METHOD AND SYSTEM FOR DAMPING SLOSHING MOLTEN METAL

Abstract

The disclosed method is a control to suppress sloshing in a ladle of a pouring device and a mold caused by their movements. A plurality of flasks, each of which contains a conveyed mold, is arranged linearly between an electric pusher-cylinder and an electric cushion-cylinder. In the method, a first natural frequency of the molten metal in the ladle is calculated based on a predetermined relationship between the weight and the natural frequency for the molten metal in the ladle, and the measured weight of the molten metal in said ladle. Also, a second natural frequency of the molten metal in said mold is calculated based on a predetermined relationship between the weight and the natural frequency for the molten metal in the mold, and the measured weight of the molten metal in the mold. The first and second natural frequencies are entered in a filtering circuit to modify a velocity waveform of the movement of conveying the flasks such that the modified velocity waveform does not include the first and second natural frequencies. The electric pusher-cylinder and the electric cushion-cylinder are driven such that the velocity waveform of the movement of conveying the flasks is said modified velocity waveform.

Description

FIELD OF THE INVENTION

The present invention generally relates to a control for a casting line. In particular the present invention relates to a method and a system for damping the sloshing that occurs in molten metal in a ladle and a mold in the casting line.

BACKGROUND OF THE INVENTION

Patent publication 1, listed below, discloses one example of the conventional casting line in which a conveying line for conveying molds is provided with an encoder to detect the rate of feeding a mold. Responding to the detection signal of the encoder, a pouring device tracks, and synchronizes with the conveying mold, such that the pouring device moves to the proper position, i.e., where a ladle of the pouring device pours molten metal into the mold.

Reference of Prior-Art Document

• Patent Citation 1: Japanese Patent No. 3113950 (Isuzu Manufacturing Co., Ltd.)

In such a conventional casting line, because cylinders push out and thus convey a flask that contains the mold and the pouring device, the velocity waveform of the flask or the pouring device has a waveform that is generally trapezoidal when it is moved for conveying. This involves sloshing the molten metal in the ladle of the pouring device and the mold to cause the fluid level of the molten metal to ripple. As a result, a casting piece may contain a sand inclusion or a casting fin that adversely affects the quality of the cast product.

Accordingly, there is a need for a method and a system for damping sloshing that occurs in molten metal in a ladle and a mold in a casting line where a process of pouring is automatic.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a method and a system of suppressing sloshing in a casting line that includes a conveying line in which an electric pusher-cylinder is located at one end of the conveying line for intermittently pushing out a plurality of flasks, each containing a mold, one by one. It also includes an electric cushion-cylinder that is located at the other end of the conveying line such that it is opposed to the electric pusher-cylinder so as to receive and cushion a group of the pushed flasks such that the conveying line conveys the plurality of flasks, which are arranged linearly between the electric pusher-cylinder and the electric cushion-cylinder; and an automatic pouring device that has a ladle for containing molten metal and that can be moved in synchronization with the flask on the conveying line, to pour the molten metal into the mold by tilting the ladle. The method and system control the electric pusher-cylinder and the electric cushion-cylinder using a controller having filtering means such that the sloshing that occurs in the molten metal is suppressed when the ladle and the mold move a distance that corresponds to one flask.

The method comprises: calculating a first natural frequency of the molten metal in the ladle based on a predetermined relationship between the weight and the natural frequency for the molten metal in the ladle, and the measured weight of the molten metal in the ladle, and calculating a second natural frequency of the molten metal in the mold based on a predetermined relationship between the weight and the natural frequency for the molten metal in the mold, and the measured weight of the molten metal in the mold; entering the first and second natural frequencies in the filtering means to modify a velocity waveform of the movement of conveying the flasks such that the modified velocity waveform does not include the first and second natural frequencies; and driving the electric pusher-cylinder and the electric cushion-cylinder such that the velocity waveform of the movement of conveying the flasks is the modified velocity waveform.

The system comprises: a first weight-calculation means for calculating the weight of the molten metal in the ladle; a second weight-calculation means for calculating a second natural frequency of the molten metal in the mold; a first natural frequency-calculation means for calculating a first natural frequency based on a predetermined relationship between the weight and the natural frequency for the molten metal in the ladle, and the calculated weight of the molten metal in the ladle by the first weight-calculation means; a second natural frequency-calculation means for calculating a second natural frequency based on a predetermined relationship between the weight and the natural frequency for the molten metal in the mold, and the calculated weight of the molten metal in the mold by the second weight-calculation means; a filtering means for modifying a velocity waveform of the movement of conveying the flasks on the conveying line such that the modified velocity waveform does not include the first and second natural frequencies calculated by the first and second natural frequency-calculation means; and an instructing means for providing operating instructions to the electric pusher-cylinder, the electric cushion-cylinder, and the automatic pouring device, based on the modified velocity waveform.

A second aspect of the present invention provides a method and a system of suppressing sloshing in a casting line, wherein the casting line includes: a conveying line in which an electric pusher-cylinder is located at one end of the conveying line for intermittently pushing out a plurality of flasks that each contains a mold, one by one, and an electric cushion-cylinder that is located at the other end of the conveying line that is opposed to the electric pusher-cylinder to receive and cushion a group of the pushed flasks such that the conveying line conveys the plurality of flasks that is arranged linearly between the electric pusher-cylinder and the electric cushion-cylinder; an automatic pouring device that has a ladle for containing molten metal and that can be moved in synchronization with the flask on the conveying line, to pour the molten metal into the mold by tilting the ladle; driving means for driving the electric pusher-cylinder, the electric cushion-cylinder, and the automatic pouring device along the conveyed direction of the flasks; controlling means for controlling the driving means; and instructing means for providing operating instructions for the electric pusher-cylinder, the electric cushion-cylinder, and the automatic pouring device to the driving means through the controlling means.

The method and the system control the casting line using a controller having filtering means, based on a feedforward control program such that the sloshing that occurs in the molten metal is suppressed when the ladle and the mold move a distance corresponding to one flask.

The method of the second aspect comprises: calculating a first natural frequency of the molten metal in the ladle based on a predetermined relationship between the weight and the natural frequency for the molten metal in the ladle, and the measured weight of the molten metal in the ladle, and calculating a second natural frequency of the molten metal in the mold based on a predetermined relationship between the weight and the natural frequency for the molten metal in the mold, and the measured weight of the molten metal in the mold; under the first natural frequency, the second natural frequency, and parameters on the controlling means that are preliminarily calculated such that they do not exceed the capacities of the driving means and that are stored, removing components that are located near the first and second frequencies from the operating instructions, in which the maximum value of at least one of a velocity of the movement, an acceleration of the movement, and a jerk of the ladle and the mold is restricted, by the filtering means using the stored parameters, wherein the components to be removed are decided based on a simulation using a model representing the characteristics of the casting line to repeatedly calculate the components by the following equation (1) or (2), while gradually varying filtering parameters ai(f), bj(f) that are parameterized by a resonance frequency f that are successively calculated from the molten metal in the ladle and the mold; and entering the operating instructions, in which the components located near the first and second frequencies have been removed, in the controlling means based on only the feedforward controlling program, to operate the driving means based on only the feedforward controlling program without using a feedback control program.

$\begin{array}{cc}\left[\mathrm{Math}.1\right]& \\ y\left(t\right)=b_0\left(f\right)x\left(t\right)+b_1\left(f\right)x\left(t-1\right)+b_2\left(f\right)x\left(t-2\right)+\dots -a_1\left(f\right)y\left(t-1\right)-a_2\left(f\right)y\left(t-2\right)-\dots y\left(t\right)=\sum _{j=0}^mb_j\left(f\right)x\left(t-j\right)-\sum _{i=1}^na_1\left(f\right)y\left(t-i\right)& \left(1\right)\end{array}$

where x(t-j) is a time-series data that is input before j controlling cycles, and y (t-i) are a time-series data that are output before i controlling cycles.

$\begin{array}{cc}\left[\mathrm{Math}.2\right]& \\ \begin{array}{c}F\left(S\right)=\frac{Y\left(S\right)}{X\left(S\right)}\\ =\frac{b_0\left(f\right)S^0+b_1\left(f\right)S^1+b_2\left(f\right)S^2+\dots }{a_0\left(f\right)S^0+a_1\left(f\right)S^1+a_2\left(f\right)S^2+\dots }\\ =\frac{\sum _{j=0}^mb_j\left(f\right)S^j}{\sum _{i=0}^na_i\left(f\right)S^i}\end{array}& \left(2\right)\end{array}$

where S is the Laplace operator, and equation (1) can be derived by applying a Z transformation on the transfer function of the filter that is expressed as equation (2).

As stated above, restricting the maximum value of at least one of a velocity of the movement, an acceleration of the movement, and a jerk of the movement, of the ladle and the mold can ensure that the driving means of the casting line prevents an excess, in particular, of the acceleration of the automatic pouring device and the flasks. Further, removing the components of the resonance frequencies by filtering the operating instructions to convey the flasks can prevent the efficiency of the control means of the driving means of the casting line from significant degradation, even if the detected weights of the molten metal in the ladle and the mold involves a detected error.

The system of the second aspect comprises: a first weight-calculation means for calculating the weight of the molten metal in the ladle; a second weight-calculation means for calculating a second natural frequency of the molten metal in the mold; a first natural frequency-calculation means for calculating a first natural frequency based on a predetermined relationship between the weight and the natural frequency for the molten metal in the ladle, and the calculated weight of the molten metal in the ladle by the first weight-calculation means; a second natural frequency-calculation means for calculating a second natural frequency based on a predetermined relationship between the weight and the natural frequency for the molten metal in the mold, and the calculated weight of the molten metal in the mold by the second weight-calculation means; an instructing means for providing operating instructions based on a feedforward program for operations of the electric pusher-cylinder, the electric cushion-cylinder, and the automatic pouring device, to the driving means through the controlling means; a parameter calculation means for preliminarily calculating the parameters of the controlling means such that the calculated parameters do not exceed the capacity of the driving means; a stored means for receiving and storing the calculated parameters from the parameter calculation means; a restriction means for restricting the maximum value of at least one of a velocity of the movement, an acceleration of the movement, and a jerk of the automatic pouring device and the mold; a filtering means for receiving the first and second resonance frequencies from the first and second frequency-calculation means, and for removing components that are located near adjacent to the first and second frequencies from the operating instructions, in which the maximum value is restricted by the restriction means, using the stored parameters from the stored means, wherein the components to be removed are decided based on a simulation using a model representing the characteristics of the casting line to repeatedly calculate the components, under the stored parameters, by the above equation (1) or (2), while gradually varying filtering parameters ai(f), bj(f) that are parameterized by a resonance frequency f that are successively calculated from the molten metal in the ladle and the mold, and wherein the instructing means provides the controlling means with the operating instructions in which the components located near the first and second frequencies are removed such that the controlling means carries out the controls based on only the feedforward controlling program, without using a feedback control program.

As used herein, the term “filtering means” refers to a circuit or its partial configuration that includes a pair of an input terminal and an output terminal with a transfer function therebetween that has a frequency response.

As used herein, the term “feedforward control” refers to way to control a manipulative variable to be applied to a controlled object to a predetermined value such that output value is a target value. The feedforward control may provide a highly efficient control if an input-output relation and a disturbance, for example, to the controlled object, are definite.

As used herein, the term “jerk” refers to a rate of deviation in an acceleration relative to the time.

The forgoing and the other features and objects of the present invention will also be obvious from the following descriptions by referring to the accompanied drawing. Note that the various embodiments of the present invention are not intended to be limited to the illustrated arrangements and means.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic block diagram of one embodiment of the casting equipment to which the present invention is applied.

EMBODIMENT OF THE INVENTION

The First Embodiment

FIG. 1 shows casting equipment to which the method and the system of the present invention is applied. The casting equipment includes a casting line in which a conveying line A conveys a plurality of flasks. Each contains a mold Y to a conveyed direction designated by an arrow X, arranged linearly, such that the casting line carries out casting processes using the conveyed flasks. For the ease of understanding the illustration, each flask is schematically shown as a contour of the corresponding Y. Arranged on the casting line are an electric pusher-cylinder B, an electric cushion-cylinder C, and an automatic pouring device D. The electric pusher-cylinder B is located at one end of the conveying line A for the flasks to intermittently push out the plurality of flasks one by one. The electric cushion-cylinder C is located at the other end of the conveying line A that is opposed to the electric pusher-cylinder B to receive and cushion a group of the pushed flasks. The automatic pouring device D, which has a ladle Z for containing molten metal, can be moved in the direction X in synchronization with the flask on the conveying line A, to pour the molten metal into the mold by tilting the ladle Z. The automatic pouring device D is provided with a driving motor (driving means), not shown, to move it in the direction X. Although the automatic pouring device D is also provided with a plurality of motors (not shown) to let the ladle Z move vertically, forward and backwards, and tilt, explanations for these motors to move the ladle Z are omitted. The casting equipment is also provided with a system to control a controller having a filter circuit, using a program to control the operations of the electric pusher-cylinder B, the electric cushion-cylinder C, and the automatic pouring device D, in the casting line.

On the electric pusher-cylinder B and the electric cushion-cylinder C, induction motors (driving means) B1 and C1 for driving the respective ball screws are mounted as driving motors to move them in the direction X. The induction motors B1 and C1 are electrically connected to a first servo controller (controlling means) B3 and a second servo controller (controlling means) C3 through inverters B2 and C2 that can control the position by entering data on a pulse string.

The control system includes, besides the first and second servo controllers B3 and C3 described above, a control unit J for the automatic pouring device D to control the X driving motor to drive the automatic pouring device D in the X direction (and the driving motors to drive the ladle Z) and a control device K for the conveying line of the flasks to control the first and second servo controllers B3 and C3. The control system also includes the following functions: a first weight-calculating means for calculating the weight of the molten metal in the ladle Z; a second weight calculating means for calculating the weight of the molten metal in the mold Y; a first natural frequency calculating means for calculating the natural frequency (the first natural frequency) of the molten metal in the ladle Z based on a predetermined relationship between the weight and the natural frequency for the molten metal in the ladle Z, and the calculated weight of the molten metal in the ladle Z from the first weight-calculating means; a second natural frequency calculating means for calculating the natural frequency (the second natural frequency) of the molten metal in the mold Y based on a predetermined relationship between the weight and the natural frequency for the molten metal in the mold Y, and the calculated weight of the molten metal in the mold Y from the second weight-calculating means; an instructing means for providing operating instructions to the electrical pusher-cylinder B, the electrical cushion-cylinder C, and the automatic pouring device D, based on the control program; and a filtering means for modifying a velocity waveform of a conveying motion of the flask to be targeted such that the casting line is operated by the modified velocity waveform that does not include the calculated natural frequencies of the molten metal in the ladle or in the mold from the first and second weight-calculating means.

The first servo controller B3 may comprise a central processing unit (CPU) B3a, a pulse output device B3b, I/O B3c, a communication device B3d, a servo I/O B3e, and a counter B3f. The second servo controller C3 may, like the first servo controller B3, comprise a central processing unit (CPU) C3a, a pulse output device C3b, I/O C3c, a communication device C3d, a servo I/O C3e, and a counter C3f.

The first servo controller B3 and the second servo controller C3 are connected to a communication device K2 of the control device K of the conveying line through communication devices B3d and C3d, which transmit and receive digital data, to acquire data on the weights of the molten metal in the control unit K for the conveying line.

The control unit J of the automatic pouring device is electrically connected to the control device K of the conveying line such that the control unit J transmits signals indicating the weights of the molten metal in the ladle Z and mold Y to the control device K through the link communication devices J3 and K3. The control unit J also includes a programmable logic controller (PLC) J4 to control the X driving motor of the automatic pouring device D.

The first and the second servo controller B3 and C3 transmit a positional command (a signal) of a pulse string to the inverters B2 and C2 to drive the induction motors B1 and C1. Controlling the torques, speeds, and positions of these motors, is carried out by the inverters B2 and C2.

Attached to the automatic pouring device D is a load cell G to measure the weight of the molten metal in the ladle Z. The load cell G is electrically connected to an analog input unit J1 of the control unit J of the automatic pouring device through an amplifier H.

The function of the casting equipment constructed as described above will now be explained. The weight of the molten metal in the ladle Z is detected by the load cell G, and to measure it, it is then input into the analog input unit J1 of the control unit J of the automatic pouring device. The molten metal in the ladle Z of the automatic pouring device D is then poured into the mold Y. The measured weight of the molten metal in the ladle Z and the reduced weight of the molten metal in the mold Y that is calculated from the former are then provided in the control device K of the conveying line, to retrieve the natural frequency (the first natural frequency) of the molten metal in the ladle Z and the natural frequency (the second natural frequency) of the molten metal in the mold Y.

The electric cushion-cylinder C is positioned at a predetermined set position in readiness. When the first and the second servo controllers B3 and C3 detect a signal indicating that the flask to be conveyed from the programmable logic controller (PLC) K4 of the control device K of the conveying line, the electric pusher-cylinder B is first extended at a low speed to secure the group of the flasks on the conveying line entirely in the sandwiched relation between the electric pusher-cylinder B and the electrical cushion-cylinder C. Then the electric pusher-cylinder B is extended, while the electric cushion-cylinder C is contracted in the same velocity waveform of the electric pusher-cylinder B, to convey the flasks such that the group of the flasks moves in the X direction by a distance corresponding to one flask. At the same time, the automatic pouring device D pours the molten metal into the mold Y, while the automatic pouring device D is moved in the X direction by the distance corresponding to one flask. In such a rapid motion, a sloshing suppression control is carried out to prevent the molten metal in the ladle Z and the mold Y from the sloshing, as described below.

Both the calculated natural frequency of the molten metal in the ladle Z and the calculated natural frequency of the molten metal in the mold Y are input into the filtering means to modify the velocity waveform of the conveying motion of the flasks on the conveying line, to provide a version of it that is modified without including these two natural frequencies. Both the electric pusher-cylinder B and the electrical cushion-cylinder C are then driven such that the velocity waveform of the conveying motion of the flasks is in the modified version. Thus, the sloshing that occurs in the molten metal in the ladle Z and the mold Y can be accurately suppressed when the ladle Z and the flasks are moved by a distance corresponding to one flask.

The control unit J of the automatic pouring device D causes the second servo controller C3 to transmit the signals indicating that the flasks are conveyed while the automatic pouring device D pours the molten metal. The transmitted signal is input into the counter J2 to be converted to positional data. The X driving motor of the automatic pouring device D is then driven to follow the positional command based on the converted positional data to move the automatic pouring device D in the X direction such that it follows the conveyed motion of the flasks.

Because the molten metal in the ladle Z and the mold Y has a complicated shape and thus it is difficult to accurately calculate the respective natural frequencies, a relationship between the weights of the molten metal in the ladle Z and natural frequencies that are derived based on a method to estimate the natural frequencies, described below, is preliminarily established as parameters. The method for determining the natural frequencies includes, for example, a derivation based on fluid analysis software, or an estimation based on the magnitude of the amplitude of the vibrations when the molten metal is actually vibrated. This derivation is made while the frequencies are varied. One example that may be used as the fluid analysis software is three-dimensional thermo-fluid analysis software that can calculate with a high accuracy a complicated and unstable behavior of fluid that involves nonlinear behavior or a large deformation behavior.

Although, as described above, the inverter control of the servo controllers in this embodiment is based on the positional control by the output of the pulse string, such a control may be carried out at the side of the servo controllers by configuring control loops for velocities and positions. The induction motors B1, C1 and the inverters B2, C2 may be replaced by servomotors and servo amplifiers.

The Second Embodiment

The same as the first embodiment, the control system in the second embodiment includes the first servo controller B3, the second servo controller C3, the control unit J of the automatic pouring device D, and the control device K of the conveying line, as described above. The control system in the second embodiment also includes an arrangement for controlling the suppression of sloshing. This arrangement includes, the same as with the first embodiment, a first weight-calculating means for calculating the weight of the molten metal in the ladle Z; a second weight calculating means for calculating a weight of molten metal in the mold Y; a first natural frequency-calculation means for calculating the natural frequency (the first natural frequency) of the molten metal in the ladle Z based on a predetermined relationship between the weight and the natural frequency for the molten metal in the ladle Z, and the calculated weight of the molten metal in the ladle Z from the first weight-calculating means; a second natural frequency-calculation means for calculating the natural frequency (the second natural frequency) of the molten metal in the mold Y based on a predetermined relationship between the weight and the natural frequency for the molten metal in the mold Y, and the calculated weight of the molten metal in the mold Y from the second weight-calculating means. However, the arrangement for controlling the suppression of sloshing in the second embodiment, instead of being that of the instructing means and the filtering means of the first embodiment, includes the following instructing means, parameter calculation means for calculating parameters, storing means for storing parameters, restricting means for restricting the maximal value, and filtering means. In this embodiment, the instructing means provides operating instructions based on a forward control program for the operation of the casting line. The means to calculate parameters preliminarily calculates the parameters of the controllers (i.e., the first servo controller B3, the second servo controller C3, and the control unit J of the automatic pouring device D) of the driving devices for the X direction (i.e., the induction motor B1 of the electric pusher-cylinder B, the induction motor C1 of the electric cushion-cylinder C, and the X driving motor of the automatic pouring device D) of the casting line such that the calculated parameters do not exceed the capacities of these driving devices for the X direction. The storing means receives the parameters from the calculating means and stores them. In line with the stored parameters given by the storing means, the restricting means limits the maximum value in at least one of a velocity of the movement, an acceleration of the movement, and a jerk of the movement of the automatic pouring device and the flasks in the operating instructions for the casting line from the instructing means. In line with the stored parameters given by the storing means, the filtering means receives data on the first and second resonance frequencies from the first and second resonance frequency-calculation means, and thus removes components located near them from the operating instructions in which the maximum value is restricted by the restricting means.

Removing the components located near the first and second resonance frequencies is carried out using filtering parameters that are preliminarily stored by simulating a model representing the characteristics of the casting line to repeatedly calculate the components by the following equation (1) or (2), while gradually varying the filtering parameters ai(f), bj(f). Further, the instructing means provides the operating instructions in which the components located near the first and second resonance frequencies are removed, by the filtering mean, to the driving devices for the X direction through these controllers. These controllers drive the driving devices for the X direction based on just the feedforward control program, without the feedback program. The construction for carrying out the control of suppression of sloshing can be implemented by a computer.

$\begin{array}{cc}\left[\mathrm{Math}.3\right]& \\ y\left(t\right)=b_0\left(f\right)x\left(t\right)+b_1\left(f\right)x\left(t-1\right)+b_2\left(f\right)x\left(t-2\right)+\dots -a_1\left(f\right)y\left(t-1\right)-a_2\left(f\right)y\left(t-2\right)-\dots y\left(t\right)=\sum _{j=0}^mb_j\left(f\right)x\left(t-j\right)-\sum _{i=1}^na_1\left(f\right)y\left(t-i\right)& \left(1\right)\end{array}$

where ai(f), bj(f) are filtering parameters that are parameterized from resonance frequencies f sequentially calculated from the molten metal in the ladle and the mold, x(t-j) is time-series data that is input before j controlling cycles, and y (t-i) denotes time-series data that are output before i controlling cycles.

$\begin{array}{cc}\left[\mathrm{Math}.4\right]& \\ \begin{array}{c}F\left(S\right)=\frac{Y\left(S\right)}{X\left(S\right)}\\ =\frac{b_0\left(f\right)S^0+b_1\left(f\right)S^1+b_2\left(f\right)S^2+\dots }{a_0\left(f\right)S^0+a_1\left(f\right)S^1+a_2\left(f\right)S^2+\dots }\\ =\frac{\sum _{j=0}^mb_j\left(f\right)S^j}{\sum _{i=0}^na_i\left(f\right)S^i}\end{array}& \left(2\right)\end{array}$

where equation (1) can be derived by applying a Z transformation to the transfer function of the filter that is expressed as equation (2), and S is the Laplace operator.

In the second embodiment, the weight of the molten metal in the ladle is entered in the first resonance frequency-calculation means to calculate the resonance frequency of the molten metal in the ladle, while the weight of the molten metal in the mold is entered in the second resonance frequency-calculation means to calculate the resonance frequency of the molten metal in the mold. These two calculated resonance frequencies are entered in the filter.

Meanwhile, the instructing means provides the operating instructions to the restricting means. The restricting means then reads out the stored parameters on the controllers of the driving devices for the X direction in the casting line from the parameter storing means, while the restricting means limits the maximum value in at least one of the velocity of the movement, the acceleration of the movement, and the jerk of the movement of the automatic pouring device and the flasks in the operating instructions from the instructing means such that the calculated parameters do not exceed the capacities of these driving devices for the X direction. The results are provided to the filter.

The filtering means reads out the stored parameters on the controllers of the driving devices for the X direction in the casting line that do not exceed the capacities of these driving devices from the parameter storing means. The filtering means filters the operating instructions to be provided to the driving devices in the X direction in which the maximum value is restricted in at least one of the velocity of the movement, the moving acceleration, and the moving jerk of the automatic pouring device and the flasks in line with the two resonance frequencies sequentially calculated from the molten metal in the ladle and the mold, to remove from the operating instructions the components located near the first and second resonance frequencies. The resulting filtering operating instructions are entered in the driving devices for the X direction in the casting line through their controllers. Thus, any sloshing that has occurred in the molten metal in the ladle Z and the mold Y can be suppressed when the ladle Z and the flasks are moved by a distance corresponding to one flask.

The calculation by the filtering means is executed based on the principle as discussed below. Namely, assuming that x (t) is time-series data to be input in the filtering means, and y (t) is time-series data output from the filtering means, a filter to be applied to the time-series data is expressed by equation (1).

$\begin{array}{cc}\left[\mathrm{Math}.5\right]& \\ y\left(t\right)=b_0\left(f\right)x\left(t\right)+b_1\left(f\right)x\left(t-1\right)+b_2\left(f\right)x\left(t-2\right)+\dots -a_1\left(f\right)y\left(t-1\right)-a_2\left(f\right)y\left(t-2\right)-\dots y\left(t\right)=\sum _{j=0}^mb_j\left(f\right)x\left(t-j\right)-\sum _{i=1}^na_1\left(f\right)y\left(t-i\right)& \left(1\right)\end{array}$

where, ai(f), bj(f) are parameters that are parameterized from two resonance frequencies f sequentially calculated from the molten metal in the ladle Z and the mold Y.

Further, x(t-j) is time-series data that are input before j controlling cycles, and y (t-i) is time-series data that are output before i controlling cycles.

Although the number of items m and n can be appropriately determined based on the construction of the filter, they should be preliminary decided. For example, m=0 and n=1 if the filter is a primary low-path filter, m=0 and n=1 if it is a secondary low-path filter, and m=2 and n=2 if it is a notch filter, can be preliminarily decided. These decided numbers of items m and n are entered in the parameter storing means and the parameter calculation means.

The parameters ai(f), bj(f) should be preliminary calculated and decided using the parameter calculation means by simulations using a model representing the characteristics of the casting line to repeatedly calculate them, while their values are being gradually varied.

To calculate these parameters, the constraining conditions in the operating instructions to be provided to the driving devices for the X direction in the casting line are as follows: the maximum velocity in the operating instructions should not exceed the maximum velocities of the electrical pusher-cylinder B and the electrical cushion-cylinder C, each maximum value of the maximum velocities of them should not exceed the restrictions on the maximum value on the driving devices for the X direction, and the time of the movements of the ladle Z and the flasks becomes the shortest.

Equation (1) can be derived by applying a Z transformation to the transfer function of the filter that is expressed as the following equation (2).

$\begin{array}{cc}\left[\mathrm{Math}.6\right]& \\ \begin{array}{c}F\left(S\right)=\frac{Y\left(S\right)}{X\left(S\right)}\\ =\frac{b_0\left(f\right)S^0+b_1\left(f\right)S^1+b_2\left(f\right)S^2+\dots }{a_0\left(f\right)S^0+a_1\left(f\right)S^1+a_2\left(f\right)S^2+\dots }\\ =\frac{\sum _{j=0}^mb_j\left(f\right)S^j}{\sum _{i=0}^na_i\left(f\right)S^i}\end{array}& \left(2\right)\end{array}$

where S is the Laplace operator.

In the second embodiment, the induction motors B1, C1 and the inverters B2, C2 of the electric pusher-cylinder B and the electric cushion-cylinder C may also be replaced by servomotors and servo amplifiers.

The computer to use for the embodiments of the present invention may include a central processing unit (CPU), an input device, a display, a memory, and any other circuit that is able to perform the functions described herein.

The computer also may include a storage device that may include a hard disk drive, an optical disk drive, a floppy disk drive, etc. The storage device may use other similar means to load a computer program or other instructions to the computer.

The computer program, when loaded and executed, controls the computer such that it carries out the methods described herein. A computer readable storage media that stores the computer program may include any volatile or non-volatile storage device.

Because the above embodiments are not intended to limit the present invention to any specific embodiment, it will be appreciated that various modifications and variations may be embodied without departing from the spirit and the scope of the present invention.

Claims

1. A method of suppressing sloshing in a casting line, wherein said casting line includes:

a conveying line in which an electric pusher-cylinder is located at one end of the conveying line for intermittently pushing out a plurality of flasks, wherein each flask contains a mold, one by one, and an electric cushion-cylinder is located at the other end of said conveying line and opposed to said electric pusher-cylinder to receive and cushion a group of said pushed flasks such that said conveying line that conveys said plurality of flasks is arranged linearly between said electric pusher-cylinder and said electric cushion-cylinder; and

an automatic pouring device that has a ladle for containing molten metal and that can be moved in synchronization with the flask on the conveying line, to pour the molten metal into the mold by tilting said ladle;

said method controlling said electric pusher-cylinder and said electric cushion-cylinder by using a controller having filtering means such that the sloshing that occurs in the molten metal is suppressed when said ladle and said mold move by a distance corresponding to one flask, said method comprising:

calculating a first natural frequency of the molten metal in said ladle based on a predetermined relationship between the weight and the natural frequency for the molten metal in said ladle, and the measured weight of the molten metal in said ladle, and calculating a second natural frequency of the molten metal in said mold based on a predetermined relationship between the weight and the natural frequency for the molten metal in said mold, and the measured weight of the molten metal in said mold;

entering the first and second natural frequencies in said filtering means to modify a velocity waveform of the movement of conveying said flasks such that the modified velocity waveform does not include the first and second natural frequencies;

driving said electric pusher-cylinder and said electric cushion-cylinder such that the velocity waveform of the movement of conveying said flasks is said modified velocity waveform.

2. A system of suppressing sloshing in a casting line, wherein said casting line includes:

a conveying line in which an electric pusher-cylinder is located at one end of the conveying line for intermittently pushing out a plurality of flasks, wherein each contains a mold, one by one, and an electric cushion-cylinder is located at the other end of said conveying line and is opposed to said electric pusher-cylinder to receive and cushion a group of said pushed flasks such that said conveying line that conveys said plurality of flasks is arranged linearly between said electric pusher-cylinder and said electric cushion-cylinder; and

an automatic pouring device that has a ladle for containing molten metal and that can be moved in synchronization with the flask on the conveying line, to pour the molten metal into the mold by tilting said ladle; wherein said system that controls said casting line such that the sloshing that occurs in the molten metal in said ladle and said mold is suppressed when said ladle and said mold move by a distance corresponding to one flask; said system comprising:

a first weight-calculation means for calculating the weight of the molten metal in said ladle;

a second weight-calculation means for calculating a second natural frequency of the molten metal in said mold;

a first natural frequency-calculation means for calculating a first natural frequency based on a predetermined relationship between the weight and the natural frequency for the molten metal in said ladle, and the calculated weight of the molten metal in said ladle by said first weight-calculation means;

a second natural frequency-calculation means for calculating a second natural frequency based on a predetermined relationship between the weight and the natural frequency for the molten metal in said mold, and the calculated weight of the molten metal in said mold by said second weight-calculation means;

filtering means for modifying a velocity waveform of the movement of conveying of said flasks on said conveying line such that the modified velocity waveform does not include the first and second natural frequencies calculated by said first and second natural frequency-calculation means; and

instructing means for providing operating instructions to said electric pusher-cylinder, said electric cushion-cylinder, and said automatic pouring device, based on said modified velocity waveform.

3. A method of suppressing sloshing in a casting line, wherein said casting line includes: y  ( t ) = b 0  ( f )  x  ( t ) + b 1  ( f )  x  ( t - 1 ) + b 2  ( f )  x  ( t - 2 ) + … - a 1  ( f )  y  ( t - 1 ) - a 2  ( f )  y  ( t - 2 ) - …   y  ( t ) = ∑ j = 0 m   b j  ( f )  x  ( t - j ) - ∑ i = 1 n   a 1  ( f )  y  ( t - i ) ( 1 ) F  ( S ) = Y  ( S ) X  ( S ) = b 0  ( f )  S 0 + b 1  ( f )  S 1 + b 2  ( f )  S 2 + … a 0  ( f )  S 0 + a 1  ( f )  S 1 + a 2  ( f )  S 2 + … = ∑ j = 0 m   b j  ( f )  S j ∑ i = 0 n   a i  ( f )  S i ( 2 )

a conveying line in which an electric pusher-cylinder is located at one end of the conveying line for intermittently pushing out a plurality of flasks, wherein each flask contains a mold, one by one, and an electric cushion-cylinder is located at the other end of said conveying line and is opposed to said electric pusher-cylinder to receive and cushion a group of said pushed flasks such that said conveying line conveys said plurality of flasks and is arranged linearly between said electric pusher-cylinder and said electric cushion-cylinder;

an automatic pouring device that has a ladle for containing molten metal and that can be moved in synchronization with the flask on the conveying line, to pour the molten metal into the mold by tilting said ladle;

driving means for driving said electric pusher-cylinder, said electric cushion-cylinder, and said automatic pouring device along a conveyed direction of said flasks;

controlling means for controlling said driving means; and instructing means for providing operating instructions for said electric pusher-cylinder, said electric cushion-cylinder, and said automatic pouring device to said driving means through said controlling means wherein;

said method controls said casting line using a controller having filtering means, based on a feedforward control program such that the sloshing that occurs in the molten metal is suppressed when said ladle and said mold move by a distance corresponding to one flask, said method comprising:

calculating a first natural frequency of the molten metal in said ladle based on a predetermined relationship between the weight and the natural frequency for the molten metal in said ladle, and the measured weight of the molten metal in said ladle, and calculating a second natural frequency of the molten metal in said mold based on a predetermined relationship between the weight and the natural frequency for the molten metal in said mold, and the measured weight of the molten metal in said mold;

under the first natural frequency, the second natural frequency, and the parameters of said controlling means that are preliminarily calculated such that they do not exceed the capacities of said driving means and are stored, removing components that are located near the first and second frequencies from the operating instructions, in which the maximum value of at least one of a velocity of the movement, an acceleration of the movement, and a jerk of the movement of said ladle and said mold is restricted, by said filtering means using said stored parameters,

wherein said components to be removed are decided based on a simulation using a model representing the characteristics of said casting line to repeatedly calculate said component by the following equation (1) or (2),

while gradually varying filtering parameters ai(f), bj(f) that are parameterized by a resonance frequency f that are successively calculated from the molten metal in said ladle and said mold, wherein y (t-i) is time-series data that are output before i controlling cycles, x(t-j) is time-series data that are input before j controlling cycles, S is the Laplace operator, and equation (1) can be derived by applying a Z transformation to the transfer function of the filter that is expressed as equation (2); and

entering the operating instructions, in which said components that are located near the first and second frequencies have been removed, in said controlling means based on only said feedforward controlling program, to operate said driving means based on only said feedforward controlling program without using a feedback control program.

4. A system for the suppression of sloshing in a casting line, wherein said casting line includes: y  ( t ) = b 0  ( f )  x  ( t ) + b 1  ( f )  x  ( t - 1 ) + b 2  ( f )  x  ( t - 2 ) + … - a 1  ( f )  y  ( t - 1 ) - a 2  ( f )  y  ( t - 2 ) - …   y  ( t ) = ∑ j = 0 m   b j  ( f )  x  ( t - j ) - ∑ i = 1 n   a 1  ( f )  y  ( t - i ) ( 1 ) F  ( S ) = Y  ( S ) X  ( S ) = b 0  ( f )  S 0 + b 1  ( f )  S 1 + b 2  ( f )  S 2 + … a 0  ( f )  S 0 + a 1  ( f )  S 1 + a 2  ( f )  S 2 + … = ∑ j = 0 m   b j  ( f )  S j ∑ i = 0 n   a i  ( f )  S i ( 2 )

a conveying line in which an electric pusher-cylinder is located at one end of the conveying line for intermittently pushing out a plurality of flasks that each contain a mold, one by one, and an electric cushion-cylinder is located at the other end of said conveying line and is opposed to said electric pusher-cylinder to receive and cushion a group of said pushed flasks such that said conveying line conveys said plurality of flasks and is arranged linearly between said electric pusher-cylinder and said electric cushion-cylinder;

an automatic pouring device that has a ladle for containing molten metal and that can be moved in synchronization with the flask on the conveying line, to pour the molten metal into the mold by tilting said ladle;

driving means for driving said electric pusher-cylinder, said electric cushion-cylinder, and said automatic pouring device along a conveyed direction of said flasks; and

controlling means for controlling said driving means; wherein said system controls said casting line to suppress the sloshing that occurs in the molten metal in said ladle and the mold when said ladle and said mold move by a distance corresponding to one flask, said system comprising:

a first weight-calculation means for calculating the weight of the molten metal in said ladle;

a second weight-calculation means for calculating a second natural frequency of the molten metal in said mold;

a first natural frequency-calculation means for calculating a first natural frequency based on a predetermined relationship between the weight and the natural frequency for the molten metal in said ladle, and the calculated weight of the molten metal in said ladle by said first weight-calculation means;

a second natural frequency-calculation means for calculating a second natural frequency based on a predetermined relationship between the weight and the natural frequency for the molten metal in said mold, and the calculated weight of the molten metal in said mold by said second weight-calculation means;

instructing means for providing operating instructions based on a feedforward program for operations of said electric pusher-cylinder, said electric cushion-cylinder, and said automatic pouring device, to said driving means through said controlling means;

parameter calculation means for preliminarily calculating the parameters of said controlling means such that the calculated parameters do not exceed the capacity of said driving means;

storing means for receiving and storing the calculated parameters from said parameter calculation means;

restriction means for restricting a maximum value of at least one of a velocity of the movement, an acceleration of the movement, and a jerk of the movement of said automatic pouring device and said mold;

filtering means for receiving the first and second resonance frequencies from said first and second frequency-calculation means, and for removing components that are located near the first and second frequencies from the operating instructions, in which the maximum value is restricted by said restriction means, using the stored parameters from the stored means, wherein said components to be removed are decided based on a simulation using a model representing the characteristics of said casting line to repeatedly calculate said component, under said stored parameters, by the following equation (1) or (2),

while gradually varying filtering parameters ai(f), bj(f) that are parameterized by a resonance frequency f that are successively calculated from the molten metal in said ladle and said mold, wherein y (t-i) is time-series data that are output before i controlling cycles, x(t-j) is time-series data that are input before j controlling cycles, S is the Laplace operator, and equation (1) can be derived by applying a 2 transformation to the transfer function of the filter that is expressed as equation (2); and

wherein said instructing means provides said controlling means with operating instructions in which said components that are located near the first and second frequencies have been removed such that said controlling means carries out the controls based on only said feedforward controlling program without using a feedback control program.

5. A computer readable media storing a computer program for the suppression of sloshing in a casting line, wherein said casting line includes:

a conveying line in which an electric pusher-cylinder is located at one end of the conveying line for intermittently pushing out a plurality of flasks that each contain a mold, one by one, and an electric cushion-cylinder is located at the other end of said conveying line and is opposed to said electric pusher-cylinder to receive and cushion a group of said pushed flasks such that said conveying line conveys said plurality of flasks and is arranged linearly between said electric pusher-cylinder and said electric cushion-cylinder; and

an automatic pouring device that has a ladle for containing molten metal and that can be moved in synchronization with the flask on the conveying line, to pour the molten metal into the mold by tilting said ladle;

wherein said computer program causes a computer having filter means to control said electric pusher-cylinder and said electric cushion-cylinder such that the sloshing that occurs in the molten metal is suppressed when said ladle and said mold move by a distance corresponding to one flask, said computer program comprising the steps to be executed by said computer of:

calculating a first natural frequency of the molten metal in said ladle based on a predetermined relationship between the weight and the natural frequency for the molten metal in said ladle, and the measured weight of the molten metal in said ladle, and calculating a second natural frequency of the molten metal in said mold based on a predetermined relationship between the weight and the natural frequency for the molten metal in said mold, and the measured weight of the molten metal in said mold;

entering the first and second natural frequencies in said filtering means to modify a velocity waveform of the movement of conveying of said flasks such that the modified velocity waveform does not include the first and second natural frequencies; and

driving said electric pusher-cylinder and said electric cushion-cylinder such that the velocity waveform of the movement of conveying of said flasks is said modified velocity waveform.

6. A computer readable media storing a computer program for the suppression of sloshing in a casting line, wherein said casting line includes: y  ( t ) = b 0  ( f )  x  ( t ) + b 1  ( f )  x  ( t - 1 ) + b 2  ( f )  x  ( t - 2 ) + … - a 1  ( f )  y  ( t - 1 ) - a 2  ( f )  y  ( t - 2 ) - …   y  ( t ) = ∑ j = 0 m   b j  ( f )  x  ( t - j ) - ∑ i = 1 n   a 1  ( f )  y  ( t - i ) ( 1 ) F  ( S ) = Y  ( S ) X  ( S ) = b 0  ( f )  S 0 + b 1  ( f )  S 1 + b 2  ( f )  S 2 + … a 0  ( f )  S 0 + a 1  ( f )  S 1 + a 2  ( f )  S 2 + … = ∑ j = 0 m   b j  ( f )  S j ∑ i = 0 n   a i  ( f )  S i ( 2 )

a conveying line in which an electric pusher-cylinder is located at one end of the conveying line for intermittently pushing out a plurality of flasks that each contain a mold, one by one, and an electric cushion-cylinder is located at the other end of said conveying line and is opposed to said electric pusher-cylinder to receive and cushion a group of said pushed flasks such that said conveying line that conveys said plurality of flasks is arranged linearly between said electric pusher-cylinder and said electric cushion-cylinder;

an automatic pouring device that has a ladle for containing molten metal and that can be moved in synchronization with the flask on the conveying line, to pour the molten metal into the mold by tilting said ladle;

driving means for driving said electric pusher-cylinder, said electric cushion-cylinder, and said automatic pouring device along a conveyed direction of said flasks;

controlling means for controlling said driving means; and

instructing means for providing operating instructions for said electric pusher-cylinder, said electric cushion-cylinder, and said automatic pouring device to said driving means through said controlling means;

wherein said computer program causes a computer having filter means to control said electric pusher-cylinder and said electric cushion-cylinder such that the sloshing that occurs in the molten metal is suppressed when said ladle and said mold move by a distance corresponding to one flask, said computer program comprising the steps to be executed by said computer of:

calculating a first natural frequency of the molten metal in said ladle based on a predetermined relationship between the weight and the natural frequency for the molten metal in said ladle, and the measured weight of the molten metal in said ladle, and calculating a second natural frequency of the molten metal in said mold based on a predetermined relationship between the weight and the natural frequency for the molten metal in said mold, and the measured weight of the molten metal in said mold;

under the first natural frequency, the second natural frequency, and parameters of said controlling means that are preliminarily calculated such that they do not exceed capacities of said driving means and are stored, removing components that are located near the first and second frequencies from the operating instructions, in which at least one of a velocity of the movement, an acceleration of the movement, and a jerk of the movement of said ladle and said mold, by said filtering means using said stored parameters, wherein said components to be removed are decided based on a simulation using a model representing characteristics of said casting line to repeatedly calculate said components by the following equation (1) or (2),

while gradually varying filtering parameters ai(f), bj(f) that are parameterized by a resonance frequency f that are successively calculated from the molten metal in said ladle and said mold, wherein y (t-i) is time-series data that are output before i controlling cycles, x(t-j) is time-series data that are input before j controlling cycles, S is the Laplace operator, and equation (1) can be derived by applying a Z transformation to the transfer function of the filter that is expressed as equation (2); and

entering the operating instructions, in which said components located near the first and second frequencies have been removed, in said controlling means based on only said feedforward controlling program, to operate said driving means based on only said feedforward controlling program without using a feedback control program.