Apparatus and method for determining a target rotational speed for a rotary drive driving a displacement pump of a hydraulic system of a lifting equipment

Abstract

Provided is an apparatus (100) for determining a target rotational speed for a rotary drive (130) driving a displacement pump (125) of a hydraulic system of a lifting equipment (120). The apparatus (100) includes processing circuitry (110) configured to receive input data (101) indicating at least one pressure measurement in the hydraulic system. The processing circuitry (110) is further configured to determine the target rotational speed for the rotary drive (130) based on a first value and a second value. The first value represents a pressure difference between a load pressure in the hydraulic system and a pump pressure of the displacement pump. The first value is based on the input data (101). The second value is a target value for the pressure difference. In addition, the processing circuitry (110) is configured to output control data (105) indicating the determined target rotational speed.

Description

Field

[0001] The present disclosure relates to controlling rotary drives driving displacement pumps of lifting equipment. In particular, examples of the present disclosure relate to an apparatus and a method for determining a target rotational speed for a rotary drive driving a displacement pump of a hydraulic system of a lifting equipment, a system comprising the apparatus and a vehicle comprising the apparatus.Background

[0002] Cranes, in particular loader cranes play a pivotal role in various industries, providing efficient lifting and handling capabilities. Various functions of a crane such as lifting, lowering, extending, retracting, rotating, and stabilizing use hydraulic power provided by a displacement pump of the crane. The displacement pump pumps hydraulic oil to provide the required hydraulic power.

[0003] Fixed displacement pumps or variable displacement pumps are used at constant or specific speed levels in most applications. The use at constant speed gives the variable displacement pump an efficiency advantage over the fixed displacement pump. Variable displacement pumps are generally more expensive than fixed displacement pumps, have higher noise emissions but are also more efficient if the volume flow requirement is nearly the same as the volume flow production. Operating a fixed displacement pump at variable speed is difficult or only possible to a limited extent with an internal combustion engine. The same problem arises with other types of lifting equipment equipped with a hydraulic system, such as forklifts or lifting platforms.

[0004] Hence, there may be a demand for improved control of the hydraulic system of lifting equipment.Summary

[0005] This demand is met by an apparatus and a method for determining a target rotational speed for a rotary drive driving a displacement pump of a hydraulic system of a lifting equipment, a system, a vehicle, a non-transitory machine-readable medium and a program in accordance with the independent claims. Advantageous embodiments are defined by the dependent claims.

[0006] According to a first aspect, the present disclosure provides an apparatus for determining a target rotational speed for a rotary drive driving a displacement pump of a hydraulic system of a lifting equipment. The apparatus comprises processing circuitry configured to receive input data indicating at least one pressure measurement in the hydraulic system. The processing circuitry is further configured to determine the target rotational speed for the rotary drive based on a first value and a second value. The first value represents a pressure difference between a load pressure in the hydraulic system and a pump pressure of the displacement pump. The first value is based on the input data. The second value is a target value for the pressure difference. In addition, the processing circuitry is configured to output control data indicating the determined target rotational speed.

[0007] According to a second aspect, the present disclosure provides a system comprising a lifting equipment and a rotary drive configured to drive a displacement pump of a hydraulic system of the lifting equipment. The system comprises the apparatus according to the first aspect for determining a target rotational speed for the rotary drive. The system further comprises control circuitry configured to control the rotary drive based on the control data. The lifting equipment comprises at least one hydraulic actuator coupled to the displacement pump and drivable by the hydraulic fluid.

[0008] According to a third aspect, the present disclosure provides a vehicle having mounted thereon or being a lifting equipment. The vehicle comprises the apparatus according to the first aspect. The hydraulic system comprises at least one hydraulic actuator coupled to the displacement pump and drivable by the hydraulic fluid. Control circuitry on the vehicle is configured to control the rotary drive based on the control data. The rotary drive is part of or is mounted to the vehicle. Alternatively, the rotary drive is external to the vehicle and the vehicle is configured to mechanically couple the displacement pump to the external rotary drive. In this case, the vehicle is configured to output the control data to control circuitry for controlling the rotary drive external to the vehicle.

[0009] According to a fourth aspect, the present disclosure provides a method for determining a target rotational speed for a rotary drive driving a displacement pump of a hydraulic system of a lifting equipment. The method comprises receiving input data indicating at least one pressure measurement in the hydraulic system. Further, the method comprises determining the target rotational speed for the rotary drive based on a first value and a second value. The first value represents a pressure difference between a load pressure in the hydraulic system and a pump pressure of the displacement pump. The first value is based on the input data. The second value is a target value for the pressure difference. In addition, the method comprises outputting control data indicating the determined target rotational speed.

[0010] According to a fifth aspect, the present disclosure provides a non-transitory machine-readable medium having stored thereon a program having a program code for performing the method according to the fourth aspect, when the program is executed on a processor or a programmable hardware.

[0011] According to a sixth aspect, the present disclosure provides a program having a program code for performing the method according to the fourth aspect, when the program is executed on a processor or a programmable hardware.

[0012] By adjusting the rotational speed based on the first value representing the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump, it is ensured that the displacement pump operates at an optimized (improved) level. This results in significant improvements in the efficiency and, hence, the sustainability of the hydraulic system. For example, the proposed technology allows to mimic the beneficial operational behavior of a variable displacement pump with a low-cost, quiet and efficient fixed displacement pump. Furthermore, precise control over the hydraulic system is provided as the rotational speed is adjusted based on the at least one pressure measurement in the hydraulic system. Accordingly, (quick) responses to changes in load or operating conditions of the lifting equipment are possible. The target value for the pressure difference further allows to adapt the rotational speed control to a desired operation strategy for the lifting equipment.Brief description of the Figures

[0013] Some examples of apparatuses and / or methods will be described in the following by way of example only, and with reference to the accompanying figures, in which Fig. 1 illustrates an example of an apparatus for determining a target rotational speed for a rotary drive; Fig. 2 illustrates a first exemplary hydraulic system comprising a fixed displacement pump; Fig. 3 illustrates a second hydraulic system comprising a variable displacement pump; Fig. 4 illustrates an example of a system; Fig. 5 illustrates an example of a vehicle; and Fig. 6 illustrates a flowchart of an example of a method for determining a target rotational speed for a rotary drive. Detailed Description

[0014] Some examples are now described in more detail with reference to the enclosed figures. However, other possible examples are not limited to the features of these embodiments described in detail. Other examples may include modifications of the features as well as equivalents and alternatives to the features. Furthermore, the terminology used herein to describe certain examples should not be restrictive of further possible examples.

[0015] Throughout the description of the figures same or similar reference numerals refer to same or similar elements and / or features, which may be identical or implemented in a modified form while providing the same or a similar function. The thickness of lines, layers and / or areas in the figures may also be exaggerated for clarification.

[0016] When two elements A and B are combined using an "or", this is to be understood as disclosing all possible combinations, i.e. only A, only B as well as A and B, unless expressly defined otherwise in the individual case. As an alternative wording for the same combinations, "at least one of A and B" or "A and / or B" may be used. This applies equivalently to combinations of more than two elements.

[0017] If a singular form, such as "a", "an" and "the" is used and the use of only a single element is not defined as mandatory either explicitly or implicitly, further examples may also use several elements to implement the same function. If a function is described below as implemented using multiple elements, further examples may implement the same function using a single element or a single processing entity. It is further understood that the terms "include", "including", "comprise" and / or "comprising", when used, describe the presence of the specified features, integers, steps, operations, processes, elements, components and / or a group thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, processes, elements, components and / or a group thereof.

[0018] Fig. 1 schematically illustrates an apparatus 100 for determining a target rotational speed for a rotary drive (rotary actuator, rotary motion drive) 130 driving a displacement pump 125 of a hydraulic system of a lifting equipment 120.

[0019] The lifting equipment 120 is any machinery (device) for lifting loads (e.g., goods and / or people) using hydraulic power. For example, the lifting equipment may be a crane such as a knuckle boom or loader crane for loading and unloading goods (loads). Alternatively, the lifting equipment may, e.g., be the crane section of a mobile crane (with a vehicle being a mobile platform having mounted thereon the crane section) or the entire mobile crane. In some examples, the lifting equipment may be a stationary crane. In other examples, the lifting equipment may, e.g., be a forklift comprising a pronged device in the front, called forks, which can be inserted under loads to lift and carry them. In still other examples, the lifting equipment may, e.g., be a lifting platform (elevating platform of lift table) comprising a platform supported by a mechanical structure in a liftable manner to a base of the lifting platform.

[0020] The rotary drive 130 is configured to produce (provide) controlled rotational movement. The target rotational speed denotes the desired or intended speed at which the rotary drive 130 should rotate. In other words, the target rotational speed refers to the desired or intended speed of the rotational movement to be provided by the rotary drive 130.

[0021] As schematically indicated in Fig. 1, the displacement pump 125 of the lifting equipment 120 is driven by the rotary drive 130 to provide hydraulic power. For example, the hydraulic power may be provided by means of a flow of hydraulic fluid caused (generated) by the displacement pump 125 when driven by the rotary drive 130. In general, any type of hydraulic fluid suitable for transmitting power efficiently may be used. For example, the hydraulic fluid may be a mineral oil-based hydraulic fluid or a synthetic hydraulic fluid. The hydraulic power provided by the displacement pump 125 is used by one or more hydraulic actuators (which may be understood as consumers) of the lifting equipment 120 (not illustrated in Fig. 1). The one or more hydraulic actuators of the lifting equipment 120 are hydraulically coupled to the displacement pump 125. The displacement pump 125 and the one or more hydraulic actuators of the crane 120 form the hydraulic system of the lifting equipment 120.

[0022] For example, the one or more hydraulic actuators may be one or more hydraulic cylinders and / or one or more slewing drives of the lifting equipment 120 for providing various functions of the lifting equipment 120 such as lifting, lowering, extending, tilting, retracting, rotating, and stabilizing. For reasons of simplicity, various elements of the lifting equipment 120 such as its one or more hydraulic cylinders, one or more slewing drives, equipment base (e.g., the crane base of a crane or the base of a lifting platform), lifting devices (e.g., a boom or crane arm of a crane, the forks of a forklift, the platform of a lifting platform) or outriggers (e.g., crane legs) are not illustrated in Fig. 1.

[0023] The rotary drive 130 may be part of the lifting equipment 120. In other examples, the rotary drive 130 may be external to the lifting equipment 120 (e.g., external to a crane such as a loader crane). In other words, the rotary drive 130 is not part of the lifting equipment 120 in some examples. The rotary drive 130 may be any device or system capable of converting energy into mechanical rotation (rotational movement) in a controlled manner. For example, the rotary drive 130 may be an electric rotary drive comprising one or more electric motors for generating the rotational movement. According to examples of the present disclosure, the rotary drive 130 may be an electric rotary drive on a vehicle having mounted thereon (holding, carrying) the lifting equipment 120 or being the lifting equipment 120. Electric rotary drives are also denoted as electric Power Take-Offs (ePTOs). In alternative examples, the rotary drive 130 may be a Power Take-Off (PTO) driven by a drive system 140 (e.g., a combustion engine and optionally a gearbox). According to examples of the present disclosure, the rotary drive 130 may be a PTO of a vehicle having mounted thereon or being the lifting equipment 120. The vehicle may be a land vehicle (e.g., wheeled, tracked or railed) or a watercraft (e.g., a ship, a boat or a barge). For example, the lifting equipment 120 may be mounted to a vehicle such as a truck. For example, the lifting equipment 120 may be a crane (e.g., a knuckle boom or loader crane) mounted to a vehicle such as a truck for loading and unloading goods onto and from the vehicle. The rotary drive 130, in particular when implemented as electric rotary drive, may be detachably attached to the vehicle. In other examples, the rotary drive 130 may be fixedly attached to the vehicle. In still other examples, the rotary drive 130 may be external to the vehicle, i.e., not be part of the vehicle. For example, the rotary drive 130 may be part of an external aggregate or power unit to which the vehicle or the lifting equipment 120 (e.g., a stationary crane) is mechanically coupleable. Accordingly, the vehicle or the lifting equipment 120 may be configured to mechanically couple the displacement pump 125 to the external rotary drive. For reasons of clarity, the vehicle is not shown in Fig. 1.

[0024] The apparatus 100 may be part of the lifting equipment 120 (e.g., be part of a crane). According to examples, equipment control circuitry (equipment controller) 121 for controlling operation of the lifting equipment 120 may comprise the apparatus 100. The equipment control circuitry 121 may, e.g., be coupled to the displacement pump 125 and control operation of the displacement pump 125 and optionally further elements of the lifting equipment 120. In other examples, the apparatus 100 and the equipment control circuitry 121 may be separate elements of the lifting equipment 120. In case the lifting equipment 120 is a crane, the equipment control circuitry 121 may be crane control circuitry (a crane controller) for controlling operation of the crane. In alternative examples, the apparatus 100 may be external to the lifting equipment 120, i.e., not be part of the lifting equipment 120. For example, a computing cloud communicatively coupled to the lifting equipment 120 (e.g., via a wireless connection) may comprise or be the apparatus 100. In still other examples, the vehicle having mounted thereon the lifting equipment 120 may comprise the apparatus 100. In examples, in which the rotary drive 130 is part of an aggregate external to the vehicle, the aggregate may comprise the apparatus 100.

[0025] The apparatus 100 comprises processing circuitry 110. For example, the processing circuitry 110 may be a single dedicated processor, a single shared processor, or a plurality of individual processors, some of which or all of which may be shared, a digital signal processor (DSP) hardware, an application specific integrated circuit (ASIC), a system-on-a-chip (SOC), a neuromorphic processor or a field programmable gate array (FPGA). The processing circuitry 110 may optionally be coupled to, e.g., memory such as read only memory (ROM) for storing software, random access memory (RAM) and / or non-volatile memory. For example, the apparatus 100 may comprise memory configured to store instructions, which when executed by the processing circuitry 110, cause the processing circuitry 110 to perform the steps and methods described herein.

[0026] The processing circuitry 110 is configured to receive first input data 101. The first input data 101 indicate (are encoded with information about) at least one pressure measurement in (at) the hydraulic system. The at least one pressure measurement may, e.g., be one or more (absolute) pressures measured in (at) the hydraulic system, one or more pressure differences (differential pressures) measured in (at) the hydraulic system or a combination thereof. The first input data 101 may, e.g., be received from one or more pressure sensors in (at) the hydraulic system or an intermediate entity (element, circuitry) that is coupled between the apparatus 100 and the one or more pressure sensors (e.g., a buffer memory). The first input data 101 as well as other input data to the processing circuitry 110 may be real-time data (i.e., data that is delivered / received immediately after collection / generation without significant delay). This may ensure that the target rotational speed can be dynamically adjusted.

[0027] Additionally, the processing circuitry 110 is configured to determine the target rotational speed for the rotary drive 130 based on a first value and a second value. The first value represents a pressure difference between a load pressure in the hydraulic system and a pump pressure of the displacement pump. The first value is based on the first input data 101. In other words, the first value is derived from the first input data 101. Accordingly, the first value reflects the actual (pressure) conditions in the hydraulic system. The second value is a target value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125.

[0028] The processing circuitry 110 may, e.g., be configured to determine the target rotational speed for the rotary drive 130 based on a difference between the first value and the second value, i.e., the pressure difference between the first value and the second value. In other words, the processing circuitry 100 may compare the first value to the second value and determine the target rotation speed for the rotary drive 130 based on the comparison. For example, the processing circuitry 110 may be configured to increase the target rotational speed if the first value indicates a smaller pressure difference than the second value, and vice versa. Increasing the target rotational speed allows to increase the volume flow of the hydraulic fluid in the hydraulic system and, hence, the pressure difference between the pump pressure of the displacement pump and the load pressure in the hydraulic system. This ensures that the apparatus 100 constantly strives to achieve or maintain the target pressure difference indicated by the second value.

[0029] The load pressure in the hydraulic system is the actual pressure in the hydraulic system while operating the lifting equipment. The load pressure depends on the movements or actions of the lifting equipment 120 currently being driven by the hydraulic system. For example, if a load is lifted by the lifting equipment 120, the weight of the load and the specific movement of the lifting equipment 120 for lifting the load determine the load pressure in the hydraulic system. Similarly, if an outrigger of the lifting equipment 120 is moved, the movement of the outrigger determines the load pressure in the hydraulic system. The load pressure may be measured at various points of the hydraulic system. For example, the load pressure may be the pressure at a hydraulic actuator of the hydraulic system, the pressure at a control valve of the hydraulic system for controlling (regulating) the flow of the hydraulic fluid in the hydraulic system, the pressure in a dedicated load sensing line of the hydraulic system, or a combination thereof.

[0030] The pump pressure of the displacement pump 125 is the pressure generated by the displacement pump for moving the hydraulic fluid through the hydraulic system. The pump pressure may be measured at various points of the displacement pump 125. For example, the pump pressure may be the pump output pressure at the pump outlet. Similarly, the pump pressure may be the pressure in the supply line, which fluidically couples the pump outlet with the remaining hydraulic system, immediately after the pump outlet. In some example, the pump pressured may be the pressure at the slide valve (control valve, spool) of the displacement pump 125.

[0031] The first value represents the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125, i.e., the first value characterizes the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125. The first value may be the exact pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125, but need not. Some examples of how to determine the first value will be given below.

[0032] The target value for the pressure difference denotes the desired, demanded or intended pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125. The target value for the pressure difference, may, e.g., be predefined by a manufacturer of the lifting equipment 120. For example, the target value for the pressure difference may be set by the manufacturer of the lifting equipment 120 according to a desired operation strategy for the lifting equipment 120. The processing circuitry 110 may, e.g., be configured to read the second value from a memory of the lifting equipment 120. The manufacturer may, e.g., store the second value in the memory when manufacturing the lifting equipment 120. In other examples, the second value may be adjustable or selectable from a plurality of predefined second values. Some examples will be described in greater detail below.

[0033] The processing circuitry 110 may be configured to determine the target rotational speed using a predefined computational model. The computational model is a mathematical representation (e.g., a set of mathematical equations) for determining the target rotational speed for the rotary drive 130 taking into account the first value, the second value and optionally further inputs. The computational model may use various signal and / or data processing operations such as signal / data addition, subtraction, multiplication, division, integration, derivation, filtering (e.g., discrete, continuous or both), delaying, etc. to determine the target rotational speed based on the various inputs to the processing circuitry 110.

[0034] The processing circuitry 110 is configured to output control data 105 indicating the determined target rotational speed. The control data 105 are for controlling the rotational speed of the rotary drive 130. The control data 105 may be output by the processing circuitry 110 to various entities - depending on the implementation of the rotary drive 130. For example, the processing circuitry 110 may be configured to output the control data 105 to the rotary drive 130 such that control circuitry of the rotary drive 130 may control the rotary drive 130 to adjust its rotational speed to the determined target rotational speed. In other examples, the processing circuitry 110 may be configured to output the control data 105 to control circuitry for the rotary drive 130 external to the rotary drive 130 such that the external control circuitry may control the rotary drive 130 to adjust its rotational speed to the determined target rotational speed. For example, if the rotary drive is an electric rotary drive on a vehicle having mounted thereon or being the lifting equipment 120, the processing circuitry 110 may be configured to output the control data 105 to the electric rotary drive such that control circuitry of the electric rotary drive may control the electric rotary drive to adjust its rotational speed to the determined target rotational speed. In case the rotary drive 130 is driven by the drive system 140, the processing circuitry 110 may be configured to output the control data 105 to the drive system 140 or control circuitry for the drive system 140 external to the drive system 140 such that the drive system 140 is controlled to adjust the driving of the rotary drive 130 such that the rotational speed of the rotary drive 130 is adjusted to the determined target rotational speed. For example, if the rotary drive 130 is a PTO of a vehicle having mounted thereon or being the lifting equipment 120, the processing circuitry 110 may be configured to output the control data 105 to the vehicle such that vehicle control circuitry of the vehicle may control the drive system 140 of the vehicle (e.g., a combustion engine of the vehicle) based on the control data 105. If the rotary drive 130 is part of an aggregate external tot the vehicle, the processing circuitry 110 may be configured to output the control data 105 to the aggregate such that control circuitry of the rotary drive 130 or control circuitry of the aggregate for the rotary drive 130 (i.e., control circuitry not being part of the rotary drive130) may control the rotary drive 130 to adjust its rotational speed to the determined target rotational speed.

[0035] By adjusting the target rotational speed for the rotary drive 130 based on the first value representing the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump, the apparatus 100 ensures that the displacement pump 125 operates at an optimized level. This results in significant improvements in the efficiency and, hence, the sustainability of the hydraulic system. For example, if the displacement pump 125 is a fixed displacement pump, the apparatus 100 allows to mimic the beneficial operational behavior of a variable displacement pump with the low-cost, quiet and efficient fixed displacement pump. In particular, by adjusting the target rotational speed for the rotary drive 130, the apparatus 130 allows to ensure that the fixed displacement pump 125 is not underutilized, which optimizes energy consumption and reduces unnecessary strain on the hydraulic components. By adjusting the target rotational speed for the rotary drive 130, the flow rate of the hydraulic fluid generated by the fixed displacement pump may be varied like for a variable displacement pump. This may lead to energy savings and lower operational costs. On the other hand, if the displacement pump 125 is a variable displacement pump, the apparatus 100 allows to further increase the efficiency of the variable displacement pump. The apparatus 100 provides precise control over the hydraulic system as the rotational speed is adjusted based on the at least one pressure measurement in the hydraulic system. Accordingly, (quick) responses to changes in load or operating conditions of the lifting equipment 120 are possible. The target value for the pressure difference further allows to adapt the rotational speed control to a desired operation strategy for the lifting equipment 120.

[0036] As indicated above, the measured pressure(s) indicated by the first input data 101 may be manifold. Accordingly, the derivation of the first value may be manifold. In the following a few non-limiting examples will be described in greater detail.

[0037] According to a first example, the first input data 101 may be encoded with (indicate) at least one measurement value (e.g., a time series of measurement values) for the load pressure in the hydraulic system and at least one measurement value (e.g., a time series of measurement values) for the pump pressure of the displacement pump 125. In other words, the first input data 101 include direct measurements of the load pressure in the hydraulic system and the pump pressure of the displacement pump 125. The processing circuitry 110 may be further configured to determine the first value based on the at least one measurement value for the load pressure in the hydraulic system and the at least one measurement value for the pump pressure of the displacement pump 125. In this example, the first value is / represents the exact pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125. Accordingly, the first value accurately reflects the actual operating condition of the hydraulic system. As described above, the first value (i.e., the pressure difference derived from the first input data 101) is then used to determine the target rotational speed for the rotary drive 130. This ensures that the displacement pump 125 is operating in an optimized manner according to real-time system demands.

[0038] By using direct measurements for both the load pressure and the pump pressure, the target rotational speed for the rotary drive 130 is determined based on a highly accurate description (understanding) of the hydraulic conditions in the hydraulic system. The precise calculation of the pressure difference allows the apparatus 100 to adjust the speed of the displacement to exactly what is needed, avoiding unnecessary energy use. This optimization contributes to lower operational costs and more efficient use of power, especially in hydraulic systems with a fixed displacement pump that operate under varying loads.

[0039] In a second example, the processing circuitry 110 may be configured to modify, prior to determining the first value, the at least one measurement value for the load pressure in the hydraulic system and / or the at least one measurement value for the pump pressure of the displacement pump 125 by a predefined modification value. In other words, the processing circuitry 110 may modify at least one of the load pressure measurement and the pump pressure measurement by a predefined modification value. The predefined modification value refers to a set value or adjustment factor that is used to modify the at least one measurement value for the load pressure in the hydraulic system and / or the at least one measurement value for the pump pressure of the displacement pump 125 by a certain amount. For example, if a measurement value for the load pressure in the hydraulic system (or the pump pressure of the displacement pump 125) is X (in units of, e.g., Pa, Bar or psi) and the predefined modification value is Y (in units of, e.g., Pa, Bar or psi), the resulting (modified) value for the load pressure in the hydraulic system (or the pump pressure of the displacement pump 125) is Z = X + Y. In other examples, if an adjustment factor A (which is dimensionless, i.e., a scalar value) is used instead of the set value Y, the resulting value for the load pressure in the hydraulic system (or the pump pressure of the displacement pump 125) is Z = X . A. By modifying the load pressure measurement and / or the pump pressure measurement before calculating the pressure difference, the apparatus 100 may account for various factors that might otherwise lead to inaccuracies. The modification may, e.g., allow the apparatus 100 to compensate for known inefficiencies, such as pressure losses due to long hydraulic lines, an offset of a sensor measuring the load pressure or the pump pressure, elevation changes, or mechanical wear.

[0040] The predefined modification value applied to the load pressure measurement may be customized or selected to align with different operation strategies for the lifting equipment 120. For instance, if a strategy prioritizes energy efficiency, the modification value could be adjusted to slightly reduce the measurement value for the load pressure, leading to a lower target rotational speed and thus conserving energy. Conversely, if the operation strategy emphasizes maximum performance or speed, the modification value could be adjusted to increase the measurement value for the load pressure, resulting in a higher target rotational speed that enhances the lifting equipment 120's responsiveness and speed.

[0041] The modification value may be adjusted or selected based on specific operational conditions such as load type, environmental factors (e.g., temperature, altitude) or equipment wear. For example, if operating at high altitudes where pressure conditions differ, the modification value may be set to compensate for these changes, ensuring the lifting equipment 120 operates optimized under those conditions.

[0042] According to a third example, the first input data 101 may be encoded with at least one measurement value (e.g., a time series of measurement values) for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125. In other words, the first input data 101 include a direct measurement of the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125. In this example, instead of separately measuring the load pressure and pump pressure and then calculating the pressure difference (as described above), the pressure difference between these two points is measured directly. Accordingly, the first value may be the at least one measurement value for the pressure difference indicated by the first input data 101. This direct measurement approach simplifies the process by eliminating the need for the apparatus 100 to determine (compute) the pressure difference from two separate measurements. Instead, the apparatus 100 relies on a sensor or sensors specifically designed to measure the difference in pressure between the load and pump pressures. By directly measuring the pressure difference, the apparatus 100 avoids potential errors that could arise from measuring load and pump pressures separately and then determining the difference. Since the apparatus 100 does not need to determine the pressure difference from two separate measurements, it can respond more quickly to changes in the hydraulic system. This faster response time may be beneficial in dynamic environments where load conditions can change rapidly.

[0043] According to a fourth example, the pressure difference measurement may be manipulated analogously to what is described above for the manipulation of the load pressure measurement and / or the pump pressure measurement. In other words, if the first input data 101 are encoded with at least one measurement value (e.g., a time series of measurement values) for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125, the processing circuitry 110 may be configured to modify the at least one measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125 by a predefined modification value (see above for examples) to obtain at least one modified measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125. Accordingly, the first value may be the at least one modified measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump 125. Using the modified pressure difference measurement may allow the apparatus 100 to account for various factors that might otherwise lead to inaccuracies - analogously to what is described above.

[0044] In a fifth example, the first input data 101 may be encoded (only) with at least one measurement value (e.g., a time series of measurement values) for the pump pressure of the displacement pump. In this example, the first input data 101 are not encoded (do not indicate) measurement values for the load pressure in the hydraulic system. The processing circuitry 110 may be configured to determine the first value based on a predefined reference value for the load pressure in the hydraulic system and the at least one measurement value for the pump pressure of the displacement pump. For example, the predefined reference value for the load pressure in the hydraulic system may be subtracted from the at least one measurement value for the pump pressure of the displacement pump, or vice versa. In this example, instead of using a direct measurement for the load pressure, the apparatus 100 uses a predefined reference value that represents the load pressure in the hydraulic system. For example, the predefined reference value may be an expected or a desired load pressure in the hydraulic system. The predefined reference load pressure may be determined from historical data (e.g., historical measurement values for the load pressure in the hydraulic system), system design specifications or operational requirements.

[0045] By using a predefined reference value for the load pressure, the apparatus 100 eliminates the need for a direct load pressure measurement sensor. This simplifies the lifting equipment 120's design, reducing the number of sensors required and potentially lowering costs. Using a predefined reference value allows the apparatus 100 to operate based on known, stable parameters. This predictability may be beneficial in environments where the load pressure does not vary significantly or where it is crucial to maintain consistent operation regardless of small variations in actual load conditions. The predefined reference value may be adjusted, selected or set based on the specific operation strategy or the desired performance of the hydraulic system or the lifting equipment 120. For example, if safety is a priority, the reference value could be set conservatively to ensure the hydraulic system operates within safe limits.

[0046] As indicated above, the first input data 101 as well as other input data to the processing circuitry 110 may be time series data. Time series data is a sequence of data points in chronological order for succeeding time instants. Accordingly, the first input data 101 may indicate a sequence of data points in chronological order for succeeding time instants for each pressure measurement in the hydraulic system. Each data point in the respective indicates the measurement value for the respective pressure measurement for the respective time instant. As described above, the time series data may include continuous or periodic measurements of one or more of the load pressure in the hydraulic system, the pump pressure of the displacement pump 125 and the pressure difference between them. For example, the first input data 101 may be a continuous stream of data points over time. The data points may be equally spaced in time but need not. In these examples, the processing circuitry 110 may be configured to continuously update the first value based on the first input data 101 and to continuously determine the target rotational speed for the rotary drive 130 based on the updated first value. In other words, the first value, representing the pressure difference, is not a static value in these examples but is continuously redetermined (recalculated) as new data points from the time series are received. This ensures that the first value accurately reflects the current state of the hydraulic system at all times. This continuous updating allows the apparatus 100 to respond immediately to changes in pressure, whether due to varying loads, environmental factors, or operational demands. As the first value is updated, the processing circuitry 110 simultaneously redetermines (recalculates) the target rotational speed for the rotary drive 130. This continuous recalculation means that the displacement pump 125's speed is always optimized for the current conditions. By constantly optimizing the displacement pump 125's rotational speed based on up-to-date pressure data, the lifting equipment 120 may operate more efficiently. This minimizes energy consumption and reduces wear and tear on the displacement pump 125 and other components, leading to longer equipment life and lower operating costs.

[0047] In some examples, the processing circuitry 110 may be configured to receive second input data 102 indicating a user input. The user input indicates a user setting for the target value for the pressure difference. For example, the user input may indicate a desired target value for the pressure difference, i.e., a specific value for the target value for the pressure difference, a modification value for modifying a current or previously used target value for the pressure difference, or a selection of one of a plurality of predefined target values for the pressure difference. The second input data 102 may, e.g., be received from a remote control (not illustrated in Fig. 1). The remote control is a device for an operator (user) of the lifting equipment 120 for controlling the lifting equipment 120 from a distance. However, the present disclosure is not limited thereto. In other examples, the second input data 102 may be received from another entity such as an element or circuitry of the lifting equipment 120 (e.g., a Human-Machine Interface, HMI, of the lifting equipment 120), a mobile device (e.g., a mobile phone, a laptop-computer or a tablet-computer) of the operator of the lifting equipment 120 or a remote server.

[0048] The processing circuitry 110 may be further configured to determine the target value for the pressure difference based on the user input. For example, the processing circuitry 110 may use the specific value indicated by the user input for the target value for the pressure difference, modify a currently or previously used target value for the pressure difference based on the modification value indicated by the user input or use the one of the plurality of predefined target values for the target value for the pressure difference. By setting the target value, the user has direct influence over the lifting equipment 120's operation, tailoring it to specific operation strategies, needs or preferences. For example, the user may want to prioritize energy efficiency, precision, or speed depending on the task at hand.

[0049] According to some examples, the processing circuitry 110 may be configured to receive third input data 103. The third input data 103 indicate a measured temperature of the hydraulic fluid in the hydraulic system. The third input data 103 may, e.g., be received from one or more temperature sensors in (at) the hydraulic system or an intermediate entity (element, circuitry) that is coupled between the apparatus 100 and the one or more temperature sensor (e.g., a buffer memory). The processing circuitry 110 may further be configured to determine the target value for the pressure difference based on the measured temperature. Properties of the hydraulic fluid, such as viscosity, may change significantly with temperature, affecting the hydraulic system's performance. The temperature-based adjustment of the target value for the pressure difference allows the apparatus 100 to adapt dynamically to changing thermal conditions, ensuring that the hydraulic system operates optimally regardless of temperature variations. If the fluid temperature is low, the hydraulic fluid may be more viscous, which can lead to higher pressure losses in the hydraulic system. In response, the processing circuitry 110 may increase the target pressure difference to compensate for these losses. Conversely, if the fluid temperature is high, the fluid may become less viscous, reducing pressure losses. The processing circuitry 110 may then decrease the target pressure difference to avoid overcompensation and maintain efficient operation.

[0050] In some examples, the processing circuitry 110 may be configured to receive fourth input data 104. The fourth input data 104 indicate at least one of a status of the lifting equipment 120 and a movement performed (currently or in the future) by the lifting equipment 120. The status of the lifting equipment 120 refers to the operational condition, i.e., the current state or operational parameters of the lifting equipment 120. For example, the status of the lifting equipment 120 may indicate a current operation mode of the lifting equipment 120. The status of the lifting equipment 120 may, e.g., indicate whether the lifting equipment 120 is operating in an idle mode, an operation mode with the primary goal of optimizing power consumption, an operation with the primary goal of maximize performance of the lifting equipment 120, or an operation mode that is a trade-off between the two foregoing operation modes. The movement performed by the lifting equipment 120 is the specific movement being carried out (currently or in the future) by the lifting equipment 120. For example, the movement may be one of lifting, lowering, extending, tilting, retracting, rotating, and stabilizing. The third input data 103 may, e.g., be received from the equipment control circuitry 121, one or more sensors of (at) the lifting equipment or a combination thereof.

[0051] The processing circuitry 110 may be further configured to determine the target value for the pressure difference based on the at least one of the status of the lifting equipment and the movement performed by the lifting equipment.

[0052] The fourth input data 104 allow to determine, set or adjust the target value for the pressure difference in a context-aware manner. For example, different operation modes of the crane are linked to different operation strategies foreseen for the lifting equipment 120. By adjusting the target value for the pressure difference accordingly, the apparatus 100 allows to adjust the performance of the lifting equipment 120 for different types of operation strategies. Analogously, the apparatus 100 may optimize the hydraulic system's performance for different types of movements. For instance, when performing a high-speed movement, the apparatus 100 may adjust the target pressure difference to ensure sufficient power and stability. Conversely, during delicate operations, such as placing a load precisely, the apparatus 100 may reduce the pressure difference for finer control.

[0053] Measurement of pressure in two exemplary hydraulic systems of lifting equipment will be described in the following with reference to Fig. 2 and Fig. 3.

[0054] Fig. 2 illustrates a hydraulic system 200 of a lifting equipment. The hydraulic system 200 comprises two hydraulic actuators 210 and 220, which are depicted as hydraulic cylinders in the example of Fig. 2. It is to be noted that more or less hydraulic actuators may be used. Furthermore, different types of hydraulic actuators may be used.

[0055] The hydraulic system 200 comprises a fixed displacement pump 225 to provide hydraulic power by creating a flow of hydraulic fluid in the hydraulic system 200. The fixed displacement pump 225 is driven by rotary drive 230 to provide the hydraulic power. The fixed displacement pump 225 delivers a constant flow of the hydraulic fluid during operation.

[0056] Two directional control valves 240 and 245 are provided in the hydraulic system 200 to control the flow of the hydraulic fluid to the hydraulic actuators 210 and 220. The directional control valves 240 and 245 are hydraulically coupled between the fixed displacement pump 225 and the hydraulic actuators 210 and 220. The respective position of the valves 240 and 245 determines whether the hydraulic fluid is directed to move the respective hydraulic actuator 210, 220 in one direction or another, or if the fluid is blocked, keeping the respective hydraulic actuator 210, 220 in place. The positions of the directional control valves 240 and 245 are controlled via the control lever 205 illustrated in the left part of Fig. 2. The control lever 205 allows a user or operator to direct the hydraulic fluid to either side of the hydraulic actuators 210 and 220 to control extension and retraction of the hydraulic actuators 210 and 220, depending on the task.

[0057] The hydraulic system 200 comprises an inlet pressure compensator 250 to manage and stabilize the flow rate of the hydraulic fluid within the hydraulic system 200 while also compensating for pressure variations. This ensures that the flow delivered to the hydraulic actuators 210 and 220 remains consistent, regardless of load changes or fluctuations in the hydraulic system 200's overall pressure. The primary function of the inlet pressure compensator 250 is to control the rate at which the hydraulic fluid is supplied to the hydraulic actuators 210 and 220. By maintaining a steady flow rate, the hydraulic system 200 may ensure smooth and predictable movement of the hydraulic actuators 210 and 220, which is essential for precise operations like lifting or positioning loads. The inlet pressure compensator 250 adjusts the flow to maintain the desired pressure level at the hydraulic actuators 210 and 220, even when the hydraulic system 200's load conditions change. For example, if the load increases, causing a drop in pressure, the inlet pressure compensator 250 adjusts the flow to maintain sufficient pressure for the required operation. In particular, the inlet pressure compensator 250 regulates the system pressure via the volume flow. Excess volume flow is diverted to a reservoir in the hydraulic system 200. The system pressure is maintained with a defined pressure difference (indicated by the spring of the inlet pressure compensator 250) above the detected load pressure.

[0058] A pressure relief valve 260 is provided in the hydraulic system 200 to protect the hydraulic system from excessive pressure by allowing hydraulic fluid to bypass or be diverted when the pressure exceeds a predefined safe limit. The pressure relief valve 260 is configured to open at a predefined pressure threshold. If the pressure in the hydraulic system 200 exceeds this limit, the pressure relief valve 260 opens to allow excess hydraulic fluid to flow out, usually returning to a reservoir or to a low-pressure area in the hydraulic system 200. This prevents the buildup of dangerous pressure levels that could damage components or lead to system failure.

[0059] The hydraulic system 200 further comprises a return filter 270 to maintain the cleanliness and proper functioning of the hydraulic system 200. The return filter 270 is configured to remove contaminants from the hydraulic fluid as it returns from the hydraulic actuators 210 and 220 to avoid damage of hydraulic components in the hydraulic system (e.g., by abrasion, blockages, scoring of surfaces or seal damage potentially caused by the contaminants).

[0060] A load sensing line 280 of the hydraulic system 200 allows to monitor the load pressure in the hydraulic system 200. In the example of Fig. 2, the load sensing line 280 is a channel in a main control valve of the hydraulic system 200. The main control valve is indicated in Fig. 2 by the dashed line at which the reference sign 280 is pointing.

[0061] A pressure sensor 290 is hydraulically coupled to the load sensing line 280 and a pump outlet 226 of the fixed displacement pump 225. The pressure sensor 290 is configured to measure the pressure difference between the load pressure in the hydraulic system 200 and the pump output pressure of the displacement pump 225.

[0062] The pressure difference measured by the pressure sensor 290 is used as described above to determine the target rotational speed for the rotary drive 230.

[0063] Compared to fixed displacement pumps, variable displacement pumps are generally more expensive than fixed displacement pumps, have higher noise emissions but are also more efficient if the volume flow requirement is nearly the same as the volume flow production. By controlling the rotational speed of the rotary drive 230 based on the pressure difference measured by the pressure sensor 290 and the target value for the pressure difference as described above, the beneficial operational behavior of a variable displacement pump may be mimicked (achieved) with the low-cost, quiet and efficient fixed displacement pump 225.

[0064] In particular, by adjusting the target rotational speed for the rotary drive 230, the flow rate of the hydraulic fluid generated by the fixed displacement pump 225 may be varied like for a variable displacement pump.

[0065] An alternative hydraulic system 300 using a variable displacement pump 325 instead of the fixed displacement pump 225 is illustrated in Fig. 3. For reasons of simplicity, mainly the differences between the hydraulic systems 200 and 300 will be described in the following.

[0066] The hydraulic system 300 omits (does not comprise) the inlet pressure compensator 250 compared to the hydraulic system 200. In the hydraulic system 300, the pressure relief valve 260 is arranged at the position of the inlet pressure compensator 250 in the hydraulic system 200.

[0067] At the position of the pressure relief valve 260 in the hydraulic system 200, the hydraulic system 300 comprises a load sensing regulator 310 configured regulate (control) the variable displacement pump 325's displacement based on the pressure in the load sensing line 280.

[0068] The load sensing regulator 310 continuously monitors the pressure difference between the load sensing line 280 and the pump pressure provided by the variable displacement pump 325. If the pressure at the load sensing line 280 indicates an increased load, the load sensing regulator 310 is configured to adjust the variable displacement pump 325 to increase displacement, providing more flow to maintain the desired performance. Conversely, if the pressure at the load sensing line 280 drops (indicating a reduced load), the load sensing regulator 310 is configured to adjust the variable displacement pump 325 to decrease displacement, reducing the flow to save energy and prevent overpressure. The load sensing regulator 310 adjusts the displacement of the variable displacement pump 325 via a mechanism 320. The mechanism 320 is controlled by the load sensing regulator 310 and configured to change the angle of the variable displacement pump 325's swash plate or through other means that alter the internal geometry of the variable displacement pump 325.

[0069] Analogously to the hydraulic system 200, the pressure sensor 290 is hydraulically coupled to the load sensing line 280 and the pump outlet 326 of the variable displacement pump 325. The pressure sensor 290 is configured to measure the pressure difference between the load pressure in the hydraulic system 200 and the pump output pressure of the displacement pump 325. The pressure difference measured by the pressure sensor 290 is used as described above to determine the target rotational speed for the rotary drive 230.

[0070] By controlling the rotational speed of the rotary drive 230 based on the pressure difference measured by the pressure sensor 290 and the target value for the pressure difference as described above, the flow rate of the hydraulic fluid generated by the variable displacement pump 325 may be varied. Accordingly, two mechanisms for varying the flow rate of the hydraulic fluid generated by the variable displacement pump 325 are provided: 1) Changing the angle of the variable displacement pump 325's swash plate or altering the internal geometry of the variable displacement pump 325 in another way; and 2) Changing the target rotational speed for the rotary drive 230 driving the variable displacement pump 325.

[0071] This allows to further increase the efficiency of the variable displacement pump 325.

[0072] In the examples of Fig. 2 and Fig. 3, the pressure sensor 290 measures the pressure difference between the load pressure in the hydraulic system 200 and the pump output pressure of the displacement pump 225. As described above, two separate pressure sensors may be used in alternative examples to measure the load pressure in the hydraulic system 200 and the pump output pressure of the displacement pump 225 separately. In still other examples, only the pump output pressure of the displacement pump 225 may be measured via a pressure sensor, but not the load pressure in the hydraulic system 200.

[0073] Fig. 4 schematically illustrates a system 400 using the apparatus 100 described above.

[0074] The system 400 comprises a lifting equipment 410 such as, e.g., a stationary crane. The system 400 further comprises a rotary drive 420, which may be part of the lifting equipment 410 or be external to the lifting equipment 410. For example, the rotary drive 420 may be part of aggregate external to the lifting equipment 410. The rotary drive 420 is configured to drive a displacement pump 411 in a hydraulic system of the lifting equipment 410. The displacement pump 411 generates a flow of hydraulic fluid in the hydraulic system. The hydraulic system comprises at least one hydraulic actuator 412 (hydraulically) coupled to the displacement pump 411 and drivable by the hydraulic fluid.

[0075] The apparatus 100 receives the first input data 101 indicating the at least one pressure measurement in the lifting equipment 410's hydraulic system and generates the control data 105 as described above.

[0076] Control circuitry 430 of the system 400 is configured to control the rotary drive 420 based on the control data 105. The control circuitry 430 is as described above with reference to Fig. 1.

[0077] The system 400 may achieve high efficiency of the lifting equipment 410's hydraulic system. For example, if a low-cost, quiet and efficient fixed displacement pump is used for the displacement pump 411, the proposed technology allows to mimic the beneficial operational behavior of a variable displacement pump. Similarly, if a variable displacement pump is used for the displacement pump 411, the efficiency of the variable displacement pump may be further improved by the proposed technology. Furthermore, the control of the rotation speed may be adapted to a desired operation strategy for the lifting equipment 410 via the target value for the pressure difference.

[0078] Fig. 5 further illustrates a truck as an exemplary vehicle 500 having mounted thereon (holding) a loader crane (knuckle boom crane) 520 as an exemplary lifting equipment. In the example of Fig. 5, the loader crane 520 comprises hydraulic cylinders 521, 522 and 523 for driving (moving) the crane arm 524 of the loader crane 520. The crane arm 524 is an exemplary lifting device of a lifting equipment. Additionally, the loader crane 520 comprises hydraulic cylinders 525 for driving (moving) the outriggers 526. Further illustrated in Fig. 5 is the slewing drive 528 for rotating the crane arm 524 relative to the base 527 of the loader crane 520. The hydraulic cylinders and the slewing drive(s) are exemplary hydraulic actuators, hydraulically coupled to the displacement pump 125 of the loader crane 520 and form the hydraulic system of the loader crane 520. The hydraulic cylinders and the slewing drive(s) are drivable (driven) by the displacement pump 125 of the loader crane 520. The displacement pump 125 of the loader crane 520 is driven by the rotary drive 130 on the vehicle 300.

[0079] The vehicle 500 further comprises the apparatus 100 according to the present disclosure for determining a target rotational speed for the rotary drive 130.

[0080] As described above, the rotary drive 130 may be mounted on (to) the vehicle 500. For example, the rotary drive may be a PTO of the vehicle 300. The PTO may, e.g., be driven by a combustion engine and optionally a gearbox of the vehicle 500. In alternative examples, the rotary drive 130 may be an ePTO on the vehicle 500. For reasons of simplicity, the rotary drive 130 is illustrated schematically in Fig. 5. Control circuitry 510 on the vehicle 500 is configured to control the rotary drive 130 based on the control data 105 output by the apparatus 100. As described above, the control circuitry 510 may be manifold depending on the type of rotary drive.

[0081] In alternative examples, the rotary drive 130 may be external to the vehicle 500. For example, the rotary drive 130 may be part of an external aggregate or power unit 530 to which the vehicle 500 is mechanically coupleable. Accordingly, the vehicle 500 or the loader crane 520 may be configured to mechanically couple the displacement pump 125 to the external rotary drive 130. For example, the vehicle 500 or the loader crane 520 may comprise one or more of a drive shaft, a hydraulic coupler or clutch, a belt or a chain drive for mechanically coupling the displacement pump 125 to the external rotary drive 130 of the external aggregate or power unit 530.

[0082] In these examples, the vehicle 500 or the loader crane 520 may be configured to output the control data 105 to control circuitry 531 for controlling the rotary drive 130. The control circuitry 531 is part of the external aggregate or power unit 530 and, hence, external to the vehicle 500. For example, the vehicle 500 or the loader crane 520 may comprise interface circuitry (not illustrated in Fig. 1) for wireless or wired transmission of the control data 105 to the control circuitry 531. The control circuitry 531 may control the rotary drive of the external aggregate or power unit 530 based on the control data 105 analogously to what is described above. Accordingly, the vehicle 500 may omit (i.e., not comprise) the control circuitry 510.

[0083] Compared to conventional vehicles, the vehicle 500 may achieve optimized efficiency and, hence, the sustainability of the loader crane 520's hydraulic system. For example, a low-cost, quiet and efficient fixed displacement pump may be used for the displacement pump 125 as the proposed technology allows to mimic the beneficial operational behavior of a variable displacement pump. Similarly, if a variable displacement pump is used for the displacement pump 125, the efficiency of the variable displacement pump may be further improved by the proposed technology. Furthermore, the control of the rotation speed may be adapted to a desired operation strategy for the loader crane 520 via the target value for the pressure difference.

[0084] Fig. 5 focused on the loader crane 520 as an exemplary lifting equipment. However, as indicated above, present disclosure is not limited to the lifting equipment being the loader crane 520 mounted to the vehicle 500. In general, the lifting equipment may be any type of crane using a displacement pump to provide hydraulic power. Apart from a knuckle boom or loader crane for loading and unloading goods (loads), the lifting equipment may, e.g., be the crane section of a mobile crane (with the vehicle being the mobile platform having mounted thereon the crane section) or the entire mobile crane. The lifting equipment may alternatively be a stationary (immobile, fixed) crane. It is to be noted further that the present disclosure is not limited to cranes. In other examples, the lifting equipment may, e.g., be a forklift using a displacement pump to provide hydraulic power for various applications such as raising and lowering its forks or tilting the mast of the forklift to which the forks are mounted. In still other examples, the lifting equipment may, e.g., be a lifting platform using a displacement pump to provide hydraulic power for various applications such as raising and lowering its platform.

[0085] For further highlighting the driving of displacement pumps of lifting equipment described above, Fig. 6 illustrates a flowchart of a method 600 for determining a target rotational speed for a rotary drive driving a displacement pump of a hydraulic system of a lifting equipment. The method 600 comprises receiving 602 input data indicating at least one pressure measurement in the hydraulic system. Further, the method 600 comprises determining 604 the target rotational speed for the rotary drive based on a first value and a second value. The first value represents a pressure difference between a load pressure in the hydraulic system and a pump pressure of the displacement pump. The first value is based on the input data. The second value is a target value for the pressure difference. In addition, the method 600 comprises outputting 606 control data indicating the determined target rotational speed.

[0086] Analogously to what is described above, the method 600 may allow to operate the displacement pump at an optimized level to improve efficiency and, hence, the sustainability of the hydraulic system. For example, the method 600 may allow to mimic the beneficial operational behavior of a variable displacement pump with a low-cost, quiet and efficient fixed displacement pump. Furthermore, precise control over the hydraulic system may be provided as the rotational speed is adjusted based on the at least one pressure measurement in the hydraulic system. Accordingly, (quick) responses to changes in load or operating conditions of the hydraulic equipment are possible. The target value for the pressure difference further allows to adapt the rotational speed control to a desired operation strategy for the lifting equipment.

[0087] More details and aspects of the method 600 are explained in connection with the proposed technique or one or more examples described above (e.g., Fig. 1 to Fig. 5). The method 600 may comprise one or more additional optional features corresponding to one or more aspects of the proposed technique or one or more examples described above.

[0088] The examples described herein may be summarized as follows: In the following, some examples of the proposed concept are presented: An example (e.g., example 1) relates to an apparatus for determining a target rotational speed for a rotary drive driving a displacement pump of a hydraulic system of a lifting equipment. The apparatus comprises processing circuitry configured to receive input data indicating at least one pressure measurement in the hydraulic system. The processing circuitry is further configured to determine the target rotational speed for the rotary drive based on a first value and a second value. The first value represents a pressure difference between a load pressure in the hydraulic system and a pump pressure of the displacement pump. The first value is based on the input data. The second value is a target value for the pressure difference. In addition, the processing circuitry is configured to output control data indicating the determined target rotational speed.

[0089] Another example (e.g., example 2) relates to a previous example (e.g., example 1) or to any other example, wherein the processing circuitry is configured to determine the target rotational speed for the rotary drive based on a difference between the first value and the second value.

[0090] Another example (e.g., example 3) relates to a previous example (e.g., one of the examples 1 or 2) or to any other example, wherein the input data are encoded with at least one measurement value for the load pressure in the hydraulic system and at least one measurement value for the pump pressure of the displacement pump, and wherein the processing circuitry is further configured to determine the first value based on the at least one measurement value for the load pressure in the hydraulic system and the at least one measurement value for the pump pressure of the displacement pump.

[0091] Another example (e.g., example 4) relates to a previous example (e.g., example 3) or to any other example, wherein, prior to determining the first value, the processing circuitry is configured to modify the at least one measurement value for the load pressure in the hydraulic system and / or the at least one measurement value for the pump pressure of the displacement pump by a predefined modification value.

[0092] Another example (e.g., example 5) relates to a previous example (e.g., one of the examples 1 or 2) or to any other example, wherein the input data are encoded with at least one measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump, and wherein the first value is the at least one measurement value for the pressure difference.

[0093] Another example (e.g., example 6) relates to a previous example (e.g., one of the examples 1 or 2) or to any other example, wherein the input data are encoded with at least one measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump, wherein the processing circuitry is configured to modify the at least one measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump by a predefined modification value to obtain at least one modified measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump, and wherein the first value is the at least one modified measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump.

[0094] Another example (e.g., example 7) relates to a previous example (e.g., one of the examples 1 or 2) or to any other example, wherein the input data are encoded with at least one measurement value for the pump pressure of the displacement pump, and wherein the processing circuitry is further configured to determine the first value based on a predefined reference value for the load pressure in the hydraulic system and the at least one measurement value for the pump pressure of the displacement pump.

[0095] Another example (e.g., example 8) relates to a previous example (e.g., one of the examples 1 to 7) or to any other example, wherein the input data are time series data, and wherein the processing circuitry is configured to continuously update the first value based on the input data and to continuously determine the target rotational speed for the rotary drive based on the updated first value.

[0096] Another example (e.g., example 9) relates to a previous example (e.g., one of the examples 1 to 8) or to any other example, wherein the processing circuitry is configured to receive second input data indicating a user input, wherein the user input indicates a user setting for the target value for the pressure difference, and determine the target value for the pressure difference based on the user input.

[0097] Another example (e.g., example 10) relates to a previous example (e.g., one of the examples 1 to 9) or to any other example, wherein the processing circuitry is configured to receive third input data indicating a measured temperature of hydraulic fluid in the hydraulic system, and determine the target value for the pressure difference based on the measured temperature.

[0098] Another example (e.g., example 11) relates to a previous example (e.g., one of the examples 1 to 10) or to any other example, wherein the processing circuitry is configured to receive fourth input data indicating at least one of a status of the lifting equipment and a movement performed by the lifting equipment, and determine the target value for the pressure difference based on the at least one of the status of the lifting equipment and the movement performed by the lifting equipment.

[0099] Another example (e.g., example 12) relates to a previous example (e.g., one of the examples 1 to 11) or to any other example, wherein the displacement pump is a fixed displacement pump.

[0100] Another example (e.g., example 13) relates to a previous example (e.g., one of the examples 1 to 11) or to any other example, wherein the displacement pump is a variable displacement pump.

[0101] Another example (e.g., example 14) relates to a previous example (e.g., one of the examples 1 to 13) or to any other example, wherein the rotary drive is a power take-off of a vehicle, the vehicle having mounted thereon or being the lifting equipment.

[0102] Another example (e.g., example 15) relates to a previous example (e.g., one of the examples 1 to 13) or to any other example, wherein the rotary drive is an electric rotary drive.

[0103] An example (e.g., example 16) relates to a system comprising a lifting equipment and a rotary drive configured to drive a displacement pump of a hydraulic system of the lifting equipment. The system comprises the apparatus according to a previous example (e.g., one of the examples 1 to 15) or to any other example for determining a target rotational speed for the rotary drive. The system further comprises control circuitry configured to control the rotary drive based on the control data. The lifting equipment comprises at least one hydraulic actuator coupled to the displacement pump and drivable by the hydraulic fluid.

[0104] An example (e.g., example 17) relates to a vehicle having mounted thereon or being a lifting equipment. The vehicle comprises the apparatus according to the first aspect. The hydraulic system comprises at least one hydraulic actuator coupled to the displacement pump and drivable by the hydraulic fluid. Control circuitry on the vehicle is configured to control the rotary drive based on the control data. The rotary drive is part of or is mounted to the vehicle. Alternatively, the rotary drive is external to the vehicle and the vehicle is configured to mechanically couple the displacement pump to the external rotary drive. In this case, the vehicle is configured to output the control data to control circuitry for controlling the rotary drive external to the vehicle.

[0105] Another example (e.g., example 18) relates to a previous example (e.g., example 16 or examples 17) or to any other example, wherein the at least one hydraulic actuator is configured to drive at least one of a lifting device of the lifting equipment and an outrigger of the lifting equipment.

[0106] Another example (e.g., example 19) relates to a previous example (e.g., one of examples 16, 17 or 18) or to any other example, wherein the lifting equipment is a loader crane.

[0107] An example (e.g., example 20) relates to a method for determining a target rotational speed for a rotary drive driving a displacement pump of a hydraulic system of a lifting equipment. The method comprises receiving input data indicating at least one pressure measurement in the hydraulic system. Further, the method comprises determining the target rotational speed for the rotary drive based on a first value and a second value. The first value represents a pressure difference between a load pressure in the hydraulic system and a pump pressure of the displacement pump. The first value is based on the input data. The second value is a target value for the pressure difference. In addition, the method comprises outputting control data indicating the determined target rotational speed.

[0108] Another example (e.g., example 21) relates to a non-transitory machine-readable medium having stored thereon a program having a program code for performing the method according to a previous example (e.g., example 20) or to any other example, when the program is executed on a processor or a programmable hardware.

[0109] Another example (e.g., example 22) relates to a program having a program code for performing the method according to a previous example (e.g., example 20) or to any other example, when the program is executed on a processor or a programmable hardware.

[0110] The aspects and features described in relation to a particular one of the previous examples may also be combined with one or more of the further examples to replace an identical or similar feature of that further example or to additionally introduce the features into the further example.

[0111] Examples may further be or relate to a (computer) program including a program code to execute one or more of the above methods when the program is executed on a computer, processor or other programmable hardware component. Thus, steps, operations or processes of different ones of the methods described above may also be executed by programmed computers, processors or other programmable hardware components. Examples may also cover program storage devices, such as digital data storage media, which are machine-, processor- or computer-readable and encode and / or contain machine-executable, processor-executable or computer-executable programs and instructions. Program storage devices may include or be digital storage devices, magnetic storage media such as magnetic disks and magnetic tapes, hard disk drives, or optically readable digital data storage media, for example. Other examples may also include computers, processors, control units, (field) programmable logic arrays ((F)PLAs), (field) programmable gate arrays ((F)PGAs), graphics processor units (GPU), ASICs, integrated circuits (ICs) or system-on-a-chip (SoCs) systems programmed to execute the steps of the methods described above.

[0112] It is further understood that the disclosure of several steps, processes, operations or functions disclosed in the description or claims shall not be construed to imply that these operations are necessarily dependent on the order described, unless explicitly stated in the individual case or necessary for technical reasons. Therefore, the previous description does not limit the execution of several steps or functions to a certain order. Furthermore, in further examples, a single step, function, process or operation may include and / or be broken up into several sub-steps, -functions, -processes or -operations.

[0113] If some aspects have been described in relation to a device or system, these aspects should also be understood as a description of the corresponding method. For example, a block, device or functional aspect of the device or system may correspond to a feature, such as a method step, of the corresponding method. Accordingly, aspects described in relation to a method shall also be understood as a description of a corresponding block, a corresponding element, a property or a functional feature of a corresponding device or a corresponding system.

[0114] The following claims are hereby incorporated in the detailed description, wherein each claim may stand on its own as a separate example. It should also be noted that although in the claims a dependent claim refers to a particular combination with one or more other claims, other examples may also include a combination of the dependent claim with the subject matter of any other dependent or independent claim. Such combinations are hereby explicitly proposed, unless it is stated in the individual case that a particular combination is not intended. Furthermore, features of a claim should also be included for any other independent claim, even if that claim is not directly defined as dependent on that other independent claim.

Claims

1. An apparatus (100) for determining a target rotational speed for a rotary drive (130) driving a displacement pump (125) of a hydraulic system of a lifting equipment (120), the apparatus (100) comprising processing circuitry (110) configured to: receive input data (101) indicating at least one pressure measurement in the hydraulic system; determine the target rotational speed for the rotary drive (130) based on a first value and a second value, wherein the first value represents a pressure difference between a load pressure in the hydraulic system and a pump pressure of the displacement pump (125), wherein the first value is based on the input data (101), and wherein the second value is a target value for the pressure difference; and output control data (105) indicating the determined target rotational speed.

2. The apparatus (100) of claim 1, wherein the processing circuitry (110) is configured to determine the target rotational speed for the rotary drive (130) based on a difference between the first value and the second value.

3. The apparatus (100) of claim 1 or claim 2, wherein the input data (101) are encoded with at least one measurement value for the load pressure in the hydraulic system and at least one measurement value for the pump pressure of the displacement pump (125), and wherein the processing circuitry (110) is further configured to determine the first value based on the at least one measurement value for the load pressure in the hydraulic system and the at least one measurement value for the pump pressure of the displacement pump (125).

4. The apparatus (100) of claim 3, wherein, prior to determining the first value, the processing circuitry (110) is configured to modify the at least one measurement value for the load pressure in the hydraulic system and / or the at least one measurement value for the pump pressure of the displacement pump (125) by a predefined modification value.

5. The apparatus (100) of claim 1 or claim 2, wherein the input data (101) are encoded with at least one measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump (125), and wherein the first value is the at least one measurement value for the pressure difference.

6. The apparatus (100) of claim 1 or claim 2, wherein the input data (101) are encoded with at least one measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump (125), wherein the processing circuitry (110) is configured to modify the at least one measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump (125) by a predefined modification value to obtain at least one modified measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump (125), and wherein the first value is the at least one modified measurement value for the pressure difference between the load pressure in the hydraulic system and the pump pressure of the displacement pump (125).

7. The apparatus (100) of claim 1 or claim 2, wherein the input data (101) are encoded with at least one measurement value for the pump pressure of the displacement pump (125), and wherein the processing circuitry (110) is further configured to determine the first value based on a predefined reference value for the load pressure in the hydraulic system and the at least one measurement value for the pump pressure of the displacement pump (125).

8. The apparatus (100) of any one of claims 1 to 7, wherein the input data (101) are time series data, and wherein the processing circuitry (110) is configured to continuously update the first value based on the input data (101) and to continuously determine the target rotational speed for the rotary drive (130) based on the updated first value.

9. The apparatus (100) of any one of claims 1 to 8, wherein the processing circuitry (110) is configured to: receive second input data (102) indicating a user input, wherein the user input indicates a user setting for the target value for the pressure difference; and determine the target value for the pressure difference based on the user input.

10. The apparatus (100) of any one of claims 1 to 9, wherein the processing circuitry (110) is configured to: receive third input data (103) indicating a measured temperature of hydraulic fluid in the hydraulic system; and determine the target value for the pressure difference based on the measured temperature.

11. The apparatus (100) of any one of claims 1 to 10, wherein the processing circuitry (110) is configured to: receive fourth input data (104) indicating at least one of a status of the lifting equipment (120) and a movement performed by the lifting equipment (120); and determine the target value for the pressure difference based on the at least one of the status of the lifting equipment (120) and the movement performed by the lifting equipment (120).

12. The apparatus (100) of any one of claims 1 to 11, wherein the displacement pump (125) is a fixed displacement pump.

13. The apparatus (100) of any one of claims 1 to 11, wherein the displacement pump (125) is a variable displacement pump.

14. A system (400) comprising: a lifting equipment (410); a rotary drive (420) configured to drive a displacement pump (411) of a hydraulic system of the lifting equipment (410); the apparatus (100) according to any one of claims 1 to 13 for determining a target rotational speed for the rotary drive (420); and control circuitry (430) configured to control the rotary drive (420) based on the control data (105), wherein the hydraulic system comprises at least one hydraulic actuator (412) coupled to the displacement pump (411) and drivable by the hydraulic fluid.

15. A vehicle (500) having mounted thereon or being a lifting equipment (520), wherein the vehicle (500) comprises the apparatus (100) according to any one of claims 1 to 13, wherein the hydraulic system comprises at least one hydraulic actuator (521, 522, 523, 525, 528) coupled to the displacement pump (125) and drivable by the hydraulic fluid, and wherein: control circuitry on the vehicle (500) is configured to control the rotary drive (130) based on the control data (105), the rotary drive (130) being part of or being mounted to the vehicle (500); or the rotary drive (130) is external to the vehicle (500), the vehicle (500) is configured to mechanically couple the displacement pump (125) to the external rotary drive (130), and the vehicle (500) is configured to output the control data (105) to control circuitry (531) for controlling the rotary drive (130) external to the vehicle (500).

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