Electrohydrostatic drive system, and method for moving a hydraulic spindle

Abstract

The invention relates to an electrohydrostatic drive system (100) for moving a hydraulic spindle, comprising a kinetic energy storage device (140), and wherein the electrohydrostatic drive system comprises at least one hydraulic cylinder (110) for moving the hydraulic spindle, in particular a hydraulic press. Furthermore, a motor-pump unit (120) is provided which comprises an electric motor (121) and a pump (122) for supplying a hydraulic volume flow for moving the hydraulic cylinder. In addition, a motor control device (130) is provided which is designed to exchange electrical power with the electric motor. Furthermore, the electrohydrostatic drive system contains a supply device (170) which is arranged between a supply grid (160) and the motor control device. The electrohydrostatic drive system also comprises the kinetic energy storage device (140), which is electrically connected to the supply device and to the motor control device, the kinetic energy storage device being designed to exchange electrical power with the motor control device and the supply device, and to store kinetic energy.

Description

[0001] Electro-hydrostatic drive system and method for moving a hydraulic axle

[0002] Description

[0003] The present disclosure relates to an electrohydrostatic drive system for moving an axle, in particular a force-generating movement of a hydraulic axle. The electrohydrostatic drive system includes a kinetic energy storage device. Additionally or alternatively, a method for controlling a kinetic energy storage device of an electrohydrostatic drive system is provided. Additionally or alternatively, a computing unit for controlling an electrical energy storage device of an electrohydrostatic 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] Electrohydrostatic drive systems are known in the prior art. In known electrohydrostatic 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 motor control device of the electrohydrostatic drive system, thereby reducing the peak value of the power drawn from the supply network.

[0005] Electromechanical servo presses are known in the prior art. These electromechanical servo presses can use kinetic energy storage devices to store and release kinetic energy generated by the high inertia of the drive shaft and the main drive motors. In electromechanical servo presses, there is no working fluid to transmit the force between the mechanical press section and the electric motor.

[0006] The kinetic energy storage system is coupled to the DC bus and is designed to store kinetic energy when other servo axes are braking. In electro-hydrostatically driven presses, passively operating working capacitors can be used to store and reuse braking and decompression energy. Using test axes, the released spring energy (of the material being tested) can be stored in a DC link capacitor via an EPU (electro-hydrostatic drive). For smaller machines with lower decompression energy, a passive capacitor can be used.

[0007] DE 10 2014 116 770 B3 relates to a test rig for testing at least one spring element, which has at least one double-acting cylinder, wherein a piston is arranged in the cylinder, dividing the cylinder into two chambers. Furthermore, at least one pump is provided, which is fluidically connected to the cylinder. The chambers and the pump form a closed fluid system, in particular a hydraulic system, wherein the pump is mechanically coupled to a drive unit that can be operated as a motor in drive mode and as a generator in power generation mode. The spring element can be clamped between the piston and a fastening means, so that a restoring force generated by the spring element during testing can be transmitted through the chambers and through the pump to the drive unit, enabling the drive unit to be operated as an electric generator.

[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 intermediate circuit, which is connected via an interface to a buffer storage device that stores the voltage of a power electronics unit. Another interface is coupled to the DC intermediate circuit with a power supply network. This latter interface allows current flow between the power supply network and the DC intermediate circuit when a voltage value in the DC intermediate circuit is within a setpoint voltage range. In the event of a power supply network failure, the buffer storage device switches off an electric drive motor.Against this background of the prior art, the purpose of the present disclosure is to specify an electrohydrostatic drive system with a kinetic energy storage device, and / or a method for controlling an electrical storage device, each of which is suitable to enrich 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 electrohydrostatic drive system for the movement, in particular a force-generating movement, of a hydraulic axle. The electrohydrostatic drive system includes a kinetic energy storage device.

[0011] The electro-hydrostatic drive system comprises at least one hydraulic cylinder for moving the hydraulic axis. The hydraulic axis can, in particular, be designed as a hydraulic press.

[0012] Furthermore, a fluid-hydraulic motor-pump unit is provided, comprising an electric motor and a pump designed to supply a fluid-hydraulic flow rate at a specific pressure to move 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.

[0013] In addition, a motor control device is provided, which is designed to exchange electrical power with the electric motor.

[0014] A power supply device is provided, which is arranged, in particular, between a power supply network and the motor control device. The power supply device can be configured to exchange electrical power with a power supply network and an intermediate circuit. Furthermore, a kinetic energy storage device is provided. The kinetic energy storage device has a storage capacity. The kinetic energy storage device is electrically connected to the intermediate circuit, in particular to the DC intermediate circuit, and thus to the power supply device and the motor control device. The kinetic energy storage device is designed to exchange electrical power with the motor control device and the power supply device and can store mechanical energy.

[0015] 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.

[0016] 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.

[0017] 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 operation. 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.

[0018] For the purposes of this disclosure, an electrical storage device is understood to be a component with an electrical connection to a direct current voltage, which absorbs electrical energy and stores it for later use. The electrical storage device may be capable of storing electrical energy in an electrical, chemical, or kinetic form and releasing it again when required. The electrical storage device includes a storage capacity, which specifies how much electrical energy can be stored.

[0019] The 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 voltage. Furthermore, compared to the electrolytic capacitors used in the prior art, mechanical storage devices have a significantly higher energy density and are therefore better suited for applications involving larger amounts of energy. Double-layer capacitors have a similar energy density to mechanical storage devices, but their lifespan is considerably shorter.Rechargeable batteries also have significantly fewer life cycles than mechanical storage devices.

[0020] For the purposes of this disclosure, a kinetic storage device is a system or subsystem of a system for storing and converting energy.

[0021] A kinetic energy storage device can store energy in the form of kinetic energy. This can be achieved through the use of rotating masses such as flywheels. These flywheels are typically made of high-density materials, which allow them to store large amounts of energy through their rotation. As the flywheel rotates, it absorbs energy that it can later release. The rotational energy is thus stored in kinetic form and is available when needed.

[0022] The kinetic energy storage device is capable of converting kinetic energy into electrical energy and vice versa. This bidirectional conversion capability is advantageous for the flexible use of the stored energy. For example, if electrical energy is available, it can be used to accelerate the flywheel and thus store kinetic energy. Conversely, the kinetic energy of the rotating flywheel can be converted back into electrical energy by a generator when needed. This conversion capability ensures that energy is used efficiently and made available when required.

[0023] The kinetic energy storage device is electrically connected to other systems, in particular to a power supply device and a motor control device. These electrical connections are crucial for enabling energy exchange between the various components. For example, the motor control device can supply electrical energy to the kinetic energy storage device via a DC circuit to accelerate the flywheel. Simultaneously, the kinetic energy storage device can supply electrical energy to the DC circuit and thus to the motor control device to operate or assist it.

[0024] The kinetic energy storage device enables the exchange of electrical power with the motor control device. This means that the kinetic energy storage device can both absorb and release energy, depending on the system's requirements. For example, when there is a high demand for electrical energy, the kinetic energy storage device can convert the stored kinetic energy into electrical energy and release it to the motor control device. Conversely, it can absorb electrical energy when there is a surplus, convert it into kinetic energy, and store it. This continuous energy exchange helps ensure the stability of the entire energy system and maximizes efficiency.

[0025] 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 direct current for the DC circuit and, depending on the embodiment, may also feed electrical power into the supply network.

[0026] The power supply device draws electrical power from the supply network and makes it available to the devices connected to the intermediate circuit.

[0027] 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.

[0028] 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.

[0029] 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 compressed hydraulic fluid in the electrohydrostatic drive system. 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.

[0030] The electro-hydrostatic drive system with the computing unit described above offers a number of advantages.

[0031] The kinetic energy storage device allows for the kinetic storage of decompression power. This power can be released to the DC circuit (DC bus) when the process requires it, particularly when the fluid needs to be recompressed. The potential energy in the "fluid spring" thus oscillates back and forth between the drive and DC circuits and the kinetic energy storage device. This eliminates the need to draw (a large portion of) the compression energy from the power grid, and the decompression energy is reused instead of being converted into heat via braking resistors. This reduces the energy consumption of the electrohydrostatic system. Furthermore, high power peaks required for fluid compression are drawn from the storage device rather than from the power supply, which can therefore be correspondingly smaller.

[0032] Possible further developments of the electrohydrostatic drive system described above are explained in detail below.

[0033] A computing unit can be provided which is configured to receive at least one system parameter of the electro-hydraulic drive system and to automatically regulate, at runtime, a power flow from the motor control device to the kinetic energy storage device or from the kinetic energy storage device to the motor control device based on the at least one received system parameter. The electro-hydraulic drive system can have a multitude of system parameters that can be detected and received. The computing unit can be part of the electro-hydraulic 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 carry out an embodiment of the disclosed method.The computing unit can include a data processing device or a processor unit configured to perform an embodiment of the disclosed method. For this purpose, the processor unit 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. The processor unit can also include program code configured to perform the embodiment of the disclosed method when executed by the processor unit. The program code can be stored in a data memory of the processor unit. The processor unit can, for example, be based on at least one circuit board and / or on at least one SoC (System on Chip).

[0034] The system parameter may include a fluid-hydraulic pressure and / or a force provided by the electro-hydrostatic drive system. 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. Using the determined pressure as a system parameter, the amount of stored compression energy of a cylinder chamber can be determined. The stored compression energy E h can be calculated from the pressure p and a known bulk modulus K of the known fluid volume V enclosed under pressure. o accordingly The stored energy can be determined. 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. The table values ​​can be determined empirically through analysis or measurement. For set pressures, the compression energy can be measured by measuring the regenerated electrical energy during a pressure drop; for example, this can be done by integrating the rotational speed and torque values ​​available in the motor control device over time.

[0035] From the determined amount of stored compression energy, it can be determined that power is to be stored in the kinetic storage device.

[0036] The system parameter may include a force measured by the electro-hydrostatic drive system. A load cell can be installed directly between the actuator and the load. This can directly measure the force exerted on the actuator. The force provided by the electro-hydrostatic drive system can be determined using at least one pressure sensor and at least one load cell. A combination of these methods may also be used. 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. Furthermore, this can be achieved by regulating the electrical storage device to a target voltage and adjusting the power flow of the feed-in device.

[0037] The system parameter may include a voltage measured on a DC circuit. By measuring the voltage on the DC bus, the system can monitor and control the energy flow in real time. This is crucial for optimizing energy efficiency. Monitoring the DC bus voltage allows the system to dynamically respond to changes in energy demand and regulate the energy flow between the various components (such as the motor control device, the power supply device, and the kinetic energy storage device). Monitoring the DC bus voltage enables precise control of energy flows, contributing to the stabilization of the DC link. Voltage fluctuations can be detected and compensated for immediately by absorbing or releasing energy from the kinetic energy storage device.This prevents voltage spikes and drops that could damage the components. The system can use the voltage in the DC circuit to determine when to store or reuse regenerated energy from the hydraulic axes or other processes. A rise in DC bus voltage indicates excess energy, which is then stored in the kinetic energy storage device. Conversely, a voltage drop releases the stored energy to support the system. By utilizing the voltage detected in a DC circuit, the system minimizes its reliance on the power grid. Excess energy is stored locally within the system instead of being fed back into the grid. This reduces the load on the grid and improves the overall system efficiency.At the same time, feeding energy back into the grid is avoided, which is often associated with losses and additional costs. By monitoring the voltage in the DC circuit, the system can detect peak loads and react accordingly. During peak load times, the kinetic energy storage device can supply energy to meet demand, thus shaving off peak loads. This reduces the need for an oversized power supply and leads to cost savings in the sizing of power supply components. Continuous monitoring and control of the voltage in the DC circuit contributes to the system's reliability. By avoiding voltage fluctuations and efficiently utilizing regenerated energy, the service life of the system components is extended. Consistent voltage levels minimize wear and tear on electrical and mechanical parts.The system parameter may include the speed of the electric motor. Monitoring the electric motor's speed enables precise control of the motor's power output. This is particularly important for the motor-pump unit that drives the hydraulic cylinder. Accurate speed control leads to precise regulation of the hydraulic flow rate and, consequently, the movement of the hydraulic cylinder. This improves the accuracy and efficiency of the entire system. By monitoring the motor speed, the system can optimize energy consumption. At lower speeds, the motor's energy demand can be reduced, lowering the system's overall energy consumption. This is especially beneficial in applications where energy consumption must be minimized to reduce operating costs and maximize energy efficiency.Monitoring the motor speed allows the system to react to changes in energy demand in real time. When the motor runs slower, the system can draw correspondingly less energy from the DC bus. At higher speeds, the system can meet the energy demand from the kinetic energy storage device (KES) instead of drawing additional energy from the grid. This results in better utilization of the stored energy and reduces the load on the grid. During fluid decompression in the hydraulic cylinder, the kinetic energy generated by the fluid's return can be used to brake the motor. Monitoring the motor speed enables the system to efficiently feed this regenerated energy back into the DC bus or store it in the kinetic energy storage device. This reduces energy losses and increases the overall energy efficiency of the system.Monitoring the electric motor's rotational speed enables rapid adaptation to load changes and operating conditions. The system can quickly react to changes in speed and make appropriate adjustments to ensure the stability and performance of the electro-hydrostatic drive system. This is particularly important for applications requiring high dynamics and fast response times.

[0038] Monitoring the motor speed in combination with other system parameters, such as the voltage in the DC circuit, enables comprehensive monitoring and control of the electro-hydrostatic drive system. This holistic view of the system improves the ability to optimize energy flows, manage peak loads, and maximize efficiency.

[0039] It can be provided that fluid-hydraulic and mechanical energy stored in the electro-hydrostatic drive system is regenerated and stored as kinetic energy in the kinetic energy storage device when the fluid-hydraulic pressure and / or the supplied force decreases. When the fluid-hydraulic pressure and / or the supplied force increase, the stored kinetic energy is converted into electrical power and supplied to the motor control device to operate the motor-pump unit. The ability to regenerate fluid-hydraulic and mechanical energy during pressure reduction and store it in the kinetic energy storage device (KES) enables the efficient use of energy that would otherwise be unusable. This energy is not converted into heat or lost, but rather stored and reused as needed, leading to increased energy efficiency.By storing the regenerated energy in the kinetic energy storage device and subsequently converting it into electrical energy to power the motor-pump unit, the need for external energy input from the grid can be significantly reduced. This decreases the load on the grid and lowers operating costs, as less energy needs to be drawn from external sources. The stored kinetic energy can be used for peak shaving. During periods of high energy demand, the kinetic energy storage device can provide additional energy, thus reducing the need for an oversized power supply unit and a high grid load. This leads to optimized sizing of power supply components and cost savings.The system can react quickly to changes in energy demand by converting stored kinetic energy into electrical energy and delivering it to the motor control unit. This rapid responsiveness improves the dynamics of the drive system and ensures smooth and stable performance even under varying operating conditions. Regenerating and storing energy during pressure reduction and supplying this energy during pressure build-up allows for optimal control of energy flow within the system. This helps maximize the efficiency of the entire electro-hydrostatic drive system and reduce overall operating costs.

[0040] The electro-hydrostatic drive system may include at least one additional kinetic energy storage device connected in parallel. Connecting multiple kinetic energy storage devices in parallel increases the overall energy storage capacity. This means the system can store larger amounts of regenerated energy, which is then available when needed. Higher storage capacity allows the system to cover longer or more intense peak loads without drawing additional energy from the grid. Parallel connection provides redundancy, increasing the system's reliability. If one of the kinetic energy storage devices fails or requires maintenance, the others can continue to supply the necessary energy. This redundancy is important in critical applications where a continuous power supply must be guaranteed.By connecting multiple kinetic energy storage devices in parallel, the system's energy management can be made more flexible. The system can dynamically decide which storage device should absorb or release energy based on its current state of charge and the specific operational requirements. This optimizes the use of available energy storage and increases the system's efficiency. Distributing energy absorption and output across multiple storage devices minimizes peak loads on individual components. This reduces wear and tear on individual kinetic energy storage devices and extends their service life. Simultaneously, the overall stability of the system is improved because peak loads can be handled more efficiently.In applications with varying load profiles, the system can respond more effectively to different energy demands by utilizing multiple kinetic energy storage devices. At low loads, some storage devices can be placed in standby mode while others remain active. At high loads, all storage devices can be used simultaneously to provide the necessary energy. This results in optimized energy utilization and reduced energy consumption. Furthermore, the ability to connect multiple kinetic energy storage devices in parallel facilitates integration into existing electro-hydrostatic drive systems. This allows for a gradual expansion of energy storage capacity without requiring fundamental changes to the overall system. Existing systems can thus be adapted to anticipated energy demands with minimal effort.Expanding energy storage capacity modularly using parallel kinetic storage devices can be more cost-effective than using a single large storage unit. Smaller, modular storage units are often less expensive to purchase and maintain, while offering the flexibility to increase capacity as needed.

[0041] The kinetic energy storage device can be connected to the motor control device and the power supply device via a DC-DC converter. The converter enables efficient conversion of the kinetic energy stored in the kinetic energy storage device into electrical energy and vice versa. This efficient conversion ensures minimal energy losses and optimal utilization of the stored energy, thus increasing the overall system efficiency. The DC-DC connection allows the kinetic energy storage device to maintain a stable voltage supply. The converter can quickly respond to voltage changes on the DC bus and provide the stored energy to compensate for voltage fluctuations. This contributes to the overall system stability and protects the connected components from voltage spikes and drops.The energy storage inverter enables flexible energy supply and storage. It can dynamically decide when to draw energy from or feed it into the kinetic energy storage device. This flexibility is particularly important for applications with fluctuating energy demands, as it allows for optimal utilization of available energy sources. An energy storage inverter optimizes the system's energy management. The inverter can continuously collect data on energy demand and the state of charge of the kinetic energy storage device and control the energy flow within the system based on this information. This leads to improved efficiency and reduces the need for external energy input from the grid. By efficiently utilizing the kinetic energy storage device, the energy demand from the grid can be reduced.The energy storage inverter ensures that the stored energy is used effectively to smooth peak loads and minimize grid strain. This leads to cost savings in energy supply and reduces the need for expensive grid upgrades. The inverter allows for the easy integration of multiple kinetic energy storage devices into the system. These can be connected in parallel to increase the overall energy storage capacity and improve redundancy. The inverter can coordinate the energy flow between the different storage devices to ensure optimal performance. The inverter can quickly respond to changes in energy demand and the state of charge of the kinetic energy storage device. This improves the system's dynamics and responsiveness, as it is able to provide or store energy immediately when needed.This rapid responsiveness is crucial for applications with high dynamic requirements.

[0042] The kinetic energy storage device may include an electric machine. Electric machines are designed to efficiently convert kinetic energy into electrical energy and vice versa. This allows for effective use of the stored energy. When the kinetic energy storage device needs to release energy, the electric machine converts the kinetic energy into electrical energy, which can then be used to power the system. Electric machines offer high power density, meaning they are capable of storing and converting large amounts of energy in a compact form. This is particularly advantageous in applications where space and weight are limited. Electric machines can respond very quickly to control commands, resulting in fast charging and discharging cycles.This improves the system's dynamics and responsiveness, which is advantageous in industrial applications with fluctuating load requirements. Electric machines are versatile and can be integrated into a wide variety of applications. They can function as both motors and generators, depending on the system's needs. This flexibility allows for a broad range of applications in various industrial processes. Electric machines have a longer lifespan than batteries and double-layer capacitors. They generally require less maintenance compared to mechanical or hydraulic components and offer high operational reliability. The electric machine can be designed as a permanent magnet synchronous motor (PMSM). Permanent magnet synchronous motors exhibit high efficiency and power density.They offer precise speed and position control and are therefore advantageous for applications requiring accurate control. PMSMs are also capable of functioning as generators, making them highly versatile.

[0043] The electric machine can be designed as an asynchronous motor. Asynchronous motors are robust and cost-effective. They are widely used in industrial applications due to their simple design and reliability. Asynchronous motors can also be used as generators, making them a good choice for kinetic energy storage devices.

[0044] The electric machine can be designed as a synchronous reluctance motor. Synchronous reluctance motors offer good efficiency and high power density. They feature a simple design and the ability to generate high torques at low speeds. These characteristics make them suitable for applications requiring high efficiency and reliability.

[0045] The electric machine can be designed as a switched reluctance motor. Switched reluctance motors are simple in design and robust. They offer high reliability and efficiency, especially in applications requiring variable speeds and high torques. These motors can also be used as generators, making them versatile.

[0046] The electric machine can be designed as a direct current (DC) motor. DC motors offer simple control and high torque at low speeds. They are advantageous in applications requiring precise control of speed and torque. DC motors can also function as generators, making them suitable for kinetic energy storage devices. The electric machine can be designed with a rotating shaft to which a rotating mass is coupled. By coupling a rotating mass to the shaft of the electric machine, kinetic energy can be stored efficiently. The rotating mass (such as a flywheel) stores energy in the form of rotational energy, which can be retrieved when needed. This results in a high energy density.A rotating mass on a rotating shaft can store a significant amount of energy in a relatively small volume. This results in a high power density, which is particularly advantageous in applications where space and weight are limited. The compact design allows for efficient use of available space. The rotating mass acts as an energy storage device, contributing to the stabilization of system performance. In the event of sudden load changes or fluctuations in energy demand, the stored kinetic energy can be quickly released to stabilize the power output. This prevents voltage fluctuations and improves the stability of the entire drive system. The presence of a rotating mass enables a rapid response to changes in energy demand. The electric machine can quickly convert the kinetic energy of the rotating mass into electrical energy and vice versa.This results in improved system dynamics and rapid responsiveness, which is particularly important in industrial applications with fluctuating load requirements. The direct coupling of the rotating mass to the shaft of the electric machine minimizes energy losses that could occur during energy conversion. Kinetic energy can be stored and released with virtually no loss, increasing the overall system efficiency. This is especially advantageous in applications where energy losses must be minimized. Utilizing a rotating mass for energy storage can improve the system's lifespan and reliability. The rotating mass can store and release energy without placing excessive stress on wear parts. This reduces mechanical stress and extends the service life of the system components.When the electric motor decelerates, the kinetic energy of the rotating mass can be regenerated and fed back into the DC bus. This allows for the reuse of energy that would otherwise be lost. This regeneration contributes to energy savings and increased system efficiency. A rotating mass in the form of a flywheel can be incorporated. A flywheel offers several advantages in the electro-hydrostatic drive system. A flywheel stores kinetic energy very efficiently by storing it as rotational energy, which can be quickly released when needed. This helps stabilize sudden load changes and voltage fluctuations in the system by providing readily available energy.Furthermore, the use of a flywheel improves system dynamics and responsiveness while simultaneously reducing mechanical stress and wear, thus extending the system's service life. For the purposes of this disclosure, a flywheel consists of a heavy, circular metal body attached to the rotating shaft of the electric machine. It can be made of materials such as steel or cast iron to ensure high mass and inertia. The flywheel can be designed as a single component or as a composite component with multiple layers or segments. Additionally, it can be equipped with fins or vents to improve heat dissipation and prevent overheating. Depending on the application requirements, the flywheel can be designed in various sizes and weights to achieve the required energy storage capacity and moments of inertia.

[0047] A kinetic energy storage device, specifically a flywheel energy storage system, consists of a drive motor with a mechanically connected flywheel. The flywheel's drive motor can operate as a motor to store energy and as a generator to extract energy. 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

[0048] F E kin — - 2 J Ikin < w i 2 ■

[0049] It can be provided that the rotating mass is coupled to the rotating shaft of the electric machine outside the machine's housing, and that the rotating mass is enclosed in a housing, in particular a grid-like housing. A technical advantage of this design is that the rotating mass is located outside the electric machine's housing, thereby improving heat dissipation. This arrangement allows for more efficient cooling of the rotating mass and prevents overheating, which could impair the performance and service life of the flywheel. The grid-like housing around the rotating mass provides additional protection without impeding heat dissipation, while also enabling safe handling and maintenance.The external placement of the flywheel also allows for flexible adjustment of the flywheel's size and weight without affecting the dimensions of the electric machine.

[0050] Additionally, this configuration offers easier access for inspections and maintenance of the rotating mass. External mounting simplifies the installation and replacement of the flywheel, thus increasing ease of maintenance. This arrangement also helps to reduce vibrations and mechanical stresses on the electric motor, as the rotating mass can be mounted and stabilized separately. This results in smoother and more stable operation of the entire drive unit. Finally, the flexible design of the housing helps to keep out dirt and foreign objects, further enhancing operational reliability.

[0051] The rotating shaft can be designed with a smaller diameter than the rotating mass. This design offers the advantage of improved heat dissipation and cooling of the rotating mass, preventing overheating and extending the flywheel's service life. External placement of the rotating mass allows for greater flexibility in adjusting its size and weight without affecting the dimensions of the electric motor. The lattice-like housing provides protection from external influences and facilitates maintenance while ensuring efficient heat dissipation. This arrangement reduces mechanical stress and vibration on the electric motor, resulting in smoother and more stable operation.The kinetic energy storage device can be further configured to convert the kinetic energy of the motor-pump unit into electrical power via the motor control device. A technical advantage of this design is that the kinetic energy storage device can convert and store excess kinetic energy from the motor-pump unit into electrical power. This increases the overall efficiency of the system, as the renewable energy that would otherwise be lost is used effectively. By storing this energy, it can be reused when needed, reducing energy consumption from external sources. This contributes to lower operating costs and improved system sustainability. Furthermore, it reduces the load on the grid by balancing peak loads and stabilizing energy fluctuations.

[0052] The electro-hydrostatic drive system may include at least one additional hydraulic cylinder. A technical advantage of having at least one additional, parallel-connected hydraulic cylinder is the increased flexibility and performance of the system. By connecting multiple hydraulic cylinders in parallel, the system can generate greater forces and distribute them evenly across multiple loads, thus improving the efficiency and effectiveness of power transmission. This enables the system to execute complex motion sequences and handle different load requirements simultaneously. Furthermore, the redundant arrangement of the cylinders allows the system to remain functional even if a single cylinder fails, increasing operational safety and reliability.Finally, the even distribution of the load across multiple cylinders will reduce the wear of individual components and thus extend the service life of the entire drive system.

[0053] The electro-hydrostatic drive system may include at least one additional motor-pump unit. A technical advantage of this is the increased redundancy and flexibility of the system. Integrating multiple motor-pump units allows the system to continue operating even if one unit fails, thus increasing the reliability and availability of the drive. This enables load distribution, where the work is evenly distributed across multiple units, thereby increasing efficiency and reducing wear on individual components. Furthermore, the motor-pump units can be switched on or off as needed to optimize energy consumption and adapt operation to current requirements.This configuration also allows for easy scalability of the system by adding additional motor pump units to meet higher performance requirements.

[0054] The electro-hydrostatic drive system may include at least one electrical storage device with a storage capacity, configured to exchange electrical power with the motor control device and the power supply device, and to store electrical energy. A technical advantage of the electro-hydrostatic drive system having at least one electrical storage device with a storage capacity lies in the improved energy efficiency and flexibility of the system. The electrical storage device can store excess electrical energy and release it back to the motor control device as needed, thus ensuring a stable and continuous power supply. This reduces dependence on external energy sources and minimizes energy losses, as regenerated energy is used effectively.Furthermore, the electrical storage device can absorb peak loads and distribute energy consumption more evenly, which reduces operating costs and extends the service life of the system components. Finally, storing electrical energy contributes to stabilizing the DC circuit, which increases the efficiency and reliability of the entire drive system.

[0055] The electrical storage device (180) may include at least one of the following storage devices, comprising a capacitor, an accumulator, and / or a combination thereof. For the purposes of this disclosure, an electrical storage device is understood to be a component with an electrical connection to a DC voltage that absorbs electrical energy and stores it for later use. The electrical storage device may be capable of storing electrical energy in an electrical, chemical, or kinetic form and releasing it again when required. The electrical storage device includes a storage capacity that specifies the maximum amount of electrical energy that can be stored. The inclusion of an electrical storage device can generate the advantage that it responds immediately to rapid power peaks, especially if it is designed as a passive intermediate circuit storage device.The (active) kinetic energy storage device reacts with a slight delay and can be configured to respond only to power peaks with high energy content. This can be incorporated into an optimal control strategy where different storage types can each leverage their strengths.

[0056] 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.

[0057] The storage device may include at least one electrical capacitor. Capacitors can absorb and release high electrical power. Furthermore, capacitors have a long lifespan.

[0058] 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

[0059] Eel Cel U 2 .

[0060] The motor control device may also be designed to exchange electrical power with the power supply device and the kinetic energy storage device. This allows for the optimization of the system's energy management. This flexibility makes it possible to dynamically control and adjust energy flows to ensure efficient energy consumption.

[0061] Excess energy can be stored in the kinetic storage device and released again when needed, resulting in an overall improvement in energy efficiency.

[0062] The motor control device contributes to stabilizing the DC bus by drawing energy from or storing it in the kinetic energy storage device to compensate for voltage fluctuations. This ensures that the DC bus maintains a constant voltage, improving the performance and reliability of the entire drive system. By enabling energy exchange between the power supply and the kinetic energy storage device, the system can reduce its reliance on the grid. During periods of low load, excess energy can be stored in the kinetic energy storage device and released during peak load times. This reduces the load on the grid and can lead to lower energy costs. The system can also efficiently store regenerated energy, such as that generated during hydraulic axle decompression, in the kinetic energy storage device.This stored energy can later be used to support the motor control device, further increasing the overall energy efficiency of the system. This regeneration and reuse of energy also contributes to sustainability by reducing energy consumption and the system's environmental footprint. The ability to quickly exchange energy between the kinetic storage device and the motor control device improves the system's dynamics and responsiveness. This is particularly important in applications with rapidly changing load requirements, as the system can quickly respond to changes in energy demand without relying on external energy sources. By using the kinetic storage device as an additional energy source, the system can continue operating even in the event of failures or malfunctions in the power supply device.This redundancy increases the reliability and fault tolerance of the electro-hydrostatic drive system, as it is less susceptible to external power supply problems. The motor control device can distribute energy between the power supply device and the kinetic energy storage device to smooth out load peaks. This results in a more even distribution of the load across the system and prevents overloads that could lead to failures or inefficient operation.

[0063] It can be envisioned that electrical power is regenerated and stored as kinetic energy in the kinetic storage device without feeding energy back into the power grid or dissipating it via another electrical consumer. By directly storing regenerated electrical power as kinetic energy in the kinetic storage device, the system's efficiency is maximized. Energy losses that could occur when feeding energy back into the grid or dissipating it to other consumers are avoided. This leads to optimal use of the regenerated energy and increases the overall efficiency of the system. The system becomes more independent of the power grid, as it does not rely on feeding regenerated energy back into the grid. This is particularly advantageous in situations where the grid is unstable or peak loads need to be avoided.The stored kinetic energy can be used as needed, thus reducing dependence on external energy sources. Storing the regenerated energy directly in the kinetic storage device contributes to the stabilization of the DC circuit (DC bus).

[0064] Voltage fluctuations in the DC bus are minimized because the kinetic energy storage device acts as a buffer, absorbing or releasing excess energy to maintain a constant voltage. Directly storing regenerated energy in the kinetic energy storage device prevents losses that could occur during conversion and feeding it back into the grid. This leads to more efficient energy use and reduces the overall operating costs of the system. Energy losses due to transmission losses or inefficient conversion processes are thus avoided. The ability to store regenerated energy directly, rather than feeding it back into the grid, increases the system's reliability and fault tolerance. In the event of grid disturbances or outages, the system can still draw on the stored kinetic energy to maintain operation.This is particularly important for applications requiring high availability and continuous operational readiness. The stored kinetic energy can be used to smooth peak loads and optimize load management. During periods of high demand, the kinetic storage device can provide energy to cover peak loads, thereby reducing the strain on the grid and lowering operating costs. Directly storing the regenerated energy in the kinetic storage device simplifies the system architecture. No additional components or circuits are required to feed energy back into the grid or supply it to other consumers. This reduces the system's complexity and maintenance requirements. The advantage of an active storage device (e.g., kinetic energy storage, DC+DC converter + capacitors) lies in the stabilization of the intermediate circuit voltage.In the case of passively operating capacitors in the intermediate circuit (state of the art), the voltage fluctuates significantly. A sharp drop in the DC voltage forces the motors of the drive axles (EHA or EMA) to operate in the field-weakened region, which generates higher losses due to the additional current.

[0065] The above can be summarized in other words and in a possible more concrete elaboration of the revelation as described below, whereby the following description is to be interpreted as not being restrictive for the revelation.

[0066] A drive-controlled asynchronous motor is provided, which is coupled to the DC bus of an EAS drive machine. The motor stores energy, especially decompression energy, kinetically in the rotating mass. The power can be delivered to the DC bus when the process requires it, particularly when the fluid needs to be recompressed.

[0067] The EAS drive unit is an electro-hydrostatic drive system. It uses 4-quadrant EPUs (electro-hydrostatic pump units) driven by servo drives, usually with a coupled intermediate circuit.

[0068] EAS-based machines are new. The use of a four-quadrant operating pump enables the recovery of braking and decompression energy from the axes / processes. The state of the art involves dissipating this regenerative energy via leakage resistors, or some machines use active front-end power supplies to feed this energy back into the factory. According to the disclosure, the energy is stored kinetically in the KES (kinetic energy storage system). Capacitors can be provided in the DC link to store this regenerative energy. However, above a certain energy level (in the range >35 kJ), kinetic storage is significantly more cost-effective. KES are used similarly in servo presses.Storing regeneration energy through the combination of an EAS-based machine and the storage of the oil's potential energy (which acts like a spring), as well as releasing this stored energy to assist in fluid compression, is advantageous. The exchange between the fluid's potential energy and the kinetic energy of the rotating mass of the KES (Kinetic Energy System) is essential.

[0069] The motor can be an asynchronous motor (ASM). However, any electric motor can also be used. It can be used on any machine with a DC bus, even without EAS (i.e., purely electromechanical). It can also be used on simulation platforms with high energy demands. Peak shaving approaches (power feed-in + storage) for EAS-based machines are very attractive due to their significantly higher efficiency compared to throttle-based hydraulic solutions. The storage system also allows for a considerable reduction in the high installed power of the EAS axes. The energy management component for EAS acts as an enabler for the future technology of EAS / EPUs. It is advantageous that the installed power of EAS-based machines is lower than, or at least equal to, the installed power of the hydraulic (throttle-based) machine.This is especially true if the hydraulic machine uses a constant pressure system with hydraulic accumulators, which can also buffer (positive) power peaks and thus reduce the nominal power of the supplying central pump.

[0070] The potential energy in the "fluid spring" oscillates via the EPU and DC link to the kinetic energy storage device and back. This means that (a large portion of) the compression energy does not need to be drawn from the grid, and the decompression energy is reused instead of being converted into heat. The advantages of significantly lower power input (peak shaving) and loss minimization (storage rather than dissipation) can be utilized. The system can also consist of multiple cylinders and / or multiple EPUs. The DC link can therefore also consist of multiple AC-DC converters. One or more kinetic energy storage devices (KES) can be coupled in parallel to the DC link. The KES can also absorb kinetic energy from the EPU mass when it is braking and release it when the EPUs are accelerating. Passive capacitors can also be added to the DC link to buffer very high-frequency power peaks.

[0071] Furthermore, a method for controlling a kinetic energy storage device of an electrohydrostatic drive system is provided. The method can comprise several process steps. In a first process step, at least one system parameter of the electrohydrostatic drive system is received. In a further step, a power flow from the motor control device to a kinetic energy storage device or from the kinetic energy storage device to the motor control device is controlled based on the received system parameter.

[0072] Furthermore, a computing unit for controlling a kinetic energy 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 control the power flow from the motor control device to a kinetic energy storage device or from the kinetic energy storage device to the motor control device based on the received system parameter.

[0073] Furthermore, a computer program is provided, comprising instructions that, when executed by a computer, cause it to at least partially execute the above-described procedure. The program code of the computer program can be in any form, in particular in a form suitable for the processing unit of electrohydrostatic drive systems. The above descriptions relating to the electrohydrostatic drive system and the procedure apply analogously to the computer program and vice versa.

[0074] Furthermore, a hydraulic axle, in particular a hydraulic press, is provided. The hydraulic axle has the electro-hydrostatic drive system according to the disclosure.

[0075] 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.

[0076] 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.

[0077] Detailed description

[0078] 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:

[0079] Fig. 1 shows an embodiment of an electrohydrostatic drive system according to the disclosure;

[0080] Fig. 2 shows a further embodiment of the electrohydrostatic drive system according to the disclosure;

[0081] Fig. 3 shows a flowchart of an embodiment of the disclosed

[0082] Procedure; and

[0083] Fig. 4 shows an embodiment of the control of the kinetic

[0084] Storage device.

[0085] 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.

[0086] Figure 1 shows an embodiment of an electro-hydrostatic drive system 100 according to the disclosure. The electro-hydrostatic drive system (100) is designed for operating a hydraulic axle. The hydraulic axle can be configured as a hydraulic cylinder 110. The electro-hydrostatic drive system 100 can be used in applications such as hydraulic presses. The electro-hydrostatic drive system 100 can incorporate a plurality of hydraulic cylinders 100 of different designs. The electro-hydrostatic drive system 100 shown in Figure 1 comprises various subsystems, including a motor-pump unit 120, a motor control device 130, a kinetic energy storage device 140, and a computing unit 150, to ensure efficient control and operation.

[0087] The core component that facilitates the movement of the hydraulic axis is the hydraulic cylinder 110. This hydraulic cylinder 110 is crucial for converting hydraulic energy into mechanical energy to perform tasks such as pressing or lifting.

[0088] The motor-pump unit 120, which directly drives the hydraulic cylinder 110, comprises an electric motor 121 and a pump 122. The electric motor 121 drives the pump 122, which in turn generates a hydraulic flow rate essential for the operation of the hydraulic cylinder 110. In this configuration, the energy conversion process takes place, in which electrical energy is first converted into hydraulic energy.

[0089] The function of the electric motor 121 is controlled by a motor control device 130. The motor control device 130 is designed to regulate the power supply to the electric motor 121 and thus control its operating parameters such as speed and torque based on the requirements of the hydraulic cylinder 110.

[0090] The power supply device 170 acts as an intermediary between the motor control device 130 and an external power supply network 160. It ensures that the motor control device 130 receives power to protect the electro-hydrostatic drive system 100 from fluctuations in the power supply that could impair the performance of the electric motor 121. The electro-hydrostatic drive system 100 includes the kinetic energy storage device 140, which is connected to both the motor control device 130 and the power supply device 170. The kinetic energy storage device 140 comprises an electric machine 141 containing a rotating shaft 142 with a rotating mass 143. This arrangement can store kinetic energy and is used to store excess energy and redistribute it as needed.The kinetic storage device 14 can absorb energy during low-demand operation and release it during peak loads, thereby increasing the overall energy efficiency of the system.

[0091] The computing unit 150 is designed for the dynamic management of the electro-hydrostatic drive system 100. It is configured to receive system parameters such as hydraulic pressure, force exerted by the hydraulic cylinder 110, voltage levels in the DC circuit 190, and rotational speed of the electric motor 121. Based on these inputs, the computing unit 150 adjusts the energy distribution in the system by controlling the energy flow from the motor control device 130 to the kinetic energy storage device 140 and vice versa. This real-time management ensures optimal performance and energy utilization, adapted to varying operating requirements.

[0092] The DC circuit 190 serves as a channel for the transmission of electrical energy within the electro-hydrostatic drive system 100, in particular between the kinetic energy storage device 140, the motor control device 130, and the power supply device 170. The inclusion of an energy converter 200 in this configuration enables the conversion of stored kinetic energy back into electrical energy, which can then be used by the motor control device 130 to control the motor pump unit 120.

[0093] Together, these components form the electro-hydrostatic drive system 100, which enables kinetic energy storage, real-time control, and efficient hydraulic motion. The electro-hydrostatic drive system 100 is designed to maximize energy efficiency while maintaining high operational reliability and flexibility, particularly in industrial environments where hydraulic machinery plays a crucial role.

[0094] After a pressing operation is carried out by the hydraulic cylinder 110, the working fluid (hydraulic fluid) is compressed and pressurized in the corresponding chamber of the hydraulic cylinder 110 and the connected fluid lines. During decompression, initiated by the motor pump unit 120, the potential energy of the fluid flows through the motor control device 130 into the DC link. The processing unit 150 accelerates the kinetic energy storage device 140, in particular the electric motor 141, to kinetically store the energy flowing through the common DC link 190. In a subsequent pressing phase, when the fluid needs to be compressed again, the kinetic energy from the kinetic energy storage device 140 can be reused by decelerating the rotating mass of the kinetic energy storage device 140.The required peak power for compression therefore does not come (exclusively) from the power supply network 160, but also from the energy storage inverter 200 and the kinetic energy storage device 140. Furthermore, the decompression energy does not need to be dissipated hydraulically via a valve or electrically via a leakage resistor in the DC intermediate circuit 190. Additionally, peak shaving for EAS-based presses is achieved through kinetic energy storage.

[0095] Figure 2 shows a further embodiment of the electrohydrostatic drive system 100 according to the disclosure for moving a hydraulic axle. The electrohydrostatic drive system 100 of Figure 2 has the components of the embodiment of Figure 1.

[0096] Additionally, the electrical storage device 180 is provided, which enhances the energy management capabilities of the electro-hydrostatic drive system 100. The electrical storage device 180 is designed to interact with the motor control device 130 and the power supply device 170, to store electrical energy and provide additional power flexibility. It can store energy in various forms, including capacitors and accumulators, provides a buffer against energy fluctuations, and supports the continuous operation of the electro-hydrostatic drive system 100.

[0097] The electro-hydrostatic drive system 100 can have a plurality of hydraulic cylinders 110-x. For this purpose, the hydraulic cylinders 110 are connected in parallel. Furthermore, the electro-hydrostatic drive system 100 can have at least one additional motor-pump unit 120-x, which is connected to the DC intermediate circuit 190 and is connected in parallel to the existing motor-pump unit 120.

[0098] Figure 3 shows a flowchart of an embodiment of the disclosed method. The method 300 for charging a kinetic energy storage device 140 of an electro-hydrostatic drive system 100, as illustrated in Figure 3, comprises two process steps. In a first step 310, at least one system parameter of the electro-hydrostatic drive system 100 is received. In a further step 320, a power flow from the motor control device 130 to a kinetic energy storage device 140 or from the kinetic energy storage device 140 to the motor control device 130 is controlled based on the received system parameter.

[0099] Figure 4 shows an embodiment of the control system for the kinetic energy storage device 140. The working fluid in the hydraulic cylinder 110, which is under pressure in the chamber (or chambers), is decompressed by releasing a volume flow. The stored potential energy of the fluid is electrically transferred to the kinetic energy storage device 140 via the motor pump unit(s) 120, motor control device 130, and DC intermediate circuit 190, and stored there as kinetic energy by increasing the rotational speed. If, in the next process step, a force is to be generated again via the hydraulic cylinder 110, the stored kinetic energy is converted back into the potential energy of the compressed fluid by braking the kinetic energy storage device 140 and building up pressure in the cylinder chamber (or chambers) via the EPU axes. (Reference numeral list)

[0100] 100 electro-hydrostatic drive system

[0101] 110 hydraulic cylinders

[0102] 110 hydraulic cylinders with working fluid

[0103] 120 Motor pump unit

[0104] 120 fluid hydraulic motor pump unit

[0105] 121 electric motor

[0106] 122 Pump

[0107] 130 Engine control unit

[0108] 140 kinetic storage device

[0109] 141 electric machine

[0110] 142 rotating shaft

[0111] 143 rotating mass

[0112] 150 computing units

[0113] 151 Interface

[0114] 152 processor units

[0115] 153 storage units

[0116] 160 supply network

[0117] 170 Feed device

[0118] 180 electrical storage device

[0119] 190 DC intermediate circuit

[0120] 190 DC circuit

[0121] 200 storage inverters

[0122] 300 procedures

[0123] 310 333 procedural steps

Claims

Patent claims 1. Electro-hydrostatic drive system (100) for moving a hydraulic axis, wherein the electro-hydrostatic drive system (100) comprises: a hydraulic cylinder (110) for moving the hydraulic axis, in particular a hydraulic press; a motor-pump unit (120) with an electric motor (121) and a pump (122) for providing a hydraulic flow for moving the hydraulic cylinder (110); - a motor control device (130) designed to exchange electrical power with the electric motor (121); a power supply device (170) arranged between a power supply network (160) and the motor control device (130); and - a kinetic storage device (140) which is electrically connected to the power supply device (170) and the motor control device (130), wherein the kinetic storage device (140) is designed to exchange electrical power with the motor control device (130) and the power supply device (170) and to store kinetic energy.

2. Electro-hydrostatic drive system according to the immediately preceding claim, wherein fluid-hydraulic and mechanical energy stored in the electro-hydrostatic drive system (100) is regenerated in the kinetic storage device (140) when the fluid-hydraulic pressure and / or the force supplied is reduced and stored as kinetic energy, and when the fluid-hydraulic pressure and / or the force is supplied, the stored kinetic power is converted into electrical power and supplied to the motor control device (130) for operating the motor pump unit (120).

3. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the electro-hydrostatic drive system (100) further comprises a computing unit (150), wherein the computing unit (150) is configured to receive at least one system parameter of the electro-hydrostatic drive system (150) and to automatically control a power flow from the motor control device (130) to the kinetic storage device or from the kinetic storage device to the motor control device (130) at runtime based on the at least one received system parameter.

4. Electro-hydrostatic drive system (100) according to the immediately preceding claim, wherein the system parameter comprises a voltage detected on a DC circuit (190).

5. Electro-hydrostatic drive system (100) according to one of the preceding claims 3 and 4, wherein the system parameter includes a rotational speed of the electric motor (121).

6. Electro-hydrostatic drive system (100) according to any one of the preceding claims 3 to 5, wherein the system parameter comprises a fluid hydraulic pressure and / or a force provided by the electro-hydrostatic drive system (100).

7. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the electro-hydrostatic drive system (100) comprises at least one further kinetic storage device (140-x) connected in parallel.

8. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the kinetic storage device (140) is connected to a storage converter (200) via a DC circuit (190) to the motor control device (130) and the power supply device (170).

9. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the kinetic storage device (140) comprises an electric machine (141).

10. Electro-hydrostatic drive system (100) according to the immediately preceding claim, wherein the electric machine (141) has a rotating shaft (142) and a rotating mass (143) is coupled to the rotating shaft (142).

11. Electro-hydrostatic drive system (100) according to one of the preceding claims 9 and 10, wherein the electric machine (141) is designed as a permanent magnet synchronous motor, asynchronous motor, synchronous reluctance motor or switched reluctance motor.

12. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the kinetic storage device (140) is further configured to store kinetic energy of the motor pump unit (120) converted into electrical power via the motor control device (130).

13. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the electro-hydrostatic drive system (100) comprises at least one further hydraulic cylinder (110-x).

14. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the electro-hydrostatic drive system (100) comprises at least one further motor pump unit (120-x).

15. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the electro-hydrostatic drive system (100) has at least one electrical storage device (180) with a storage capacity, and wherein the electrical storage device (180) is configured to exchange electrical power with the motor control device (130) and the power supply device (170) and to store electrical energy.

16. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the electrical storage device (180) comprises at least one of the following storage devices comprising a capacitor, an accumulator and / or a combination thereof.

17. Electro-hydrostatic drive system (100) according to one of the preceding claims, wherein the motor control device (130) is further configured to exchange electrical power with the power supply device (170) and the kinetic storage device (140).

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

19. Method (300) for controlling a kinetic storage device (140) of an electrohydrostatic drive system (100) according to at least one of the preceding claims, with a motor control device (130) comprising the following method steps: Receive (310) at least one system parameter of the electrohydrostatic drive system (100); and Rules (320) of a power flow from the motor control device (130) into a kinetic storage device or from the kinetic storage device into the motor control device (130) based on the received system para meter.

20. Hydraulic axle, in particular a hydraulic press, with an electro-hydrostatic drive system (100) according to any one of claims 1 to 18.

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