Method for scaling volumetric flow rate demand in control of hydraulic drive system

Abstract

To provide a method for scaling volumetric flow rate demand in control of a hydraulic drive system, the hydraulic drive system comprising a pressure medium source (5) for providing a volumetric flow rate in a pressure medium in a hydraulic drive unit and a plurality of hydraulic loads (8), where a pressure medium is supplied to the hydraulic loads (8) with individual controllable systems through a valve assembly (6).SOLUTION: In the present method, an output side volumetric flow rate demand (85) is determined from a given input side volumetric flow rate demand for each load using a pump flow rate scaling function (84) for each load, where by the pump flow rate scaling function, an available volumetric flow rate variable of a pressure medium source (5) is determined (120), for each load, a volumetric flow rate variable proportion in the available volumetric flow rate variable is determined (130), and for each load, the output side volumetric flow rate demand (85) is determined taking into account the volumetric flow rate variable proportion of the load (140).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for scaling a volume flow demand in the control of a hydraulic drive system and to a method for controlling a hydraulic drive system, as well as a computing unit and a computer program for the execution thereof. [Background technology]

[0002] 2. Background of the Invention The working machine may have a hydraulic drive with several functional elements that are individually driven by hydraulic loads (e.g. hydraulic cylinders or hydraulic motors). In the case of conventional hydraulic drives with mechanically and hydraulically controlled participants or hydraulic loads, individual and therefore distributed control devices are used that allow the power consumption of the respective participants or loads to be individually controlled. These control devices or control elements are, for example, valves assigned to the participants or loads, which are directly driven and operated on the basis of presettings of the operator of the working machine, captured, for example, by a joystick. Summary of the Invention [Problem to be solved by the invention]

[0003] Disclosure of the Invention According to the invention, a method for scaling a volume flow demand in the control of a hydraulic drive system and a method for controlling a hydraulic drive system, as well as a computing unit and a computer program for the execution thereof, are proposed having the features of the independent claims. Preferred embodiments are the subject of the dependent claims and the following description. [Means for solving the problem]

[0004] According to the invention, the volumetric flow demand in the control of a hydraulic drive system comprising a pressure medium source and a number of hydraulic loads to which pressure medium is supplied via a valve assembly is scaled using a pump flow scaling function that maps the input volumetric flow demand of the load to the output volumetric flow demand of the load. The pump flow scaling function determines the available volumetric flow variable of the pressure medium source, determines for each load a volumetric flow variable proportion of the available volumetric flow variable, and determines for each load an output volumetric flow demand taking into account (or based on) the volumetric flow variable proportion. By this procedure, it is possible to achieve a drive control of the loads using the valve assembly such that the volumetric flow rate of pressure medium actually available from the pressure medium source is maintained in total. For example, it is possible to avoid pressure drops that would occur if more pressure medium were supplied to the multiple loads in total than the actually available volumetric flow rate of the pressure medium source.

[0005] The available volume flow variable of the pressure medium source is in particular the available volume flow rate of the pressure medium and / or the available volume flow rate change between successive points in time or, in other words, the available volume flow rate change rate. The volume flow variables are assumed as positive values ​​or as multiple positive values ​​if they comprise multiple (partial) variables. In particular, the volume flow rate change or the volume flow rate change rate is from the point of view shown as a positive value, i.e. the volume flow rate increase. According to an embodiment, the volume flow rate variable percentages for the load are determined such that their sum is less than or equal to the available volume flow rate variable.

[0006] According to one embodiment, the volumetric flow variable percentages are determined such that their ratio to one another is equal to the corresponding ratio of said input volumetric flow demands, which ultimately satisfies the desired ratio based on operator input between the movements of the machine parts operated by the hydraulic loads.

[0007] According to one embodiment, the available volume flow variable is or includes the available volume flow of the pressure medium source, where for each load the output volume flow demand is equal to its volume flow variable proportion, i.e. according to this embodiment the volume flow is divided directly, which can be realized relatively easily and can be done, for example, according to a proportion of the input volume flow demand.

[0008] According to one embodiment, the available volume flow variable is or includes the available volume flow change of the volume flow of the pressure medium source between a first time point and a second time point that exists after the first time point, where an output volume flow demand at the first time point is given for each load and an output volume flow demand at the second time point for each load is determined from its output volume flow demand at the first time point and its volume flow variable ratio, in particular the output volume flow demand at the second time point is used as the output volume flow demand of the pump flow rate scaling function. That is, according to this embodiment, the volume flow is not divided directly, but the additionally available volume flow (volume flow change) is divided. The use of the volume flow change makes it possible to avoid discontinuities in the pressure medium supply of the individual loads, which may occur when further loads are switched on. The available volume flow change can be determined or calculated, for example, from a known or measured volume flow rate change rate of the volume flow of the pressure medium source (for example as the volume flow rate change rate times the time difference between the second time point and the first time point). The first and second time points are, for example, capture and / or evaluation time points of the electronic control, which take place, for example, on a time pattern with regularly spaced time points. The second time point is, for example, the (current) time point at which the output volumetric flow demand is determined by the pump flow scaling function. The first time point is therefore an earlier time point at which the output volumetric flow demand of the pump flow scaling function is already given or known, for example temporarily stored.

[0009] According to one embodiment, the volume flow variable percentage for loads whose output volume flow demand at a first time point is equal to or greater than the input volume flow demand at a second time point is set to zero. In other words, loads whose volume flow demand is already met are not assigned a percentage in the volume flow variable, i.e., a percentage in the volume flow change. In other words, the total volume flow change can be divided among the loads whose volume flow demand is not yet met.

[0010] According to one embodiment, for each load, or for each load whose volumetric flow variable percentage is not set to zero, - the sum of the output volume flow demand and the volume flow rate variable proportion at a first time point is determined, The output volumetric flow demand at the second time point is determined as being equal to the minimum value from the input volumetric flow demand at the second time point and the sum determined for the load. That is, for loads that have not yet reached the input volumetric flow demand, the volumetric flow variable percentage is added to the output volumetric flow demand, i.e., the output volumetric flow demand is changed according to the assigned volumetric flow change percentage (or volumetric flow change rate).

[0011] According to an embodiment, the predefined priority of the loads is taken into account when determining the volumetric flow variable percentage. For example, the priority may be given in the form of a numerical value for each of the loads, and the volumetric flow variable percentage of the load can be determined according to the ratio of the corresponding priority (numerical value), whereby the correspondingly determined output volumetric flow demand of the load is limited by the input volumetric flow demand of this load. This division of the available volumetric flow variables according to the ratio of the corresponding priority should in particular only relate to loads that are assigned a volumetric flow variable percentage different from zero or whose volumetric flow variable percentage is not set to zero. Similarly, if the volumetric flow variable is or includes an available volume flow, this division should only be performed for those loads whose input volumetric flow demand has not yet been satisfied. A temporal prioritization is also conceivable. For example, a higher priority can be assigned to a load whose last change in input volumetric flow demand was further back in time.

[0012] According to one embodiment, the output volumetric flow demand of the pump flow scaling function is taken into account in the control of the pressure medium source (or the pressure medium source is driven based on the output volumetric flow demand of the pump flow scaling function). The output volumetric flow demand of the pump flow scaling function can be taken into account directly or indirectly, as will be briefly explained below. The driving control can be based directly on the output volumetric flow demand of the pump flow scaling function, for example the pressure medium source can be driven such that its volume flow is equal to (or greater than) the sum of the output volumetric flow demands of the pump flow scaling function. Alternatively, the driving control can be based indirectly on the output volumetric flow demand of the pump flow scaling function, for example when the output volumetric flow demand of the pump flow scaling function is used as the input volumetric flow demand of a subsequent scaling function.

[0013] According to one embodiment, the pump flow scaling function further determines for each load a scaling factor as the ratio of the output volumetric flow demand of the respective load to the input volumetric flow demand of the respective load, where the scaling factor of the pump flow scaling function is taken into account in particular in the actuation control of the valve assembly. Here too (as in the case of the output volumetric flow demand), an actuation control of the valve assembly based directly or indirectly on the scaling factor of the pump flow scaling function is possible.

[0014] According to a further aspect of the invention, a method for controlling a hydraulic drive system is proposed, the hydraulic drive system comprising a pressure medium source providing a volumetric flow rate of pressure medium in the hydraulic drive system and a plurality of hydraulic loads, the hydraulic loads being supplied with pressure medium in an individually controllable manner via a valve assembly. The method for controlling a hydraulic drive system comprises the following steps: receiving or determining a volumetric flow rate demand for each of the plurality of loads; using one or more successive stages of scaling functions, where for each stage the scaling function for each load maps an input volumetric flow rate demand of the respective load to an output volumetric flow rate demand of the respective load, determining a scaling factor for each load as a ratio between the output volumetric flow rate demand and the input volumetric flow rate demand of the respective load, the output volumetric flow rate demand of one stage being used as the input volumetric flow rate demand of the respective next stage scaling function, the volumetric flow rate demand being: the step of using as an input volumetric flow demand of a first stage scaling function; determining a total scaling factor for each load based on the scaling factor of each load; determining a scaled volumetric flow demand for each load based on the total scaling factor of each load; determining a total volumetric flow demand from the output volumetric flow demand of a last stage scaling function; controlling a valve assembly in response to the scaled volumetric flow demand; and controlling a pressure medium source in response to the total volumetric flow demand, wherein the scaling function comprises a pump flow scaling function according to the present invention.

[0015] The use of a scaling function makes it possible to take into account the resulting or desired relationships or conditions between the various hydraulic loads and / or pressure medium sources or their volumetric flows, coded into the scaling function, as well as further existing conditions, such as the available power or available torque of the drive motors of the pressure medium sources, which makes it possible to avoid undesirable behavior during the concerted movement of several parts operated by the loads of the machine in which the hydraulic drive system is used, such as jerky movements of the individual parts, such that the required volumetric flow of the pressure medium fluctuates significantly in a short time when the hydraulic loads are switched on or off, i.e. a constant control behavior that is predictable for the machine operator can be achieved when using several hydraulic loads simultaneously.

[0016] A computing unit according to the invention, for example a control device for a hydraulic drive system of a mobile work machine, is in particular program-technically designed to carry out the method according to the invention.

[0017] It is also advantageous to implement the method according to the invention in the form of a computer program or computer program product with a program code for implementing all the method steps, since this entails very little cost, especially if the control device to be executed is already existing in any case, since it is also used for other tasks. Suitable data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, etc. Downloading the program via a computer network (Internet, intranet, etc.) is also possible.

[0018] Further advantages and embodiments of the invention become apparent from the description and the accompanying drawings.

[0019] It is to be understood that the features mentioned above, and those to be further described below, can be used not only in the respective combinations presented, but also in other combinations or alone, without departing from the scope of the invention.

[0020] The invention is illustrated diagrammatically in the drawing by way of an embodiment and will be explained in detail below with reference to the drawing. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a simplified diagram showing the structure of a hydraulic drive system. [Diagram 2] FIG. 1 illustrates a flow diagram according to an exemplary embodiment of a method for scaling volumetric flow demand in controlling a hydraulic drive system. [Diagram 3] FIG. 4 illustrates a control method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Detailed Description of the Drawings FIG. 1 shows, in a simplified manner, the structure of a hydraulic drive system in which the method according to the invention can be used.

[0023] A hydraulic machine 2, in particular a hydraulic pump (also called pump), is provided, by which a pressure medium (hydraulic medium, typically hydraulic oil) is pumped from a tank (hydraulically connected to the suction port of the hydraulic pump) to the hydraulic drive system. The illustrated hydraulic machine 2 is, for example, adjustable, i.e. has an adjustable displacement. The term displacement means the volume of pressure medium delivered per each revolution of the hydraulic machine 2. For example, the hydraulic machine 2 is an axial piston machine, for example of swash plate or tilted shaft design type, where the displacement corresponds to an adjustable swivel angle. The hydraulic machine 2 is driven by a motor or drive motor 4, for example an internal combustion engine, in particular a diesel engine, or an electric motor. The hydraulic machine 2 together with the drive motor 4 forms a pressure medium source 5 of the hydraulic drive system. In general, the pressure medium source may include one or more hydraulic machines and / or one or more drive motors.

[0024] The volume flow rate of pressure medium delivered by the hydraulic machine 2 can be varied by adjusting the displacement. In particular, if the drive motor 4 is an electric motor or electric machine, the displacement can additionally or alternatively be varied by varying the rotational speed of the electric motor. Correspondingly, in particular, if an electric motor is used as the drive motor 4, hydraulic machines with a constant displacement (constant speed machines or constant speed pumps) can also be used. In the case of an internal combustion engine, rotational speed changes occur relatively slowly, so that in hydraulic drives this is often operated at a constant rotational speed.

[0025] The pressure medium delivered by the hydraulic machine 2 is guided via a hydraulic line (hydraulically connected with the working port of the hydraulic pump) to a valve assembly 6, formed for example of a valve module or a valve disk, by means of which the inflow and outflow of the pressure medium to a number of hydraulic loads 8 can be controlled, here exemplarily one hydraulic motor and two hydraulic cylinders, which are coupled for example to mechanical parts of the machine in which the hydraulic drive system is used, in order to drive them or to cause their movements. For example, in the case of an excavator, the hydraulic motor can drive the rotational movement of the upper structure relative to the lower structure, and the hydraulic cylinder can cause the swivel movement of an arm or boom element. In general, there may be one or more hydraulic loads, i.e. in particular one or more hydraulic motors and / or hydraulic cylinders. The valve assembly 6 is in particular configured such that the inflow and outflow of the pressure medium to each of the hydraulic loads 8, i.e. to each hydraulic load 8, can be controlled individually or separately, for example by controlling the inflow and outflow throttles in the valve assembly or the cross-section of the valve openings. The hydraulic load is also referred to as the load for short.

[0026] In the hydraulic drive system, an electronic control 10 (computing unit) or control device is provided, which is arranged to determine and / or generate control signals for controlling the pressure medium source 5 and / or for controlling the valve assembly 6. The control of the pressure medium source 5 may involve the control or regulation of the hydraulic machine 2 and / or (for example in the case of an electric motor) the control of the rotational speed of the drive motor 4. These control signals are for example coded in the form of electric signals and transmitted via control lines (represented by dashed lines) to the respective components or their control units.

[0027] The control signals are determined by the electronic control 10 by implementation of a control algorithm (e.g. in the form of a computer program or computer program module) based on the operating presets of the operator, which are captured by a suitable operating device (e.g. a joystick). The electronic control 10 can, for example, capture the operating presets 12 itself or receive them from the operating device and determine or calculate the corresponding volumetric flow requirements for the individual (hydraulic) loads therefrom. Alternatively, it may be envisaged that a higher-level control captures or receives the operating presets from the operating device, determines or calculates the corresponding volumetric flow requirements for the individual loads therefrom and transmits said volumetric flow requirements 14 to the electronic control.

[0028] The electronic control unit 10 is in particular configured to implement the method according to the invention, for example by executing a computer program stored in the electronic control unit or by executing a computer program module stored in the electronic control unit.

[0029] The hydraulic drive system may be provided with one or more sensors (not shown), which transmit their measurement results, for example via sensor lines, to the electronic control 10. The electronic control 10 may be correspondingly configured to receive or capture the measurement results from the sensors and use them when controlling the hydraulic drive. For example, one or more of a displacement sensor or a swivel angle sensor for capturing the displacement of the hydraulic pump 2, a rotation speed sensor for capturing the rotation speed of the drive motor 4, one or more pressure sensors for capturing the pressure of the pressure medium at appropriate points of the hydraulic drive, a position sensor (for example an end position sensor) for capturing the position of a piston in a hydraulic cylinder, etc. may be provided.

[0030] Figure 2 shows a flow diagram according to an exemplary embodiment of a method for scaling a volumetric flow demand in a hydraulic drive system, such as the controller of the drive system shown in Figure 1, comprising a pressure medium source supplying a volumetric flow rate of pressure medium to the hydraulic drive accordingly, and a number of hydraulic loads to which pressure medium is supplied in an individually controllable manner via valve assemblies. The method is implemented or performed by a computing unit or controller of the hydraulic drive system (e.g. the electronic controller 10 of Figure 1).

[0031] In this method, for each of the loads, an output volumetric flow demand 85 is determined from a given input volumetric flow demand for the load using a scaling function called pump flow scaling function 84 .

[0032] An input volumetric flow demand for the load is notably received in optional step 110. With reference to Fig. 1, the input volumetric flow demand may for example be a volumetric flow request 14 for the load obtained from an operation preset 12. Similarly, the input volumetric flow demand may be an output volumetric flow demand of a previous processing stage, notably a previous stage having a scaling function.

[0033] In step 120, an available volume flow variable of the pressure medium source is determined by the pump flow scaling function, which can for example receive a value indicative of the available volume flow variable (for example from another functional module in the control) or the pump flow scaling function can be configured to determine or calculate the available volume flow variable from sensor measurements and / or the characteristic map itself. The available volume flow variable can in particular be the available volume flow of the pressure medium source and / or the available volume flow change (in particular the volume flow increase) of the pressure medium source between successive time points. The available volume flow change is given for example by the rate of change of the volume flow of the pressure medium source. The successive time points are for example a first time point and a subsequent second time point, where the second time point is a time point at which the output-side volume flow demand of the pump flow scaling function is to be determined. It is envisaged that the available volume flow variable includes both the available volume flow and the available volume flow change. In this case, for example, the calculations can first be carried out separately, so that two preliminary output volumetric flow demands are determined for each load, and then the output volumetric flow demand for each load to be finally determined by the pump flow scaling function can be determined as a weighted sum of these preliminary output volumetric flow demands of the respective load (in this case the weights of the weighted sum are greater than zero and the sum of the weights is equal to 1).

[0034] In step 130, a proportion of the available volume flow variable is determined by the pump flow scaling function for each load, i.e. a volume flow variable proportion. This volume flow variable proportion is determined in particular such that their sum is equal to the available volume flow variable, i.e. the available volume flow variable is divided, so to speak, into the load. If the available volume flow is the available volume flow of the pressure medium source, the volume flow variable proportion corresponds to the proportion of the available volume flow. If the available volume flow variable is the available volume flow change of the pressure medium source, the volume flow variable proportion corresponds to the proportion of the available volume flow change.

[0035] In step 140, the pump flow scaling function is determined for each load from the output volumetric flow demand 85 taking into account the volumetric flow variable proportion of the load, i.e. the output volumetric flow demand of each load is determined based on the volumetric flow variable proportion of the respective load, where this determination may in particular additionally be based on the input volumetric flow demand of the respective load. If the available volumetric flow variable is the available volumetric flow of the pressure medium source, the output volumetric flow demand of the load can be set approximately equal to the volumetric flow variable proportion of this load. If the available volumetric flow variable is the available volumetric flow change of the pressure medium source, the output volumetric flow demand of the load (for the second time point) can be set approximately equal to the output volumetric flow demand of this load at the first time point + its volumetric flow variable proportion if its input volumetric flow demand is not yet satisfied. If the available volumetric flow variable is the available volumetric flow change of the pressure medium source, in particular it is assumed that the available volumetric flow change is only divided between the loads whose input volumetric flow demand is not yet satisfied. Therefore, for these loads the volume flow variable percentage is equal to zero, i.e. the output volume flow demands of these loads are equal to their input volume flow demands.

[0036] In optional step 150, the pump flow scaling function for each load determines a scaling factor 86 as the ratio between its output volumetric flow demand and its input volumetric flow demand.

[0037] The output volume flow demand 85 can be taken into account in the control of the pressure medium source. This can be done directly or indirectly. In the case of direct consideration, for example, a total volume flow demand at the pressure medium source is determined from the output volume flow demand 85 (for example as the sum of the output volume flow demands) and the pressure medium source is further controlled in such a way that the total volume flow demand is met (this control can then also take into account the pump pressure demand). In the case of indirect consideration, the total volume flow demand is not obtained directly from the output volume flow demand of the pump flow scaling function, but one (or more) further processings can be carried out, for example with further scaling functions whose input volume flow demands are the output volume flow demands of the pump flow scaling function (see FIG. 3).

[0038] For good controllability of the machine, the load volume flow or pump volume flow and the valve opening (especially of the valve assembly) are adjusted to each other when designing the machine. This adjustment is usually made for individual movements, where the load can at most receive the maximum pump volume flow, i.e. the maximum valve opening is selected accordingly. If the sum of the load demands in the combined movements exceeds the pump capacity, the individual loads cannot deliver the desired volume flow. The pump flow scaling function makes it possible in particular to achieve a controllability comparable to that in the individual movements, because the valve opening is adjusted according to the reduction or scaling factor.

[0039] Fig. 3 shows a control method according to an embodiment of the present invention. The control method relates to a hydraulic drive system with a number of hydraulic loads (also called loads for short) and at least one hydraulic machine, as shown, for example, in Fig. 1. The control method is implemented in particular by an electronic control unit of the hydraulic drive system.

[0040] First, by means of the operating device 16, e.g. one or more joysticks, levers, pedals, etc., the operating presets of the operator of the machine in which the hydraulic drive is used (i.e. load presets or operator presets for the loads) can be captured for each (hydraulic) load. From these operating presets 12, the volumetric flow demand 14 and pressure demand 22 for the load can be determined by means of appropriately defined functions or mappings, e.g. a volumetric flow mapping 18 and a pressure mapping 20. The volumetric flow demand 14 depends, for example, on the operating preset 12 in a progressive manner, i.e. with an increase in the deflection of the operating device 16, the corresponding volumetric flow demand increases more significantly than linearly. Similarly, the scaling factor 86 (possibly together with the scaling factors of other scaling functions) can also be taken into account in the drive control of the valve assembly supplying the pressure medium to the load.

[0041] From the hydraulic load volumetric flow demand 14, a hydraulic load volumetric flow demand 40 is determined in one or more successive stages, scaled by means of a scaling function 31, 32, 33, 34, 35, and for each hydraulic load one or more scaling coefficients 41, 42, 43, 44, 45 are determined. These scaling coefficients are determined as the ratio between the output volumetric flow demand and the input volumetric flow demand of a stage (for the same load), for example here five stages are shown, but generally other numbers greater than one are also possible. These stages form a sequence from the first stage to the last stage, which are identical in the case of only one stage, in particular they are equal to one stage.

[0042] From the scaled volumetric flow demands 40, a (scaled) total volumetric flow demand 50 is determined or calculated. For example, a summation map 52 may be envisaged, which sums up the scaled volumetric flow demands 40 to obtain the total volumetric flow demand 50. Furthermore, it may be envisaged that a pump pressure demand 54 is determined or calculated from the pressure demands 22. For example, it may be envisaged that it is determined or calculated using a maximum value map 56, which selects the maximum value of the pressure demands 22 as the pump pressure demand 54. Alternatively (or additionally), the pump pressure demand 54 can be fixedly pre-set or determined, for example, using a load pressure control. By means of a pump control algorithm 58, from the total volumetric flow demand 50 (taking into account the pump pressure demand 54), a control signal or control command for the pressure medium source 5, i.e. the hydraulic machine 2 and / or the drive motor 4 (in this case, for example, an electric motor) can be determined in order to satisfy the total volumetric flow demand 50. That is, the pressure medium source 5 is driven and controlled according to the total volume flow demand 50, i.e. in particular to provide a volume flow rate of pressure medium according to the total volume flow demand (wherein the pump pressure demand should also be met).

[0043] From the one or more scaling factors 41, 42, 43, 44, 45, for each (hydraulic) load a total scaling factor 60 is determined, where optionally additional parameters or variables can be taken into account, such as the number of active loads 62 and / or the motor scaling factor 64 for each of the loads (see below). The determination of the total scaling factor 60 can be done, for example, using a total scaling function 66.

[0044] From the total scaling function 60 and the corresponding operation preset 12 of the load (as shown) or from the total scaling factor 60 and the corresponding volumetric flow demand 14 of the load (not shown), for example by a preset scaling function 70 or demand scaling function, a scaled control preset 72 for the load or a control preset for the valve assembly supplying pressure medium to the load is determined, for example as the product of the total scaling factor 60 and the corresponding (i.e. assigned to the same load) operation preset 12 or volumetric flow demand 14. These control presets 72 can be converted by a valve assembly control algorithm 74 into corresponding control signals for the valve assemblies 6, whereby the drive control of the valve assemblies 6 as a whole is performed in response to the scaled control presets 72.

[0045] The scaling functions 31, 32, 33, 34, 35 of each stage respectively map the input volume flow demand for each of the loads to the output volume flow demand for each of the loads. The output volume flow demand of one stage is then the input volume flow demand of the next stage. The input volume flow demand of the first stage is the volume flow demand 14 of the load. The output volume flow demand of the last stage is the scaled volume flow demand 40 of the load. In the case of only one stage or only one scaling function, the volume flow demand 14 is the input volume flow demand of this scaling function and the scaled volume flow demand 14 is the output volume flow demand of this scaling function. Besides the dependence of the respective input volume flow demands, the scaling functions may also depend on further parameters. Such further parameters may for example be determined or determinable parameters or may be parameters captured within the operating range of the hydraulic drive (for example sensor measurements).

[0046] By means of the scaling functions 31, 32, 33, 34, 35 certain boundary conditions and / or dependencies between the variables of the hydraulic drive can be taken into account in controlling the drive of the hydraulic machine and the valve assembly, so that in particular a desired control behavior can be achieved or an undesired control behavior can be avoided. In general, different scaling functions can be provided to take different aspects into account.

[0047] A scaling function is provided, for example the fourth scaling function 34 in the figure, which determines the output volume flow demand 85 for each load based on the percentage of the available volume flow variable of the pressure medium source. This scaling function, also called pump flow scaling function 84, has already been described above, especially in relation to FIG. 2.

[0048] Further examples of possible scaling functions are briefly discussed below.

[0049] The scaling function, for example the first scaling function 31 in the figure, scales the volumetric flow demand or the volumetric flow demand of the loads based on how the volumetric flow demands of the various loads influence each other. That is, for each load, it is taken into account how much the volumetric flow demand of each other load influences, in particular how much it reduces, the output volumetric flow demand of this load. This makes it possible to achieve a desired course of the joint movement of the various loads. By means of this scaling function, which can also be called a demand reduction function, the first load demand can be reduced by the second load demand. This is advantageous, for example, if a high speed is desired for the individual movements with full joystick deflections, but a relatively low speed is desired for the combined movement of the first and second loads, each with full joystick deflections.

[0050] A scaling function, for example the second scaling function 32 in the figure, scales the volumetric flow request or demand of the load based on an input or parameter. Here, for example, the operator can adapt the volumetric flow to an attachment (for example a demolition hammer or a sweeper) by means of a parameter. The target quantities for pumps and valves can then be influenced using individual scaling factors. The output volumetric flow demand of a load arises, for example, by monotonic mapping from the input volumetric flow demand of the same load, where this mapping can depend on the sign of the input volumetric flow demand. This mapping is in particular independent of the input volumetric flow demand of other loads. The scaling or mapping can be different for different loads. This allows implementing desired characteristics of the volumetric flow demand. For example, the mapping of a load can be defined in such a way that the output volumetric flow demand initially increases linearly with its input volumetric flow demand (starting from zero) so that a limit on the load's volumetric flow demand is implemented, and when the input volumetric flow demand exceeds the limit, it is set to a constant maximum output volumetric flow demand.

[0051] A scaling function, for example the third scaling function 33 in the figure, scales the volumetric flow request or demand of the load based on the reference motor speed and the actual or set motor speed. Here, the desired volumetric flow is scaled with the drive speed of the pump or the drive motor (for example a diesel engine). If the operator selects, for example, a relatively low drive motor speed, this corresponds to the operator's request for the machine to run slower, in particular for its hydraulic load to run slower. In particular, the ratio between the controlled motor speed and the reference motor speed can be calculated and a scaling factor can be determined depending on this ratio, in which case the direction or sign of the volumetric flow demand can additionally be taken into account.

[0052] A scaling function, for example the fifth scaling function 35 in the figure, scales the volumetric flow request or demand of the load so that it does not exceed the available torque and / or available power of the drive motor. If the available power is not sufficient to meet the volumetric flow request, the requested volumetric flow must be reduced. As in the previous scaling functions, it is advantageous if the volumetric flow of the load and the valve opening are matched to each other, i.e. if the volumetric flow is reduced due to a high load and / or a lack of available power, the valve opening should also be adjusted. For the adjustment of the valve opening, a reduction or scaling factor is calculated in this function.

[0053] In particular, cases may arise where the scaling function implements a trivial mapping for at least one load, i.e. where in the scaling function for at least one load the output volumetric flow demand is equal to the input volumetric flow demand (and correspondingly the scaling factor is equal to 1).

[0054] The number of active loads 62 can be determined, for example, by a number determination function 76 (if this is taken into account when determining the total scaling factor 60). In this case, in order to obtain a continuous progression of the number of active loads 62, a percentage value can be determined for each load from its volumetric flow request, and a percentage function can be used which starts from zero, corresponds to a volumetric flow request of zero, and increases monotonically to 1 with increasing volumetric flow requests (for example, the percentage function can map all volumetric flow requests below a first threshold to zero, increase with a constant gradient from the first threshold to the second threshold to 1, and map all volumetric flow requests above the second threshold in terms of absolute value to 1). The percentage values ​​are then added up. Correspondingly, the number of active loads 62 can have a non-integer real value. There are also exceptional conditions in which it is not advantageous to follow the valve slide opening of the loads with a reduction in the volumetric flow. For example, in the individual operations, if a volumetric flow restriction based on a lack of available power occurs at the same time, it is also disadvantageous to reduce the valve opening. This exception condition (or a similar exception condition) can be recognized by using this function to determine the number of actuators, i.e. hydraulic loads, operated by the operator.

[0055] The motor scaling factors 64 (if they are taken into account when determining the total scaling factor 60) can be determined, for example, by a corresponding decision function (motor scaling decision function 78). In this case, the motor scaling factors 64 are determined on the basis of the volumetric flow requirement of the respective load and the actual or set motor speed. Here, a deceleration factor or a motor scaling factor can be predefined in order to bring about an influence on the valve opening in dependence on the speed, in particular independently for each load. In contrast to the preceding function, this function is not based on the desired volumetric flow, but solely on the drive motor speed, in particular on the internal combustion engine speed, so that a different behavior can be achieved on the vehicle. The valve reduction then depends mainly on the set speed and less on the volumetric flow.

[0056] To determine the total scaling factor 60, the total scaling function 66 evaluates the scaling factors 41, 42, 43, 44, 45 and possibly the motor scaling factor 64, for example depending on the number of active loads 62 and on determined or determinable parameters, and combines the scaling factors 41, 42, 43, 44, 45 and possibly the motor scaling factor 64 (in particular according to determined or determinable parameters). In the simplest case, the scaling factors 41, 42, 43, 44, 45 of the loads can for example be multiplied with each other to determine or calculate the total scaling factor 60 for the respective load. More generally, the individual scaling factors are combined depending on the parameters. This can be done independently of each other (i.e. with different parameters) for the various loads. Depending on the application in the machine, it is advantageous to take into account only selected scaling factors. So, for example, it is advantageous to scale the drive of the slewing mechanism with the speed of the diesel engine, whereas the lowering of the boom is advantageously not scaled, since here only gravity acts as the drive. The number of activation functions is also taken into account here in order to avoid unnecessary throttling in individual movements.

[0057] One or more of the scaling functions 31 , 32 , 33 , 34 , 35 and, possibly, the total scaling function 66 and / or the preset scaling function 70 and / or the number decision function 76 and / or the motor scaling decision function 78 can be collectively considered as a volumetric flow division function 80 .

Claims

1. 1. A method for scaling volumetric flow demands in the control of a hydraulic drive system, the hydraulic drive system comprising a pressure medium source (5) providing a volumetric flow rate of pressure medium in a hydraulic drive and a plurality of hydraulic loads (8), the hydraulic loads (8) being supplied with pressure medium in an individually controllable manner via valve assemblies (6), Using a pump flow scaling function (84) for each said load, an output volumetric flow demand (85) is determined from a given input volumetric flow demand for each said load, where the pump flow scaling function determines: - the available volume flow variable of said pressure medium source (5) is determined (120), - a volumetric flow variable proportion of the available volumetric flow variables for each of the loads is determined (130); - the output volume flow demand (85) for each said load is determined (140) taking into account the volume flow variable proportions of said loads.

2. 2. The method of claim 1, wherein the volumetric flow variable percentages for the load (8) are determined such that their sum is less than or equal to the available volumetric flow variable.

3. 3. The method according to claim 1 or 2, wherein the volume flow variable proportions are determined such that their ratio to one another is equal to the corresponding ratios of the input volume flow demands.

4. 4. The method according to claim 1, wherein the available volume flow variable is or comprises the available volume flow of the pressure medium source (5), and the output volume flow demand (85) for each load (8) is equal to a proportion of that volume flow variable.

5. 5. The method according to claim 1, wherein the available volume flow variable is or comprises an available volume flow change of the volume flow of the pressure medium source (5) between a first time point and a second time point that exists after the first time point, and wherein for each load an output volume flow demand at the first time point is given and an output volume flow demand (85) at the second time point for each load (8) is determined from its output volume flow demand at the first time point and its volume flow variable ratio, in particular the output volume flow demand at the second time point is used as the output volume flow demand of the pump flow scaling function (84).

6. 6. The method of claim 5, wherein the volume flow variable percentage for the loads where the output volume flow demand at the first time is greater than or equal to the input volume flow demand at the second time is set to zero.

7. For each said load (8) or for each said load whose volume flow variable proportion is not set to zero, the sum of the output volume flow demand at the first time point and its volume flow variable proportion is determined, The method according to claim 5 or 6, wherein the output volumetric flow demand at the second time point is determined as being equal to the minimum value from its input volumetric flow demand at the second time point and a sum determined for the load.

8. 8. The method according to claim 1, wherein a predetermined priority of the loads (8) is taken into account when determining the volumetric flow rate variable proportion.

9. 9. The method according to claim 1, wherein the output volumetric flow demand (85) of the pump flow scaling function (84) is taken into account in controlling the drive of the pressure medium source (5).

10. 10. The method according to claim 1, wherein the pump flow scaling function (84) further determines a scaling factor (86) for each load (8) as a ratio of the output volumetric flow demand (85) of each load to the input volumetric flow demand of each load, the scaling factor (86) of the pump flow scaling function being taken into account in particular in controlling the actuation of the valve assembly (6).

11. 1. A method for controlling a hydraulic drive system, the hydraulic drive system comprising a pressure medium source (5) providing a volumetric flow rate of pressure medium in the hydraulic drive system, and a plurality of hydraulic loads (8), the hydraulic loads (8) being supplied with pressure medium in an individually controllable manner via valve assemblies (6), The method comprises the following steps: receiving or determining a volumetric flow demand (14) for each of a plurality of said loads; - using one or more successive stages of scaling functions (31, 32, 33, 34, 35), where for each stage, said scaling function for each load maps the input volumetric flow demand of each load to the output volumetric flow demand of each load and determining a scaling coefficient (41, 42, 43, 44, 45) for each load as the ratio between the output volumetric flow demand and the input volumetric flow demand of each load, the output volumetric flow demand of the scaling function of one stage being used respectively as the input volumetric flow demand of the scaling function of the next stage and said volumetric flow request (14) being used as the input volumetric flow demand of the scaling function (31) of the first stage; determining (66) a total scaling factor (60) for each load based on said scaling factors (41, 42, 43, 44, 45) for each said load; determining (70) a scaled volumetric flow demand (72) for each of said loads based on said total scaling factor for each of said loads; determining a total volume flow requirement (52) from the output volume flow demands of the scaling function (35) of the last stage; controlling (74) the valve assembly (6) in response to the scaled volumetric flow demand (72); controlling (58) the pressure medium source (5) in response to the total volumetric flow demand (50); Including, A method, wherein the scaling function comprises a pump flow scaling function according to any one of claims 1 to 10.

12. A computing unit (10), comprising a processor configured to perform the method according to any one of claims 1 to 11.

13. A computer program comprising instructions for causing a computer to carry out a method according to any one of claims 1 to 11, when the program is executed by the computer.

14. A computer readable data carrier having a computer program according to claim 13 stored thereon.

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