JPH1118498A - Controller for servo motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform speed control smoothly, while preventing voltage saturation during high-speed rotation of a servo motor through providing means for controlling the current by setting the electric angle of a servo motor at an arbitrary value. SOLUTION: This controller for a servo motor comprises an electric angle setting section 21 for regulating the output from an electric angle calculating section 18, i.e., the electric angle of a motor, arbitrarily such that a torque constant equivalent to an induction voltage can be operated arbitrarily. The electric angle setting section 21 can produce an arbitrary shift from a calculated electric angle of the motor. A reactive current component, which is essentially '0', is generated in a servo motor 15 by the shift in the electric angle and the reactive component acting as a fluctuation component for the field flux produced from the permanent magnet in the servo motor 15. When the fluctuation is controlled in the direction for weakening the magnetic flux, the torque constant dependent on the magnetic flux of the servo motor 15 can be controlled to a low value, resulting in a smooth speed characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a servo motor control device, and more particularly to a servo motor control device for controlling a polyphase AC servo motor.

[0002]

2. Description of the Related Art Conventionally, as this kind of servo motor control device, one applied to a servo motor system shown in FIG. 6 is known. In the figure, a speed control unit 102 receives a speed command of a motor 105 from a speed command generation unit 101 and outputs a torque current command Iqc to a current control unit 103. At this time, the rotational position of the motor 105 is detected. The motor rotational speed output from the speed detecting means 110 is fed back based on the rotational position detected by the encoder 106, which is a detector, so as to eliminate a speed deviation. In this case, the speed detecting means 110 calculates the motor rotation speed by differentiating the position information obtained from the encoder 106 attached to the motor 105.

The current control unit 103 feeds back the current value of the motor 105, and the torque current of the motor 105
qc, and outputs a voltage command so that the orthogonal component of the torque current becomes “0”. Electric angle calculator 108
Calculates the electrical angle corresponding to the number of pole pairs of the motor 105 from the position signal of the encoder 106,
Output to q conversion section 109. The dq inverse conversion unit 104 receives a voltage command and an electrical angle in the orthogonal coordinate system, performs a quadrature / three-phase conversion on the voltage command, and outputs a three-phase voltage command to the motor 105.

A current detector 107 detects a current flowing in the U-phase and V-phase of the motor, A / D converts the current, and dq converter 109
Output to The dq converter 109 receives the U-phase and V-phase current values and the electrical angles, and performs three-phase / orthogonal conversion to obtain the torque current Iqf.
And the reactive current Idf. As described above, the conventional servo motor control device controls the current flowing through the motor 105 as a whole by dividing the current into a torque component and an ineffective component, and controls the motor to move according to a command from the speed command generator 101.

[0005]

Generally, when the motor is rotating at a steady state, the induced voltage constant Ke and the motor rotation speed ω
The motor rotates with the voltage command equal to the induced voltage of the motor determined by Ke × ωm from m. Further, when the motor is accelerated, a voltage corresponding to the torque current is generated.
At this time, the maximum value of the generated voltage is a power supply voltage value supplied to the servo control device. In some synchronous motors, to obtain high torque, the induced voltage constant Ke
In some cases, when the motor generates an accelerating torque during high-speed rotation, that is, when ωm is large, the induced voltage of the motor may exceed the power supply voltage. In this case, the voltage of the motor is clamped by the power supply voltage value, and may not reach the desired speed. In addition, since a desired current value is not generated, an error is accumulated in an integrator in the speed control unit and the current control unit, and an excessive command is generated. As a result, a current value oscillates, and an alarm is generated by an excessive current protection function. There was a problem that.

The present invention has been made in view of the above problems, and is a control device for a servomotor used in an NC machine tool, a robot, or the like. It is an object of the present invention to provide a servomotor control device capable of preventing voltage saturation and smoothly rotating a servomotor when saturation occurs.

[0007]

In order to achieve the above object, the invention according to claim 1 comprises a drive power output means for outputting drive power to a polyphase AC servomotor, and a rotation speed of the polyphase AC servomotor. And a reactive current control means for increasing the reactive current component of the driving power output means when the rotational speed detected by the speed detecting means is high.

[0008] In the invention according to claim 1 configured as described above, when the drive power output means outputs drive power to the polyphase AC servomotor, the speed detection means determines the rotational speed of the polyphase AC servomotor. Upon detection, the reactive current control means increases the reactive current component at the drive power output means when the rotational speed detected by the speed detection means is high. When the reactive current component in the driving power output means increases, the torque constant decreases,
Even at the time of high-speed rotation, the induced voltage does not increase and does not exceed the power supply voltage.

The driving power output means and the reactive current control means can be realized in various configurations. As an example, the invention according to claim 2 is the invention according to claim 1, wherein The driving power output means includes an electric angle calculating means for measuring an electric angle of the polyphase AC servomotor, and a voltage of a rectangular coordinate system converted to a voltage of a polyphase AC coordinate system based on the electric angle, and Voltage command output means for outputting to the AC servomotor, current feedback means for converting a current of the polyphase AC coordinate system flowing to the polyphase AC servomotor to a current of the orthogonal coordinate system based on the electric angle, and a speed command A corresponding current is input and feedback control is performed based on the current in the rectangular coordinate system so that the reactive current component is reduced so that the polyphase AC servomotor is reduced. Current control means for outputting a voltage in a rectangular coordinate system, wherein the reactive current control means changes the electrical angle when the rotation speed increases to generate a reactive current component. Is provided.

According to the second aspect of the present invention, the electric angle calculation means measures the electric angle of the multi-phase AC servomotor, and the current control means of the drive power output means controls the speed command. And outputs a voltage in the Cartesian coordinate system to the polyphase AC servomotor. Then, the voltage command output means converts the voltage of the rectangular coordinate system to the voltage of the polyphase AC coordinate system based on the electric angle and outputs the voltage to the polyphase AC servomotor, and the current feedback means based on the electric angle. Thus, the current of the polyphase AC coordinate system flowing through the polyphase AC servomotor is converted into the current of the orthogonal coordinate system. The current in the rectangular coordinate system thus converted is input to the current control means, and is subjected to feedback control so that the reactive current component is reduced. On the other hand, originally, the feedback control is performed so as to eliminate the reactive current component in this way. However, the electrical angle setting means of the reactive current control means sets the electrical angle when the rotation speed increases. Due to the change, the electrical angle to be fed back is shifted, and a predetermined amount of reactive current component is generated despite the feedback control.

As a preferred example of such an electric angle setting means, the invention according to claim 3 is the servo motor control device according to claim 2, wherein the electric angle setting means calculates the electric angle by the electric angle calculation means. The electrical angle is set such that a deviation angle is generated by multiplying the rotational speed by a predetermined coefficient with respect to the electrical angle. Claim 3 configured as described above.
According to the present invention, the electrical angle setting means sets an electrical angle that generates a shift angle obtained by multiplying the electrical angle calculated by the electrical angle calculating means by a predetermined coefficient.

That is, the larger the rotation speed, the larger the deviation angle is generated, and by setting an electrical angle with the deviation angle, the reactive current component also increases. As a result, the torque constant is greatly reduced, and even at the time of high-speed rotation, the induced voltage is not increased and does not exceed the power supply voltage.
According to a fourth aspect of the present invention, in the servo motor control device according to the third aspect, the electric angle setting means calculates the rotation speed based on a change amount of a rotation angle position of the polyphase AC servomotor. There is.

[0013] In the invention according to claim 4 configured as described above, the electric angle setting means inputs the rotational angle position of the polyphase AC servomotor and calculates the rotational speed from the change amount.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a servo system to which a servo motor control device according to an embodiment of the present invention is applied. In the figure, a speed control unit 12 receives a speed command of a motor 15 from a speed command generation unit 11 and outputs a signal representing an encoder 1 serving as a motor rotational position detector.
The rotation position from step 6 is fed back from the speed detection means 20 as the motor rotation speed, and a torque current command Iqc is output to the current control unit 13 so as to eliminate the speed deviation. Here, the speed detecting means 20 calculates by differentiating the position information obtained from the encoder 16 attached to the motor.

The current control section 13 feeds back the current value of the motor 15 so that the torque current of the motor 15 becomes Iq
and outputs a voltage command so that the quadrature component of the torque current becomes “0”. The electrical angle calculator 18 calculates an electrical angle corresponding to the number of pole pairs of the motor 15 from the position signal of the encoder 16 and outputs the electrical angle to the electrical angle setting unit 21. The electrical angle setting unit 21 sets an arbitrary value for the electrical angle calculated by the electrical angle calculation unit 18 and sets the dq inverse transform unit 14 and dq
Output to the conversion unit 19.

The dq inverse converter 14 receives a voltage command and an electrical angle in a rectangular coordinate system, performs a quadrature / three-phase conversion on the voltage command, and outputs a three-phase voltage command to the motor 15. Current detector 17
Detects the current flowing in the U-phase and V-phase of the motor, performs A / D conversion, and outputs the result to the dq converter 19. The dq conversion unit 19 uses U
The phase and V-phase current values and electrical angles are input, and three-phase / orthogonal conversion is performed to output torque current Iqf and reactive current Idf.

FIG. 2 shows a vector diagram of current control of a conventional synchronous servomotor. In the magnetic flux control of the synchronous motor, control is performed such that the d-axis matches the direction of the field magnetic flux. Therefore, if Idc = 0 and control is performed so that the d-axis current becomes 0, all the q-axis currents orthogonal to the d-axis can be controlled as torque components. The torque constant of the motor is Kt and the current command of the q axis is Iq
Assuming that c, the torque T generated in the motor is T = Kt × Iqc.

FIG. 3 shows a current control vector diagram when the electric angle is set to be shifted by the servo motor control device shown in FIG. In the figure, θr represents the amount of deviation between the electric angle used for control and the actual motor electric angle. The dq coordinates used in the dq transform unit 19 and the dq inverse transform unit 14 are represented by d ′ axis and q ′ axis. At this time, Idc '
= 0 and a torque current command of Iqc 'is given to the motor, the actual current command to the motor is Idc =-Iqc' x sinθr Iqc = Iqc 'x cosθr

Since the d-axis component flowing here can be approximated by a first-order relationship with respect to the field magnetic flux, if the conversion coefficient between Idc and Kt is β, the torque T becomes T = Kt (1 + β × Idc) × Iqc = Kt (1 + β × Iqc ′ × sin θr) × Iqc ′ ×
cos θr. Therefore, the torque constant K when the electrical angle is shifted
t ′ is given by: Kt = T / Ipc ′ = Kt (1 + β × Iqc ′ × sin
θr) × cos θr. Here, Kt ′ is K when the electric angle is not shifted.
For t, Kt ′ / Kt = (1 + β × Iqc ′ × sin θr) × c
osθr.

As is clear from the results of the above equation, setting θr between 0 ° and 90 ° makes it possible to reduce the torque constant and the induced voltage, thereby preventing voltage saturation. be able to. Further, by setting θr to θr = α × ωm using the coefficient α and the motor speed ωm, the influence on the conventional control is reduced in the low rotation region where no problem occurs, and only in the high rotation region which is a problem to be solved. It is possible to exert the effect. Since the motor speed ωm is proportional to the change amount Δθ of the electrical angle per unit time, the above equation can be expressed as θr = α ′ × Δθ.

FIG. 4 specifically shows an embodiment of the electrical angle setting unit 21 at this time. With the electric angle θ of the motor 15 as an input,
The electrical angle deviation amount θr is calculated by differentiating by the differentiating means 22 and multiplying by the constant α ′ by the multiplying means 23. This shift amount is added to the electrical angle θ by the adding means 24 to calculate an output θ ′, which is output to the dq inverse converter and the dq converter.

FIG. 5 is a diagram showing a specific effect of the present invention having the electrical angle setting unit shown in FIG. Here, ωm is the motor speed, ωmax is the maximum rotation speed of the motor, and T is the output torque of the motor. Graph A represents the conventional control, and B represents the maximum torque value that can be generated by the motor without causing voltage saturation in the case of the present invention. Here, the range in which the output torque is constant irrespective of the motor speed is due to the fact that the current value that can flow through the winding of the motor is limited.

As apparent from FIG. 5, in the case B according to the present invention, it is possible to generate a larger torque without causing voltage saturation in the high-speed region as compared with the case A according to the prior art. You can see that there is. Therefore, in B, since the limit torque at which current oscillation occurs is large, smoother and faster motor speed control is possible compared to A.

As described above, the present servo motor control device
An electric angle setting unit that can adjust an arbitrary value with respect to the motor electric angle output from the electric angle calculation unit so that the torque constant equivalent to the induced voltage can be arbitrarily manipulated. Since the angle setting unit can cause an arbitrary deviation from the calculated electric angle of the motor, the deviation generates a reactive current component that should be “0” in the servo motor. The current acts as a fluctuation component with respect to the field magnetic flux generated by the permanent magnet of the servo motor, and by controlling this fluctuation in a direction to weaken the magnetic flux, the torque constant depending on the magnetic flux of the servo motor can be controlled to be small. In addition, smooth speed characteristics can be realized.

[0025]

As described above, the present invention can provide a servomotor control device capable of preventing voltage saturation by lowering the induced voltage constant during high-speed rotation. Further, according to the second aspect of the present invention, it is possible to generate a desired reactive current by setting an electrical angle in a feedback control system formed based on the electrical angle. That is, by having a means for setting an arbitrary value to the electric angle of the servo motor and performing current control,
Voltage saturation during high-speed rotation of the servomotor can be prevented, and smooth speed control can be performed.

Further, according to the invention of claim 3,
Since the ratio of the reactive current component increases as the rotation speed increases, it is possible to prevent the occurrence of the reactive current component from having a large effect while the rotation speed is low. Further, according to the invention of claim 4, it is possible to calculate the rotation speed even if the input is the rotation angle position.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a servo motor control device according to the present invention.

FIG. 2 is a vector diagram of current control of a conventional motor.

FIG. 3 is a vector diagram of current control of the motor according to the present invention.

FIG. 4 is a block diagram illustrating a specific configuration example of an electrical angle setting unit.

FIG. 5 is a characteristic diagram showing an effect of the servo motor control device according to the present invention.

FIG. 6 is a block diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 11 speed command generator 12 speed controller 13 current controller 14 dq inverse converter 15 motor 16 encoder 17 current detector 18 electrical angle calculator 19 dq converter 20 speed detector 21 electrical angle setting unit 22 differentiator 23 multiplier 24 Addition means

Claims (4)

[Claims] 1. A drive power output means for outputting drive power to a polyphase AC servomotor, a speed detection means for detecting a rotation speed of the polyphase AC servomotor, and a rotation speed detected by the speed detection means And a reactive current control means for increasing the reactive current component in the drive power output means when is larger. 2. The servo motor control device according to claim 1, wherein said driving power output means includes: an electric angle calculating means for measuring an electric angle of said multi-phase AC servomotor; Voltage command output means for converting a voltage of a coordinate system into a voltage of a polyphase AC coordinate system and outputting the voltage to the polyphase AC servomotor; and a polyphase AC coordinate system flowing through the polyphase AC servomotor based on the electric angle. Current feedback means for converting the current of the rectangular coordinate system into a current of the rectangular coordinate system; and a current feedback means for inputting a current corresponding to the speed command and performing feedback control based on the current of the rectangular coordinate system to reduce the reactive current component. Current control means for outputting the voltage of the rectangular coordinate system to the phase AC servomotor, and the reactive current control means, when the rotation speed is increased Servo motor control apparatus characterized by having an electrical angle setting means for producing a reactive current component by changing the electrical angle. 3. The servo motor control device according to claim 2, wherein the electric angle setting means calculates a deviation angle obtained by multiplying the electric angle calculated by the electric angle calculation means by a predetermined coefficient by the rotation speed. A servo motor control device for setting the generated electrical angle. 4. The servo motor control device according to claim 3, wherein the electric angle setting means calculates the rotation speed based on a change amount of a rotation angle position of the multi-phase AC servo motor. Servo motor control device.