JP2006154942A - Servo motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a servo motor controller capable of correcting a shift quantity of relative rotation positions at the stopping of both motors. <P>SOLUTION: This servo motor controller has a means for correcting a shift when two servo motors for operating and controlling a machine object are driven, and power supply to both the motors is abruptly interrupted and when the shift between rotation positions at the stopping of both the motors caused by a brake difference of brake mechanisms of both the motors is generated. The controller comprises a detection means for detecting the rotation positions at the stopping of both the motors when power supply to both the motors is re-started, a shift quantity calculating means for calculating the relative rotation position at stopping as the difference between the rotation positions at the stopping of both the motors based on the detected rotation positions of both the motors and for calculating the shift quantity between the relative rotation position at stopping and a predetermined initial set relative rotation position, and a correction driving means for automatically rotating and driving either of the motors so as to make the shift quantity zero. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a servo motor control apparatus for controlling the operation of one workpiece using a plurality of servo motors.

  Conventionally, when one workpiece is controlled by a plurality of servo motors, position commands of a plurality of servo motors are corrected in order to reduce the distortion of the workpiece when the motor is in a controlled state. A method for synchronous control has been proposed. (For example, refer to Patent Document 1).

  When the operation of one workpiece is controlled by a plurality of servomotors, if the supply of power to the servomotor is suddenly interrupted due to a power failure or the like, the servomotor enters an uncontrolled state and stops. The rotation position at this time is hereinafter referred to as a stop rotation position. In this case, in order to stop according to the braking performance of the brake mechanism of the servo motor, each motor has a different rotational distance from the non-control state to the stop, so that the workpiece is twisted.

  When torsion occurs, if the workpiece has high rigidity, a load due to torsion of the workpiece is applied to any of a plurality of motors, so the servo motor controller can accurately control the operation of the motor. Disappear. Moreover, the motor speed reducer may be damaged. If the workpiece has low rigidity, there is a possibility that the workpiece has a large torsion. Therefore, if the servo motor drive is resumed while the torsion is occurring, the machining result of the workpiece will be reduced. It will have an adverse effect.

  A method of correcting the deviation that occurs between the rotation positions of the plurality of servo motors that cause the twist will be described with reference to FIGS.

  FIG. 4 is a diagram showing a general configuration of a welding robot that performs welding by controlling the operation of one workpiece by two servo motors. In the figure, a workpiece 3 is attached to a first positioner 1 and a second positioner 2, and a first servo motor M1 and a second servo motor M2 are incorporated in both the positioners 1 and 2, respectively. Operation control signals SM1 and SM2 from the servo motor control device 4 are input to both the motors M1 and M2, respectively, and the rotation operation of the workpiece 3 is controlled.

  Further, the operation command signal SR is input from the teach pendant 5 to the robot control device 6, and the operation control signal SRc from the robot control device 6 is input to the manipulator 7. Thereby, the tip position of the welding torch 8 attached to the tip of the manipulator 7 is controlled, and the workpiece 3 is welded. The servo motor control device 4 may be provided in the robot control device 6 in some cases.

  FIG. 5 is a block diagram for explaining the flow of signals between the servo motor control device 4 of the prior art and the motors M1 and M2 built in the positioners 1 and 2. As shown in FIG. In the figure, electric power E is supplied from a commercial power source 9 to the servo motor control device 4. Operation control signals SM1 and SM2 are input from the servo motor control device 4 to both servo motors M1 and M2 incorporated in both positioners 1 and 2, respectively. The rotational position signals P1 and P2 of the motors M1 and M2 are fed back to the servo motor control device 4, respectively. Then, both motors M1 and M2 are synchronously controlled, and the workpiece 3 is controlled in operation.

  FIG. 6 is a flowchart for explaining a method of correcting a shift in rotational position when both motors are stopped when power supply to both motors is suddenly interrupted. FIG. 7 is a diagram showing the rotational positions of the two motors when correcting the deviation of the rotational positions when both the motors of the prior art are stopped.

  As shown in FIG. 7 (A), in order to perform synchronous control of both motors M1 and M2 to carry out the work 3 or the work of the workpiece 3, rotational positions P1a and P2a serving as references for both motors M1 and M2 are used. Are preset, and these initially set rotational positions P1a and P2a are stored in the servo motor control device 4. In addition, a task program for returning the rotational positions of both the motors M1 and M2 to the initial rotational positions P1a and P2a is created in advance.

  As shown in FIG. 7A, the workpiece 3 is twisted while the workpiece 3 is attached to both the motors M1 and M2 without being twisted and the motors M1 and M2 are synchronously controlled. Maintains no state.

  However, in step S1 of FIG. 6, a power failure or the like occurs while both the motors M1 and M2 are driven, and the supply of power to the servo motor control device 4 is suddenly cut off.

  In step S2, the operation control signals SM1 and SM2 to both the motors M1 and M2 are stopped, and both the motors M1 and M2 are stopped according to the braking performance of the respective brake mechanisms. As a result, as shown in FIG. 7B, the first servo motor M1 moves from the initial setting rotational position P1a to the stopping rotational position P1b and stops, and the second servo motor starts from the initial setting rotational position P2a. It moves to the rotation position P2b at the time of stop and stops. Since the rotational distances until the motors M1 and M2 are stopped are different, the workpiece 3 is twisted.

Thereafter, after the supply of power to the servo motor control device 4 is resumed in Step 3 of FIG. 6, in Step S4, the rotation positions P1b and P2b of both the motors M1 and M2 are changed to the initial rotation positions P1a and P1b. The task program to be returned to P2a is started, and as shown in FIG. 7C, the first servo motor M1 moves from the stop rotation position P1b to the initial set rotation position P1a and stops, and the second servo motor , It moves from the stop rotation position P2b to the initial set rotation position P2a and stops. As a result, both the motors M1 and M2 return to the initial set rotational positions P1a and P2a, respectively, so that the torsion of the workpiece 3 is corrected.
Japanese Patent Laid-Open No. 11-305839

  As described above, the method of correcting the deviation between the rotational positions P1b and P2b of the motors M1 and M2 according to the prior art uses the rotational positions P1b and P2b of the motors M1 and M2 when stopped, and the initial rotational positions P1a and P2b. The task program for returning to P2a is activated. In this case, when the stop rotation positions P1b and P2b of both the motors M1 and M2 are far from the initial setting rotation positions P1a and P2a, the stop rotation positions P1b and P2b are changed to the initial setting rotation positions P1a and P2a. It takes time to return. In addition, since the twisted state is continued for a long time, a load is applied to the workpiece during that time.

  An object of the present invention is to provide a servo motor control device capable of correcting a shift amount of a relative rotational position when both motors are stopped in a short time.

In order to achieve the above object, the first invention provides:
When the power supply to both motors is suddenly interrupted while the two servo motors that control the work are being driven, and the rotational position of both motors is shifted due to the braking difference between the brake mechanisms of both motors. In the servo motor control device having means for correcting this deviation,
Detection means for detecting the rotational position when both motors are stopped when the supply of power to both motors is resumed;
Based on the detected rotation position of both motors, a relative rotation position at the time of stop, which is a difference between the rotation positions of both motors when stopped, is calculated, and this relative rotation position at the time of stop and a predetermined initial set relative rotation position are calculated. A deviation amount calculating means for calculating a deviation amount from
A servo motor control device comprising correction drive means for automatically rotating one or both of the two motors so that the deviation amount becomes zero.

The second invention is
The servo motor control apparatus according to the first aspect of the present invention, further comprising: a determination unit that shifts to the correction drive unit only when the deviation amount exceeds a predetermined threshold value.

The third invention is
The servo motor control device according to the first aspect, wherein the initially set relative rotational position is predetermined according to the type of workpiece.

  In the servo motor control devices according to the first and third aspects of the present invention, the power supply to both motors is suddenly cut off while the two servo motors for controlling the operation of the workpiece are being driven, and the braking mechanisms of both motors are braked. In a servo motor control device having means for correcting this deviation when a difference occurs in the rotational position when both motors are stopped due to the difference, when the supply of power to both motors is resumed, both motors rotate when stopped. Based on the detection means for detecting the position and the detected rotational position of both motors, the relative rotational position at the time of stopping, which is the difference between the rotational positions when both motors are stopped, is calculated and determined as the relative rotational position when stopped. A deviation amount calculating means for calculating a deviation amount from the initially set relative rotational position, and a correction driving means for automatically rotating either one or both of the motors so that the deviation amount becomes zero. There.

  As a result, unlike the prior art, there is no need to start a task program for returning the rotational positions P1b and P2b of both motors M1 and M2 to the initial rotational positions P1a and P2a. Even when the rotational position is far from the initial set rotational position, the rotational distance between the two motors for correcting the deviation is short, so that the deviation amount of the relative rotational position when both motors are stopped can be corrected in a short time. In addition, the torsional period during which the workpiece is loaded is significantly shortened.

  A servo motor control device according to a second aspect of the invention is the servo motor control device according to the first aspect of the invention, wherein the correction drive means is used only when the deviation amount of the relative rotational position during stop exceeds a predetermined threshold value. It is provided with discrimination means for shifting to As a result, in addition to the effects of the servo motor control device of the first invention, it is possible to improve the efficiency of the machining operation.

[Embodiment 1]
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on examples with reference to the drawings.
The block diagram for explaining the flow of signals between the servo motor control device and both motors built in both positioners is the same as the block diagram of the prior art shown in FIG. Hereinafter, processing different from the prior art of the servo motor control device of the present invention will be described in detail.

  FIG. 1 is a flow chart for explaining the operation of the servo motor control apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram showing the shift of the relative rotational position when both motors are stopped by the servo motor control apparatus of the present invention. It is a figure which shows the rotational position of both motors when correct | amending.

  As shown in FIG. 2 (A), in order to synchronously control both the motors M1 and M2 to carry out the work or the work of the workpiece 3, rotational positions P1a and P2a serving as a reference for both the motors M1 and M2. Are preset, and these initially set rotational positions P1a and P2a are stored in the servo motor control device 4.

  As shown in FIG. 2 (A), the workpiece 3 is twisted while the workpiece 3 is attached to both the motors M1 and M2 without being twisted and the motors M1 and M2 are synchronously controlled. Maintains no state.

  However, in step S1 of FIG. 1, a power failure or the like occurs while both the motors M1 and M2 are driven, and the supply of power to the servo motor control device 4 is suddenly cut off.

  In step S2, the operation control signals SM1 and SM2 to both the motors M1 and M2 are stopped, and both the motors M1 and M2 are stopped according to the braking performance of the respective brake mechanisms. As a result, as shown in FIG. 2B, the first servo motor M1 moves from the initial setting rotational position P1a to the stopping rotational position P1b and stops, and the second servo motor is moved from the initial setting rotational position P2a. It moves to the rotation position P2b at the time of stop and stops. Since the rotational distances until the motors M1 and M2 are stopped are different, the workpiece 3 is twisted.

  Thereafter, after the supply of power to the servo motor control device 4 is resumed in Step 3 of FIG. 1, the servo motor control device 4 stops the motors M1 and M2 shown in FIG. 2B in Step S4. The hourly rotation positions P1b and P2b are detected.

  In step S5, the stop relative rotational position (Pb = Pb = P2b), which is the difference between the detected rotational positions P1b and P2b of the motors M1 and M2 and the stopped rotational positions P1b and P2b of the motors M1 and M2. P1b-P2b) is calculated.

  In step S6, the amount of deviation (ΔP = Pb−Pa) between the above-mentioned relative rotational position Pb at the time of stop and a predetermined initial relative rotational position (Pa = P1a−P2a) is calculated.

  In step S7, a target rotational position (P2c = Pb + ΔP) of the second servo motor at which the deviation amount ΔP becomes zero is calculated.

  In step S8, an operation control signal for rotating to the target rotation position P2c is input to the second servo motor M2, and as shown in FIG. 2C, the second servo motor M2 is moved from the stop rotation position P2b to the target rotation position P2b. The rotational position P2c is rotationally driven to correct the shift of the relative rotational position at the time of stop. It is set in advance which of the two motors M1 or M2 is driven to rotate when correcting the shift of the relative rotational position at the time of stopping. Further, instead of rotating either one of the motors M1 or M2, both the motors M1 and M2 may be driven to rotate.

  A jig for attaching the workpiece 3 is fixed to each of the positioners 1 and 2. When the shape of the workpiece 3 attached to the fixed jig is different, the above-described initial relative rotation position Pa is determined in advance corresponding to the shape.

  By the above-described steps S1 to S8, the shift amount ΔP of the relative rotational position Pb when both the motors M1 and M2 are stopped can be corrected. As a result, unlike the prior art, there is no need to start a task program for returning the rotation positions P1b and P2b of both motors M1 and M2 to the initial rotation positions P1a and P2a, and when both motors M1 and M2 are stopped. Even when the rotational positions P1b and P2b are far from the initial set rotational positions P1a and P2a, the rotational distances of both the motors M1 and M2 for correcting the deviation are short, so that both the motors M1 and M2 are in a short time. The deviation amount ΔP of the stop relative rotational position Pb can be corrected. In addition, the torsional period during which the workpiece is loaded is significantly shortened.

[Embodiment 2]
FIG. 3 is a flowchart for explaining the operation of the servo motor control apparatus according to the second embodiment of the present invention. In the figure, steps S1 to S6 and steps 7 and 8 are the same as those in FIG. Hereinafter, step 9 indicated by a dotted line will be described.

  In step S9, it is determined whether or not the deviation amount ΔP of the stop relative rotational position Pb exceeds a predetermined threshold value T1. This threshold value T1 is set in advance depending on the material and quality of the workpiece 3. When the deviation ΔP of the stop relative rotational position Pb exceeds a predetermined threshold value T1, the routine proceeds to step 7. When the deviation amount ΔP of the stop relative rotational position Pb does not exceed the predetermined threshold value T1, the flow for correcting the deviation amount ΔP is ended.

  A threshold value that is larger than the above-described threshold value T1 is provided, and when this threshold value is exceeded, it is determined that the torsion of the workpiece 3 is abnormally large, and an abnormal signal is output to the operator. You may make it notify.

  As described above, the servo motor control apparatus according to the second embodiment of the present invention corrects the correction driving means only when the deviation amount ΔP of the stop relative rotational position Pb exceeds the predetermined threshold value T1. Therefore, in addition to the effects of the servo motor control apparatus according to the first embodiment, it is possible to improve the efficiency of the machining operation.

  The servo motor control device of the present invention described above has been described with respect to the case where the workpiece is attached to two positioners to control the operation. However, the present invention is not limited to this case. The present invention can also be applied to, for example, a case where two servo motors are attached to two columnar support members, respectively, and a movable part is attached between these servo motors to control the operation. Further, the present invention can also be applied to the case where four servo motors are attached to four columnar support members, respectively, and a planar moving member is attached to these servo motors to control the operation.

It is a flowchart for demonstrating operation | movement of the servomotor control apparatus of Embodiment 1 of this invention. It is a figure which shows the rotational position of both motors when correct | amending the shift | offset | difference of the relative rotational position at the time of a stop of both motors by the servomotor control apparatus of this invention. It is a flowchart figure for demonstrating operation | movement of the servomotor control apparatus of Embodiment 2 of this invention. It is a figure which shows the general structure of the welding robot which performs operation control of one workpiece by two servomotors, and performs welding. It is a block diagram for demonstrating each signal flow between the servomotor control apparatus 4 of a prior art, and both motors M1 and M2 incorporated in both positioners 1 and 2. FIG. It is a flowchart explaining the method of correct | amending the shift | offset | difference of the rotation position at the time of a stop of both motors, when supply of the electric power to both motors of a prior art is interrupted | blocked suddenly. It is a figure which shows the rotation position of both motors when correct | amending the shift | offset | difference of the rotation position at the time of the stop of both motors of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st positioner 2 2nd positioner 3 Workpiece 4 Servo motor control apparatus 5 Teach pendant 6 Robot control apparatus 7 Manipulator 8 Welding torch 9 Commercial power supply E Electric power M1 1st servo motor M2 2nd servo motor P1 1st servo motor Rotational position signal P1a Predetermined set rotational position P1b of the first servo motor Rotational position P2 when the first servo motor is stopped P2 Rotational position signal P2a of the second servo motor Predetermined set rotational position P2b of the second servo motor Second servo motor stop rotation position P2c Second servo motor target rotation position Pa Set relative rotation position Pb Stop relative rotation position SM1 Operation control signal SM2 Operation control signal SR Operation command signal SRc Operation control signal T1 Threshold value ΔP Deviation of relative rotational position Pb at stop

Claims (3)

When the power supply to both motors is suddenly interrupted while the two servo motors that control the work are being driven, and the rotational position of both motors is shifted due to the braking difference between the brake mechanisms of both motors. In the servo motor control device having means for correcting this deviation,
Detection means for detecting the rotational position when both motors are stopped when the supply of power to both motors is resumed;
Based on the detected rotation position of both motors, a relative rotation position at the time of stop, which is a difference between the rotation positions of both motors when stopped, is calculated, and this relative rotation position at the time of stop and a predetermined initial set relative rotation position are calculated. A deviation amount calculating means for calculating a deviation amount from
A servo motor control device, comprising: a correction driving means for automatically rotating one or both of the two motors so that the deviation amount becomes zero.   2. The servo motor control apparatus according to claim 1, further comprising a determining unit that shifts to the correction driving unit only when the deviation amount exceeds a predetermined threshold value. 2. The servo motor control device according to claim 1, wherein the initially set relative rotational position is predetermined according to the type of workpiece.

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