Method of monitoring a machine

Abstract

A method of monitoring a machine is described. The machine includes a mechanical system moved by a motor, where the mechanical system has more than two components coupled to each other. The two or more components move differently when the mechanical system is driven by the motor. The method includes repeatedly determining one movement factor of one of the components, and repeatedly determining one dynamic factor of one of the components. The movement factors of the remaining components are then calculated via a model of the mechanical system, and separate parameters for the components of the mechanical system are determined from the movement factor, the dynamic factor, and the calculated movement factors.

Claims

1. A method of monitoring a machine in which a mechanical system is moved by a motor, wherein the mechanical system comprises more than two components coupled to one another, wherein one of the components comprises the motor, wherein at least two of the components move differently when the motor drives the mechanical system, and wherein at least one movement factor of one of the components of the mechanical system is determined repeatedly; at least one dynamic factor of one of the components of the mechanical system is determined repeatedly; the movement factors of the remaining components of the mechanical system are calculated by means of a model of the mechanical system; and separate mechanical parameters for the components of the mechanical system are determined from the determined movement factor, from the determined dynamic factor and from the calculated movement factors.

2. The method in accordance with claim 1, wherein a plurality of values of the determined movement factor and/or of the determined dynamic factor are used to determine the mechanical parameters for the components of the mechanical system.

3. The method in accordance with claim 1, wherein an equation system having a plurality of equations is set up and solved to determine the mechanical parameters.

4. The method in accordance with claim 3, wherein the equation system is having one equation per value of the determined movement factor.

5. The method in accordance with claim 1, wherein the movement factor comprises a speed; a position; an acceleration; an angular speed; an angular position; and/or an angular acceleration.

6. The method in accordance with claim 1, wherein the model of the mechanical system comprises at least one transfer function (x.sub.1, x.sub.2) which describes the movement of a first component in dependence on the movement of a second component which is coupled to the first component.

7. The method in accordance with claim 6, wherein the movement factors are each multiplied by a derivative of the transfer function which describes the movement of the respective component.

8. The method in accordance with claim 1, wherein the mechanical parameters comprise a torque; and/or a force; and/or a parameter for calculating a torque or a force.

9. The method in accordance with claim 8, wherein the parameter for calculating the torque or the force is based on an acceleration or a speed.

10. The method in accordance with claim 1, wherein the method is carried out separately several times, in particular twice, to determine mechanical parameters for different directions of movement of a component.

11. The method in accordance with claim 10, wherein the method is carried out separately twice, to determine mechanical parameters for different directions of movement of a component.

12. The method in accordance with claim 1, wherein the determined movement factor and/or the determined dynamic factor is/are measured and/or calculated from a measured value.

13. The method in accordance with claim 12, wherein the determined movement factor and/or the determined dynamic factor is/are measured and/or calculated from a motor torque.

14. The method in accordance with claim 1, wherein a new determination of the mechanical parameters takes place when the determined movement factor and/or the determined dynamic factor changes/change, for example by more than 10% or by more than 15%.

15. The method in accordance with claim 1, wherein the model of the mechanical system comprises a digital twin.

16. The method in accordance with claim 1, wherein a value for at least one mechanical parameter is determined several times and a final value for the mechanical parameter is calculated from the plurality of values.

17. The method in accordance with claim 1, wherein a change of the control of the motor takes place on the basis of at least one of the mechanical parameters.

18. The method in accordance with claim 1, wherein a predictive maintenance of the machine is carried out on the basis of at least one mechanical parameter.

19. An industrial machine having a mechanical system which comprises a motor and at least two further components, wherein the components are coupled to one another, wherein at least the two components move differently when the motor drives the mechanical system, and wherein the machine comprises at least one sensor and a processing device and is designed to repeatedly determine at least one movement factor of one of the components of the mechanical system; to repeatedly determine at least one dynamic factor of one of the components of the mechanical system; to calculate the movement factors of the remaining components of the mechanical system by means of a model of the mechanical system; and to determine separate mechanical parameters for the components of the mechanical system from the determined movement factor, from the determined dynamic factor and from the calculated movement factors.

Description

(1) The invention will be described purely by way of example with reference to the drawings. There are shown:

(2) FIG. 1: the schematic design of a machine; and

(3) FIG. 2: a matrix equation system for determining mechanical parameters of the machine.

(4) FIG. 1 shows a machine 10 which comprises a motor 12; a gear 14 coupled to the motor 12; a first cam disk 16; and a second cam disk 18. The gear 14 drives the cam disks 16, 18 in a rotational manner by means of a drive shaft 20.

(5) The first cam disk 16 in turn moves a first weight 22 and the second cam disk 18 moves a second weight 24. Both weights 22, 24 are moved in a translational manner and against gravity.

(6) The combination of the motor 12, the gear 14, the drive shaft 20 and the cam disks 16, 18 will be considered as the first component K1 of the machine 10 in the following. The first weight 22 is a second component K2 and the second weight 24 is a third component K3 of the machine 10.

(7) The design of the machine 10 shown here is to be understood purely by way of example and only serves to illustrate the method of calculating the mechanical parameters. In general, mechanical parameters of machines of any desired design, in particular also of complex machines, can be determined with the specified approach.

(8) The motor 12 is controlled by a control unit 25. The control unit 25 has the effect that the motor 12 delivers different rotational speeds and torques to the drive shaft 20 over time. The rotation of the drive shaft 20 which is variable in time is indicated by the function φ.sub.K1 in FIG. 1.

(9) The control unit 25 measures a current consumed by the motor 12 and from this calculates the torque delivered by the motor 12 to the drive shaft 20 in each case. In addition, the control unit 25 measures (e.g. via an encoder not shown) the respective instantaneous angular position of the motor shaft of the motor 12. The control unit 25 then calculates an angular speed and an angular acceleration of the motor 12 and/or of the drive shaft 20 from the change of the angular position over time.

(10) A model of the mechanical system of the machine 10 is kept available in the control unit 25 or also in an external system not shown here. By means of the model, it is possible to draw a conclusion on the respective angular position of the cam disks 16, 18 from the respective angular position of the motor 12 on the basis of a known gear ratio. The position, the speed and the acceleration of the weights 22, 24 can then be calculated from the angular position of the cam disks 16, 18. The calculation takes place for the first weight 22 by means of a transfer function x.sub.K2(φ.sub.K1) and for the second weight 24 by means of a transfer function x.sub.K3(φ.sub.K1). The input quantity/factor for the transfer functions x.sub.K2, x.sub.K3 is the rotation of the drive shaft 20, i.e. the function (φ.sub.K1, in each case.

(11) FIG. 2 shows a matrix equation system 26. The matrix equation system 26 comprises a matrix 28 which is multiplied by a first vector 30. This multiplication results in a second vector 32.

(12) In a respective row of the matrix 28, respective measured values or values determined therefrom are entered for the same point in time. The first three values (W1, W2, W3) of each row relate to the first component K1 in this respect.

(13) The values 4-6 (W4, W5, W6) of each row relate to the movement of the first weight 22 (i.e. of the second component K2), whereas the values 7-9 (W7, W8, W9) relate to the movement of the second weight 24 and thus to the third component K3.

(14) The values belonging to the first component K1 are marked as the first region 34 in the matrix 28. Accordingly, the values belonging to the first weight 22 are marked as the second region 36 and the values belonging to the second weight 24 are marked as the third region 38.

(15) The first value W1 of each row defines the angular acceleration α for the rotation of the drive shaft 20. The second value W2 is the angular speed ω for the rotation of the drive shaft 20. The third value W3 is constant 1.

(16) The fourth and seventh values W4, W7 each indicate an acceleration acc of one of the weights 22, 24 which is multiplied by a derivative of the transfer function

(17) $\left(e.g.\frac{d{x}_{K2,t1}}{d{\phi }_{K1,t1}}\right).$
The fifth and eighth values W5, W8 each indicate a speed vel of the first weight 22 or of the second weight 24 which is likewise multiplied by a derivative of the transfer function. Finally, the sixth and ninth values W6, W9 of each row only indicate the derivative of the transfer function for the first weight 22 and the second weight 24 respectively.

(18) The mechanical parameters to be determined, i.e. the unknowns of the matrix equation system 26, are included in the vector 30. The first variable of the vector 30 represents a moment of inertia J.sub.K1 of the first component. The second variable of the vector 30 is a parameter k.sub.Mvel,K1 which indicates a torque dependent on the rotational speed. The third variable indicates a static torque k.sub.Mstat,K1 (for example due to friction). The first three variables thus describe the first component K1.

(19) The fourth to sixth variables of the first vector 30 describe the first weight 22 or its movement behavior. The fourth variable represents the mass m.sub.K2 of the first weight 22, the fifth variable describes a speed-dependent force k.sub.Fvel,K2 and the sixth variable describes a static force k.sub.Fstat,K2 which is generated by the first weight 22.

(20) In a corresponding manner, the seventh variable describes the mass m.sub.K3 of the second weight 24, the eighth variable describes a speed-dependent force k.sub.Fvel,K3 and the ninth variable describes a constant force k.sub.Fconst,K3. Accordingly, the variables 1-3 are associated with the first region 34, the variables 4-6 are associated with the second region 36 and the variables 7-9 are associated with the third region 38.

(21) In the second vector 32, the torques M.sub.t1 to M.sub.tn that are introduced by the motor 12 and measured at a point in time (t1, t2, . . . , tn) represented in a respective row are indicated for this point in time.

(22) An equation with nine unknowns (the nine variables of the first vector 30) results for each row of the matrix 28 when the matrix equation system 26 is solved. The remaining values were either measured or calculated using the model of the mechanical system, as stated above.

(23) The matrix equation system 26 can be unambiguously solved by the multiplication of both sides of the matrix equation system 26 by the transpose of the matrix 28.

(24) For example, more than 1000 or more than 10,000 measurements are in particular carried out at a large number of points in time, e.g. within one machine cycle or within a plurality of machine cycles. A row is generated in the matrix equation system 26 for each measurement, wherein the values measured or calculated at the respective point in time are entered in the row. Accordingly, the matrix 28 and thus also the second vector 32 can comprise more than 1000 or more than 10,000 rows.

(25) In this way, a statement can be made on the mechanical parameters of all the components of the machine 10 solely by the measurement of the torque generated by the motor 12 and by the measurement of the position of the motor 12. The motor 12 together with the control unit 25 thus serves as the only measurement device. The movement factors summarized in the matrix 28 can be determined at any point in time by the measurements of the motor 12, whereby the mechanical parameters 30 can then in turn be determined. The behavior of the mechanical system of the machine can be predicted by the mechanical parameters, whereby a feedforward control of the motor 12 can take place. The running properties of the machine 10 can hereby be considerably improved. In addition, smaller/lighter motors 12 can e.g. be used than is customary so that costs for the motor 12 and also the energy consumption for the operation of the machine 10 can be considerably reduced.

(26) In addition, there is the advantage that the mechanical parameters 30 are each associated with a defined component so that e.g. the component at which an increased friction currently occurs can also e.g. be recognized in complex drive trains, among other things, in ongoing operation solely by the measurement at the motor 12. This component can then e.g. be maintained in a targeted manner, whereby the work of maintenance personnel is simplified. It is thus possible, in particular in the operating phase of a machine 10, to compare the desired behavior of the machine 10 in accordance with the machine design with the real/current behavior at any time to recognize deviations and to introduce targeted counter-measures, e.g. in real time, by a feedfoward control of the drive torque of the motor 12.

REFERENCE NUMERAL LIST

(27) 10 machine 12 motor 14 gear 16 first cam disk 18 second cam disk 20 drive shaft 22 first weight 24 second weight 25 control unit 26 matrix equation system 28 matrix 30 first vector 32 second vector 34 first region 36 second region 38 third region φ.sub.K1 function of the rotation of the drive shaft x.sub.K2(φ.sub.K1) first transfer function x.sub.K3(φ.sub.K1) second transfer function K1 first component K2 second component K3 third component W1-W9 first to ninth value