JP4045828B2 - Servo control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a servo control device that controls movement of a moving body by a motor (servo motor).
[0002]
[Prior art]
When the article is moved, servo control is used as position control of the article (moving body). For example, servo control is used for position control when an article or an electronic component is repeatedly conveyed between two predetermined positions in an article conveyance device in a physical distribution system or an electronic component conveyance device in a clean room. ing. For example, in a belt forward / reverse traverse device that traverses during fiber winding, servo control is used for position control when the traverse guide reciprocates within a predetermined range.
[0003]
An outline of a servo control device for controlling the servo motor is shown in FIG. In FIG. 6, the current controller 14 that controls the motor current of a servo motor (hereinafter referred to as a motor) 20 to be a target motor current specified by a current command, and the position of a moving body that is moved by the motor 20 are shown. A position control unit 10 and a speed control unit 12 that specify the target motor current so as to be in the position specified by the position command are provided.
[0004]
For example, a position command output from a central control unit (not shown) of the conveyance device and a rotation detection signal output from the rotation detector 22 that detects the rotation state of the motor 20 are input to the position control unit 10. The position control unit 10 calculates a position feedback amount based on the rotation detection signal, calculates a position deviation amount based on the position command and the position feedback amount, and outputs a speed command corresponding to the calculated position deviation amount.
[0005]
The speed control unit 12 receives the speed command output from the position control unit 10 and the rotation detection signal output from the rotation detector 22. The speed control unit 12 calculates a speed feedback amount based on the rotation detection signal, calculates a speed deviation amount based on the speed command and the speed feedback amount, and outputs a current command corresponding to the calculated speed deviation amount.
[0006]
The current control unit 14 receives the current command output from the speed control unit 12 and the current detection signal output from the current detector 24 that detects the motor current of the motor 20. The current control unit 14 calculates a motor current based on the current detection signal, and calculates a current deviation amount between the current command and the motor current. The current control unit 14 outputs a voltage command corresponding to the current deviation amount, and increases or decreases the motor current.
[0007]
[Problems to be solved by the invention]
In the servo control device described above, the speed and acceleration of the moving body are limited by the calculation time of the speed command and the current command and the transfer time of the rotation detection signal. For example, the relationship between the position of the moving body and the speed in servo control is shown in FIG. 7. In most cases, as shown in FIG. 7, the speed is a maximum value (a value determined by the characteristics of the servo motor, the load of the conveyed object, etc. ) Is limited to a smaller value.
[0008]
In the transport apparatus or traverse apparatus described above, the faster the moving body, the shorter the transport time or the winding speed, and the shorter the overall processing time including the movement of the moving body. Efficiency can be increased. However, as shown in FIG. 7, since the moving speed is limited by the calculation time of the speed command and the current command and the transfer time of the rotation detection signal, the transport time can be shortened or the winding speed can be increased. I'm not there.
[0009]
The present invention has been made in view of such circumstances. While the moving body moves from the movement start position to a predetermined position, the position control unit and the speed control are switched by a switching unit that switches to control using only the current control unit. It is an object of the present invention to provide a servo control device that eliminates the limitation on the movement speed that occurs when using the unit, increases the movement speed faster than the limitation, and improves the efficiency of the entire process including the movement of the moving object.
[0010]
Further, the present invention performs position detection by measuring means for measuring the elapsed time from the start of movement and detecting means for detecting that the elapsed time has reached the predetermined time for the moving body to reach the predetermined position. It is another object of the present invention to provide a servo control device that can detect that a moving body has reached a predetermined position.
[0011]
In addition, the present invention provides a servo control device that can increase the moving speed to a value close to the maximum value that can be output by the motor by a designation means that instructs the current control unit to supply a target motor current that is large enough not to damage the motor. For the purpose.
[0012]
The present invention also provides a switching means for switching the detection accuracy (calculation accuracy) of the position of the moving body to lower the calculation accuracy than usual, thereby reducing the calculation load on the position control unit and the speed control unit and limiting the movement speed. It is an object of the present invention to provide a servo control device that can improve the efficiency of the entire process including the movement of a moving body by reducing the above-described problem and increasing the moving speed.
[0013]
The present invention also provides a high-accuracy position detection with a low-precision position detection signal transfer speed by position detection means for outputting a low-precision position detection signal with a small number of digits or a high-precision position detection signal with a large number of digits. An object of the present invention is to provide a servo control device which can be made faster than a signal and speed up the processing time of position detection by the position control unit and the speed control unit.
[0014]
[Means for Solving the Problems]
The servo control device according to the first aspect of the present invention includes a position control unit that sets a target speed of the motor so that the position of the moving body moved by the motor becomes the target position, and a target so that the speed of the motor matches the target speed. In a servo control device having a speed control unit for setting a motor current and a current control unit for controlling the motor current so as to match the target motor current, the moving body moves from the movement start position to the movement end position. Switching means for switching between control by the current control unit and control by the current control unit, position control unit, and speed control unit at a predetermined position, and while the moving body moves from the movement start position to the predetermined position, the current control unit The control by the position control unit and the speed control unit is not performed, and the current control unit, the position control unit and the speed control unit are used while moving from the predetermined position to the movement end position. Wherein the are no order to perform the control.
[0015]
Such a servo control device performs control using only the current control unit while the moving body moves from the movement start position to the predetermined position by the switching means, and control using the position control unit and the speed control unit is not performed. Not performed. And while moving to a movement end position from a predetermined position, control using a current control part, a position control part, and a speed control part is performed. When only the current control unit is used, the moving speed of the moving body is not limited by the calculation time of the position of the moving body by the position control unit and the speed control unit, so the moving speed is higher than the limited speed. Speed can be increased. Further, the predetermined position is set so that the moving body can accurately stop at the movement end position. Between the movement start position and the predetermined position, only the current control unit is used to increase the moving speed, and between the predetermined position and the movement end position, the current control unit, the position control unit, and the speed control unit are used with high accuracy. Position control can be performed.
[0016]
According to a second aspect of the present invention, there is provided a servo control device according to the first aspect, further comprising: a measuring unit that measures an elapsed time from the start of movement of the moving body; and a detecting unit that detects that the elapsed time has reached a predetermined time. When the elapsed time reaches the predetermined time, the switching means switches from the control by the current control unit to the control by the current control unit, the position control unit and the speed control unit.
[0017]
In such a servo control device, the elapsed time from the start of movement of the moving body is measured by the measuring means, and the elapsed time is measured by the detecting means for a predetermined time after reaching the predetermined position after the moving body starts moving. Detects that When the elapsed time reaches a predetermined time, the switching means switches from control by the current control unit to control by the current control unit, position control unit, and speed control unit. As in the first invention, during the period from the movement start position to the predetermined position, the movement speed can be increased using only the current control unit, and the movement is performed based on the time measured by the measuring means without performing position detection. The detection means can detect that the body has reached a predetermined position. In an electronic component conveying device, a belt forward / reverse traverse device, and the like, the load and moving distance are often determined in advance, and a predetermined time for the moving body to reach a predetermined position is obtained in advance based on motor characteristics. be able to.
[0018]
According to a third aspect of the present invention, the servo control device according to the first or second aspect further comprises designation means for designating a target motor current, and the current control unit is designated while the moving body moves from the movement start position to the predetermined position. The motor current is controlled based on a target motor current designated by the means.
[0019]
In such a servo control device, while the moving body moves from the movement start position to a predetermined position, the current control unit performs control based on the target motor current designated by the designation means. The target motor current specified by the specifying means can be set to a large target motor current that does not damage the motor, and the moving speed can be increased to near the maximum value that the motor can output.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
(First embodiment)
FIG. 1 shows a schematic configuration of a servo control device according to the present invention. The servo control device drives the motor 20 such that the current detector 24 outputs a current detection signal corresponding to the motor current flowing through the motor (servo motor) 20 and the motor current becomes the target motor current specified by the current command. Current control unit 14 that performs rotation, a rotation detector 22 that outputs a rotation detection signal corresponding to the position of the moving body that is moved by the motor 20, and a target motor current so that the position of the moving body becomes a position specified by the position command. A position control unit 10 and a speed control unit 12 that specify (current command), a switching unit (switching unit) 30 that switches a current command applied to the current control unit 14, and a timer (detection unit) 32 that instructs switching of the current command. With.
[0025]
The speed command output of the position control unit 10 is connected to the speed command input of the speed control unit 12, the current command output of the speed control unit 12 is connected to one of the inputs (terminal b) of the switching unit 30, and the output of the switching unit 30 (Terminal c) is connected to the current command input of the current control unit 14. The output of the current control unit 14 is connected to a current amplification unit that increases or decreases the motor current flowing through the motor 20. The switching command output of the timer 32 is connected to the switching command input of the switching unit 30.
[0026]
The motor (servo motor) 20 is a motor in which the motor current and the torque are substantially proportional, and for example, a brushless DC motor can be used. In the vicinity of the motor 20, a rotation detector 22 for detecting the rotation state of the motor and a current detector 24 for detecting the motor current are provided, and the rotation detection signal output of the rotation detector 22 is output from the position controller 10 and the speed. The rotation detection signal input of the control unit 12 is connected to each other, and the current detection signal output of the current detector 24 is connected to the current detection signal input of the current control unit 14.
[0027]
For example, a position command output from a central control unit (not shown) of the transfer device is input to the position control unit 10. The position control unit 10 calculates a position feedback amount based on the rotation detection signal, calculates a position deviation amount based on the position command and the position feedback amount, and outputs a speed command corresponding to the calculated position deviation amount. The speed control unit 12 calculates a speed feedback amount based on the rotation detection signal, calculates a speed deviation amount based on the speed command and the speed feedback amount, and outputs a current command corresponding to the calculated speed deviation amount. To do.
[0028]
For example, a current command is input to the other input (terminal a) of the switching unit 30 from the above-described central control unit (designating means). Hereinafter, a current command input from the central control unit to the terminal a is referred to as a current command A, and a current command input from the speed control unit 12 to the terminal b is referred to as a current command B. The switching unit 30 switches the connection between the terminal a and the terminal c and the connection between the terminal b and the terminal c according to the switching command output from the timer 32.
[0029]
The target motor current corresponding to the current command A is larger than the maximum value of the target motor current corresponding to the current command B, and smaller than the motor current at which the motor 20 is damaged. Since the motor 20 is not damaged even if a motor current exceeding the rating is applied for a short time, the target motor current corresponding to the current command A can be set higher than the rating.
[0030]
The timer 32 measures the elapsed time from the start of movement of the moving body, and outputs a switching command when the elapsed time reaches the set time. Switching unit 30 connects terminal a and terminal c until a switching command is input, and connects terminal b and terminal c after the switching command is input. Therefore, the current command A is input to the current control unit 14 until the set time has elapsed from the start of movement. In addition, the current command B is input to the current control unit 14 after the set time has elapsed until the end of movement.
[0031]
FIG. 2 shows the relationship between the position of the moving body and the speed when the current command is switched. Since the current command A corresponds to the maximum motor current that does not damage the motor 20, and the current command B corresponds to the limited motor current similar to the conventional servo control, as shown in FIG. Increases acceleration and maximum speed. In FIG. 2, the alternate long and short dash line indicates the speed of conventional servo control.
[0032]
The set time is set based on the time until the moving body reaches a set position between the movement start position and the movement end position. The setting position is set so that the moving body does not exceed the movement end position. In order to shorten the movement time, the set position is preferably closer to the movement end position.
[0033]
The current control unit 14 calculates a motor current based on the current detection signal, calculates a current deviation amount between the current command (current command A or B) and the motor current, and outputs a voltage command corresponding to the calculated current deviation amount. Output.
[0034]
Next, motor drive control using the servo control apparatus according to the present invention will be described.
An example of the servo control procedure is shown in FIG. A movement command is sent from the above-described central control unit to the servo control device, and servo control for movement of the moving body is performed.
[0035]
The timer 32 outputs a switching command so that the terminals a and c of the switching unit 30 are connected, switches the current command input to the current control unit 14 to the current command A, and starts moving the moving body. At the same time, timing is started (S12). In this case, the current control unit 14 controls the motor 20 based on the current command A. The motor 20 is controlled using only the primary control loop by the current control unit 14 without using the secondary control loop by the position control unit 10 and the speed control unit 12 (S14). Since the secondary control loop is not used, the moving speed is not limited, and the acceleration and the maximum speed can be improved.
[0036]
Until the set time elapses, the motor 20 is controlled only by the primary control loop (S16: NO). When the set time has passed (S16: YES), the timer 32 outputs a switching command so that the terminals b and c of the switching unit 30 are connected, and the current command input to the current control unit 14 is Switch to the command B (S18). In this case, the current control unit 14 controls the motor 20 based on the current command B. The motor 20 is controlled using the primary control loop by the current control unit 14 and the secondary control loop by the position control unit 10 and the speed control unit 12 (S20). Since the secondary control loop is used, the moving speed is limited, but accurate position control can be performed.
[0037]
Control of the motor 20 by the primary and secondary control loops is performed until the movement ends (S22: YES), that is, until the conveyed product reaches a predetermined position (S22: NO). Thereby, a conveyed product etc. can be stopped in the exact stop position. In the above example, the timer 32 is used and the switching unit 30 performs switching based on the elapsed time, but instead of using the elapsed time, position detection is always performed from the start of movement (position control is performed). If the position reaches a preset position (set position), the switching unit 30 may perform switching. In either case of using the elapsed time or the detection position, it is necessary to always detect (obtain) the current position after the movement starts. When switching is performed based on the elapsed time, the position deviation (deviation between the target position and the current position) is forcibly made zero simultaneously with the switching, and then control using the secondary control loop is started.
[0038]
(Second Embodiment)
FIG. 4 shows another schematic configuration of the servo control device according to the present invention. The servo control device includes a current control unit 14, a position control unit 10 and a speed control unit 12, a rotation detector (position detection unit) 22 and a current detector 24, and a comparison unit (switching unit) 40. The motor 20, the current detector 24, and the current control unit 14 are the same as those in the first embodiment. The rotation detector 22, the position controller 10 and the speed controller 12 are basically the same as those in the first embodiment. However, in this embodiment, the position detection or calculation accuracy is changed. Is possible.
[0039]
The comparison unit 40 compares the position (current position) detected (calculated) by the position control unit 10 with a preset position (set position), and is output from the rotation detector 22 according to the comparison result. The accuracy of the rotation detection signal and the accuracy of position detection (calculation) of the position control unit 10 and the speed control unit 12 are switched. As in the first embodiment, the setting position is set so that the moving body does not exceed the movement end position.
[0040]
The connection of the position control unit 10, the speed control unit 12, the current control unit 14, the motor 20, the rotation detector 22 and the current detector 24 is substantially the same as in the first embodiment, but the current of the speed control unit 12 is The command output is connected to the current command input of the current control unit 14.
[0041]
The current position signal output of the position control unit 10 is connected to the current position signal input of the comparison unit 40, and the switching command output of the comparison unit 40 is the switching command input of the rotation detector 22, the position control unit 10 and the speed control unit 12. Connected to each.
[0042]
A setting position command is input to the comparison unit 40 from the above-described central control unit. The comparison unit 40 compares the current position signal with the set position command, determines whether or not the moving body has reached the set position, and instructs switching of the calculation accuracy according to the determination result.
[0043]
For example, the rotation detector 22 switches and outputs a 16-bit or higher-order 8-bit rotation detection signal of the 16 bits, and the position control unit 10 and the speed control unit 12 use a 16-bit or 8-bit rotation detection signal. Calculation of accuracy (16 bits) or low accuracy (8 bits) is performed.
[0044]
The comparison unit 40 switches the accuracy to 8 bits until the current position reaches the set position, and switches to 16 bits after reaching the set position. When the precision is 8 bits, the amount of data is smaller than when the precision is 16 bits, and the transfer time of the rotation detection signal is shortened. In addition, the feedback amount of the position control unit 10 and the speed control unit 12 and the command calculation time are also shortened. By reducing the transfer time and the calculation time, the moving speed of the moving body can be increased.
[0045]
The relationship between the position of the moving body and the speed when the accuracy is switched is substantially the same as in the first embodiment. As shown in FIG. 2, the acceleration and the maximum speed at the start of movement are improved.
[0046]
Next, motor drive control using the servo control apparatus according to the present invention will be described.
An example of the servo control procedure is shown in FIG. A movement command is sent from the above-described central control unit to the servo control device, and servo control for movement of the moving body is performed. The comparison unit 40 outputs a switching command to 8 bits and switches the accuracy to 8 bits, and then the movement of the moving body is started (S32). In this case, the rotation detection signal is 8 bits, and the position control unit 10 and the speed control unit 12 perform calculation with 8 bits (S34). Since it is 8 bits, the accuracy is lower than that of 16 bits, but the transfer time and calculation time are shortened, and the moving speed of the moving body can be increased.
[0047]
Until the current position reaches the set position, the drive control of the motor 20 with an accuracy of 8 bits is performed (S36: NO). When the set position is reached (S36: YES), a switching command to 16 bits is output from the comparison unit 40 (S38). In this case, the rotation detection signal is 16 bits, and the position control unit 10 and the speed control unit 12 perform calculation with 16 bits (S40). Since it is 16 bits, the transfer time and calculation time increase compared to 8 bits, and the movement speed is limited, but the accuracy of position detection is improved.
[0048]
Until the movement is completed (S42: YES), that is, until the conveyed product reaches a predetermined position, control of the motor 20 with 16 bits of precision is performed (S42: NO). Thereby, a conveyed product etc. can be stopped in the exact stop position.
[0049]
【The invention's effect】
According to the first invention, the position control unit and the speed control unit are used by performing control using only the current control unit while the moving body moves from the movement start position to the predetermined position by the switching unit. Therefore, the movement speed can be made faster than the restriction. The movement speed can be increased, and the efficiency of the entire process including the movement of the moving body can be improved.
[0050]
According to the second aspect of the invention, the elapsed time is measured by the measuring means, and the detection means detects that the elapsed time has reached a predetermined time, thereby detecting the time by the measuring means and the predetermined time by the detecting means without performing position detection. By detecting the passage of time, it is possible to detect that the moving body has reached the predetermined position.
[0051]
According to the third aspect of the invention, while the moving body moves from the movement start position to the predetermined position, the designation means instructs the current control unit to provide a large target motor current that does not cause the motor to be damaged. The speed can be increased to near the maximum value that the motor can output.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a servo control device according to the present invention.
FIG. 2 is a diagram showing an example of changes in the position and speed of a moving body by servo control according to the present invention.
FIG. 3 is a flowchart showing an example of a servo control procedure according to the present invention.
FIG. 4 is a block diagram showing another schematic configuration of the servo control device according to the present invention.
FIG. 5 is a flowchart showing another example of a servo control procedure according to the present invention.
FIG. 6 is a block diagram showing a schematic configuration of a conventional servo control device.
FIG. 7 is a diagram showing an example of changes in the position and speed of a moving body by conventional servo control.
[Explanation of symbols]
10 Position control unit 12 Speed control unit 14 Current control unit 20 Motor (servo motor)
22 Rotation detector (position detection means)
24 current detector 30 switching part (switching means)
32 timer (detection means)
40 comparison part (switching means)

Claims (3)

A position controller that sets the target speed of the motor so that the position of the moving body moved by the motor becomes the target position; a speed controller that sets the target motor current so that the speed of the motor matches the target speed; In a servo control device including a current control unit that controls a motor current so as to match a target motor current,
Switching means for switching between the control by the current control unit and the control by the current control unit, the position control unit and the speed control unit at a predetermined position while the moving body moves from the movement start position to the movement end position;
Control is performed by the current control unit while the moving body moves from the movement start position to the predetermined position, and control is not performed by the position control unit and the speed control unit, and current control is performed while moving from the predetermined position to the movement end position. A servo control device characterized in that control is performed by a control unit, a position control unit, and a speed control unit. A measuring means for measuring the elapsed time from the start of movement of the moving object;
Detecting means for detecting that the elapsed time has reached a predetermined time, and when the elapsed time has reached the predetermined time, the switching means causes the current control section, the position control section, and the speed to be changed from the control by the current control section. 2. The servo control device according to claim 1, wherein the servo control device is configured to switch to control by a control unit. A specifying means for specifying the target motor current is provided.
3. The current control unit is configured to control the motor current based on a target motor current designated by the designation means while the moving body moves from the movement start position to the predetermined position. The servo control device described.

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