shows an abstracted, generalized single-track model for a tractor-trailer combination of mechanically or virtually coupled component vehicles, such that the model ofFIG. 7is used twice in the model ofFIG. 4, namely on the one hand to determine the angle α1between the longitudinal central axis9of the trailing component vehicle1and the drawbar axis12, and on the other hand to determine the angle α2between the drawbar axis12and the longitudinal central axis10of the leading component vehicle2. In the abstracted, generalized single-track model shown inFIG. 7the travel speeds v, angular speeds ω and geometrical dimensions L of the trailing component vehicle are characterized by the subscript index i and the travel speeds, angular speeds and geometrical dimensions of the leading component vehicle are characterized by the subscript index i+1. Furthermore, in the generalized single-track model ofFIG. 7it is assumed that both on the trailing component vehicle and also on the leading component vehicle there are respective coupling points8iand8i+1.

In order, now, to determine the angle between the longitudinal axes of the coupled component vehicles of a tractor-trailer combination, namely by using the abstract single-track model inFIG. 7, for at least one wheel axle and/or wheel axle group of the leading component vehicle concerned a travel speed vi+1and an angular speed ωi+1of the wheel axle or wheel axle group concerned are determined. In addition, for at least one wheel axle or wheel axle group of the trailing component vehicle a travel speed viand an angular speed ωiof the wheel axle or wheel axle group concerned are determined. From these determined travel speeds viand vi+1and angular speeds ωiand ωi+1of the wheel axles or wheel axle groups of the leading and trailing component vehicles, the angle α between the longitudinal axes of the component vehicles is then calculated.

For this, the angle α between the longitudinal axes of the component vehicles is calculated as a function of the travel speeds viand vi+1and angular speeds ωiand ωi+1determined, with reference to the generalized single-track model ofFIG. 7, using the following equation:

tan⁡(αi)=vi+1*Li,K⁢⁢2*ωi-vi*Li+1,K⁢⁢1*ωi+1vi+1*vi+Li,K⁢⁢2*Li+1,K⁢⁢1*ωi+1*ωi
in which vi+1is the travel speed and ωi+1the angular speed of a wheel axle or wheel axle group of the first, leading component vehicle, viis the travel speed and ωiis the angular speed of a wheel axle or a wheel axle group of the second, trailing component vehicle, Li+1,K1is a geometrical dimension of the first, leading component vehicle, Li,K2is a geometrical dimension of the second, trailing component vehicle, and i is a count variable.

If the generalized single-track model and the above equation are applied in the special case ofFIGS. 1 and 2, namely for a tractor-trailer combination with no drawbar consisting of the leading component vehicle2and the trailing component vehicle1, wherein the leading component vehicle2has the front, non-rotating but steered wheel axle7and the rear, non-rotating and non-steered wheel axle8, and wherein the trading component vehicle1has exclusively the non-rotating and non-steered wheel axle group5, then the index i=1 in the above generalized formula for the generalized single-track model shown inFIG. 7, and the angle α between the longitudinal axes9and10of the two component vehicles1and2is calculated from the following equations:

If the generalized equation for the single-track model inFIG. 7is applied in the special case, shown inFIG. 3, of a tractor-trailer combination of the two component vehicles1and2coupled by way of a drawbar axle11of the trailing component vehicle1, in which the drawbar axle11is the front axle of the trailing component vehicle1and in which the trailing component vehicle1comprises the rear, non-steered and non-rotating wheel axle3and the leading component vehicle2comprises the rear, non-steered and non-rotating wheel axle6, then the index i=2 and the angle α between the longitudinal axes9and10of the tractor-trailer combination inFIGS. 3 and 4can be calculated using the following equations:

In the tractor-trailer combination shown inFIGS. 5 and 6as well, in the manner described above the angle α between the longitudinal axes of the component vehicles9and10of the tractor-trailer combination inFIGS. 5 and 6can be calculated from the travel speeds and angular speeds of the wheel axle groups5and15; in this case the index i=1 and the following equations are used:

In the above equations, used to determine the angle between coupled component vehicles of a tractor-trailer combination, the respective travel speeds and angular speeds of wheel axles or wheel axle groups are involved. In this case the travel speed of a wheel axle or wheel axle group or drawbar axle of a component vehicle is determined from the wheel speeds of the wheels of the wheel axle or wheel axle group or drawbar axle concerned, in accordance with the following equation:

vi=1N⁢∑j=1N⁢⁢vi-RAD,j
in which viis the travel speed of the wheel axle or wheel axle group or drawbar axle, and vi-RADjis the wheel speed of the j-th wheel of the wheel axle or wheel axle group or drawbar axle.

Thus, in this way the wheel speeds of all the wheels on a wheel axle or wheel axle group are averaged in order to determine the travel speed of the wheel axle or wheel axle group or drawbar axle concerned. The wheel speeds of all the wheels on a wheel axle or wheel axle group or drawbar axle are preferably calculated from measured wheel rotation speed values of the wheels on a wheel axle or wheel axle group or drawbar axle.

The angular speed of a wheel axle or wheel axle group or drawbar axle of a component vehicle is determined from the wheel speeds of the wheels of the wheel axle or wheel axle group or drawbar axle concerned, preferably in accordance with the following equation:

ωi=vi⁢-⁢RAD,RECHTS-vi⁢-⁢RAD,LINKSd
in which ωiis the angular speed of the wheel axle or wheel axle group or drawbar axle concerned, vi-RAD,RECHTSand vi-RAD,LINKSare wheel speeds of a right and a left wheel on the wheel axle or wheel axle group or drawbar axle, and d is the distance between the left and right wheels of the wheel axle or wheel axle group or drawbar axle.

In the case of a wheel axle group having several left and right wheels, the wheel speeds of the left wheel and the right wheel are in each case the wheel speeds determined for all the left wheels and all the right wheels of the wheel axle group concerned.

If, for example for the tractor-trailer combination shown inFIGS. 1 and 2or, for that matter, the tractor-trailer combination shown inFIGS. 3 and 4, no wheel speeds of the wheels on the rear wheel axle6of the leading component vehicle2are available, the travel speed and the angular speed of the rear axle6of the leading component vehicle2can be calculated from the steering angle β and the travel speed v of the steered front axle7of the leading component vehicle2, for the tractor-trailer combination inFIGS. 1 and 2preferably using the following equation:

If an appropriate sensor system is present in the tractor-trailer combination, the travel speeds and angular speeds of the wheel axles, wheel axle groups or drawbar axles calculated as above can be further verified, for example from speeds derived from radar or GPS measurements, or angular speeds determined with the help of yaw-rate sensors. However, that is purely optional: the invention can also be used without any additional sensors to determine the angle between longitudinal axes of the component vehicles of a tractor-trailer combination.

According to an alternative design of the invention it is provided that the angle between the longitudinal axes of component vehicles of a tractor-trailer combination can be determined exclusively on the basis of angular speeds of the wheel axles, wheel axle groups or drawbar axles, preferably using the following equation:
α=∫(ωi+1−ωi)dt+α0
in which ωi+1is the angular speed of a wheel axle or wheel axle group of the first, leading component vehicle, ωiis the angular speed of a wheel axle or wheel axle group of the second, trailing component vehicle and α0is an initialization value.

In this case, to avoid an integration error it is important to have as precise a knowledge as possible of the initialization value α0. The initialization value α0corresponds to that angle between the longitudinal axes of the component vehicles which they enclose at the beginning of the numerical integration in accordance with the above equation.

In order to determine this initialization value α0as accurately as possible, it can be provided that the initialization value α0is determined afresh from time to time under particular operating conditions.

For example, it can be provided that when, for example on the basis of GPS information it is known that the tractor-trailer combination is operating on a straight stretch of road and when, furthermore, the time span during which the vehicle drives on the straight stretch is longer than a limit value, the initialization value α0is set to zero. The limit value for the time span depends on the total length of the tractor-trailer combination and its travel speed, and can for example be determined from the following equation:

T=k*lv
in which T is the limit value for the time span concerned, I is the total length of the tractor-trailer combination, v is the speed of the tractor-trailer combination and k is a constant, such that k can for example equal 3.

Alternatively, when for a defined time span the steering angle β=0, it can be assumed that the tractor-trailer combination is operating on a straight stretch, and then the initialization value α0is again set to zero.

The present invention also concerns a control unit for implementing the method. The control unit comprises means for carrying out the method according to the invention. The means include both hardware means and software means. The hardware means are data interfaces in order to exchange data with the assemblies involved in implementing the method according to the invention. In addition, the hardware means include a processor and a memory, the memory serving to store data and the processor serving for data processing. The software means consist of program modules for implementing the method according to the invention.

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