Control device for an electric motor

Abstract

The present application provides a control device of an electric motor, which can quickly and effectively stop at a specific position, thereby achieving further high-speed positioning. The control device of the electric motor is used for stopping a rotating shaft rotating at a specified speed at a specific position after a stop instruction, and comprises: a first time calculation unit, which calculates a first time for stopping the rotating shaft at a target stop position without changing the rotating direction according to a current speed, the target stop position and an acceleration at the time of positioning; a second time calculation unit, which calculates a second time for stopping the rotating shaft at the target stop position by rotating the rotating shaft in the reverse direction after temporarily stopping the rotation of the rotating shaft according to the current speed, the target stop position and the acceleration at the time of positioning; a comparison unit, which compares the first time with the second time; and a directional stop control unit, which performs stop control of the electric motor in a manner of shortening the time until the rotating shaft is stopped at the target stop position based on the comparison result of the comparison unit.

Description

TECHNICAL FIELD

[0001] The present application relates to a control device of an electric motor. BACKGROUND

[0002] For example, the rotation amount, speed, torque, and the like of a servo motor of an industrial machine such as a servo motor for driving a spindle of a machine tool are subjected to drive control. In addition, a control device of a servo motor detects the position, magnetic pole position (phase (angle) of a motor magnet) of the motor using a detector, decides a voltage command value based on various feedback values from the detector, applies a voltage modulated by a pulse width modulation (PWM) method, and thereby performs drive control of the motor.

[0003] On the other hand, as a method of controlling an operation of stopping an industrial machine at a certain position, that is, a so-called homing (homing stop) operation, the following method has been put into practical use, which is a method of, for example, receiving a homing command, and executing a maximum deceleration control operation by flowing a maximum current in a motor, detecting a maximum deceleration acceleration, acquiring a state value of the fastest homing stop, and then making a command for stopping at a certain position based on the state value, and performing drive control of the motor in accordance with the command.

[0004] For example, Patent Literature 1 discloses the following: "A control method of a spindle motor for driving a disc-shaped storage medium, the control method of the spindle motor being characterized by stopping application of a forward rotation drive current and applying a reverse rotation drive current at the time of stop, and detecting a rotation speed and a rotation acceleration of the spindle motor to calculate a required stop time and a required stop rotation speed required until stop, and stopping application of the reverse rotation drive current at a time point at which the required stop time has elapsed from the time point when the required stop rotation speed is less than a prescribed value."

[0005] Patent Document 2 discloses the following: "A control device for motor stop for making each motor emergency stop in a process line equipped with a plurality of motors and a motor drive device, wherein the plurality of motors include a first motor for driving a conveyor of a continuous member and a second motor for driving a coiler of the continuous member, the motor drive device for controlling the motors, the control device characterized by having: an input portion to which each roll diameter information of the conveyor and the coiler and each rotational speed information of the motors are input in real time; a recording portion in which a rated value of each motor and an inertia of a mechanical portion connected to each motor are recorded in advance; a stop time calculation portion for calculating, for each motor, a stop time in a case where a regenerative brake is implemented at a constant torque prescribed at a current time point, based on the information input to the input portion and the information recorded in the recording portion; a torque limit value calculation portion for specifying a maximum stop time from the stop times of each motor calculated by the stop time calculation portion, and calculating, for each motor, a torque limit value for stopping the motor so as to match the specified maximum stop time; and an output portion for outputting each torque limit value calculated by the torque limit value calculation portion to the motor drive device when the output portion is input with an emergency stop instruction for making the line emergency stop, and performing a regenerative brake after torque limitation with the torque limit value."

[0006] Prior art documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 2948830

[0009] Patent Document 2: Japanese Patent Application Publication No. 2012-175808 SUMMARY

[0010] Problem to be solved by the invention

[0011] Here, in the above-described orientation control method, in order to make a quick and efficient stop at a specific position, it is provided that a maximum current is made to flow in the motor to perform a maximum deceleration control action at the same time as the orientation instruction is issued.

[0012] However, there are cases where it is difficult to make a maximum current flow in the motor to perform a maximum deceleration control action and make a high-precision stop at a specific position in this state, as a result of which the time until a stop at a specific position is made is lengthened to cause a decrease in efficiency.

[0013] Therefore, a method capable of making a quicker and more efficient stop at a specific position is strongly desired.

[0014] Solution to the problem

[0015] One embodiment of the control device of the electric motor of the present disclosure is a control device of an electric motor that makes a rotating shaft rotating at a prescribed speed stop in a targeted direction after a stop instruction, and is configured to include: a first time calculation section that calculates a first time in a case where the rotating shaft is stopped at a target stop position without changing a rotation direction, based on a current speed, the target stop position, and an acceleration at the time of positioning; a second time calculation section that calculates a second time in a case where the rotating shaft is stopped at the target stop position by rotating in a reverse direction after temporarily stopping the rotating shaft, based on the current speed, the target stop position, and the acceleration at the time of positioning; a comparison section that compares the first time and the second time; and a targeted stop control section that performs stop control of the electric motor in a manner to shorten a time until stopped at the target stop position, based on a comparison result of the comparison section.

[0016] Effects of the invention

[0017] According to one embodiment of the control device of the electric motor of the present disclosure, it is possible to make the electric motor that is issued with a targeted instruction stop quickly and efficiently at a specific position, and further make an industrial machine or the like driven by the electric motor stop quickly and efficiently at a specific position. That is, it is possible to achieve high speed of a targeted action. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 is a block diagram illustrating the control device of the electric motor of one embodiment.

[0019] Fig. 2 is a graph illustrating a relationship between a speed of the action control of the first time and time.

[0020] Fig. 3 is a graph illustrating the action control of the first time.

[0021] Fig. 4 is a graph illustrating the action control of the first time.

[0022] Fig. 5 is a graph illustrating a relationship between a speed of the action control of the second time and time.

[0023] Fig. 6 is a graph illustrating the action control of the second time.

[0024] Fig. 7 is a graph illustrating the action control of the second time.

[0025] Fig. 8 is a graph illustrating a relationship between a speed of a modified example of the action control of the first time and time.

[0026] Fig. 9 is a drawing showing a modification example of the first-time action control.

[0027] Explanation of reference numerals

[0028] 1: control system of industrial machine; 2: motor; 3: control device of motor; 4: speed detection section; 5: acceleration calculation section; 6: insufficient / excessive distance calculation section; 7: first-time calculation section; 8: second-time calculation section; 9: comparison section; 10: orientation stop control section. DETAILED DESCRIPTION

[0029] Hereinafter, the control device of the motor related to the first embodiment will be described with reference to Figs. 1 to 9 to the first embodiment will be described with reference to

[0030] The present embodiment relates to a control device of a motor, which is used, for example, to appropriately control an orientation (orientation stop) action of controlling a motor (rotary shaft of an industrial machine) for driving a spindle of a machine tool, so that the spindle position is stopped at a specific position where tool changing can be performed, and the like.

[0031] Further, the control device of the motor of the present disclosure can control an orientation action of an industrial machine equipped with a motor (rotary shaft) as long as it can, and is not limited to a machine tool, and of course, can be applied to drive control of a motor of other industrial machines such as a robot, a transfer machine, a measuring device, a test device, a press machine, an indenter, a printing machine, a die casting machine, an injection molding machine, a food machine, a packaging machine, a welding machine, a cleaning machine, a painting machine, an assembly device, a mounting machine, a woodworking machine, a sealing device, a cutting machine, and the like.

[0032] In addition, the motor can not necessarily be a servo motor.

[0033] First, as shown in Fig. 1 the control system 1 of the machine tool of the present embodiment is equipped with a control device 3 of a motor, which is used, for example, to control a motor 2 for driving a spindle (rotary shaft) of a machine tool and the like based on an instruction of a CNC (Computerized Numerical Control) of an instruction section, thereby controlling an orientation (orientation stop) action.

[0034] The control device 3 of the motor of the present embodiment is equipped with: a speed detection section 4 that detects a speed of a spindle (rotary shaft) driven by the motor 2; and an acceleration calculation section 5 that calculates an acceleration based on the speed detected by the speed detection section 4, and sets a target stop position to the control device 3 of the motor at a time point when an orientation instruction is issued.

[0035] Furthermore, the motor control device 3 of this embodiment includes: a short / excess distance calculation unit 6, which calculates the short distance and excess distance relative to the target stop position based on the current speed, the target stop position, and the acceleration during positioning when a directional command is issued; a first time calculation unit 7, which calculates a first time when the rotating shaft (main shaft) stops at the target stop position without changing its rotation direction based on the current speed, the target stop position, and the acceleration during positioning when a directional command is issued; a second time calculation unit 8, which calculates a second time when the rotating shaft is temporarily stopped and then rotated in the opposite direction to stop at the target stop position based on the current speed, the target stop position, and the acceleration during positioning; a comparison unit 9, which compares the first time and the second time; and a directional stop control unit 10, which performs motor 2 stop control by shortening the time until it stops at the target stop position based on the comparison result of the comparison unit 9.

[0036] The motor control device 3 of this embodiment is configured such that when switching from speed control to position control at a predetermined speed after issuing a directional (directional stop) command, it calculates a first time and a second time based on the current speed, the distance (angle) to the target position (command position), and the acceleration during positioning, and selects the action that minimizes the positioning time.

[0037] <First-time calculation>

[0038] Specifically, the first time calculation unit 7 of the control device 1 for the electric motor 2 in this embodiment calculates the first time as follows.

[0039] like Fig. 2 , Fig. 3 , Fig. 4 ( Fig. 1 As shown in the figure, while issuing the orientation command, the acceleration calculation unit 5 calculates the acceleration that causes the motor 2 to decelerate and stop from the position control start position based on the current speed detected by the speed detection unit 4, and the orientation stop control unit 10 performs deceleration control based on this acceleration.

[0040] The insufficient / excess distance calculation unit 6 calculates the insufficient distance and the excessive distance relative to the target stopping position when the position control starts from the starting position and then stops.

[0041] If the result obtained by the insufficient / excess distance calculation unit 6 is that the position is stopped at a distance S1 less than the target stopping position, a directional command is issued in order to correct the insufficient distance S1, and the state of speed control is switched to position control.

[0042] This shift from speed control to position control is made in the stage (time t0) where deceleration is performed at maximum capacity after the directional instruction is issued and the preset speed V0 is reached.

[0043] The directional stop control section controls the drive of the motor 2 so that the shaft of the motor 2 is stopped at the target stop position by only positive rotation after the start of the directional instruction, in the case where the result of the calculation by the insufficient / excessive distance calculation section 6 is the insufficient distance S1 with respect to the target stop position, as shown in FIG. 2.

[0044] Thus, in the case where the result of the calculation by the insufficient / excessive distance calculation section 6 is the insufficient distance S1 with respect to the target stop position, as shown in FIG. 2, the directional stop control section 10 controls the drive of the motor 2 so that the shaft of the motor 2 is stopped at the target stop position by only positive rotation after the start of the directional instruction. Fig. 2 The first time calculation section 7 calculates the first time from the issuance of the directional instruction until the stop at the target stop position at this time.

[0045] <Second time calculation>

[0046] The second time calculation section 8 of the control device 3 of the motor of the present embodiment calculates the second time as follows.

[0047] As shown in FIG. 3, Fig. 5 , Fig. 6 , Fig. 7 ( Fig. 1 ) shows that, at the same time as the issuance of the directional instruction, the acceleration calculation section 5 calculates an acceleration that causes deceleration at the maximum capacity of the motor 2 from the position control start position so as to stop, based on the current speed detected by the speed detection section 4, and the directional stop control section 10 performs deceleration control at this acceleration.

[0048] The insufficient / excessive distance calculation section 6 calculates the distance that is insufficient, the distance that is excessive, with respect to the target stop position in the case where deceleration is performed at the maximum capacity from the position control start position so as to stop like this.

[0049] In the case where the result obtained by the insufficient / excessive distance calculation section 6 is a position where the stop is at the excessive distance S1 with respect to the target stop position, the directional instruction is issued in order to correct the excessive distance S1, and the shift from the state where speed control is performed to position control is made.

[0050] Further, generally, in a case where the result of stopping at a position exceeding the distance SI from the target stop position occurs, control is performed so that the main shaft stops at the target stop position after one revolution of re-rotation. Therefore, the time from the issuance of the positioning command until stopping at the target stop position is long.

[0051] This shift from the speed control to the position control is performed at a stage (time tO) where the maximum deceleration is performed after the issuance of the orientation command and the preset speed V0 is reached.

[0052] The orientation stop control section causes the deceleration to continue at the stage (time, speed) = (tO, V0) and causes the movement to exceed the target position by the distance SO and temporarily stop. Then, the correction operation control of the acceleration and deceleration is performed after the inverse rotation by the distance SI from the stage (time, speed) = (tl, 0) when the movement by the distance SO is performed, to cause the stop at the target stop position ((time, speed) = (t2, 0)).

[0053] In a case where the result of stopping at a position exceeding the distance SI from the target stop position occurs like this, the orientation stop control section 10 controls the drive of the motor 2 so that the shaft of the motor 2 is stopped at the target stop position in a combination of the forward rotation and the inverse rotation after the issuance of the orientation command, as shown in Fig. 5 The second time calculation section 8 calculates the second time from the issuance of the orientation command until stopping at the target stop position at this time.

[0054] <Selection of stop control operation>

[0055] Next, the comparison section 9 compares the first time and the second time calculated as described above to determine which time is shorter. Then, the operation of the first time or the second time until stopping at the target stop position is selected which is shorter, and the orientation stop control section 10 performs the stop control of the motor 2 in a manner to shorten the time until stopping at the target stop position.

[0056] Thus, in the control device 3 of the motor of the present embodiment, it is possible to stop at a specific position quickly and efficiently. That is, further high speed of the orientation operation can be achieved.

[0057] The above describes one embodiment of the control device of the motor, but is not limited to the above-described embodiment and can be appropriately changed within a range not departing from the gist thereof.

[0058] For example, it is also possible to Fig. 8 , Fig. 9As shown, after the stage (time tO) of maximum deceleration and speed control to reach the speed V0 after the directional instruction is issued, after which the distance S0' is moved with maximum deceleration also by speed control and stopped ((time, speed) = (tl, 0)), in this stage, the position control is switched from the speed control, and the distance S1 that is insufficient to move according to the acceleration / deceleration is moved so as to stop at the target stop position. The time in the case where the shaft of the motor 2 is stopped at the target stop position by only the positive rotation after the directional instruction is issued like this can also be taken as the first time.

[0059] In addition, in the case where the excess distance is generated due to deceleration at the maximum capacity of the motor, it is sufficient to perform the reverse rotation action for correcting the excess distance.

Claims

1. A control device of a motor for stopping a main shaft rotating shaft at a target stop position after switching from speed control to position control at a stop instruction for stopping the main shaft rotating shaft at the target stop position, the switching from the speed control to the position control is performed in a stage where deceleration is performed at a maximum capacity of the motor and a predetermined speed is reached after the stop instruction is issued, the control device of the motor comprises: an acceleration calculation section that calculates an acceleration at the time of deceleration at the maximum capacity of the motor in the speed control, and an acceleration at the time of acceleration and deceleration or deceleration at the maximum capacity of the motor from a start position of the position control to stop; a first time calculation section that calculates a first time in a case where the main shaft rotating shaft is stopped at the target stop position without changing a rotation direction, based on the predetermined speed, the target stop position, a start position of the position control, and the acceleration calculated by the acceleration calculation section; a second time calculation section that calculates a second time in a case where the main shaft rotating shaft is stopped at the target stop position by rotating in a reverse direction after temporarily stopping the rotation of the main shaft rotating shaft, based on the predetermined speed, the target stop position, the start position of the position control, and the acceleration calculated by the acceleration calculation section; a comparison section that compares the first time with the second time; and an oriented stop control section that selects one of a time until stopping at the target stop position that is shorter based on a comparison result of the comparison section to perform stop control of the motor.

2. The control device of the motor according to claim 1, characterized in that, in a case where it is determined that the second time is shorter than the first time, the control device of the motor performs control such that the main shaft rotating shaft is positioned at the target stop position by rotating in a reverse direction after deceleration stop at a maximum capacity. ​

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