JP2811685B2 - Servo motor controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servomotor control device that feedback-controls a servomotor according to an operation command.

[Prior Art] Servo motors are frequently used in various NC machine tools, robots, measuring devices and the like.

The servomotor control device performs feedback control of the servomotor in accordance with the operation command.

That is, for example, when a target rotation position and a target rotation speed are input as operation commands, a current command value to be supplied to the servomotor is calculated from these target values and the current rotation position and rotation speed of the servomotor, Feedback control is performed by multiplying the deviation between the current actually supplied to the servomotor and the current command value by a predetermined coefficient (feedback gain).

As described above, the servo motor generates a rotating magnetic field by the supplied current, and the rotor rotates in synchronization with the rotating magnetic field.

However, when the rotation speed of the servomotor increases, the current that actually flows is delayed by a predetermined phase with respect to the current command value. Note that the phase of the current command value matches the phase of the power supply voltage.

That is, the current command value changes in synchronization with the rotational position of the servomotor, but the current i that actually flows depends on the power supply voltage.
Assuming that Vm, ω is the cycle, r is the resistance, and L is the inductance of the servomotor, it is expressed by the following equation.

Therefore, the current i actually flowing is theoretically θ θ compared to the current command value corresponding to the rotational position of the servomotor.
Only be delayed. In reality, this delay slightly varies depending on each servomotor.

FIG. 6 shows this relationship. The solid line is the current command value, and the broken line is the current i that actually flows. The dashed line indicates the deviation between the current command value and the current i that actually flows.

The hatched portions in FIG. 6 are portions (ineffective portions) where the supplied current does not contribute to the rotation of the servomotor.

In the conventional servo motor control device, the feedback gain is set so that the invalid portion is minimized. However, as is apparent from the above equation, the phase delay θ
Since it changes depending on the rotation speed, the optimum feedback gain cannot be set over all the rotation speeds, and only the optimum feedback gain is used at the most frequently used rotation speed.

Therefore, especially when the rotation speed increases, the invalid portion increases, and the efficiency of the servomotor deteriorates.

That is, the ratio of the supplied current to the torque decreases, and the amount of generated heat increases.

When the servo motor rotates as described above, a back electromotive force (induced voltage) is generated in the coil of the servo motor.

The induced voltage Em is generated in a direction to cancel the supplied current, and is represented by the following equation, where N is the number of turns of the coil and Φ is the magnetic flux. Note that Φm is the maximum value of the magnetic flux.

Therefore, the induced voltage Em increases in proportion to the change rate of the magnetic flux, that is, the rotation speed of the servomotor.

Therefore, especially when the rotation speed is high, the voltage applied to the servomotor is canceled out by the induced voltage Em and decreases,
The current that actually flows is smaller than the current command value.

As a result, the torque of the servomotor becomes smaller than the value specified by the work command.

To cope with this, the current actually flowing through the coil is detected, and the feedback control of the current is performed so that the desired current flows through the servomotor.

[Problems to be Solved by the Invention] The present invention provides a servomotor control device that compensates for the above-described current phase shift, efficiently controls the servomotor, and generates a desired torque with a simpler configuration. The purpose is to:

[Means for Solving the Problems] As illustrated in FIG. 1, the servo motor control device of the present invention operates such that the servo motor M1 operates according to an operation command.
What is claimed is: 1. A servo motor control device for controlling a current supplied to a servo motor M1, comprising: state detection means M2 for detecting a rotation position and a rotation speed of the servo motor M1; A current command value calculating means M3 for calculating a current command value to be supplied to the servo motor M1 using the command; and a servo motor M1 based on the calculated current command value.
Servo motor drive means M4 for controlling the current supplied to the motor
And current phase storage means (not shown) in which the relationship between the rotation speed of the servomotor M1 and the current phase shift with respect to the current command value generated according to the rotation speed is stored in advance. Current phase compensation amount for the rotation speed
The current compensation amount determining means M5, which is determined based on the relationship stored in the current phase storage means, and the relationship between the rotation speed of the servo motor M1 and the amount of reduction in current due to the induced voltage generated according to the rotation speed. A current reduction amount storage means (not shown) stored in advance; and a voltage compensation amount determination means M6 for determining the voltage compensation amount for the detected rotation speed based on the relationship stored in the current reduction amount storage means. And current command value correction means M7 for correcting the current command value based on the determined current phase compensation amount and voltage compensation amount.

[Operation] In the present servomotor control device, the current compensation amount determining means M5 estimates the delay of the phase of the current actually flowing with respect to the current command value from the rotation speed of the servomotor M1 detected by the state detecting means M2. This estimation is performed based on the relationship between the rotation speed of the servomotor M1 and the current phase shift with respect to the current command value generated according to the rotation speed, which is stored in the current phase storage means in advance. Then, the phase of the current command value calculated by the current command value calculation means M3 is advanced in advance by the current command value correction means M7 by an amount corresponding to this delay.

Therefore, when the servo motor M1 is controlled by the corrected current command value in the servo motor driving means M4, especially at a high rotation speed, the delay of the phase of the current actually flowing with respect to the rotation position of the servo motor M1 is reduced. And the servomotor can be efficiently controlled.

Further, a voltage drop due to the induced voltage is estimated by the voltage compensation amount determining means M6 from the rotation speed of the servo motor M1. This estimation is performed based on the relationship between the rotational speed of the servo motor M1 and the amount of decrease in the current due to the induced voltage generated according to the rotational speed, which is stored in advance in the current decrease amount storage means. Then, the current command value calculated by the current command value calculation means M3 is increased in advance by the current command value correction means M7 by an amount corresponding to the voltage drop.

Therefore, when the servomotor M1 is controlled, particularly in the case of high rotation, a reduction in the current that actually flows due to the generation of the induced voltage is compensated.

That is, by performing both the phase compensation of the current and the compensation of the induced voltage, the current supplied to the servomotor is controlled so as to generate a desired torque without performing the feedback control of the current which is conventionally required. be able to. In addition, since the relationship between the rotational speed of the servo motor M1 and the phase shift of the current is stored in advance in the current phase storage means, the device configuration is simple, and the phase shift is determined immediately when the rotational speed is detected. can do.

Further, since the relationship between the rotation speed of the servo motor M1 and the amount of decrease in current is also stored in advance in the current decrease amount storage means,
As soon as the rotation speed is detected, the amount of current decrease can be determined.

Embodiment An embodiment of the present invention will be described with reference to FIGS.

 FIG. 2 is a configuration diagram of the present embodiment.

The controller 10 is constituted by a digital circuit centered on a microcomputer as shown in the figure in consideration of simplification of the configuration and versatility.

That is, the CPU 10a that executes a logical operation, the ROM 10b that nonvolatilely stores various control programs executed by the CPU 10a and the respective data tables used in the programs, and temporarily stores information to assist the operation of the CPU 10a. RAM1
0c, an input / output port 10d for exchanging information between these logic circuits and other devices is a main part.

Other devices of the controller 10 output a PWM signal according to a control signal input from the input / output port 10d.
A PWM circuit 10e and a pre-driver 10f for driving a power amplifier 10g configured by a power transistor based on the PWM signal are provided.

Since the three-phase alternating current PWM controlled by the power amplifier 10g is supplied as the armature current of the control motor 20,
The driving of the control motor 20 is controlled by a control signal output from the input / output port 10d, that is, by a logic circuit centering on the CPU 10a.

In addition, the controller 10 employs a feedback control method to stably control the control motor 20 with higher accuracy.

The information about the output of the control motor 20 that is fed back is the detection output of the encoder 26 that detects the rotational position of the rotation shaft of the control motor 20.

The rotational position of the control motor 20 detected by the encoder 26 is a relative position between a stator and a rotor constituting the control motor, and the rotational position is differentiated and used as a rotational speed.

The rotating shaft of the control motor 20 is connected to a ball screw 32 screwed to a table 30 on which a work or the like is placed.

Therefore, when the rotation shaft of the control motor 20 rotates, the ball screw 32 rotates, and the screwed table 30 can be moved in the horizontal direction in the drawing.

At this time, the amount of rotation of the rotating shaft corresponds to the amount of movement of the table 30,
The rotation speed of the rotating shaft corresponds to the moving speed of the table 30.

Also, as described above, the ROM 10b of the controller 10
In addition to the control program, the delay amount of the phase of the current that actually flows with respect to the rotation speed of the control motor 20 is defined as the current phase compensation amount, and the actual reduction amount of the current due to the induced voltage with respect to the rotation speed is also the voltage compensation amount. It is stored as

This current phase compensation amount is determined by the theoretical delay amount θ described in “Prior Art” and the delay amount experimentally obtained from the control motor 20, and the voltage compensation amount is described in “Prior Art”. It is determined by the theoretical induced voltage Em and the amount of voltage decrease obtained from the control motor 20 through experiments.

An example of the relationship between the rotation speed and the current phase compensation amount is shown in FIG.
FIG. 5A shows the relationship between the rotation speed and the voltage compensation amount in the fifth embodiment.
It is shown in FIG.

As is known, a logic circuit centering on the CPU 10a is like an aggregate of various electronic components, and by executing a predetermined program on these, various electronic circuits of interest can be configured. .

The controller 10 of the present embodiment operates as shown in FIG. 3 by a program stored in the ROM 10b.

This program is repeatedly executed from the time when the servo system including the controller 10 is started, and is repeatedly executed at predetermined intervals.

First, when control is started, a control command and a rotational position of the control motor 20 are input (step S100).

The control command is input from a keyboard or the like (not shown), and includes target information such as a rotation speed and a rotation position of the control motor 20, and the rotation position of the control motor 20 is input from the encoder 26. .

Next, the rotational speed of the control motor 20 is calculated by differentiating the input rotational position of the control motor 20 (step S110).

Subsequently, a current command value for energizing the control motor 20 is calculated from the control command, the rotation position and the rotation speed of the control motor 20 (step S120).

Since the calculation of the current command value is well known, the description is omitted.

Next, a current phase compensation amount (see FIG. 5A) stored in advance from the ROM 10b is calculated from the ROM 10b using the calculated rotation speed (Step S130). The previously stored voltage compensation amount (fifth
FIG. (B) is calculated) (step S140).

Then, the current command value calculated in step S120 is
Correction is performed using the calculated current phase compensation amount and voltage compensation amount (step S150).

The correction based on the current phase compensation amount is performed by superimposing a sine wave having the same peak value and cycle as the current command value but having a phase advanced by the calculated current phase compensation amount on the current command value. . The correction based on the voltage compensation amount is performed by adding a value corresponding to the current value reduced by the induced voltage to the current command value.

Next, the current command value thus corrected is converted into a PWM signal and output from the input / output port 10d to the PWM circuit 10e (step S160), and the process ends.

FIG. 4 is a block diagram visually showing a pseudo electronic circuit configured as the controller 10 by the above program.

By executing the above program, the logic circuit constituted by the CPU 10a or the input / output port 10d constitutes a servo circuit having a double feedback loop as shown. Note that K1 to K3 are used when calculating each value.
It corresponds to a coefficient at the time of a logical operation executed in U10a.

In brief, when a control command is given to this servo system, the servomotor 20 is controlled by a two-stage feedback loop of a position command and a speed command.

The position command is obtained by correcting the control command with the output of the encoder 26 and multiplying the gain command by the gain K1 to obtain a speed command. The speed command is corrected by a value (rotation speed) obtained by differentiating the output of the encoder 26. The current command is obtained by multiplying the gain K2. The current command is corrected by a sine wave advanced in phase by the current phase compensation amount obtained from the rotation speed, further corrected by the voltage compensation amount similarly obtained from the rotation speed, multiplied by a gain K3, and A predetermined current is supplied from 10e, 10g, and 10f.

Next, the speed command is corrected by the speed feedback so that the rotation speed of the motor 20 to be controlled matches the speed command obtained from the position command.

Further, in the position feedback, the position command is corrected such that the rotational position of the motor 20 controlled by the speed feedback coincides with the position command obtained from the command position.

As described above, by controlling, even if the rotational speed reading becomes high, the delay of the phase of the current that actually flows with respect to the rotational position of the control motor 20 is eliminated, and no invalid current flows, and the efficiency is improved. A reduction in current due to the induced voltage is eliminated, and a desired torque can be obtained.

As a result, heat generation due to the reactive current of the control motor 20 is eliminated.

In addition, since it is not necessary to perform current feedback, the configuration can be simplified.

Furthermore, in the present embodiment, when calculating the current phase compensation amount and the voltage compensation amount, the logically calculated delay θ and the induced voltage Em
In addition, since data obtained experimentally is used, compensation for phase delay and compensation for current drop due to induced voltage can be performed more reliably.

[Effects of the Invention] In the servo motor control device of the present invention, the phase of the current command value is advanced in advance by an amount corresponding to the delay due to the rotation speed in accordance with the rotation speed of the servo motor, and the current command value is reduced by the induced voltage. Is increased by an amount corresponding to the decrease in current caused by the above.

Therefore, even if the rotation speed is increased, the phase of the current that actually flows with respect to the rotation position of the servomotor is not delayed, and an invalid current does not flow, thereby improving the efficiency.
As a result, heat generation due to the reactive current of the servomotor is eliminated.

In addition, even if the rotation increases, the current that actually flows due to the induced voltage does not decrease, so that a desired torque can be obtained, and it is not necessary to perform feedback control of the current, so that the configuration is simplified. That is, since the feedback control of the current which requires the fastest control can be omitted, the load on the device can be reduced, and the system can be constructed with a cheaper and simpler configuration.

Further, the delay of the phase of the current with respect to the rotation speed is stored in advance in the current phase storage unit, and the amount of decrease in the current due to the induced voltage generated according to the rotation speed is stored in advance in the current decrease amount storage unit. Therefore, the configuration required for estimating the current phase compensation amount and the voltage compensation amount is simplified, and
Either of these is estimated in a short time, whereby the correction of the current command value is quickly performed, and high-speed response is ensured.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is a flowchart for explaining the operation thereof, FIG. FIG. 5 (A) is a diagram showing the relationship between the rotation speed and the current phase compensation amount used for it, FIG. 5 (B) is a diagram showing the relationship between the rotation speed and the voltage compensation amount used therefor, and FIG. The figure is an explanatory view of a conventional problem. M1,20: Servo motor (control motor) M2, 26: State detection means (encoder) M3: Current command value calculation means M4: Servo motor drive means M5: Current compensation amount determination means M6: Voltage Compensation amount determination means M7: Current command value correction means 10: Controller

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H02P 5/408-5/412 H02P 7/628-7/632 H02P 21/00

Claims (1)

(57) [Claims] 1. A servo motor control device for controlling a current supplied to a servo motor so as to operate the servo motor in accordance with an operation command, comprising: state detecting means for detecting a rotation position and a rotation speed of the servo motor; Current command value calculating means for calculating a current command value to be supplied to the servomotor using the detected rotational position, rotational speed and the operation command; and a servomotor based on the calculated current command value. A servo motor driving means for controlling a current supplied to the motor, and a current stored in advance in which a relationship between a rotation speed of the servo motor and a phase shift of the current with respect to a current command value generated according to the rotation speed is stored in advance. A phase storage means, and a current phase compensation amount for the detected rotation speed based on the relation stored in the current phase storage means. Means for determining current compensation amount to be determined; current reduction amount storage means for storing in advance the relationship between the rotation speed of the servomotor and the amount of current reduction due to the induced voltage generated according to the rotation speed; Voltage compensation amount determining means for determining a voltage compensation amount for speed based on the relationship stored in the current decrease amount storage means; and the current command value is determined by the determined current phase compensation amount and voltage compensation amount. And a current command value correcting means for correcting.