Attenuation of load oscillations without additional measuring means on the load side

Abstract

A method for attenuating load oscillations in a load mechanism having a controlled drive, wherein a load is coupled mechanically to a motor via a spring element, includes determining an actual motor torque value, determining an actual angular velocity value, determining a motor inertial torque, calculating a spring torque from the actual angular velocity value, the motor inertial torque and the actual motor torque value, and supplying the calculated spring torque to an attenuator connection for attenuating the load oscillations.

Claims

1. A method for attenuating load oscillations in a load mechanism having a controlled drive, wherein a load is coupled mechanically to a motor via a spring element, said method comprising: determining an actual motor torque value of the motor; determining an actual angular velocity value of the motor; determining a motor inertial torque; calculating a spring torque of the spring element by subtracting from a second intermediate value derived from the determined actual motor torque value, a first intermediate value derived from a product of the motor inertial torque and a first order time-derivative of the actual angular velocity value; supplying the calculated spring torque to an attenuator connection for attenuating the load oscillations; and attenuating the load oscillations using the calculated spring torque.

2. The method of claim 1, wherein the actual angular velocity value is derived from an actual angular position value which is measured or determined by a sensor and/or a measurement system.

3. The method of claim 1, wherein the load mechanism additionally comprises a motor model with a current controller, which is connected upstream of the controlled drive, and the method further comprising determining the motor torque value, in particular the actual motor torque value from a measured motor current and the motor model.

4. The method of claim 1, wherein the load mechanism additionally comprises a motor model with a current controller, which is connected upstream of the controlled drive, and further comprising calculating the actual angular velocity value from the motor model operating without sensors.

5. The method of claim 1, further comprising supplying the motor torque value, in particular the actual motor torque value, to a filter, in particular a smoothing filter, to form the second intermediate value.

6. The method of claim 1, wherein the attenuator connection comprises at least two attenuator passages, and further comprising: determining a third intermediate value by multiplying the determined actual angular velocity value with the motor inertial torque, followed by high-pass filtering; determining a fourth intermediate value by integrating the determined motor torque value, in particular the determined actual motor torque value, without an offset; determining an integral spring torque by supplying the third intermediate value and the fourth intermediate value to a second subtractor; and supplying the determined integral spring torque to a second of the at least two attenuator passages.

7. The method of claim 1, wherein the attenuator connection comprises an Advanced Position Control (APC) system and the calculated spring torque is supplied to the APC.

8. The method of claim 1, wherein the attenuator connection comprises at least one first attenuator passage for determining at least one attenuation frequency having a natural frequency for attenuating at least one load oscillation, in particular by way of a negative-feedback connection to a predetermined angular velocity required value.

9. The method of claim 8, further comprising supplying at least the calculated spring torque to the at least one first attenuator passage, wherein the at least one first attenuator passage has an input side with at least one first bandpass.

10. A device for attenuating load oscillations, comprising: a load mechanism having a controlled drive comprising a motor and a spring element, wherein a load is coupled mechanically to the motor via the spring element, said device being configured to determine an actual motor torque value of the motor, determine an actual angular velocity value of the motor, determine a motor inertial torque, calculate a spring torque of the spring element by subtracting from a second intermediate value derived form the determined actual motor torque value, a first intermediate value derived from a ;product of the motor inertial torque and a first order time-derivative of the actual angular velocity value; and supply the calculated spring torque to an attenuator connection for attenuating the load oscillations.

11. The device of claim 10, further comprising a sensor and/or a measurement system providing an actual angular position value, from which the actual angular velocity value is derived.

12. The device of claim 10, wherein the load mechanism additionally comprises a motor mod& with a current controller, which is connected upstream of the controlled drive, wherein the motor torque value, in particular the actual motor torque value is determined from a measured motor current and the motor model.

13. The device of claim 10, further comprising a filter, in particular a filter performing a smoothing function, which receives the motor torque value, in particular the actual motor torque value, and forms the second intermediate value.

14. The device of claim 10, wherein the attenuator connection comprises an Advanced Position Control (APC) system and wherein the calculated spring torque is supplied to the APC.

15. The device of claim 10, wherein the attenuator connection comprises at least one first attenuator passage for determining at least one attenuation frequency having a natural frequency for attenuating at least one load oscillation, in particular by way of a negative-feedback connection to a predetermined angular velocity required value.

16. The device of claim 15, wherein the at least one first attenuator passage comprises at least one first bandpass having an input side configured to receive at least the calculated spring torque.

17. The device of claim 10, wherein the load mechanism further comprises a motor model with a current controller, which is connected upstream of the controlled drive, wherein the motor model is configured to calculate the motor torque value, in particular the actual motor torque value without employing sensors.

18. The device of claim 10, wherein the attenuator connection comprises at least two attenuator passages, said device being configured to: determine a third intermediate value by multiplying the determined actual angular velocity value with the motor inertial torque, followed by high-pass filtering, determine a fourth intermediate value by integrating the determined motor torque value, in particular the determined actual motor torque value, without an offset, determine an integral spring torque by supplying the third intermediate value and the fourth intermediate value to a second subtractor, and supply the integral spring torque to a second attenuator passage.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Further features, characteristics and advantages of the present invention emerge from the description given below, which refers to the enclosed figures. In the figures, in schematic diagrams:

(2) FIG. 1 shows a first drive configuration with motor and load,

(3) FIG. 2 shows a second drive configuration with motor and load,

(4) FIG. 3 shows a block diagram of a control path for a dominant natural frequency,

(5) FIG. 4 shows a first graphic functional representation of a device for carrying out the inventive method in a controlled drive,

(6) FIG. 5 shows a second graphic functional representation of a device for carrying out the inventive method in a controlled drive,

(7) FIG. 6 shows a result of an example with inventive attenuation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(8) Although the invention has been illustrated and described in greater detail by the preferred exemplary embodiments, the invention is not restricted by the disclosed examples. Variations herefrom can be derived by the person skilled in the art, without departing from the scope of the invention, as is defined by the claims given below.

(9) Shown in greater detail in FIG. 4 is a drive control device 30 of a controlled drive 32 with motor 6 and load 2, wherein parts of this drive control device 30 are presented in greater detail. A commercially-available drive control device 30 has a final control element 34, for example a power converter, in particular a self-commutated pulse-controlled inverter, and a closed-loop controller 36. This closed-loop controller 36 consists for example of a motor model with current controller 38, a speed control circuit 40 and a position control circuit 42. These control circuits 38,40 and 42 form a control attenuator passage. I.e. the position control circuit 42 is higher-ranking than the speed control circuit 40 and the speed control circuit 40 is higher-ranking than the motor model with current controller 38. The control circuits 38 and 42 are not specified in detail here, since these circuits are not needed for understanding the invention.

(10) In addition this drive control device 30 has an attenuator connection 44, which is connected on its output side by means of an adder 46 to an angular velocity required value .sub.Lsoll. In this case this angular velocity required value .sub.Lsoll is present at a non-inverting input and the attenuator connection 44 is linked on its output side to the inverting input of the adder 46. Through this the output signal Df.sub.all of the attenuator connection 44 is connected with negative feedback to the angular velocity required value .sub.Lsoll.

(11) The speed control circuit 40 has on its input side a comparator 48 and on its output side a controller 50. This controller 50 is linked on its input side to an output of the comparator 48. By means of this comparator 48 a control deviation, here the deviation .sub.e, of an angular velocity actual value .sub.List from a predetermined angular velocity required value .sub.Msoll is determined. By means of the controller 50 a final control variable is created, which is characterized so that the control deviation .sub.e becomes zero. Thus the angular velocity actual value .sub.Mist is adjusted to the angular velocity required value .sub.Lsoll. With a speed control circuit 40 a motor torque required value M.sub.soll is obtained as a final control value of the controller 50, to which for example a noise torque M.sub.z, e.g. cogging, is connected by means of an adder 52. Thus a modified motor torque required value M.sub.soll is present at the output of this adder 52, which is connected by means of a filter 54 to an input of the subordinate motor model with current controller 38.

(12) On the input side, in accordance with the invention, the attenuator connection 44 is now supplied with the current spring torque M.sub.F for attenuation.

(13) In accordance with the invention it has been recognized that the spring torque M.sub.F thus represents one of two components, which leads to load acceleration. It has been recognized in this case that the spring torque M.sub.F is produced by the following equation:
M.sub.F=M.sub.istJ.sub.M*d.sub.Mist/dt(1)
wherein .sub.Mist=angular velocity actual value J.sub.M=motor inertial torque M.sub.ist=motor torque actual value.

(14) The spring torque M.sub.F takes care of the acceleration of the load side. Likewise the context for the load acceleration d.sub.Mist/dt has been recognized:
d.sub.Mist/dt+M.sub.FM.sub.L(2)

(15) The spring torque M.sub.F thus represents one of two components, which leads to load acceleration d.sub.Mist/dt. The spring torque M.sub.F contains the portion of the load acceleration that leads to oscillation, while the load torque portion M.sub.L is normally independent of the oscillation. This enables the spring torque M.sub.F according to (1) to be included for load oscillation attenuation. Only the motor torque value, in particular the motor torque actual value M.sub.ist, the angular velocity actual value .sub.Mist and the motor inertial torque J.sub.M are necessary as input variables, which are usually known or are present as calculated variables or as measured variables.

(16) A sensor or a measurement system measures the angular actual value .sub.Mist from which the angular velocity actual value .sub.Mist is determined. This means that the motor speed is known. It also has been created with a generatorless motor model, so that not even a motor generator is absolutely necessary. Naturally fewer dynamic model actual values can be used just for attenuation for corresponding lower frequencies. This is now multiplied by the motor inertial torque J.sub.M by means of a multiplier 80. Subsequently the result is differentiated to form a first intermediate result ZW.sub.1 differentiated according to time t (differentiator 81). Of course there can also first be differentiation according to time t and then multiplication by the motor inertial torque J.sub.M, since the motor inertial torque J.sub.M is a constant.

(17) In addition the motor torque value, in particular the motor torque actual value M.sub.ist, is determined from the motor model with current controller 38 and from the measured current. In generatorless operation the angular velocity actual value .sub.Mist is also determined from the motor model, but is normally delayed in relation to a measured value. This does not apply however to the motor torque value, in particular the motor torque actual value M.sub.ist, which is present barely delayed, even in generatorless operation. This is supplied to a smoothing filter 82, i.e. a filter with a smoothing function, for forming a second intermediate value ZW.sub.2. Of course all other suitable filters can be employed.

(18) The intermediate values formed, ZW.sub.1 and ZW.sub.2, are now supplied to a subtractor 83. There the first intermediate value ZW.sub.1 is subtracted from the second intermediate value ZW.sub.2 and thereby the spring torque M.sub.F is formed. This is now supplied to the attenuator connection 44. In this case the attenuator connection 44 consists of at least one or more attenuator passages 56.sub.1 and 56.sub.2. Two attenuator passages 56.sub.1 and 56.sub.2 are shown here, which are linked on the output side by means of a further adder 60.

(19) The attenuator passages 56.sub.1 or 56.sub.2 have a bandpass 62.sub.1 or 62.sub.2 on their input side, downstream of which a filter 64.sub.1 or 64.sub.2 is connected, and on their output side an amplifier 66.sub.1 or 66.sub.2, which is linked on its input side to an output of the filter 64.sub.1 or 64.sub.2. The amplifier 66.sub.1 or 66.sub.2 is also connected to an adjustable factor 68.sub.1 or 68.sub.2. Two natural frequencies f.sub.1 and f.sub.2 of the low-frequency load oscillations are to be attenuated by means of this attenuator connection 44, wherein these two natural frequencies f.sub.1 and f.sub.2 are to be attenuated differently, since the amplifiers 66.sub.1 or 66.sub.2 are supplied in each case with different amplification factors K1 and K2. An output signal Df.sub.1 and Df.sub.2 of the attenuator passages 56.sub.1 and 56.sub.2 is present at the output of each of the amplifiers 66.sub.1 or 66.sub.2. These output signals D.sub.f1 and D.sub.f2 of the attenuator passages 56.sub.1 and 56.sub.2 are combined by means of the adder 60 into the output signal Df.sub.all of the attenuator connection 44.

(20) The low-frequency load oscillations occurring in the controlled drive 32 are measured. In this case, in the example shown, only two natural frequencies f.sub.1 and f.sub.2 are isolated from the low-frequency load oscillations. A bandpass filtered signal Df.sub.1_0 or Df.sub.2_0 is present at the output of the bandpass 62.sub.1 or 62.sub.2. During commissioning here at least the natural frequencies f.sub.1 and f.sub.2 of the low-frequency oscillations occurring are measured. On the basis of these measurements at least one bandpass 62.sub.1 of an attenuator passage 56.sub.1 of the attenuator connection 44 is adjusted so that only one natural frequency f.sub.1 of the load oscillation is allowed to pass through. A bandpass filtered signal with the natural frequency f.sub.1 is obtained at the output of this bandpass 61.sub.1. Depending on the natural frequency f.sub.1 and the degree of attenuation, the amplification factor K1 is selected accordingly. The same applies for the frequency f.sub.2. Through the negative-feedback connection of the output signal Df.sub.all of the attenuator connection 44, the natural frequency f.sub.1, f.sub.2 of the low-frequency load oscillation is attenuated.

(21) The spring torque M.sub.F is created smoothed here in accordance with the invention, since a smoothing is sensible for differentiation, in order to remove the noise. With a bandpass 62.sub.1,2 the frequency ranges are selected in which the attenuation is to act, in order to avoid feedback to other frequency ranges, because for example even further natural frequencies are present, which can be aroused by the attenuation. The invention has been trialed successfullyas described in FIG. 6.

(22) FIG. 5 shows a further exemplary embodiment. Here too the attenuator connection 44 is embodied with two attenuator passages 56.sub.1,2. The second attenuator passage 56.sub.2 can now be supplied not with the spring torque M.sub.F calculated above, but with the speed M.sub.F. This is achieved in that, for determining a third intermediate value ZW.sub.3, the established angular velocity actual value .sub.Mist is multiplied by the motor inertial torque J.sub.M and is subsequently supplied to a highpass filter 91. In addition for determining a fourth intermediate value ZW.sub.4, the established motor torque value, in particular of the established motor torque actual value M.sub.ist is integrated without offset. To determine the integral spring torque M.sub.F the third intermediate value ZW.sub.3 and the fourth intermediate value ZW.sub.4 are then supplied to a subtractor 93. This is now supplied to the second attenuator passage 44.

(23) The second attenuator passage here therefore does not need the spring torque M.sub.F (=acceleration) but a speed, i.e. the integral of the spring torque M.sub.F with a downstream highpass. Because the differentiator and the integrator cancel each other out, the structure can also be redrafted and the smoothing during differentiation can be omitted.

(24) FIG. 6 shows a result of a simulation of FIG. 4 with a 3-mass oscillator, wherein the lower natural frequency is to be attenuated with this method. At the beginning a speed required value jump to 10 l/s is carried out and at 0.3 s a spring-type load torque of 2 Nm is connected. The angular velocity actual value .sub.Mist has the number 100 here. The angular velocity required value .sub.Lsoll has the number 101 here, the signal Df.sub.all, i.e. the attenuation connection value, has the number 102 here, the load torque M.sub.F has the number 103, the motor torque actual value M.sub.ist has the number 104 and the (actual) spring torque M.sub.F is calculated as 105. In the simulation the natural oscillations do not have any natural attenuation. The controller provides good attenuation both in management behavior and also in load behavior. The attenuation is also effective without changing the setting if the natural frequencies of the path change.

(25) The advantage of this invention is that load oscillations can be attenuated without having to operate an additional measuring device. Moreover this solution, by comparison with other solutions for example, is more robust, because it only accesses existing measurement variables and the invariable motor inertial torque J.sub.M. The load characteristics (spring stiffness, load inertia) no longer play any role. Naturally the path influences the natural frequency and thus also the optimum setting of the feedback amplification and of the bandpass, robust settings can be selected here however, since the attenuation effect is maintained even with a non-optimum setting, even though not quite as strong. The invention can be used in particular in conjunction with the APC system, and can also be employed with other systems.