JP3854602B2 - Multi-axis drive - Google Patents

Description

  The present invention relates to a multi-axis drive device, and more particularly to a multi-axis drive device suitable as a multi-axis drive device for an injection molding machine.

In an injection molding machine, a plurality of parallel ball screw shafts are rotationally driven by individual motors, and the multi-axis drive is configured to advance and retract the injection screw in the axial direction of the ball screw shaft by rotation of the ball screw shaft. The device is in practical use. In such a multi-axis drive device, the positional deviation of the injection screw with respect to the target position is detected, and each motor is driven by a speed command based on this positional deviation. In addition, the speed command for each motor is corrected based on the deviation of the movement position of the injection screw on each ball screw shaft so that the deviation is eliminated, thereby preventing the displacement of the movement position of the injection screw on each ball screw shaft. Is done. (For example, refer to Patent Document 1).
JP 2002-137269 A

  The multi-axis drive device as described above is configured so that the feed speed of the injection screw as the driven body can be controlled not only by the speed command based on the position deviation but also by the speed command set by the user. Is desirable. In this case, in the final period of the injection process, it is necessary to accurately control the injection screw at the target position by controlling the feed speed of the injection screw by the speed command based on the position deviation.

  An object of the present invention is to provide a multi-axis drive device capable of accurately positioning a driven body at a target position while realizing control of a feed speed of the driven body based on a speed command set by a user. It is in.

  A multi-axis drive device according to the present invention includes a driven body that is moved in the axial direction of a plurality of shafts by rotation or movement of the plurality of shafts, a plurality of driving means that rotate or move the respective shafts, and the respective driving devices. Control means for controlling the means, and the control means is commanded with first speed command generating means for generating a first speed command corresponding to a positional deviation of the driven body with respect to the commanded target position. A second speed command generating means for generating a second speed command corresponding to the target speed of the driven body, and a speed command for selecting a smaller speed command of the first speed command and the second speed command. Selecting means, and configured to apply the speed command selected by the speed command selecting means to the control of each driving means.

The control means includes a deviation detecting means for detecting mutual deviations of the positions of the driven bodies in the plurality of axes, and a correcting means for correcting the speed command applied to each driving means so that the deviation is eliminated. Further, it can be provided.
The position deviation may be a position deviation obtained by averaging the positions of the driven bodies on the plurality of axes.

  The driven body is, for example, a movable mold of an injection molding machine or an injection screw of the injection molding machine. When the driven body is the injection screw, the control means can further include third speed command generation means for generating a third speed command corresponding to the deviation of the injection pressure with respect to the commanded target injection pressure. The speed command selecting means is provided with means for selecting the third speed command as a speed command for the driving means when the third speed command is smaller than the first and second speed commands.

PI compensation means for performing PI compensation processing on the deviation of the injection pressure to form the third speed command, and an integration element of the PI compensation means when the third speed command is selected by the speed command selection means. Integration initializing means for setting an initial integration value.
The integration initialization unit is configured to set, for example, the speed command selected by the speed command selection unit as the initial integration value. The integral initialization means may be configured to set the initial integral value obtained by subtracting the output of the proportional element of the PI compensation means from the speed command selected by the speed command selection means.

  According to the present invention, it is possible to accurately position the driven body at the target position while realizing the control of the feed speed of the driven body based on the speed command set by the user.

FIG. 1 is a block diagram showing an embodiment of a multi-axis drive device according to the present invention. The multi-axis drive device includes an injection screw moving mechanism 10 of an injection molding machine and a control device 20 that controls the injection screw moving mechanism 10.
In the injection screw moving mechanism 10, the base of the injection screw 11 that is a driven body is fixedly supported at the center of the support 12. Ball screw nuts 13 </ b> A and 13 </ b> B are provided on the support 12 at symmetrical positions with respect to the central axis of the injection screw 11. The ball screw shafts 14A and 14B are respectively screwed into the ball screw nuts 13A and 13B in a form parallel to the central axis of the injection screw 11, and are rotationally driven by the screw moving electric motors 15A and 15B, respectively.
According to the injection screw moving mechanism 10, the injection screw 11 can be advanced and retracted together with the support 12 by simultaneously rotating the motors 15 </ b> A and 15 </ b> B.

The position sensors 16A and 16B detect the moving position of the injection screw 11 as the position of the ball screw nuts 13A and 13B (the position of the support 12) on the ball screw shafts 14A and 14B, respectively. The pulse encoder generates a number of pulse signals corresponding to the rotation amount of 15B.
The pressure sensors 17A and 17B detect the injection reaction force of the injection screw 11 acting between the ball screw nut 13A and the ball screw shaft 14A and the reaction force acting between the ball screw nut 13B and the ball screw shaft 14B as the injection pressure. For example, it is constituted by a load cell.

  The control device 20 includes a host control unit 21, a servo control unit 23, and amplifiers 24A and 24B. FIG. 2 shows the configuration of the speed command generator included in the host controller 21. In FIG. 2, a position command setting unit 210, a speed command setting unit 211, and a pressure command setting unit 212 are a command indicating a target position (injection completion position) of the injection screw 11 and a command indicating a target moving speed of the screw 11. And a command indicating the target injection pressure are provided for setting manually.

The average position calculation unit 213 executes a calculation for averaging the respective movement positions X _A0 and X _B0 of the injection screw 11 detected by the position sensors 16A and 16B. The calculation unit 214 calculates a deviation between the target position set by the position command setting unit 210 and the average position (X _A0 + X _B0 ) / 2 calculated by the average position calculation unit 213, and this position deviation is multiplied by after being multiplied by the gain multiplier K _p in part 215, it is input to the switching unit 216 as a speed command V _d based on the position deviation.

The average pressure calculation unit 217 executes calculation for averaging the injection pressure detected by the pressure sensors 17A and 17B. The calculation unit 218 calculates a deviation between the target injection pressure commanded by the pressure command setting unit 212 and the average pressure calculated by the average pressure calculation unit 217, and this pressure deviation is subjected to PI compensation processing by the pressure PI compensation unit 219. Is applied to the low value selection unit 220 as a speed command V _p based on the pressure deviation.

The low value selection unit 220 compares the speed command V _r set by the speed command setting unit 211 with the speed command V _p based on the pressure deviation, and selects the smaller one as the speed command V _m . . On the other hand, the switching unit 216 compares the speed command V _d and the speed command V _m based on the positional deviation, to select a smaller one of those among the speed command V _CMD. As a result, the minimum speed command among the speed commands V _d , V _r and V _p is selected as the speed command V _CMD .

Next, the servo control unit 23 shown in FIG. 1 will be described. In the servo control unit 23, the position deviation calculation unit 230 is a position deviation (X _A0 −X _B0 ) of the injection screw 11 detected by the position sensors 16A and 16B, that is, relative to the ball screw nuts 13A and 13B. Calculate the amount of displacement. Further, the synchronization control unit 231 multiplies the position deviation (X _A0 −X _B0 ) calculated by the position deviation calculation unit 230 by a predetermined gain multiplier K ₀ to obtain a speed command correction value K ₀ (X _A0 for synchronous control). _-XB0 ).
The calculation unit 232 performs a calculation of adding the speed command correction value K ₀ (X _A0 −X _B0 ) calculated by the synchronous control unit 231 to the speed command V _CMD output from the host control unit 21, and The calculation unit 233 executes a calculation for subtracting the speed command correction value K ₀ (X _A0 −X _B0 ) from the speed command. Therefore, the speed commands corrected so as to eliminate the relative displacement of the ball screw nuts 13A and 13B are output from the calculation units 232 and 233, respectively.

The corrected speed commands output from the arithmetic units 232 and 233 are given to the amplifiers 24A and 24B after being subjected to PI processing by the speed PI compensation units 234A and 234B, respectively. The motors 15A and 15B are driven so that the ball screw nuts 13A and 13B are moved at a speed of As a result, the positions of the ball screw nuts 13A and 13B are synchronized, and the injection screw 11 is smoothly moved.
When a synchronous belt is wound between the rotating shafts of the motors 15A and 15B to mechanically synchronize the rotation of the motors 15A and 15B, the speed command correction process as described above is not necessary. .

According to the injection molding machine to which the multi-axis drive device according to this embodiment is applied, as described above, the speed command V _d based on the position deviation, the speed command V _r set by the speed command setting unit 211, The smallest speed command among the speed commands V _p based on the pressure deviation is selected.
At the beginning of the injection process, both the speed command V _d based on the position deviation and the speed command V _p based on the pressure deviation are both large, so the speed command V _r is selected and the injection screw 11 moves in the injection direction at this speed V _r. proceed. When the speed command V _p becomes smaller than the speed command V _r with increasing injection pressure, since the speed command V _p is selected, the injection screw 11 is advanced in the injection direction at the velocity V _p become.

Immediately before the end of the injection process in which the injection screw 11 is in the vicinity of the stop position, the speed command Vd based on the position deviation is the smallest, so this speed command Vd is selected. Therefore, the injection screw 11 is positioned at the target position with extremely high accuracy while moving at a low speed.
If the moving speed of the injection screw 11 is controlled only by the speed command Vd based on the position deviation as in the prior art, the calculation section (comprising a deviation counter) that calculates the position deviation as the injection pressure increases. Since the accumulated pulse of 214 increases, an excessive speed command due to the accumulated pulse may cause the injection screw 11 to move at an unexpected speed, which causes proper positioning of the injection screw 11. Not only will it be hindered, it will be a factor in generating defective molded products.
On the other hand, according to the above embodiment, the injection screw 11 is moved to the vicinity of the stop position by the speed command Vp based on the pressure deviation. Therefore, the injection screw 11 can be smoothly and highly accurately without increasing the accumulated pulse. Can be positioned at the target position.

上記の式によって速度指令Ｖ_pを導出した場合、積分時間ｔ_ipによる圧力上昇の遅延のため、ユーザ設定による速度指令Ｖ_rから圧力偏差に基づく速度指令Ｖ_pへの切り替えの際に、射出圧力がユーザ設定の圧力指令に基づく大きさまで速やかに上昇しないおそれがある。 Meanwhile, the host controller 21 derives the speed command V _p by performing the operation based on the example the following formula in the pressure PI compensator 219, and the speed command V _r The speed command V _p at a low value selector 220 Comparing.

When the speed command V _p is derived by the above equation, the injection pressure is changed when switching from the speed command V _r by the user setting to the speed command V _p based on the pressure deviation because of a delay in pressure increase due to the integration time t _ip. May not rise rapidly to a magnitude based on a user-set pressure command.

Therefore, in the embodiment of FIG. 3, the speed command currently selected by the low value selection unit 220 is taken into the integration element 219a of the pressure PI compensation unit 219, and the speed command V based on the pressure deviation from the speed command V _r set by the user. When switching to _p , the acquired speed command is used as the initial integral value. When the speed command V _r is switched to the speed command V _p , the speed command V _r is taken into the integral element 219a of the PI compensation unit 219. Therefore, to prevent the transient decrease in the velocity command V _p when switching the speed command V _p from the speed command V _r if executed an integration initialization process as described above, to improve the controllability of the injection pressure be able to.

On the other hand, when the speed command V _r has a large value when switching from the speed command V _r to the speed command V _p , the initial speed command V _p based on the integral initialization process becomes excessive. This may cause a phenomenon such as an overshoot in the injection pressure. In order to cope with this, as indicated by a dotted line in FIG. 3, the output of the proportional element 219b of the PI compensation unit 219 is input to the arithmetic unit 219c, and the output of the proportional element 219b is obtained from the currently selected speed command. It is possible to perform a subtraction operation and use the operation result as an initial integration value. If such an integral initialization process is executed, even if the speed command V _r has a large value, a speed command V _p having an appropriate magnitude is formed. The phenomenon can be suppressed.

The multi-axis drive device according to the present invention includes a mold clamping device for an injection molding machine, a mold clamping device for a low pressure injection molding machine such as an injection press machine, and other devices that compress or press an object by synchronizing the operations of a plurality of shafts. It can also be applied to other mold clamping devices.
FIG. 4 illustrates the configuration of the mold clamping device of the injection molding machine. The mold clamping device includes four ball screw shafts 42A to 42D that are rotationally driven by electric motors 41A to 41D, and the axial direction of the ball screw shafts 42A to 42D as the ball screw shafts 42A to 42D rotate. A movable mold 43 that advances and retreats is provided. In practice, as shown in FIG. 5, the ball screw shafts 42A and 42B are screwed into the upper end portions of the movable mold 43, and the ball screw shafts 42C and 42D are screwed into the lower end portions of the mold 43, respectively. Has been.

Position sensors 45A to 45D that individually detect the positions of the movable molds 43 on the ball screw shafts 42A to 42D are connected to the control device 50 that controls the motors 41A to 41D of the mold clamping device.
The control device 50 has a configuration according to the control device 20 shown in FIG. 1, that is, the control device 50 includes a host control unit 51, a servo control unit 53, and amplifiers 54A to 54D as shown in FIG. ing. FIG. 7 shows the configuration of the speed command generator included in the host controller 51. In FIG. 7, a position command setting unit 510 and a speed command setting unit 511 are for manually setting commands indicating the target position and target moving speed of the movable mold 43, respectively.

The average position calculation unit 513 executes calculation for averaging the movement positions X _{A to} X _D of the movable mold 43 detected by the position sensors 45A to 45D. The calculation unit 514 calculates the deviation between the target position commanded by the position command setting unit 510 and the average position (X _A + X _B + X _C + X _D ) / 2 calculated by the average position calculation unit 513. The deviation is multiplied by the gain multiplier K _p ′ by the multiplication unit 515 and then input to the low value selection unit 520 as a speed command V _d ′ based on the position deviation.
The low value selection unit 520 compares the speed command V _r ′ set by the speed command setting unit 511 with the speed command V _d ′ based on the position deviation, and uses the smaller one as the final speed command. select.

Next, the servo control unit 53 shown in FIG. 6 will be described. In the servo control section 53, the position deviation calculation unit 530, a position sensor 45A, each detected position of 45B (X _A, the average value X _avg (X _A of X _B, and X _B), the position sensor 45C, each of 45D detection position (X _C, the average value X _avg (X _C of X _D, calculates a deviation between X _D). Then, the synchronization control unit 531, a predetermined gain multiplier to the calculated position deviation in the deviation calculating section 530 The speed command correction value K _S1 [X _avg (X _A , X _B ) −X _avg (X _C , X _D )] for synchronous control is created by multiplying K _S1 .

The calculation unit 532 performs a calculation for adding the speed command correction value K _S1 [X _avg (X _A , X _B ) −X _avg (X _C , X _D )] to the speed command output from the host control unit 51. In addition, the calculation unit 533 executes a calculation for subtracting the speed command correction value K _S1 [X _avg (X _A , X _B ) −X _avg (X _C , X _D )] from the speed command. Therefore, from the calculation units 532 and 533, a speed command corrected so as to eliminate the shift amount between the position of the movable mold 43 on the ball screw shafts 42A and 42B and the position of the movable mold 43 on the ball screw shafts 42C and 42D is issued. Each is output.

  The corrected speed command output from the calculation unit 532 is subjected to PI compensation processing by the speed PI processing units 534 and 534B, and is then supplied to the amplifiers 54A and 54B. Similarly, the corrected speed command output from the arithmetic unit 533 is subjected to PI processing by the speed PI processing units 534C and 534D, and then is given to the amplifiers 54C and 54D. Therefore, the movable mold 43 shown in FIG. 4 is moved while the deviation between the positions on the ball screw shafts 42A and 42B and the positions on the ball screw shafts 42C and 42D is corrected, that is, the above positions are synchronized. .

The control device 50 can further have a function of correcting the relative displacement of the position of the movable mold 43 on the ball screw shafts 42A and 42B and the relative displacement of the position of the movable mold 43 on the ball screw shafts 42C and 42D. It is.
In this case, in the deviation calculation unit 530, the deviations X _A -X _B of the positions X _A and X _B detected by the position sensors 45A and 45B and the positions X _C and X _D detected by the position sensors 45C and 45D are detected. The deviation X _C -X _D is further calculated. Then, in the synchronization control unit 531, a speed command correction value K _S2 (X _A −X _B ) for synchronization control obtained by multiplying the position deviation X _A −X _B by a predetermined gain multiplier K _S2 and a position deviation X _C −X. A speed command correction value K _S3 (X _C −X _D ) for synchronous control is generated by multiplying _D by a predetermined gain multiplier K _S3 . Further, as shown in FIG. 8, between the calculation unit 532 and the speed PI processing unit 534A, between the calculation unit 532 and the speed PI processing unit 534B, between the calculation unit 533 and the speed PI processing unit 534C, and between the calculation unit 533 and the speed PI processing unit. Operation units 535A, 535B, 535C, and 535D are provided between 534D, respectively.

In the calculation unit 535A, the correction value K _S2 (X _A −X _B ) is added to the output of the calculation unit 532, and in the calculation unit 535B, the correction value K _S2 (X _A −X is calculated from the output of the calculation unit 532). _B ) is reduced. On the other hand, in the calculation unit 535C, the output of the arithmetic unit 533 the correction value K _S3 (X _C -X _D) is added, and in the calculation unit 535D, the correction value K _S3 (X _C from the output of the arithmetic unit 533 -X _D ) is reduced.
Therefore, in the movable mold 43, the mutual displacement between the ball screw shafts 42A and 42B is corrected, and the mutual displacement between the ball screw shafts 42C and 42D is corrected.

Eventually, according to the embodiment applied to the mold clamping device of this injection molding machine, during the period in which the speed command V _r ′ and the speed command V _d ′ shown in FIG. 7 are in the state of V _r ′ <V _d ′, That is, during a period from when mold clamping is started to immediately before the mold clamping is finished, a speed command V _r ′ set by the user is selected, and the movable mold 43 advances at this speed. Thereafter, the speed command V _d ′ based on the position deviation is selected, the movable mold 43 is positioned at the target position with extremely high accuracy, and the mold clamping is completed.

  In addition, during the movement of the movable mold 43, the deviation between the position of the mold 43 on the ball screw shafts 42A and 42B and the position of the mold 43 on the ball screw shafts 42C and 42D is corrected, and the ball Since the shift of each position of the movable mold 43 on the screw shafts 42A and 42B and the shift of each position of the movable mold 43 on the ball screw shafts 42C and 42D are corrected, the mold 43 is moved along the respective axes 42A to 42D. It is possible to move very smoothly while synchronizing the position.

  The position synchronization means of the mold 43 is not limited to the above configuration. That is, for example, the calculation units 532 and 533 in FIG. 8 are deleted, and a speed command output from the host control unit 51 is added to the calculation units 535A, 535B, 535C, and 535D as shown in FIG. good.

1 is a block diagram showing an embodiment of a multi-axis drive device according to the present invention. It is a block diagram which shows the structure of the speed command generation part contained in a high-order control part. It is a block diagram which shows an integral initialization process. It is the top view which showed typically the structure of the mold clamping apparatus of an injection molding machine. It is a side view which shows the positional relationship of a movable metal mold | die and a ball screw axis | shaft. It is a block diagram which shows the structural example of a control apparatus. It is a block diagram which shows the structure of the speed command generation part contained in a high-order control part. It is a block diagram which shows an example of the position synchronization means of a metal mold | die. It is a block diagram which shows the other example of the position synchronization means of a metal mold | die.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Injection screw moving mechanism 11 Injection screw 14A, 14B Ball screw shaft 15A, 15B Motor 16A, 16B Position sensor 17A, 17B Pressure sensor 20 Control apparatus 21 High-order control part 23 Servo control part 210 Position command setting part 211 Speed command setting part 212 Pressure command setting unit 216 Switching unit 220 Low value selection unit 230 Position deviation calculation unit 231 Synchronous control unit 41A to 41D Motor 42A to 42D Ball screw shaft 43 Movable mold 50 Controller 51 Upper level control unit 53 Servo control unit 510 Position command setting 511 Speed command setting unit 520 Low value selection unit 530 Position deviation calculation unit 531 Synchronization control unit

Claims (9)

A driven body that is moved in the axial direction of the axes by rotation or movement of a plurality of axes;
A plurality of driving means for rotating or moving each of the shafts;
Control means for controlling each of the driving means,
The control means includes
First speed command generating means for generating a first speed command (V _d , V _d ′) corresponding to the position deviation of the driven body with respect to the commanded target position;
Second speed command generating means for generating a second speed command (V _r , V _r ′) corresponding to the commanded target speed of the driven body;
A speed command selecting means for selecting a speed command of a smaller one of the first speed command (V _d , V _d ′) and the second speed command (V _r , V _r ′) ;
The second speed command (V _r , V _r ′) is set smaller than the first speed command (V _d , V _d ′) when the driven body is at a predetermined movement start position ,
A multi-axis drive device configured to apply the speed command selected by the speed command selection means to the control of each drive means.   The control means includes a deviation detecting means for detecting mutual deviations of the positions of the driven bodies in the plurality of axes, and a correcting means for correcting the speed command applied to each driving means so that the deviation is eliminated. The multi-axis drive device according to claim 1, further comprising:   The multi-axis drive device according to claim 1, wherein the position deviation is a deviation of a position obtained by averaging the positions of the driven bodies on the plurality of axes.   The multi-axis drive device according to claim 1, wherein the driven body is a movable mold of an injection molding machine.   The multi-axis drive device according to claim 1, wherein the driven body is an injection screw of an injection molding machine.   The control means further includes third speed command generation means for generating a third speed command corresponding to the deviation of the injection pressure with respect to the commanded target injection pressure, and the speed command selection means includes the third speed command generation means. 6. The multi-axis drive device according to claim 5, further comprising means for selecting the third speed command as a speed command for the drive means when is smaller than the first and second speed commands.   PI compensation means for performing PI compensation processing on the deviation of the injection pressure to form the third speed command, and an integration element of the PI compensation means when the third speed command is selected by the speed command selection means. The multi-axis drive device according to claim 6, further comprising integration initialization means for setting an initial integration value.   The multi-axis drive device according to claim 7, wherein the integral initialization unit is configured to set a speed command selected by the speed command selection unit as the initial integral value.   The integral initialization means is configured to set a value obtained by subtracting the output of the proportional element of the PI compensation means from the speed command selected by the speed command selection means as the initial integral value. The multi-axis drive device according to claim 7.

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