METHOD FOR OPERATING A DRIVETRAIN AND DRIVETRAIN

Description

[0001] The invention relates to a method for operating a drive train and drive train.

[0002] It is generally known for inverter-fed electric motors that the signal electronics determine the actual value of the torque from the detected motor current, from the motor voltage and / or from the curve of the detected angular position of an electric motor.

[0003] It is also generally known that converters provide an electric motor with such a motor voltage that it is controlled to a torque setpoint.

[0004] From DE 10 2007 028 914 A1, the closest prior art is a device for controlling and / or regulating the speed of an electric motor.

[0005] DE 691 20 486 T2 discloses a method for calculating the moment of inertia in a motor speed controller.

[0006] From EP 2 690 777 A2 the closest prior art engine control device is known.

[0007] From JP 3 479922 B2 a load determination in an electric motor drive system is known.

[0008] From XP055299894, a play compensation in the power train of a vehicle is known.

[0009] The invention is therefore based on the object of achieving the highest possible control quality when controlling an electric motor.

[0010] According to the invention, the object is achieved by the method according to the features specified in claim 1 and by the drive train according to the features specified in claim 11.

[0011] Important features of the invention in the method for operating a drive train are that the drive train has an electric motor and a load driven by the electric motor or by a transmission driven by the electric motor, wherein a sensor for detecting the angular position of a rotor of the electric motor is provided, in particular arranged on the electric motor, wherein a motor voltage is made available to the electric motor by means of the converter, in particular by means of a motor control means of the converter, in order to achieve a torque setpoint M_setpoint, wherein, in particular recurringly over time, an actual angular velocity value ω_actual and an actual angular acceleration value α_actual are determined from the values ​​of the angular position of the rotor detected by the sensor, wherein the torque setpoint M_setpoint is determined from a moment of inertia J_total and an angular acceleration setpoint α_setpoint, which is determined as a manipulated variable by a speed controller element to which the difference, in particular control deviation, between the actual angular velocity value ω_actual and the angular velocity setpoint w_setpoint is supplied, wherein the moment of inertia J_total is determined as the sum of the moment of inertia J_Mot of the drive train without load and the moment of inertia J_Load of the load,where the moment of inertia J_Last of the load is determined from an actual torque value M_ist and from the actual angular acceleration value α_ist, in particular taking into account the moment of inertia J_Mot. ,

[0012] The advantage here is that the speed and torque of the load can be controlled with high control quality. This is because the moment of inertia J_total can be determined from the quotient of the actual torque value and the actual angular acceleration value. According to the state of the art, the actual torque value can be determined from the motor current and preferably another variable, such as motor voltage and / or the angular position of the electric motor's rotor. Thus, the actual value of the moment of inertia can be determined at any time and used for motor control, in particular speed control. Motor control can also be implemented according to the state of the art, with the parameter used there for the moment of inertia being determined according to the invention. Thus, when the drive train changes, such as changing the moment of inertia of the load, the moment of inertia can be determined and control can be carried out using a current value of the moment of inertia.

[0013] In an advantageous embodiment, the actual torque value M_actual is determined from the motor current measured by a current sensor and from the measured values ​​of the rotor's angular position x. This is advantageous because a state-of-the-art method for determining the actual torque value M_actual can be applied.

[0014] In an advantageous embodiment, the actual torque value M_actual is determined from the motor current measured by a current sensor and from the measured motor voltage U and / or from the measured values ​​of the rotor's angular position x. Advantageously, a method known from the prior art for determining the actual torque value M_actual can be applied.

[0015] In an advantageous embodiment, the moment of inertia J_Mot of the drive train without load is specified as a parameter. This is advantageous because the moment of inertia of the motor rotor can be determined with high precision during motor manufacture, thus determining J_Mot with high precision. Therefore, only the load-side or other moment of inertia needs to be determined to obtain a reliable value for the moment of inertia.

[0016] In an advantageous embodiment, the torque setpoint M_setpoint is calculated as the product of the moment of inertia J_total and the angular acceleration setpoint α_setpoint. This allows for simple torque determination.

[0017] In an advantageous embodiment, the moment of inertia J_Load of the load is determined as the quotient of the actual torque value M_actual and the actual angular acceleration value α_actual, reduced by the moment of inertia J_Mot. This is advantageous because a currently existing value of the load's moment of inertia can be determined.

[0018] In an advantageous embodiment, the moment of inertia J_Last of the load is determined at a first time as the first quotient of the actual torque value M_ist and the actual angular acceleration value α_ist reduced by the moment of inertia J_Mot, wherein the actual angular acceleration value α_ist lies in a first value range, Wherein, after the first point in time, the moment of inertia J_Load of the load is determined at a second point in time as the second quotient of the actual torque value M_act and the actual angular acceleration value α_act, reduced by the moment of inertia J_Mot, where the actual angular acceleration value α_act lies within a second value range, wherein an updated moment of inertia J_Load is determined by adding the difference between the second and the first quotient to the previously determined value of the moment of inertia J_Last. The advantage here is that tracking, i.e. updating the moment of inertia, is possible.

[0019] In an advantageous embodiment, the first range is one value range of the angular acceleration, and the second range is a different value range of the angular acceleration, whereby the two value ranges do not overlap but are spaced apart from each other. The advantage here is that with a sufficiently large distance between the value ranges, the best possible signal-to-noise ratio can be achieved, thus enabling a reliable determination of the value of the moment of inertia.

[0020] In an advantageous embodiment, the respective determined values, in particular the moment of inertia J_Load of the load, are filtered, in particular low-pass filtered. This is advantageous because the measurement noise can be reduced.

[0021] In an advantageous embodiment, the speed controller element is designed as a PI controller, wherein it has a proportional element and an integrating element connected in parallel to the proportional element, wherein the proportionality constant of the proportional element is a function of the moment of inertia J_Mot and the total moment of inertia J_ges, wherein the time constant of the integrating element is a function of the moment of inertia J_Last and the total moment of inertia J_ges. The advantage here is that the function can be selected such that a drive train with backlash, in particular with a connection subject to backlash, can be operated with the same control behavior, in particular with the same time constant and with the same transient response characteristics, as the same drive train without the backlash, in particular with a backlash-free connection instead of the connection subject to backlash. In addition, the P-element reacts according to the part of the drive train that is connected to the rotor of the electric motor without backlash, so that correspondingly good control behavior can be achieved within the backlash.

[0022] In an alternative advantageous embodiment, the speed controller element is designed as a PI controller, wherein it has a proportional element and an integrating element connected in parallel to the proportional element, wherein the proportionality constant of the proportional element is a function of the moment of inertia J_Load and the total moment of inertia J_total, wherein the time constant of the integrating element is a function of the moment of inertia J_Mot and the total moment of inertia J_total. The advantage here is that the function can be selected such that a drive train with backlash, in particular with a connection subject to backlash, can be operated with similar control behavior to the same drive train without the backlash, in particular with a backlash-free connection instead of the connection subject to backlash. In addition, a control behavior is activated even within the backlash, which is essentially coordinated with the load moment of inertia, so that the transition from the backlash area to the area outside the backlash is carried out with little jerk.But even outside the lots, a smooth, low-jerk behavior is possible due to the small time constants.

[0023] According to the invention, the speed controller element is designed as a PI controller, wherein it comprises a proportional element and an integrating element connected in parallel to the proportional element, wherein the proportionality constant of the proportional element is a function of the product of the moment of inertia J_Mot and the moment of inertia J_Last of the load, and / or wherein the time constant of the integrating element is a function of the product of the moment of inertia J_Mot and the moment of inertia J_Last of the load. The advantage here is that optimized backlash control can be achieved, since the moment of inertia J_Mot and the moment of inertia J_Last of the load are determined separately and used multiplied by one another.

[0024] Important features of the drive train are that it is configured to perform the aforementioned process. The advantage here is that the rotation of the load can be controlled with high control quality.

[0025] Further advantages are set forth in the subclaims. The invention is not limited to the combination of features set forth in the claims.

[0026] The invention will now be explained in more detail using schematic illustrations: In the Figure 1 A means 1 for determining the actual torque value M_ist is shown schematically, which determines an actual value M_ist for torque M_ist from the motor current I and the angular position x. In the Figure 2 An alternative means 20 for determining the actual torque value M_ist is shown schematically, which determines an actual value M_ist for torque from the motor current I and the motor voltage U. In the Figure 3According to the invention, a speed controller element 30 is shown, from whose control value α_Soll, in particular from a setpoint α_Soll for angular acceleration, using the actual torque value M_ist, a torque setpoint M_Soll is determined, which is specified to a motor control, which provides an electric motor 33 with a motor voltage U. In the Figure 4 An exemplary speed controller for determining the torque setpoint M_Soll is shown, where a proportional element has the proportionality constant Kp1 and an integrating element has the characteristic parameter Tn1, and where the values ​​kp1 and Tn1 are selected such that a desired behavior, such as time constant and transient response characteristic, is present for a backlash-free drive train with a constant total moment of inertia. Figure 5 is in contrast to Figure 4the drive train is subject to play, i.e. looseness, and the proportionality constant Kp2 of the proportional element and the characteristic parameter Tn2 of the integrating element are selected in such a way that the behavior is as similar as possible to that of Figure 4 is present.

[0027] As shown in the figures, in a method for motor control according to the invention, an electric motor 33, which is preferably designed as a three-phase motor, is provided with a motor voltage U, in particular a three-phase voltage, by an inverter.

[0028] The angular position of a rotor shaft of the electric motor 33 is detected by means of a sensor and fed as actual value x_actual to a speed controller, which determines a value of a manipulated variable from the control deviation of the actual value x_actual to a setpoint value x_setpoint specified in particular as a parameter.

[0029] As in Figure 1As shown, the manipulated variable is preferably provided as a setpoint α_setpoint for angular acceleration.

[0030] This manipulated variable is fed to the means 31 for determining the torque setpoint M_Soll, which determines the torque setpoint M_Soll taking into account the actual torque value M_ist.

[0031] This is supplied to the motor control means 32 as a setpoint, wherein the motor control means 32 provides a motor voltage U to the electric motor 33 depending on this setpoint.

[0032] The angular position, i.e. angular position x, of the rotor of the electric motor 33 is detected by a sensor, from which the actual speed value w_ist is determined and the difference between the speed setpoint ω_setpoint and the actual speed value w_ist is fed as a control deviation to the speed controller element 30, which is preferably designed as a linear controller, such as a PI controller or PID controller.

[0033] To determine the torque setpoint M_Soll, the moment of inertia J_Last of the load driven by the electric motor 33 is first determined in the mean 31 according to J_Last = M_ist / dω_ist / dt − J_mot

[0034] Here, J_mot is the moment of inertia of the rotor of electric motor 33, known as a parameter of the electric motor, and dω_actual / dt is the time derivative of the angular velocity determined from the recorded angle values. Furthermore, the actual torque value M_actual is determined by means 1 for determining the actual torque value or by means 20 for determining the actual torque value.

[0035] From the determined moment of inertia J_Last and the moment of inertia J_Mot present as a parameter, the total moment of inertia J_ges, i.e. the total mass inertia, can be determined by summing J_ges = J_Mot + J_Last.

[0036] This is used to determine the torque setpoint M_Soll according to M_Soll = J_ges * α_Soll

[0037] Thus, the torque setpoint M_Setpoint is determined by simply multiplying the total moment of inertia J_ges with the manipulated variable α_Setpoint of the speed controller element 30.

[0038] According to the invention, the correct load inertia is always available for the control system because it can be adjusted during operation

[0039] In another embodiment, if in addition to the torque for accelerating the drive an additional torque occurs, such as load torque, i.e. a torque introduced into the drive train by the load, or a friction torque, two areas with different accelerations are used to determine the change ΔJ_Load of the moment of inertia according to: ΔJ_Last = M_ist_ 1 / dω_ist_ 1 / dt − M_ist_ 2 / dω_ist_ 2 / dt where dw_ist_1 / dt is the time derivative of the angular velocity, i.e. the angular acceleration, which lies in the first range, where M_ist_1 is the corresponding actual torque value, where dω_ist_2 / dt is the time derivative of the angular velocity, i.e. the angular acceleration, which lies in the second range, where M_ist_2 is the corresponding actual torque value.

[0040] The moment of inertia J_Mot of the rotor of the electric motor is constant, so that the change ΔJ_ges of the total moment of inertia J_ges corresponds to the change ΔJ_Last of the moment of inertia J_Last of the load.

[0041] The first range is a range of values ​​of the angular acceleration and the second range is another range of values ​​of the angular acceleration, whereby the two ranges do not overlap and are spaced from each other.

[0042] The determination of the actual torque value M_ist_1 and the angular acceleration dw_ist_1 / dt from the first range is carried out at a time interval from the determination of the actual torque value M_ist_2 and the angular acceleration dw_ist_2 / dt from the second range.

[0043] Thus, the moment of inertia J_Last can be tracked to the change.

[0044] For example, the drive accelerates a load in a first time period, resulting in a first acceleration value. In a subsequent time period, the motor speed is kept constant, and in a subsequent third time period, the load is decelerated, resulting in a second acceleration value. The second acceleration value may be equal to the first acceleration value.

[0045] Thus, from such a driving process, the moment of inertia J_Load of the load can be determined, whereby the influence of friction is eliminated.

[0046] In this way, the moment of inertia can be determined, and in particular, tracked, during operation of the system including the drive. Whenever the acceleration is in the first or second range, the respective quotient of the corresponding actual torque value and the angular acceleration can be updated.

[0047] Even if the load mass inertia changes during operation, the moment of inertia J_Load and thus the total moment of inertia of the drive train comprising the load and the rotor can be determined by updating.

[0048] The drive train is understood to mean the electric motor 33 fed by the converter together with the load driven by the electric motor 33, possibly via a gearbox.

[0049] In further embodiments according to the invention, the value curve of the load moment of inertia is further filtered in a suitable manner in order to reduce noise caused by noise in the measured variables.

[0050] As in Figure 4 As shown, the values ​​Kp1 and Tn1 are selected such that the desired behavior occurs when the drive train has no looseness, i.e., no play. The moment of inertia driven by the electric motor is J_total.

[0051] As in Figure 5 shown, other values ​​can be used which, in a drive train with looseness, i.e. with play, have the same behavior as in the version according to Figure 4 Here, Kp2 is used as the value of the proportionality constant of the proportional element, and Tn2 is used as the time constant of the integrating element.

[0052] In particular, stable control behavior can be achieved if Kp 2 = Kp 1 * J_Mot / J_Mot + J_Last Tn 2 = Tn 1 * J_Mot + J_Last / J_Mot

[0053] Applies.

[0054] The total moment of inertia J_ges is equal to the sum of J_Mot and J_Last, whereby the moment of inertia J_Mot relates to the rotatably mounted part of the drive train, which describes the rotor of the electric motor of the drive train up to the connection with play, in particular up to the looseness, of the drive train, and J_Last the remaining part of the drive train.

[0055] According to the invention, J_Last is determined and thus an adjustment of the values ​​is possible.

[0056] In further embodiments of the invention, values ​​are used according to Kp 2 = Kp 1 * f J_Mot , J_ges Tn 2 = Tn 1 * g J_Last , J_ges where f and g are functions.

[0057] Therefore, the separate determination of J_Last and J_Mot is necessary. For this purpose, J_Mot is determined in a first process step by determining J_Mot according to M_ist_1 / (dω_ist_1 / dt) when no load is present or not coupled to the rotor shaft of the electric motor of the drive train. In a second process step, the load moment of inertia J_Last is then determined according to M_ist_ 1 / dω_ist_ 1 / dt − M_ist_ 2 / dω_ist_ 2 / dt

[0058] Subsequent changes in the load moment of inertia J_Last can then be determined accordingly in further process steps, i.e. the value of the load moment of inertia J_Last can be tracked.

[0059] In further embodiments of the invention, values ​​are used according to Kp 2 = Kp 1 * f J_Last , J_ges Tn 2 = Tn 1 * g J_Mot , J_ges where f and g are functions.

[0060] Therefore, the separate determination of J_Last and J_Mot is necessary. For this purpose, J_Mot is determined in a first process step by determining J_Mot according to M_ist_1 / (dω_ist_1 / dt) when no load is present or not coupled to the rotor shaft of the electric motor of the drive train. In a second process step, the load moment of inertia J_Last is then determined according to M_ist_ 1 / dω_ist_ 1 / dt − M_ist_ 2 / dω_ist_ 2 / dt

[0061] Subsequent changes in the load moment of inertia J_Last can then be determined accordingly in further process steps, i.e. the value of the load moment of inertia J_Last can be tracked.

[0062] In further embodiments of the invention, values ​​are used according to Kp 2 = Kp 1 * f J_Mot × J_Last Tn 2 = Tn 1 * g J_Mot × J_Last where f and g are functions and thus depend on the product of the two moments of inertia.

[0063] Therefore, the separate determination of J_Last and J_Mot is necessary. For this purpose, J_Mot is determined in a first process step by determining J_Mot according to M_ist_1 / (dω_ist_1 / dt) when no load is present or not coupled to the rotor shaft of the electric motor of the drive train. In a second process step, the load moment of inertia J_Last is then determined according to M_ist_ 1 / dω_ist_ 1 / dt − M_ist_ 2 / dω_ist_ 2 / dt

[0064] Subsequent changes in the load moment of inertia J_Last can then be determined accordingly in further process steps, i.e. the value of the load moment of inertia J_Last can be tracked. List of reference symbols

[0065] 1 Means for determining the actual torque value 20 Means for determining the actual torque value 30 Speed ​​controller 31 Means for determining the torque setpoint 32 Motor control means 33 Electric motor, in particular three-phase motor I Motor current, in particular motor current space vector U Motor voltage, in particular motor voltage space vector X Angular position ω_actual Actual value of the angular velocity ω_setpoint Setpoint of the angular velocity α_setpoint Setpoint for angular acceleration M_actual Actual value of the torque

Claims

1. Method for operating a drivetrain, the drivetrain having an electric motor (33) and a load that is driven by the electric motor (33) or driven by a gearing driven by the electric motor (33), a sensor for detecting the angular position of a rotor of the electric motor (33) being provided, in particular being arranged on the electric motor (33), a motor voltage being made available to the electric motor (33) by means of the converter, in particular by means of a motor commutation means (32) of the converter, in order to achieve a desired torque value M_Soll, an actual angular velocity value w_ist and an actual angular acceleration value α_ist being determined, in particular recurrently over time, from the values of the angular position of the rotor that are detected by means of the sensor, the desired torque value M_Soll being determined from a moment of inertia J_ges and a desired angular acceleration value α_Soll, the desired angular acceleration value α_Soll being determined as a manipulated variable by a speed controller member (30), to which the difference, in particular the control error, between the actual angular velocity value w_ist and the desired angular velocity value w_Soll is supplied, the moment of inertia J_ges being determined as the sum of the moment of inertia J_Mot of the drivetrain without a load and the moment of inertia J_Last of the load, the moment of inertia J_Last of the load being determined from an actual torque value M_ist and the actual angular acceleration value α_ist, in particular while taking into account the moment of inertia J_Mot, characterised in that the speed controller member (30) is configured as a PI controller, said controller member having a proportional control unit and an integrator wired in parallel with the proportional control unit, the proportionality constant of the proportional control unit being a function of the product of the moment of inertia J_Mot and the moment of inertia J_Last of the load, and / or the time constant of the integrator being a function of the product of the moment of inertia J_Mot and the moment of inertia J_Last of the load.

2. Method according to claim 1, characterised in that the actual torque value M_ist is determined from the motor current detected by means of a current sensor and the detected values of the angular position x of the rotor, or in that the actual torque value M_ist is determined from the motor current detected by means of a current sensor and the detected motor voltage U and / or the detected values of the angular position x of the rotor.

3. Method according to any of the preceding claims, characterised in that the moment of inertia J_Mot of the drivetrain without a load is specified as a parameter.

4. Method according to any of the preceding claims, characterised in that the desired torque value M_Soll is formed as a product of the moment of inertia J_ges and the desired angular acceleration value α_Soll.

5. Method according to any of the preceding claims, characterised in that the moment of inertia J_Last of the load is determined as a ratio of the actual torque value M_ist and the actual angular acceleration value α_ist minus the moment of inertia J_Mot.

6. Method according to any of claims 1 to 5, characterised in that the speed controller member (30) is configured as a PI controller, said controller member having a proportional control unit and an integrator wired in parallel with the proportional control unit, the proportionality constant of the proportional control unit element being a function of the moment of inertia J_Mot and the total moment of inertia J_ges, the time constant of the integrator being a function of the moment of inertia J_Mot and the total moment of inertia J_ges.

7. Method according to any of claims 1 to 5, characterised in that the speed controller member (30) is configured as a PI controller, said controller member having a proportional control unit and an integrator wired in parallel with the proportional control unit, the proportionality constant of the proportional control unit being a function of the moment of inertia J_Last and the total moment of inertia J_ges, the time constant of the integrator being a function of the moment of inertia J_Mot and the total moment of inertia J_ges.

8. Method according to any of claims 1 to 7, characterised in that at a first time, the moment of inertia J_Last of the load is determined as a first ratio of the actual torque value M_ist and the actual angular acceleration value α_ist minus the moment of inertia J_Mot, the actual angular acceleration value α_ist being in a first value range, after the first time, at a second time, the moment of inertia J_Last of the load being determined as a second ratio of the actual torque value M_ist and the actual angular acceleration value α_ist minus the moment of inertia J_Mot, the actual angular acceleration value α_ist being in a second value range, an updated moment of inertia J_Last being determined by adding the difference between the second and first ratios to the previously determined value of the moment of inertia J_Last.

9. Method according to claim 8, characterised in that the first range is an angular acceleration value range and the second range is a different angular acceleration value range, the two value ranges not overlapping with one another but being separate from one another.

10. Method according to any of the preceding claims, characterised in that each determined value, in particular of the moment of inertia J_Last of the load, is filtered, in particular low-pass filtered.

11. Drivetrain configured to carry out a method according to any of the preceding claims.