Machine-tool control system

Abstract

To provide a machine-tool control system capable of positioning a work-piece within an in-position range.SOLUTION: A machine-tool control system comprises a first motor 18 that drives a mounting unit, a second motor 14 that drives a mounted unit placed on the mounting unit, a clamp mechanism 15 that is provided on the mounted unit, and a control device. The control device, after completing a positioning of the mounted unit, switches the clamp mechanism 15 from an un-clamping state over to a clamping state. The control device, if positioning the mounting unit in a duration of switching the state of the clamp mechanism, brings an upper limit of acceleration of the mounting unit in the duration of switching the state lower than an upper limit of acceleration in normal times.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This specification relates to a control system for a machine tool having a function of controlling a motor drive unit mounted on a motor drive unit.

Background Art

[0002] A machine tool generally includes a drive unit driven by a motor to determine the relative position between a tool and a workpiece and perform various machining operations. Further, in order to perform machining with high degrees of freedom, there is also a mechanical structure in which an additional drive unit is provided on one drive unit. Hereinafter, one drive unit will be referred to as a "mounting unit", and an additional drive unit mounted on the mounting unit will be referred to as a "mounted unit". In a machining center, examples of configurations including a mounting unit and a mounted unit include a circular table, a trunnion unit, and the like. A circular table is a device having a table for fixing a workpiece, on which a rotating unit is mounted on a translation unit. A trunnion unit is a device having a tilt mechanism between a circular table and a translation unit.

[0003] Some of these rotating units are provided with a clamping mechanism so that their positions are not shifted by the machining load. When indexing the rotating unit, the rotating unit is indexed after the clamping mechanism is unclamped, and the indexing is completed by clamping again.

[0004] Patent Document 1 discloses a five-axis machine tool including a worktable for fixing a workpiece, a rotating unit for rotating the worktable in two axial directions of inclination and turning, and a spindle unit for moving a spindle to which a tool is attached in three axial directions of translation. In Patent Document 1, in this five-axis machine tool, when the workpiece position deviation exceeds a threshold value during workpiece positioning, it is unclamped and repositioned.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] Hereinafter, a circular table will be taken as an example for explanation. FIG. 1 is a schematic view of a circular table seen from above. As shown in this FIG. 1, consider the case where the center of gravity of the entire circular table 1 including the workpiece 2 is displaced from the rotation center axis of the circular table 1. The loading unit 4 is a translation unit that loads and translates the circular table 1. When this loading unit 4 accelerates or decelerates, a torque is generated to rotate the circular table 1 due to inertia. When the loading unit 4 accelerates after the circular table 1 is indexed, as shown in FIG. 2, after the angular velocity (first stage) of the circular table 1 becomes 0, the clamp command (third stage) turns on, and immediately thereafter, the loading unit 4 accelerates (fifth stage). Here, there is a mechanical delay from when the clamp command (third stage) turns on until the clamp torque (fourth stage) is generated. Therefore, a torque due to inertia is generated before the clamping of the circular table 1 is completed (that is, before the clamp torque is generated), and the circular table 1 is clamped in a state where it is greatly displaced from the target indexing position. Therefore, there is a problem that the angle tracking error (hereinafter referred to as "DIFF", second stage) of the circular table 1 is outside the imposition range E at the time of completion of clamping.

[0007] When the same operation is performed in the machine tool described in Patent Document 1, the deviation can be reduced by detecting the deviation after positioning and repositioning. However, there is a problem that the wear of the clamp mechanism and the like may be accelerated because the unclamping operation and the clamping operation are performed. MEANS FOR SOLVING THE PROBLEM

[0008] The control system of the machine tool disclosed in this specification includes a first motor that drives a loading unit, a second motor that drives a loaded unit loaded on the loading unit, a clamping mechanism provided on one of the loading unit and the loaded unit, and a control device that controls the driving of the first motor, the second motor, and the clamping mechanism. After the positioning of a preceding unit, which is one of the loading unit and the loaded unit, is completed, the control device switches the state of the clamping mechanism provided on the preceding unit from an unclamped state to a clamped state. When positioning a subsequent unit, which is the other of the loading unit and the loaded unit, during the state switching period of the clamping mechanism, the control device reduces the upper limit of the acceleration of the subsequent unit during the state switching period to be lower than the upper limit of the acceleration during normal times.

Effect of the Invention

[0009] According to the control system of the machine tool disclosed in this specification, since the upper limit of the acceleration of the subsequent unit during the state switching period of the clamping mechanism is reduced to be lower than the upper limit of the acceleration during normal times, it is possible to effectively prevent the positional deviation of the preceding unit after positioning.

Brief Description of the Drawings

[0010]

Figure 1

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Figure 18

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the control system of the machine tool will be described. FIG. 1 is a schematic plan view of a circular table which is an example of a control object. In FIG. 1, the circular table 1 is a rotating unit for fixing a workpiece and rotates clockwise or counterclockwise. The workpiece 2 is fixed to the circular table 1, and when the circular table 1 rotates clockwise or counterclockwise, the workpiece position also changes. This circular table 1 serves as the loaded unit. The loading unit 4 loads the circular table 1 and moves translationally in the left-right direction of FIG. 1.

[0012] FIG. 3 is a block diagram showing the configuration of the control system. In FIG. 3, a position command generation unit 11, a motor control unit 13, a motor control unit 17, a machine control unit 19, a position command correction unit 20, and a center of gravity distance estimation unit 21 are a control device 50 that controls the driving of motors 14 and 18 and a clamp mechanism 15. Such a control device 50 is, for example, a computer having a processor and a memory. In FIG. 3, the position command generation unit 11 generates a position command for the loading unit 4 and the unit to be loaded (the circular table 1 in this example). The motor 14 that drives the unit to be loaded is provided with an encoder 12 and detects the current position of the motor 14. The motor control unit 13 supplies current to the motor 14 by known feedback control, current control, or the like so that the current position follows the position command. The motor 14 generates torque by the current from the motor control unit 13 and drives the unit to be loaded. The machine control unit 19 outputs a clamp operation signal to the clamp mechanism 15. The clamp mechanism 15 is driven by a hydraulic device in response to the clamp operation command output by the machine control unit 19 and switches between an unclamped state and a clamped state. The motor 18 that drives the loading unit 4 also has an encoder 16. The motor control unit 17 supplies current to the motor 18 by known feedback control, current control, or the like so that the current position detected by the encoder 16 follows the position command.

[0013] In the control system of FIG. 3, after the positioning of the circular table 1, which is the unit to be loaded, is completed, the positioning of the loading unit 4 is performed. Hereinafter, the circular table 1 that is positioned first is referred to as the "preceding unit" as necessary, and the "loading unit" that is positioned after the preceding unit is referred to as the "subsequent unit". The control system reduces the upper limit of the acceleration of the loading unit (i.e., the subsequent unit) according to the distance from the rotation center axis of the rotating unit to the center of gravity position of the rotating unit. Note that the "center of gravity position of the rotating unit" is the center of gravity position including all objects that rotate together with the rotating unit, such as the workpiece 2 attached to the rotating unit. This will be described below.

[0014] Here, consider the case where the workpiece 2 is placed at the position PS1 of the circular table 1. The center-of-gravity distance estimation unit 21 estimates the distance L from the rotation center axis of the rotation unit (circular table 1) in FIG. 1 to the center-of-gravity position of the rotation unit based on, for example, a known technique (such as the technique described in Japanese Patent No. 6159196), from the position command of the circular table 1, the torque command of the motor 14 obtained from the current flowing through the motor 14, and the like. For example, the distance L is obtained by solving the following equation 1. In equation 1, τ m is the motor-generated torque, M is the mass of the entire circular table 1, Ir is the moment of inertia of the entire circular table 1 passing through the center of gravity (including the motor 14), v is the rotational angular velocity, g is the gravitational acceleration, τ g =MgLS β C (x+α) is the gravitational torque, τ L is the sliding load torque. τ m =(ML 2 +Ir)(dv / dt)+MgLS β C (x+α) +τ L ···(1)

[0015] The position command correction unit 20 changes the acceleration upper limit A lim of the loading unit 4 as shown in FIG. 5 according to the distance L estimated by the center-of-gravity distance estimation unit 21, and outputs the corrected position command to the motor control unit 17 of the loading unit 4. The horizontal axis in FIG. 5 is the estimated distance L, and the vertical axis is the acceleration upper limit A lim of the loading unit 4. Also, in FIG. 5, An is the reference acceleration upper limit. Usually, the reference acceleration upper limit An is the upper limit of the acceleration that can be tolerated in the loading unit 4 when the imposition range E is the reference value En and the clamping by the clamp mechanism 15 is completely completed.

[0016] When the distance L is 0 (the center of gravity of the circular table is on the rotation center axis of the rotation unit), no torque is generated due to inertial force. Therefore, when L = 0 and E = En, the acceleration upper limit A lim of the loading unit 4 is the reference acceleration upper limit A nOn the other hand, when the distance L is greater than 0, torque due to inertial force is generated. This torque increases in proportion to the distance L. Therefore, when L > 0, the acceleration upper limit A lim is limited with a downward slope from the upper right shoulder.

[0017] However, the acceleration upper limit A lim of the loading unit 4 cannot be zero. Therefore, as shown in FIG. 5, a lower limit value A min of the acceleration upper limit may be provided. Note that the acceleration upper limit A lim needs to be lowered so that the circular table 1 after positioning enters the imposition range E. For this reason, when an imposition range E n less than E n is set with respect to the normal reference imposition range E, the acceleration upper limit A lim may be determined as in the following formula (2). A lim = MAX((-k 1 L + A n ) E / E n , A min ) ···(2)

[0018] Here, MAX(A, B) is a function that takes the larger value of A and B. k 1 > 0 is a constant that determines the rate of change of A lim with respect to the distance L, and k 1 is set so that the circular table 1 enters the imposition range E n according to the distance L and the acceleration of the loading unit 4. When the reference imposition range E n is set, the acceleration upper limit A lim changes as shown by the solid line in FIG. 5. Also, when an imposition range E smaller than the reference imposition range E n is set, the acceleration upper limit A n is decreased by the part that multiplies E / E lim on the right side of formula (1), so the acceleration upper limit A limIt changes as shown by the dashed line in FIG. 5, and the circular table 1 can be maintained within the imposition range E. Therefore, when the loading unit 4 accelerates after the circular table 1 is indexed, as shown in FIG. 4, after the angular velocity (first stage) of the circular table 1 becomes 0, the clamp command (third stage) is turned on, and the position command correction unit 20 outputs a position command corrected so that the loading unit acceleration (fifth stage) becomes lower than normal. As a result, the torque due to the inertial force generated before the clamp of the circular table 1 becomes smaller, and the angle by which the circular table 1 is displaced from the target indexing position becomes smaller. For this reason, the DIFF (second stage) of the circular table 1 is within the range of the imposition range E at the time of clamp completion. Also, after the clamp is completed, the circular table 1 is fixed by the clamp torque, and since there is no need to lower the acceleration of the loading unit 4, it operates at normal acceleration.

[0019] Also, when it is known that there is a large distance L such that the rotation unit DIFF at the time of clamping cannot be made 0 only by reducing the acceleration of the loading unit 4, a threshold value may be set for the distance L, and if this is exceeded, the acceleration upper limit may not be lowered, and the loading unit 4 may be accelerated after the clamp is completed. By doing so, it is possible to avoid lowering the acceleration and making the operation time extremely long.

[0020] In the second embodiment, the position vector p from the rotation center axis of the rotation unit to the center of gravity position 1 and the unit vector p in the moving direction of the loading unit 4 2A method for reducing the acceleration of the loading unit 4 according to the magnitude of the cross product will be described. Consider a state where the workpiece 2 is placed at the position PS1 of the circular table 1 in FIG. 1 and the circular table 1 rotates 90 degrees clockwise, and the workpiece 2 moves to the position PS2. At this time, even if the loading unit 4 accelerates or decelerates in the right direction of the paper surface, no torque is generated due to inertial force. However, in the first embodiment, the acceleration of the loading unit 4 is reduced according to the distance L from the rotation center axis of the rotating unit to the center of gravity position of the rotating unit. Therefore, in the first embodiment, there is a problem that the acceleration upper limit decreases even when the workpiece 2 is at the position PS2. On the other hand, in the control system of the second embodiment shown in FIG. 6, the functions of the center of gravity position estimation unit 23 and the position command correction unit 22 are different from those of the control system of the first embodiment shown in FIG. 3.

[0021] The center of gravity position estimation unit 23 estimates the position vector p from the center of the rotation axis of the circular table 1 to the center of gravity position of the circular table 1 by a known technique (for example, Japanese Patent No. 6159196). 1 The position command correction unit 22 calculates the unit vector p in the moving direction of the loading unit 4, 2 and obtains the cross product of the unit vector p 2 and the position vector p from the center of gravity position estimated by the center of gravity position estimation unit 23 to the center of gravity position. 1 Furthermore, as shown in FIG. 7, the position command correction unit 22 changes the acceleration upper limit A lim of the loading unit 4 according to the magnitude L' of the obtained cross product, and outputs the corrected position command to the motor control unit 17 of the loading unit 4. FIG. 7 is a graph in which the horizontal axis of FIG. 5 is replaced with the magnitude L' of the cross product from the distance L, and the rest is the same as FIG. 5. Therefore, FIG. 7 shows the acceleration upper limit A lim with respect to the magnitude L' of the cross product and the imposition range E. The acceleration upper limit A lim in FIG. 7 may be determined as in the following formula (3) by replacing the distance L in formula (2) with the magnitude L' as in the first embodiment. A lim = MAX((-k 1 L'+ A n ) E / E n , A min ) ···(3)

[0022] Therefore, when the workpiece 2 is loaded at the position PS2, the position vector p from the center of gravity position 1 and the unit vector p in the moving direction of the loading unit 4 2 are in opposite directions and the included angle is 180 degrees, so the cross product is 0. Therefore, in this case, no torque is generated by the inertial force, and thus the loading unit 4 is not subject to the acceleration limit of the loading unit 4 due to the distance L and operates within the range of the acceleration limit regarding the imposition range E.

[0023] In addition, in the first and second embodiments, the unit to be loaded is described as the circular table 1 and the loading unit 4 as the translation unit for loading the circular table 1. However, the above-described technology is also applicable to other structures. For example, the unit to be loaded is not limited to the circular table and can also be implemented in a mechanical structure having other rotating units such as a trunnion unit. Similarly, the position vector p from the center of rotation of the circular table 1 to the center of gravity position of the rotating unit 1 is estimated, and by reducing the acceleration of the loading unit based on the formula (3), the torque due to the inertial force is reduced. Therefore, since the angle by which the rotating unit is displaced from the target indexing position becomes smaller, it falls within the range of the imposition range E at the completion of clamping.

[0024] In Example 3, both the loading unit and the unit to be loaded are translational units, which will be described below. FIG. 8 is a schematic view of the translational mechanism, which is the control target in Example 3, as seen from above. In FIG. 8, the translational unit 5 is a translational unit for fixing a workpiece and translates in the left - right direction. This translational unit 5 is the unit to be loaded. The loading unit 6 loads the translational unit 5 and also translates in the left - right direction, just like the translational unit 5. Also, in the example of FIG. 8, the translational unit 5 is the leading unit that is positioned earlier than the loading unit 6, and the loading unit 6 is the trailing unit that is positioned after the translational unit 5. In such a configuration, when the loading unit 6 accelerates after the translational unit 5, which is the unit to be loaded, is positioned and clamped, the translational unit 5 may be greatly displaced from the target calculated position due to inertial force and then clamped.

[0025] In the control system of Example 3 shown in FIG. 9, compared with the control system of Example 1 shown in FIG. 3, the function of the position command correction unit 24 is different. The position command correction unit 24 changes the upper acceleration limit A of the loading unit 6 as shown in FIG. 10 according to the imposition range E, and outputs the corrected position command to the motor control unit 17 of the loading unit 6. FIG. 10 is a graph in which the horizontal axis of FIG. 5 is replaced by the imposition range E. E is the lower limit value of the imposition range E, and other variables are the same as those in FIG. 5, representing the upper acceleration limit A with respect to the imposition range E. Similar to Example 1, since the upper acceleration limit A needs to be lowered so that the translational unit 5 after positioning enters the imposition range E, the upper acceleration limit A may be determined as in the following formula (4). lim and outputs the corrected position command to the motor control unit 17 of the loading unit 6. FIG. 10 is a graph in which the horizontal axis of FIG. 5 is replaced by the imposition range E. E min is the lower limit value of the imposition range E, and the other variables are the same as those in FIG. 5, representing the upper acceleration limit A with respect to the imposition range E lim . Similar to Example 1, since the upper acceleration limit A lim needs to be lowered so that the translational unit 5 after positioning enters the imposition range E, the upper acceleration limit A lim may be determined as in the following formula (4). A lim =A n E / E n ···(4)

[0026] Thus, the upper acceleration limit A of the loading unit 6 is adjusted according to the imposition range E between when the clamp command of the translational unit 5 is turned on and when the clamping torque works. limBy restricting this, the distance by which the translation unit 5 is displaced from the target calculated position due to inertial force becomes smaller, and it falls within the range of the imposition range E when clamping is completed.

[0027] In the fourth embodiment, the case where the loading unit is a rotating unit and the loaded unit is a translation unit will be described. FIG. 11 is a schematic plan view of the mechanism to be controlled in the fourth embodiment. In FIG. 11, the rotating unit 9 loads the translation unit 7 and rotates clockwise or counterclockwise. The translation unit 7 is a mechanism that moves in the diametrical direction of the rotating unit 9 for positioning. The translation unit 7 moves in the vertical direction of the paper surface at the position PS1. Also, when the rotating unit 9 rotates 90 degrees clockwise and the translation unit 7 moves from the position PS1 to the position PS2, the translation unit 7 moves in the left - right direction of the paper surface. The fourth embodiment corresponds to, for example, a U - axis machining function for radially positioning a tool attached to the machining center spindle. In the fourth embodiment, the translation unit 7, which is the loaded unit, is a preceding unit that is positioned before the rotating unit 9, which is the loading unit, and the rotating unit 9 is a subsequent unit.

[0028] In such a configuration, after the translation unit 7, which is the loaded unit, is positioned and clamped, the rotating unit 9, which is the loading unit, accelerates. At this time, if the center of gravity of the translation unit 7 is away from the rotation center axis of the rotating unit 9, centrifugal force acts on the translation unit 7, and it may be greatly displaced from the target calculated position and clamped. For such a configuration, by applying the method of the first embodiment, the distance of displacement during clamping can be shortened. That is, the center - of - gravity distance estimation unit 21 estimates the distance L from the rotation center axis of the rotating unit 9 to the center of gravity of the translation unit 7 by a known technique. The position command correction unit 20, according to the distance L estimated by the center - of - gravity distance estimation unit 21 and the imposition range E, as shown in Equation (2) and FIG. 5, sets the upper acceleration limit A of the rotating unit 9 limChange it and output the corrected position command to the motor control unit 17 of the rotation unit 9. Therefore, when the rotation unit 9, which is the loading unit, accelerates after the translation unit 7 is positioned and clamped, regardless of the center of gravity of the translation unit 7, the centrifugal force acting on the translation unit 7 becomes small, and it falls within the imposition range E at the completion of clamping after positioning.

[0029] Next, Example 5 will be described. FIG. 12 is a schematic diagram of the mechanism to be controlled in Example 5. In FIG. 12, the circular table 51 is an inclined rotation unit for fixing a workpiece, and rotates clockwise or counterclockwise about the one-dot chain line as the rotation center axis. The workpiece 52 is fixed to the circular table 51, and the workpiece position also changes when the circular table 51 rotates clockwise or counterclockwise. The loading unit 54 loads the circular table 51 and moves translationally in the direction of the arrow ab in FIG. 12. In Example 5, after the positioning of the circular table 51 (the unit to be loaded), the positioning of the loading unit 54 is performed. Therefore, in Example 5, the circular table 51 becomes the preceding unit, and the loading unit 54 becomes the subsequent unit. When the loading unit 54 accelerates in the direction of the arrow a in FIG. 12 with the workpiece 52 fixed at the position PS2, similar to the circular table in Example 1, a torque is generated to rotate the circular table 51 due to the inertial force, and there is a possibility that it will be outside the imposition range E at the completion of clamping after positioning. On the other hand, consider a state where the workpiece 52 is fixed so that the center of gravity of the circular table 51 is included in a plane parallel to the moving direction of the translation unit and including the rotation center axis of the circular table 51. For example, in FIG. 12, this state is achieved when the workpiece 52 is fixed at the position PS1. When the loading unit 54 accelerates in the direction of the arrow a in this state, although the inertial force acts on the circular table 51, no torque is generated to rotate the circular table 51, so the circular table 51 is not displaced.

[0030] When the method of Example 2 is applied to the state where the workpiece 52 is fixed at the position PS1, although the circular table 51 is not displaced, the position vector p from the rotation center axis to the center of gravity position of the circular table 51 1 and the unit vector p in the moving direction 2The magnitude L’ of the cross product is not zero, and there is a problem that the acceleration upper limit A is reduced according to Equation (3). In contrast, in the control system of Embodiment 5 shown in FIG. 13, the function of the position command correction unit 25 is different from that of the control system of Embodiment 2 shown in FIG. 6. lim The position command correction unit 25 calculates the unit vector p in the moving direction of the loading unit 54.

[0031] The position command correction unit 25 calculates the unit vector p in the moving direction of the loading unit 54. 2 Then, the position command correction unit 25 calculates a plane P that is parallel to the unit vector p2 and includes the rotation center axis of the unit to be loaded 51. Further, based on the center of gravity position and the plane P, the distance L’’ between the center of gravity position and the plane P is calculated. The position command correction unit 25 changes the acceleration upper limit A of the loading unit 54 according to the distance L’’, as shown in FIG. 14, and outputs the corrected position command to the motor control unit 17 of the loading unit 54. FIG. 14 is a graph in which the distance L on the horizontal axis of FIG. 5 is replaced with the distance L’’, and the rest is the same as FIG. 5. FIG. 5 shows the acceleration upper limit A with respect to the distance L’’ and the imposition range E. lim The acceleration upper limit A in FIG. 14 may be determined as in the following Equation (5) by replacing the distance L in Equation (2) with the distance L’’ as in Embodiment 1. lim The acceleration upper limit A in FIG. 14 lim The acceleration upper limit A in FIG. 14 may be determined as in the following Equation (5) by replacing the distance L in Equation (2) with the distance L’’, as in Embodiment 1. A lim = MAX((-k 1 L’’ + A n )E / E n , A min ) ···(5)

[0032] Here, when the workpiece 52 is fixed at the position PS1, the center of gravity of the circular table 51 is included in the plane P, and the distance L’’ of the position vector p from the plane P to the center of gravity position is zero. Therefore, in this case, it is possible to operate considering only the imposition range E without being subject to the acceleration limit of the loading unit 54 due to the magnitude L’ of the cross product in a state where no torque is generated by the inertial force. 1 Here, when the workpiece 52 is fixed at the position PS1, the center of gravity of the circular table 51 is included in the plane P, and the distance L’’ of the position vector p from the plane P to the center of gravity position is zero. Therefore, in this case, it is possible to operate considering only the imposition range E without being subject to the acceleration limit of the loading unit 54 due to the magnitude L’ of the cross product in a state where no torque is generated by the inertial force.

[0033] Next, Example 6 will be described. In Example 6, depending on the structure and positional relationship between the loading unit and the unit to be loaded, it is determined whether it is necessary to limit the acceleration upper limit. This will be described below.

[0034] In the configuration of the circular table as described in Example 1, consider the case where the rotation center axis of the circular table 61 on which the workpiece 62 is loaded as shown in FIG. 15 and the translation direction of the loading unit 64 are parallel. In such a case, even if the loading unit 64 accelerates or decelerates, no torque due to inertial force is generated on the circular table 61 of the unit to be loaded, so the circular table 61 is not displaced from the target calculated position. However, when the block diagram of FIG. 6 described in Example 2 is applied to the control of FIG. 15, the acceleration is decreased according to the magnitude L' of the cross product, so although no torque due to inertial force is generated, the acceleration upper limit A lim is decreased according to Equation (3). Also, when the block diagram of FIG. 13 described in Example 5 is applied to the control of FIG. 15, the unit vector p 2 in the moving direction of the loading unit and the rotation center axis of the loading unit are parallel and it becomes a straight line instead of a plane, but the position vector p 1 from the obtained straight line to the center of gravity position, the distance L'' between the obtained point and the straight line is equal to the distance L, and similarly, since the acceleration is decreased according to the distance L'', although no torque due to inertial force is generated, the acceleration upper limit A lim is decreased according to Equation (5).

[0035] On the other hand, in the control system of Example 6 shown in FIG. 16, compared with the control system of Example 5 shown in FIG. 13, a limit necessity determination unit 26 is added, and accordingly, the function of the position command correction unit 27 is different.

[0036] The restriction necessity determination unit 26 receives information on the moving directions and current operating directions of the loading unit and the loaded unit respectively from a higher-level control device (not shown), and determines whether the loading unit or the loaded unit is displaced during unit operation due to inertial force, centrifugal force, or reaction force. When the restriction necessity determination unit 26 determines that there is no displacement, it outputs a signal indicating that acceleration restriction is unnecessary, and when it determines that there is displacement, it outputs a signal indicating that acceleration restriction is necessary. The position command correction unit 27 receives the signal of whether acceleration restriction is necessary output by the restriction necessity determination unit 26. When acceleration restriction is unnecessary, it does not correct the position command, and when acceleration restriction is necessary, it corrects the position command to lower the acceleration as described in Embodiment 5 etc.

[0037] Note that the restriction necessity determination unit 26 determines that acceleration restriction of the loading unit is unnecessary in the case of Table 1 below, and determines that acceleration restriction of the loaded unit is unnecessary in the case of Table 2 below. Note that the acceleration restriction of the loading unit is applied when the loading unit is the subsequent unit and the loaded unit is the preceding unit. That is, when the loaded unit is positioned, then the loading unit is positioned, and further, when a clamp mechanism is provided on the loaded unit, the acceleration restriction of the loading unit is applied. Also, the acceleration restriction of the loaded unit is applied when the loaded unit is the subsequent unit and the loading unit is the preceding unit. That is, when the loading unit is positioned, then the loaded unit is positioned, and further, when a clamp mechanism is provided on the loading unit, the acceleration restriction of the loaded unit is applied.

[0038]

Table 1

Table 2

[0039] FIG. 17 shows a schematic diagram of each condition in Table 1 where the restriction necessity determination unit 26 determines that the acceleration restriction of the loaded unit is unnecessary, and FIG. 18 shows a schematic diagram of each condition in Table 2 where the restriction necessity determination unit 26 determines that the acceleration restriction of the unit to be loaded is unnecessary. In FIGS. 17 and 18, the arrow represents the moving direction of the translational unit, and the dashed-dotted line represents the rotation center axis of the rotating unit.

[0040] As shown in Table 1 and FIG. 17, in the case of condition (1), even when the loaded unit accelerates or decelerates, no torque due to inertial force is generated in the unit to be loaded and the unit to be loaded is not displaced. Therefore, the restriction necessity determination unit 26 determines that the acceleration restriction of the loaded unit is unnecessary. In the case of condition (3), even when the loaded unit accelerates or decelerates, the unit to be loaded is not displaced due to inertial force. Therefore, the restriction necessity determination unit 26 determines that the acceleration restriction of the loaded unit is unnecessary. In the cases of conditions (4) and (5), even when the loaded unit accelerates or decelerates, the unit to be loaded is not displaced due to centrifugal force. Therefore, the restriction necessity determination unit 26 determines that the acceleration restriction of the loaded unit is unnecessary.

[0041] As shown in Table 2 and FIG. 18, in the case of condition (6), even when the unit to be loaded accelerates or decelerates, the loaded unit is not displaced. Therefore, the restriction necessity determination unit 26 determines that the acceleration restriction of the unit to be loaded is unnecessary. In the case of condition (7), even when the unit to be loaded accelerates or decelerates, no torque is generated to rotate the loaded unit due to the reaction force and the loaded unit is not displaced. Therefore, the restriction necessity determination unit 26 determines that the acceleration restriction of the unit to be loaded is unnecessary. In the case of condition (8), even when the unit to be loaded accelerates or decelerates, the loaded unit is not displaced due to inertial force. Therefore, the restriction necessity determination unit 26 determines that the acceleration restriction of the unit to be loaded is unnecessary. In the case of condition (9), even when the unit to be loaded accelerates or decelerates, no torque is generated to rotate the loaded unit due to the reaction force and the loaded unit is not displaced. Therefore, the restriction necessity determination unit 26 determines that the acceleration restriction of the unit to be loaded is unnecessary. In the case of the circular table 61 shown in FIG. 15, the restriction necessity determination unit 26 corresponds to condition (1) or condition (6) and determines that the acceleration restriction is unnecessary. Therefore, the acceleration upper limit A lim is not restricted.

[0042] Thus, in the sixth embodiment, when the other unit is not shifted due to the acceleration or deceleration of one unit, the necessity determination unit 26 determines that acceleration limitation is unnecessary, so unnecessary acceleration limitation can be avoided.

[0043] In addition, due to the secular change of the clamp mechanism, there may be a delay from when a clamp completion signal or the like rises until the clamp torque rises. If the acceleration is immediately returned to normal after clamp completion, torque due to inertial force is generated, and it is conceivable that the loaded unit is largely shifted from the target calculation position and goes outside the imposition range E at the time of clamp completion. Therefore, a variable timer may be provided between clamp completion and when the acceleration of the loaded unit returns to normal.

[0044] Also, when the user determines that acceleration limitation is unnecessary, the upper control device may be provided with a function to always disable acceleration limitation.

Explanation of Reference Numerals

[0045] 1, 51, 61 circular table, 2, 52, 62 workpiece, 4, 6, 54, 64 loading unit, 5, 7 translation unit, 9 rotation unit, 11 position command generation unit, 12, 16 encoder, 13, 17 motor control unit, 14, 18 motor, 15, 30 clamp mechanism, 19 machine control unit, 20, 22, 24, 25, 27 position command correction unit, 21, 23 center-of-gravity distance estimation unit, 26 necessity determination unit for limitation, 50 control device.

Claims

1. A first motor for driving a loading unit, a second motor for driving a loaded unit loaded on the loading unit, a clamping mechanism provided on one of the loading unit and the loaded unit, a control device for controlling the driving of the first motor, the second motor, and the clamping mechanism, and comprising, after the positioning of a preceding unit, which is one of the loading unit and the loaded unit, is completed, the control device switches the state of the clamping mechanism provided on the preceding unit from an unclamped state to a clamped state, when the control device positions a subsequent unit, which is the other of the loading unit and the loaded unit, during the state switching period of the clamping mechanism, the control device lowers the upper limit of the acceleration of the subsequent unit during the state switching period below the upper limit of the acceleration during normal times, A control system for a machine tool, characterized in that.

2. A control system for a machine tool according to Claim 1, wherein the loaded unit is a translational unit that performs translational motion or a rotational unit that performs rotational motion, and the loading unit is a translational unit that performs translational motion or a rotational unit that performs rotational motion, A control system for a machine tool, characterized in that.

3. A control system for a machine tool according to Claim 1, wherein the state switching period of the clamping mechanism is a period from the rise of the clamping command to the clamping mechanism to ON until the clamping by the clamping mechanism is completed, a control system for a machine tool, characterized in that.

4. A control system for a machine tool according to Claim 1, wherein the loaded unit is a rotational unit, and the control device lowers the upper limit of the acceleration of the subsequent unit during the state switching period as the distance from the rotation center axis of the loaded unit to the center of gravity of the loaded unit is larger, A control system for a machine tool, characterized in that.

5. A control system for a machine tool according to Claim 4, wherein the control device, defines a function that returns the maximum value among a plurality of arguments as MAX(), Let k be a positive constant １ and defines the distance from the rotation center axis of the loaded unit to the center of gravity of the loaded unit as L, Let A be the upper limit of acceleration that serves as the standard for the subsequent unit ｎ and Let the imposition range that serves as the standard for the unit to be loaded be E ｎ and defines the actual imposition range of the loaded unit as E, Let the lower limit value of the acceleration of the subsequent unit be A ｍｉｎ when The acceleration upper limit A of the subsequent unit during the state switching period ｌｉｍ is A ｌｉｍ = MAX((-k １ L + A ｎ )E / E ｎ , A ｍｉｎ ) and calculates by, a control system for a machine tool, characterized in that.

6. A control system for a machine tool according to Claim 1, The loaded unit is a rotating unit, The control device, calculates the cross product of the position vector from the rotation center axis of the loaded unit to the center of gravity of the loaded unit and the unit vector in the moving direction of the loading unit, and the larger the cross product, the lower the upper limit of the acceleration of the subsequent unit during the state switching period. A control system for a machine tool, characterized in that.

7. A control system for a machine tool according to claim 6, wherein the control device, defines a function that returns the maximum value among a plurality of arguments as MAX(), Let \(k\) be a positive constant １ and defines the magnitude of the cross product as L', Let A be the upper limit of acceleration that serves as a reference for the subsequent unit ｎ and Let the imposition range that serves as the standard for the unit to be loaded be E ｎ and defines the actual imposition range of the loaded unit as E, When the lower limit value of the acceleration of the subsequent unit is A ｍｉｎ then The acceleration upper limit A of the subsequent unit during the state switching period ｌｉｍ is A ｌｉｍ = MAX((-k １ L'+A ｎ )E / E ｎ , A ｍｉｎ ) and calculates by, a control system for a machine tool, characterized in that.

8. A control system for a machine tool according to claim 1, wherein both the loading unit and the loaded unit are translational units, and the control device, defines a function that returns the maximum value among a plurality of arguments as MAX(), Let k be a positive constant １ and Let A be the upper limit of acceleration that serves as the standard for the subsequent unit ｎ and Let the imposition range that serves as the standard for the unit to be loaded be E ｎ and defines the actual imposition range of the loaded unit as E, Let the lower limit value of the acceleration of the subsequent unit be A ｍｉｎ When this is the case The acceleration upper limit A of the subsequent unit during the state switching period ｌｉｍ is A ｌｉｍ = A ｎ E / E ｎ and calculates by, a control system for a machine tool according to claim 1, characterized in that.

9. A control system for a machine tool according to claim 1, wherein the loading unit is a rotating unit, the loaded unit is a translational unit, and the control device, defines a function that returns the maximum value among a plurality of arguments as MAX(), Let k be a positive constant １ and defines the distance from the rotation center axis of the loading unit to the center of gravity of the loading unit as L, Let A be the upper limit of acceleration that serves as a reference for the subsequent unit ｎ and Let the imposition range that serves as the standard for the unit to be loaded be E ｎ and defines the actual imposition range of the loaded unit as E, When the lower limit value of the acceleration of the subsequent unit is A ｍｉｎ then The acceleration upper limit A of the subsequent unit during the state switching period ｌｉｍ is A ｌｉｍ = MAX((-k １ L + A ｎ )E / E ｎ , A ｍｉｎ ) and calculates by, a control system for a machine tool, characterized in that.

10. A control system for a machine tool according to claim 1, wherein the loaded unit is a rotating unit, and the control device, defines a plane P that is parallel to the unit vector in the moving direction of the loading unit and includes the rotation center axis of the loaded unit, defines the distance between the plane P and the center of gravity of the loaded unit as L'', defines a function that returns the maximum value among a plurality of arguments as MAX(), Let \(k\) be a positive constant １ and Let A be the upper limit of acceleration that serves as a reference for the subsequent unit ｎ and Let the imposition range serving as a reference for the unit to be loaded be E ｎ and defines the actual imposition range of the loaded unit as E, Let the lower limit value of the acceleration of the subsequent unit be A ｍｉｎ When this is the case The acceleration upper limit A of the subsequent unit during the state switching period ｌｉｍ is A ｌｉｍ = MAX((-k １ L'' + A ｎ )E / E ｎ , A ｍｉｎ ) and calculates by, a control system for a machine tool, characterized in that.

11. A control system for a machine tool according to any one of claims 1 to 10, wherein the control device, When the unit to be loaded is the preceding unit and the loading unit is the subsequent unit, and when the loading unit and the unit to be loaded each satisfy the conditions shown in Table 1, the acceleration limit of the loading unit is not set. When the unit to be loaded is the subsequent unit and the loading unit is the preceding unit, and when the loading unit and the unit to be loaded each satisfy the conditions shown in Table 2, the acceleration limit of the unit to be loaded is not set. A control system for a machine tool, characterized by the above. 【Table 1】 【Table 2】

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