Torsional Oscillation in a Damping Drive System

Abstract

A drive system (10) includes at least one electric machine (12) and a plurality of rotating members (14) interconnected by shafts (18, 20, 22). A method for damping torsional oscillations in a drive system (10) includes: determining an angular velocity (θ i ) of at least one shaft (18) based on measured values in the drive system (10); using a function to determine a damping torque (T i ) from the angular velocity (θ damp ), the function modeling at least some of the electric machine (12), the rotating members (14), and the shafts (18, 20, 22); adjusting a reference torque (T ref ) of at least one electric machine (12) by increasing the damping torque; and controlling at least one electric machine (12) with the adjusted reference torque (T).

Description

Technical Field

[0001] The present invention relates to a method and a controller for damping torsional oscillations in a drive system. The present invention also relates to a drive system. Background Art

[0002] A drive train or more generally a drive system typically includes a number of electromechanical systems which are connected together along one or more flexible shafts. Simple examples include an electric motor connected to a load engine via a gearbox.

[0003] However, there are more complex drive systems where multiple electric motors are interconnected to multiple rotating members. For example, some or all of the electric motors and / or some or all of the rotating members may be interconnected to each other via a common shaft. As another example, the rotating members and the electric motors may be interconnected via one or more gearboxes.

[0004] In any case, the shaft or a part of the shaft may act like a torque coupling element which may cause torsional oscillations in the drive system. Generally, these torsional oscillations are undesirable and must be damped. However, for complex drive systems, generally the cause of the torsional oscillations and the method of how to damp the torsional oscillations must be determined individually based on the design of the drive system.

[0005] WO2015130901A1 describes the use of a Kalman filter for torsional damping of an electric traction drive.

[0006] EP 2194290 A2 shows a torsional oscillation damping system which has a controller with a torsional damper, the controller being configured to generate a torsional correction signal based on a torsional signal from a torsional sensor.

[0007] US2012 / 083953A1 shows a drive system for a hybrid vehicle which has a plurality of shafts. The speed of the shafts is measured and input into a number of control blocks. The rotational speed of the electric motors of the vehicle is input into a controller for determining a damping torque, where the damping torque is determined by differentiating and filtering the rotational speed depending on the state of a clutch.

[0008] WO2015 / 087132A1 relates to a system for suppressing vibrations by damping the torsion of an electric motor of a hybrid vehicle. Summary of the Invention

[0009] The object of the present invention is to provide a simple and flexible method for damping oscillations in a complex drive system.

[0010] This object is achieved by the subject matter of the independent claims. Other exemplary embodiments are apparent from the dependent claims and the following description.

[0011] One aspect of the present invention relates to a method for damping torsional oscillations in a drive system. The drive system may include at least one electric motor and a plurality of rotating members interconnected by shafts. The electric motor may be supplied with electrical energy by an electric converter. The amount of power, frequency, and / or magnitude of the current supplied to the electric converter can be controlled, and in this way, the torsional oscillations can also be controlled.

[0012] The torsional oscillations may be mechanical oscillations resulting from the torsional flexibility of the shafts and the rotating members connected thereto. Each rotating member may have a specific rotational inertia.

[0013] According to an embodiment of the present invention, the method includes: determining the angular velocity of at least some or all of the shafts based on measured values in the drive system. The angular velocity can be determined directly by speed measurements of one or more corresponding sensors. Additionally, based on a model of the drive system, additional angular velocities can be determined from the measured angular velocity.

[0014] According to an embodiment of the present invention, the method further includes: determining an angular velocity difference based on the angular velocity using a drive system model that models the drive system as a plurality of inertial elements interconnected via coupling elements, and each angular velocity difference represents the difference in angular velocity at the ends of the coupling element. For example, when a coupling element models a specific shaft, the difference between a first angular velocity at one end of the shaft and a second angular velocity at the other end of the shaft can be used as the angular velocity difference of the corresponding coupling element.

[0015] It must be noted that the inertial elements can be regarded as virtual inertial elements, and the coupling elements can be regarded as virtual springs and / or virtual damping elements because they represent and / or simplify the actual components of the drive system. The coupling elements can model the oscillation and / or damping characteristics.

[0016] The drive system model may include mechanical rotational inertia for each electric motor and each rotating member. However, the drive system model can also simplify the actual drive system, and for example, certain rotating members can be aggregated into one inertial element.

[0017] According to an embodiment of the present invention, the method includes: determining a damping torque based on the angular velocity using a function that models at least some of the electric motors, rotating members, and shafts. For example, the function can be provided in the form of a damping matrix.

[0018] According to an embodiment of the present invention, the method includes: determining the damping torque of at least one electric motor based on the angular velocity difference. The angular velocity difference can be input into the function.

[0019] The drive system may include more than one electric motor, and the damping torque can be determined for each electric motor. The above function can determine the damping torque of each electric motor.

[0020] According to an embodiment of the present invention, the angular velocity differences form an angular velocity difference vector, the damping torques of more than one motor form a damping torque vector, and the damping torque vector is equal to the angular velocity difference vector multiplied by a constant damping matrix.

[0021] The determination of the damping torques for all motors can be reduced to multiplying the angular velocity difference vector by a predetermined constant damping matrix. The damping matrix utilizes the structural design of the drive system and is the only component of the controller that may have to be adapted to the design of the drive system. In other words, the function for determining one or more damping torques based on the angular velocity and / or angular velocity differences can be a linear function.

[0022] The damping matrix is constructed such that the angular velocity differences of the coupling elements of the drive system model are converted into damping torques for the motors, and these damping torques apply torques to these coupling elements. Specifically, the angular velocity differences of the coupling elements can be mapped to two torques, which, when the corresponding motors apply these torques to the drive system, generate related forces on the components represented by the coupling elements in a direction opposite to the angular velocity differences.

[0023] The damping matrix can be a matrix having M rows for each motor and P columns for each coupling element and / or angular velocity difference. The terms of the damping matrix can be selected such that the angular velocity differences are mapped to damping torques as described above.

[0024] According to an embodiment of the present invention, the method further includes: adjusting the reference torque of each motor by adding the corresponding damping torque, and using the adjusted reference torque to control the motor. The reference torque of the motor can be provided by another controller and / or an external control loop. The adjusted torque can be used to determine the switching state of the converter of the motor, and this switching state can be switched such that the desired torque is generated.

[0025] According to an embodiment of the present invention, the terms of the damping matrix are selected such that the angular velocity differences of the coupling elements are mapped to a damping torque vector that adjusts (such as increases and / or decreases) the angular velocity of the motors that are connected to the coupling elements according to the model. As mentioned above, the damping matrix can have constant terms, and the determination of the damping torques of multiple motors can be reduced to multiplying by a constant matrix.

[0026] In summary, the method can rely on a large-scale multi-inertia model of the drive system. A multi-input multi-output controller can adjust the torque references of one or more motors of the drive system in order to dampen the oscillations in the entire drive system. The method is general and allows for any number of inertia elements and coupling elements to be included.

[0027] The damping matrix can be the product of a scaling matrix, the transpose of an input matrix, and the pseudo-inverse matrix of a difference matrix. The scaling matrix can set the height of the damping for each motor. The input matrix can model which torque affects which angular velocity difference. The difference matrix can model which angular velocities determine which angular velocity differences based on the design of the drive system.

[0028] It should be noted that the damping matrix can be calculated offline based on these three matrices.

[0029] According to an embodiment of the present invention, the damping matrix includes the transpose of the input matrix as a multiplicative factor. The input matrix can model which motor applies torque to which inertial element and / or is assigned to which inertial element. For example, the input matrix E can have M columns for each motor and N rows for each inertial element. When motor m applies E percent of its torque mn to inertial element n, the input matrix can include a term E with a value between 0 and 1 at position (m,n). mn .

[0030] According to an embodiment of the present invention, the damping matrix includes the pseudo-inverse matrix of the difference matrix as a multiplicative factor. The difference matrix models which angular velocities must be subtracted to determine the speed difference of the coupling element. The pseudo-inverse matrix of the difference matrix can be a matrix that, when multiplied by the difference matrix, results in a diagonal matrix that has only 1s and 0s on the diagonal.

[0031] The difference matrix can be a matrix that has P columns for each angular velocity in the drive system model and P rows for each coupling element. When angular velocities q and q' result in an angular velocity difference of coupling element p, the difference matrix can include 1 at position (p,q) and -1 at term (p,q').

[0032] According to an embodiment of the present invention, the damping matrix includes a scaling matrix as a multiplicative factor, which determines the amount of damping for each motor. For each motor, the scaling matrix can be a square matrix with M columns and M rows. The scaling matrix can be a diagonal matrix, and each diagonal term of the scaling matrix can be the damping factor of the corresponding motor.

[0033] According to an embodiment of the present invention, the scaling matrix is a multiple of the identity matrix. In this case, the damping coefficients of all motors can be equal.

[0034] According to an embodiment of the present invention, only a subset of the angular velocities of the shafts is determined. The angular velocity differences are determined based on the drive system model into which the subset of angular velocities is input. For example, mathematical equations can be used to calculate additional angular velocities based on the existing angular velocities.

[0035] According to an embodiment of the present invention, the angular velocities in the subset are measured. This can be performed using angular velocity sensors connected to the shafts.

[0036] According to an embodiment of the present invention, the drive system model includes inertia elements and / or coupling elements, which represent more than one rotating member and / or more than one shaft of the drive system. The drive system model can simplify the actual design of the drive system. The drive system model can be regarded as a reduced model. In the case of a reduced model, it may only be necessary to determine the angular velocity and / or angular velocity difference involved in the reduced model.

[0037] According to an embodiment of the present invention, the method further includes: determining the switching state of an electric converter of the drive system based on the adjusted reference torque, where each electric machine is powered by one of the electric converters. As already mentioned, the adjusted torque for the electric machine can be used as an input parameter of a controller that determines the switching state of the electric converter that powers the electric machine.

[0038] According to an embodiment of the present invention, the method further includes: determining a reference torque of an electric machine based on one or more reference speeds of the drive system. The reference torque can be determined by a higher-level controller and / or an external control loop. The reference torque can be provided by an override controller that can control the common speed of the entire drive system. Such a controller can be external to one or more controllers of the electric converter. The reference torque can also be provided from a speed control loop that can be part of the controller of the electric machine.

[0039] A further aspect of the present invention relates to a computer program adapted to execute the method as described herein when executed by a processor, and to a computer-readable medium in which this computer program is stored.

[0040] The computer-readable medium can be a floppy disk, a hard disk, a USB (Universal Serial Bus) storage device, a RAM (Random Access Memory), a ROM (Read-Only Memory), an EPROM (Erasable Programmable Read-Only Memory), or a flash memory. The computer-readable medium can also be a data communication network that allows downloading of program code, such as the Internet. Generally, the computer-readable medium can be a non-transitory or transitory medium.

[0041] Another aspect of the present invention relates to a controller for damping torsional oscillations in a drive system, the controller being adapted to execute the method as described herein. It must be understood that the features of the method as described above and below can be features of the controller as described above and below.

[0042] It should also be understood that the method can be implemented at least partially in software. For example, the controller can include a processor and a computer program that, when executed on the processor, is adapted to execute the method as described above and below.

[0043] The method can also be implemented at least in part in hardware. For example, the controller can include a DSP and / or an FPGA, which implement part or all of the methods described above and below.

[0044] According to an embodiment of the present invention, the controller includes an angular velocity estimator for estimating an angular velocity based on measurements in the drive system. The angular velocity estimator can encode a mathematical equation that models the behavior of the mechanical components of the drive system (such as motors, rotating components, and / or the shafts interconnecting them). The mathematical equation can model these components as inertial elements interconnected by coupling elements.

[0045] The angular velocity estimator can also determine an angular velocity difference based on the angular velocity.

[0046] According to an embodiment of the present invention, the controller includes a torsional damping unit for determining the damping torque of the motor. The torsional damping unit can receive the angular velocity difference and can determine the damping torque for each motor as described herein.

[0047] Another aspect of the present invention relates to a drive system.

[0048] According to an embodiment of the present invention, the drive system includes at least one motor; at least one electrical converter for powering the motor; a plurality of rotating components; a plurality of shafts interconnecting the at least one motor and the rotating components; and a controller as described above and below.

[0049] Using this method and the controller, only the model of the drive system needs to be suitable for the actual design of the drive system. There is no need to make considerations related to a specific drive system.

[0050] According to an embodiment of the present invention, the drive system includes at least one gearbox that interconnects the rotating components and / or at least one motor via a shaft. Similarly, the gearbox or the components of the gearbox can be modeled as one or more inertial elements interconnected by coupling elements.

[0051] It should be understood that the features of the method described above and below can be the features of the computer program, computer-readable medium, controller, and drive system described above and below, and vice versa.

[0052] These and other aspects of the present invention will become apparent and will be derived from the embodiments described below. Description of the Drawings

[0053] The subject matter of the present invention will be explained in more detail in the following text with reference to the exemplary embodiments shown in the drawings.

[0054] Figure 1 Schematically shows a drive system according to an embodiment of the present invention.

[0055] Figure 2 Schematically shows Figure 1 a model of the drive system.

[0056] Figure 3 Schematically shows a control scheme of the drive system according to an embodiment of the present invention.

[0057] Figure 4 Shows a flowchart of a method for damping torsional oscillations in a drive system.

[0058] Figure 5 Shows the Bode plot of the transfer function generated by the method using Figure 4 ...

[0059] The reference numerals used in the drawings and their meanings are listed in a summary form in the list of reference numerals. In principle, the same parts are provided with the same reference numerals in the drawings.

[0060] List of reference numerals

[0061] 10 Drive system

[0062] 12 Electric motor

[0063] 14 Rotating member

[0064] 16 Gearbox

[0065] 18 Shaft

[0066] 20 Shaft

[0067] 22 Shaft

[0068] 24 Converter

[0069] 28 Controller / control system

[0070] 30 Drive system model

[0071] 32 Speed controller

[0072] 34 Speed reference

[0073] 36 Measured value

[0074] 37 Converter controller

[0075] 38 Switching state

[0076] 40 Torsional damping unit

[0077] 42 Angular velocity estimator

[0078] J i Inertia

[0079] k ij Stiffness constant of the coupling element

[0080] θ i Angular velocity

[0081] Angular velocity difference

[0082] T ref Reference torque

[0083] T damp Damping torque

[0084] T Adjusted reference torque. Detailed implementation

[0085] Figure 1 The drive system 10 is shown, which includes a plurality of motors 12, several mechanical rotating members 14 and a gearbox 16 interconnected by shafts 18, 20, 22. The motors 12 may have a common shaft 20, the rotating members 14 may have a common shaft 22 and / or a component of the drive system 10 (such as the gearbox 16) may be connected to more than two shafts 18, 20, 22.

[0086] The motor 12 can be an electric motor, which is supplied with current by a converter 24. The converter 24 can be controlled by one or more controllers 28, which also receive measurement signals from the drive system 10.

[0087] Using measurement signals such as current, voltage and / or mechanical measurement signals such as speed, rotation frequency, etc., the controller or more generally the control system 28 determines the switching signals for the converter 24, and the converter 24 then generates the corresponding current.

[0088] One can consider the connecting shafts 18, 20, 22 as infinitely rigid elements that do not cause distortion between the components 12, 14, 16. However, in reality, the shafts 18, 20, 22 are elastic and have their own stiffness constant and damping coefficient, which introduces a difference between the angles and angular velocities seen by the motors 12, 14, 16 on one side and the gearbox 16 and the load 14 on the other side.

[0089] Figure 2 Shows a model 30 for the Figure 1 drive system 10 that takes these factors into account. The motor 12 and the load 14 as well as the gearbox 16 are modeled as inertial elements with an inertia J i The portions of the shafts 18, 20, 22 between the components 12, 14, 16 are modeled as coupling elements with a stiffness constant k i，j

[0090] ​Generally, there are inertial elements in the drive system 10, such as components 12, 14, 16, that is, it is modeled as N inertial elements with the following inertia

[0091] [J1…J N

[0092] And there are flexible elements, such as shafts 18, 20, 22 with a stiffness coefficient k i，j The following formula applies to the inertial elements connected in series, but can be generalized to more complex structures. In the case of series connection, there are N - 1 coupling elements with the following stiffness coefficients

[0093] [k 12 …k N-1N

[0094] The differential equation that controls the dynamic characteristics of the inertial elements connected in series by these coupling elements is

[0095]

[0096] Here, a j，j is the damping coefficient, and τ i is the forced torque generated by some external driving force, which in this example is the motor 12 directly acting on the i-th inertial element.

[0097] The above formula can be generalized to more complex systems that are not just series-connected. However, for clarity, only the simpler equations are given.

[0098] Generally, the above equation and the more general equations of more complex systems can be written as a matrix equation in state space form

[0099]

[0100] In this equation, Θ = [θ1…θ N is the angular position of the inertial elements, where the inertia J i forms a vector, is the angular velocity, and is the angular acceleration.

[0101] T = [τ1…τ M is the vector composed of the torques generated by M motors 12 or more general torque generators.

[0102] The input matrix E models which motor 12 is connected to which inertial element with inertia J i For example, in the case of three motors 12 and 5 inertial elements with inertia J i the input matrix E can be

[0103] ​​

[0104] Matrix B is called the incidence matrix and models how the connecting elements with coefficient k i，j interconnect the inertial elements with inertia J i . For example, in the case of inertial elements J i in series, the incidence matrix B can be

[0105]

[0106] Matrix J is the inertial element matrix and encodes the inertia J i on the diagonal.

[0107]

[0108] In the case of series inertial elements with inertia J i , the other matrices are defined as

[0109]

[0110] Generally, K encodes the stiffness constant k i，j and D encodes the damping coefficient D i，j .

[0111] For a rather complex drive system 10 with, for example, a large number of inertial elements J i , it may be attractive to reduce the size of the model equations by aggregating the inertial elements and the connecting elements into fewer dominant inertial elements.

[0112] This aggregation can be defined with the help of the partitioning matrix P, which encodes how specific inertial elements are aggregated into one replacement inertial element. Each column of the matrix P can define a partition, where 1 indicates the inertial element with inertia J i included in a specific partition.

[0113] For example,

[0114]

[0115] encodes the aggregation of the first and second inertial elements and the third and fourth inertial elements into one inertial element respectively.

[0116] Based on this, a reduced - order model can be defined

[0117]

[0118] where

[0119] stiffness coefficient matrix and the damping coefficient matrix can be defined based on partitioning, for example as a series equivalent of the original coefficients. For example, in the case of a series inertia element, by applying the formula

[0120] it is known that

[0121] It must be noted that when reducing the matrix size, a reduced model can be used. The determination of the damping torque as described herein can be accomplished using either the full model or the reduced model. Both models have the same structure.

[0122] To define the torsional damping part of the model (either the full model or the reduced model), a differential model is constructed below. This can be achieved by defining a transformation with a difference matrix L that defines which velocities θ i must be subtracted in order to output the corresponding difference for the corresponding connecting element (with label a) For example, in the case of a series inertia element, the difference matrix can be

[0123]

[0124] Using the difference matrix L, the dynamic characteristics of the model (here the reduced model) can be written as

[0125]

[0126] L + = L T (LL T ) -1 is the pseudo-inverse matrix.

[0127] Now, the dynamic characteristics are in a form such that possible damping terms can be included. The damping terms can be included through the input matrix and can have a structure similar to the terms containing the inclusion factor .

[0128] The overall feedback T can take the following form

[0129] T = T ref + T damp

[0130] T, T ref and T damp are vectors, where the number of components M is the same as the number of motors 12 present.

[0131] T ref is the reference torque given to the motor 12, which we can control and which can come from different control loops (such as speed and / or torque control loops).

[0132] Tdamp is the damping torque and is given by

[0133]

[0134] This results in the following closed-loop equations

[0135]

[0136] The matrix determines the amount of damping in the closed-loop equation system.

[0137] It is important to note that the value of the torsional natural frequency after feedback can be the same as before feedback.

[0138] The scaling matrix ρ, which can also be a single coefficient, can be regarded as an adjustment factor. Figure 3 Shows a possible controller 28 that utilizes the damping torque T as described above damp to control the electromechanical part 30 of the drive system 10.

[0139] For example, the reference speed 34 and the measured value 36 from the electromechanical part 30 of the drive system 10 can be input into the speed and / or torque controller 32, which provides the reference torque vector T ref . To the reference torque vector T ref add the damping torque vector T damp , and input the resulting torque vector T into the converter controller 37, which generates the switching command 38 for the converter 24.

[0140] The damping torque vector T damp is provided by the torsional damping unit 40, which receives the differential velocity vector and calculates the damping torque vector T according to . damp .

[0141] It must be noted that it is not necessary to know the matrices J, K, D, and B above to calculate the damping torque based on the differential velocity.

[0142] The differential velocity vector is provided by the angular velocity estimator 42 The angular velocity estimator 42 determines the differential velocity vector based on the measured value 36 in the drive system 10 For example, the velocity θ i can be directly measured by an angular velocity sensor connected to the corresponding motor 12 and / or the rotating member 14.

[0143] If the required (differential) velocity measurement value θ i cannot be obtained, then the angular velocity estimator 42 can estimate the velocity difference based on a subset of the velocities θ i in the drive system 10 and optional other measured values 36

[0144] For example, an estimation scheme that uses the system model 30, the measured angular displacement, and the (differential) angular velocity to estimate unmeasured quantities can be used.

[0145] Figure 4 A flowchart showing a method for damping torsional oscillations in the drive system 10.

[0146] In step S10, the speed controller 32 determines the reference torque T of the motor 12 based on one or more reference speeds 34 of the drive system 10 ref .

[0147] In step S12, at least some or all of the angular velocities θ of some of the shafts 18 are determined based on the measured values in the drive system 10 i .

[0148] The angular velocity estimator 42 uses the drive system model 30 to determine the angular velocity difference based on the angular velocity θ i of some or all of the angular velocities θ in the measurable subset i .

[0149] Only a subset of the angular velocities θ of the shafts 18, 20, 22 may be determined, and the angular velocity estimator 42 may determine the angular velocity difference from the drive system model 30 into which the subset of the angular velocities θ i is input i .

[0150] In step S14, the torsional damping unit 40 determines the damping torque T of each motor 12 based on the angular velocity difference damp , where the angular velocity difference forms the angular velocity difference vector and the damping torque forms the damping torque vector T damp , and the damping torque vector T damp is equal to the angular velocity difference vector multiplied by the constant damping matrix R. As described above, the damping matrix may have the following form

[0151]

[0152] Generally, the terms of the damping matrix R can be selected such that the angular velocity difference ij corresponding to the coupling element of k is mapped to the damping torque vector T damp that adjusts the angular velocity of the motor 12, which, according to the model 30, is connected to the coupling element corresponding to k ij .

[0153] ​The damping matrix R may include the transpose E of the input matrix E T as a multiplication factor. As described above, the input matrix E models which inertial element having an inertia J of which motor 12 i is applied with a torque.

[0154] A reduced model of the transpose of the input matrix may also be used. In this case, the drive system model 30 may include inertial elements and / or coupling elements, which represent more than one rotating member 14 and / or more than one shaft 18, 20, 22 of the drive system 10.

[0155] The damping matrix R may include the pseudo-inverse matrix L of the difference matrix L + as a multiplication factor. As described above, the difference matrix L models which angular velocities θ i must be subtracted to determine the speed difference of the coupling element for modeling.

[0156] The damping matrix R may include a scaling matrix ρ as a multiplication factor, which determines the amount of damping of each motor 12. The scaling matrix ρ may be a diagonal matrix and / or may be a multiple of the identity matrix.

[0157] Finally, the reference torque vector T of the motor 12 is adjusted by adding a damping torque vector T damp to regulate the reference torque vector T of the motor 12 ref .

[0158] In step S16, the motor 12 is controlled with the regulated reference torque vector T. One or more converter controllers 37 determine the switching state 38 of the electrical converter 24 of the drive system 10 according to the regulated reference torque T.

[0159] Figure 5 Shows Bode plots of the transfer function from an input torque to a speed output without torsional damping (dashed line) and with torsional damping (continuous line). The upper part of the figure shows the attenuation of the amplitude, while the lower part shows the phase shift.

[0160] The Bode plots are generated for a 15-mass spring-damper drive system model with 3 torque inputs. A sine wave disturbance is injected into one torque at the first torsional natural frequency. It can be seen that applying torsional damping to the drive system weakens the peaks of the first three torsional natural frequencies.

[0161] Although the present invention has been shown and described in detail in the accompanying drawings and the foregoing description, such illustration and description are to be considered as illustrative or exemplary and not restrictive; the present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and effected by those skilled in the art in the field and practicing the claimed invention by studying the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or controller or other unit may fulfill the functions of several items recited in the claims. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A method for damping torsional oscillations in a drive system (10), Among them, wherein the drive system (10) comprises at least one electric machine (12) and a plurality of rotating members (14) interconnected by shafts (18, 20, 22); The method comprises: Determine the angular velocity (θ i ) of at least some of the shafts (18) based on the measured values in the drive system (10); Using the drive system model (30) to determine the angular velocity difference based on the angular velocity (θ i ) The drive system model models the drive system (10) as a plurality of inertia elements (J i ) interconnected by coupling elements, and each angular velocity difference represents the difference in angular velocity at the ends of the coupling elements; Using a function based on the angular velocity difference to determine a damping torque, the function modeling at least some of the electric machine (12), the rotating member (14), and the shafts (18, 20, 22); Adjusting the reference torque (T ref ) of the at least one electric machine (12) by increasing the damping torque to determine an adjusted reference torque (T); Controlling the at least one electric machine (12) with an adjusted reference torque (T).

2. The method according to claim 1, Among them, The angular velocity difference forms an angular velocity difference vector The damping torques of more than one motor form a damping torque vector (T damp ), and the damping torque vector (T damp ) is equal to the angular velocity difference vector multiplied by a damping matrix (R).

3. The method according to claim 2, Among them, Select the terms of the damping matrix (R) such that the angular velocity difference of the coupling element is mapped to a damping torque vector (T damp ), the damping torque vector adjusting the angular velocity of the at least one electric machine (12), which, according to the model (30), is connected to the coupling element.

4. The method according to claim 2 or claim 3, Among them, wherein the damping matrix (R) comprises the transposed matrix of the input matrix (E) as a multiplicative factor; Among them, the input matrix (E) models which motor (12) applies torque to which inertial element (J i ).

5. The method according to claim 2 or claim 3, Among them, The damping matrix (R) includes the pseudo-inverse matrix (L + ) of the difference matrix (L) as a multiplication factor; Among them, the difference matrix (L) models which angular velocities (θ i ) must be subtracted to determine the speed difference of the coupling element .

6. The method according to claim 2 or claim 3, Among them, wherein the damping matrix (R) comprises a scaling matrix (ρ) as a multiplicative factor, the scaling matrix determining the damping amount of at least two electric machines (12).

7. The method according to claim 6, Among them, wherein the scaling matrix (ρ) is a multiple of the identity matrix.

8. The method according to claim 1 or claim 2, Among them, Only determine a subset of the angular velocity (θ i ) of the shafts (18, 20, 22); Among them, according to the angular velocity (θ i ), a subset of which is input into the drive system model (30), the angular velocity difference is determined 9. The method according to claim 8, Among them, Measure the angular velocity (θ i ) that is input into a subset of the drive system model (30).

10. The method according to claim 1 or claim 2, Among them, wherein the drive system model (30) comprises inertia elements and / or coupling elements, which represent more than one rotating member (14) and / or more than one shaft (18, 20, 22) of the drive system (10).

11. A controller (28) for damping torsional oscillations in a drive system, wherein the controller (28) is adapted to perform the method according to one of the preceding claims.

12. The controller (28) according to claim 11, further comprising: An angular velocity estimator (42) for estimating the angular velocity based on measurements in the drive system (10).

13. The controller (28) according to claim 11 or claim 12, further comprising: A torsional damping unit (40) for determining the damping torque of the at least one electric machine (12).

14. A drive system (10) comprising: At least one electric machine (12); At least one electric converter (24) for powering the at least one electric machine (12); A plurality of rotating members (14); A plurality of shafts (18, 20, 22) interconnecting the at least one electric machine (12) and the rotating members (14); A controller (28) according to one of claims 11 to 13.

15. The drive system (10) according to claim 14, further comprising: At least one gearbox (16) interconnecting the rotating members (14) and / or the at least one electric machine (12) by shafts (18, 20, 22).

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