Method for Controlling a Casting Process, Control System for a Casting Process, Apparatus and Computer Program

Abstract

A method for controlling, in particular for temperature control, a casting process, in particular a gravity die casting process, including control of at least one input variable indicative of at least one input variable of the casting process, in particular as a function of at least one output variable indicative of at least one temperature of the casting process, in particular for a temperature of a casting mould. A temperature difference between the temperature of the casting process and a preset temperature profile is minimized. The control of the at least one input variable is based on a model predictive control. The present invention also relates to a control system for a casting process, in particular for a permanent mold casting process, a device including at least one processor and at least one memory as well as a computer program including program instructions.

Claims

1-14. (canceled)

15. A method for controlling, in particular for temperature controlling, a casting process, in particular a permanent mold casting process, comprising control of at least one input variable indicative of at least one input value of the casting process depending on at least one output variable indicative of at least one temperature of the casting process, in particular of a temperature of a casting mould, in such a way that a temperature difference between the temperature of the casting process and a preset temperature profile is minimized, wherein the control of the at least one input variable is based on a model predictive control, wherein the model predictive control comprises a model, in particular a dynamic model, wherein the model is identified and/or adapted on the basis of a data set, the data set having data indicative of the at least one input variable and the at least one output variable, and wherein a correlation between the at least one input variable and the at least one output variable is determined by means of the model based on the data set, wherein the at least one input variable is a flow rate of a coolant, a temperature of a coolant, a duration of a casting cycle, a quantity of a mold filling, a composition of a mold filling, a temperature of a mold filling, a time of a mold filling, a temperature of a heating source and/or a heating rate of a heating source, wherein the data set comprises historical data, in particular data from casting tests already carried out and/or data from series production, the data set being extended by data recorded during the carrying out of the casting process, the model predictive control comprises a Kalman filter, and the state of the casting process, in particular the system state and the state of the at least one output variable, is calculated by means of the Kalman filter model, in particular at defined time intervals, and the model-predictive control further takes into account a filling of the mold as a measured disturbance variable and the correlation of the disturbance variable to the at least one input variable and/or the at least one output variable based on the dynamic model, the model predictive control predicts different trajectories of the at least one output variable by means of the state calculated by the Kalman filter model, and the model predictive control is used to control the at least one input variable in such a way that a predicted trajectory of the output variable is set which is indicative of a minimum temperature difference between the temperature of the casting process and the preset temperature profile.

16. The method according to claim 15, wherein and/or the model is parameterized by means of estimated values, wherein the model preferably is validated and/or extended by recorded data during the carrying out of the casting process.

17. The method according to claim 15, wherein the model-predictive control takes into account the at least one input variable and the one output variable as well as their correlation to each other based on the model.

18. The method according to claim 15, wherein the model predictive control takes into account limitations of the casting process, in particular limitations of the at least one input variable and/or the at least one output variable.

19. The method according to claim 15, wherein the at least one output variable is indicative of at least one temperature of the casting process detected by means of a thermocouple, in particular by means of a thermocouple arranged at least partially inside a casting mold.

20. A control system for a casting process, in particular for a permanent mold casting process, comprising: at least one control means for controlling at least one input variable indicative of at least one input value of the casting process depending on at least one output variable indicative of at least one temperature of the casting process, in particular of a temperature of a casting mould, in such a way that a temperature difference between the temperature of the casting process and a preset temperature profile is minimized, wherein the control means regulates the at least one input variable based on a model predictive control, and the control system is designed to carry out a method according to claim 15.

21. A device comprising at least one processor and at least one memory containing program code, wherein the memory and the program code are arranged to cause a device with the at least one processor to execute and/or control at least the method according to claim 15.

22. A computer program comprising program instructions that cause a processor to execute and/or control the method according to claim 15 when the computer program is running on the processor.

Description

BRIEF DESCRIPTION OF THE INVENTION

[0052] In the following, the invention is explained with reference to the drawing by means of examples of embodiments. The drawing shows

[0053] FIG. 1 an exemplary comparison of measured temperature data and temperature data calculated by means of a model;

[0054] FIG. 2 an exemplary representation of different temperature curves based on different controls for temperature control of a casting process; and

[0055] FIG. 3 a further exemplary representation of different temperature curves based on different controls for controlling the temperature of a casting process.

DESCRIPTION OF THE INVENTION

[0056] FIG. 1 shows an exemplary comparison of a temperature curve 2 of a realistic simulation and a temperature curve 4 calculated using a model. The temperature curve 4 calculated using the model, in particular using the dynamic model, deviates only slightly from the temperature curve 2 of the realistic simulation, so that the basic system dynamics of the casting process can be reliably reproduced by the dynamic model.

[0057] To create the dynamic model, data from a vehicle subframe component made of an aluminum alloy produced using the casting process was used.

[0058] A realistic simulation was first used to create a data set by means of which the system dynamics of the available data were identified. Such a realistic simulation is preferably a simulation for casting processes. In this case, a simulation from Magmasoft was used.

[0059] The realistic simulation was used to change various input variables indicative for different input values so that a comprehensive data set is available. To determine an output variable indicative of a temperature in the mold, a fixed position of a thermocouple in the mold was selected. In this case, the following different input values and the input variables indicative of these input values were taken into account in the simulation: [0060] the flow rate of the coolant in two cooling circuits close to the specific position of the thermocouple; and [0061] the heating rate of a heating source or heating element close to the specific position of the thermocouple.

[0062] The filling of the mold with a melt or the mold filling was also taken into account as a measured disturbance.

[0063] The mold filling was modeled as a Dirac pulse, whereby the respective Dirac pulse is triggered as soon as the mold filling flows into the mold in the simulation. In the context of model predictive control, the mold filling can also be referred to as a measured disturbance.

[0064] The following process model was adapted to the data determined in the simulation:

[00007]$Y_{\mathrm{out}}\left(s\right)={.Math.}_{k=1}^n{G}_i\left(s\right)U_{\mathrm{in},i}\left(s\right);$

[0065] Y.sub.out is the output variable that is indicative of at least one temperature of the casting process. The input variables indicative of the aforementioned input variables are referred to as U.sub.in, i. The function G.sub.i(s) is a transfer function which can be represented by the following formula for the individual input variables:

[00008]$G_i\left(s\right)=\frac{K_i}{{\left(1+T_i\right)}^2}.$

[0066] K.sub.i is a gain factor of the respective input variable, where T.sub.i is a time constant.

[0067] As shown in FIG. 1, the predicted temperature curve of the identified dynamic model deviates only slightly from the temperature curve of the realistic simulation, so that the dynamic model reliably predicts the temperature curves that occur during the casting process.

[0068] FIG. 2 shows an example of various temperature curves based on different temperature control systems for a casting process. The temperature profile of a realistic simulation 2, the temperature profile of the model predictive control 6, the temperature profile of a PID control 8 and the temperature profile of a bang-bang control 10 were compared with each other. A constant temperature trajectory of 320 C. was selected as the preset temperature profile 12.

[0069] The model predictive control 6 was based on a prediction horizon of n.sub.PH=1000 for a time interval of T=1 s. Accordingly, 1000 time intervals of 1 s each are included in the calculation. The control horizon n.sub.CH was also set at 100 for a time interval of T=1 s, so that the input variables can be changed for 100 time intervals.

[0070] The weighting matrices Q, R and S were selected as unit matrices with the constants q, r and s on the diagonal, where q=1,000,000; r=1; and s=0.

[0071] As an input variable indicative of an input variable, an input variable indicative of a flow rate of a coolant was controlled in the controls shown in FIG. 2. It can be seen that the model-predictive control 6 enables a temperature profile that is on average closer to the preset temperature profile 12 than the other control types 8 and 10. However, since the temperature can essentially only be moved in one direction by the flow rate of the coolant, namely a temperature reduction can be caused, the model shown in FIG. 2 has technical limitations that stand in the way of further improved control.

[0072] FIG. 3 shows another example of different temperature curves based on different controls for controlling the temperature of a casting process. In contrast to the controls shown in FIG. 2, the controls shown in FIG. 3 are based on two input variables, namely an input variable indicative of the flow rate of a coolant and a further input variable indicative of the heating rate of a heating source. In this respect, the two aforementioned input variables can be controlled by the respective controllers in such a way that the respective temperature curves have the smallest possible difference to the preset temperature profile 12. As can be seen from FIG. 3 and also from a comparison of FIGS. 2 and 3, a temperature profile that is very close to the preset temperature profile can be achieved, particularly with model-predictive control 6. With the other control types 8 and 10, only a slight improvement could be achieved by controlling an additional input variable.

[0073] The exemplary embodiments of the present invention described in this specification are also to be understood as disclosed in all combinations with each other. In particular, the description of a feature encompassed by an embodiment-unless explicitly stated to the contrary-should not be understood herein to mean that the feature is indispensable or essential for the function of the exemplary embodiment.

[0074] Terms used in the claims such as comprising, comprising, comprising, containing and the like do not exclude further elements or steps. The phrase at least partially includes both the case of partially and the case of completely. The wording and/or is to be understood as meaning that both the alternative and the combination are to be disclosed, i.e. A and/or B means (A) or (B) or (A and B). A plurality of entities, persons or the like in the context of this specification means a plurality of entities, persons or the like. The use of the indefinite article does not exclude a plurality. A single device or means may perform the functions of a plurality of units or devices specified in the claims. Reference signs given in the claims are not to be regarded as limitations of the means and steps employed.