WO2009083221A1

WO2009083221A1 - Method for actuating a traction drive

Info

Publication number: WO2009083221A1
Application number: PCT/EP2008/011026
Authority: WO
Inventors: Matthias Müller; Peter Schmuttermair
Original assignee: Robert Bosch Gmbh
Priority date: 2007-12-28
Filing date: 2008-12-22
Publication date: 2009-07-09
Also published as: DE102008025683B4; DE102008025683A1

Abstract

The invention relates to a method for actuating a traction drive (1) having a primary drive machine (2) and a hydrostatic transmission (3) connected thereto. Initially, a position of a driving command setting unit (13) is detected. An operating point for a primary drive machine (2) is determined on the basis of the position of the driving command setting unit (13) that is determined. Further, a setting of the hydrostatic transmission (3) is determined. An initial target torque of the traction drive (1) is determined on the basis of the position of the driving command setting unit (3), from which a required drive output of the primary drive machine (2) is determined. The operating point of the primary drive machine (2) is established on the basis of the required drive output.

Description

Method for controlling a traction drive

The invention relates to a method for controlling a traction drive with a primary drive machine and an associated continuously variable transmission.

A method for controlling a hydrostatic drive is known from DE 38 06 194 Al. The control described there is self-learning and processor-controlled. By means of a transmitter, such as an accelerator pedal, a speed for a diesel engine is specified. The control contains adjustable characteristic curves with which a maximum permissible pressure can be set as a function of the given diesel engine speed. Depending on the pressure actually resulting from the load condition, a delivery volume of the hydrostatic pump of the hydrostatic transmission is adjusted.

A problem with the known control is that changes to the characteristics of the control behavior are difficult to implement. Thus, an idling curve of the prime mover must be recorded by the self-learning process. The flexibility is limited to the adaptation of the maximum permissible maximum pressure of the diesel engine.

It is therefore the object of the invention to provide a

To provide control method for a hydrostatic drive, in which a slight intervention in the control characteristic is possible.

The object is achieved by the method having the features of claim 1. In the method according to the invention, a travel command and a vehicle state are first determined to control a traction drive with a continuously variable, in particular a hydrostatic transmission. It is z. B. a position of a Fahrbefehlvorgabevorrichtung and a

Vehicle speed detected. Such a driving command setting device may be a driving lever or an accelerator pedal. From the detected position of the Fahrbefehlvorgabevorrichtung a vehicle target torque and therefrom an operating point for a primary drive machine is determined. At the determined operating point, it is ensured that the primary drive engine generates sufficient power to satisfy the requirements according to driving lever specification. In addition to the operating point, the setting of the hydrostatic transmission, ie their transmission ratio is determined. According to the invention based on the detected position of the

Fahrbefehlvorgabevorrichtung detects a target output torque of the traction drive, from which a required

Drive power and ultimately the operating point of the primary drive machine is determined. Thus, in contrast to the prior art by means of the position of the Fahrbefehlvorgabevorrichtung no longer simply set a target speed for the most designed as a diesel engine primary prime mover. Rather, first a set by an operator driving lever position of a torque request, the target output torque, assigned by the operator. Based on this moment requirement so the

Sollausgangsmoment the traction drive, the required drive power of the primary drive machine is then determined in a second step, which is required to realize the target output torque. Finally, the determined required

Drive power determined according to an operating point of the primary drive machine. In particular, in diesel internal combustion engines, there is no direct relationship between the position of Driving command setting device and a target speed of the diesel engine. Rather, the operating point is determined from the characteristic diagram of the diesel internal combustion engine, wherein a selection criterion is the previously determined required drive power. The determination of the operating point in the map can thus be made considerably more flexible and in particular take into account areas with particularly favorable fuel consumption. Hereinafter, for the sake of simplicity, only a hydrostatic transmission representative of other continuously variable transmissions is used.

Advantageous developments of the method according to the invention are set forth in the subclaims.

It is advantageous to first determine a vehicle target speed based on a physical model of the drive train or of the entire vehicle from the setpoint output torque of the travel drive. From this vehicle target speed, the transmission ratio of the hydrostatic transmission is then determined. The determination of the transmission ratio of the hydrostatic transmission from the target output torque on the target vehicle speed has the advantage that instead of a complex consideration of an acceleration torque, a simple addition of the actual vehicle speed can be done. This simplifies the calculation and, in particular, the parameterization of the control algorithm.

According to a further preferred embodiment, a value from 0 to a torque resulting from the rated power of the drive machine is assigned to determine the target output torque of the respectively determined position of the drive command setting device. However, this results in a relatively large load sensitivity, since the actual available power at a speed taking into account the suppression of the diesel engine with increasing speed increasingly below the rated power of the diesel engine.

In another particularly preferred embodiment, therefore, each detected position of the

Travel command presetting device assigned a value of 0 to one resulting from the torque at an actual operating point of the prime mover. This ensures in each case that regardless of the position of the driving command setting device for the remaining

Pedalweg or lever travel of Fahrbefehlvorgabevorrichtung the actual available free drive power of the primary drive machine is available. Therefore, at each run command default position, the operator "feels" what additional power the drive machine still provides.

Preferably, a vehicle load torque is also taken into account in determining the transmission ratio of the hydrostatic transmission. The

Vehicle load torque is determined in particular from the suppression of the prime mover. As a push, the deviation of the actual speed from a target speed of the primary drive machine is called. The determination of the vehicle load torque from the suppression of

Drive machine has the advantage that only a deviation of the actual resulting engine speed is required by the predetermined target speed. This is already possible by using a simple speed sensor.

In contrast, according to a further preferred embodiment, the vehicle load torque is read out directly from the control unit of the primary drive machine. However, such an approach is only possible if the

Control unit, for example, the injection system of a diesel engine, a corresponding signal on the vehicle load torque or the actual delivered drive power of the diesel engine provides.

The determination of the vehicle target speed is preferably carried out by integration of an initially determined vehicle target acceleration. In this case, the relationship between the setpoint output torque and the setpoint acceleration is utilized in a particularly simple manner. The calculation of the vehicle target speed by integration of the vehicle target acceleration ensures that virtually the entire determination of the transmission ratio of the hydrostatic transmission can be carried out by calculation. The pressure-controlled adjusting devices, which are required, for example, in an otherwise usual speed-dependent high pressure adjustment, can thus be omitted. The method for controlling the travel drive is thus essentially to be integrated into a control unit and can therefore be easily parameterized.

The transmission ratio for the hydrostatic transmission is finally determined according to the preferred embodiment from the determined by integration vehicle target speed and the actual speed of the primary drive machine. In this way, the ratio of the hydrostatic transmission to be set can also be calculated purely mathematically, with individual characteristics being established for setting the pump pivot angle or the motor pivot angle, starting from the transmission ratio.

It is particularly preferred that the integration of the vehicle target acceleration for determining the target vehicle speed over the entire time since a system start takes place. A preferred embodiment of the method according to the invention will be explained in detail with reference to the figures in the following description. Show it:

FIG. 1 shows a schematic representation of a hydrostatic travel drive used for activation according to the method according to the invention;

FIG. 2 shows an exemplary characteristic diagram for scaling the position of the travel command specification device;

FIG. 3 shows a signal flow diagram for clarification of FIG

Implementation of the method according to the invention;

Figure 4 is an exemplary map of a

Diesel engine running primary prime mover.

FIG. 1 shows, in a schematic representation, a travel drive 1 for carrying out the method according to the invention. The traction drive 1 comprises a primary drive machine, which is designed in the illustrated embodiment as a diesel engine 2. The diesel engine 2 is connected to a hydrostatic transmission 3.

The hydrostatic transmission 3 comprises an adjustable hydraulic pump 4 and a likewise adjustable hydraulic motor 5. The transmission ratio of the hydrostatic

Getriebes 3 is determined by the set volume of the hydraulic pump 4 and the set displacement of the hydraulic motor 5. In the illustrated embodiment, the hydrostatic transmission 3 is realized by connecting the hydraulic pump 4 and the hydraulic motor 5 in a closed circuit. Both hydrostatic machines, which are preferably axial piston machines of the bent axis or swash plate type, are for operation in two opposite flow directions designed. Thus, the direction of travel can be adjusted by changing the conveying direction of the hydraulic pump 4 without the need for a mechanical transmission.

The diesel engine 2 is connected to the hydraulic pump 4 via a drive shaft 6. Instead of the direct drive of the hydraulic pump 4 may also be provided between the diesel engine 2 and the hydraulic pump 4 arranged transmission. The transmission can be designed as a transfer case, which is provided for example a power take-off for driving further possibly also hydraulic consumers.

To drive the vehicle, the hydraulic motor 5 is connected via an output shaft 7 to a driven vehicle axle 8. The representation of the individual driven vehicle axle is merely an example. Likewise, the output shaft 7 may be connected to a further transfer case to realize, for example, a multi-axis drive.

To implement a determined operating point of the diesel engine 2, an injection system 9 is provided. The injection system 9 may for example have its own injection control device, via which the injection quantity of a not explicitly shown injection pump of the injection system 9 is set.

To set the delivery volume of the hydraulic pump 4, a first adjusting device 10 is provided. In a corresponding manner, a second adjusting device 11 is provided for adjusting the absorption volume of the hydraulic motor 5. The first adjusting device 10 and the second adjusting device 11 may be, for example, electro-proportional adjusting devices, as are known for the control of swash plate angles in axial piston machines. By means of a central control unit 12, in which the method according to the invention for driving substantially expires, both the injection system 9 and the first and the second adjusting device 10, 11 of the hydrostatic transmission 3 are activated. For this purpose, 12 default values are determined by the central control unit, which are transmitted via corresponding lines, such as a bus system, to the injection system 9, the first adjustment device 10 and the second adjustment device 11.

The central control unit 12 determines for the diesel engine 2 a by a target speed n _D , _so ii fixed operating point and for the first

Adjustment device 10 and the second adjusting device 11 each have a control signal, for example, for a proportional solenoid in the case of an electro-proportional adjustment of the hydraulic pump 4 and the hydraulic motor fifth

To determine the control signals, a position of a travel command setting device is determined by the central control unit 12. In the illustrated embodiment of Figure 1, the Fahrbefehlvorgabevorrichtung is an accelerator pedal 13. Die

Position of the accelerator pedal 13 is determined via an accelerator pedal sensor 14 and corresponds to a value of 0 to 100%. Further, the central control unit 12, the actual speed n _{D / is} the diesel engine 2 fed. This can be done for example via a correspondingly returned signal of the injection system 9. If such a signal of the injection system 9 is not available, a speed sensor, for example, must be provided on the drive shaft 6 and its signal fed to the central control unit 12. The accelerator pedal 13 can also be adjusted starting from a basic position to -100% and +100%. Furthermore, the vehicle speed v _{ist is determined} by means of a vehicle speed sensor 15. This can, for example, determine the speed of the output shaft 7 and pass it to the central control unit 12, where, taking into account the

Radgetriebeübersetzungen and / or a final drive transmission, the actual vehicle speed Vi _{St is} determined.

To carry out the method _{according to the} _invention , a vehicle _{target torque} M _F2g , _so ii, is first determined for a specific position of the _travel command _{specification device} determined by the position _sensor 14. In general, a vehicle torque is calculated according to the following equation:

(D w M _D.

In this case, M _{Fzg is} the vehicle _torque , M _{0 is} the drive torque of the diesel _{internal combustion engine} ₂ actually supplied to the hydrostatic transmission 3, r is the ratio of the stroke volume of the hydraulic pump V _gP to the displacement of the hydraulic _motor 5 V _gM and i _rad the gear reduction, which is the ratio of the hydrostatic transmission 3 is defined as the speed of the hydraulic motor 5 to the speed of the driven wheel. At the same time, this definition also takes into account an axis ratio.

There are two ways to assign the determined position of the accelerator pedal 13 to a vehicle target torque. In general, the following relationship between the vehicle torque and the power of the primary drive engine is generally used:

(ID

^V Fzg, ιsl ^V Fzg, ιst Where n _Df i _{St is} the actual speed of the primary prime _mover , v _Fzg , _is the actual speed of the vehicle and r _ra d is the radius of the driven wheels. In the right-hand part of the equation, the dependence of the vehicle _torque M _Fzg on the power of the primary drive _machine P _{D can be recognized} , taking into account the power of any additional load P _NV present.

Since with decreasing vehicle _speeds v _FZ g, i _st the

Vehicle torque would go towards infinity, is a limitation of the maximum torque through

Provide pressure relief valves in the hydrostatic transmission 3. This limitation is made according to the equation:

(III)

_* , _ "gMPmsx ■

Fzg.πax _^ rad

Here, M _F2 g, in _a χ the maximum vehicle _torque , V _gM das

Suction volume of the hydraulic motor 5 and p _{max of} the maximum permissible by the pressure relief valves in the closed circuit of the hydrostatic transmission 3 working pressure.

According to a first, simple embodiment, the scaling of the ascertained accelerator pedal position takes place such that when the accelerator pedal is fully depressed (100% position) the vehicle target torque is determined according to the above equation, taking into account the absolute maximum drive power P _D , _ma χ, _{abs of} the diesel internal combustion engine 2. In the rest position of the accelerator pedal 13 (0% position), however, the vehicle target torque M _F2 g _{/ SO} ii is equal to zero. The scaling can z. B. be linear.

In this determination of the position of the accelerator pedal 13 associated vehicle target torque, however, is not considered that the actual available power Pu, max (n _{D /} ig _t ) of the actual speed of Diesel engine 2 and their pressure depends and with increasing pressure is less than the absolute maximum power PD, max, abs of the diesel engine. 2

For this first possibility is in the figure 2 a

Map for scaling the accelerator pedal 13 shown. From the diagram of Figure 2 it can be seen that the accelerator pedal 13, starting from its zero position in two directions can be swung out, which corresponds to a forward drive or a reverse drive. Furthermore, the limitation of the maximum vehicle _torque M _Fzg can be recognized by the pressure relief _valves . The diagram shows the vehicle _{target torque} M _{Fzg / SO} ii predetermined by an operator in each case by means of the accelerator pedal 13 as a function of the vehicle _{actual speed} v _Fzg , i _St.

According to a second, particularly preferred embodiment, the scaling of the vehicle pedal when the accelerator pedal 13 is fully depressed (100% position) does not take into account the rated power of the primary drive machine 2 but rather the drive power actually available at the set operating point. The 100% position of the accelerator pedal 13 is thus assigned a vehicle _{target torque} M _Fzg , _so ii, which takes into account the maximum torque M _D , _m ax available at the actual _{diesel rotational speed} n _D , i _St. In the 0% position of the accelerator pedal 13 is of course again the associated vehicle _{target torque} M _Fzg , _so n is equal to zero. The latter possibility has the advantage that the torque scaling of the usable torque of the

Diesel engine 2 always takes place over the entire accelerator pedal. The residual pedal travel of the accelerator pedal 13 is thus always associated with the still available power reserve of the diesel internal combustion engine 2. Thus, in contrast to the first-mentioned scaling example, there is no dead pedal travel in which an operator changes the accelerator pedal 13 in its position, but no reaction of the vehicle takes place. The sequence of the method according to the invention will be explained below with reference to FIG. First, as already explained above, for each position of the accelerator pedal 13 in the central control unit 12, an associated one

Vehicle _{target torque} M _Fz g, _so ii determined. The scaling is indicated schematically in step 1. In step S2, this vehicle _target torque M _Fz g, _so ii freed from the load torque of the vehicle. In the example shown, the load torque is determined from the depression of the diesel engine 2. For this purpose, initially based on the vehicle target torque M _Fz g, _so ii a target speed n _D , _so u the

Diesel engine 2 determined. This setpoint speed nD, soii is also determined by the central control unit 12 and fed to the injection system 9 of the traction drive 1 as a control variable.

To determine the setpoint speed n _D , _So ii of the diesel engine 2 is first from the vehicle _{target torque} M _Fzg , _so n the implementation of this

Moments required drive power determined (S3). The specification of Solldrehzal n _D , _so n is then based on a map of the diesel engine 2. This will be explained below with reference to Figure 4. After the setpoint speed for the diesel internal combustion engine 2 has been determined in step S4, the actual speed n _D , i _{St of} the diesel internal combustion engine 2 is also determined, for example, by means of a speed sensor, not shown. In step S5, from the target speed n _D , _so n and the actual speed HD, the speed depression Δn _{D is} determined. From the depression Δn _D and the actual diesel rotational speed n _D , i _St , the torque M _{D /} i _St actually generated by the diesel engine 2 is determined on the basis of a known relationship, which is stored as a map in the central control unit 12. Out of that by the

Diesel engine 2 provided torque MD, is taking into account the transmission ratio r of the hydrostatic transmission 3 as well as the wheel speed ratio i _ra d estimated in step S7 and other factors influencing the moment, such as friction losses, a simplified vehicle _{load torque} M _Fzg , _Est , which disregards a proportion of the actual acceleration. This estimated simplified vehicle load Moment M _Fzg, _it t is _so subtracted from the value determined from the accelerator pedal position, vehicle target moment M _Fz g ii, and from the resulting differential torque in step S9 a simplified vehicle target acceleration a'Fzg, soii computed.

This generated torque M _D , i _St corresponds to the drive torque actually provided by the diesel engine to the hydrostatic transmission 3, unless additional consumers are present. In general, the input torque of the hydrostatic transmission 3 corresponds to the following relationship:

(IV)

Here, M _{NV is} the load torque of the secondary consumers and f ((n _D , _{so is} _{D / is} ) p, n _D , i _S t) of the stored as a map

Relationship between the torque generated by the diesel internal combustion engine 2 and the determined diesel fuel injection _ΔnD at a specific diesel engine speed n _D , i _Sf

Generally, the relationship between the

Vehicle _load _moment M _Fzg , _{load given} by the following equation:

(V)

\ A

^ Fzg.Last - ~ ^M T / ° - ^IS ' ^{l ■} rad ^a Fzg, ιst ^mr rad In this case, the first member of the right side gives the simplified vehicle _{load moment} M _{Fzg / ΘSt} and the second member gives an actual part of the load torque of the vehicle on the actual acceleration a _Fz g. Here m is the total vehicle mass and r _rad the radius of the driven wheel.

From the difference between the vehicle _{target torque} M _Fzg , _so u and the vehicle load, a target acceleration a _Fz g, soii be calculated for the vehicle. This takes into account at a difference between the vehicle target torque ^M F _z g, _soll and the vehicle load M _FZ g, _L astf as calculated according to the above equation, also the load component attributable to the acceleration component and is calculated according to the following relationship:

(VI)

^M Fzg, soU ~ - ^a Fzg ^, ^mr rad

/ 7 _ M Fzgjoll ^ Fzg.Lasl J aFzg, should m ^r rad

The respective vehicle _{target speed} v _FZ g _{/ SO} n results from integration of the vehicle _{target acceleration} a _Fzg determined according to the above context, _so ii by integration. If one chooses integration limits from the system start (t = 0) up to the current time t, the following relationship results:

(VI I)

^V Fzg, sotl ⁼ J ^a Fzg, soU

The connection between this

Vehicle _{target speed} v _Fzg , _so n and the ratio to be set r of the hydrostatic transmission 3 is given by the equation: (VIII)

_ ^V Fzg, should ^l rad nD, ιst ^r rad ^ ^π

taking into account the actual diesel speed n _D , i _St.

In the calculation of the vehicle target speed v _F2 g, _s oii also shows that due to the relationship according to equation VI integration over the

Vehicle _{target acceleration} a _Fz g, _so ii can ultimately reduce to an addition of the vehicle speed. The vehicle _{target speed} v _Fzg , _so n is given by:

dt + v "

Returning to the representation of the method in FIG. 3, it follows that in step S2 the simplified vehicle _{load moment} M _{Fzg # e} st is subtracted from the vehicle _{setpoint moment} M _Fzg , _so ii, instead of integrating the vehicle _{actual acceleration} a _Fzg , _3O n into a later addition of the

Vehicle _speed v _{Fzg /} i _St can be performed.

From the difference between the vehicle _{target torque} M _Fzg , _S oii and the simplified vehicle _{load torque} M _Fzg , _Θ st, a simplified vehicle target acceleration a ' _Fz g _{/ 3} oii is determined in step S9. After in the further step SlO about this simplified vehicle target acceleration a 'g _Fz, _so the integrated ii Fahrzeugistgeschwindigkeit v _Fzg, i _St is added subsequently. This Fahrzeugistgeschwindigkeit v _veh _is, can be determined in a simple manner, for example on the speed sensor 15th An integration with respect to this _component in the determination of the vehicle _{target speed} v _Fzg , _so ii can thus be avoided.

Using the actual diesel speed n _D , i _S t will then be out of the vehicle target speed

V _Fz _should g, determines the transmission ratio r. With the aid of this transmission ratio r, the delivery volume V _gP for the hydraulic pump 4 and a second characteristic curve are used to determine the displacement V _{gM of} the _{hydraulic motor} 5 by means of a first characteristic curve. These are given by way of example in method step S12. Initially, the displacement V _{gM of} the _{hydraulic motor} 5 is maintained at its constant, maximum value, while the pivoting angle of the hydraulic pump 4 along a ramp is increased linearly from a minimum value up to the maximum delivery volume. When the maximum delivery volume of the hydraulic pump 4 is reached, the displacement V _{gM of} the _{hydraulic motor} 5 is subsequently reduced along the second part of the dashed curve, thus further accelerating the vehicle.

FIG. 4 shows by way of example a characteristic diagram of a diesel internal combustion engine 2. In the diesel map is determined after determining a power requirement, which is composed of the traction drive 1 and the additional existing consumers, an optimal diesel speed, taking into account the specific fuel consumption. In addition to the diesel speed, the efficiencies of the hydrostats 4, 5 are taken into account. Instead of increasing the power of the diesel engine 2 along the points 16 to 23, which would allow an increase in the diesel power or the output torque at a constant speed, starting from a point A (Idling) increases the diesel speed to point B. This increase in diesel speed has the advantage that the hydraulic motor 5 can be operated in the range of improved efficiency. By increasing the speed of the diesel engine larger engine pivot angle of the hydraulic motor 5 can be realized, with the efficiency of the hydraulic motor 5 thereby improved. From the point B, the speed of the diesel engine 2 is increased in the direction of the point C so that as long as possible operation of the reciprocating engines 4, 5 of the hydrostatic transmission 3 in a good efficiency range is possible. The exact adjustment of the curve as well as the required support points are determined by means of an optimization function, which takes into account the driving comfort and / or the driving performance to be achieved in addition to the consumption. Instead of the optimization function, a map can be used, in addition to consumption and power also enters the speed.

In a vehicle with a drive of Figure 1, the recovery of braking energy can be realized in a simple manner. For this purpose, an unillustrated high pressure accumulator is connected to the suction side of the hydraulic pump 4. The drive torque to be provided by the diesel engine 2 accordingly reduces due to the high pressure provided. The vehicle target torque is calculated in this case according to:

(X)

where P _{SPHD is} the current pressure in the high pressure _accumulator and P _{SPND is} the pressure in the low pressure _{accumulator required to balance} the flow. In the described embodiment, the traction drive 1 with a pressure cradle consisting of a high-pressure accumulator and a low pressure accumulator connected. The above relationship applies without regard to the efficiencies. At the same time it must be ensured that the diesel engine 2 does not go into overrun mode. The engine swivel angle of the hydraulic motor 5 must therefore satisfy the following condition:

(XI)

The invention is not bound to the illustrated embodiment. Rather, individual features of the method according to the invention can be combined with each other.

Claims

claims

1. A method for controlling a traction drive (1) with a primary drive machine (2) and an associated continuously variable transmission (3), with the following method steps:

Detecting a position of a travel command setting device (S1), determining an operating point (A, B, C) for a primary drive machine (2) on the basis of a travel command (13, S4) and a current vehicle state,

- Determining a transmission ratio (r) of the hydrostatic transmission (3), characterized in that based on the detected position of the Fahrbefehlvorgabevorrichtung (13) a vehicle target torque of the traction drive (1) is determined, from which a required driving power is determined (S3), is determined on the basis of the required drive power of the operating point (A, B, C) of the primary drive machine (2).

2. The method according to claim 1, characterized in that from the target output torque (M _Fzg , soii) a vehicle _{target speed} (v _Fzg , _so n) based on a physical model of a drive train or the vehicle is determined (SlO) and the gear ratio (r ) of the continuously variable transmission (3) is determined from the vehicle target speed (Sil).

3. The method according to claim 1 or 2, characterized in that for determining the vehicle target torque (MFzg, soii) the determined position of the Travel command setting device (13) is assigned a value of zero to a resulting from the rated power of the prime mover torque (Sl).

4. The method according to claim 1 or 2, characterized in that: to determine the vehicle _{target torque} (M _{Fzg / SO} n) the determined position of the Fahrbefehlvorgabevorrichtung (13) a value from zero to one from the at an actual operating point (A , B, C) of the drive machine (2) is assigned to the resulting moment (Sl).

5. The method according to any one of claims 1 to 4, characterized in that for determining the transmission ratio (r) of the hydrostatic transmission (3) a vehicle _{load torque} (M _Fzg , _it t) is taken into account.

6. The method according to claim 5, characterized in that the vehicle _{load torque} (M _{Fzg / est} ) is determined from a suppression of the prime mover.

7. The method according to claim 5, characterized in that the vehicle _{load torque} (M _Fzg , _it t) from a control unit (g) of the drive _machine (2) is read.

8. The method according to claim 2, characterized in that the vehicle _{target speed} (V _Fzg , _so ii) from an initially determined vehicle _{target acceleration} (a _Fzg , _so ii) is determined by integration (SlO).

9. The method according to claim 8, characterized in that the transmission ratio (r) for the hydrostatic transmission (3) is determined from the vehicle _target speed (v _Fzg , _so n) and the actual speed (n _D , i _St ) of the primary drive _machine (2).

10. The method according to claim 8 or 9, characterized in that the integration of the vehicle _{target acceleration} (a _Fz g, _so ii) over the entire time since the system start (0-t) takes place.