Electro-hydrostatic drive system, method and computer unit for controlling the charging of an electrical storage device

Abstract

The invention relates to an electro-hydrostatic drive system for moving a hydraulic axle, comprising a computer unit, wherein the computer unit is designed for controlling the charging of an electrical storage device, and wherein the electro-hydrostatic drive system comprises at least one hydraulic cylinder for moving a hydraulic axle. The invention further relates to a fluid-hydraulic motor pump unit having an electric motor and a pump, which is designed to provide a fluid-hydraulic volume flow having a fluid-hydraulic pressure for moving the hydraulic cylinder. In addition, a motor control device is provided which is designed to exchange electrical power with the electric motor. Furthermore, the electro hydrostatic drive system contains a feed device which is arranged between a supply network and the motor control device. The electro-hydrostatic drive system also has an electrical storage device with a storage capacity, which is electrically connected to the feed device and the motor control device, wherein the electrical storage device is designed to exchange electrical power with the motor control device and the feed device and to store electrical energy, and a computer unit which is designed to receive at least one system parameter of a plurality of system parameters of the electro-hydraulic drive system, and to automatically determine an energy content of the electro-hydrostatic drive system for the run time based on the received system parameter, and to continuously control the determined energy content of the electrical storage device, by adjusting a power flow into the electrical storage device, in such a way that, with a reduction in the fluid-hydraulic pressure, the fluid-hydrualic and mechanical energy stored in the electro-hydrostatic drive system is regenerated and stored in the electrical storage device as electrical energy, without the storage capacity of the storage device being exceeded.

Description

[0001] Electrohydrostatic drive system, method and computing unit for charging control of an electrical storage device

[0002] Description

[0003] The present disclosure relates to an electro-hydrostatic drive system for motion, in particular force-generating motion, of a hydraulic axle, comprising a computing unit, wherein the computing unit is configured for charging control of an electrical storage device. Additionally, or alternatively, a method for charging control of an electrical storage device of an electro-hydrostatic drive system is provided. Additionally, or alternatively, a computing unit for charging control of an electrical storage device of an electro-hydrostatic drive system, comprising a motor control device, is provided. Additionally, or alternatively, a computer program is provided which includes instructions that, when executed by a computer, cause the computer to execute the method, at least partially.

[0004] Electro-hydrostatic drive systems are known in the prior art. In known electro-hydrostatic drive systems, an electrical energy storage device and / or an energy storage device can be provided to partially draw short-term high electrical power demands from the energy storage device of the drive system, thereby reducing the peak value of the power drawn from the supply network (peak load reduction).

[0005] This energy storage system can also be used to store electrical energy that is regenerated by the drive system during decompression of the pressurized fluid and the energized elastic mechanical elements, for later use. Known electrohydrostatic drive systems incorporate an electrical energy storage device designed to store all regenerated electrical energy.

[0006] Alternatively, the energy storage system can be smaller. A smaller electrical energy storage system may require the dissipation of excess electrical energy, for example, by activating a braking resistor that can release the energy as waste heat, resulting in a loss of energy usable by the drive system. Alternatively, excess regenerated electrical energy can be fed back into the electrical grid. This is undesirable in certain grids and may necessitate the use of more complex power electronics.

[0007] From EP 2 214 302 Bl, a motor drive control device is known, comprising: a power supply converter connected to an AC power supply, a voltage detector that detects a DC voltage from the power supply converter, an inverter connected to a motor, and an energy storage device connected to a DC bus that links the power supply converter and the inverter. The motor drive control device has an operating voltage determination section that determines whether the DC voltage of the power supply converter is equal to or lower than a current operating voltage set by a current operating voltage setting section.The motor drive control device has a voltage adjustment operating control section that causes the power supply converter to start current operation when the DC voltage is equal to or lower than the current operating voltage, and causes the power supply converter to stop current operation when the DC voltage has exceeded the current operating voltage.

[0008] From DE 10 2010 025 647 A1, a device and a method for intelligent grid power regulation by means of capacitive energy storage are known. The device has a DC link, which is formed via an interface with a buffer storage device that stores the voltage of a power electronics unit. Another interface is coupled to the DC link with a power supply network. This latter interface allows current flow between the power supply network and the DC link when a voltage value in the DC link is within a target voltage range. Against this background of the prior art, the object of the present disclosure is to specify an electrohydrostatic drive system with a computing unit, and / or a method for charging and controlling an electrical storage device, each of which is suitable for enriching the prior art.

[0009] The problem is solved by the features of the independent claim. The dependent and subordinate claims each contain optional further developments of the disclosure.

[0010] The task is then solved by an electro-hydrostatic drive system for the movement, in particular a force-generating movement, of a hydraulic axle. The electro-hydrostatic drive system includes a computing unit. The computing unit is designed for the charging control of an electrical storage device.

[0011] The electro-hydrostatic drive system comprises at least one hydraulic cylinder for moving, in particular force-generating, a hydraulic axis. Furthermore, a fluid-hydraulic motor-pump unit is provided, comprising an electric motor and a pump configured to supply a fluid-hydraulic flow rate at a specific pressure for moving the hydraulic cylinder. Alternatively or additionally, a force is provided. This force can be used to move the load and / or to apply process forces.

[0012] In addition, a motor control device is provided, which is designed to exchange electrical power with the electric motor.

[0013] A power supply device is provided, which is arranged, in particular, between a supply network and the motor control device. The power supply device can be configured to exchange electrical power with a supply network and an intermediate circuit.

[0014] Furthermore, an electrical storage device is provided. The electrical storage device has a storage capacity. The electrical storage device is electrically connected to the intermediate circuit and thus to the power supply device and the motor control device. The electrical storage device is designed to exchange electrical power with the motor control device and the power supply device and can store electrical energy.

[0015] A computing unit is provided which is designed to receive at least one system parameter from a multitude of system parameters of the electrohydraulic drive system and to automatically determine the energy content of the electrohydraulic drive system at runtime based on the received system parameter and to continuously regulate the determined energy content of the electrical storage device by adjusting a power flow into the electrical storage device in such a way that the fluid-hydraulic and mechanical energy stored in the electrohydraulic drive system is regenerated when the fluid-hydraulic pressure decreases and stored as electrical power in the electrical storage device without exceeding the storage capacity of the electrical storage device.

[0016] The computing unit can be part of the electro-hydrostatic drive system. The computing unit can be an electronic control unit (ECU). The computing unit can include a data processing device or a processor device configured to perform one embodiment of the disclosed method. The computing unit can include a data processing device or a processor device configured to perform one embodiment of the disclosed method. For this purpose, the processor device can include at least one microprocessor and / or at least one microcontroller and / or at least one FPGA (Field Programmable Gate Array) and / or at least one DSP (Digital Signal Processor). Furthermore, the computing unit can be configured as a PLC and / or as a software implementation.Furthermore, the processor device can include program code configured to perform the embodiment of the disclosed method when executed by the processor device. The program code can be stored in a data memory of the processor device. The processor device can be based, for example, on at least one circuit board and / or on at least one SoC (System on Chip).

[0017] For the purposes of this disclosure, an electrohydrostatic drive system is understood to be a hydraulic system in which a hydraulic fluid is used to move a load and / or to perform a force-generating movement with the hydraulic cylinder. The electrohydrostatic drive system comprises a fluid-hydraulic motor-pump unit, at least one hydraulic line for transporting the hydraulic fluid, a driven actuator (hydraulic cylinder), and a return reservoir for the hydraulic fluid. The fluid-hydraulic motor-pump unit comprises a pump and an electric motor through which the hydraulic flow rate is provided.

[0018] The hydraulic line transports hydraulic fluid between a fluid-hydraulic motor-pump unit and an actuator. The actuator can be designed as either a hydraulic cylinder or a hydraulic motor. A hydraulic cylinder converts the hydraulic flow into linear motion, while a hydraulic motor converts the flow into rotary motion. The actuator is responsible for executing a movement and applying a force, including lifting or moving a load with mass and weight, or performing a specific motion task.

[0019] For the purposes of this disclosure, a motor control device for an electro-hydrostatic drive system is understood to be an electronic circuit and / or a device configured to control and regulate an electric motor, preferably the motor-pump unit. The motor control device supplies the electric motor with the electrical power necessary for its movement. For this purpose, the motor control device includes power electronic components for switching the voltages on the phases of the motor winding and / or a control and / or regulation system for commutation of the phase currents, regulation of the motor current, and motor speed. For the purposes of this disclosure, an electrical storage device is understood to be a component with an electrical connection to a DC voltage, which absorbs electrical energy and stores it for later use.An electrical storage device can be capable of storing electrical energy in an electrical, chemical, or kinetic form and releasing it again when needed. The electrical storage device includes a storage capacity, which indicates the maximum amount of electrical energy that can be stored.

[0020] The electrical storage device can be designed as a capacitor storage system, consisting of interconnected electrolytic capacitors and / or double-layer capacitors (ultracaps) and / or accumulators and / or as a flywheel storage system. Capacitors store energy in the form of an electric field and can absorb and release high power. Accumulators store electrical energy in the form of chemical energy. Compared to capacitors, accumulators have a greater storage capacity for the same size. The energy content increases with the voltage.

[0021] A flywheel energy storage system is a storage device that stores energy in the form of the kinetic rotational energy of a flywheel. The system consists of a rotating flywheel with a motor, which can function as either a motor or a generator, and is connected to a motor control unit. The energy content increases with the rotational speed of the flywheel. Compared to capacitors, a flywheel energy storage system can offer greater energy storage capacity within the same installation space.

[0022] For the purposes of this disclosure, a feed-in device is a device that can draw at least electrical power from a supply network and convert it into DC voltage for the intermediate circuit and, depending on the embodiment, may also feed electrical power into the supply network.

[0023] For the purposes of this disclosure, a braking resistor is an electrical resistor that is connected to the DC link via a switch to convert electrical power into heat. It is switched on when a certain maximum voltage is exceeded in order to protect the electrical storage device and / or the DC link from overvoltage. The generated heat represents wasted energy for the electro-hydrostatic drive system and is not usable.

[0024] For the purposes of this disclosure, the compression energy of the electrohydrostatic drive system is the amount of stored energy generated by the pressure of the compressed hydraulic fluid within the electrohydrostatic drive system. The stored energy is determined by the hydraulic pressures of the cylinder chambers and the pressurized, enclosed fluid volumes. Furthermore, the stored energy is determined by the spring energy of the elastic mechanical elements that are subjected to force by the hydraulic cylinder.

[0025] For the purposes of this disclosure, the regenerated compression energy is the compression energy converted into electrical energy by the motor pump unit.

[0026] For the purposes of this disclosure, electrical power is understood to be the physical quantity that indicates how much electrical energy is converted or transferred per unit of time.

[0027] The electro-hydrostatic drive system with the computing unit described above offers a number of advantages.

[0028] The usable amount of stored energy in the electrical energy storage device, which can be used to store regenerated compression energy for later use by the electro-hydrostatic drive system, can be increased without increasing the storage capacity of the energy storage device.

[0029] Compared to a state-of-the-art solution, given a specific storage capacity of the electrical energy storage device, the need for either feeding energy back into the grid or dissipating regenerated electrical compression energy during force reduction can be completely or partially eliminated. This reduces the required electrical energy for the entire force-building motion cycle and increases the system's energy efficiency. Furthermore, if excess electrical energy is dissipated as waste heat by activating a braking resistor, the resistor can be smaller or eliminated entirely, thus generating less waste heat.

[0030] Feeding power back into the grid can be partially or completely omitted without generating additional losses through power dissipation. If feed-in is eliminated, the feed-in device can be designed more simply. Feed-in is considered undesirable due to the risk of disruptions to the quality of the grid or regulatory requirements.

[0031] Alternatively, the electrical storage device would have to be designed with a larger storage capacity in order to avoid the discharge of electrical energy during power reduction without the disclosed method.

[0032] Rather, the electrical storage device can be controlled proactively by the disclosed method in order to maintain reserves for storing regenerated compression energy at all times and thus increase the amount of storable regenerated electrical energy when pressure drops.

[0033] Possible further developments of the electrohydrostatic drive system described above are explained in detail below.

[0034] The motor control device may also be configured to exchange electrical power with the power supply device and the electrical storage device. If required, power can be supplied to the motor control device via the DC link from the power supply device and the electrical storage device to drive the motor-pump unit. The motor control device can convert (regenerate) power from the electro-hydrostatic drive system back into electrical power and feed it into the DC link when the motor-pump unit is to be operated as a generator. This power can be fed into the grid by the power supply device (grid regeneration) or used to charge the electrical storage device.Alternatively or additionally, this power can be supplied to other motor control devices connected to the intermediate circuit. The energy efficiency of the electro-hydrostatic drive system can be increased through the generator-like operation of the motor-pump unit and the power exchange with the electrical storage device and the feed-in device.

[0035] The system parameter may include at least a fluid hydraulic pressure. A pressure sensor may be placed in the hydraulic line and / or on the hydraulic cylinder and / or on a hydraulic control block to detect the pressure of the hydraulic fluid.

[0036] Using the measured pressure as a system parameter, the amount of stored compression energy in a cylinder chamber can be determined. The stored compression energy E hcan be calculated from the pressure p and a known bulk modulus K of the known fluid volume V enclosed under pressure. o accordingly to be determined.

[0037] Alternatively, the stored energy can be determined from the system parameter using a table (look-up table) that contains the amount of stored compression energy for specific pressure values.

[0038] The table values ​​can be empirically determined through analysis or measurement. For set pressures, the compression energy can be measured by measuring the regenerated electrical energy during pressure reduction; for example, this can be done by integrating the speed and torque values ​​available in the motor control device over time.

[0039] From the determined amount of stored compression energy, it is possible to calculate how much storage capacity must be available in the electrical storage device to store the compression energy whenever needed. It may be possible to take into account losses occurring during the conversion of hydraulic power to electrical power in the DC link, which take place in the motor-pump unit and the motor control device.

[0040] The disclosed method makes it possible to keep the sum of the energy stored in the energy storage device and the compression energy present in the system, which can be regenerated, approximately always equal to the storage capacity of the electrical energy storage device.

[0041] Alternatively or additionally, the pressure and / or cylinder force can be determined from the torque of the electro-hydrostatic drive system. The torque of the motor of the motor-pump unit can be determined via the motor control device using the known motor phase currents of the electric motor. Additionally, the effects of the acceleration of the motor-pump unit and losses of the hydraulic motor-pump unit on the measured torque can be taken into account.

[0042] The system parameter may include a force measured by the electro-hydrostatic drive system. A force transducer can be installed directly between the actuator and the load. This transducer can directly measure the force exerted on the actuator.

[0043] It may be possible to include the position of the hydraulic cylinder piston as a system parameter. Since the volume of the pressurized fluid influences the compression energy, the position can be advantageously used to determine the stored compression energy more accurately.

[0044] The system parameter can be configured to contain information about the machine's process step, such as the specified force in a press cycle. This allows for a simplified calculation of the amount of stored compression energy. This information can be obtained through measurements and reference runs in the individual process steps.

[0045] The system parameter may include a force provided by the electro-hydrostatic drive system. The force provided by the electro-hydrostatic drive system may be determined by means of at least one pressure sensor and at least one load cell. A combination of these means may also be used.

[0046] During a reference run, the compression energy in the electro-hydrostatic drive system can be recorded for measured forces and stored in a table. Using this table, the compression energy can be determined for a given measured force value, possibly by interpolation between table values. From the determined compression energy, a target value for the energy content of the electrical storage device can be specified, which is achieved by reducing power consumption from the supply network. This can also be achieved by controlling the electrical storage device to a target voltage and adjusting the power flow of the power supply device.

[0047] It may be provided that the system parameter includes the torque of the motor pump unit, determined by the motor control device from the phase currents of the servo motor, as a measure of the hydraulic pressure.

[0048] The power supply device draws electrical power from the supply network and makes it available to the devices connected to the intermediate circuit.

[0049] Furthermore, the power supply device can be configured to feed power back into the grid (feedback). The power supply device can be integrated as a component within the motor control device. In particular, the power supply device can convert an AC voltage into a DC voltage for the intermediate circuit. The intermediate circuit connects the power electronics (at least one motor control device, energy storage device, and power supply device) and enables bidirectional energy exchange (a device can supply / receive energy). With multiple motor control devices, power can be exchanged between them via the intermediate circuit.

[0050] Furthermore, the feed-in device can be used to change the amount of power fed in from the grid. The feed-in device adjusts the power output via a control loop by regulating the current exchanged with the grid. By adjusting the power output, the energy content of the connected electrical storage device can be changed.

[0051] It may be provided that the feed-in device is designed to regulate the energy content of the electrical storage device to a predetermined value by adjusting the power fed in from the supply network.

[0052] It can be provided that the processing unit, based on the determined system parameter, supplies a target voltage to the power supply device such that the power supplied by the power supply device is adjusted accordingly. The target voltage can include the voltage value of the connected electrical storage device. Furthermore, this target voltage can be determined from a desired energy content of the electrical storage device, which takes into account the stored compression energy and the maximum storage capacity of the electrical storage device.

[0053] It may be provided that the motor control device is further designed to exchange electrical power with the power supply device and the electrical storage device.

[0054] The electrical storage device can be configured to store regenerated compression energy and not discharge any energy into the power grid and / or other consumers. The other consumer can be a motor and / or braking resistor. The regenerated compression energy is provided via the motor control device. Excess electrical energy, which would be lost in prior art methods, is recovered and stored instead of being fed back into the power grid and / or dissipated as heat by activating a braking resistor.

[0055] It may be provided that the specified energy content of the electrical storage device is reduced according to the system parameter.

[0056] In particular, the target voltage of an electrical storage device implemented by capacitors or accumulators can be reduced such that a corresponding storage capacity for storing regenerated compression energy is available in the electrical storage device. In particular, the target rotational speed of an electrical storage device implemented as a kinetic energy storage device can be reduced such that a corresponding storage capacity for storing regenerated compression energy is available in the electrical storage device.

[0057] The electro-hydrostatic drive system may include an electrical converter device located between the power supply device and the electrical storage device, which converts the voltage between them. This converter can control the power flow between the power supply device and the electrical storage device in both directions.

[0058] The processing unit can be configured to provide a target voltage to this converter device based on the determined system parameter, thus ensuring that the exchanged power is adjusted accordingly. The target voltage can include the voltage value of the connected electrical storage device. The electrical converter device can be designed as active power electronics with current control and, consequently, control of the exchanged electrical power.

[0059] The storage device may include at least one electrical capacitor. Capacitors can absorb and release high electrical power. Furthermore, capacitors have a long lifespan.

[0060] The storage device may include at least one accumulator. Accumulators can store a large amount of electrical energy in a given volume. The stored energy E el The storage device is determined when the electrical capacitance C is known. el of the capacitor or the accumulator for voltage U to Eel = ~2Cel U 2 .

[0061] The storage device may include at least one kinetic energy storage device. In this case, kinetic energy is stored through the rotation of a body (flywheel storage). A flywheel storage device consists of a drive motor with a mechanically connected flywheel, which is operated at a speed controlled by a motor control device. The flywheel's drive motor can operate as a motor to store energy and as a generator to extract energy.

[0062] At nominal speed a) nom The flywheel energy storage system has reached its storage capacity. The stored kinetic energy as a function of the moment of inertia J. kin and the rotational speed co of the flywheel storage is determined accordingly

[0063] F E kin — - 2 J Ikin < w i 2 ■

[0064] It is possible for the storage device to comprise a combination of the aforementioned types of storage devices. This can compensate for corresponding disadvantages and provide an electrical storage device that is more efficient and has improved storage characteristics.

[0065] The electro-hydrostatic drive system may include a switchable braking resistor. This resistor is activated when the DC link voltage becomes too high and, by converting electrical energy into heat, prevents excessively high DC link voltages that could damage components. The braking resistor requires cooling and must be of a size appropriate to the amount of energy converted.

[0066] The above can be summarized in other words and in a possible more concrete elaboration of the disclosure as described below, whereby the following description is to be interpreted as not restricting the disclosure. The proposed method for charging the electrical energy storage device is based on the approach of calculating the sum of the amount of energy E stored in the electrical energy storage device. el and the compression energy E h to supply the energy stored in the electro-hydrostatic drive system to the storage capacity of the electrical energy storage device, based on the calculation rule

[0067] Enom

[0068] It may be possible to take into account losses occurring in the motor-pump unit and the motor control device during the conversion of hydraulic to electrical power at the intermediate circuit when determining efficiency, for example by using the factor r) as the efficiency. For a motor-pump unit and motor control device without losses, the efficiency is rj = 1.

[0069] The electrical energy storage device has the storage capacity E nom on.

[0070] Given a known compression energy and storage capacity of the electrical storage device, a calculation rule for the required energy storage content of the electrical storage device can be derived, according to the calculation rule.

[0071] Eel — E nom — T) E h .

[0072] The determined value is the target value for the energy content of the electrical storage device, which is to be achieved by regulating the power flow into the energy storage device.

[0073] The compression energy can be determined for known system parameters, for example, using a simplified physical model. For instance, the compression energy resulting from the compression of a hydraulic fluid with bulk modulus K, stored at pressure p in a volume VO, can be calculated according to the following formula:

[0074] For an electrical energy storage device designed with a capacitor or accumulator as an energy storage device, the amount of energy E stored therein can be el from the known electrical capacitance C el and voltage U to

[0075] 1

[0076] Eel = 2 C el U to be determined.

[0077] For the nominal voltage U nom For a filled energy storage device 140, the storage capacity E is accordingly obtained. nom to p Lnom = - 2 C IInom 2 ■

[0078] A simple rule for specifying the voltage U ref The electrical storage device results as follows,

[0079] >

[0080] To determine the requirement, the hydraulic capacity C must be calculated. h the cylinder chamber under pressure and the electrical capacitance C el of the energy storage.

[0081] This can be described as a control loop with the measured variable pressure of the cylinder chamber under high pressure p and the set voltage U ref The electrical energy storage system consisting of capacitors or accumulators can be considered a control variable.

[0082] In the ideal case of linear system properties, the relationship between hydraulic capacity, enclosed fluid volume and bulk modulus is as follows:

[0083] C C h - - V o / / K' and it is advantageous to consider the change in volume V o The cylinder chamber under consideration should be taken into account as a further system parameter by measuring the piston position.

[0084] The method can be extended analogously to several cylinder chambers under pressure by summing the hydraulic compression energies determined from the cylinder chambers.

[0085] The method can additionally or alternatively take into account the mechanical spring energy stored in the mechanical elastic components under the influence of the hydraulic cylinder's force. This spring energy can be determined from the measured cylinder force as a component of the compression energy. The cylinder force can be determined from the pressures of the hydraulic cylinder's chambers.

[0086] If the electrical storage device is electrically connected to the DC link, the determined voltage can be specified as the setpoint for the voltage control, which changes the power supplied from the supply network as the manipulated variable of the control loop in order to adjust the voltage of the DC link to the setpoint.

[0087] If the electrical storage device is electrically connected to the DC link via a voltage converter, the measured voltage can be set as the setpoint for the voltage control of the energy storage device. The voltage converter adjusts the input power as a manipulated variable to maintain the voltage of the energy storage device as a controlled variable, thus keeping it within the setpoint.

[0088] In this case, no active feed-in device with the ability to control the fed-in electrical power is required.

[0089] When a flywheel energy storage system is used as an electrical storage device, the energy stored in it can be derived from the moment of inertia J. kin and the measured rotational speed co of the flywheel can be determined

[0090] Similarly, a calculation rule for specifying the rotational speed of the flywheel can be derived from this. which is transmitted to the engine control unit as the target speed of the flywheel. A speed control loop adjusts the engine torque to maintain the target speed.

[0091] In this case, no active feed-in device with the ability to control the fed-in electrical power is required.

[0092] The procedure can be executed in a program code in a controller or in an electronics with a processor unit integrated into the motor control device or the power supply device.

[0093] The method can be implemented as a control loop, comprising the target voltage of the electrical storage device as the manipulated variable and the system parameter as feedback. The system parameter includes at least the pressure of a cylinder chamber. The method can be implemented in program code within a controller or in electronics with a processor unit integrated into the motor control device or the power supply device.

[0094] Furthermore, a method for charging an electrical storage device of an electro-hydrostatic drive system is provided. The method can comprise several process steps. In a first process step, at least one system parameter from a plurality of system parameters of the electro-hydrostatic drive system is received. In a further step, the energy content of the electro-hydrostatic drive system is determined based on the received system parameter.In a further step, the determined energy content of the electrical storage device is continuously regulated by adjusting a power flow into the electrical storage device in such a way that fluid hydraulic and mechanical energy stored in the electro-hydrostatic drive system is regenerated and stored as electrical power in the storage device when the fluid hydraulic pressure decreases, without exceeding the storage capacity of the electrical storage device.

[0095] Furthermore, a computing unit for charging control of an electrical storage device of an electro-hydrostatic drive system, comprising a motor control device, is provided. The computing unit includes an interface configured to receive a system parameter of an electro-hydrostatic drive system. Additionally, a processor unit is provided, configured to determine the energy content of the electro-hydrostatic drive system based on the received system parameter.Furthermore, the processor unit is designed to continuously regulate the determined energy content of the electrical storage device by adjusting the power flow into the electrical storage device, so that the fluid-hydraulic and mechanical energy stored in the electro-hydrostatic drive system is regenerated as electrical power in the storage device when the fluid-hydraulic pressure decreases, particularly at any time, without exceeding the storage capacity of the electrical storage device. A computer program is also provided, comprising instructions that, when executed by a computer, cause it to at least partially execute the above-described procedure.The program code of a computer program can be in any form, particularly code suitable for the processing unit of electrohydrostatic drive systems. What was described above with reference to the electrohydrostatic drive system and the process also applies analogously to the computer program, and vice versa.

[0096] The disclosure also includes combinations of features from the described embodiments. Thus, the disclosure also includes realizations that each exhibit a combination of features from several of the described embodiments, provided the embodiments have not been described as mutually exclusive. The above embodiments and further developments can be combined with one another as appropriate. Further possible embodiments, further developments, and implementations of the disclosure also include combinations of features of the disclosure described previously or subsequently with respect to the exemplary embodiments, even if not explicitly mentioned. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present disclosure.In particular, features of the method claims can be implemented and / or carried out by corresponding components of the computing unit and / or the electrohydrostatic drive system, thereby supplementing or extending their functionality. Thus, the person skilled in the art will also consider aspects of the method claims for the computing unit or the electrohydrostatic drive system. Furthermore, aspects of the computing unit and / or the drive system can be implemented through functional features in the method.

[0097] The term "may" refers in particular to optional features of the disclosure. Accordingly, there are also further developments and / or embodiments of the disclosure that additionally or alternatively exhibit the respective feature(s). From the combinations of features disclosed herein, isolated features can also be selected as needed and, by dissolving any structural and / or functional relationship that may exist between the features, used in combination with other features to define the subject matter of the claim.

[0098] Detailed description

[0099] The following detailed description of the figures provides a non-restrictive account of exemplary embodiments with their features and further advantages, illustrated schematically and by way of example:

[0100] Fig. 1 shows a representation of the hydraulic part of an electrohydrostatic drive system according to the disclosure;

[0101] Fig. 2 shows a representation of the power electrical part of a control system for the electrohydrostatic drive system according to the disclosure;

[0102] Fig. 3 shows a further representation of an electrohydrostatic drive system according to the disclosure;

[0103] Fig. 4 is a representation of a computing unit as revealed;

[0104] Fig. 5 shows a flowchart of a process according to the disclosure;

[0105] Fig. 6 shows a representation of a force-building movement sequence of the

[0106] Stempels a press (position and force over time);

[0107] Fig. 7 shows a representation of the system parameters of the electrohydrostatic drive system according to the disclosure; the calculated power flows, the specified and actual values ​​of the intermediate circuit voltage and the pressure of the upper cylinder chamber as system parameters with charging control of the electrical storage device according to the disclosure for the motion sequence shown in Fig. 6; Fig. 8 shows a representation of the force-building motion sequence in the electrohydrostatic drive system according to the disclosure (position and force over time) of a piston pressing on a spring element;

[0108] Fig. 9 shows a representation of the calculated power flows, the specification and

[0109] Actual values ​​of the intermediate circuit voltage and the pressure of the upper cylinder chamber as system parameters with the charging control of the electrical storage device for the movement sequence shown in Fig. 8;

[0110] Fig. 10 shows a representation of the calculated power flows, the specification and

[0111] Actual values ​​of the intermediate circuit voltage and the pressure of the upper cylinder chamber as system parameters with a charging control of the electrical storage device known in the prior art for the movement sequence shown in Fig. 8;

[0112] The accompanying drawings are intended to provide a further understanding of the embodiments of the disclosure. The illustrated embodiments serve to explain the principles and concepts of the disclosure in connection with its description. Other embodiments and many of the advantages mentioned will become apparent with reference to the drawings. The elements of the drawings are not necessarily shown to scale. In the figures of the drawing, identical, functionally equivalent, and similarly acting elements, features, and components are to be designated with the same reference numerals unless otherwise stated.

[0113] Fig. 1 shows a representation of an electro-hydrostatic drive system 100 according to the disclosure. The electro-hydrostatic drive system 100 includes a computing unit 150. The computing unit 150 is designed for charging control of an electrical storage device 140 (shown in Fig. 2). The computing unit 150 can be part of the electro-hydrostatic drive system 100. Alternatively, the computing unit 150 can be located centrally and communicate with the electro-hydrostatic drive system via a suitable communication medium. The computing unit 150 can have corresponding interfaces 151 for data communication. The electro-hydrostatic drive system 100 also includes a hydraulic cylinder 110. The hydraulic cylinder 110 can be configured as a single-acting hydraulic cylinder, a double-acting hydraulic cylinder, a synchronous cylinder, or a differential cylinder.This list is not exhaustive. Further variants of a hydraulic cylinder 110, not mentioned here, may be provided for the electro-hydrostatic drive system 100. The electro-hydrostatic drive system 100 may be intended for pressing applications.

[0114] The electro-hydrostatic drive system 100 further comprises a fluid-hydraulic motor-pump unit 120. The fluid-hydraulic motor-pump unit 120 includes an electric drive 121 and a pump 122. The electric drive 121 and the pump 122 are rigidly connected to each other via a shaft. The electric drive 121 can be operated as a motor or as a generator. The electric drive 121 can be designed as a servo motor.

[0115] The fluid-hydraulic motor pump unit 120 provides a fluid-hydraulic flow rate for moving the hydraulic cylinder 110. A load 170 with a mass is attached to the hydraulic cylinder 110. A weight force and / or other external forces can act on the load, for example, through spring elements that connect the load to stationary points.

[0116] The Last 170 can be configured in a press application as a ram with mass, which performs a movement in some areas without external pressing force and, upon contact with a workpiece, initiates a force-generating movement. To generate a high force, the fluid is pressurized (typically 150 to 500 bar) in a cylinder chamber.

[0117] The hydraulic circuit can be supplied with fluid (hydraulic oil) at low pressure (typically 2 to 20 bar) from a pre-charge circuit, represented as volume flow source 124, to compensate for the reduced fluid volume on the low-pressure side of the fluid-hydraulic motor pump unit 120 when force is built up due to compression of the fluid. Additional low-pressure fluid is drawn in through the check valves 123, which then open. This applies a pre-charge pressure to both ports of the pump 122 to prevent cavitation when the pump 122 draws in the fluid and to clamp the hydraulic cylinder 110 with at least this pre-charge pressure.

[0118] The volume that can arise during force reduction and thus during decompression of the fluid in a chamber can be discharged into the pre-tensioning circuit via an artificial leakage between the cylinder chambers and the tank or pre-tensioning circuit, or by actively opening the check valves 122 (not shown).

[0119] The fluid hydraulic motor pump unit 120 can be controlled according to a predetermined position of the load and / or the force of the hydraulic cylinder 110 and / or the cylinder pressures of the hydraulic cylinder 110.

[0120] The electric drive 121 is controlled by a motor control device 130. The motor control device 130 is designed to exchange electrical power with the electric drive 121. Electrical power can be supplied to the electric drive 121 by the motor control device 130. Furthermore, electrical power can be received from the electric drive 121 by the motor control device 130. The motor control device 130 provides a rotating electric field for the electric drive motor 121.

[0121] Furthermore, an electrical storage device 140 is provided with reference to Fig. 2. The electrical storage device 140 has a specific storage capacity, which can be selected according to the application, the technical configuration of the electro-hydrostatic drive system 100, and / or economic considerations. The electrical storage device 140 can be designed using capacitors, accumulators, and / or a kinetic energy storage device. The electrical storage device 140 is electrically connected to the motor control device 130 and the power supply device 180. The electrical storage device 140 is designed to exchange electrical power with the motor control device 130 and the power supply device 180. The electrical storage device 140 is designed to store electrical energy.

[0122] The charge of the electrical storage device 140 can be adjusted by the feed-in device (180) with electrical energy from the supply network in order to adjust the energy content of the electrical storage device 140 in order to maintain the reserve.

[0123] The charging control ensures that sufficient reserve energy content is always maintained in the electrical storage device 140 to store the electrical energy regenerated from the compression energy during pressure reduction in the electrical storage device 140 without exceeding the storage capacity.

[0124] The computing unit 150 is designed to receive at least one system parameter from a multitude of system parameters of the electro-hydrostatic drive system 100. The system parameter can include a fluid-hydraulic pressure, a force provided by the hydraulic cylinder 110, a position of the cylinder piston 111 of the hydraulic cylinder 110, and / or a value dependent on the process step or status.

[0125] The system parameter can be detected using appropriate sensors or determined by appropriate calculation using the detected system parameters.

[0126] The computing unit 150 can automatically determine, at runtime, the energy content of the electrohydrostatic drive system 100, which is determined by compression of the fluid and application of a force, based on the received system parameter. Furthermore, the determined energy content of the electrical storage device 140 is continuously adjusted by adapting the power flow into the electrical storage device 140, so that the compression energy stored in the electrohydrostatic drive system 100 can be regenerated as electrical power in the electrical storage device 140 when the fluid-hydraulic pressure decreases, without exceeding the storage capacity. This energy can be stored for later movements.

[0127] Fig. 2 shows the structure of the electrical subsystem of the electrohydrostatic drive system 100 according to the disclosure.

[0128] The fluid-hydraulic motor pump unit 120 with the electric drive 121 and the hydraulic machine 122, which is operated and controlled by the motor control device 130, corresponds to the fluid-hydraulic motor pump unit 120 of Figure 1. The feed device 180 and the motor control device 130 as well as the electrical storage device 140 can exchange electrical power via an intermediate circuit.

[0129] The intermediate circuit is preferably designed as a DC intermediate circuit. The supply network is preferably designed as a three-phase AC network.

[0130] The feed-in device 180 can control the power exchanged between the supply network and the electrical storage device by regulating the current flow. The target voltage can be determined by a control loop from the comparison of the measured and target voltage at the electrical storage device 140. For the topology shown in Fig. 2, the DC link voltage is equal to the voltage at the electrical storage device 140.

[0131] In motor mode, the motor control device 130 draws its electrical power for the fluid-hydraulic motor pump unit 120 from the intermediate circuit for the electric drive 121. In generator mode, the motor pump unit 120 can feed electrical power into the intermediate circuit via the motor control device 130. This allows hydraulic energy to be converted into electrical energy. Furthermore, other motor control devices can be connected to the intermediate circuit.

[0132] When the motor control device 130 of the motor pump unit 120 experiences a short-term high power demand, this power can be supplied from the electrical storage device 140. This advantageously results in a more even load distribution on the power supply network (peak load reduction). When the power demand of the motor control device 130 of the motor pump unit 120 is lower, the electrical storage device 140 can be recharged by the feed-in device 180. It can also be recharged by the motor control device 130 when hydraulic energy is regenerated. Furthermore, energy regenerated by the electric drive 121 can be advantageously stored in the electrical storage device 140 of the electro-hydraulic drive system 100 without feeding it back into the power supply network 160, for later use in a movement.

[0133] The storage capacity of the electrical storage device 140 is typically limited by its design, space, and cost. The embodiment shown in Fig. 1 solves the problem of optimally utilizing a given storage capacity.

[0134] Figure 2 shows an electrical storage device 140 with capacitors as the storage technology. Without an electrical storage device 140, the power required by the motor control device 130 for the motor pump unit to generate the force-generating movement of the shaft, in addition to any losses present, must be drawn from the supply network 160 at all times.

[0135] Fig. 3 shows a further representation of an electrohydrostatic drive system 100 according to the disclosure. In the electrohydrostatic drive system 100 shown in Fig. 3, a load 170 with a mass is provided attached to the hydraulic cylinder 110, which exerts a force on a spring element 190.

[0136] The stored spring energy in spring elements 190, generated by a force applied by the electrohydrostatic drive system 100, can be considered in addition to the stored compression energy in the fluid. The spring elements 190 can represent the elasticities of a machine frame and / or be a clamped spring element. When the elastic element deforms, deformation energy is stored in this element.

[0137] Fig. 4 shows a representation of a computing unit 150 according to the disclosure. The computing unit 150 for charging control of an electrical storage device 140 of an electro-hydrostatic drive system 100 comprising a motor control device 130 has an interface for communication and / or data exchange. The first interface 151 is provided for receiving a system parameter of an electro-hydrostatic drive system 100. The first interface 151 can be configured as a serial or parallel interface or as an interface for wireless operation. The computing unit 150 can be a processor unit.

[0138] The processor unit 152 is configured to determine the energy content of the electro-hydrostatic drive system 100 based on the received system parameter. Furthermore, the processor unit 152 is configured to continuously regulate the determined energy content of the electrical storage device 140 by adjusting the power flow into the electrical storage device 140, such that the compression energy stored in the electro-hydrostatic drive system 100 is regenerated as electrical energy in the storage device 140 when the fluid hydraulic pressure decreases (decompression), without exceeding the storage capacity of the electrical storage device 140. The computing unit 150 includes a storage unit 153, which is configured to store necessary and / or corresponding data and information.

[0139] 153 can be trained using known technologies.

[0140] Fig. 5 shows a flowchart of a method 300 according to the disclosure. The method V for charging control of an electrical storage device 140 of an electrohydrostatic system 100 comprises several process steps in the illustrated embodiment. In a first process step 310, at least one system parameter of a plurality of system parameters of the electrohydrostatic system 100 is received.

[0141] In a further process step 320, the compression energy of the electrohydrostatic system 100 is determined based on the received system parameter. From this compression energy, a target value for the amount of energy stored in the electrical storage device is determined.

[0142] In a further process step 330, the energy content of the electrical storage device 140 is continuously regulated (charge control) by adjusting a power flow into the electrical storage device 140 in such a way that compression energy stored in the electro-hydrostatic drive system 100 is regenerated and stored as electrical power in the storage device 140 when the fluid hydraulic pressure decreases, without exceeding the storage capacity of the electrical storage device 140.

[0143] The method uses, for example, pressures in the chambers of the hydraulic cylinder to determine the amount of compression energy that can be regenerated into electrical energy.

[0144] The method uses the known storage capacity of the electrical energy storage device 140 and determines the amount of stored energy by measuring the voltage in the case of capacitors or accumulators, or by measuring the rotational speed in the case of flywheel storage devices.

[0145] To determine the regenerated compression energy, losses that occur during the conversion of hydraulic to electrical energy in motor 120, pump 121 and the motor control unit 130 can be taken into account.

[0146] The determination of the amount of stored energy is shown for an electrical energy storage device 140 designed with capacitors as energy storage devices. The amount of stored energy E el This results when the electrical capacitance C is known. el of the capacitor and voltage U

[0147] For the maximum voltage U nomFor a filled energy storage device 140, the storage capacity E is accordingly obtained. nom to

[0148] The charging control is based on the idea of ​​supplying the storage capacity with the sum of the stored energies in the energy storage device 140 and the energy stored as compression energy in the electrohydrostatic drive system 100, in accordance with the goal fnom — fei + fh '

[0149] Given a known compression energy E h Can a regulation for specifying the voltage of the energy storage device be derived from this?

[0150] When using a model to determine the compression energy E hA rule for specifying the voltage of the energy storage device can be determined. Under the simplified assumption that the compression energy is generated by the compression of the hydraulic fluid with linear bulk modulus K, which is under pressure p in a volume V. o When set, the stored energy is approximately given by

[0151] From this, the simple rule for specifying the voltage U can be derived. ref the electrical storage device 140 can be derived:

[0152] The voltage of the electrical storage device can be influenced, given a power flow of the motor control device 130, by changing the power flow between the supply network 160 and the electrical storage device 140 (energy storage device), thereby controlling the state of charge of the energy storage device.

[0153] In the power electronics topology shown in Fig. 2, the voltage of the electrical storage device 140 is equal to the voltage of the intermediate circuit and can therefore be transmitted to the feed-in device 180 as a setpoint for power control. Alternatively, instead of the feed-in device 180, a DC-DC converter with active power control can be used between the intermediate circuit and the energy storage device 140 to regulate the charging of the energy content of the energy storage device 140.

[0154] The feed-in device 180 adjusts the DC link voltage to the specified target voltage by adapting the power supplied from the supply network 160. Industrially available active feed-in devices (active front ends) possess this function of measuring and controlling the DC link voltage to a target value by adjusting the power exchanged between the supply network 160 and the DC link within their power limits.

[0155] Figures 6 to 8 show the results of a simulation for the disclosed load control for a force-building motion cycle of a press with a plastic compact.

[0156] In particular, Fig. 6 shows a force-building motion sequence of the ram of a press (position and force over time), in which the axis position (upper representation) and the force applied by the cylinder (lower representation) are shown over time.

[0157] A cylindrical surface area of ​​200000 mm² 2 A moving ram mass of 5000 kg and low friction losses in the hydraulic cylinder 110 are assumed. The assumed movement cycle lasts 6 s and exerts a maximum pressing force of 490 kN, corresponding to a weight force of 500 t, on the pressed part.

[0158] The ram accelerates to a constant speed from the upper starting position towards the compact, with which it makes contact at a position of 300 mm. This generates a force and corresponding pressure in the upper chamber of the hydraulic cylinder 110. The pressing force results from the compact's behavior under load and unloading caused by the ram's movement. In the example shown, the compact is made of metal or ceramic powder, which deforms non-linearly under force.

[0159] Once the pressing force is reached, the force is held for a short time, then reduced until the piston detaches from the pressing and is accelerated upwards, continuing until it reaches the upper position.

[0160] Fig. 7 shows a representation of the system parameters of the disclosed electrohydrostatic drive system, in particular the calculated power flows, the setpoint and actual value of the DC link voltage, and the pressure of the upper cylinder chamber as system parameters with disclosed charging control of the electrical storage device. Fig. 8 shows a representation of the force-generating motion sequence in the disclosed electrohydrostatic drive system (position and force over time) of a piston pressing on a spring element. Figures 7 and 8 show results of the simulation of an electrohydrostatic drive system 100 with the power electrical component topology shown in Figure 2.An electrical energy storage device 140, designed as a capacitor with an electrical capacitance of 200 mF, is electrically connected to the DC link, which exchanges electrical power with the motor control device 130 of the motor pump unit 120. A power supply device 180 with a peak power of 100 kW draws power from the supply network 160 and feeds it into the DC link depending on the specified DC link voltage. Feeding power back into the supply network is not possible. The DC link voltage is limited to 800 V by a braking resistor, which is switched on to protect the components if the voltage exceeds 800 V plus a small switching hysteresis and dissipates power. The motor pump unit 120 operates the hydraulic cylinder 110 in a position-controlled manner.

[0161] When the charging control is applied, the force-building movement shown in Figure 6 results in the power curves shown in Figure 7 (upper area), the curve of the setpoint and actual value of the intermediate circuit voltage shown in the middle graph, and the curve of the pressure of the upper chamber of the hydraulic cylinder 110 shown in the bottom graph.

[0162] In the top graph, the power taken in by the motor control device 130 is shown as "motor pump", the power drawn from the grid as "feed-in" and the power dissipated by the brake resistor as "brake resistor".

[0163] At t=0.2s, the ram is accelerated, resulting in a positive peak in the power input of the motor pump unit 120. The pressing force builds up from t=1.5s until the desired maximum pressing force is reached at t=2.6s. This requires a comparatively high power output for the compression of the fluid and the deformation of the pressed part. Subsequently, the pressing force is maintained, requiring only the loss of power to be supplied. From t=3.4s, the pressing force is reduced by decompression of the pressure, allowing the motor pump unit 120 to regenerate electrical power and supply it to the intermediate circuit.

[0164] At t=4.0s, the piston is accelerated upwards again, resulting in a brief increase in power output. At t=5.8s, the piston is decelerated in its upper position, briefly regenerating electrical power. During travel at a constant speed without contact with the pellet, the power output is relatively low, determined by the weight and mechanical friction.

[0165] The curve of the input power compared to the power delivered to the motor control device 130 during force build-up during pressing shows that a large proportion of it is drawn from the capacitor storage.

[0166] The target voltage for the intermediate circuit, referred to as "target" in the middle graph, is reduced by the disclosed procedure (charging algorithm) at high pressure, shown in the bottom graph. The voltage target is accordingly Calculated for a nominal voltage of 770V for known electrical capacitance and hydraulic capacitance C h The voltage, designated as "actual," is set at the electrical energy storage device 140 by the voltage regulator. When force is reduced, due to pressure drop in the upper cylinder chamber, the motor pump unit 120 regenerates electrical energy, which is then supplied by the motor control device 130 to the capacitor storage device 140. This capacitor is charged, and its voltage increases accordingly. Advantageously, no loss of usable energy occurs, as would happen without a voltage drop. The intermediate circuit voltage does not exceed the permissible intermediate circuit voltage, and the braking resistor is not switched.

[0167] In practice, the nominal voltage of the charging algorithm must be chosen below, preferably minimally below, the maximum permissible voltage of the intermediate circuit, so that unforeseen side effects, such as the occurrence of braking energy, can be compensated for.

[0168] Fig. 9 shows a representation of the calculated power flows, the setpoint and actual values ​​of the DC link voltage and the pressure of the upper cylinder chamber as system parameters, with the charging control of the electrical storage device for the movement shown in Fig. 8. Fig. 10 shows a representation of the calculated power flows, the setpoint and actual values ​​of the DC link voltage and the pressure of the upper cylinder chamber as system parameters, with a charging control of the electrical storage device known in the prior art for the movement shown in Fig. 8.

[0169] Figures 9 and 10 show results of applying the method according to the disclosure for the charging algorithm to an electrohydrostatic drive system with identical construction as before (hydraulic cylinder, motor pump unit, motor control device) and a capacitor storage with 250mF, which is suitable for applying a force to an elastic spring element, for example for a test system for spring elements.

[0170] While in the previous example of a press the regenerated energy consists almost exclusively of the hydraulic compression energy of the fluid, in this case the compression energy also includes the spring energy stored in the spring element.

[0171] Since the spring stores mechanical energy with low loss, only a small amount of energy needs to be supplied from the supply network 160 with high efficiency of the components, and the feed-in device 180 is designed with low peak power, for the calculation results shown with peak power 40kW.

[0172] For a movement of the piston, as shown in the top graph in Fig. 8, which from a position of 300mm compresses a spring element with a linear force-displacement characteristic by the cylinder force shown in the middle graph, the power flow into the motor control device 130 of the motor pump unit 120 shown in the bottom graph results.

[0173] By applying the disclosed method, the energy content of the electrical energy storage device 140 is reduced with increasing force. This can be seen from the reduction in the intermediate circuit voltage applied to the capacitor storage device, shown in the middle graph of Figure 10, with increasing pressure, shown in the lower graph of Figure 10. The voltage is adjusted accordingly. calculated, where a value for the hydraulic capacity C hThe calculation is such that the fluid's compression energy and the spring energy are taken into account. The intermediate circuit voltage, whose course is shown as "actual" in the middle graph, is regulated by the voltage control through adjustment of the power drawn from the supply network 160 by the feed-in unit 180, shown as "feed-in" in the top graph, in comparison to the power requirement "motor pump" of the motor control device 130 of the motor pump unit 120.

[0174] Since feedback is assumed to be prohibited in this example, i.e., only power can be fed in, slight control errors in the voltage occur during decompression.

[0175] Figure 10 shows a comparison of the system's behavior without the disclosed charging algorithm, with a fixed DC link voltage. The power dissipated as heat at the braking resistor, labeled "braking resistor" in the top graph, between t=3s and t=4s results from the braking resistor being switched on when the permissible DC link voltage of 800V is exceeded. This increases the system's energy consumption for the entire movement sequence.

[0176] Reference symbol list

[0177] 100 electro-hydrostatic drive system

[0178] 110 hydraulic cylinders

[0179] 111 Position of the hydraulic cylinder

[0180] 120 fluid hydraulic motor pump unit

[0181] 121 electric drive

[0182] 122 Pump

[0183] 123 check valves

[0184] 124 Volume flow source

[0185] 130 Engine control unit

[0186] 140 electrical storage device

[0187] 150 computing units

[0188] 151 Interface

[0189] 152 processor units

[0190] 153 storage units

[0191] 160 supply network

[0192] 170 Last

[0193] 180 Feed device

[0194] 190 spring element

[0195] 300 procedures

[0196] 310-333 Procedural steps

Claims

Patent claims 1. Electro-hydrostatic drive system (100) for moving a hydraulic axis, with a computing unit (150), wherein the computing unit (150) is designed for charging control of an electrical storage device (140), and wherein the electro-hydrostatic drive system (100) comprises at least: - a hydraulic cylinder (110) for moving a hydraulic axle; - a fluid hydraulic motor pump unit (120) with an electric motor (121) and a pump (122) designed to provide a fluid hydraulic flow rate with a fluid hydraulic pressure for moving the hydraulic cylinder (110); - a motor control device (130) designed to exchange electrical power with the electric motor (121); - a feed-in device (180) arranged between a supply network (160) and the motor control device (130); - an electrical storage device (140) with a storage capacity, which is electrically connected to the power supply device (180) and the motor control device (130), wherein the electrical storage device (140) is configured to exchange electrical power with the motor control device (130) and the power supply device (180) and to store electrical energy, and - a computing unit (150) designed to receive at least one system parameter from a plurality of system parameters of the electrohydraulic drive system (100) and to automatically determine, at runtime, an energy content of the electrohydraulic drive system (100) based on the received system parameter and to continuously regulate the determined energy content of the electrical storage device (140) by adjusting a power flow into the electrical storage device (140) such that the fluid-hydraulic and mechanical energy stored in the electrohydraulic drive system (100) is replenished when the The fluid hydraulic pressure is regenerated in the electrical storage device (140) and stored as electrical power without exceeding the storage capacity of the electrical storage device (140).

2. Electro-hydrostatic drive system (100) according to the immediately preceding claim, wherein the motor control device (130) is further configured to exchange electrical power with the power supply device (180) and the electrical storage device (140).

3. Electro-hydrostatic drive system (100) according to the immediately preceding claim, wherein electrical power is regenerated and stored in the electrical storage device (140) without returning energy to the supply network (160) and / or discharging it via a further electrical consumer.

4. Electro-hydrostatic drive system (100) according to at least one of the preceding claims, wherein the feed-in device (180) is designed to actively regulate the energy content of the electrical storage device (140) by adjusting the power fed in from the supply network (160).

5. Electro-hydrostatic drive system (100) according to at least one of the preceding claims 1 to 2, wherein the electro-hydrostatic drive system (100) comprises a converter device (200) arranged between the power supply device (180) and the electrical storage device (140), and which is designed to actively regulate the energy content of the electrical storage device (140) by adjusting the charging / discharging power.

6. Electro-hydrostatic drive system (100) according to at least one of the preceding claims, wherein the system parameter is a fluid-hydraulic pressure, a force provided by the electro-hydrostatic drive system (100), a position of the cylinder piston (111) of the hydraulic cylinder (110), the torque of the motor-pump unit determined by the motor control device (130) from the phase flows of the servo motor as a measure of the hydraulic includes pressure, and / or a process-status-dependent energy content of the electrical storage device.

7. Electro-hydrostatic drive system (100) according to at least one of the preceding claims, wherein the energy content of the electrical storage device (140) is reduced according to the energy content from the fluid-hydraulic and mechanical energy content determined by at least one system parameter.

8. Electro-hydrostatic drive system (100) according to at least one of the preceding claims, wherein the electrical storage device (140) comprises at least one capacitor, one accumulator, one kinetic energy storage device, one flywheel storage device and / or a combination thereof.

9. Method (300) for charging control of an electrical storage device (140) of an electro-hydrostatic drive system (100) according to at least one of the preceding claims with a motor control device (130), comprising the following method steps: - Receiving (310) at least one system parameter of a plurality of system parameters of the electrohydrostatic drive system (100); - Determining (320) an energy content of the electrohydrostatic drive system (100) based on the received system parameter; - Rules (330) of the determined energy content of the electrical storage device (140) continuously by adjusting a power flow into the electrical storage device (140) such that fluid hydraulic and mechanical energy stored in the electro-hydrostatic drive system (100) is regenerated and stored as electrical power in the storage device (140) when the fluid hydraulic pressure decreases, without exceeding the storage capacity of the electrical storage device (140).

10. Computing unit (150) with storage unit (153) for charging control of an electrical storage device (140) of an electro-hydrostatic drive system (100) comprising a motor control device (130), with: - an interface (151) designed to receive a system parameter of an electrohydrostatic drive system (100); - a processor unit (152) configured to determine the energy content of the electro-hydrostatic drive system (100) based on the received system parameter; and wherein the processor unit (152) is further configured to continuously control the determined energy content of the electrical storage device (140) by adjusting a power flow into the electrical storage device (140) such that the fluid-hydraulic and mechanical energy stored in the electro-hydrostatic drive system (100) is regenerated in the storage device (140) when the fluid-hydraulic pressure decreases and is stored as electrical power in the electrical storage device (140) without exceeding the storage capacity of the electrical storage device (140).

11. Computer program, wherein the computer program is loadable into a storage unit (153) of a computing unit (150) according to the immediately preceding claim and contains program code sections to cause the computing unit (150) to execute the method for controlling an electrical storage device (140) of an electrohydrostatic drive system (100) according to the method claim when the computer program is executed in the computing unit (150).

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