WO2012060018A1 - 電動射出成形機の可塑化制御装置および可塑化制御方法 - Google Patents
電動射出成形機の可塑化制御装置および可塑化制御方法 Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C2045/1784—Component parts, details or accessories not otherwise provided for; Auxiliary operations not otherwise provided for
- B29C2045/1792—Machine parts driven by an electric motor, e.g. electric servomotor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76003—Measured parameter
- B29C2945/76083—Position
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76003—Measured parameter
- B29C2945/7611—Velocity
- B29C2945/76113—Velocity linear movement
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76177—Location of measurement
- B29C2945/7618—Injection unit
- B29C2945/76187—Injection unit screw
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76344—Phase or stage of measurement
- B29C2945/76367—Metering
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76494—Controlled parameter
- B29C2945/76525—Electric current or voltage
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76494—Controlled parameter
- B29C2945/76595—Velocity
- B29C2945/76605—Velocity rotational movement
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76655—Location of control
- B29C2945/76658—Injection unit
- B29C2945/76692—Injection unit drive means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76822—Phase or stage of control
- B29C2945/76846—Metering
Definitions
- the present invention relates to a plasticization control device and a plasticization control method for an electric injection molding machine.
- the AC servo motor which features high-precision control and excellent responsiveness, has a large capacity by improving the performance of permanent magnets used in the motor and reducing costs.
- An AC servo drive using an AC servo motor is also applied to an injection molding machine (clamping force 350 t or more).
- the injection molding machine has a plasticizing mechanism that melts resin pellets by screw rotation, an injection and pressure holding mechanism that injects molten resin into a mold at a high speed by the forward movement of the screw, and a mold that opens and closes the mold. There is an opening and closing mechanism.
- the AC servo drive can be applied to any of these mechanisms.
- FIG. 1 a schematic diagram of the plasticizing mechanism is shown in FIG.
- the injection molding machine is provided with a moving device base (not shown) that can be moved by a linear guide on an injection molding machine base (not shown) fixed on the ground. All parts other than the mold 1 shown in FIG. By moving this moving device base, the tip of the injection cylinder 2 can be pressed against the mold 1, and conversely, the tip of the injection cylinder 2 can be separated from the mold 1.
- FIG. 2 shows a state during a plasticizing process in which resin pellets are melted by screw rotation.
- An injection cylinder 2, an injection servo motor 3, a speed reducer 4, a ball screw 5, a bearing 6 and a hopper 16 are fixed on the moving device base. Further, the nut 7, the movable part 8, the screw 9, the speed reducer 10, the plasticizing servo motor 11 and the pressure sensor 12 of the ball screw 5 are integrated. In this integrated structure, the movable portion 8 is mounted on the linear guide 13 so that the ball screw 5 can be moved back and forth by the movement of the nut 7 of the ball screw 5.
- the rotational motion of the injection servo motor 3 is transmitted to the ball screw 5 as a booster mechanism via the speed reducer 4, and the rotational motion of the ball screw 5 is converted into a linear motion of the nut 7 on the ball screw shaft.
- the screw 9 is moved back and forth and the molten resin is pressurized by the screw 9 through the movable portion 8.
- the pressure applied to the molten resin by the screw 9 in the plasticizing process is referred to as a screw back pressure.
- the position of the screw 9 is detected by a motor encoder 14 provided on the injection servo motor shaft.
- the screw back pressure is detected by the pressure sensor (for example, load cell) 12 that is sandwiched and installed between the nut 7 of the ball screw 5 and the movable portion 8.
- the rotation of the screw 9 for melting and kneading the resin pellets in the plasticizing process is performed by the plasticizing servo motor 11 via the speed reducer 10, and the plasticizing servo motor 11 includes a motor.
- An encoder 15 is attached.
- the screw 9 advances at a high speed by the high-speed rotation of the injection servo motor 3, the molten resin stored at the tip of the screw 9 is filled into the cavity 17 in the mold 1 at a high speed, and pressure is applied for a predetermined time.
- the injection process is finished, and a molded product having a predetermined shape is obtained.
- Patent Document 1 a plasticizing motor gives a predetermined screw rotation speed, and a screw back pressure set value is realized by screw retraction speed control by an injection motor.
- the injection motor realizes a constant or predetermined screw retraction speed pattern, and the screw back pressure setting value is realized by controlling the rotational speed of the plasticizing motor.
- the screw back pressure setting value is realized by current (torque) control or current (torque) limitation of the injection motor.
- Patent Literature 7 and Patent Literature 8 the amount of screw movement required to realize the screw back pressure setting value is performed by position control using an injection motor.
- Patent Document 9 and Patent Document 10 the plasticizing motor achieves a predetermined screw rotation speed, and the injection motor realizes the screw retraction speed corrected by the deviation amount of the screw back pressure to perform screw back pressure control. Do.
- Patent Document 11 from the first control mode in which the plasticizing motor is screw rotation speed control and the injection motor is screw back pressure control, the plasticizing motor is screw back pressure control and the injection motor is screw retraction control. Control to switch to the second mode is performed.
- screw back pressure control is an indispensable technical problem in the plasticizing process, and a pressure sensor is required to realize accurate screw back pressure control.
- Patent Document 12 a plasticizing pressure sensor (0 to 150 atmospheres (15.2 MPa)) having a small pressure detection value range and an injection / holding pressure sensor (150 to 3000 atmospheres (15) having a large pressure detection value range are disclosed. .2 to 304 MPa)), which switches between two types of pressure sensors. By using two types of pressure sensors with different detection ranges, the control accuracy of the screw back pressure in the plasticizing process is improved.
- FIG. 3 is a block diagram for explaining an example of the internal configuration of a conventional plasticization control apparatus.
- the plasticizing control device includes a back pressure controller 20, an injection motor controller (servo amplifier) 30, a screw rotation speed controller 40, a plasticizing motor controller 50 (servo amplifier), and a pressure sensor 12. .
- the back pressure controller 20 will be described.
- the back pressure controller 20 performs a control calculation at regular time intervals and updates a control command.
- the back pressure controller 20 includes a screw back pressure commander 21, a subtractor 22, an analog / digital (A / D) converter 23, a pressure controller 24, and a digital / analog (D / A) converter 25.
- the pressure sensor 12 is connected to the A / D converter 23.
- the screw back pressure command device 21 outputs a screw back pressure command P * b according to a time sequence to the subtractor 22.
- the pressure controller 24 outputs a current command i * m to the injection servomotor 3 to the D / A converter 25 by proportional integral derivative (PID) control calculation.
- PID proportional integral derivative
- the D / A converter 25 outputs a motor current command i * m to the injection motor controller 30.
- the injection motor controller 30 includes an A / D converter 31 and a pulse width modulation control (PWM) circuit 32.
- the injection servo motor 3 is connected to the injection motor controller 30, and the motor encoder 14 is attached to the injection servo motor 3.
- the A / D converter 31 outputs the motor current command i * m from the D / A converter 25 to the PWM circuit 32.
- the PWM circuit 32 applies a predetermined three-phase voltage to the injection servomotor 3 based on a given motor current command i * m .
- the injection servo motor 3 is driven by the motor current i * m , and applies a pressing force by the screw to the molten resin stored at the screw tip so as to realize the screw back pressure P * b .
- the screw rotation speed controller 40 includes a screw rotation speed command device 41.
- the screw rotation speed command device 41 outputs a screw rotation speed command N * s according to a time sequence to the plasticizing motor controller 50.
- the plasticizing motor controller 50 includes a subtractor 51, a differentiation circuit 52, a speed controller 53, and a PWM circuit 54.
- the plasticizing servo motor 11 is connected to the plasticizing motor controller 50, and the motor encoder 15 is attached to the plasticizing servo motor 11.
- the screw rotation speed command N * s from the screw rotation speed controller 40 is input to the subtractor 51.
- the pulse signal of the motor encoder 15 is input to the differentiating circuit 52, and the differentiating circuit 52 outputs the actual screw speed N s to the subtractor 51.
- the speed controller 53 outputs a current command i * for the plasticizing servomotor 11 to the PWM circuit 54 by PID control calculation.
- the PWM circuit 54 applies a predetermined three-phase voltage to the plasticizing servomotor 11 based on a given motor current command i * .
- the plasticizing servomotor 11 is driven by the motor current i * to achieve a predetermined screw rotation speed N * s .
- Screw back pressure control is an effective means for ensuring the uniformity of the molten resin in the plasticizing process and improving the measurement accuracy.
- a screw back pressure detecting means that satisfies the following two requirements is required.
- A High accuracy
- B The technique of a high gain observer (Non-Patent Document 1) is adopted as a pressure detection means that satisfies these two requirements with a very small time delay.
- a simple controlled object model will be used to explain that a high gain observer that inputs variables that can be measured and estimates all state variables satisfies the two requirements (A) and (B). Equation (1) shows the state equation and output equation of the controlled object model.
- x 1 and x 2 are state variables
- u is an input variable
- y is an output variable
- ⁇ (x, u) is a nonlinear function composed of variables x and u.
- the state equation is composed of first-order differential equations that express the behavior of the state variables x 1 and x 2 , and the output equation defines an observable variable, that is, an output variable y.
- x 1 is the position variable
- x 2 is the speed variables
- u is the motor current.
- x ⁇ 1, x ⁇ 2 represents the predicted value of the state variable x 1, x 2.
- H 1 and H 2 are gain constants of the high gain observer.
- the function ⁇ 0 represents the nominal (reference) function of the function ⁇ employed in the operation of the high gain observer.
- Estimate error x ⁇ 1, x ⁇ 2 when using the high gain observer of formula (2) has the formula (1) is given by the following equation from the equation (2) (3).
- ⁇ is considered to be the difference between the true function ⁇ that is not actually obtained and the nominal function ⁇ 0 adopted in the high gain observer, that is, the model error of the controlled object.
- ⁇ is considered to be the difference between the true function ⁇ that is not actually obtained and the nominal function ⁇ 0 adopted in the high gain observer, that is, the model error of the controlled object.
- a positive parameter ⁇ sufficiently smaller than 1 is introduced, and H 1 and H 2 are given by the following equation (5).
- Equation (3) is expressed by the following equation (6).
- equation (6) is expressed by the following equation (8).
- the estimated value errors ⁇ 1 and ⁇ 2 can be sufficiently reduced from the model error ⁇ of the controlled object according to the equation (8). That is, if a high gain observer is used, the requirement (A) “high accuracy” required for pressure detection is satisfied by adopting a controlled object model that includes screw back pressure in the state variable. I understand.
- Equation (11) the estimated value errors ⁇ 1 (t) and ⁇ 2 (t) rapidly become 0. That is, it can be seen that the use of a high gain observer satisfies the requirement (B) “very small time delay” required for pressure detection.
- H is a gain constant of the high gain observer. Since the expression (12) includes the time derivative of the output y on the right side, it cannot be used directly as an arithmetic expression. However, the high gain observer given by the expression (12) requires the two necessary conditions (A) and (B ) (Paragraph (0028)). From the third equation of equation (1), the following equation (13) is obtained.
- Expression (15) is expressed by the following Expression (18).
- the estimated value errors x 1 to 2 can be sufficiently affected by the model error ⁇ of the control target from the equation (18).
- the requirement (A) “high accuracy” required for pressure detection is satisfied by adopting a controlled object model that includes screw back pressure in the state variable. .
- x 1 to 20 are initial values of the estimated value errors x 1 to 2 .
- Equ (20) it can be seen that if the parameter ⁇ is sufficiently smaller than 1, the estimated value errors x 1 to 2 (t) rapidly become zero. That is, it can be seen that the use of a high gain observer satisfies the requirement (B) “very small time delay” required for pressure detection.
- the high gain observer of equation (12) does not estimate the state variables that can be measured, but estimates the minimum necessary state variables, so the order is lower than the observer of equation (2), so a low-dimensional high gain observer Called.
- equation (12) is given by equation (22) below.
- FIG. 4 shows a schematic diagram of a plasticizing mechanism that does not use a pressure sensor. 4 is composed of parts having the same reference numerals as those in FIG. 2 except for the pressure sensor. Therefore, the description of FIG. 4 is the same as the description of FIG. 2 described in “Background Art” (paragraphs (0004) to (0008)). Instead of
- FIG. 1 is an example in which screw back pressure detection by a high gain observer according to an embodiment of the present invention is applied to a plasticization control device of an electric injection molding machine, and is a block for explaining an internal configuration of the plasticization control device FIG.
- the plasticizing control device includes a back pressure controller 60 with a built-in high gain observer 27, an injection motor controller (servo amplifier) 70, a screw rotation speed controller 40, and a plasticizing motor controller (servo amplifier) 50. Consists of
- the back pressure controller 60 will be described.
- the back pressure controller 60 performs a control calculation at regular time intervals and outputs a control command to the injection motor controller 70.
- the back pressure controller 60 includes a screw back pressure commander 21, a subtractor 22, a pressure controller 24, a digital / analog (D / A) converter 25, an analog / digital (A / D) converter 26, and a high gain. It consists of an observer 27.
- the screw back pressure command device 21 outputs a screw back pressure command P * b according to a time sequence to the subtractor 22.
- the injection motor is detected by the injection motor controller within 70 actual current i m is input through the A / D converter 26. Further, the backward speed signal v of the screw 9 is input from the injection motor controller 70 to the high gain observer 27 using a pulse from the motor encoder 14 of the injection servo motor 3. Further, the actual screw rotational speed N s is input to the high gain observer 27 from the plasticizing motor controller 50.
- the high gain observer 27 uses the input signals i m , v and N s to execute a built-in discrete arithmetic expression derived using a mathematical model of the plasticizing mechanism, and to estimate the screw back pressure estimated value P ⁇ . b is output.
- the estimated screw back pressure value P ⁇ b is input to the subtractor 22.
- the subtracter 22, a control deviation [Delta] P b and the screw back pressure command P * b and the screw back pressure estimated value P ⁇ b is calculated from the following equation (24).
- the subtracter 22 outputs the calculated control deviation [Delta] P b to the pressure controller 24.
- the motor current command i * m is output to the injection motor controller 70 via the D / A converter 25.
- the injection motor controller 70 includes an A / D converter 31, a pulse width modulation control (PWM) circuit 32, an injection motor actual current detector 33, and a differentiation circuit 34.
- the injection servo motor 3 is connected to the injection motor controller 70, and the motor encoder 14 is attached to the injection servo motor 3.
- the A / D converter 31 receives the motor current command i * m of the injection servo motor 3 from the back pressure controller 60 and outputs i * m to the PWM circuit 32.
- the PWM circuit 32 applies a predetermined three-phase voltage to the injection servo motor 3 based on the motor current command i * m . Thereby, the injection servo motor 3 is driven by the motor current command i * m .
- the injection motor actual current detector 33 detects the motor drive current i m, and outputs to the A / D converter 26 of the back pressure regulator 60.
- the differentiating circuit 34 receives a pulse from the motor encoder 14 of the injection servo motor 3 to detect the reverse speed v of the screw 9, and sends it to the high gain observer 27 in the back pressure controller 60. Output.
- J M is the motor body inertia moment
- J G1 is the motor side reduction gear inertia moment
- ⁇ m is the motor angular velocity
- TM is the motor torque
- r 1 is the motor side reduction gear radius
- F is the reduction gear transmission force
- t Is time The equation of motion of the ball screw 5 is given by the following equation (26).
- J S ball screw shaft moment of inertia J G2 load side reduction gear inertia
- omega s is a ball screw shaft angular speed
- r 2 is the load-side reduction gear radius
- T a is the ball screw drive torque.
- W movable unit weight g is the gravitational acceleration
- v is a screw (movable portion) retraction rate
- F a the ball screw shaft force
- F L is The load force that the screw receives from the resin
- ⁇ is the moving part-linear guide friction coefficient.
- the ball screw drive torque T a and the ball screw shaft force F a is given by the following equation (29).
- V b is the cylinder reservoir volume
- V b0 is the cylinder reservoir initial volume value (at the start of plasticization)
- Q f is the amount of molten resin supplied from the screw to the cylinder reservoir
- ⁇ is the resin volume modulus. is there.
- the motor characteristics are given by the following equation (34).
- K T is the motor torque coefficient and i m is the injection servomotor current.
- Equation (36) represents the equation of motion of the screw linear motion converted to the motor shaft
- Equation (37) represents the motor shaft equivalent equivalent moment of inertia
- equation (39) From equation (31), equation (34), and equation (36), the equation of motion of screw linear motion is given by the following equation (39).
- Expression (32) is expressed by the following Expression (41).
- v max (> 0) is the maximum screw retraction speed during plasticization
- ⁇ max (> 0) is the maximum rotation speed of the servo motor for injection corresponding to v max
- x max (> 0) is the maximum screw retraction amount during plasticization.
- i max is a motor rated current.
- P max represents the screw back pressure maximum value.
- equation (43) the following relational equation (44) is used.
- Expression (43) is expressed by the following expression (45).
- a function of the screw plasticizing resin amount [Q f / Q max] is generally screw back pressure [P b / P max] and the screw rotation speed [N s / N max].
- N max is the maximum screw speed.
- equations (49), (50) from the equations (42), (45), (47), (48). Is given as equation (51).
- Input variables u 1 and u 2 defined by the following equation (54) are introduced. It is assumed that u 1 and u 2 can be measured. Said high in the calculation of the gain observer 27, the injection servomotor actual current i m may also be considered to be equal to the motor current command i * m. time delay of i * m and i m is very small.
- ⁇ (x 2 ), ⁇ (x, u 2 ) represents a nonlinear function.
- variable y x 2 measurement of the formula (59)
- the state variable x 1 using Equation (56) is sought from the following equation (62), is replaced with the variable y s determined from the output variables y .
- the physical meaning of variable y s dimensionless screw position, an initial value of y s is set to 0 (paragraphs (0096)).
- the high gain observer 27 inputs the screw retraction speed x 2 that can be measured, the motor actual current u 1, and the screw rotation speed u 2 , and outputs an estimated value of the state variable x 3 .
- the estimated value x ⁇ 3 is given by the following equation (68) (Non-Patent Document 2).
- K is a gain constant of the high gain observer 27.
- ⁇ 0 (y), ⁇ 0 (x ⁇ 3 , u 2 , y, y s ) is the value of ⁇ (y), ⁇ (x ⁇ 3 , u 2 , y, y s ) used in the high gain observer 27. It is a nominal (reference) function.
- Expression (68) is written as the following expression (69).
- expression (72) is expressed by the following expression (77).
- eta-0 is an estimate error eta initial value of. Since the b ⁇ 0 in plasticizing step of an injection molding machine, taking sufficiently small parameter ⁇ than 1 from the equation (85), the estimate error eta ⁇ (t) is found to be a rapid 0. That is, when the high gain observer 27 is used, the screw back pressure estimated value x ⁇ 3 obtained from the equations (78), (79), and (80) is equal to the necessary condition (B) “time delay is very small. Is satisfied.
- a discrete arithmetic expression of time integration of Expression (78) is expressed by the following Expression (87) when the trapezoidal approximation method is adopted.
- the estimated value ⁇ ⁇ (t k ) at the discrete time t k is expressed by ⁇ ⁇ (k).
- u 1 (k) for even u 2 (k), shows the values at discrete time t k.
- chi 0 (k) is obtained from equation (60)
- [psi 0 (k) is obtained from equation (58) indicates the value of the discrete time t k.
- Expression (91) can be expressed by the following expression (93).
- the high gain observer 27 can obtain the screw back pressure estimated value x ⁇ 3 (k) by calculating the arithmetic expressions (88), (93), and (94) at regular time intervals ⁇ t.
- the high gain observer 27 realized by the equations (88), (93), and (94) does not estimate the state variable x 2 (k) that can be measured, but the screw back pressure x that is a necessary state variable. It is a low-dimensional high-gain observer that estimates 3 (k).
- FIG. 5 shows simulation conditions when screw back pressure control is performed.
- FIG. 5B shows a time sequence of the screw back pressure command P * b given to the screw back pressure command device 21.
- FIG. 6 shows a time response of the screw back pressure when the screw back pressure control is performed.
- 6 (a) shows the time response of the screw back pressure P b when performing the screw back pressure control plasticized controller shown in FIG. 3 using the pressure sensor 12. It can be seen that the time response of the screw back pressure command P * b and the screw back pressure shown in FIG.
- FIG. 6B shows the estimated screw back pressure value P ⁇ b output from the high gain observer 27 at this time. Since the time response of the P ⁇ b of P b and FIG. 6 (b) of FIG. 6 (a) match well, high gain observer 27, without delay the screw back pressure in time, precision It can be seen that
- Figure 6 (c) shows the time response of the screw back pressure P b when performing the screw back pressure control plasticized controller shown in FIG. 1 using the high gain observer 27. Since the time response P b time response and FIG. 6 of the screw back pressure P b (c) in FIGS. 6 (a) using the pressure sensor 12 coincides well, the without using the pressure sensor 12 It can be seen that by using the high gain observation device 27, good screw back pressure control can be realized.
- the estimated screw back pressure output from the high gain observer is used as a screw back pressure detection signal without using a pressure sensor.
- a highly reliable pressure sensor in a high pressure environment becomes expensive.
- the pressure sensor attached to the tip of the injection cylinder requires special processing, and the work cost cannot be ignored.
- the load cell attached to the injection shaft system extending from the injection motor to the injection screw complicates the mechanical structure for incorporation, and further reduces the mechanical rigidity of the injection shaft system.
- It is expensive to use two types of pressure sensors with different measurement ranges in order to improve the control accuracy of the screw back pressure (Patent Document 12).
- the estimated screw back pressure value output from the high gain observer is highly accurate and has a very small time delay, so that it can be used as a screw back pressure monitoring signal and a control feedback signal. Therefore, it is considered that the plasticization control device and the plasticization control method of the electric injection molding machine using the high gain observer according to the present invention have a value that is sufficiently utilized.
Abstract
Description
(1) 高圧環境下で信頼性の高い圧力センサは高価になる。
(2) 射出シリンダ先端部への圧力センサ取付けは、特別な加工を施す必要があり、作業コストが無視できない。
(3) 射出用モータから射出スクリュに至る射出軸系に取り付けるロードセルは、組み込むための機械構造を複雑にし、更には射出軸系の機械剛性の低下を招く。
(4) 歪みゲージを検出部に使用するロードセルでは、微弱なアナログ信号に対するノイズ対策が必要になり、また信号アンプのゼロ点調整やスパン調整等にも人手による作業が必要になる(特許文献13)。
(5) スクリュ背圧の制御精度向上のために計測範囲の異なる2種類の圧力センサを使用すると高価になる(特許文献12)。
(A)高精度である
(B)時間的遅れが非常に小さい
この2つの必要条件を満たす圧力検知手段として、高ゲイン観測器(非特許文献1)の手法を採用する。計測できる変数を入力して、すべての状態変数を推定する高ゲイン観測器が、前記2つの必要条件(A)、(B)を満たしていることを簡単な制御対象モデルを使って説明する。式(1)は制御対象モデルの状態方程式と出力方程式を示す。
(1) 計算手順1
(A)高精度である
(B)時間的遅れが非常に小さい
が満たされることを明らかにする。式(79)で公称関数χ0(y)、ψ0(η^、u2、y、ys)ではなく、実際には得られない真の関数χ(y)、ψ(η、u2、y、ys)を使用したときに得られる変数ηは次の式(81)で決まる。
スクリュ最大後退量 xmax=20.0cm
スクリュ最大後退速度 vmax=2.0cm/sec
スクリュ背圧最大値 Pmax=19.6MPa
射出用モータ最大回転数 ωmax=31.67rad/sec(302.4rpm)
制御対象のモデル定数を使って、式(56)~式(58)で使われる係数a,b,c,dは次の式(95)の値を用いた。
(1) 高圧環境下で信頼性の高い圧力センサは高価になる。
(2) 射出シリンダ先端部への圧力センサ取付けは、特別な加工を施す必要があり、作業コストが無視できない。
(3) 射出用モータから射出スクリュに至る射出軸系に取り付けるロードセルは、組み込むための機械構造を複雑にし、更には射出軸系の機械剛性の低下を招く。
(4) 歪みゲージを検出部に使用するロードセルでは、微弱なアナログ信号に対するノイズ対策が必要になり、また信号アンプのゼロ点調整やスパン調整等にも人手による作業が必要になる(特許文献13)。
(5) スクリュ背圧の制御精度向上のために計測範囲の異なる2種類の圧力センサを使用すると高価になる(特許文献12)
2 射出シリンダ
3 射出用サーボモータ
4 減速機
5 ボールネジ
6 軸受
7 ナット
8 可動部
9 スクリュ
10 減速機
11 可塑化用サーボモータ
12 圧力センサ
13 リニアガイド
14 モータエンコーダ
15 モータエンコーダ
16 ホッパー
17 キャビティ
20 背圧制御器
21 スクリュ背圧指令器
22 減算器
23 アナログ/デジタル(A/D)変換器
24 圧力制御器
25 デジタル/アナログ(D/A)変換器
26 アナログ/デジタル(A/D)変換器
27 高ゲイン観測器
30 射出用モータ制御器(サーボアンプ)
31 アナログ/デジタル(A/D)変換器
32 パルス幅変調制御(PWM)回路
33 射出用モータ実電流検出器
34 微分回路
40 スクリュ回転数制御器
41 スクリュ回転数指令器
50 可塑化用モータ制御器(サーボアンプ)
51 減算器
52 微分回路
53 速度制御器
54 パルス幅変調制御(PWM)回路
60 背圧制御器
70 射出用モータ制御器(サーボアンプ)
Claims (2)
- 電動射出成形機の可塑化制御装置であって、射出用サーボモータの回転は減速機を介してボールネジに伝えられ、前記ボールネジの回転はボールネジ軸上のナットの直線運動に変換され、前記ナットにより駆動される可動部を介してスクリュが前後進移動し、前記スクリュの前後進により射出シリンダ先端部に貯留された溶融樹脂への加圧(スクリュ背圧)を実現する射出軸系と、可塑化用サーボモータの回転は減速機を介してスクリュを回転し樹脂ペレットを溶融するスクリュ回転駆動系とからなる可塑化機構の運動を表現する数式モデルとして、スクリュ後退速度変数とスクリュ背圧変数の2変数を状態変数とし前記射出用サーボモータへの制御信号として印加されるモータ電流指令信号或はモータ実電流信号とスクリュ回転数およびスクリュ位置の3変数を入力変数とする状態方程式と計測できる状態変数として前記スクリュ後退速度変数を出力変数とする出力方程式からなる連続時間系数式モデルおよびスクリュ位置とスクリュ後退速度の関係を与える時間積分式を採用し、前記時間積分式に対して時間積分近似を適用して導出した時間積分離散演算式および前記連続時間系数式モデルから前進矩形近似を適用して導出した離散演算式を一定時間間隔毎に実行する高ゲイン観測器と、スクリュ背圧指令を出力するスクリュ背圧指令器と、前記高ゲイン観測器が前記射出用サーボモータの軸に設けたモータエンコーダと微分回路で検出されるスクリュ後退速度信号と前記モータ電流指令信号或は前記モータ実電流信号および可塑化用モータ制御器で検出されるスクリュ回転数信号を入力されて内蔵する前記時間積分離散演算式と前記離散演算式を使用して算出して出力するスクリュ背圧推定値と前記スクリュ背圧指令器が出力する前記スクリュ背圧指令とが入力されて、前記スクリュ背圧指令と前記スクリュ背圧推定値との差を出力する減算器と、前記減算器の出力を入力して前記スクリュ背圧推定値が前記スクリュ背圧指令に追従するように前記モータ電流指令信号を算出する圧力制御器と、を含むスクリュ背圧制御器と、前記モータ電流指令信号が入力される射出用モータ制御器と、可塑化用サーボモータの回転数制御を行う可塑化用モータ制御器と、
を具備することを特徴とする電動射出成形機の可塑化制御装置 - 電動射出成形機の可塑化制御方法であって、射出用サーボモータの回転は減速機を介してボールネジに伝えられ、前記ボールネジの回転はボールネジ軸上のナットの直線運動に変換され、前記ナットにより駆動される可動部を介してスクリュが前後進移動し、前記スクリュの前後進により射出シリンダ先端部に貯留された溶融樹脂への加圧(スクリュ背圧)を実現する射出軸系と、可塑化用サーボモータの回転は減速機を介してスクリュを回転し樹脂ペレットを溶融するスクリュ回転駆動系とからなる可塑化機構の運動を表現する数式モデルとして採用した、スクリュ後退速度x2とスクリュ背圧x3を状態変数とし射出用サーボモータへのモータ電流指令信号或はモータ実電流信号u1とスクリュ回転数u2とスクリュ位置ysを入力変数とする下記(数77)の状態方程式(97)と前記スクリュ後退速度x2を出力変数yとする出力方程式(98)および前記スクリュ位置ysと前記スクリュ後退速度yの関係を与える下記(数78)の時間積分式(100)に対して、前記時間積分式(100)に時間積分近似を適用して導出した下記(数79)の時間積分離散演算式(101)および前記状態方程式(97)と出力方程式(98)から前進矩形近似を適用して導出した下記(数80)の離散演算式(103)及び(数81)の離散演算式(105)を一定時間間隔毎に実行する高ゲイン観測器が、前記射出用サーボモータの軸に設けたモータエンコーダおよび微分回路で検出されるスクリュ後退速度信号と前記モータ電流指令信号或は前記モータ実電流信号および可塑化用モータ制御器で検出されるスクリュ回転数信号を入力信号としてスクリュ背圧推定値x^3を出力し、減算器が、スクリュ背圧指令器が出力するスクリュ背圧指令と前記スクリュ背圧推定値を入力信号として前記スクリュ背圧指令と前記スクリュ背圧推定値との差を出力し、圧力制御器が、前記減算器の出力を入力信号として前記スクリュ背圧推定値が前記スクリュ背圧指令に追従するように前記モータ電流指令信号を出力し、射出用モータ制御器が、前記モータ電流指令信号を入力信号として、前記射出用サーボモータに前記モータ電流指令信号に相当するモータトルクを発生させて前記スクリュ背圧指令に等しいスクリュ背圧を実現する電動射出成形機の可塑化制御方法
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US8871128B2 (en) * | 2010-11-01 | 2014-10-28 | Noriyuki Akasaka | Device and method for pressure control of electric injection molding machine |
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