DE10123274B4 - Method for controlling the temperature of an extruder for metals - Google Patents

Abstract

Method for controlling the temperature of an extruder for metals, by evaluating a just past pressing cycle k a curve for an input function u _{k + 1} (l) for manual control of the pressing speed and an axial bar temperature curve θ _{Bk + 1} (l) of the material to be pressed one following cycle (k + 1) are generated and specified such that the temperature θ _{ak + 1} (l) of the profiles as exiting the die as constant as possible and equal to a predetermined setpoint θ _aw , and at the same time the pressing speed as constant as possible and equal given value v _{k + 1} remains, and the feed of the calculated input function u _{k + 1} (l) by descending a superimposed on a monitor history of the calculated input function takes place, wherein an actual bar temperature curve θ _{Bk + 1} (l) is measured, and from this calculates an optimal input function history and from the beginning to the end of (k + 1). Pressing cycle is superimposed on a monitor on which at the same time an input manually entered by the operator input function is also displayed in such a way that the surgeon by descending the optimal course ...

Description

This The invention relates to a method for controlling the temperature of an extruder for metals.

extrude are commonly used for making stranded products made of metal, glass or plastic. In this process, assigned to hot forming processes in process engineering is to control productivity in order to maximize productivity and homogenize product quality of the thermal household desired.

At the Extrusion of metals, such. B. of aluminum, on which As will be referred to below, aluminum ingots are in one Oven at 400 to 500 ° C heated and then loaded into a receptacle (recipient). This one-sided by a die closed, the breakthrough of the cross section of the resulting profile strand corresponds. From the other side is with a stamp under the influence of a very large force (> 10 MN) the block except for a small one Rest pushed through the die. After completion of a cycle, a new block is loaded and the Pressing process can be repeated.

The Balance of the thermal budget results from the difference of the supplied thermal energy and mechanical work and by heat conduction dissipated Energy. The resulting temperature of the protruding profiles at the exit from the die can by the preheat of the Ingot and the pressing speed are specifically influenced. The pressing speed in turn is in older systems by the operator input for the Adjustment of the oil flow rate of the hydraulic system. Here is the surgeon input the setpoint for the swivel angle of a swivel angle pump or for the valve position. In modern plants, the press guide gives what they want Target course for the speed ahead. A speed control ensures that the actual Press speed equal to the specified press speed by the press driver is, provided that the pressing pressure remains within its limits. In general is the speed control with a memory programmable control system (PLC) implemented.

In the process engineering is known that the productivity maximum then achieved if possible while of the entire pressing cycle with the maximum permissible strand outlet temperature is pressed. Furthermore, this temperature has a considerable Influence on the metallurgical properties of the products, therefore also for reasons quality assurance There is considerable interest in defining and defining them while to keep the process constant. Upon fulfillment of this condition speaks one of an isothermal extrusion process [1, 2, 3].

The However, realization of the isothermal extrusion of aluminum is associated with significant, technologically inadequately solved problems, therefore so far mainly a theoretical review of the topic in the technical literature is done, the use at a broad level but has failed in the industry.

• a) Beim simulierten Strangpressen [5] wird die Strangaustrittstemperatur aufgrund eines thermischen Simulationsmodells vorausberechnet und durch Umkehrung kann ein bezüglich dieses Modells optimaler Pressgeschwindigkeitsverlauf berechnet werden. Der Strangpressprozess, der ein thermisches System mit verteilten Parametern darstellt, ist mit analytischen Methoden jedoch kaum und mit numerischen Methoden nur ungenau beschreibbar, weswegen dieses Verfahren keine be friedigende Ergebnisse liefert.
• b) Beim geregelten Strangpressen [4] wird die Strangaustrittstemperatur gemessen, wobei vorwiegend Strahlungspyrometer eingesetzt werden. Die Grundstruktur entspricht einem geschlossenen Regelkreis, der durch permanenten Vergleich von Soll- und Istwert während des Prozesses eine Stellgröße für die Pressgeschwindigkeit berechnet. Da bei der kontaktlosen Messung der Strangaustrittstemperatur, insbesondere an Aluminium, mit regelmäßigen Störungen zu rechnen ist, kann ein unkontrolliertes Systemverhalten nicht ausgeschlossen werden. Folglich hat sich diese Strategie in der Praxis als nicht leicht anwendbar erwiesen.
• c) Im Europäischen Patent EP 0615 795 B1 [6] ist die zyklische Regelung von Strangpressen angegeben [7,8].
• 1. Das Verfahren beginnt mit der Messung des axialen Barrentemperaturprofils, bevor er im Rezipienten eingeladen wird.
• 2. Der Verlauf der Pressgeschwindigkeit als Funktion der Stempelposition l wird vor Beginn eines jeden Presszyklus von einem Digitalrechner berechnet und vorgegeben. Der Geschwindigkeitsregelkreis sorgt dafür, dass der tatsächliche Geschwindigkeitsverlauf mit dem vorgegebenen Sollverlauf übereinstimmt.
• 3. Die Pressung erfolgt. Die tatsächliche Pressgeschwindigkeit und die Strangaustrittstemperatur werden über den gesamten Presszyklus gemessen.
• 4. Nach Beendigung des Presszyklus wird der optimale Sollgeschwindigkeitsverlauf für den nachfolgenden Zyklus mit Hilfe von Optimierungsalgorithmen unter Berücksichtigung der Grenzwerte derart berechnet und vorgegeben, dass die Temperaturfehler, d.h. die Differenz zwischen den gewünschten und der tatsächlichen Strangaustrittstemperatur, minimiert wird.

In the literature [4, 5, 6, 7] are so far known a) the simulated isothermal extrusion, b) controlled isothermal extrusion and c) the cyclic control of extruders.

• a) In simulated extrusion [5], the strand outlet temperature is calculated in advance on the basis of a thermal simulation model, and by reversing it is possible to calculate an optimum compression velocity profile with respect to this model. However, the extrusion process, which is a thermal system with distributed parameters, is poorly described by analytical methods and numerical methods only inaccurately, which is why this method does not provide satisfactory results.
• b) In controlled extrusion [4], the strand outlet temperature is measured, with predominantly radiation pyrometers being used. The basic structure corresponds to a closed control loop, which calculates a manipulated variable for the pressing speed by permanently comparing the setpoint and actual value during the process. Since in the contactless measurement of the strand outlet temperature, in particular of aluminum, is to be expected with regular disturbances, an uncontrolled system behavior can not be excluded. Consequently, this strategy has proven to be not easily applicable in practice.
• c) In the European patent EP 0615 795 B1 [6] the cyclic control of extrusion presses is given [7,8].
• 1. The procedure begins with the measurement of the axial bar temperature profile before being loaded into the recipient.
• 2. The course of the press speed as a function of the punch position l is calculated and specified by a digital computer before the start of each press cycle. The speed control loop ensures that the actual speed curve matches the specified setpoint course.
• 3. The pressing takes place. The actual press speed and the strand exit temperature are measured over the entire press cycle.
• 4. At the end of the pressing cycle, the optimum target velocity profile for the subsequent cycle is calculated and specified by means of optimization algorithms taking into account the limit values in such a way that the temperature errors, ie the difference between the desired and the actual strand outlet temperature, are minimized.

The above-mentioned method c) is successfully used and tested in modern extrusion presses with memory programmable control systems (SPS) and speed control [8, 9]. In older systems, a cruise control is not available. The input is made via a rotary knob, with which the press driver sets the desired angular position for the swivel angle or valve of the hydraulic system. The use of a regulation after EP 0615 795 B1 turns out to be costly. Furthermore, the installation of the system requires the interruption of the pressing operation.

A prerequisite in EP 0615 795 B1 which is not always present is that the bar temperature is not subject to fluctuations.

task the present invention is to develop a method implemented with isothermal extrusion in older extrusion presses can be made without costly investments such as for a cruise control or interruptions, with further changes in the Bar temperature is taken into account. The task is solved by a Method according to the features of claim 1.

Of the Inventor proposes a method for generating and feeding an optimal trajectory for the surgeon input or press speed for a given bar temperature profile. The feeding of the optimal trajectory takes place in older extrusion presses (without speed control or memory programmable controllers) by descending the predetermined optimal course of the input on a monitor on the part of the surgeon.

Furthermore beats he for Plants with barren stoves, in which the axial temperature profile (Taper) specifically adjustable is a method by which isothermal extrusion at preferably constant pressing speed can be achieved. In this case will that, for achieving the desired constant exit temperature at the desired constant press speed, required bar temperature profile calculated and the Barrenofentemperaturregelung specified. Before loading the bar into the recipient, the indeed reached Barentemperaturprofil recorded and the associated surgeon input history calculated and fed.

• – Die Sollwertkurve der Strangaustrittstemperatur θ_aw(t) (0 < t < T_Zyk) ist vor Beginn eines Zyklus bekannt.
• – Die Zykluszeit T_Zyk hat stets die gleiche Größenordnung.
• – Das Systemverhalten ist nur langsam zeitveränderlich (>> T_Zyk).
• – Der Prozess ist nichtlinear und mit analytischen Methoden kaum beschreibbar.
• – Das Prozessverhalten ist determiniert, unterliegt keinen stochastischen Parameterschwankungen und ist stets reproduzierbar.
• – Jeder Zyklus hat den gleichen Anfangszustand.
• – Die Stellgrößen des Prozesses sind begrenzt und nicht beliebig schnell veränderbar.
• – Die Erfassung der Regelgröße (Strangaustrittstemperatur θ_a) ist mit Fehlern, Messstörungen und mit einer Totzeit behaftet, weswegen eine offline-Verarbeitung der Messsignale vorteilhaft ist.

From a control engineering point of view, the extrusion press, with a radiation pyrometer as a measuring sensor for the controlled variable, is characterized as follows:

• - The setpoint curve of the strand outlet temperature θ _aw (t) (0 <t <T _Zyk ) is known before the beginning of a cycle.
• - The cycle time T _Zyk always has the same order of magnitude.
• - The system behavior is only slowly time- _changeable (>> T _Zyk ).
• - The process is non-linear and hardly describable by analytical methods.
• - The process behavior is determined, is not subject to stochastic parameter fluctuations and is always reproducible.
• - Each cycle has the same initial state.
• - The manipulated variables of the process are limited and can not be changed arbitrarily fast.
• - The detection of the controlled variable (strand outlet temperature θ _a ) is fraught with errors, measurement errors and a dead time, which is why an offline processing of the measurement signals is advantageous.

Due to these process properties, the European patent EP 0615 795 B1 proposed a method that deviates from conventional fixed-value controls. It is not, as in a closed loop, only the local operating point, but always optimized the entire cycle. Because of the repetitive nature of the process, the experience of one cycle k is used to generate the press speed curve k + 1, thus providing feedback from one cycle to the other is.

In previous literature, such as [5] and im EP 0615 795 B1 [6], it is assumed that for a given bar temperature, the pressing speed is the immediate variable variable by the surgeon. Consequently, the methods proposed there calculate and specify the desired pressing speed profile. A speed control loop, if one exists, ensures that this speed profile is also achieved. The procedures are not applicable if there is no cruise control. This situation exists in older systems. In older systems, it is not the pressing speed but the pivot angle of a swivel angle pump or the valve position and thus the oil flow rate that is the primary operator input parameter.

in the Contrary to [5, 6] in the present invention, both the oil flow rate as well as the press speed as surgeon input u allowed. In order to deleted the requirement of the presence of a cruise control.

• i) Nach einem jeden Matrizenwechsel wird der erste Zyklus mit den Erfahrungswerten des Operateurs gefahren. Nach Ablauf des ersten Zyklus wird zunächst durch Auswertung der Verläufe der Eingabegrösse u₀(t) und Ausgangsgröße θ_a0(t) ein mathematisches Abbild für das Übertragungsverhalten der Strangpresse erstellt.
• ii) Die Regelung setzt ab den 2. Zyklus ein. Mit Hilfe des Abbilds wird anhand der gemessenen Verlaufs von der Austrittstemperatur θ_ak(t) und der Operateureingabe u_k(t) im k-ten Zyklus der Verlauf der Eingabegrösse u_k+1(t) nach den Verfahren der iterativ lernender Regelungen [10, 11] derart bestimmt, dass der Regelfehler ek+1(t) = θaw(t) – θak+1(t) (1)und der Stellaufwand u_k+1(t) möglichst gering werden. Insbesondere können auch Stellgrößenbeschränkungen berücksichtigt werden. Die Operateureingabekurve u_k+1(t) wird vor Beginn des Zyklus k + 1 berechnet und während des Pressvorgangs nicht mehr verändert.

The proposed method works in 2 phases.

• i) After each die change, the first cycle is run with the experience of the surgeon. After the first cycle has ended, a mathematical image for the transfer behavior of the extruder is first created by evaluating the curves of the input variable u ₀ (t) and output variable θ _a0 (t).
• ii) The scheme starts from the 2nd cycle. With the aid of the image, the course of the input quantity u _{k + 1} (t) is calculated according to the methods of the iteratively learning rules [10... _K ) in the k th cycle on the basis of the measured profile of the exit temperature θ _ak (t) and the operator input u _k (t) , 11] determined such that the control error e k + 1 (t) = θ aw (t) - θ k + 1 (t) (1) and the control effort u _{k + 1} (t) as low as possible. In particular, manipulated variable restrictions can also be taken into account. The operator input curve u _{k + 1} (t) is calculated before the beginning of the cycle k + 1 and is not changed during the pressing process.

To Termination of the pressing process k + 1 is checked by considering the control quality, whether the mathematical Image has to be readjusted. If this is the case, it will go through Evaluation of the input and output curves as determined under i). Otherwise, proceed according to ii).

This approach facilitates the suppression of measurement disturbances because, in contrast to conventional controls, more powerful, non-causal filters can be used and, despite difficult boundary conditions, leads to a safe and robust control system. Due to the thermal inertia of the extruder, the changes in the boundary conditions (tool or recipient temperature) of successive cycles are negligibly small, ensuring an optimal process flow. Since the realization is possible only with a microcomputer, the time functions are scanned discretely. The continuous time t is followed by the discrete time i t = i · T A , i = 0, 1, 2, ... (2) replaced. An alternative is to sample the signals at those times when the stamp clears the way l = i · ΔL, where ΔL = elementary length and i = 0, 1, 2, ... (3) has put back.

functionality of the new procedure

It is taken into account, that in some extrusion presses a controllable ingot furnace for disposal with which the ingot a predetermined axial temperature profile, called Taper, to be imprinted can. In such systems, by applying the optimal tapers isothermal pressing achieved at a constant speed.

The exit temperature of the profile, when the plunger has traveled the distance l in mm since the beginning of pressing, is denoted by θ _a (l). The length l is at the same time the length of the pressed bar: The outlet temperature under otherwise identical conditions depends on the bar temperature at the point l, as well as from the course of the operator input u in the interval (0, l).

method for plants without possibility to the imprint an axial temperature profile

In In this case, the bar temperature can be adjusted only gradually. The Exit temperature control is then changed by changing the operator input function (Setpoint for the oil flow rate or for the Press speed) accomplished. As the temperature of the Bars, as they come out of the oven, only gradually changes, lies a quasi-stationary one Condition before. The temperature of the ingot in the (k + 1) -th cycle is approximately the same with the cycle k.

Figure 1 shows the arrangement of a direct extrusion press with the proposed mobile measuring and automation system for extrusion molding (MoMAS). The outlet temperature θ _ak (l) is detected with pyrometer 1 and passed to the industrial PC via an interface unit, which is used for galvanic isolation and signal conditioning. Pyrometer 2 (which could also be replaced by a contact thermometer) detects the temperature profile θ _Bk (l) of the billet.

The Bars are heated in a block oven and fed to the extruder. The Pressing is done by building up the pressing pressure by adjusting the oil flow rate changed becomes. In systems without speed control, the input is u, which dictates the surgeon, the target value of the pivot angle of a Swivel angle pump and thus the setpoint for the oil flow. In plants with a Speed control is the input u is the setpoint for the press speed. In both cases the entry is made by the position of the potentiometer in the picture 1. The potentiometer position is also called an analog or digital Signal over the Interface unit led to the computer. It represents the input function u (l) as a function of the platen position l. The position sensor detects the current position l of the stamp. In systems with a cruise control becomes the actual press speed from the detected position signal determined. The speed control is by the automatic change the oil flow rate dependent on realized by the difference between the target and actual speeds of the punch. In MoMAS the current position l also becomes the interface unit Computer led

wobei α, β und g_k(l) unter Verwendung von Daten aus vorausgegangenen Pressläufen gewählt werden. Durch Diskretisierung mit l = i·Δ, i = 0, 1, 2, ..., N – 1, N·Δ = L = Länge des zu pressenden Barrens werden die Gleichungen (4) (5) zu

bzw. in Matrizendarstellung

For the calculation of the optimal input profile, the following approach is chosen for the relationship between the process variables:

where α, β and g _k (l) are selected using data from previous press runs. By discretization with l = i · Δ, i = 0, 1, 2, ..., N - 1, N · Δ = L = length of the billet to be pressed, equations (4) (5) are added

or in matrix representation

wobei R die Reglermatrix und

darstellen.The elements of the impulse response matrix G _k are also determined from previous experiments [10, 11]. The calculation of the optimal course of u _{k + 1} (l) at the beginning of the (k + 1) cycle is carried out as described in [1] with optimizing iteratively learning rules. A second possibility for the determination of u _{k + 1} (l) exists with the help of linear iterative learning control. This is

where R is the regulator matrix and

represent.

The isothermal pressing is achieved with the abovementioned automation system with the involvement of the operator in the control loop as follows: The optimum course of the input function u _{k + 1} (l) for the cycle k + 1 becomes in the interval between the cycles k and k + 1 out of the Run the input function u _k (l) and the error function e _k (l) calculated in the cycle k. The total calculated course is a function of the punch position at the beginning of the (k + 1). Cycle displayed on a monitor. At the same time, the actual operator input is displayed on the same monitor. The surgeon retraces the optimal curve by properly manipulating the operator input knob, and then applies the calculated optimum input function curve u _{k + 1} (l) to the extruder. In case the oven temperature control does not ensure a constant bar temperature, the bar temperature is measured before the bar is loaded into the receiver and the measured value is included in the calculation.

• a) MoMAS wird während eines vom Operator bestimmten Zyklus – z.B. des zweiten Zyklus nach einem Matrizenwechsel – aktiviert.
• b) Die Barrentemperatur wird gemessen.
• c) Die Operateureingabe u(l), mit l = der Stempelweg, für diesen Zyklus ist eine konstante Grösse u₀, die der Operator aufgrund seiner Erfahrung und Expertise wählt und vorgibt.
• d) Nach Ablauf des Zyklus wird das Maximum der Profilaustrittstemperatur θ_max in diesem Zyklus von MoMAS automatisch ermittelt. Üblicherweise tritt θ_max gegen Ende des Zyklus auf. Gleichzeitig kontrolliert der Operateur die Qualität des Profils. Ist die Profilqualität zufriedenstellend, so stellt θ_max die Profilaustrittstemperatur dar, die man idealerweise durch Vorgabe einer geeigneten Operateureingabe u_soll(l) über den ganzen Zyklus erzielen müsste. Wahlweise kann der Operator θ_max oder einen anderen Wert für den Sollwert der Profilaustrittstemperatur θ_aW wählen.
• e) MoMAS ermittelt den Zusammenhang zwischen der Operatoreingabe, Barrentemperatur, Pressgeschwindigkeit und der Profilaustrittstemperatur aus den Verläufen der Prozessgrößen im abgelaufenem (k-ten) Zyklus.
• f) Die Barrentemperatur der nächsten im Zyklus k + 1 zu pressenden Barren wird gemessen.
• g) Den optimalen Verlauf der Operateureingabe u_k+1(l) in Abhängigkeit vom Stempelweg l wird unter Benutzung der Kenntnissen der Verläufe der Prozessgrößen im vorangegangenen Zyklus k, sowie der gemessenen Barrentemperatur und der gewünschten Austrittstemperatur, unter Berücksichtigung der erlaubten Grenzen der Stellgrößen, nämlich Presskraft und Stempelgeschwindigkeit von MoMAS berechnet.
• h) Der von MoMAS berechnete Verlauf der Operateureingabe u_k+1(l) wird für den gesamten Zyklus zu Beginn des nachfolgenden Zyklus auf den Monitor eingeblendet.
• i) Die Pressung des k + 1-ten Zyklus wird gestartet. Auf dem Monitor wird zusätzlich zu dem von MoMAS vorgeschlagenen Verlauf u_k+1(l) für die Operateureingabe auch die tatsächlich vom Operateur vorgegebene Eingabe in einer anderen Farbe dargestellt. Der Operator justiert nun seine Eingabe laufend während des Zyklus derart, dass in der Anzeige seine Eingabe mit dem vorgeschlagenen Verlauf möglichst gut übereinstimmt.
• j) Die Schritte e) bis i) werden wiederholt. Eventuell kann man auf Schritt e) verzichten und nur die Schritte f) bis i) wiederholen.

More specifically, the method consists of the following steps:

• a) MoMAS is activated during a cycle determined by the operator - eg the second cycle after a die change.
• b) The bar temperature is measured.
• c) The operator input u (l), where l = the stamp path, for this cycle is a constant quantity u ₀ , which the operator chooses and specifies based on his experience and expertise.
• d) At the end of the cycle, the maximum of the profile exit temperature θ _max in this cycle is automatically determined by MoMAS. Usually, θ _max occurs near the end of the cycle. At the same time, the surgeon checks the quality of the profile. If the profile quality is satisfactory, θ _{max represents} the profile exit temperature, which ideally should be achieved by specifying a suitable operator input u _soll (l) over the entire cycle. Optionally, the operator may choose θ _max or some other value for the setpoint value of the profile exit _temperature θ _aW .
• e) MoMAS determines the relationship between the operator input, bar temperature, press speed and profile exit temperature from the process variables in the expired (k th) cycle.
• f) The bar temperature of the next bar to be pressed in cycle k + 1 is measured.
• g) The optimal course of the operator input u _{k + 1} (l) as a function of the punch path l, using the knowledge of the processes of the process variables in the previous cycle k, and the measured bar temperature and the desired outlet temperature, taking into account the allowed limits of the control variables, namely press force and punch speed calculated by MoMAS.
• h) The progression of the operator input u _{k + 1} (l) calculated by MoMAS is superimposed on the monitor for the entire cycle at the beginning of the following cycle.
• i) The pressing of the k + 1-th cycle is started. In addition to the progression u _{k + 1} (l) suggested by MoMAS, the monitor also displays the input actually given by the surgeon in a different color for the surgeon input. The operator now adjusts his input continuously during the cycle in such a way that in the display his input matches the suggested course as well as possible.
• j) Steps e) to i) are repeated. You may be able to do without step e) and only repeat steps f) to i).

It can for the surgeon input, for example, a three-step history selected and with the first step extending over the first 30% of the block length, the second over 40 and the third level over the remaining 30% of the block length.

In make of new alloys, profile geometries or positioning limits, in which The surgeon can not rely on his experience, the optimal outlet temperatures using the control limits with MoMAS by gradually increasing the limits until the optimum has been reached.

method for plants with possibility to the imprint an axial temperature profile

In this case, the bar a temperature profile can be impressed, also the temperature adjustment in the oven can be done quickly. It is thus possible to specify a constant pressing speed and a constant outlet temperature, and to achieve this by suitable control of the bar temperature profile. The setpoint curve of the bar temperature profile is calculated by the method of optimizing iterative learning control or the linear iterative learning control using equation (9), where u is the input replaced by v the press speed and G by G *. G * represents the impulse response matrix in the event that the press speed as input and exit temperature are considered as output. Since i. Gen. however, if the resulting barrel temperature profile deviates from the target, the actual ingot temperature profile is measured before the ingot is loaded into the recipient. Using this data, the desired course for the operator input is calculated and specified. Thus, the constant maintenance of the outlet temperature over the constant maintenance of the pressing speed is prioritized higher.

• a) MoMAS wird während eines vom Operator bestimmten Zyklus – z.B. des zweiten Zyklus nach einem Matrizenwechsel – aktiviert.
• b) Die Barrentemperatur wird gemessen.
• c) Die Operateureingabe u(l), mit l = der Stempelweg, für diesen Zyklus ist eine konstante Grösse u₀, die der Operator aufgrund seiner Erfahrung und Expertise wählt und vorgibt.
• d) Nach Ablauf des Zyklus wird das Maximum der Profilaustrittstemperatur θ_max in diesem Zyklus von MoMAS automatisch ermittelt. Üblicherweise tritt θ_max gegen Ende des Zyklus auf. Gleichzeitig kontrolliert der Operateur die Qualität des Profils. Ist die Profilqualität zufriedenstellend, so stellt θ_max die Profilaustrittstemperatur dar, die man idealerweise durch Vorgabe des Barrentemperaturprofils und einer geeigneten Operateureingabe u_soll(l) über den ganzen Zyklus erzielen müsste. Wahlweise kann der Operator θ_max oder einen anderen Wert für den Sollwert der Profilaustrittstemperatur θ_aW wählen.
• e) Der Operateur gibt die gewünschten Werte v_soll bzw. θ_aW für die Pressgeschwindigkeit bzw. für die Austrittstemperatur vor.
• f) MoMAS ermittelt den Zusammenhang zwischen der Operatoreingabe, Barrentemperatur, Pressgeschwindigkeit und der Profilaustrittstemperatur aus den Verläufen der Prozessgrößen im abgelaufenem (k-ten) Zyklus.
• g) Das Solltemperaturprofil für das Barrenofen für den Zyklus k + 2 wird errechnet und vorgegeben.
• h) Das Barrentemperaturprofil des im nächsten (k + 1)-ten Zyklus zu pressenden Barrens wird gemessen.
• i) Den optimalen Verlauf der Operateureingabe u_k+1(l) in Abhängigkeit vom Stempelweg l wird unter Benutzung der Kenntnissen der Verläufe der Prozessgrößen im vorangegangenen Zyklus k, sowie der gemessenen Barrentemperatur θ_Bk+1 und der gewünschten Austrittstemperatur θ_aek+1 im Zyklus k + 1 unter Berücksichtigung der erlaubten Grenzen der Stellgrössen, nämlich Presskraft und Stempelgeschwindigkeit, von MoMAS berechnet.
• j) Der von MoMAS berechnete Verlauf der Operateureingabe u_k+1(l) wird für den gesamten Zyklus zu Beginn des nachfolgenden Zyklus auf den Monitor eingeblendet.
• k) Die Pressung des k + 1-ten Zyklus wird gestartet. Auf dem Monitor wird zusätzlich zu dem von MoMAS vorgeschlagenen Verlauf u_k+1(l) für die Operateureingabe auch die tatsächlich vom Operateur vorgegebene Eingabe in einer anderen Farbe dargestellt. Der Operator justiert nun seine Eingabe laufend während des Zyklus derart, dass in der Anzeige seine Eingabe mit dem vorgeschlagenen Verlauf möglichst gut übereinstimmt.
• l) Die Schritte e) bis k) werden wiederholt. Eventuell kann man sich auf Schritt e) und/oder auf f) verzichten.

More specifically, the method consists of the following steps:

• a) MoMAS is activated during a cycle determined by the operator - eg the second cycle after a die change.
• b) The bar temperature is measured.
• c) The operator input u (l), where l = the stamp path, for this cycle is a constant quantity u ₀ , which the operator chooses and specifies based on his experience and expertise.
• d) At the end of the cycle, the maximum of the profile exit temperature θ _max in this cycle is automatically determined by MoMAS. Usually, θ _max occurs near the end of the cycle. At the same time, the surgeon checks the quality of the profile. If the profile quality is satisfactory, θ _{max represents} the profile exit temperature, which would ideally have to be achieved by specifying the bar temperature profile and a suitable operator input u _soll (l) over the entire cycle. Optionally, the operator may choose θ _max or some other value for the setpoint value of the profile exit _temperature θ _aW .
• e) The operator inputs the desired values v _soll or θ _aW before the pressing speed or for the outlet temperature.
• f) MoMAS determines the relationship between the operator input, bar temperature, press speed and the profile exit temperature from the process variables in the expired (k th) cycle.
• g) The setpoint temperature profile for the ingot furnace for cycle k + 2 is calculated and specified.
• h) The ingot temperature profile of the bar to be pressed in the next (k + 1) -th cycle is measured.
• i) The optimal course of the operator input u _{k + 1} (l) as a function of the punch path l is using the knowledge of the courses of the process variables in the previous cycle k, and the measured bar temperature θ _{Bk + 1} and the desired outlet temperature θ _{aek + 1} im Cycle k + 1 taking into account the permitted limits of the manipulated variables, namely pressing force and punch speed, calculated by MoMAS.
• j) The course of the operator input u _{k + 1} (l) calculated by MoMAS is superimposed on the monitor for the entire cycle at the beginning of the following cycle.
• k) The pressing of the k + 1-th cycle is started. In addition to the course suggested by MoMAS, u _{k + 1} (l) for the surgeon input is actually displayed on the monitor by the surgeon Input displayed in a different color. The operator now adjusts his input continuously during the cycle in such a way that in the display his input matches the suggested course as well as possible.
• l) Steps e) to k) are repeated. You may be able to do without step e) and / or f).

designations

• e _k (l) control error depending on the punch position
• e control error
• g (t) impulse response of the linearized model of the path with the surgeon input as input and outlet temperature as output
• G impulse response matrix
• l Stamp position = pressed bar length
• t time (continuous)
• T _A sampling time
• T _cycle time of a press cycle
• u Operator entry: Setpoint for swivel angle or press speed
• u _should (l) course of the desired course of the surgeon input as a function of the punch position
• u _k (l) The at the beginning of the k. Cycle proposed and visualized progression of surgeon input as a function of stamp position l
• v Press speed
• v _k (l) Pressing speed in k Cycle at punch position = pressed bar length l
• ΔL elementary length at the discretization of the stamp position
• θ _a strand outlet temperature
• 
  Strand outlet temperature (setpoint curve)
• θ _max Maximum outlet temperature
• 
  Strand outlet temperature (actual value curve in cycle k) as a function of punch position l
• θ _Bk (l) Course of the bar temperature in k. Cycle as a function of punch position

indices:

• i time index (discrete), place index
• k cycle

literature

• [1] Ruppin, D. and Strehmel, W. direct Extrusion with constant outlet temperature - use variable pressing speed magazine Aluminum, 1977, pp. 543-548
• [2] Ruppin, D. and Strehmel, W. Automation of the pressing process in the direct extrusion of aluminum materials (I) magazine Aluminum, 1983, pp. 674-678
• [3] Ruppin, D. and Strehmel, W. Automation of the pressing process in the direct extrusion of aluminum materials (II) magazine Aluminum, 1983, p. 773-776
• [4] Ingvorsen, J. Closed loop isothermal extrusion Proc. Intnl. Extrusion Technology Symposium, pp. 549-558, Chicago (2000)
• [5] Biswas, K .; Repgen, K. and Steinmetz, A. Computer simulation of Extrusion Press Operation - Experience with CADEX A New Computer Aided Process Optimizing System 5th International Extrusion Seminar, Chicago 1992, p. 149-155
• [6] EP 0615795 B1 Temperature control of an extruder
• [7] Pandit, M. Baqué, S. Deis, W., Müller, K .: Implementation of Temperature Measurement and Control in Aluminum Extruders Extrusion Technology 2000, Chicago, 15-19. 5th 2000
• [8] Pandit, M., Buchheit, K., Isothermal extrusion of aluminum ", Part I, Aluminum, Issue 4 (1995), pp. 483-487, Part II, Aluminum, Issue 5 (1995), p. 614-619
• [9] Pandit, M. Trends and Perspectives concerning temperature Measurement and Control in Aluminum Extruders Aluminum, 76, H. 7-8, July August 2000, pages 564-573
• [10] Hillenbrand, p Iterative learning regulations with reduced sampling rate Dissertation, Department of Electrical Engineering, University of Kaiserslautern, 2000
• [11] Isermann, R .: Identification of dynamic systems, Bd. 1 + 2 Springer Verlag Berlin 1988

Claims (6)

Method for controlling the temperature of an extruder for metals, by evaluating a just past pressing cycle k a curve for an input function u _{k + 1} (l) for manual control of the pressing speed and an axial bar temperature curve θ _{Bk + 1} (l) of the material to be pressed one following cycle (k + 1) are generated and specified such that the temperature θ _{ak + 1} (l) of the profiles as exiting the die as constant as possible and equal to a predetermined setpoint θ _aw , and at the same time the pressing speed as constant as possible and equal given value v _{k + 1} remains, and the feed of the calculated input function u _{k + 1} (l) by descending a superimposed on a monitor history of the calculated input function takes place, wherein an actual bar temperature curve θ _{Bk + 1} (l) is measured, and from this calculates an optimal input function history and from the beginning to the end of (k + 1). Press cycle is superimposed on a monitor, on which at the same time an input manually by the operator input function is also displayed such that the surgeon imprints the optimal input function course by descending the optimal course of the press control. A method according to claim 1, characterized in that the set by the surgeon target value θ _{aw is} automatically selected as the maximum of the outlet temperature of a previous cycle, the quality of the profile is ensured by the surgeon. A method according to claim 1, characterized in that the determined axial bar temperature profile θ _{Bk + 1} (l) is transmitted to a furnace temperature control and adjusted there. Method according to one of claims 1 to 3, characterized in that the optimal characteristics of the input function u _{k + 1} (l) and the axial bar temperature curve θ _{Bk + 1} (l) are determined by means of a simulation model and algorithms of the iterative learning control. Method according to one of claims 1 to 4, characterized in that for determining the input function u _{k + 1} (l) required impulse responses g (t) and / or g (l) of a linearized model of the extruder by evaluating the input function uk (l) and the exit temperature θ _ak (l) of the past cycles are used. Method according to one of claims 1 to 5, characterized in that the bar temperature θ _Bk (l) is automatically lowered successively, so that the control of the outlet temperature via the input function u _k (l) engages, and thereby automatically increases the predetermined pressing speed and thus the predetermined Pressing time is shortened, and if the bar temperatures are too low, it is automatically detected whether the pressing force is too long at its upper limit to initiate an increase in the bar temperature θ _Bk (I).