DE102023201817A1 - Method for controlling a hydraulic drive system - Google Patents

Abstract

The invention relates to a method for controlling a hydraulic drive system which has a motor (4) which provides a drive variable and a plurality of adjustable hydraulic machines (2a, 2b) which are driven by the motor with the drive variable, comprising detecting or determining (110) a target specification for each of the hydraulic machines, detecting or determining (120) a drive variable actual value for each of the hydraulic machines (2a, 2b) of the drive variable which is received by the respective hydraulic machine, determining (130) a value of the drive variable which is to be made available to the respective hydraulic machine at most as a drive variable limit value for each of the hydraulic machines (2a, 2b) based on the target specifications, so that the sum of the drive variable limit values is equal to or less than a drive variable maximum, wherein the drive variable maximum is a value of the drive variable which is maximally available for the plurality of hydraulic machines, determining (140) a drive variable requirement value for each of the Hydraulic machines (2a, 2b) from the actual drive size value and the drive size limit value of the respective hydraulic machine, wherein, if the actual drive size value is smaller than the drive size limit value, the drive size requirement value is determined to be smaller than the drive size limit value, determining (150) a drive size control value for each of the hydraulic machines (2a, 2b) from the drive size maximum and the drive size requirement values of the respective other hydraulic machines, and controlling (160) the hydraulic machines (2a, 2b) with the drive size control values.

Description

The present invention relates to a method for controlling a hydraulic drive system.

Background of the invention

Work machines, in particular mobile work machines such as excavators, can have a hydraulic drive system to effect the movement of elements of the work machine by means of hydraulic cylinders or hydraulic motors (hydraulic consumers). Such a hydraulic drive system can include several hydraulic pumps driven by a single motor (e.g. internal combustion engine or electric motor), each of which supplies a portion of the hydraulic consumers with hydraulic fluid.

In the EP 4 012 117 A1 A hydromechanical controller is used to implement torque control for two hydraulic pumps according to the ratio of hydraulic outputs of the hydraulic machines.

Disclosure of the invention

According to the invention, a method for controlling a hydraulic drive system as well as a computing unit and a computer program with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the subclaims and the following description.

The invention uses the measure of determining drive size limit values for the (adjustable) hydraulic machines based on a drive size maximum and target specifications for the hydraulic machines. For each hydraulic machine, a drive size requirement value is determined from the respective drive size actual value and the respective drive size limit value in such a way that if the drive size actual value is smaller than the drive size limit value, the drive size requirement value is smaller than the drive size limit value. Furthermore, drive size control values for the hydraulic machines are determined from the drive size requirement values and the hydraulic machines are controlled accordingly. By taking the target specifications into account when determining the drive size limit values, it is possible to maintain the desired movements as far as possible in accordance with the target specification when the drive size maximum is exhausted. By taking the actual drive size values into account, it is possible to ensure that a freed-up amount of the drive size, e.g. if a hydraulic machine does not exhaust the drive size limit or the actual drive size value is below this, is used for other hydraulic machines.

The drive variable is, for example, a torque or a power. The values of the drive variable (drive variable limit values, drive variable actual values, drive variable maximum value, drive variable required values, drive variable maximum, drive variable control values, ...) can be specified in an appropriate unit (e.g. Nm or watts).

The target specification of a hydraulic machine is a specification for a quantity that is provided by the hydraulic machine and consumed by hydraulic consumers connected to the hydraulic machine. For example, the target specification can be a target volume flow, a target torque or a target pressure.

The maximum drive size indicates which value of the drive size is actually available for the hydraulic machines to drive them. In the limiting case, the maximum drive size can be, for example, a maximum drive size value that can be provided by the motor. The maximum drive size value can be speed-dependent.

The drive size limit value of a hydraulic machine indicates the maximum value of the drive size that is assigned to this hydraulic machine. The drive size actual value of a hydraulic machine indicates the value of the drive size that is actually recorded by this hydraulic machine at the respective time (e.g. determinable from the output pressure, the displacement or swivel angle, the speed; which are recorded using sensors, for example).

The drive size requirement value of a hydraulic machine indicates which value of the drive size is required by this hydraulic machine at the respective time; i.e. corresponds to an actual requirement taking into account the drive size limit value. The drive size requirement value is determined such that it is less than or equal to the drive size limit value and, if the drive size actual value is less than the drive size limit value, the drive size requirement value is determined such that it is less than the drive size limit value. If the drive size actual value is not less than the drive size limit value, the drive size requirement value can in particular be determined as equal to the drive size limit value. The drive size requirement value of a hydraulic machine can, for example, be the minimum of the drive size actual value and the drive size limit value. limit value of the respective hydraulic machine (although other functional dependencies are also conceivable, as long as the above conditions are met).

The drive variable control value of a hydraulic machine indicates which value of the drive variable is to be achieved by adjusting or controlling the hydraulic machine, e.g. by adjusting the swivel angle or the displacement.

A computing unit according to the invention, e.g. a control unit of a mobile work machine, is set up, in particular in terms of programming, to carry out a method according to the invention.

The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, since this causes particularly low costs, especially if an executing control unit is also used for other tasks and is therefore already present. Suitable data carriers for providing the computer program are in particular magnetic, optical and electrical storage devices, such as hard disks, flash memories, EEPROMs, DVDs, etc. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention emerge from the description and the accompanying drawings.

It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

The invention is illustrated schematically in the drawing using embodiments and is described in detail below with reference to the drawing.

Character description

• 1 shows the structure of an exemplary hydraulic drive system in which a control method according to the invention can be applied.
• 2 shows a flow chart according to an embodiment of the invention.

Detailed description of the drawing

1 shows, in a highly simplified form, the structure of an exemplary hydraulic drive system in which a control method according to the invention can be used. The hydraulic drive system is provided in a work machine, in particular a mobile work machine, e.g. an excavator.

The drive system comprises two hydraulic pumps or hydraulic machines, namely a first adjustable hydraulic machine 2a and a second adjustable hydraulic machine 2b, which are jointly driven by a motor 4. For example, the motor 4 is coupled to the first and second hydraulic machines via shafts in order to drive them. Optionally, one or more gears can be provided between the motor and/or the hydraulic machines, in particular transmission gears, so that the speeds can differ according to the respective transmission ratios. The hydraulic machines 2a, 2b are each set up, for example, to convey pressure medium (i.e. hydraulic fluid, in particular a hydraulic oil) from a tank into respective hydraulic lines (first hydraulic line 6a, second hydraulic line 6b), which are connected to output-side outputs or pressure outputs of the hydraulic machines. Both hydraulic machines 2a, 2b are adjustable, i.e. their displacement (i.e. volume of pressure medium delivered per revolution, also referred to as displacement volume) is changeable or adjustable, e.g. according to a swivel angle. The hydraulic machines 2a, 2b can be axial piston machines, in particular swash plate machines. The motor 4 can be an internal combustion engine, in particular a diesel engine, or an electric motor or an electric machine.

The motor 4 provides a so-called drive variable, e.g. a torque or a power. The drive variable provided is converted by the hydraulic machines (in a split form) into hydraulic power or hydraulic variables, e.g. pressure and/or volume flow. The drive variable that can be provided by the motor 4 is limited upwards by a drive variable maximum that is typically dependent on the speed.

Furthermore, pressure sensors can be provided, with a first pressure sensor 8a measuring the pressure (output pressure) of the pressure medium at the pressure outlet of the first hydraulic machine 2a (or at the first hydraulic line 6a), and a second pressure sensor 8b measuring the pressure (output pressure) of the pressure medium at the pressure outlet of the second hydraulic machine 2b (or at the second hydraulic line 6b). Displacement sensors can also be provided (or swivel angle sensors) may be provided, wherein a first displacement sensor 10a measures or determines the displacement (or swivel angle) of the first hydraulic machine 2a, and a second displacement sensor 10b measures or determines the displacement (or swivel angle) of the second hydraulic machine 2b.

The pressure output of the first hydraulic machine 2a is connected (via the first hydraulic line 6a) to a first valve arrangement 12a, which controls the inflow and outflow of pressure medium to one or more (first) hydraulic consumers 14a. Here, for example, a hydraulic cylinder is shown as the first hydraulic consumer 14a. The pressure output of the second hydraulic machine 2b is connected (via the second hydraulic line 6b) to a second valve arrangement 12b, which controls the inflow and outflow of pressure medium to one or more (second) hydraulic consumers 14b. Here, for example, a hydraulic motor is shown as the second hydraulic consumer 14b. In the case of an excavator in which the hydraulic drive system is provided, the hydraulic cylinder could, for example, cause the swivel movement of the excavator arm and the hydraulic motor could cause the rotational movement of the upper carriage relative to the chassis. Each of the valve arrangements 12a, 12b can be connected to other or additional hydraulic consumers as an alternative or in addition to the hydraulic consumers shown in order to control the inflow and outflow of pressure medium to/from them. In general, each valve arrangement 12a, 12b is therefore connected to at least one first or second hydraulic consumer 14a, 14b (e.g. at least one hydraulic cylinder and/or hydraulic motor) in order to control the inflow and outflow of pressure medium to or from it. The valve arrangements each include, for example, one or more valves, in particular directional valves, which are at least partially controllable in order to control the inflow and outflow of pressure medium. The desired movements of the hydraulic consumers and the existing loads on the hydraulic consumers result in requirements for the output pressure and/or the volume flow of the corresponding hydraulic machine.

An electronic controller 16 (processing unit) can be provided which is set up to control the hydraulic machines 2a, 2b, i.e. to control or regulate their displacement or swivel angle. The controller 16 can record sensor data from the first and second pressure sensors 8a, 8b and/or from the first and second displacement sensors 10a, 10b. The controller 16 can also be set up to control the motor 4 (e.g. to control it with a target speed) and/or to record a speed of the motor 4. The controller 16 can also be set up to control the valve arrangements and thus the hydraulic consumers, e.g. based on operating signals which are recorded by an operating device 18 (e.g. a joystick) and transmitted to the controller. The respective control lines and/or signal lines (for transmitting control signals or measurement data) are shown in the figure as dashed lines as an example. The electronic control 16 is particularly designed to carry out a method according to the invention for controlling a hydraulic drive system.

The hydraulic machines 2a, 2b are controlled taking into account target specifications for the hydraulic machines, i.e. a target specification is determined or recorded for each hydraulic machine. This determination or recording can be carried out by the controller 16, for example based on operating signals. Target specifications can be, for example, target volume flows, target torques, target pressures or similar. Furthermore, the hydraulic machines 2a, 2b can be controlled in such a way that the proportion of the drive variable taken up or consumed by each of the hydraulic machines corresponds as closely as possible to a specific value, which is referred to as the drive variable control value. The hydraulic machines are therefore adjusted or controlled (for example as part of a control system) in such a way that the respective drive variable control values are achieved. The actual recorded value or consumed portion of the drive variable, which is referred to as the actual drive variable value and which can be determined using the measurement data of the corresponding pressure sensor and/or displacement sensor, can deviate from the drive variable control value, e.g. in dynamic situations or if this cannot be achieved, for example due to a limitation of the maximum possible displacement and/or the maximum output pressure (e.g. pressure cut-off of a hydraulic machine).

In 1 Two hydraulic machines 2a, 2b are shown as examples, which are jointly driven by the motor 4. In general, more than two hydraulic machines can be provided, which are jointly driven by a motor, with each hydraulic machine supplying corresponding hydraulic consumers with pressure medium (in particular via valve arrangements).

2 shows a flow chart according to an embodiment of the invention, ie a method for controlling a hydraulic drive system comprising a motor providing a drive variable and a plurality of hydraulic machines driven by the motor with the drive variable (as eg in 1 The drive size, which depends on the speed of the engine can be, for example, a torque or a power, whereby the torque is used as an example in the following formulas.

The method or the steps of the method can be carried out in particular by an electronic control of the hydraulic drive system.

In step 110, a target specification for each of the hydraulic machines is recorded or determined. The target specification can be, for example, a target volume flow, a target torque or a target pressure. The following formulas use the target volume flow as an example, which can be determined from volume flow requirements resulting from operator inputs.

In step 120, an actual drive variable value is determined or recorded for each of the hydraulic machines, which is actually recorded by the respective hydraulic machine, i.e. the proportion or a value corresponding to the proportion of the drive variable that is actually recorded by the respective hydraulic machine at the respective time of determination or recording. For this purpose, output pressures or displacements measured by pressure sensors and displacement sensors can be used in particular.

In step 130, a so-called drive size limit value is determined for each hydraulic machine, taking into account the target specifications for the hydraulic machines and making the determination such that the sum of all drive size limit values is equal to or less than a drive size maximum. The drive size limit value of a hydraulic machine designates the maximum value of the drive size that can be assigned to it. The drive size maximum can be viewed as the value of the drive size that can be used by the hydraulic machines as a whole. In particular, the drive size limit values can be determined such that the ratios of two drive size limit values (for different hydraulic machines) are equal to the ratios of the corresponding two target specifications. For all pairs of two hydraulic machines, the ratio of the drive size limit values that correspond to the hydraulic machines in a pair should be equal to the ratio of the target specifications that correspond to the hydraulic machines in the pair.

The maximum drive variable can be a maximum drive variable value of the engine, i.e. a maximum value of the drive variable that can be provided by the engine, which is dependent on the speed of the engine, for example. The maximum drive variable value of the engine can be recorded or determined. For example, the current maximum drive variable value can be transmitted from an engine control to an electronic control that implements a method according to the invention. Corresponding variables (e.g. speed of the engine) can also be recorded by an electronic control that implements a method according to the invention, e.g. transmitted by an engine control, and the electronic control can determine the current maximum drive variable value from them (e.g. using a characteristic map).

If it is determined, e.g. during or after at least one execution of the method, that the maximum drive size value of the motor changes, it can be provided that the maximum drive size is changed accordingly (i.e. a changed maximum drive size is determined) and that the method is repeated with the changed maximum drive size.

$$M_{lim\mathrm{,2}}=M_{max}\cdot \frac{Q_{dem2}}{Q_{dem\mathrm{,1}}+Q_{dem\mathrm{,2}}}$$

In the case of two hydraulic machines, the drive size limits that satisfy these conditions (including the ratio condition) can be calculated, for example, by: $$M_{lim\mathrm{,1}}=M_{max}\cdot \frac{Q_{dem\mathrm{,1}}}{Q_{dem\mathrm{,1}}+Q_{dem\mathrm{,2}}}$$

$$M_{lim\mathrm{,2}}=M_{max}\cdot \frac{Q_{dem2}}{Q_{dem\mathrm{,1}}+Q_{dem\mathrm{,2}}}$$

Here, M _max denotes the drive size maximum (here e.g. torque maximum) of the motor, Q _dem,1 denotes the target value (here e.g. target volume flow) of the first hydraulic machine, Q _dem,2 denotes the target value (here e.g. target volume flow) of the second hydraulic machine, M _lim,1 denotes the drive size limit value (here e.g. torque limit value) of the first hydraulic machine and M _lim,2 denotes the drive size limit value (here e.g. torque limit value) of the second hydraulic machine.

Accordingly, in general, for each of the hydraulic machines, the drive size limit value such that the above conditions (including the condition on the ratios) are met can be calculated as the product of the drive size maximum with the quotient of the target specification of the respective hydraulic machine and the sum of the target specifications for all hydraulic machines.

When determining the actual drive values (step 120) and/or when determining the Drive variable limit values (step 130) can take into account the efficiencies of the hydraulic machines, which depend in particular on the speed and/or the displacement and/or the output pressure of the respective hydraulic machine. The efficiency of a hydraulic machine refers in particular to the extent to which the drive variable received on the input side (e.g. torque or power) is converted by the hydraulic machine into output-side variables (e.g. output pressure times displacement or output pressure times volume flow). The efficiency depends on the operating point of the respective hydraulic machine, which is characterized, for example, by the speed and/or the displacement and/or the output pressure of the respective hydraulic machine. The operating point, in particular the speed and/or the displacement and/or the output pressure, can be determined (at least partially) from measured or recorded values for speed and/or displacement and/or output pressure and/or from the target specification. The efficiencies can be stored, for example, in the form of characteristic maps in the electronic control system. When determining the drive size limit value, the quotient of the target value and the efficiency can be used for each hydraulic machine instead of the target value (if the efficiencies are defined accordingly).

In step 140, a drive size requirement value is determined for each of the hydraulic machines from the drive size actual value and the drive size limit value of the respective hydraulic machine. The drive size requirement value of each of the hydraulic machines is determined in particular as being equal to the minimum Min(M _ist,i ; M _ıim,i ) from the drive size actual value and the drive size limit value of the respective hydraulic machine, ie as the smaller of the drive size actual value and the drive size limit value.

In general, the drive size requirement value is determined to be less than or equal to the drive size limit value and, if the drive size actual value is less than the drive size limit value, the drive size requirement value is determined to be less than the drive size limit value. This means that in addition to the minimum calculation, other functions are also conceivable for determining the drive size requirement value. For example, if the drive size actual value is less than the drive size limit value, an average of these values could be used. In any case, the drive size requirement value is less than or equal to the drive size limit value.

In step 150, a drive size control value is determined for each of the hydraulic machines. For each hydraulic machine, the drive size control value assigned to it is determined to be equal to or less than the drive size maximum minus the drive size requirement values of all other hydraulic machines (or equal to the drive size maximum minus the sum of the drive size requirement values of all other hydraulic machines or less than this value).

$$M_{set\mathrm{,2}}=M_{max}-Min\left(M_{ist\mathrm{,1}};M_{lim\mathrm{,1}}\right)$$

Overall (step 140 and step 150), in the case of only two hydraulic machines, the following applies in particular: $$M_{set\mathrm{,1}}=M_{max}-Min\left(M_{ist\mathrm{,2}};M_{lim\mathrm{,2}}\right)$$

$$M_{set\mathrm{,2}}=M_{max}-Min\left(M_{ist\mathrm{,1}};M_{lim\mathrm{,1}}\right)$$

Here, M _set,1 denotes the drive variable set point of the first hydraulic machine, M _set,2 denotes the drive variable set point of the second hydraulic machine, M _ist,1 denotes the actual drive variable value of the first hydraulic machine and M _ist,2 denotes the actual drive variable value of the second hydraulic machine. If the actual drive variable value or drive variable requirement value of one of the two hydraulic machines is below its drive variable limit value, i.e. if a portion (freed portion) of the drive variable that is assigned to this hydraulic machine according to the drive variable limit value is not used by the hydraulic machine, the freed portion (drive variable limit value minus actual drive variable value of this hydraulic machine) is assigned to the other hydraulic machine, i.e. the drive variable set point of the other hydraulic machine is correspondingly larger. The case that the actual drive size value is below the drive size limit value can occur, for example, if there is another limitation of the recorded drive size of the hydraulic machine, for example due to pressure cut-off (internal pressure limitation of the hydraulic machine) or in dynamic situations. The hydraulic machine in question can therefore also be referred to as a limited hydraulic machine.

• Der Antriebsgrößen-Stellwert für diese (limitierte) Hydraulikmaschine wird als gleich dem Antriebsgrößen-Istwert dieser Hydraulikmaschine bestimmt. Weiter wird ein angepasstes Antriebsgrößen-Maximum als gleich dem (aktuellen) Antriebsgrößen-Maximum minus der Differenz zwischen Antriebsgrößen-Grenzwert und Antriebsgrößen-Istwert dieser (limitierten) Hydraulikmaschine bestimmt. Anschließend werden die Schritte 130 bis 150 eingeschränkt auf die anderen Hydraulikmaschinen (d.h. die von der limitierten Hydraulikmaschine verschiedenen Hydraulikmaschinen) unter Verwendung des angepassten Antriebsgrößen-Maximums erneut durchgeführt.

In the case of more than two hydraulic machines, a suitable distribution of the released portion (of a limited hydraulic machine) to the other hydraulic machines can be selected. For example, in the case of more than two hydraulic machines, if it is determined (e.g. in step 140 or step 150) that for one (limited) hydraulic machine, the actual drive size value or drive size requirement value corresponding to this hydraulic machine is below the drive size limit value corresponding to this hydraulic machine, the following procedure can be followed:

• The drive size control value for this (limited) hydraulic machine is determined to be equal to the drive size actual value of this hydraulic machine. Furthermore, an adjusted drive size maximum is determined to be equal to the (current) drive size maximum minus the difference between the drive size limit value and the drive size actual value of this (limited) hydraulic machine. Then, steps 130 to 150 are carried out again, restricted to the other hydraulic machines (ie the hydraulic machines other than the limited hydraulic machine), using the adjusted drive size maximum.

In step 160, the hydraulic machines are controlled according to the drive variable control values.

The steps of the method can be carried out repeatedly or continuously so that the drive variable control values are continuously updated or adjusted according to changed target values and/or changed drive variable actual values and/or a changed drive variable maximum.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 4012117 A1 [0003]

Claims (14)

Method for controlling a hydraulic drive system having a motor (4) that provides a drive variable and a plurality of adjustable hydraulic machines (2a, 2b) that are driven by the motor with the drive variable, comprising: Detecting or determining (110) a target specification for each of the hydraulic machines; Detecting or determining (120) for each of the hydraulic machines (2a, 2b) a value of the drive variable that is received by the respective hydraulic machine as the actual drive variable value; Determining (130) for each of the hydraulic machines (2a, 2b) based on the target specifications a value of the drive variable that is to be made available to the respective hydraulic machine at most as a drive variable limit value, so that the sum of the drive variable limit values is equal to or less than a drive variable maximum, wherein the drive variable maximum is a value of the drive variable that is maximally available for the plurality of hydraulic machines; Determining (140) a drive size requirement value for each of the hydraulic machines (2a, 2b) from the drive size actual value and the drive size limit value of the respective hydraulic machine, wherein, if the drive size actual value is less than the drive size limit value, the drive size requirement value is determined to be less than the drive size limit value; Determining (150) a drive size control value for each of the hydraulic machines (2a, 2b) from the drive size maximum and the drive size requirement values of the respective other hydraulic machines; and Controlling (160) the hydraulic machines (2a, 2b) with the drive size control values. Procedure according to Claim 1 , wherein for each hydraulic machine, if the actual drive size value is not less than the drive size limit value, the drive size requirement value is determined to be equal to the drive size limit value; and/or wherein the drive size requirement value of each hydraulic machine (2a, 2b) is determined to be the minimum of the actual drive size value and the drive size limit value of the respective hydraulic machine. Method according to one of the preceding claims, wherein the drive variable limit values are determined such that the ratios between any two drive variable limit values are equal to the ratios between the corresponding target values. Method according to one of the preceding claims, wherein the drive size control value for each of the hydraulic machines (2a, 2b) is determined to be equal to or less than the drive size maximum minus the sum of the drive size requirement values of the respective other hydraulic machines. Procedure according to Claim 4 , wherein in the case of two hydraulic machines (2a, 2b) the drive size control value for each of the two hydraulic machines is determined as equal to the drive size maximum minus the drive size requirement value of the respective other hydraulic machine. Method according to one of the preceding claims, wherein the drive variable is a drive torque. Method according to one of the preceding claims, wherein the target specification is a target volume flow or a target torque. Method according to one of the preceding claims, wherein the drive variable maximum corresponds to a drive variable maximum value of the motor (4), wherein the drive variable maximum value indicates a maximum value of the drive variable that can be provided by the motor. Procedure according to Claim 8 , wherein the maximum drive size value of the motor (4) is detected or determined and, if it is determined that the maximum drive size value of the motor has changed or is changing, the maximum drive size is changed accordingly and the method is carried out again using the changed maximum drive size. Method according to one of the preceding claims, wherein when determining the actual drive variable values and/or when determining the drive variable limit values, efficiencies of the hydraulic machines (2a, 2b) are taken into account, which are dependent on the operating point, in particular on the speed and/or the displacement and/or the output pressure, of the respective hydraulic machine. Method according to one of the preceding claims, wherein in the case of more than two hydraulic machines, if, in particular when determining the drive size requirement value, it is determined for a limited hydraulic machine of the plurality of hydraulic machines that its drive size actual value is below its drive size limit value, the drive size control value for the limited hydraulic machine is determined to be equal to the drive size actual value of this hydraulic machine; an adjusted drive size maximum as the drive size maximum minus the difference between drive size limit value and drive size actual value of the limited hydraulic machine are determined; and the method, in particular the determination of drive size limit values and the determination of drive size requirement values, is carried out again restricted to those of the plurality of hydraulic machines other than the limited hydraulic machine using the adjusted drive size maximum. Computing unit (160) comprising a processor configured to carry out the method according to any one of the preceding claims. Computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method according to Claim 1 until 11 to execute. Computer-readable data carrier on which the computer program is Claim 13 is stored.

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