WO2022128180A1

WO2022128180A1 - Hydraulic pump for a hydrostatic drive, and hydrostatic drive

Info

Publication number: WO2022128180A1
Application number: PCT/EP2021/071006
Authority: WO
Inventors: Steffen Mutschler; Michael Hilsch; Adrian Trachte
Original assignee: Robert Bosch Gmbh
Priority date: 2020-12-14
Filing date: 2021-07-27
Publication date: 2022-06-23
Also published as: DE102020215820A1; CN116583687A

Abstract

The invention relates to a hydraulic pump having an adjustable delivery volume for supplying a hydrostatic load with a pressure medium in a pressure-controllable manner, involving trajectory planning by means of which, for a requestable pressure of the hydraulic pump, the target trajectory, which has a flatness, and its time derivatives can be planned and can be transmitted to a pilot controller of the hydraulic pump, which pilot controller comprises an inverse model of the hydraulic pump via which a target control value of an adjusting device of the hydraulic pump can be determined on the basis of the target trajectory and its time derivatives, and the hydraulic pump can be controlled by means of this target control value. In addition, the invention relates to a hydrostatic drive comprising the hydraulic pump and a hydrostatic load which is supplied with a pressure medium by the hydraulic pump.

Description

Hydraulic pump for a hydrostatic drive, and hydrostatic drive

description

The invention relates to a hydraulic pump according to the preamble of claim 1 and a hydrostatic drive, in particular a travel drive, according to claim 16.

A traction or torque-based driving strategy has proven to be user-friendly, particularly in the off-highway area of hydrostatic travel drives. Here, an operator uses an HMI interface to specify a tensile force or torque requirement. Hydraulically, the resulting tensile force or moment is based on the pressure of the pressure medium provided by a hydraulic pump. In the case of rotary consumers, based on the pressure and depending on the displacement, the tractive force or the torque of the hydrostatic consumer or hydraulic motor coupled to the output is obtained. The other way around, a traction or torque-based drive can be implemented by means of pressure control or regulation.

Document DE 10 2014 224 337 A1, which originates from the applicant, shows a generic travel drive. Here, a control with specification of the target value of a torque at the output is implemented as a reference variable. Depending on the specification, target time profiles or trajectories are planned both from the target value and from its time derivatives, which can be implemented by the elements of the drive. The trajectories then go into a complex, inverse model of the entire hydraulic circuit - ie the hydraulic pump and the hydraulic motor. Target trajectories of the manipulated variables for reaching the target value are planned from this via a control unit. The actuating elements of the travel drive are then controlled on the basis of the setpoint trajectories. This is a high quality controller. However, the underlying model is complex. In contrast, the invention is based on the object of creating a hydraulic pump for a drive, via which the pressure for a drive can be adjusted with less effort and yet closely based on a force or torque specification. A further object of the invention is to provide a drive whose force or moment can be adjusted with less effort and closely based on a force or moment specification.

The first task is solved by a hydraulic pump with the features of claim 1, the second by a drive with the features of claim 16.

Advantageous developments of the invention are described in the dependent claims.

A first hydraulic machine, hereinafter hydraulic pump, which can be operated as a hydraulic pump and can be coupled to a drive machine, has an adjustable delivery volume and is provided for the pressure-controlled supply of pressure medium to a hydrostatic consumer of a drive, in particular a travel drive. The hydraulic pump is in particular a primary unit designed as an axial piston pump with a swash plate design. The consumer is in particular a hydraulic motor that can be coupled to an output of the drive. The hydraulic pump has a device for trajectory planning. This device can be used to plan a target trajectory that has the characteristic of flatness and its time derivatives for a requested pressure. These setpoint trajectories go into a device for pilot control of the hydraulic pump, which contains an inverse model of the hydraulic pump. By means of this device and the inverse model, a control setpoint value for an adjustment device of the hydraulic pump can be determined as a function of the setpoint trajectory and its time derivatives, and the adjustment device can thus be activated. According to the invention, at least one consumer-dependent disturbance variable is added to this pilot control. This is preferably detectable, recorded or known from a controller.

In contrast to the state of the art cited, there is therefore no need to fully model the consumer and integrate it into the inverse model. The inverse model is therefore less complex. In order to still achieve a high level of control quality, that is, a deviation of the pressure from the requested value to keep it small, the feedforward control of the consumer to the pilot control is implemented instead. In this way, a hydraulic pump is created via which the pressure for a drive can be adjusted with reduced effort and yet closely based on a force or torque specification.

In a further development, an absorption volume of the consumer, in particular of the hydraulic motor, can be controlled, detected or it can be determined from a controller, ie it is known.

Time constants of the trajectory planning depend in particular on the application, ie on a specific application of the hydraulic pump in a specific drive.

As an alternative or in addition, input saturation and/or state saturation can be taken into account in the trajectory planning device for calculating the respective trajectory.

The inverse model is based on a reduced-order model of differential equations of the hydraulic pump consisting of differential equations for describing the adjusting device and the pressure build-up (pressure build-up equation). If the adjustment device is formed by a hydraulic actuator, in particular a hydraulic cylinder, and a hydraulic valve for applying actuating pressure medium to it, as is described further below, the dynamics of a valve position can be neglected. The differential equations of the adjustment device are then derived from the respective balance of forces on the valve body and on the piston of the actuator. Alternatively, valve dynamics can be taken into account.

In a further development, the at least one consumer-dependent disturbance variable is a recorded or ascertained pressure medium volume flow of the consumer or a time derivation thereof. Alternatively, both variables mentioned, ie the pressure medium volume flow and its time derivative, can be applied as disturbance variables.

In a further development, the inverse model contains a volume flow model or a volume flow balance element, the output of which is a variable, in particular a geometric variable, which determines a setpoint delivery volume of the hydraulic pump. In case of In axial piston pumps with a swash plate design, this variable is, for example, a swivel angle of the swash plate.

According to a preferred development, at least one displacement volume flow of the hydraulic pump that is recorded or determined from the speed and size, the first time derivative of the setpoint trajectory and, as a connectable, consumer-dependent disturbance variable, the pressure medium volume flow of the consumer, are provided as inputs to the volume flow model or balance element.

In one development, the inverse model has a volume flow time derivative model or a volume flow time derivative balance element. Its output is a time derivation of a variable, in particular a geometric variable, that determines a target delivery volume of the hydraulic pump, in particular the time derivation of the above-mentioned swivel angle.

Inputs of the volume flow time derivation model or balance element are preferably at least one displacement volume flow of the hydraulic pump that is detected or determined from the speed and the size, the first time derivation of the target trajectory, a trajectory that is dependent on the second time derivation of the target trajectory, and - as switchable, consumer-dependent Disturbance variable - the time derivative of the pressure medium volume flow of the consumer.

The quality of the pilot control can be further improved if, in a further development, the inverse model contains a leakage model. This preferably takes into account at least the setpoint trajectory and its first time derivative as inputs. Outputs are preferably a leakage pressure medium volume flow, in particular of the hydrostatic drive, in particular of the hydraulic circuit consisting of at least one hydraulic pump and at least one hydraulic motor, and a time derivative of the leakage pressure medium volume flow. In a further development, this leakage pressure medium volume flow is then included in the volume flow model or balance element.

Alternatively or additionally, the time derivation of the leakage pressure medium volume flow can be included in the volume flow time derivation model or balance element in order to further improve the quality of the pilot control. An even better quality is achieved in a further development of the hydraulic pump with a control device, since model inaccuracies, uncertainties and unknown disturbance variables can be taken into account and a deviation of the pressure from the required pressure can be reduced more reliably.

For this purpose, a first comparison element is provided, via which a first difference between the target trajectory (minuend) and the detected pressure (subtrahend) can be determined. The first difference is then in turn an input into the control device.

The control device preferably maps a control strategy that allows, for example, the tractive force/torque requested by an operator to be applied to drive wheels of the drive.

In particular, a PID control device is provided for this purpose.

The PID control device is preferably designed with anti-windup with regard to saturation of the target control value and the geometric variable (in particular the swivel angle) that determines the delivery volume of the hydraulic pump. The saturation due to a limited pivoting angle can preferably be activated when the size (pivoting angle) reaches a defined limit stored in the pilot control.

In addition, the PID controller is resettable when the magnitude (pivot angle) exceeds zero since an integral part of the PID controller depends on the valve used. The desired behavior of the pressure is described by a linearized function z and its first and second time derivation.

In one development, a second comparison element is provided for processing the output of the control device and for returning it to the pilot control. Its inputs are the above-mentioned second time derivation of the target trajectory (minuend) and the output of the control device (subtrahend). An output of the second comparator is then the dependent trajectory mentioned above. In this way, the second time derivative of the target trajectory is changed from the output of the control device to the dependent trajectory. Specifically, the output of the PID controller is calculated with the highest time derivative of the target trajectory of the requested pressure, which is then the new entry into the inverse model. An advantage of this structure is that variations in the gain of the controlled system are taken into account by the inverse model. For example, for a high speed of the hydraulic pump, only a small increase in the target control value and the swivel angle is required, while a larger increase is required for a low speed.

As already indicated, in a preferred development the adjusting device has a hydraulic actuator, in particular a hydraulic cylinder. A hydraulic valve that can be actuated electromagnetically and that can be actuated with the control current is provided for this purpose. Depending on its activation, the actuator can be acted upon by a setting pressure medium volume that has a setting pressure.

For this purpose, a setpoint control pressure can be determined from a characteristic map of the hydraulic pump provided in the inverse model. The characteristic map depicts the setpoint actuating pressure as a function of the speed of the hydraulic pump, the setpoint trajectory and the variable (in particular the swivel angle) that determines the setpoint delivery volume of the hydraulic pump. In contrast, a target actuating pressure medium volume can be determined from an inverse model of the actuator that maps the target actuating pressure medium volume as a function of the time derivation of the variable (in particular swivel angle) that determines the target delivery volume.

In a further development, the hydraulic valve can be actuated electromagnetically and the inverse model contains a model of the valve via which a target control flow of the valve can be determined as a function of the target actuating pressure and the target actuating pressure medium volume. The model of the valve represents in particular the balance of forces of the magnetic force acting on the valve piston, the flow force, the actuating pressure force and, if applicable, the spring force.

A hydrostatic drive has a hydrostatic consumer that can be coupled to an output of the drive, and a hydraulic pump that is designed according to one aspect of the preceding description, is fluidically connected to the consumer in a hydraulic circuit and can be coupled to a drive machine of the drive . In particular, the drive is a travel drive and the consumer is a hydraulic motor. A traction force or torque-based driving strategy with high quality and reproducibility of the torque requested by the operator or the traction force requested by him can thus be implemented for the traction drive without the need for control. Of course, the quality and reproducibility can still be increased by the control device already introduced above and its further developments.

The hydrostatic travel drive is provided in particular for an off-highway application, in particular a mobile working machine, in particular a construction machine. The at least one consumer is in particular a secondary unit designed as an axial piston motor with a bent-axis design, in particular with a constant or adjustable displacement. Both units (primary and secondary) are fluidically connected in series. The hydraulic pump is driven by an internal combustion engine, an electrical energy store or a hydraulic pressure store or the like and converts mechanical power into hydraulic power. The at least one secondary unit converts hydraulic power into mechanical power on the output side of the drive. The process can also be reversed, so that the at least one secondary unit is braked on the output side. The hydraulic circuit of the primary and secondary unit(s) can be designed as an open or as a closed circuit. In the case of the open circuit, the low-pressure sides of the units are connected to a pressure-balanced tank, in the case of the closed circuit, the low-pressure sides of the primary and secondary unit(s) are connected directly to each other. Both circuits are preferably secured against excessive pressure via pressure relief valves. In order to increase the efficiency of the drive, a power split can be provided in which a mechanical power path is provided parallel to the hydrostatic section of the drive. An adjustment in the displacement volume of the primary and secondary unit(s) can be separate or coupled to one another. In general, the speed on the secondary side is proportional to the pressure medium volume flow.

An exemplary embodiment of a drive according to the invention with a hydraulic pump according to the invention is explained in more detail below in three drawings. Show it: 1 shows a hydrostatic drive designed as a travel drive according to an exemplary embodiment,

2 shows a simplified block diagram of a hydraulic pump of the drive according to FIG. 1 with its devices for trajectory planning, pilot control and regulation, and FIG. 3 shows a detailed block diagram of the hydraulic pump according to FIG.

According to Figure 1, a hydrostatic travel drive 1 has a drive machine 2, a first hydraulic machine 4 (hereinafter hydraulic pump) coupled thereto as an axial piston pump of swash plate design with adjustable delivery volume or pivoting angle, and a first hydraulic machine 4 (hereinafter hydraulic pump) coupled to an output 6, as an axial piston motor of bent axis design constant displacement or axis angle configured second hydraulic machine 8 (hereinafter hydraulic motor). Hydraulic pump 4 and hydraulic motor 8 are fluidically connected in the exemplary embodiment shown in a closed hydraulic circuit via working lines 10 , 12 . The hydraulic motor 8 is coupled to the output 6 via a gear 14 . In the exemplary embodiment shown, the output is an axle with wheels 16.

The drive 1 has a means 18 for detecting a geometric variable that determines the delivery volume of the hydraulic pump 4 . In the case of the design mentioned, this variable is, for example, the swivel angle a of the swash plate of the hydraulic pump 4.

In addition, a means 20 for detecting the pressure p of the hydraulic pump 4, more precisely a pressure difference Ap across the hydraulic machine 4 between the working lines 10, 12, is provided. Due to the arrangement in the hydraulic circuit and neglecting flow losses, the pressure p drops with the same magnitude of the pressure difference Ap across the hydraulic motor 8 . Furthermore, the hydraulic pump 4 has an adjustment device 22 for adjusting its swivel angle α and thus its delivery volume.

In the exemplary embodiment shown, the adjustment device is formed by an electromagnetically actuable hydraulic valve (not shown in detail) and an actuator designed as a double-acting hydraulic cylinder (also not shown in detail) that can be acted upon by actuating pressure medium. The adjustment is known in particular as electric direct adjustment or ET adjustment. A pressure medium volume flow of the hydraulic pump 4 can be continuously adjusted as a function of a control current ides, with which the hydraulic valve is controlled. A valve, in particular a pressure-reducing valve, can be provided for each adjustment direction, in particular if the hydraulic pump 4 can be swiveled through or reversed due to its zero delivery volume. The actuator is acted upon by actuating pressure medium in a manner proportional to the control current ides. The pivoting angle that occurs with a specific control current ides and the delivery volume determined therefrom is dependent on a speed n _P and the pressure difference Ap according to a characteristic map of the hydraulic pump 4 .

The hydraulic pump 4 has a control unit 24 according to the invention with devices for planning the trajectory of the pressure difference and its time derivatives, for pilot control of the hydraulic pump 4 depending on the planning of the trajectory with a feedforward control of the hydraulic motor and for regulating the pressure. The control unit 24 is signal-connected to a control unit 26 of the drive machine 2 .

FIG. 2 shows a rough structure of the control unit 24 and a first overview of its signal flows. Accordingly, the control unit 24 has an input 28 which can be connected to an interface of an HMI, for example, via which the specification of a requested pressure difference Apdes, hereinafter briefly formulated as the requested pressure Apdes, can be transferred to the control unit 24 . The pressure Apdes represents the intensive state variable of a traction force Fdes requested by an operator via the HMI or of a requested output torque Mdes of the travel drive 1 . It is thus the command or control variable that is to be set as precisely as possible via the control unit 24 . According to FIG. 2, it enters a device for trajectory planning 30, which, as flat, linearized outputs, generates a target trajectory of the pressure Apdes,™ and its two time derivatives Apdes,™, Apdes,™ s . The three setpoint trajectories Apdes, ™, Apdes, ™, Apdes, ™ enter a precontrol device 32, wherein the highest of the time derivatives Apdes, ™ can be changed beforehand by a control device 34, which is explained in more detail below .

The device for pilot control 32 contains an inverse model of the hydraulic pump 4 including its adjustment device 22 with valve and actuator according to FIG. The device for pilot control 32 has the pressure medium volume flow of the hydraulic motor as disturbance variables 8 and its time derivative. An output 36 of the pilot control supplies a control current ides, with which the valve of the adjusting device 22 is controlled and thus its actuator is acted upon by actuating pressure medium and sets a swivel angle a of the hydraulic pump 4 .

The pressure Ap that occurs is recorded and fed back to a first comparison element 38 as a subtrahend, where it is offset against the setpoint trajectory of the pressure Apdes.

The discrepancy determined in this way is included in the control device 34 designed as a PID controller. Its output is in turn connected as a subtrahend to a second comparison element 40 and is calculated there with the reference trajectory of the highest time derivative Δpdesit of the pressure. The result of this then enters the device for pilot control 32 as a changed target trajectory of the highest time derivative of the pressure and leads to a changed control current ides with which the valve of the adjustment device 22 is controlled. This then results in a new pressure Ap.

FIG. 3 resolves the device for pre-control 32 and the models and signal flows stored therein more precisely. Accordingly, an inverse model of the hydraulic pump 4 is stored in the pilot control device 32 .

This includes a characteristic map 42 of the hydraulic pump 4, in which for a rotational speed CÜP of the hydraulic pump 4, a requested setpoint trajectory of the pressure Apdes, tut and a necessary setpoint swivel angle ap.soii of the hydraulic pump 4, a necessary setpoint actuating pressure Px.soii des The actuator of the adjusting device 22 is stored.

Furthermore, an actuator model 44 is provided, in which a required setpoint actuating pressure medium volume _qsteii.soii of the actuator of the adjustment device 22 is stored for a time derivation of the setpoint swivel angle ΔP setpoint of the hydraulic pump 4 .

Characteristic map 42 and actuator model 44 are models of the engine-related components and represent in particular the engine forces, pressure forces and control pressure forces acting on the swash plate of hydraulic pump 4 . The resulting values of the required setpoint actuating pressure p _x ,soii and setpoint actuating pressure medium volume q _s teii,soii of the actuator go into a valve model 46 of the valve of the adjusting device 22 .

This represents a force balance of the forces acting on the valve body of the valve. The setpoint actuating pressure p _x , setpoint and a piston area of the actuator enter a module 48 for determining a compressive force F _p . The setpoint actuating pressure p _x ,soii and the setpoint actuating pressure medium volume q _steii ,soii of the actuator go into a module of a valve opening cross section 50 . From this, the module 50 calculates a spring force FF and a flow force Fjet. The sum of these three forces corresponds to the actuation force FM to be applied to the electromagnet of the valve of the adjustment device 22 and goes into a module for determining the actuation current 52, in which, in principle, a characteristic curve of the actuation current ides as a function of the actuation force FM is stored.

The device for pilot control 32 also contains a volume flow model 54, a volume flow time derivation model 56 and a leakage model 58.

The speed CÜP, the first time derivative of the target trajectory Apdes it, a leakage pressure medium volume flow qieck and—as a disturbance variable—the pressure medium volume flow q _mo t of the hydraulic motor 8 go into the first-mentioned model 54 . A result of the volume flow model 54 is the setpoint swivel angle ap.soii, which is included in the characteristics map 42 for the above-described determination of the setpoint actuating pressure Px.soll.

The speed CÜP, the highest time derivative of the setpoint trajectory Apdes it, the first time derivative of the setpoint trajectory Apdes, fnt, a time derivative of the leakage pressure medium volume flow q _leak and - as a disturbance variable - go into the second-mentioned model 56 Time derivation of the pressure medium volume flow q _mot of the hydraulic motor 8 a. A result of the volume flow time derivative model 56 is the time derivative of the target swivel angle ΔP setpoint , which is used in the actuator model 44 for the above-described determination of the setpoint actuating pressure medium volume q _s _teii ,soii .

The leakage pressure medium volume flow qieck and its time derivative q _leak are determined and made available by the leakage model 58 as a function of the desired trajectory Apdes it and its first time derivative Apdes. The 54, 56 and 58 models can be referred to as the 60 hydraulic model.

Activation of the valve of adjustment device 22 with activation current ides then results in pressure Ap, which, as already described with reference to FIG.

Disclosed is a hydraulic pump for supplying pressure medium to a hydrostatic consumer, in particular a hydraulic motor, of a hydrostatic drive, in particular a travel drive, with a control unit with a device for trajectory planning of a target pressure of the hydraulic pump and its time derivatives, the target trajectories being inputs to a device for pilot control, in which an inverse model of the hydraulic pump is stored, via which a setpoint control value of an adjustment device of the hydraulic pump can be determined as a function of the trajectories and the latter can thus be controlled, with at least one input into the inverse model being provided according to the invention for injecting a consumer-dependent disturbance variable.

Also disclosed is a hydrostatic drive, in particular a travel drive, which has at least one hydrostatic consumer which can be coupled to an output of the drive, which is arranged in a hydraulic circuit with a hydraulic pump of the type just mentioned and can be supplied with pressure medium by it, with the pilot control at least one state variable of the consumer is applied to the control unit of the hydraulic pump as a disturbance variable.

Claims

patent claims

1 . Hydraulic pump with adjustable delivery volume for pressure-carrying pressure medium supply to a hydrostatic consumer (8), with a trajectory plan (30), via the desired pressure (Apdes) of the hydraulic pump (4) having a flatness having a desired trajectory (Apdes, tut) and its time derivations ( Apdes, tut, Apdes, tut) can be planned and transmitted to a pilot control (32) of the hydraulic pump (4), which contains an inverse model (42, 44, 46, 60) of at least the hydraulic pump (4), via which, depending on the Target trajectory (Apdes, mt) and its time derivatives (Apdes, tut, Apdes, tut) a control target value (ip, des) of an adjusting device (22) of the hydraulic pump (4) can be determined and this can be controlled with it, characterized by an injection of at least one consumer-dependent disturbance variable (q _mot , q _mo t) to the pilot control (32).

2. Hydraulic pump according to claim 1, wherein the at least one consumer-dependent disturbance is a detected or determined pressure medium volume flow (q _mot ) of the consumer (8) or a time derivative (q _mot ) thereof.

3. Hydraulic pump according to claim 1 or 2, wherein the inverse model (42, 44, 46, 60) has a volume flow model (54) whose output is a variable (a _{P soll} ) that determines a target delivery volume of the hydraulic pump (4). is.

4. Hydraulic pump according to claim 3, wherein inputs into the volume flow model (54) include at least one recorded or determined delivery volume flow of the hydraulic pump (4) or a value (CÜP) on which this is based, the first time derivative (Apdes, tut) of the target trajectory (Apdes , does) and--as a switchable, consumer-dependent disturbance variable--the pressure medium volume flow (q _mot ) of the consumer (8).

5. Hydraulic pump according to one of the preceding claims, wherein the inverse model (42, 44, 46, 60) has a volume flow time derivation model (56) whose output is a time derivation (ä _Psoll ) of a target delivery volume of the hydraulic pump (4) determining quantity (a _{P target} ) is . Hydraulic pump according to claim 5, wherein inputs into the volume flow time derivation model (56) include at least one recorded or determined delivery volume flow of the hydraulic pump (4) or a value (CÜP) on which this is based, the first time derivation (Apdes, ) of the setpoint trajectory (Apdes it), a trajectory dependent on the second time derivative (Apdes it) of the setpoint trajectory (Apdes it) and--as a connectable, consumer-dependent disturbance variable--the time derivative (q _mot ) of the pressure medium volume flow (q _mot ) of the consumer (8). Hydraulic pump according to one of the preceding claims, wherein the inverse model (42, 44, 46, 60) includes a leakage model (58) whose inputs are the target trajectory (Apdes, fiit) and its first time derivative (Apdes, ), and the outputs of which are a leakage pressure medium volume flow (q _leak ) and its time derivative (Q(ecfc). Hydraulic pump according to claims 3 and 7, wherein a further input of the volume flow model (54) is the leakage pressure medium volume flow (q _leak ). Hydraulic pump according to claims 5 and 7, wherein a further input of the volume flow time derivative model (56) is the time derivative (q _leak ) of the leakage pressure medium volume flow (q _leak ).Hydraulic pump according to one of the preceding claims with a control device (34) via which a deviation of the pressure (Ap) can be reduced from the required pressure (Apdes) Hydraulic pump according to Claim 10 with a first comparison element (38) via which a first difference with the target trajectory (Apdes, tut) as the minuend and the pressure (Ap) a Can be determined as a subtrahend, the first difference being an input into the control device (34). Hydraulic pump according to Claims 6 and 10 with a second comparison element (40) whose inputs have the second time derivative (Apdes, tut) of the target trajectory (Apdes, tut) as the minuend 15 and an output of the control device (34) are as a subtrahend, with an output of the second comparison element (40) being the dependent trajectory. Hydraulic pump according to one of the preceding claims, in which the adjusting device (22) has a hydraulic actuator and a hydraulic valve which can be actuated with the actuation current (ides), depending on the actuation of which the actuator is supplied with an actuating pressure medium volume (q _s teii) and actuating pressure (p _x ) can be acted upon. Hydraulic pump according to Claim 3, in which the inverse model (42, 44, 46, 60) contains a characteristic map (42) of the hydraulic pump (4), from which, depending on a speed (CÜP) of the hydraulic pump (4), the setpoint trajectory ( Apdes it) and the variable that determines the target delivery volume of the hydraulic pump (a _{P so ll} ) a target actuating pressure Px, SO //) can be determined. Hydraulic pump _according to Claims 5 and 13, in which the inverse model (42, 44, 46, 60) contains a model (44) of the actuator, via which the variable ( a _{P so ll} ) a desired actuating pressure medium volume (q _s teii, soii) can be determined. Hydrostatic drive with at least one hydrostatic consumer (8), which can be coupled to an output (6) of the drive (1), and with a hydraulic pump (4), which is designed according to one of the preceding claims, in a hydraulic circuit with the consumer ( 8) is fluidically connected and can be coupled to a drive machine (2) of the drive (1).