Method for identifying load data

Abstract

The present invention relates to a method for identifying load data of a load acting on a drive train of a machine, wherein the load data are identified by means of computing data in a computer unit, wherein the computing data are generated by power electronics of the drive train and / or are transmitted to the computer unit by the power electronics.

Description

[0001] Method for determining load data

[0002] The present invention relates to a method for determining load data of a load acting on a drive train of a machine, wherein the load data is determined by means of calculation data in a calculation unit.

[0003] It is known from the state of the art, for example, to determine the mass or weight of an object lifted by a construction machine using calculations to limit the load moment of the construction machine. The load moment is calculated based on the machine's geometric data and measured values ​​from force measuring tabs in the support structure, e.g., in the support rods of a cable excavator. From these calculations, the mass or weight of the object can be determined, among other things.

[0004] Fig. 6 shows an example of a state-of-the-art cable excavator (SB). The data obtained from the force measuring lugs (KM) in the support rods of the SB cable excavator are used to calculate the load moment of the cable excavator, from which the mass or weight of the object is derived according to the state of the art.

[0005] The prior art method for calculating the mass or weight of an object is complex and error-prone, for example, due to the necessary sensors, such as force-measuring tabs. Against this background, the present invention seeks to provide the above-mentioned method in an advantageous manner, particularly with regard to its simplicity and robustness.

[0006] This object is achieved by the method having the features of independent claim 1. Advantageous developments of the invention are the subject of the dependent claims.

[0007] Accordingly, the invention provides that the calculation data are generated by power electronics of the drive train and / or transmitted from the power electronics to the computing unit.

[0008] The load preferably comprises a force and / or a torque. Load data preferably comprises force and / or torque values. The load acting on the drive train is caused, for example, by an object that is to be lifted and preferably also includes mechanical and electrical effects, such as friction and magnetic reversal in the drive train components.

[0009] The determination of the load data preferably includes a calculation and / or estimation of the load data.

[0010] The generation of the calculation data preferably comprises a measurement and / or calculation of the calculation data.

[0011] The term "load and / or calculation data" is preferably to be understood broadly, so that load and / or calculation data can be understood as a quantity or value, but also as a range of quantities and / or values ​​that includes multiple quantities and / or values. The drive train is preferably an electrical or electromechanical drive train and preferably comprises at least one electrical machine, in particular an electric motor. The power electronics are preferably designed to supply the electrical machine with electrical power and / or signals. The power electronics can also be connected to the electrical machine in a single unit.

[0012] The computing unit can be part of a machine control system.

[0013] The load can act on the drivetrain during stationary or dynamic operation of the drivetrain.

[0014] Preferably, the calculation data comprise an electrical state variable, a measurement and / or control variable, a rotational speed and / or a torque estimate.

[0015] Preferably, the load data comprise a property of the load, in particular a mass, a weight, a cross-sectional size in the drive train and / or the machine, a turnover, a turnover forecast and / or a machine parameter.

[0016] In other words, it is preferably provided to determine load data from electrical state variables and / or measured and / or controlled variables provided by power electronics. Load data is relevant, for example, for the handling calculation of a machine. The handling calculation of a machine requires, in the example of a cable excavator, the current load of a receiving device, such as a hook, of the machine. In this way, for example, the current handling quantity as well as forecasts etc. can be determined, calculated and / or displayed. It is also conceivable that the method can be used to determine resistance forces in an electric drilling drive, on the basis of which resistance forces, for example, can be analyzed. It is preferably provided that the power electronics comprise or represent a power converter, preferably an inverter.

[0017] The inverter can also be called an inverter. The power electronics can also be a converter or include one.

[0018] Preferably, the computing data is transmitted from the power electronics to the computing unit via a bus system and / or wirelessly or wired.

[0019] It is preferably provided that the load data is determined by means of a calculation model which is preferably adapted to the drive train and / or the machine.

[0020] Preferably, it is provided that forces and / or moments within the drive train and / or the machine are calculated by means of the calculation model.

[0021] Cutting forces of mechanical components of the drive train can also be analyzed.

[0022] The method preferably uses electrical measurement and / or control variables from the power electronics as input parameters. These are preferably communicated via a bus system, such as a Controller Area Network (CAN) bus, to the computing unit, which may, for example, be part of a machine control system or may consist of a machine control system. These are then converted into load data in a calculation model adapted to the drive train and / or the machine.

[0023] The method is preferably not limited to one, especially specific, winch arrangement. It is conceivable that computational data in the form of measured values ​​from internal sensors of the power electronics, which are communicated via CAN messages to the machine control system as the computing unit, could be used to calculate or determine load data.

[0024] Preferably, alternatively or additionally, for parameterized combinations of electric machine and power electronics, calculation data in the form of the instantaneous torque estimate from the power electronics can be communicated or transmitted directly to the machine control system as a computing unit using Id / Iq tables. Using a calculation model adapted to the drive train and / or the machine, this basic information can be used to make statements about the load, e.g., the mass of an object on the hook of a machine.

[0025] Preferably, it is provided that no sensors are used, in particular outside the power electronics, and / or that the calculation data do not include any speed, torque, current and / or voltage data measured by sensors outside the power electronics.

[0026] It is conceivable that a speed sensor that records speed data from an electrical machine is located both outside the power electronics and inside the electrical machine. The electrical machine, for example, has a resolver or encoder. However, the evaluation unit or evaluation electronics for the resolver or encoder is located inside the power electronics. Therefore, the speed of the electrical machine is communicated via the power electronics.

[0027] Preferably, the power electronics, through its internal sensors and / or control and / or regulation algorithms, provide information that can be used to calculate further system parameters.

[0028] The method preferably does not use sensors separate from the power electronics. Preferably, the load data is determined at least partially using a state estimator, machine learning, a calibration process, models, and / or algorithms. In particular, internal forces can be determined using a state estimator.

[0029] Preferably, mathematical methods, particularly from the field of machine learning, are used in the process to take into account the dynamic effects when determining the load data.

[0030] Preferably, the calculation data and / or load data are displayed to a user.

[0031] Preferably, it is provided that computing data from the power electronics communicated via a bus system serves as the basis data for the calculation. In the method, preferably, no direct current measurement of the phases of the electric machine is carried out and / or no resolver and / or encoder data of the electric machine are evaluated directly in the computing unit and / or when determining the load data for determining the speed.

[0032] Preferably, forces and / or moments within the drive train and / or the machine can be calculated using the calculation model adapted to the drive train and / or the machine.

[0033] The method preferably offers a cost-effective, software-based method for determining or capturing load data from drivetrain components. Load data is relevant, for example, for calculating the load envelope or the load torque of a machine. The internal forces along the drivetrain determined or calculated using the method preferably enable in-depth analyses of the load on subsystems and components that were previously impossible. The method preferably uses calculation data provided by the power electronics as standard. Thus, the method is preferably universally applicable and requires no additional measurement technology and / or hardware.

[0034] Preferably, a calculation model adapted to the drive train and / or machine is used to determine or determine the load data. This method preferably also allows any internal forces to be calculated within the calculation model. For example, cable forces can be determined and service life forecasts derived.

[0035] The invention also relates to a system having a drive train of a machine and a computing unit, wherein the drive train comprises power electronics, wherein the drive train, the power electronics and / or the computing unit are designed to carry out a method according to the invention.

[0036] Preferably, the computing unit is arranged on or in the machine or separately from the power electronics and / or from the machine, preferably in a cloud.

[0037] The load data is preferably not calculated directly on the power electronics. Computational data from the power electronics is preferably used and transmitted to a computing unit, where the load data serves as the basis for determining the load data. The load data is preferably transmitted wirelessly or wired to a computing unit on the machine and / or to a computing unit separate from the machine. This has the advantage that the method is preferably independent of the hardware configuration used.

[0038] Preferably, the drive train comprises a winch, a boom, a drilling machine, a slewing gear and / or a chassis.

[0039] Preferably, the machine is a construction machine, in particular a crane or cable excavator. The machine preferably has one or more drive trains. An exemplary electric drive train comprises, as main components, power electronics, in particular an inverter that converts the direct current voltage of the direct current intermediate circuit into an alternating current voltage, an electric machine that converts electrical energy into mechanical energy, and an object to be moved that causes a load. Such a drive train can be used, for example, to drive a winch, e.g., a crane winch, a chassis, e.g., a crawler chassis, and / or a slewing gear.

[0040] The invention also relates to a computer program product comprising instructions which cause the system according to the invention to carry out the method according to the invention.

[0041] The invention also relates to a computer-readable medium on which the computer program product according to the invention is stored.

[0042] The invention preferably provides the following advantages and / or solutions.

[0043] The method preferably uses standard functions or standard data from power electronics, which are preferably manufacturer-independent. The method can therefore be used with different hardware configurations.

[0044] The computational data is preferably communicated via a bus system and is thus available to the machine control system or a computing unit on or off the machine, such as in a cloud. The method can preferably be parameterized system-specifically. Thus, it can preferably be used for various drive trains. For example, the drive train can include a drilling machine, a winch, a slewing gear, and / or a chassis.

[0045] The process is preferably independent of the current machine geometry, e.g. the boom and / or A-frame angle.

[0046] The method is preferably software-based; preferably, no additional hardware components are required.

[0047] The load data can preferably supplement existing load data or be used as redundancy to existing load moment limitation data.

[0048] The method preferably allows for the calculation of internal forces within the drive train and / or the calculation model, thus analyzing loads on components. This allows, for example, lifetime estimates to be performed.

[0049] The method preferably enables deeper system knowledge, since current electrical and mechanical parameters of the powertrain can be determined.

[0050] At this point, it should be noted that the terms "a" and "an" do not necessarily refer to exactly one of the elements, although this represents a possible embodiment, but can also refer to a plurality of the elements. Likewise, the use of the plural also includes the presence of the element in question in the singular, and conversely, the singular also encompasses several of the elements in question. Furthermore, all features of the invention described herein can be combined with one another as desired or claimed in isolation from one another. Further advantages, features, and effects of the present invention will become apparent from the following description of preferred embodiments with reference to the figures, in which identical or similar components are designated by the same reference numerals. Herein:

[0051] Fig. 1 : a schematic representation of an embodiment of a system according to the invention.

[0052] Fig. 2: a schematic representation of a calculation model adapted to a drive train of a system according to the invention.

[0053] Fig. 3: a schematic representation of a calculation model with cross-sectional forces adapted to a drive train of a system according to the invention.

[0054] Fig. 4: a schematic representation of a calculation model adapted to a drive train of a system according to the invention.

[0055] Fig. 5: a schematic representation of a calculation model with cross-sectional forces adapted to a drive train of a system according to the invention.

[0056] Fig. 6: a perspective view of a rope excavator from the state of the art.

[0057] Fig. 1 shows an electric drive train with power electronics 10, an electrical energy source 20 connected thereto, and an electrical machine 30 connected to the power electronics 10. The power electronics 10 can be connected to the energy source 20 via an intermediate circuit of the machine. The energy source 20 can be an electrical energy storage device. The intermediate circuit can have an electrical energy storage device and a plurality of electrical energy sources 20. A load 40 acts on the drive train. The load 40 is shown abstractly in Fig. 1 and is caused by at least one mechanical component.

[0058] Calculation data from the power electronics 10 in the form of current data 11, a torque estimate 12, in particular a torque of the electric machine 30, and a rotational speed 13, in particular of the electric machine 30, are transmitted to a computing unit 50. The computing unit 50 has a parameterized calculation model implemented therein that is adapted to the drive train and / or the machine. Load data is determined in this calculation model.

[0059] The computing unit 50 is preferably part of a load detection unit 51 and / or a machine control 52.

[0060] In other words, it is preferably provided to determine load data of a drive train from electrical state variables and from measurement and / or control variables provided by power electronics 10. Load data to be determined can be, for example, the mass of an object on a crane hook, the resistance forces of a crawler chassis, or a rotary drilling drive.

[0061] The method preferably uses data from power electronics 10 to calculate load data for a load on a computing unit 50 using a calculation model adapted to the drive train and / or the machine. In the example of the winch drive train, a load datum for the load is the mass of an object.

[0062] The power electronics 10 can provide electrical state variables in the form of currents and / or voltages, in particular from the direct current and / or alternating current side of the power electronics 10, as well as internal calculation and variables of the electrical machine 30, such as torque, speed, etc., via a communication interface.

[0063] The calculation model adapted to the drive train and / or the machine is shown in Fig. 2. The elements sketched in the figures between the shaft of the electric machine 30 and object 46 are to be considered as examples. All possible system configurations are conceivable. In addition to a winch drive, it can also be a travel drive, drilling drive, or the like. The electric machine 30 can be a permanent-magnet synchronous machine or an asynchronous machine, etc. Load data are preferably determined or ascertained from electrical state variables and measurement and / or control variables available from power electronics 10 using a calculation model adapted to the drive train and / or the machine.

[0064] In other words, Fig. 2 shows an analytical powertrain model as a basis for calculating load data.

[0065] In Fig. 2, the load is caused by the entire mechanism between the rotor shaft of the electric machine 30 and an object 46 on the hook. The mechanism in Fig. 2 includes a brake 41, a free-fall brake 42, a gear 43, a winch drum 44, a cable pulley 45, and an object 46 on the cable, which runs between the winch drum 44 and the cable pulley 45. The brake 41 is not a service brake, but rather a holding brake. The functionality of the brake 41 is limited to holding the load when stationary and in emergency situations.

[0066] This calculation model makes it possible to calculate forces F within the winch drive train. These forces F are shown as an example in Fig. 3.

[0067] The rotor of the electric machine 30 acts on a gearbox 43 via a shaft. The gearbox 43 also includes brakes 41 to decelerate the movement of the object 46. The gearbox output shaft drives a winch drum 44, which winds up or unwinds a cable and thus raises or lowers an object 46. When calculating the load data, cutting forces within the drive train can also be calculated. For example, the forces in the cable as well as on the cable and pulleys. The calculation data required for determining and / or calculating the load data and communicated from a power electronics unit 10 to the computing unit 50 can differ depending on the parameterization of the electric machine 30 and / or the power electronics unit 10.

[0068] In a first example, the power electronics 10 is only partially parameterized to the electric drive or adapted to the electric machine 30.

[0069] Due to the internal controllers, the power electronics 10 preferably has, among other things, sensors for current measurement. This provides the instantaneous electrical state variables, such as the output current of the power electronics 10, or more precisely, the two-dimensional current variables Id and Iq of the field-oriented control. These variables can be communicated as a message via a bus system to the computing unit 50 and / or to the calculation model implemented therein. In the first example, the theoretical electrical torque is determined from the current variables Id and Iq as well as the machine-specific inductances, magnetic fluxes, and rotor inertia.

[0070] In the first example, only the rotational speed 13 and current data 11 in the form of output currents of the power electronics from Fig. 1 are transmitted to the computing unit as computational data. In the first example, the torque estimate 12 from Fig. 1 is not transmitted.

[0071] In a second example, the power electronics 10 are specifically parameterized for the electric drive or adapted to the electric machine 30.

[0072] The second example refers to combinations of electric machine 30 and power electronics 10, which are explicitly parameterized or coordinated with each other.

[0073] In the second example, only the torque estimate 12 and the rotational speed 13 of the electric machine 30 are transmitted from the power electronics 10 to the computing unit 50. In the second example, the current data 11 are not transmitted. In the second example, a simplified calculation of the load data is possible compared to the first example, since the electrical torque of the electric machine 30 and all associated current control, magnetization, and / or loss effects for stationary operating points are not taken into account.

[0074] Fig. 4 shows an example of a winch drive train. From left to right, the elements visible are the object 46, cable pulley 45, winch drum 44, holding and free-fall brake 41, gearbox 43 with free-fall brake 42, the electric motor 30, the power electronics 10, and the on-board electrical system or energy source 20. The mechanical components between the winch drum 44 and the electric motor 30 are connected via shafts, which are also sketched.

[0075] Fig. 5 shows an exemplary representation of forces in the exemplary winch drive train from Fig. 4. The rotor of the electric machine 30 acts via a shaft on a gearbox 43 with a free-fall brake 42. The gearbox 43 also includes brakes 41 to decelerate the movement of the object 46. The gearbox output shaft drives a winch drum 44, which winds up or unwinds a cable S and thus raises or lowers an object 46. When calculating the load data, cutting forces within the drive train can also be calculated, such as forces F in the cable S and / or on cable and deflection pulleys 45.

[0076] The method for determining load data can be performed during a lifting movement of an object 46. The winch drum 44 is driven by a permanent magnet synchronous machine controlled by power electronics 10. The calculation data is transmitted by power electronics 10 via CAN messages.

[0077] In the first example, the parameters Id and Iq and the rotational speed 13 of the electric machine 30 are communicated to the machine's computing unit 50. Using these variables, the mass of the object 46 on the hook can be calculated. This calculation is an analytical consideration that neglects, for example, current controller effects, magnetization reversal effects, and temperature- and speed-dependent friction conditions of the system. These analytical neglects are preferably taken into account with correction methods to increase the accuracy of the load data.

[0078] Cutting forces can also be calculated at any point in the calculation model.

[0079] In addition to analytical calculation methods, correction methods can be used to improve the quality of the results. The analytical approach does not fully account for all dynamic processes. Influencing factors occur that are preferentially considered to ensure precise determination of the load data under both steady-state and transient operating conditions. Examples of influencing factors include speed- and / or temperature-dependent losses due to changing friction conditions in gears, magnetization reversal processes in electrical machines 30 during flux changes, and / or current controller properties in power electronics 10.

[0080] Such disturbance effects can be minimized using the following correction methods: A state estimator, such as a Kalman filter, can be used. Methods from the field of machine learning can be employed. Calibration processes can be used to determine friction and loss processes in a powertrain. Models and / or algorithms can be used to calculate electrical and / or magnetic storage processes that cannot be exploited mechanically.

[0081] A further aspect of the present invention is that the electrification of construction machinery is increasing the number of drive components with integrated control systems. These components usually have one or more bus systems. The CAN bus is typically used in the field of mobile drive technology. Values ​​measured or calculated by the component itself can be sent to a higher-level machine control system via the CAN bus. This offers the possibility of analyzing system parameters of these components during operation with the machine control system. On the higher-level machine control system, these parameters can serve as the basis for calculating additional machine parameters or for direct customer benefit.

Claims

Patent claims 1. A method for determining load data of a load acting on a drive train of a machine, wherein the load data is determined by means of calculation data in a calculation unit, characterized in that the calculation data are generated by power electronics of the drive train and / or are transmitted from the power electronics to the calculation unit.

2. Method according to claim 1, characterized in that the calculation data comprise an electrical state variable, a measurement and / or control variable, a speed and / or a torque estimate.

3. Method according to claim 1 or 2, characterized in that the load data comprise a property of the load, in particular a mass, a weight, a cross-sectional size in the drive train and / or the machine, a turnover, a turnover forecast and / or a machine parameter.

4. Method according to one of the preceding claims, characterized in that the power electronics comprises or represents a power converter, preferably an inverter.

5. Method according to one of the preceding claims, characterized in that the computing data are transmitted from the power electronics to the computing unit via a bus system and / or wirelessly or wired.

6. Method according to one of the preceding claims, characterized in that the load data are determined by means of a calculation model which is preferably adapted to the drive train and / or the machine.

7. Method according to claim 6, characterized in that forces and / or moments within the drive train and / or the machine are calculated by means of the calculation model.

8. Method according to one of the preceding claims, characterized in that no sensors, in particular outside the power electronics and / or an electrical machine, are used and / or that the calculation data do not include any speed, torque, current and / or voltage data measured by sensors outside the power electronics and / or the electrical machine.

9. Method according to one of the preceding claims, characterized in that the load data is determined at least partially by means of a state estimator, machine learning, a calibration process, models and / or algorithms.

10. Method according to one of the preceding claims, characterized in that the calculation data and / or load data are displayed to a user.

11. System with a drive train of a machine and a computing unit, wherein the drive train comprises power electronics, wherein the drive train, the power electronics and / or the computing unit are designed to carry out a method according to one of the preceding claims.

12. System according to claim 10, characterized in that the computing unit is arranged on or in the machine or separately from the power electronics and / or from the machine, preferably in a cloud.

13. System according to claim 10 or 11, characterized in that the drive train comprises a winch, a boom, a drilling machine, a slewing gear and / or a chassis.

14. System according to one of claims 10 to 12, characterized in that the machine is a construction machine, in particular a crane or cable excavator.

15. A computer program product comprising instructions that cause the system according to any one of claims 10 to 13 to carry out the method according to any one of claims 1 to 9.

16. A computer-readable medium on which the computer program product according to claim 14 is stored.

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