Method for operating a die-casting press with position control and die-casting press for carrying out the method

Abstract

Method for operating a die-casting press with a speed control of the injection piston (28), 1. wherein in a first process step at the beginning of the injection process the melt is injected into the casting cavity (25) at a slow speed, e.g. at a speed in the range between 100-300 mm / sec, 2. and in a second process step is injected into the casting cavity (25) at high speed, e.g. at a speed, e.g. in the range between 3000-10000 mm / sec, 3. wherein at least one first control valve (80) is arranged on the inlet side of the injection cylinder (27) and at least one second control valve (81) is arranged on the outlet side 4. and at least one control device is provided which controls at least one of the two control valves, 5. and regulates the filling speed of the injection cylinder with a control module (44), 6. characterized in that the controller structure of the control module (44, 44a) consists of a two-degrees-of-freedom controller, 7. namely, a parallel circuit consisting of an adaptive feedforward control (67) and a classical controller (70) with a closed control loop 8. that the adaptive feedforward control (67) calculates the control value for the servo valve (80, 81) as a function of the target speed, taking into account the adaptively estimated parameters that scale the initial parameters based on measured values, 9. which takes into account inaccurate initial parameters, temperature fluctuations, etc. 10. or that instead of adaptively estimated parameters, the adaptive feedforward control consists of a non-linear compensation of the hydraulic components to provide a desired highly dynamic control, 11. The combination of these two control mechanisms ensures that the open loop control feedforward first calculates the setpoint for the servo valve very accurately, and any deviations from this setpoint are compensated for by the classical controller, which further processes this value.

Description

[0001] The invention relates to a method for operating a die-casting press with position control and a die-casting press for carrying out the operation with position control of the injection piston according to the preamble of claim 1 or 2.

[0002] Die-casting presses of the type mentioned above are known, for example, from the subject matter of DE 10 2007 013 200 A1. Such die-casting presses are used for the production of die-cast parts with an associated casting device and essentially consist of a press frame with guide rods arranged therein and a die-casting tool which forms a cavity into which a hardenable casting compound is injected and hardens there.

[0003] The casting material is either zinc or aluminum or similar or other heat-treatable metal materials.

[0004] The subject matter of DE 10 2004 026 082 A1 discloses a process and a plant for die casting, from which a specific process sequence with control of the process parameters can be derived.

[0005] This publication describes how the closing speed of the tool is determined depending on the temperature and other parameters.

[0006] A disadvantage of the known die-casting machine, however, is its inadequate position control of the injection piston within the injection channel. In particular, the aforementioned design suffers from the drawback that the injection channel is not completely filled with the casting material by the end of the injection process, resulting in insufficient mold filling. Furthermore, it lacks a highly dynamic control system that would allow for rapid adjustments to various die-casting parameters, such as time and temperature conditions.

[0007] DE 2 305 593 A1 describes a control system of the same type for increasing the speed and acceleration of a hydraulic medium in conjunction with a metering cylinder in a die-casting machine.

[0008] The problem was identified that during die casting, a specific speed profile of the casting material should be followed, and the acceleration and speed parameters are dynamically changed so that a good result is achieved with a profile that has been determined once.

[0009] Although the publication addresses the problem of precisely controlling the speed of a hydraulic cylinder for injecting molten metal to a predetermined target speed, it presents a control system consisting of a multi-part hydraulically controlled main flow control valve 21, to which two different pressure medium sources 38, 51 are connected, which selectively and depending on the slides in the main flow valve apply pressure to the front and back of the hydraulic injection cylinder.

[0010] Mechanical throttle valves 64, 69 are provided for regulating the pressure in the injection cylinder; these are controlled by the mechanical control system. However, such hydraulic control in conjunction with a controllable main flow control valve cannot generate highly dynamic control of the feed rate of the hydraulic cylinder for the injection of the molten metal.

[0011] WO 2011 / 032918 A1 concerns a method unrelated to the general principles of process control for regulating heat flow in a reactor. This method provides control variables for process engineering operations with setpoint trajectories and records other process state variables. Control deviations are calculated, and from these, controller actuators are calculated using a control algorithm. Furthermore, feedforward actuators are determined, and the resulting actuators are calculated from the controller actuators and feedforward actuators and adjusted within the process.

[0012] In a preferred embodiment, the known control method is cascaded, wherein resulting manipulated variables of at least one master controller and at least one subordinate follower controller are calculated from the respective controller manipulated variables and their associated feedforward manipulated variables, wherein the structure of the control algorithm and / or the feedforward of the at least one follower controller is modified by a switching logic.

[0013] However, this method concerns the control of thermal processes at and within a reactor, such as the control of flow rate, temperature, or pressure. Such thermal processes are subject to relatively slow changes. Therefore, fast and highly dynamic control, as required for an injection cylinder of a die-casting machine, is not necessary, because, as described in DE 2 305 593 A1, the quality of the die-cast product is directly dependent on the highly dynamic velocity profile during the injection of the molten metal into the cavity.

[0014] The invention is therefore based on DE 2 305 593 A1 and aims to further develop a die-casting machine of the type mentioned above in such a way that the speed of the hydraulic cylinder for the injection of the molten metal can be controlled as precisely as possible to a predetermined target speed.

[0015] To solve the problem posed, the invention is characterized by the technical teaching of claim 1.

[0016] A feature of the invention is that the machine has a closing mechanism for the tool (“casting mold”), which is driven by the tool closing cylinder. Cavities are incorporated into the tool, which are to be quickly and completely filled with molten metal during the die-casting process in order to produce the desired product in high quality. The molten metal is fed into the inlet of the injection channel either with the assistance of a robot or manually and then forced into the tool at high speed by the injection cylinder. The speed profile during the injection process is essential for achieving good product quality. Therefore, there are high demands on the path planning and control accuracy of the injection cylinder. For this purpose, the invention uses a specific position control system, which is controlled by software.

[0017] The software can be summarized into a few key modules: - Operations management ◯ Coordinates general operating modes, etc. (e.g., manual or automatic mode) - Sequence control ◯ Coordinates the machine's processes and sends commands to the control system and the control valves. ◯ Manual mode: Depending on button press and sensor feedback, commands are sent for manual operation. • Automatic mode: Depending on the configuration / programming, the machine is coordinated through automatic operation, sending commands to the control system and valve stack. Depending on the configuration, communication also occurs with peripherals (removal or filling robots). - Monitoring ◯ Diagnostic functions ◯ Error detection ◯ Quality management ◯ Production Log - Regulation ◯ Controlling proportional valves to drive the specified speed profile as accurately as possible. ◯ Requirement for high dynamics / performance during operating point changes (from low to high speed in a given time with minimal overshoot) - Valve control ◯ Controlled valves are switched - Recipe and trajectory management ◯ Managing user input for configuring / programming the machine for a product

[0018] The purpose of the control system is to regulate the speed of the hydraulic cylinder used for injecting the molten metal as precisely as possible to the specified target speed. The challenge lies in the extreme speed changes required for the die-casting process. At the beginning of the injection process, the molten metal in the injection chamber is slowly (100-300 mm / sec) conveyed through the injection cylinder towards the mold, and then, at high speed (3000-10000 mm / sec), it fills the mold. The speed change must be completed within 15 milliseconds. Despite the use of a high-speed valve, the settling time is approximately 15 milliseconds according to current technology. Therefore, the challenge for the control system is to directly calculate the near-perfect setpoint for the valve. Furthermore, overshoot must be minimized. structure

[0019] The controller structure, in its initial iteration, corresponds to a two-degrees-of-freedom design. This consists of a combination of feedforward control (open-loop control) and a classical controller (closed-loop control). This refers to a parallel connection of adaptive feedforward control and a closed-loop control system.

[0020] A second implementation proposes an IMC control system. IMC stands for internal model control. This control system consists of a series connection of adaptive feedforward control and a preceding closed-loop control system.

[0021] According to the invention, both the parallel and series connection of adaptive feedforward control and a closed control loop are claimed.

[0022] The term "closed control loop" means that a control value is determined by comparing a setpoint with a measured actual value, and the resulting control deviation should be compensated for particularly quickly and dynamically. Adaptive feedforward control

[0023] Adaptive feedforward control is an important part of the controller design. Therefore, in a first implementation, an inverse hydraulic dynamics approach is proposed, which calculates the actuator value for the servo valve as a function of the target speed, taking into account the adaptively estimated parameters.

[0024] In a second version, the adaptive feedforward control consists of a non-linear compensation of the hydraulic components in order to provide a desired highly dynamic control. Adaptive parameter estimation

[0025] Based on measured values, the initial parameters can be scaled. This occurs at each time step during controlled operation. This allows for the compensation of inaccurate initial parameters, temperature fluctuations, etc. Pre-control function, especially in training as inverse hydraulic dynamics.

[0026] Here, the setpoint for the pilot valve is calculated. The estimated parameters are used to achieve the most accurate setpoint possible. regulator

[0027] A simple closed-loop control concept is used. This concept must compensate for relatively small control deviations. Currently, a PI controller is used, but this can be replaced by a variety of other control concepts. For vibration-prone systems (long and flexible hydraulic lines), a so-called linear quadratic controller (LQR) is preferred.

[0028] A feature of the invention is therefore a special, inventive controller structure that corresponds to a two-degrees-of-freedom design (parallel connection of adaptive feedforward control and closed-loop control) or an IMC design (series connection of closed-loop control and downstream adaptive feedforward control).

[0029] According to the invention, a combination of a feedforward control (open loop control) and a classic controller with a closed loop control is therefore used.

[0030] The combination of these two control mechanisms has the advantage that the open loop control feedforward first calculates the setpoint for the servo valve very precisely, and any deviations from this setpoint are compensated for by the classic controller, which processes this value further.

[0031] Of particular importance is that the inverse hydraulic dynamics directly calculates the setpoint for the servo valve, depending on the target speed and taking into account the adaptively estimated parameters.

[0032] Accordingly, an adaptive parameter estimation of the setpoints is proposed, in which the initial parameters are scaled based on measured values. This occurs at any desired time step during controlled operation. This allows inaccurate initial parameters, temperature fluctuations, and the like to be ideally compensated for.

[0033] The term "inverse hydraulic dynamics" means that the control value for the pilot valve is calculated, and the estimated parameters are used to find the perfect control value for the proportional drive of the injection piston as accurately as possible.

[0034] According to the invention, a PI controller is used for the closed control loop because a large number of control concepts can be implemented with it.

[0035] In another embodiment of the present invention, however, it is provided that the PI controller is replaced by a linear quadratic controller (LQR).

[0036] This means that a number of different controllers can be used for the closed-loop control system, such as PD controllers or PID controllers. The open-loop controller handles the feedforward control with adaptive parameter estimation, which calculates a specific feedforward function and provides it as the actuator value to the control valve.

[0037] However, the invention is not limited to a specific controller type (P, PI, PID, PD, etc.). All controller types according to the prior art can be used.

[0038] In a preferred embodiment of the invention, the control valve according to the invention is connected to the injection cylinder via a hydraulic line, in which the injection piston is arranged to be slidably driven.

[0039] The control valve is actuated by the control system according to the invention, which is shown in more detail in the block diagram of the drawings. The output of the control valve is connected to the tank into which the hydraulic fluid flows. The hydraulic fluid is returned to the pressure accumulator via a return flow or reused via hydraulic power units.

[0040] A feature of the invention is also that two differently functioning pressure accumulators are used, one of which is attached to the injection cylinder, while the other pressure accumulator is used via its own pressure cylinder to increase the pressure in the injection cylinder.

[0041] The first pressure accumulator works together with the control valve according to the invention and takes over the drive of the injection piston in the injection cylinder, wherein the pressure accumulator essentially consists of a gas pressure cushion, a diaphragm arranged therein and a hydraulic fluid located beyond the diaphragm, which directly takes over the pressure drive for the injection piston in the injection cylinder.

[0042] The second pressure accumulator, which is arranged parallel to the first pressure accumulator, also acts on the injection cylinder, but only indirectly via its own pressure cylinder.

[0043] According to the invention, the second pressure accumulator acts on the hydraulic fluid of the injection cylinder via a pressure piston with a larger cross-section.

[0044] The ratio of the cross-sectional area of ​​the piston head to the piston rod in the pressure cylinder is increased to provide an additional pressure increase in the injection cylinder shortly before the end of the injection process into the mold.

[0045] The second pressure accumulator serves to pre-pressurize the hydraulic fluid in the injection cylinder during the process step when increased pre-tensioning of the injection piston is required after it has injected the liquid medium into the mold cavity, just before it reaches its final position. In this position, the injection piston is advanced with increased thrust by means of the second pressure accumulator.

[0046] Furthermore, the invention is not dependent on the precise design of a die-casting machine. Any die-casting machine belonging to the prior art can be used.

[0047] In a preferred embodiment of the invention, however, it is specified that the tool holder plate is connected via a multi-joint arrangement to a piston rod which drives the tool holder plate in a displaceable manner, so that with this multi-joint arrangement between the driving piston rod and the tool holder plate it is always ensured that the tool holder plate is moved in the die casting machine in the correct position and angle in each process step.

[0048] The two alternative control structures offer the advantage of highly dynamic control of the two control valves of the injection cylinder in a metal die-casting machine. The control values ​​required for the valves are provided with high precision and speed. Control overshoot is reliably prevented.

[0049] Thus, the predetermined speed profile of the injection cylinder's movement is followed and maintained, largely compensating for environmental and material influences. Therefore, the speed profile is independent of the melt's material properties, and physical environmental parameters (temperature fluctuations of the ambient air or fluid, production-dependent variations in valve properties, frictional forces, pressures in the pressure accumulator, etc.) are compensated for.

[0050] The invention is explained in more detail below with reference to drawings illustrating only one embodiment. Further essential features and advantages of the invention will become apparent from the drawings and their description.

[0051] They show: Fig. 1: Schematic representation of a die-casting machine in an embodiment of the invention Fig. 2: an identical representation as Fig. 1. With the tool shape open, showing further details. Fig. 3: the representation according Fig. 2 with closed tool shape Fig. 4: Schematic representation of the software structure of the control system Fig. 5: A block diagram of the adaptive parameter estimation Fig. 6: Graphical representation of the approximation of the adaptive value to the unknown, real parameter value Fig. 7: A functional circuit diagram of the valve control system according to the invention with adaptive parameter estimation in a two-line-of-freedom design (parallel circuit) Fig. 8: a functional circuit diagram of the valve control according to the invention with an adaptive parameter estimation as an IMC design (series connection).

[0052] In a press frame 1, which is only indicated, pairs of guide rods 2, 3 are arranged parallel to each other, with a total of four guide rods being present and only the front guide rods of the pairs of guide rods 2, 3 being shown in the illustration.

[0053] A tool mounting plate 4 is slidably mounted on the guide rod pairs 2, 3 and the guide rod pairs 2, 3 are each attached at their ends in cross yokes 5, 6 in the press frame 1.

[0054] A spindle rod 7, 8 engages at the end of each pair of guide rods 2, 3, with the spindle rods 7, 8 being arranged in pairs. For the sake of simplification in the drawing and description, however, it will only be described that there is one spindle rod 7, 8 in each case, even though the spindle rods 7, 8 are arranged in pairs.

[0055] Each spindle rod 7, 8 engages in an associated spindle nut 9, 10, which is rotatably driven, wherein the respective spindle nut 9, 10 is located in a transverse plate 85 in which a rotary drive for the spindle nuts 9, 10 (not shown in detail) is arranged.

[0056] In this transverse plate 85, in which the spindle nuts 9, 10 are arranged, a tool locking cylinder 11 is arranged, which has a piston consisting of the piston rod 12 and the piston 13 connected thereto.

[0057] The piston 13 is arranged in a tool locking cylinder 11, which is under a predetermined hydraulic pressure.

[0058] The valve arrangement associated with the tool locking cylinder 11 is a simple sliding actuator, wherein the piston rod 12 acts on the tool mounting plate 4 via a multi-joint arrangement which is in Fig. 2 is shown schematically.

[0059] The displacement drive onto the piston rod 12 in the directions of arrow 20 is therefore effected via two connecting rods 15 arranged at an angle to each other, which are articulated to the rear of the tool mounting plate 4 via pivot points 17.

[0060] The connecting rods 15 are supported by further connecting rods 16, which are attached at an angle to the connecting rods 15 and are connected via their pivot points 19 to the transverse plate 85, which accommodates the spindle nuts 9, 10. The transverse plate 85 is thus displaceable in the directions of arrow 20.

[0061] The multi-joint arrangement is therefore used in Fig. 2 a knee joint 14 is described which always ensures that the drive piston with the piston rod 12 acts in the correct position and without tilting on a sliding drive for the tool mounting plate 4 in the direction of arrow 20.

[0062] In the tool mounting plate 4 an ejection piston 21 is arranged, which protrudes into the tool cavity with its free end.

[0063] The ejection piston 21 extends into Fig. 1 The two-part tool, which consists of the rear tool part 22 and the front tool part 23. The two tool parts 22, 23 are shown in the open state and form a cavity 24 between them, in which, when the tool parts 22, 23 are closed, the hardenable metal material is injected into the casting cavity 25 formed thereby.

[0064] The right tool part 23 is fixed, while the left tool part 22 is movable in the directions of arrow 20. It is moved together with the tool holder plate 4.

[0065] An injection channel 26 opens into the casting cavity 25 located in the right-hand part 23 of the tool, through which the curable metal material is injected. This is done by means of an injection piston 28, which is slidably driven in an injection cylinder 27.

[0066] A first pressure accumulator 32 is connected to the injection cylinder 27 in a fluid-conducting manner. This accumulator consists of a fluid chamber 33 filled with a suitable hydraulic fluid. The fluid chamber 33 is separated from a gas space 34 located above it by a diaphragm 35. The gas space 34 is filled with a pressurized gas medium, so that the hydraulic fluid is under pressure.

[0067] The hydraulic fluid for the pressure supply of the injection cylinder 27 is located in the fluid chamber 33.

[0068] It is only schematically shown that two connecting channels 40 are arranged side by side in pairs, wherein a proportional valve 80 according to the invention is arranged in one connecting channel, which is directly connected to the injection cylinder 27 in a fluid-conducting manner and determines the pressure in conjunction with a second control valve 81 located on the outflow side of the injection cylinder 27.

[0069] The control valve 81 is connected to the injection cylinder 27 via a hydraulic line 82, and its outlet side leads into a tank 83 for receiving the hydraulic fluid, the outlet of the tank being provided as a return flow 84 for the first pressure accumulator 32.

[0070] A second pressure accumulator 36 is present, which in a specific process step provides additional pressure for the hydraulic fluid in the injection cylinder 27.

[0071] It in turn consists of an upper gas chamber 38, which is connected to the fluid 37 via a diaphragm 39. The fluid is connected to the pressure cylinder 30 located there via a connecting channel 41 and a proportional valve (not shown) arranged there.

[0072] The cross-section of the pressure cylinder 30 is larger than the cross-section of the injection cylinder 27. A pressure piston 31 is slidably driven in the pressure cylinder 30, which consists of the piston rod 31a and the piston head 31b.

[0073] By pressurizing the pressure piston 31, a high pressure force is exerted on the pressure piston 31, which acts directly on the injection cylinder 27, with a greater pressure than the injection piston 28 in the injection cylinder 27.

[0074] In this way, by pressurizing the second pressure accumulator 36, a high feed force is exerted in the injection cylinder 27 when the injection piston 28 has moved in its forward position towards the casting cavity 25, in order to enable additional pressurization of the injection piston 28 at the end of the injection process into the casting cavity 25.

[0075] For the additional pressure application with the pressure piston 31, the diameter of the piston rod 31a is decisive, namely the ratio of the diameter of the piston rod 31a to the diameter of the piston head 31b.

[0076] The Fig. 2 and Fig. 3 show the same parts as in Fig. 1 with illustration of further details, which are in Fig. 1 are shown only schematically. The same reference numbers and the same explanation apply to the same parts.

[0077] In Fig. Figure 4 schematically depicts the machine control 42 of the die-casting machine, where the parts are only specified as functional parts.

[0078] In the area of ​​machine control 42, a sequence control 43 is arranged, which is connected to various external signal sources.

[0079] In the process step “Monitoring”, all processes are monitored, which means that the control processes can be displayed and monitored in the monitoring device 61.

[0080] This monitoring module 61 is connected to the sequence control 43 via a signal path 64.

[0081] Furthermore, signal path 64 acts on an operating control module 62. The operating control module 62 performs the overall coordination of the die-casting machine, which means determining which operating mode should be executed. Such an operating mode can be, for example, automatic or manual operation.

[0082] Furthermore, an input module 65 is provided in which the composition of the melt and the product-specific properties are graphically displayed and entered. Additional external parameters can be entered, which are then converted into corresponding trajectories in order to be fed as converted and adapted parameters via the signal path 66 of the sequence control 43.

[0083] It is important that the sequence control 43 is connected to the operating control module 62 via a signal path 47, which is designed as feedback, in order to receive feedback as to whether the sequence control 43 is working in the desired way.

[0084] Furthermore, the operating management system acts on the sequence control 43 via the signal path 63 in order to feed the higher-level operating parameters into the sequence control 43.

[0085] Thus, the operating mode is fed into the sequence control 43 via signal path 63.

[0086] The sequence control 43 acts on the output side via a signal path 46 on a control / valve control, which is subsequently referred to as control module 44.

[0087] The control module 44 acts via a signal path 45 back on the input of the sequence control 43 in order to enable feedback of the control parameters from the control module 44 to the sequence control 43.

[0088] The output of the control module 44 acts via the signal path 48 on an input and output module 49, in which the inputs 60 for the sensor signals are entered on the input side, and the cable connections 50 for the control of the valves 80, 81 and further valves of the hydraulic control are provided on the output side.

[0089] The input and output module 49 has additional outputs for controlling light displays, control displays and the like.

[0090] In Fig. Figure 7 shows the control module 44 according to the invention in a further more detailed representation.

[0091] Overall, this functional diagram reveals Fig. 7 can be seen that an adaptive feedforward control 67 is present, which essentially consists of an inverse hydraulic dynamics 68 and an associated adaptive parameter estimation 69.

[0092] The adaptive feedforward control 67 makes - as will be shown later - an approximate estimate of the output value for the valves 81, 80, whereby the output value is added to the value of the controller 70 in the adder 75.

[0093] Thus, according to the invention, a preliminary estimate of the output value for the control of the valves 80, 81 is made via an adaptive feedforward module, and this estimated value is added to the output value of the controller 70 via the controller output 64 in the adder 75, wherein the estimated value is provided via the signal path 76 by the adaptive feedforward 67.

[0094] In detail, it is explained that first a setpoint, for example for a target speed, is fed via the signal path 71 of the adaptive feedforward control 67 and there into the inverse hydraulic dynamics 68.

[0095] The inverse hydraulic dynamics 68 specifies a valve position for the injection piston. The module of the inverse hydraulic dynamics 68 performs a conversion of the desired velocity or volume flow rate with respect to a threshold value of the valves.

[0096] It is important that the signal path 71 acts directly on the inverse hydraulic dynamics, but is also fed in parallel to the controller 70 via the signal path 71, so that both the adaptive feedforward control 67 and the controller 70 receive the same setpoint signals in parallel via the signal path 71.

[0097] Further measured values ​​are fed in via signal path 72, such as the sensor values ​​from the pressure accumulators 32, 36, the signals from sensors that detect the valve position, the signals from the sensors that detect the cylinder pressure, and so on.

[0098] The signals from the sensors on the signal path 72 are fed into an adaptive parameter estimation 69 and supplied to the inverse hydraulic dynamics 68 via a parallel branch.

[0099] For the sake of clarity, it is also shown that further values ​​are fed in, for example, that the actual values ​​recorded by sensors, such as the measured speed of the injection piston, are fed in via signal path 73.

[0100] This signal path 73 also goes in parallel to both the adaptive parameter estimation 69 and the controller 70, so that both modules 67, 70 receive the same input signals in parallel.

[0101] This means that the adaptive feedforward control 67 achieves an independent approximation to the desired control value, which is processed in a separate computing circuit in the controller 70. Both values ​​are fed to the adder 75 via signal paths 74 and 76a, which then forms a common control value on signal path 76. This value is used directly or indirectly to control the valves 80 and 81. This results in a particularly dynamic and highly accurate approximation to the control value by using two separate computing modules in parallel: the adaptive feedforward control 67 and the controller 70, both of which receive the same values.

[0102] It is important that the determined setpoint on signal path 76 is also fed back via signal path 77 to the adaptive parameter estimation 69, so that a specific actual value is always entered into the adaptive parameter estimation 69.

[0103] The other inputs of the parameter estimation 69 are formed by the signal paths 72 and 73.

[0104] These are therefore two different control modules, namely a control module for adaptive feedforward control 67 and another control module via the controller 70, which - according to the general description - can be designed as a PD controller, as a PID controller or as a PI controller.

[0105] Other possible embodiments of such a controller were mentioned in the general description.

[0106] With reference to Fig. It is also mentioned in section 7 that the output of the adaptive parameter estimation 69 is connected to the input of the inverse hydraulic dynamics 68 via a signal path 78.

[0107] In Fig. Figure 5 schematically depicts a functional diagram for the adaptive parameter estimation 69. It can be seen that the measured values ​​are fed in via signal paths 72 and 73, which are then used to determine the parameters. Fig. 7 described. In the adaptive parameter estimation 69, a computing module is arranged which calculates an estimated output value from a conversion of the input measured values, via a differential equation and an adaptive estimation, which is made available on the signal path 78.

[0108] The signal path 78 is fed back via the signal path 79, and the signal is then available at the output of this computing module, which is fed into the inverse hydraulic dynamics 68.

[0109] The important aspect of the present invention is therefore that a highly dynamic, fast and accurate control of the feed rate of the injection piston takes place via two independent controllers whose control signals are linked together in a specific way.

[0110] With the adaptive feedforward control 67 in Fig. 7. A rapid approximation to a desired value takes place, which was previously unknown. Accordingly, a control value for the feedforward control is calculated highly dynamically from the available values ​​via the adaptive feedforward control 67, and a second value is determined in parallel by the controller 70 itself. Both values ​​are combined in the adder 75 and used as a control value for the valves 80, 81 according to the invention for the highly dynamic control of the injection piston.

[0111] This is in Fig. Figure 6 is shown. The abscissa represents time, and the ordinate represents the parameter value of the hydraulic model. For simplicity, only one parameter value of the model is shown, which does not necessarily represent a physical value. It is a calculated value within the hydraulic model.

[0112] The adaptive parameter estimation 69 (see Fig. 7 or Fig. 8) estimates the actual parameter value.

[0113] Initially, an estimated parameter value is assumed at position 86, and an algorithm ensures that this estimated parameter value 86 is gradually adapted to the target curve 88 as an adaptive parameter curve 87 over a time interval 89. This achieves a stable estimate of the parameter value within a short time. The estimated parameter thus converges to the unknown parameter 88 as a stable trend curve.

[0114] This makes it possible for the first time to further develop a die-casting machine of the type mentioned above in such a way that a precisely specified speed profile can be driven, and the requirement for dynamics / performance during a change of operating point (from low to high speed in a specified time with minimal overshoot) can be met.

[0115] The Fig. Figure 8 shows the second controller structure as an IMC design with a series connection of the closed control circuit with the controller 70 and the downstream adaptive feedforward control 67. The output 74 of the controller 70 acts directly on the input of the inverse hydraulic dynamics 68, whose output path 76 directly specifies the control value for the valves 80, 81.

[0116] Compared to Fig.7. Instead of adding two different control signals, a single control signal is generated via a single signal path 76. This offers the advantage that non-linear, critically controlled hydraulic valves can be controlled reliably and without overshoot. Drawing legend 1 press frame 2 pairs of guide rods 3 pairs of guide rods 4 Tool mounting plate 5 Cross yoke 6 Cross yoke 7 Spindle rod 8 Spindle rod 9 Spindle nut 10 Spindle nut 11 tool lock cylinders 12 Piston rod 13 pistons 14 Knee joint 15 Joint rod 16 Joint rod 17 joint points 18 joint points 19 joint points 20 Arrow direction 21 Ejection pistons 22 Tool part 23 Tool part 24 Cavity 25 Casting cavity 26 injection channels 27 injection cylinders 28 injection pistons 29 Piston head 30 pressure cylinders 31 Pressure piston 31a Piston rod 31b Piston head 32 pressure accumulators 33 Fluid chamber 34 Gas chamber 35 Membran 36 pressure accumulators 37 Fluid 38 Gas space 39 Membran 40 connection channel 41 Connection channel 42 Machine control 43 Process control 44 Control module 45 Signal path 46 Signal path 47 Signal path 48 Signal path 49 Input and output module 50 cable connection 60 inputs for sensor signal 61 Monitoring module 62 Operations Management Module 63 Signal path 64 Signal path 65 Input module 66 Signal path 67 adaptive feedforward control 68 inverse hydraulic dynamics 69 adaptive parameter estimation 70 controllers 71 Signal path 72 Signal path 73 Signal path 74 Controller output 75 Adders 76a Signal path 76 Exit path 77 Signal path (feedback) 78 Signal path 79 Signal path (feedback) 80 Proportional valve 81 Control valve 82 Hydraulic line 83 Tank 84 Backflow 85 cross plate 86 Position (initial value of the parameter estimate) 87 adaptive parameter curve 88 unknown real parameter value 89 time interval 90 Form cylinders 91 Proportional valve 92 Management

Claims

Method for operating a die-casting press with a speed control of the injection piston (28), 1. wherein in a first process step, at the beginning of the injection process, the melt is injected into the casting cavity (25) at a slow speed, e.g., at a speed in the range between 100 and 300 mm / sec, 2. and in a second process step, it is injected into the casting cavity (25) at a high speed, e.g., at a speed in the range between 3000 and 10000 mm / sec, 3. wherein at least one first control valve (80) is arranged on the inlet side of the injection cylinder (27) and at least one second control valve (81) is arranged on the outlet side, 4. and at least one control device is provided which actuates at least one of the two control valves, 5. and regulates the filling speed of the injection cylinder with a control module (44), 6.characterized in that the control structure of the control module (44, 44a) consists of a two-degrees-of-freedom controller, 7. namely a parallel connection of an adaptive feedforward control (67) and a classical controller (70) with a closed control loop, 8. that the adaptive feedforward control (67) calculates the setpoint for the servo valve (80, 81) as a function of the target speed, taking into account the adaptively estimated parameters, which scale the initial parameters based on measured values, 9. thereby taking into account inaccurate initial parameters, temperature fluctuations, etc., 10. or that instead of the adaptively estimated parameters, the adaptive feedforward control consists of a non-linear compensation of the hydraulic components in order to provide a desired highly dynamic control, 11.The combination of these two control mechanisms ensures that the open loop control feedforward first calculates the setpoint for the servo valve very accurately, and any deviations from this setpoint are compensated for by the classic controller, which further processes this value. Method for operating a die-casting press with speed control of the injection piston (28), 1. wherein in a first process step, at the beginning of the injection process, the melt is injected into the casting cavity (25) at a slow speed, e.g., at a speed in the range between 100-300 mm / sec, 2. and in a second process step, it is injected into the casting cavity (25) at a high speed, e.g., at a speed in the range between 3000-10000 mm / sec, 3. wherein at least one first control valve (80) is arranged on the inlet side of the injection cylinder (27) and at least one second control valve (81) is arranged on the outlet side, 4. and at least one control device is provided which actuates at least one of the two control valves and regulates the filling speed of the injection cylinder with a control module (44), characterized in that 5.The control structure of the control module (44, 44a) consists of an IMC control module (44a), namely a series connection of a classical controller (70) with a closed-loop control system and an adaptive feedforward control (67).

6. The adaptive feedforward control consists of a non-linear compensation of the hydraulic components to provide the desired highly dynamic control.

7. The initial parameters are scaled based on measured values, thereby compensating for inaccurate initial parameters, temperature fluctuations, etc.

8. The setpoint for the valve (80, 81) of the feedforward control is calculated by using the estimated parameters to achieve the setpoint as accurately as possible. 9.The combination of these two control mechanisms ensures that the open loop control feedforward first calculates the setpoint for the servo valve very accurately, and any deviations from this setpoint are compensated for by the classic controller, which further processes this value. Method according to claim 1 or 2, characterized in that the adaptive feedforward control (67) performs an approximate estimation of the output value for the valves (81, 80), that the output value is added to the value of a controller (70) in an adder (75), that a preliminary estimate of the output value for the control of the valves (80, 81) is made via the adaptive feedforward control module and this estimated value is added to the output value of the controller (70) via a controller output (64) in the adder (75), wherein the estimated value is provided by the adaptive feedforward control (67) via a signal path (76). Method according to claim 2 or 3, characterized in that the adaptive feedforward control (67) consists of a combination of an inverse hydraulic dynamics (68) or a non-linear compensation and an adaptive parameter estimation (69). Method according to one of claims 1 to 4, characterized in that the controller (70) is a controller with feedback of the measured variables and interpretation of the setpoint and is preferably designed as a classical controller (70), e.g. as a PI and / or a PD and / or a PID controller. Method according to one of claims 1 to 5, characterized in that at the input of the inverse hydraulic dynamics (68) the setpoint of the speed of the injection piston (28) and the measured values ​​of at least one pressure accumulator (32, 36) as well as the measured value of the cylinder pressure in the injection cylinder (27) and the measured values ​​of the valve position of the control valves (80, 81) are present and at the output the actuating value for the at least one control valve (80, 81) is generated as a function of the setpoint speed of the injection piston (28) taking into account the output values ​​of the adaptive parameter estimation (69). Method according to one of claims 1 to 6, characterized in that the adaptive parameter estimation (69) processes the measured values ​​from sensors of the pressure accumulators (32, 36), the cylinder pressures in the injection cylinder (27) and the valve control of the control valves (80, 81) together with the actual value of the current speed of the injection cylinder (27) and that its output is switched to the input of the inverse hydraulic dynamics. Method according to one of claims 1 to 7, characterized in that the control value for the pilot valve is estimated using inverse hydraulic dynamics (68) and is used for rapid adaptive approximation to the exact control value of the control valves (80, 81). Method according to one of claims 1 to 8, characterized in that the classical controller (70) only compensates for small control deviations between the setpoint of the target velocity of the injection piston (28) and the actual value of the measured velocity of the injection piston (28). Method according to one of claims 1 to 9, characterized in that the sum signal formed by the adder (75) is fed in as feedback to the adaptive parameter estimation (69). Device for carrying out the method according to at least one of claims 1 to 10, characterized in that the hydraulic fluid in the injection cylinder (27) for the feed drive of the injection piston (28) is under the preload pressure of two parallel connected pressure accumulators (32, 36). Device according to claim 11, characterized in that one of the two pressure accumulators (36) actuates a pressure piston (31) which applies additional pressure to the hydraulic fluid in the injection cylinder (27) at the end of the injection, and that the other pressure accumulator (32) drives the hydraulic fluid for the feed drive of the injection piston (28).

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