Method and system for calibrating a control device of an electric motor

Description

[0001] The invention relates to a method for calibrating a control device, in particular an inverter control device, of an electric motor, in particular a three-phase motor, in which the electric motor is operated as part of a power flow and force measurements are carried out using piezo elements, wherein the piezo elements are arranged in the power flow such that the power flow is applied, in particular exclusively, to the piezo elements. Furthermore, the invention relates to a method for regulating an electric motor, in particular a three-phase motor, wherein the electric motor is operated as part of a power flow and a force measurement is carried out using piezo elements which are arranged in the power flow such that the power flow is applied, in particular exclusively, to the piezo elements. Furthermore, the invention relates to systems for carrying out the aforementioned methods.

[0002] It is known from the prior art to use power devices for operating electric motors which can generate a variable voltage system, such as direct current, alternating current or three-phase current, from a fixed voltage system, such as a power grid or a battery.

[0003] Especially for three-phase motors, it is necessary to transform the DC voltage from the power supply into an AC voltage suitable for the power requirements. Therefore, so-called inverter controllers are generally used to control electric motors; see DE 10 2014 213446 A1.

[0004] Furthermore, it is known from the prior art to measure forces or torques on a shaft using a measuring flange with piezo elements, or to determine the forces or torques on a shaft via reaction forces acting between a bearing device of the shaft and a support device of the bearing device, wherein the bearing device is formed in particular by an electric machine. This is described, for example, in document WO 2019 / 144172 A1. Furthermore, document WO 2019 / 144171 A1 discloses determining torque components based on a system of equations of force measurements from various piezo elements.

[0005] Based on this prior art, it is an object of the invention to provide an improved method and system for calibrating a control device of an electric motor and an improved method and system for controlling an electric motor.

[0006] This object is achieved by the methods and systems according to the independent claims. Advantageous embodiments are defined in the subclaims.

[0007] A first aspect of the invention relates to a method for calibrating a control device, in particular an inverter control device, of an electric motor, comprising the following steps: Operating the electric motor as part of a force flow; performing a force measurement by means of piezo elements arranged in the force flow such that the force flow is applied, in particular exclusively, to the piezo elements; and adapting a control characteristic of the control device based on at least one force component derived from the force measurement, in particular a change in the at least one force component and / or at least one torque component derived from the force measurement, in particular a change in the torque component.

[0008] Preferably, the electric motor has or interacts with a shaft that transmits a power flow from or to the electric motor. Furthermore, the method is preferably computer-aided.

[0009] A second aspect of the invention relates to a method for controlling an electric motor, in particular a three-phase motor, comprising the following steps: Operating the electric motor as part of a force flow; performing a force measurement by means of piezo elements arranged in the force flow such that the force flow is applied, in particular exclusively, to the piezo elements; and adjusting at least one control parameter of the electric machine on the basis of at least one force component derived from the force measurement, in particular a change in at least one force component, and / or at least one torque component derived from the force measurement, in particular a change in the torque component.

[0010] Preferably, the electric motor has a shaft or interacts with a shaft that transmits a power flow from or to the electric motor. Further preferably, the method is computer-aided.

[0011] A third aspect of the invention relates to a system for calibrating a control device, in particular an inverter control device, of an electric motor, in particular a three-phase motor, which is part of a power flow. The system preferably comprises: Piezo elements for performing a force measurement, wherein the piezo elements are arranged in the force flow in such a way that the force flow is applied, in particular exclusively, to the piezo elements; evaluation means configured to evaluate at least one force component, in particular a change in the at least one force component, and / or at least one torque component, in particular a change in the at least one torque component, from the force measurement; and means configured to adapt a control characteristic of the control device on the basis of the at least one force component derived from the force measurement and / or the at least one torque component derived from the force measurement.

[0012] Preferably, the electric motor has a shaft or interacts with a shaft which transmits a power flow from or to the electric motor.

[0013] A fourth aspect of the invention relates to a system for controlling an electric motor, in particular a three-phase motor, which is part of a power flow, comprising: Piezo elements configured to perform a force measurement, wherein the piezo elements are arranged in the force flow in such a way that the force flow is applied, in particular exclusively, to the piezo elements; evaluation means configured to derive at least one force component, in particular a change in the at least one force component, and / or at least one torque component, in particular a change in the at least one torque component, from the force measurement; and control means configured to adjust at least one control parameter of the electric machine on the basis of the at least one force component derived from the force measurement and / or the at least one torque component derived from the force measurement.

[0014] Preferably, the electric motor has a shaft or interacts with a shaft which transmits a power flow from the electric motor or to the electric motor.

[0015] A fifth aspect of the invention relates to a test bench for an electric motor, wherein the test bench has a support device and a device for applying a load, in particular a dynamometer, and the electric motor can be arranged in a force flow between the support device and the load of the test bench, wherein the test bench further has a system for calibrating a control device of an electric motor.

[0016] A force flow within the meaning of the invention is preferably a path of a force and / or a torque in a mechanical system from a point of application, in particular a point of introduction, to one or more points at which the force and / or torque is absorbed by a reaction force and / or a reaction moment. The force flow is preferably composed of a force, in particular a transverse force relative to the direction of rotation of the shaft, and / or a torque, in particular about the axis of rotation.

[0017] A power flow in the sense of the invention is preferably a path of transmission of power in a mechanical system from a point of introduction to one or more points at which the power is taken off.

[0018] A piezoelectric element within the meaning of the invention is preferably a measuring element configured to measure a force acting across two surfaces adjacent to the piezoelectric element. A piezoelectric element preferably consists of the piezoelectric crystal and a charge dissipation device or an electrical circuit.

[0019] An electric motor in the sense of the invention is preferably an electromechanical energy converter which preferably converts kinetic energy, in particular rotation, into electrical energy or vice versa, from electrical energy into kinetic energy.

[0020] Calibration within the meaning of the invention preferably involves applying control data to a control device. Calibration is preferably used when tuning and / or optimizing the control of an electric motor.

[0021] A means within the meaning of the invention can be designed in hardware and / or software and in particular can have a processing unit, in particular a microprocessor unit (CPU), which is preferably connected to a memory and / or bus system in terms of data or signals, and / or one or more programs or program modules. The CPU can be designed to process instructions implemented as a program stored in a memory system, to detect input signals from a data bus and / or to output output signals to a data bus. A memory system can have one or more, in particular different, storage media, in particular optical, magnetic, solid-state and / or other non-volatile media. The program can be designed in such a way that it embodies the methods described here orcapable of performing such processes, so that the CPU can perform the steps of such processes and thus, in particular, calibrate or control an electric motor.

[0022] A control characteristic within the meaning of the invention is preferably the manner in which a control device controls or regulates the electric motor. The control characteristic is preferably defined by a computer program stored in a data memory of the control device, which implements an assignment rule. The assignment rule can be stored as an assignment function or as a table. Furthermore, the control characteristic is preferably influenced by controllers of a controlled system.

[0023] Most inverter control systems for electric motors automatically calibrate the inverter control system by measuring current and voltage after initial installation. This procedure is simple, but often produces unsatisfactory results. Manual calibration, on the other hand, improves performance by 10 to 20%, especially under special conditions such as low battery charge.

[0024] In a conventional manual calibration, the effective torque is measured at a variety of operating points under specific boundary conditions, and a control characteristic is adjusted. The problem is that it takes a long time, up to several weeks, to complete such a manual calibration procedure. Furthermore, the only measured effect of a changed inverter control setting is effective torque. Dynamic torque modes, which are particularly responsible for efficiency losses, cannot be detected.

[0025] The invention pursues the approach of improving calibration and thus also control of the electric motor by taking into account a force measurement carried out by means of piezo elements when creating or adjusting a control characteristic or even when setting control parameters.

[0026] By measuring the force using piezo elements, the dynamics of a force component or torque component can be determined. In particular, torque ripple and / or cogging torque can be determined in this way and taken into account in the control characteristics of the control device or directly when the control device regulates the electric motor.

[0027] Because the piezo elements are arranged directly in the force flow between the electric motor and a device for applying a load, in particular a dynamometer, or its holding device, the measurements are not limited to specific operating points. Rather, force measurements can be taken at all operating points throughout the entire operation of the electric motor. Furthermore, the calibration and control methods are not limited to test bench applications. Rather, the piezo elements used to measure force can also be arranged directly in a drive train in which the electric motor is installed, for example, in a vehicle. This allows the force measurement to be continuously used to control the electric motor.

[0028] In particular, the method according to the invention can be used to automatically calibrate and optimize a control device of an electric motor. High accuracy in measuring the dynamic response and vibration measurements can be achieved. Furthermore, by optimizing with respect to these two criteria, a significant improvement in the control of an electric motor can be achieved. In particular, torque ripples and energy losses, for example due to waste heat, can be reduced, in particular to a minimum of energy losses, which can be achieved by adjusting the control unit without hardware adjustments.

[0029] The features and advantages of the advantageous embodiments described below with respect to the methods of the first aspect and the second aspect of the invention also apply accordingly to the other aspects of the invention and vice versa.

[0030] In an advantageous embodiment of the method, the electric motor is a three-phase synchronous machine or a three-phase asynchronous machine and the control characteristic is determined by a P component and / or an I component of a PI controller or a PID controller of at least one control parameter.

[0031] In a further advantageous embodiment of the method, the electric motor is a three-phase synchronous machine, and the at least one control parameter is a rotor current, in particular its longitudinal component and quadrature component in the complex phasor diagram. This is particularly advantageous because the quadrature component of the rotor current is responsible for torque generation. Torque ripples generated by the electric motor or cogging torques can be particularly compensated for in this way.

[0032] In a further advantageous embodiment, the electric motor is a three-phase asynchronous machine, and the at least one control parameter is a stator voltage and / or a stationary frequency, or the at least one control parameter is a stator current and / or a stator frequency. This also allows for particularly effective compensation of harmful effects caused by the design of an electric motor, such as torque ripple and / or cogging torque.

[0033] In a further advantageous embodiment, at least one criterion for adapting a control characteristic or setting at least one control parameter is selected from the following group: an intensity of a harmonic oscillation of change in torque and / or force; and / or an integral of the intensity of oscillations of change in torque and / or force over a given frequency spectrum.

[0034] Using such criteria in relation to a frequency-resolved vibration analysis, a statement can be made about the vibration behavior of individual frequency ranges or a broad frequency spectrum. Optimization involves reducing the intensity of individual vibrations and / or the integrated vibrations. Such an analysis is preferably performed during stationary operation of the electric motor.

[0035] In a further advantageous embodiment of the method, at least one criterion for adapting a control characteristic or setting at least one control parameter is selected from the following group: a torque rise time from 10% of a torque request to 90% of the torque request; a delay time from a torque request time to the torque rise; and / or an intensity of an overshoot of a value of 100% of a torque request.

[0036] Such criteria relating to a dynamic vibration curve can provide information about the reaction of a drive train to a torque request,

[0037] In particular, its vibration behavior, can be addressed. Optimization reduces the intensity of overshoots, the duration of a delay time, and / or the torque rise time.

[0038] In a further advantageous embodiment of the method, force components and torque components are determined using a system of equations based on measurement signals from the individual piezo elements. Measurement signals from the individual piezo elements are preferably broken down into components that contribute to the respective force components and / or rotational components to be derived. Furthermore, in particular, all contributions from the individual piezoelectric measuring elements to the respective force components and / or torque components to be determined are preferably taken into account. By using a system of equations that is resolved for the respective force components and / or rotational components to be determined, measurements from a large number of piezo elements can be taken into account. Furthermore, all measurements from a multi-component sensor or piezo elements can be proportionally taken into account for the force components and / or rotational components to be determined.In particular, this can reduce or even prevent force shunts via piezo elements not involved in a measurement.

[0039] In a further advantageous embodiment of the method, the electric motor is operated together with a shaft that transmits a force flow from or to the electric motor. The piezo elements are arranged between a first part of the shaft and a second part of the shaft in such a way that a force, in particular a shear force, acting on the first part and the second part can be measured by means of the piezo elements. By measuring directly in or on the shaft, a particularly simple measuring arrangement can be realized.

[0040] In a further advantageous embodiment of the method, the piezo elements measure a force, in particular shear force, between the electric motor and a support device for supporting the electric motor. In this embodiment, the piezo elements are arranged between the electric motor and a support device. Thus, in this embodiment, the force measurement is carried out relative to a spatially fixed reference system, namely a powertrain test bench or its base plate or a vehicle. Piezo elements with a transverse effect, a longitudinal effect, or even a shear effect can be used, depending on how the electric motor is mounted on the support device. Due to this type of arrangement of the force sensor, a rotating mass of the shaft is essentially not changed. In particular, a reaction torque to the torque applied to the shaft is measured.

[0041] In a further advantageous embodiment of the method, the electric motor is operated together with a shaft which transmits a power flow from or to the electric motor, wherein a measuring system comprising the piezo elements does not change a rotating mass of the shaft and / or a rotating mass of rotating parts of an assembly comprising the shaft and the electric motor.

[0042] Preferably, the methods are carried out on a computer. Further aspects of the invention therefore relate to a computer program comprising instructions which, when executed by a computer, cause the computer to perform the steps of the methods, and to a computer-readable medium on which such a computer program is stored.

[0043] Further features and advantages will become apparent from the following description with reference to the figures, which show, at least in part, schematically: Fig. 1 an embodiment of a system for calibrating a control device of an electric motor; Fig. 2 an embodiment of a method for calibrating a control device of an electric motor; Fig. 3 an embodiment of a system for controlling an electric motor; Fig. 4 an embodiment of a method for controlling an electric motor; Fig. 5 a first measuring arrangement with piezo elements of an embodiment of the system for calibrating a control device or the system for controlling an electric motor; Fig. 6 a second measuring arrangement with piezo elements of an embodiment of the system for calibrating a control device or the system for controlling an electric motor; Fig. 7 a third measuring arrangement with piezo elements of an embodiment of the system for calibrating a control device or the system for controlling an electric motor; Fig. 8 a diagram of a frequency spectrum of vibrations of an electric motor, which was determined using the method for calibrating a control device or the method for controlling an electric motor; Fig. 9 another diagram of a frequency spectrum determined using the method for calibrating a control device or the method for controlling an electric motor; and Fig. 10 shows a diagram of a torque over time.

[0044] Fig. 1 shows an entirety of an embodiment of a system 10 for calibrating an inverter control device 1 of an electric motor 2 and the inverter control device 1 to be calibrated as well as the electric motor 2 to be controlled.

[0045] The invention is described below with reference to this inverter control device 1 of a three-phase synchronous machine or three-phase asynchronous machine 2, wherein a rotor current I d , I q or a stator voltage US , stator frequency f S , and stator current IS are used as control parameters. However, the described systems and methods can also be used with respect to other control devices 1 and electric motors 2.

[0046] A control characteristic 5 is stored in the inverter control 1 shown. Using this control characteristic 5, the electric motor is controlled by the control device 1 using control parameters I d , I q , IS , f S , US on the basis of input variables IN1, IN2.

[0047] Input parameters IN1, IN2 are, for example, a torque request, a speed request or the request for a braking torque.

[0048] The system 10 for calibrating the inverter control preferably comprises piezo elements 11a, 11b, 11c, evaluation means 12 and means 13 configured to adapt a control characteristic 5.

[0049] The piezo elements 11a, 11b, 11c are arranged or mounted in a force flow that encompasses the electric motor 2 in such a way that they can measure a change in force or a change in torque that acts on the electric motor 2 or is exerted by it. On the basis of this measurement of various piezo elements 11a, 11b and 11c, the evaluation means 12 can calculate a change in at least one force component and / or one torque component ΔM X , ΔM Y , ΔF Z ; ΔF X , ΔF Y , ΔM Z. In the present description and the figures, the invention is explained purely by way of example with regard to the determination of two torque components ΔM X , ΔM Y and one force component ΔF Z. As a further example, the changes in two force components ΔF X , ΔF Y and one torque component ΔM Z can alternatively also be determined.

[0050] The means 13 for adapting the control characteristic 5 can calibrate the control characteristic 5 based on various criteria, such as NVH-related criteria or dynamics-related criteria. Optimization with respect to these criteria is possible, or even adjustment of the control characteristic, for example, with respect to a specific inverter control 1.

[0051] Fig. 2 shows a block diagram of a method for calibrating a control device 100. Such a method is particularly by means of the Fig. 1 The system 10 shown for calibrating a control device can be executed. The system 10 preferably has means or modules for this purpose, which are implemented in hardware or software.

[0052] In a first work step 101, the electric motor is operated as part of a power flow. The electric motor 2 is controlled by means of the inverter control device 1. For this purpose, the inverter control device 1 generates electrical voltage signals of the control parameters I d , I q ; IS , f S , US on the basis of the input parameters IN1, IN2, which reflect a driver command or a request from a vehicle (not shown). A force measurement is carried out 102 by means of the piezo elements 11a, 11b, 11c. From this force measurement, individual force components and / or torque components ΔM X , ΔM Y , ΔF Z or their change over time can be derived. This change over time contains information about a torque ripple and / or a cogging torque.

[0053] In order to compensate for this torque ripple or cogging torque, the control characteristic 5, which is stored in the inverter control, is adjusted or changed 103 in a further work step 103.

[0054] The System 10 from Fig. 1 is preferably used on a test bench for electric drive trains. The evaluation means 12 and the means 13 for adjusting the control characteristics can be part of the test bench. Data signals are recorded at a defined storage rate, preferably 100 kHz, and subjected to a fast Fourier transform analysis in order to identify vibration intensities as a function of the rotor's rotational frequency.

[0055] Of particular importance is the use of piezo elements 11a, 11b, and 11c as dynamic force and torque sensors. Piezo elements provide sufficient temporal resolution for such dynamic measurements.

[0056] Control characteristic 5 and its variable parameters, in particular the integral action component of a PI controller stored there, are preferably modified in such a way as to optimize the criteria. In the case of NVH-related criteria and dynamics-related criteria as optimization goals, the best compromise must generally be found, as these conflict with each other.

[0057] Preferably, a so-called model-based calibration or optimization procedure is used for the calibration and, if necessary, optimization process.

[0058] A model is designed that represents a relationship between the variable parameters of the control characteristic 5 and the values ​​of the criteria.

[0059] This model can be used, for example, to target those areas in test bench experiments that are particularly promising for optima or compromises between optima.

[0060] An optimization of the control characteristic preferably proceeds as follows: First, a test plan is created for the variable parameters of the inverter control device, in particular a P-component or an I-component, a PI controller of the control parameters I d , I q ; US , IS , f S . Based on this setting of the variable parameters, tests are carried out with the Fig. 1 The overall arrangement shown is carried out. The operating characteristics achieved in the tests, or the individual operating points, are evaluated using criteria. The control characteristics are adjusted based on this evaluation.

[0061] These criteria can be fundamentally divided into NVH-related criteria and dynamic-related criteria.

[0062] For the NVH-related criteria, various harmonics and amplitude analyses of the Fastest Fourier-transformed torque signal, especially its integral, are particularly suitable.

[0063] For dynamic-related criteria, the so-called T90 / T10 rise time is important. This is the time required for the torque to reach 90% of the requested torque when the torque requirement changes from 10%. Other possible criteria are a delay time TD and an overshoot intensity ID , as described in relation to Fig. 10 described below.

[0064] The force components F x ( t ) and F y ( t ) and torque component M z ( t ) and the force component F z ( t ) as well as the torque components M x ( t ) and M y ( t ) can be determined in a manner known per se by means of a targeted arrangement of preferred directions of the individual piezo elements 11a, 11b, 11c and summation of the individual measuring signals S1, S2, S3.

[0065] Other methods for determining these parameters can also be used. For example, a decomposition, in particular orthogonal decomposition, of the measurement signals of the individual piezo elements 11a, 11b, 11c or of the forces F 1 , .., F i derived from the measurement signals, i.e., the measured forces.

[0066] Here, for example, the parameters M z , FX , FY to be determined are the solution of a system of equations, where for each measurement signal an equation applies as follows: S 1 = a 11 · M z + a 12 · Fx + a 13 · Fy S 2 = a 21 · M z + a 22 · Fx + a 23 · Fy S 3 = a 31 · M z + a 32 · Fx + a 33 · Fy ⋮ SN = a N 1 · M z …

[0067] S1, S2,...Si,..., SN are the measurement signals of the individual piezo elements 11a, 11b, 11c,..., 11i,..., 11N. Each coefficient a depends on several factors, such as the respective position of the measuring element 11a, 11b, 11c,..., 11i,..., 11N and the orientation of the respective preferred direction in the reference system, the sensitivity of the respective measuring element 11a, 11b, 11c,..., 11i,..., 11N, and a possible signal loss due to a force shunt via a fastening device.

[0068] To solve such a system of equations for the torque M z , a first transverse force component F x , and a second transverse force component F y , measurement signals from at least three piezo elements 11a, 11b, 11c are required, whose preferred directions are aligned such that they lie in or parallel to a plane. Furthermore, at least two of the preferred directions must be neither parallel nor antiparallel.

[0069] For this general case with N = 3, i.e., with three piezo elements 11a, 11b, 11c, the solution to the system of equations presented above is unique. If additional measuring elements are added to measuring system 1, the system of equations is overdetermined with three parameters to be determined, M z , F x , F y , but the measurement accuracy can be further improved.

[0070] In the case of N = 4, four different systems of equations F (S1, S2, S3), F (S1, S2, S4), F (S1, S3, S4), F (S2, S3, S4) can be set up. The values ​​determined for the individual parameters M z , F x , F y to be determined can then be added and averaged, i.e., in the case of four piezo elements 11a, 11b, 11c,..., 11i,..., 11N, they can be divided by four. In a similar way, an overdetermined system of equations F (S1, S2 ..., SN) can be set up, which is solved using a minimization problem.

[0071] Once a general solution to the system of equations has been found, the calculation of the parameters to be determined, M z , F x , F y , can be reduced to a matrix multiplication. This has three rows and as many columns as the number of measurement signals S1, S2, S3, ... SN available. The matrix elements or coefficients represent the respective contributions of the individual sensors to the parameters to be determined, M z , F x , F y . Fx Fy MB = K c 11 c 12 c 13 … c 1 N c 21 c 22 c 23 … c 2 N c 31 c 32 c 33 … c 3 N s 1 s 2 s 3 … sN

[0072] For the decomposition of the measurement signals S1, S2,...Si,..., SN into components which contribute to the respective parameters M z , F x , F y to be determined, it is necessary that the position of the piezo elements 11a, 11b, 11c,..., 11i,...,11N and the orientation of the preferred directions are known.

[0073] The geometric parameters can be determined either from a design drawing of the powertrain test bench and from the knowledge of the preferred directions of the piezo elements 11a, 11b, 11c,..., 11i,...,11N.

[0074] However, the orientation of the preferred directions of the piezo elements 11a, 11b, 11c,..., 11i,..., 11N can also be determined by measuring the preferred directions using a calibration measurement. For this purpose, the piezo elements 11a, 11b, 11c,..., 11i,..., 11N are preferably clamped between two flat plates. In a next step, external transverse forces with a known direction are applied. From the magnitude of the individual measurement signals S1, S2,...Si,..., SN in relation to the magnitude and direction of the introduced transverse forces, the preferred direction of the piezo elements 11a, 11b, 11c,..., 11i,..., 11N in the plane spanned by the preferred direction of the piezo elements 11a, 11b, 11c,..., 11i,..., 11N can be determined.

[0075] Similarly, by applying a defined torque M z and measuring the individual measurement signals S1, S2,...Si,..., SN, a distance of the piezo elements 11a, 11b, 11c,..., 11i,...,11N from the rotation axis D can be determined if the preferred directions of the individual piezo elements 11a, 11b, 11c,..., 11i,...,11N are known.

[0076] Fig. 3 shows an embodiment of a system 20 for controlling an electric motor 2, which is part of a power flow.

[0077] In contrast to the Fig. 1 In the system 10 shown, the force components and / or torque components ΔM X , ΔM y , ΔF z derived from the force measurement by means of the piezo elements 21a, 21b, 21c are taken into account directly in the control means 23, which is in particular a control device. Therefore, these are preferably used as input variables in the Fig. 3 shown control characteristic 5 and taken into account accordingly in the maps and control functions.

[0078] Accordingly, the system 20 Fig. 3 also compared to System 10 according to Fig. 1 no means for adapting the control characteristic 5 itself, in the sense that a control characteristic 5 is fundamentally changed.

[0079] The system 20 comprises, in particular, means or modules which are implemented in hardware or software and are designed to Fig. 4 The method 200 shown for controlling an electric motor 2 is carried out as follows: The electric motor 2 is operated 201 as part of a power flow, in particular in a vehicle. During this operation, force measurements are again carried out 202 by means of piezo elements 21a, 21b, 21c.

[0080] Here too, the piezo elements 21a, 21b, 21c are arranged in the force flow which also applies to the electric motor 2 in such a way that the force flow is applied, in particular exclusively, to the piezo elements 21a, 21b, 21c.

[0081] On the basis of a control characteristic 5 stored in the control means or control device 23, which is stored in particular as a characteristic map or control function, control parameters I d , I q ; US , IS , f S of the electric machine 2 are set 203, wherein, in addition to other input variables IN1, IN2, the force components and / or torque components ΔM X , ΔM y , ΔF z or the change calculated by the evaluation means 22 on the basis of the force measurement are taken into account as input variables.

[0082] The Fig. 5 bis 7 show various measuring arrangements for determining a force and / or a torque applied to an electric motor 2. Such a measuring arrangement can be used both in a system for calibrating 10 an inverter control device 1, for example in the system shown in Fig. 1 shown embodiment, as well as in a system 20 for controlling an electric motor 2, for example in the system shown in Fig. 3 shown embodiment.

[0083] The Fig. 5 bis 7 Each shows a section or detail of a drive train, wherein the electric motor 2 is supported by a support device 6, in particular a base plate. The electric motor 2 drives, for example, a shaft 3, 3a or is driven by it.

[0084] The shaft 3, 3a, 3b each rotates around a rotation axis D, the extension of which is indicated as a dashed line in all three figures.

[0085] In Fig. 5 three piezo elements 11a, 11b, 11c are arranged between a flange of a first shaft part 3a and a flange of a second shaft part 3b.

[0086] The piezo elements 11a, 11b, 11c are preferably held by force or friction at the end faces between the flanges, so that all force is applied via the end faces of the piezo elements 11a, 11b, 11c. Preferably, the piezo elements 11a, 11b, 11c form a main force connection with respect to a force flow. Further preferably, there is little or no force shunt.

[0087] The first shaft portion 3a is or can be connected in a rotationally fixed manner to a rotor (not shown) of the electric motor. The second shaft portion 3b is or can be connected in a rotationally fixed manner to a load 4. The load 4 can be formed on a test bench, for example, by one or more dynamometers.

[0088] A force flow runs from the electric motor 2 via the first shaft part 3a, the piezo elements 11a, 11b, 11c, the second shaft part 3b to the load 4 or vice versa.

[0089] The force components and / or torque components determined by a force measurement on the piezo elements 11a, 11b, 11c correspond at least substantially to those force components and / or torque components which are also applied to the electric motor 2 via the first shaft part 3a.

[0090] In the measurement arrangement according to Fig. 6 the piezo elements 11a, 11b, 11c are arranged between the electric motor 2 and a support device 6, which serves as a support device or bearing 6 for the electric motor 2. In the Fig. 6 In the measuring arrangement shown, the force flow therefore runs from the support device 6, which is formed, for example, by a base plate, via the piezo elements 11a, 11b, 11c, the electric motor 2, the shaft 3 to the load 4, which is formed in particular by one or more dynamometers.

[0091] In this measuring arrangement, too, forces and / or torques are preferably introduced exclusively via the end face of the piezo elements 11a, 11b, 11c, and the piezo elements 11a, 11b, 11c are preferably non-positively, in particular frictionally, attached between the electric motor 2 and the support device 6. In this measuring arrangement, too, this main force connection takes place via the piezo elements 11a, 11b, 11c, with preferably only a small or no force shunt via other elements.

[0092] In the measurement arrangement according to Fig. 6 However, the force components and / or torque components applied to the electric motor 2 are not measured directly, but indirectly via the reaction forces or reaction moments that the support device 6 provides as an abutment to the electric motor 2. This is done via a measuring arrangement according to Fig. 5 The advantage is that the piezo elements 11a, 11b, 11c, or a measuring device of which they are a component, do not influence the rotating mass of shaft 3 or its moment of inertia and thus have no effect on the force measurement. Furthermore, when directly connected to the stator, the quality of the measurement signal is not impaired by elasticities caused by the measuring arrangement of the piezo elements 11a, 11b, 11c and by an additional mass in the shaft, and is therefore particularly direct and rigid.

[0093] The measuring arrangement according to Fig. 7 essentially corresponds to the measuring arrangement of Fig. 6 . In this measuring arrangement, a force measurement of the reaction forces is also carried out.

[0094] In this case, however, the support device 6 is not a base plate or floor plate, but rather a device for applying a load, in particular a dynamometer or a gear, which is driven by the shaft 3 and on whose housing or structure 7 the electric motor is supported. For example, the element 7 is a gear housing.

[0095] In this case, the power flow runs from the device 6 via the gear box 7, piezo elements 11a, 11b, 11c, the electric motor 2 and the shaft 3 back to the device 6. In the case shown, the device 6 is formed by a gear, which in turn is preferably connected in a rotationally fixed manner to one or more dynamometers.

[0096] Fig. 8 shows a frequency analysis diagram showing a fast Fourier transform analysis of the torque changes or the amplitudes of torque oscillations during operation of an electric motor 2. The torque changes were determined using the methods 100, 200 and systems 10, 20 described above.

[0097] The amplitudes of the torque oscillation are given in Newton meters as a function of the respective speed of the rotor of the electric motor 2 in Hertz.

[0098] The electric motor 2 used in the measurement was a three-phase synchronous motor with 48 slots and four pole pairs. Using the measurement systems 10, 20 and methods 100, 200 described above, it was determined that torque ripple peaks occur particularly at frequencies that are multiples of 48 or 4.

[0099] Fig. 9 is again a diagram of a fast Fourier transform analysis, with amplitudes of torque vibration amplitudes of the rotor of electric motor 2 plotted against the frequency spectrum from 0 to 220 Hz. Two calibration states are plotted here: a base calibration BC and a calibration OC optimized using calibration method 100.

[0100] In this case, the criteria used for optimising control characteristic 5 were, in particular, the intensity of the 4th, 8th, 24th and 48th harmonics of the oscillation system of electric motor 2 and a value of an integral of the intensity as a function of frequency.

[0101] Compared to the basic calibration BC, the optimized calibration shows significantly lower amplitudes of the respective vibration modes.

[0102] Fig. 10 shows a temporal curve of a torque on a shaft as a function of time. A torque request occurs at time t=0, with the shaft speed kept constant.

[0103] Identifiable are a delay time TD from the torque request until a torque increase, a rise time TR from reaching 10% of the torque request value to 90% of the torque request value MS, and an overshoot intensity ΔI relative to the newly set torque request value MS. MA indicates the temporal actual value / threat torque curve.

[0104] It should be noted that the described embodiments are merely examples and are not intended to limit the scope of protection, application, or structure in any way. Rather, the preceding description provides the skilled person with a guide for implementing at least one embodiment. Various modifications, particularly with regard to the function and arrangement of the described components, can be made without departing from the scope of protection as defined by the claims and equivalent combinations of features. In particular, individual embodiments can be combined with one another. Bezugszeichenliste

[0105] 1Control device 3, 3a, 3bShaft 4Load 5Control characteristic 6Support device 10Calibration system 11a, 11b, 11cPiezo element 12Evaluation means 13Adjustment means 20Control system 21a, 21b, 21cPiezo element 22Evaluation means 23Control means DRotational axis IN1, IN2Input parameters I d Longitudinal component of the rotor current I q Cross-phase component of the rotor current US Stator voltage f S Stator frequency IS Stator current TD Delay time TR Rise time ΔIOvershoot intensity MS Torque requirement

Claims

1. Method (100) for calibrating a control device (1), in particular an inverter control device, of an electric motor (2), in particular a three-phase motor, comprising the following steps: - Operating (101) the electric motor (2) as part of a force flow; - Performing (102) a force measurement by means of piezo elements (11a, 11b, 11c) which are adapted to measure a force acting via two surfaces abutting the piezo element (21a, 21b, 21c) and which are arranged in the force flow in such a way that the force flow is applied, in particular exclusively, to the piezo elements (11a, 11b, 11c), the piezo elements (11a, 11b, 11c) forming a force main circuit with respect to the force flow; and - Adjusting (103) a control characteristic (5) of the control device (1) on the basis of at least one force component derived from the force measurement, in particular a change in the at least one force component, and / or at least one torque component derived from the force measurement, in particular a change in the torque component (ΔMx, ΔMy, ΔFz).

2. Method (200) for controlling an electric motor (2), in particular a three-phase motor, comprising the following steps: - Operating (201) the electric motor (2) as part of a force flow; - Performing (202) a force measurement by means of piezo elements (21a, 21b, 21c) which are arranged in the force flow in such a way that the force flow is applied, in particular exclusively, to the piezo elements (21a, 21b, 21c), the piezo elements (11a, 11b, 11c) forming a force main circuit with respect to the force flow; and - Setting (203) at least one control parameter (Id, Iq; US, IS, fS) of the electric machine (2) on the basis of at least one force component derived from the force measurement, in particular a change in the at least one force component, and / or at least one torque component derived from the force measurement, in particular a change in the torque component (ΔMx, ΔMy, ΔFz).

3. Method (100, 200) according to claim 1 or 2, wherein the electric motor (2) is a three-phase synchronous machine and at least one control parameter is a pole wheel current, in particular its longitudinal component (Id) and transverse component (Iq) in the complex pointer diagram.

4. Method (100, 200) according to claim 1 or 2, wherein the electric motor (2) is a three-phase asynchronous machine and the at least one control parameter is a stator voltage (US) and / or a stator frequency (fS) or the at least one control parameter is a stator current (IS) and / or a stator frequency (fS).

5. The method (100, 200) according to any one of the preceding claims, wherein at least one criterion for adjusting a control characteristic or setting at least one control parameter (ld, Iq; US, IS, fS) is selected from the following group: Amplitudes of a harmonic oscillation of the change in torque and / or force; and / or an integral of the intensity of amplitudes of oscillations of the change in torque and / or force over a given frequency spectrum.

6. The method (100, 200) according to any one of the preceding claims, wherein at least one criterion for adjusting a control characteristic or setting at least one control parameter (Id, Iq; US, IS, fS) is selected from the following group: a torque rise time of 10% of a torque demand up to 90% of the torque demand; a delay time (TD) from the time of a torque request until the torque increases; and / or an intensity (Δ I) of an amplitude of an overshoot in relation to a value of 100% of a torque requirement.

7. Method (100, 200) according to one of the preceding claims, wherein force components and torque components are determined by means of a system of equations on the basis of measurement signals of the individual piezo elements (11a, 11b, 11c; 21a, 21b, 21c).

8. Method (100, 200) according to one of the preceding claims, wherein measurement signals of the individual piezo elements (11a, 11b, 11c; 21a, 21b, 21c) are decomposed into portions which contribute to the respective force components and / or torque components to be derived.

9. Method (100, 200) according to one of the preceding claims, wherein, in particular all, contributions of the individual piezo elements to the respective force components and / or torque components to be derived are taken into account.

10. Method (100, 200) according to one of the preceding claims, wherein the electric motor (2) is operated together with a shaft (3a, 3b) which transmits a force flow from or to the electric motor (2), wherein the piezo elements (11a, 11b, 11c; 21a, 21b, 21c) are arranged between a first part of the shaft (3a) and a second part of the shaft (3b) in such a way that a force, in particular shear force, can be measured between the first part (3a) and the second part (3b) by means of the piezo elements (11a, 11b, 11c; 21a, 21b, 21c).

11. Method (100, 200) according to any one of claims 1 to 9, wherein the piezo elements (11a, 11b, 11c; 21a, 21b, 21c) measure a force, in particular shear force, between the electric motor (2) and a support device (6) for supporting the electric motor (2).

12. The method (100, 200) according to any one of claims 1 to 9, wherein the electric motor (2) is operated together with a shaft (3) transmitting a force flow from or to the electric motor, wherein a measuring system of the piezo elements (11a, 11b, 11c; 21a, 21b, 21c) does not change a rotating mass of the shaft (3) and / or a rotating mass of rotating parts of an assembly of the shaft (3) and the electric motor (2).

13. System (10) for calibrating a control device (1), in particular an inverter control device, of an electric motor (2), in particular a three-phase motor, which is part of a force flow, comprising: - Piezo elements (11a, 11b, 11c) for performing a force measurement, wherein the piezo elements (21a, 21b, 21c) are adapted to measure a force acting via two surfaces abutting the piezo element (21a, 21b, 21c), and are arranged in the force flow in such a way that the force flow is applied, in particular exclusively, against the piezo elements, wherein the piezo elements (11a, 11b, 11c) form a force main circuit with respect to the force flow; - Evaluation means (12), set up for deriving at least one force component, in particular a change in the at least one force component, and / or at least one torque component, in particular a change in the at least one torque component, from the force measurement; and - Means (13) arranged for adjusting a control characteristic (5) of the control device (1) on the basis of the at least one force component derived from the force measurement and / or the at least one torque component (ΔMx, ΔMy, ΔFz) derived from the force measurement14. System (20) for controlling an electric motor (2), in particular a three-phase motor, which is part of a force flow, in particular in a vehicle, comprising: - Piezo elements (21a, 21b, 21c) set up for performing a force measurement, wherein the piezo elements (21a, 21b, 21c) are adapted to measure a force acting via two surfaces abutting the piezo element (21a, 21b, 21c) and are arranged in the force flow in such a way that the force flow is applied, in particular exclusively, against the piezo elements, the piezo elements (11a, 11b, 11c) forming a force main circuit with respect to the force flow; - Evaluation means (22), set up for deriving at least one force component, in particular a change in the at least one force component, and / or at least one torque component, in particular a change in the at least one torque component, from the force measurement; and - Control means (23), set up for setting at least one control parameter (Id, Iq; US, IS, fS) of the electric machine (2) on the basis of the at least one force component derived from the force measurement and / or the at least one torque component (ΔMx, ΔMy, ΔFz) derived from the force measurement.

15. Test stand for an electric motor, wherein the test stand has at least one support device (6) for the electric motor and a load (4) and the electric motor can be arranged in a force flow between the support device (6) and the load (4) of the test stand, wherein the test stand furthermore has a system (10) according to claim 13.