Method for controlling a drive

Abstract

Method (100) for controlling a drive by means of a control loop (302) assigned to the drive, wherein the drive has a motor (312) and a transmission (322) driven by the motor (312), comprising: detecting an actual motor current value (314) of the motor (312); determining a current stiffness value (354) of the transmission (322) based on the actual motor current value (314) and a stiffness characteristic curve of the transmission (322); determining an actual natural frequency of the drive based on the current stiffness value (354); and changing a parameter of the control loop depending on the actual natural frequency.

Description

Field of the InventionThe disclosure relates to a method for regulating a drive, a control device for a drive, and a machine.Prior ArtFrom the prior art, methods and devices for controlling drives are known, which comprise a motor and a transmission. Known control devices comprise, for example, servo controllers or frequency converters. The control devices are usually designed for the stable control of a drive in the entire operating range of the drive and are performance-optimized only for the nominal range.However, known control devices have restrictions, in particular with regard to a performance or stability of the control. For example, the control may become unstable in the case of a low transmission output torque or after a running-in process, in particular during operation of a control device with a high circuit amplification.Disclosure of the InventionThe object of the disclosure is to specify a method for regulating a drive which is improved compared to the prior art. In particular, a method should be specified which has a high performance of the control or a high stability of the control for various torques provided by the drive. The method advantageously has a control with high stability with simultaneous high performance, for various torques provided by the drive. A control device and a machine are also to be specified.The object is achieved by a method for regulating a drive according to claim 1 and by a control device and a machine according to the subordinate claims.According to one aspect, a method for regulating a drive by means of a control circuit assigned to the drive is specified, wherein the drive has a motor and a transmission driven by the motor. The method comprises detecting an actual motor current value of the motor. The method comprises ascertaining a current stiffness value of the transmission based on the actual motor current value and a stiffness characteristic curve of the transmission. The method comprises determining an actual natural frequency of the drive based on the current stiffness value. The method comprises changing a parameter of the control loop as a function of the actual natural frequency.According to a further aspect, a control device for a drive is specified. The control device is configured to execute a method according to one of the embodiments described herein.According to yet another aspect, a machine is provided. The machine comprises a drive. The machine comprises a control device according to one of the embodiments described herein.In typical embodiments, the control loop is assigned to a drive, in particular is configured for controlling the drive. The drive typically comprises a motor. The motor can be, for example, an electric motor, in particular a permanent magnet synchronous motor (PMSM) or an asynchronous machine. A PMSM may be precisely controlled or provide high efficiency, for example. Typically, the drive comprises a transmission driven by the motor. For example, the transmission can be a coaxial transmission, in particular a planetary transmission or a hollow shaft transmission, or an angle transmission. In typical embodiments, the drive comprises a servo drive or a control device. Typically, the drive is configured to drive a load. The load is typically coupled to the transmission. In typical methods, the drive drives a load coupled to the transmission. Typically, the motor, in particular together with the transmission or the load, forms a controlled system of the control circuit.According to typical embodiments, the control loop is implemented in a control device of the drive and is connected to the control path. The control device can have one or more controllers, for example a position controller (e.g. a P controller), a rotational speed controller (e.g. a PI controller) or a current controller (e.g. a PI controller). The control device can have one or more setpoint filters, for example a setpoint position filter or a setpoint current filter. The regulating device can be arranged in the drive, in particular in a housing of the drive. In embodiments, the control device is integrated into the drive. Signal feedbacks of the control system can correspond to a structure of a cascade control. For example, the difference between the current setpoint value and the actual motor current value can be supplied to a current regulator. The same applies analogously to a speed controller or a position controller.Typically, a transmission stiffness of the transmission is dependent on a torque application to the transmission, in particular on the torque application and an angular position of the transmission. Depending on the torque application or the angular position, in a drive train comprising the motor, the transmission and the load, a natural frequency of the drive can change due to the variable transmission stiffness. Known regulations can be operated in the nominal range in a non-performance-optimal manner, in order to be stable at all operating points, or the regulations can become unstable if a transmission torque deviates from a rated transmission torque of the drive.In the case of the transmission torque deviating from the rated transmission torque, the transmission rigidity and the natural frequency can deviate from the corresponding values for the rated transmission torque. For example, a control in the range of the rated transmission torque can be stable, but become unstable if the transmission rigidity and thus the natural frequency are reduced by a reduced transmission torque. Instability can occur in known controllers in particular when a control device, e.g. a servo controller or a frequency converter, is operated with high loop amplification. Typical methods and control devices according to embodiments described herein may in particular avoid or reduce instabilities of the regulation by taking into account a current stiffness of the transmission and an actual natural frequency based on the current stiffness.According to typical embodiments, the method comprises detecting an actual motor current value of the motor. In embodiments, the actual motor current value is detected by a control device according to embodiments described herein. The control device is typically configured to carry out methods described herein. The control device may comprise a control device. The control device is typically communicatively connected to the control device. The control device is typically configured to parameterize the control device. In particular, the control device is typically configured to change a parameter of the control device. The control device can be arranged together with the regulating device in the drive, in particular in a converter of the drive. In embodiments, the control device may be arranged in the control device. In further typical embodiments, the control device can be arranged separately from the regulating device, in particular outside the drive. In embodiments, the control device may comprise the control device and the regulating device. In particular, the control device can comprise the control loop for controlling the drive and be configured to change a parameter of the control loop.In typical embodiments, the actual motor current value of the motor is measured by a measuring device. The measuring device can be configured to measure one or more further operating parameters of the drive or of a load driven by the drive. Typically, the measuring device transmits the actual motor current value to the regulating device. The control device, in particular the control device, can record the measured actual motor current value from the measuring device or from the regulating device. In embodiments, the control device may comprise the measuring device. Typically, the control device or the measuring device outputs the actual motor current value to the control device, in particular to the control device. The measuring device may transmit a rotational speed of the motor ω Mot, a rotational speed of the load ω Last, an angular position of the motor φ Mot, an angular position of the load φ Last, or a temperature of the motor T Mot to the control device. In embodiments, the actual motor current value is transferred from the measuring device to the regulating device for regulating the drive. The rotational speed of the motor ω Mot, the rotational speed of the load ω Last, the angular position of the motor φ Mot or the angular position of the load φ Last can be transferred from the measuring device to the regulating device. In embodiments, the load may be regulated, with ω Last and φ Last being fed back to the regulator for regulation. In further embodiments, the drive can be controlled, wherein ω Mot and φ Mot are fed back to the control device for control purposes.The rotational speed of the motor or of the load can also be referred to herein as the rotational speed of a motor shaft of the motor or as the load shaft rotational speed. An angular position can also be referred to as a "position", for example the angular position of the motor as the motor shaft position or the angular position of the load as the load shaft position.According to typical embodiments, the method comprises determining a current stiffness value of the transmission based on the actual motor current value and a stiffness characteristic of the transmission. The stiffness characteristic is typically predetermined. In particular, the stiffness characteristic curve is typically determined before the actual motor current value is detected and before the current stiffness value is determined. The stiffness characteristic may be determined, for example, according to embodiments described herein. The stiffness characteristic curve can be contained in a digital twin of the drive or of the drive train. The digital twin may be implemented in the control device, for example.In embodiments, determining the current stiffness value includes determining a torque acting on the transmission based on the actual motor current value. In embodiments, the torque may additionally be determined based on a speed of a motor shaft of the motor, a motor shaft position of the motor, a temperature of the motor, a load shaft speed of a load driven by the drive, or a load shaft position of the load. For example, the speed of the engine or load may be used to calculate friction torques of the engine, transmission or load. In particular, the torque acting on the transmission can be determined more accurately. The temperature of the engine may be used to more accurately determine the torque acting on the transmission, for example, via a calculation of the engine losses. The torque at the output of the transmission may be calculated from the actual motor current value using a torque constant of the motor and a gear ratio of the transmission. The torque can be calculated in particular by the digital twin.The torque may be determined using a model of the drive, for example. The model can be stored in the digital twin of the controlled system. For example, the model may describe how the motor torque constant varies with temperature. By providing the temperature of the engine to the controller, a current engine torque constant may be determined using the model. In particular, the actual torque acting on the transmission can be determined more accurately.Typically, the current stiffness value of the transmission is determined based on the determined torque. In particular, the current stiffness value is determined based on the stiffness characteristic curve and the determined torque. The current stiffness value may be determined from the DigitalTwin. Based on information about the angular position of the load or of the motor, a position dependence of the stiffness value can be taken into account. In typical embodiments, the current stiffness value is transferred to an adaptation algorithm, in particular from the DigitalTwin to the adaptation algorithm. The adaptation algorithm is typically implemented in the control device.Typically, the method comprises determining an actual natural frequency of the drive on the basis of the current stiffness value. The actual natural frequency can be calculated in particular on the basis of a model of the drive or of the drive train using the current rigidity value of the transmission, for example on the basis of a mass oscillator model.According to typical embodiments, the method comprises changing a parameter of the control loop depending on the actual natural frequency. Typically, the control device outputs the parameter to the regulating device for changing the parameter, in particular for changing the parameter in a regulator or a filter of the regulating device. Typically, the parameter comprises a controller parameter of a controller of the control device or a filter parameter of a filter of the control device. In embodiments, the method includes controlling the drive using the control loop with the changed parameter. In typical embodiments, operations of the method, in particular operations from the detection of the actual motor current value of the motor, are repeatedly carried out during an operation of the drive. In embodiments, the parameter is changed when the actual natural frequency is different from a predetermined natural frequency. If the actual natural frequency does not differ from the previously determined natural frequency, the method can be continued with a renewed detection of an actual motor current value.In embodiments, the drive is speed controlled. Typically, the modified parameter is a parameter of a speed regulator of the drive, in particular of a speed regulator of the regulating device of the drive. The speed controller may be a PI controller. Typically, the modified parameter comprises a gain k p or a reset time T n, in particular a parameter set comprising or consisting of the gain k p and the reset time T n. The parameters k p and T n can be calculated, for example, according to the root locus method.In embodiments, the drive is speed-controlled and position-controlled. In position control, a parameter of the position setpoint filter is typically changed. The modified parameter can comprise, for example, a jerk frequency. In typical embodiments with speed-controlled and position-controlled drive, the parameter is a parameter set comprising or consisting of a parameter of the speed controller and a parameter of a position setpoint filter. In further embodiments, the modified parameter is exclusively a parameter of the setpoint position filter.According to typical embodiments, the parameter to be changed may be selected and changed depending on the actual natural frequency. In embodiments, the altered parameter is a first parameter when the actual natural frequency is less than a frequency threshold. The changed parameter is a second parameter different from the first parameter when the actual natural frequency is greater than the frequency threshold value. According to embodiments, the frequency threshold value is at least 70 Hz, in particular at least 80 Hz or at least 90 Hz, or at most 150 Hz, in particular at most 130 Hz or at most 110 Hz. For example, the frequency threshold may be 100 Hz. According to further embodiments, the parameter to be changed can additionally be selected depending on the presence of position regulation.In typical embodiments, the first parameter is a parameter of a speed controller or a parameter of a position setpoint filter. The parameter of the speed regulator can comprise a gain k p or a reset time T n in particular the gain k p and the reset time T n. The parameter of the setpoint position filter can comprise a jerk frequency. According to typical embodiments, the second parameter is a parameter of a current setpoint filter. The parameter of the current setpoint filter can comprise, for example, a blocking frequency.According to typical embodiments, the current stiffness value of the transmission is determined based on, among other things, a stiffness characteristic of the transmission. In embodiments, the stiffness characteristic curve provides a relationship for calculating a respective stiffness value for a plurality of torques, in particular for all torques in a working range of the transmission. Typically, the stiffness characteristic curve indicates a relationship between stiffness and torque. Alternatively, the rigidity characteristic line can also indicate, for example, directly a relationship between the rigidity and one or more other values, in particular the actual motor current value.Typical methods include sensing torque-torque angle hysteresis of the transmission. For example, a hysteresis curve for the connection between the angle of rotation of the transmission and the applied torque can be measured for the transmission. The detection of the hysteresis typically comprises applying a plurality of different torques to the transmission and measuring the respective rotational angles of the transmission. Typically, the transmission is subjected to torques in both rotational directions. The torques comprise in particular torques up to the rated torque.Typical methods include determining the stiffness characteristic from the torque-twist angle hysteresis. Typically, a compensation curve is calculated between an upper branch and a lower branch of the hysteresis curve, in particular centrally between the upper branch and the lower branch. The compensation curve typically provides a clear relationship between the angle of rotation and the applied torque. With the formula c=M / φ with c as stiffness, M as torque and φ as angle of rotation, the stiffness characteristic curve can be calculated, in particular for the entire working range of the transmission. In embodiments, the method comprises storing the stiffness characteristic curve in the control device, in particular in a model of the transmission. Additionally, a transmission ratio of the transmission or an engine torque constant of the engine may be stored. For example, the stiffness characteristic curve can be stored in a digital twin in the control device.Typically, the torque-rotation angle hysteresis of the transmission is detected and, in particular, the rigidity characteristic line is determined before the actual motor current value is detected. Typically, the torque-rotation angle hysteresis of the transmission is detected and, in particular, the rigidity characteristic line is determined as a temporally first step of methods described herein. In typical embodiments, the torque-rotation angle hysteresis of the transmission is detected and, in particular, the rigidity characteristic line is determined in an offline state of the drive. Typically, the storing of the stiffness characteristic line in the control device is performed in the offline state. An offline state is typically understood to mean a state before the drive is put into operation, in particular before producing operation of a machine or in particular before installation of the transmission in a machine set up for an application. For example, the operations may be performed in an offline state at a manufacturer of the transmission. Typically, the detection of an actual motor current value of the motor, the determination of the current rigidity value, the determination of the actual natural frequency of the drive, and the change of the parameter of the control loop take place in an online state of the drive, in particular after installation of the drive in a machine set up for an application or in particular in producing operation in a machine set up for an application.Typically, the control device, in particular a control device of the control device, comprises at least one processor and, for example, a memory or supporting circuits. Typically, the at least one processor is coupled to the memory. Instructions for executing methods described herein may be stored in the memory as a software routine, for example, and executed by the at least one processor. Additionally or alternatively, method steps may be implemented in a hardware controller, for example in an application specific integrated circuit. In typical embodiments, the control device, in particular the control device, is configured to carry out methods described herein. In particular, a digital twin of the drive or of the drive train or an adaptation algorithm according to embodiments described herein can be implemented in the control device for executing method steps.In accordance with typical embodiments, a machine is provided. Typically, the machine comprises a drive. The drive typically comprises a motor and a transmission. The drive is typically controlled by a control device. In embodiments, the drive may include a motor, a transmission, and the control device. Typically, the machine comprises a control device according to embodiments described herein, in particular a control device for parameterizing the control device. In embodiments, the machine may include a load driven by the drive.Typical embodiments may provide the advantage over the prior art that a higher performance of the control can be provided or that instabilities in the control of a drive can be avoided, in particular in the case of low transmission output torques compared to a rated transmission output torque. In embodiments, the transmission stiffness and an actual natural frequency can be determined depending on the working point. Drive trains in which gears are installed behave non-linearly due to the varying gear stiffness. In non-linear systems, the natural frequency and thus the quality of a filter or regulator setting depends on the operating point.Based on the actual natural frequency, a controller adaptation can be carried out, which optimizes or stabilizes the control performance, in particular over the entire operating range of the drive. Drives according to embodiments can be stably controlled, in particular even with high circuit amplification. A reduction of the circuit amplification for more stable control, a reduced dynamics of the control and any opportunisticity costs resulting from a reduced dynamics can be avoided. Furthermore, embodiments can have the advantage over the prior art that drives with transmissions of lower rigidity can be stably regulated. Transmissions of lower stiffness can be more cost-effective than more rigid transmissions. Drives described herein can be operated dynamically to the maximum extent, in particular without structural changes having to be made to the drive.Brief Description of the DrawingsFurther advantages and features of preferred embodiments of the invention are explained below with reference to the attached drawings, wherein: FIG. 1 is a flowchart of a method for controlling a drive according to a typical embodiment; FIG. 2 is a graph showing a torque-torque-rotation angle hysteresis and a balance curve; and FIG. 3 is a schematic structural diagram of a machine according to a typical embodiment.DESCRIPTION OF EMBODIMENTSTypical embodiments are described below with reference to the figures, wherein the invention is not limited to the exemplary embodiments, but rather the scope of the invention is determined by the claims.FIG. 1 shows a method 100 for controlling a drive according to a typical embodiment, wherein the drive comprises a motor and a transmission driven by the motor. The method 100 of FIG. 1 includes operations performed in an offline state 110 of the drive, in particular of the transmission. In particular, the operations of the offline state 110 are carried out before the drive is put into operation in an application, for example in a production machine. The method 100 of FIG. 1 further comprises operations which are carried out in an online state 120 of the drive, in particular after the drive has been put into operation in an application, for example in a production machine. In particular, in the online state 120, the drive is put into operation.At block 112, a torque-torque angle hysteresis of the transmission is detected. FIG. 2 shows a graph 200 for illustrating a relationship between a torque 210 and a rotation angle 220 of a transmission, for example a planetary transmission. The solid curve shows a measured torque-torque angle hysteresis 230 of the transmission.At block 114 in FIG. 1, a compensation curve is calculated based on the torque-torque angle hysteresis. In FIG. 2, for example, a balance curve 240 (dotted curve) centered between an upper arm and a lower arm of the torque rotation angle hysteresis 230 is calculated. At block 116, a transmission stiffness characteristic is calculated based on the compensation curve, particularly for the entire operating range of the transmission. The stiffness characteristic is calculated at block 116 using the formula c=M / φ with c as stiffness, M as torque, and φ as angle of rotation.FIG. 3 shows a schematic structural diagram of a machine 300 having signal flows for controlling a drive according to typical methods, for example according to method 100 of FIG. 1. the machine 300 has a control loop 302 having a control device 330, a controlled system 310 and a signal feedback to the control device 330. The controlled system 310 comprises a drive having a motor 312 and a transmission 322, and a load 324 driven by the drive. In FIG. 3, the signal feedback is provided by a measurement device 370 of the machine 300. The measurement device 370 is configured to measure one or more operating parameters of the drive or load 324. The control device 330 is configured to control the drive. The machine 300 further comprises a control device 350, which is configured to adapt a parameter of the control device 330 according to embodiments described herein. In particular, the control device 350 comprises a digital twin 352 of the drive implemented in the control device 350, and an adaptation algorithm 356 for changing a parameter of the control loop 302 of the control device 330.Referring to FIGS. 1 and 3, at block 118, the calculated stiffness characteristic, and more specifically a gear ratio of the transmission 322 and an engine torque constant of the engine 312, is stored in the controller 350, more specifically in the digital twin 352 of the drive.In the online state 120 of the drive, at block 122, an actual motor current value 314 of the motor 312 is measured by the measuring device 370 and in particular detected by the control device 350, for example by the digital twin 352. At block 124, a current stiffness value 354 is determined based on the current motor current value 314. The determining includes determining a torque acting on the transmission 322 based on the actual motor current value 314. Further, at block 124 in FIG. 1, the torque is determined based on a temperature 320 of the motor 312 and a speed 316 of the motor 312. The temperature 320 and the rotational speed 316 are measured by the measuring device 370 and transferred to the control device 350, in particular to the digital twin 352. In further embodiments, the torque may be determined based only on the actual motor current value 314. In still further embodiments, in addition to or as an alternative to the speed 316 of the motor 312, a speed of the load 324 may be used to determine the torque.Further, at block 124, the current stiffness value 354 of the transmission 322 is determined based on the determined torque and the stiffness characteristic determined in the offline state 110. The current stiffness value 354 is further determined based on a motor shaft location 318 of the motor 312. The motor shaft position 318 is measured by the measuring device 370 and transferred to the control device 350. Additionally or alternatively, to the motor shaft location 318, the current stiffness value 354 may be determined based on a load shaft location of the load 324, in further embodiments. In particular, in FIGS. 1 and 3, use of the temperature 320, the speed 316, and the motor shaft location 318 of the motor 312 allows for more accurate determination of the current stiffness value 354.At block 125, the current stiffness value 354 is passed to the adaptation algorithm 356 of the controller 350. Furthermore, the adaptation algorithm 356 determines an actual natural frequency of the drive at block 125 based on the current stiffness value 354, in particular for further use according to the following block 126.At block 126, a check is made as to whether the natural frequency has changed, in particular whether the actual natural frequency differs from a previously determined natural frequency. If the actual natural frequency is not different from a previously determined natural frequency (arrow 132), the method 100 returns to detecting an actual motor current value (block 122). If the actual natural frequency differs from a previously determined natural frequency or if the actual natural frequency is first determined (arrow 128), the method 100 proceeds to block 130.At block 130, a parameter of the control loop 302 of the control device 330 is changed depending on the actual natural frequency. In particular, the parameter is output from the control device 350 to the regulating device 330 for changing the parameter in a filter or regulator of the regulating device 330. The parameter of the control loop 302 is changed and used by the control device 330 for controlling the drive. For ongoing regulation during operation of the drive, the method jumps back at block 130 to record an actual motor current value 314 (block 122). Examples of changing the parameter of the control loop 302 at block 130 are explained in more detail in connection with FIG. 3.As already explained above, FIG. 3 shows a machine 300 with the controlled system 310, the control device 330 and the control device 350. The control device 330 comprises in FIG. 3 a setpoint position filter 332, a position controller 334 (P controller), a speed controller 336 (PI controller), a setpoint current filter 338 and a current controller 340 (PI controller). The control by the control device 330 corresponds to a cascade control. In FIG. 3, for the purpose of regulating the drive, the regulating device 330 calculates, for example, a difference between a motor current setpoint 315 and the actual motor current value 314 and passes it to the current regulator 340. Similarly, a difference between a desired position 319 and the motor shaft position 318 is provided to the position controller 334, and a difference between a desired speed 317 and the speed 316 of the motor 312 is provided to the speed controller 336. In the case of regulation of the load, in further embodiments a load shaft position and a rotational speed of the load can be used to calculate corresponding differences and fed to the corresponding controllers. The interaction between the controlled system 310, the control device 330 and the control device 350 takes place as explained, for example, in connection with the method 100 in FIG. 1.In FIG. 3, in the case of excitations by disturbance variables, for example, in the case of the action of external forces, and natural frequencies in the drive of less than 100 Hz, a parameter of the speed regulator 336 is changed (see star 360), in particular a parameter set comprising the proportional component of the amplification k p and the adjustment time T n. For example, upon application of external forces, the speed controller 336 acts against these external forces to maintain a desired speed. The motor 312 must brake or accelerate, with the torque applied changing. With the change of the torque, the current transmission stiffness and the actual natural frequency also change. Previously designed parameters k p and T n for the speed regulator 336 are no longer optimal. The adaptation algorithm 356 calculates (block 130 in FIG. 1 ) the currently optimum parameter set k p and T n for the speed regulator 336 on the basis of the actual natural frequency and supplies this modified parameter set to the regulating device 330, in particular to the speed regulator 336.As an alternative to changing the parameter set of the speed regulator 336, in the case of a position-controlled drive with a natural frequency of less than 100 Hz, a parameter of the position setpoint filter 332 can be changed. For example, in the case of a position-controlled drive, the natural frequency could be excited in the event of a change in the position setpoint 319. Excitation of the natural frequency can be prevented at a known natural frequency by a suitable filter, such as a jerk filter. According to embodiments described herein, the current transmission stiffness and the actual natural frequency at the operating point of the drive are taken into account in the path planning. As shown in FIG. 3, excitation of the actual natural frequency can be prevented by setting the setpoint position filter 332 to a jerk frequency to be filtered at present (see star 358 in FIG. 3 ), which arises from the determined actual natural frequency. In particular, excitation of the actual natural frequency at each working point caused by a changed setpoint position value 319 can be prevented.In FIG. 3, at natural frequencies in the drive train greater than 100 Hz, a parameter of the current setpoint filter 338 is changed (star 362 in FIG. 3 ). In cascade control, high natural frequencies are usually excited by the current control circuit, since this has correspondingly small controller time constants. By filtering the current setpoint value, for example using a notch or blocking filter or using other current setpoint value filters, this excitation can be prevented. For setting the current setpoint filter 338, the determined actual natural frequency is used. In particular, the current setpoint filter 338 can be optimally set at each operating point by adjusting the cut-off frequency based on the actual natural frequency. This prevents the current regulator 340 from exciting the actual natural frequency. According to the embodiments described herein, a high performance of the control can be achieved at different operating points, in particular at all operating points of the drive. Furthermore, instability of the control at the various operating points can be avoided.

Claims

Method (100) for regulating a drive by means of a control circuit (302) assigned to the drive, wherein the drive has a motor (312) and a transmission (322) driven by the motor (312), comprising: detecting an actual motor current value (314) of the motor (312); determining a current rigidity value (354) of the transmission (322) based on the actual motor current value (314) and a rigidity characteristic curve of the transmission (322); determining an actual natural frequency of the drive based on the current rigidity value (354); and changing a parameter of the control circuit (302) depending on the actual natural frequency.The method (100) of claim 1, further comprising: detecting a torque-torque angle hysteresis (230) of the transmission (322); and determining the stiffness characteristic from the torque-torque angle hysteresis (230).The method (100) of claim 2, wherein the sensing of the torque-torque angle hysteresis (230) of the transmission (322) and the determining of the stiffness characteristic are performed prior to the sensing of the actual motor current value (314).Method (100) according to Claim 2 or 3, wherein the torque-rotation angle hysteresis (230) of the transmission (322) is detected before the drive is put into operation.Method (100) according to one of the preceding claims, wherein the drive is speed-controlled, and wherein the parameter is a parameter of a speed controller (336) of the drive.Method (100) according to one of Claims 1 to 4, wherein the drive is speed-controlled and position-controlled, wherein the parameter is a parameter set consisting of a parameter of the speed controller (336) and a parameter of a position setpoint filter (332), or wherein the parameter is exclusively a parameter of the position setpoint filter (332).The method (100) according to any one of the preceding claims, wherein the changed parameter is a first parameter when the actual natural frequency is less than a frequency threshold; and wherein the changed parameter is a second parameter different from the first parameter when the actual natural frequency is greater than the frequency threshold.Method (100) according to claim 7, wherein the frequency threshold value is at least 70 Hz and / or at most 150 Hz.Method (100) according to Claim 7 or 8, wherein the first parameter is a parameter of a speed regulator (336) and / or a parameter of a setpoint position filter (332).The method (100) of any of claims 7 to 9, wherein the second parameter is a parameter of a current setpoint filter (338).The method (100) of any preceding claim, wherein determining a current stiffness value (354) of the transmission (322) based on the current motor current value (314) and the stiffness characteristic of the transmission (322) comprises: determining a torque acting on the transmission (322) based on the current motor current value (314), the torque additionally determined based on a speed of a motor shaft of the motor (312), a motor shaft position of the motor (312), a temperature of the motor (312), a load shaft speed of a drive driven load (324), and / or a load shaft position of the load (324); and determining the current stiffness value (354) based on the determined torque.Method (100) according to one of the preceding claims, wherein the drive further comprises a regulating device.Control device for a drive, configured to carry out a method (100) according to one of the preceding claims.Machine (300) comprising a drive and a control device according to claim 13.

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