JPH07284286A - Torque ripple compensation system of servo motor - Google Patents

Abstract

PURPOSE:To provide a system for compensating torque ripples of a servo motor without increasing the gain of a 4 speed loop compensator. CONSTITUTION:In the control of a servo motor, a torque ripple T1 of a servo motor is compensated by compensating a torque command Tc by a torque command control part 6 provided in a speed loop with a speed loop compensator 1. And in the torque command compensation by the torque command control part 6, an amount equivalent to the torque change by the torque ripple T1 is compensated by the torque command Tc generated by the speed loop generator 1. The torque ripple of the servo motor is compensated by the compensation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servomotor control system, and more particularly to a servomotor which reduces ripples caused by a servomotor in a feed shaft of a machine tool, thereby reducing feed unevenness caused by the ripple. Torque ripple correction method.

[0002]

2. Description of the Related Art In a servo motor, a driving force is obtained by changing a magnetic flux relationship between a rotor and a stator according to mutual positions. For example, in a servomotor such as a variable reluctance type servomotor, salient poles are provided on a rotor and a stator, an exciting current is applied to the exciting windings wound around the salient poles of the stator, and the stator salient poles on which the exciting current flows The generated magnetic attraction force attracts the salient poles of the rotor, thereby obtaining the rotational force of the motor. The rotation of the motor is performed by determining the exciting phase (exciting stator salient pole) according to the rotor salient pole position and the stator salient pole position, which are the rotor phases (rotational positions), and sequentially switching the exciting phases. ing. As described above, since the servo motor controls excitation of each phase by switching between excitation and non-excitation, the nonlinearity is basically strong, and the excitation current and the output torque are not proportional. Further, even if the same value of exciting current is applied, the force of attraction of the stator salient poles by the stator salient poles differs depending on the rotor phase, so that torque ripple occurs. Due to this torque ripple, the generated torque differs depending on the rotor phase, and the torque value cannot be made constant. The torque ripple generated in this servo motor causes unevenness in speed and position deviation of the servo motor, which causes a problem that uneven feeding occurs in the feed shaft of the machine tool. Conventionally, in order to solve such a problem, in the control of the servo motor, the torque ripple is treated like the disturbance torque, and the influence of the torque ripple is suppressed by the disturbance suppression function by setting the gain of the speed loop compensator to be high. Is decreasing.

FIG. 20 is a block diagram for explaining a control loop of a conventional servo motor position control system. In FIG. 20, 4 is a position control unit and Kp is a position loop gain. Further, 1 is a velocity loop compensator, k1 is an integral gain,
k2 is a proportional gain. 2 is the torque constant Kt,
Reference numeral 3 is a motor / mechanical system, and 5 is a term for obtaining a position by integrating speed. Then, the output of the motor / mechanical system 3 is negatively fed back as the speed feedback vfb, and is input to the speed loop compensator 1 together with the speed command Vcmd. Is formed. Further, the position output of the item 5 is negatively fed back as position feedback, and is input to the position control unit 4 together with the position command θd to form a position loop. The position detected by the position detector or the like is subtracted from the position command to obtain the position deviation, the position deviation is multiplied by the position loop gain Kp to obtain the speed command vcmd, and the actual speed detected by the speed detector or the like from the speed command. The velocity vfb is subtracted to obtain the velocity deviation, the velocity deviation is integrated, and a value obtained by multiplying the integrated value by the integral gain k1 is added to obtain the torque command (current command) Tc (hereinafter referred to as torque command). It is common practice to drive the servomotor based on the torque command Tc (and also by performing current loop control). In addition, control of a servo motor that does not perform position loop control but only velocity loop control is generally performed.
The torque ripple is similar to the disturbance torque, and the integral gain k1 and the proportional gain k2 of the speed loop corrector 1 are
It is reduced by the disturbance suppression function by increasing the gain of.

[0004]

In the conventional method of increasing the gain of the speed loop compensator in the speed loop to reduce the torque ripple, the speed loop correction is performed, for example, when the rigidity of the mechanical system connected to the motor is low. Since there is a possibility of causing machine resonance by increasing the gain of the speed regulator, there is a limit to the effect of reducing the torque ripple by increasing the gain of the speed loop compensator, and there is a problem that sufficient reduction of the torque ripple cannot be obtained. is there. Therefore, the present invention solves the problems of the torque ripple correction method of the conventional servo motor described above, and provides a method that can correct the torque ripple of the servo motor without increasing the gain of the speed loop corrector. The purpose is to

[0005]

In the control of a servomotor, the present invention corrects a torque command by a torque command control unit provided in a speed loop having a speed loop compensator, and the servomotor is corrected by the torque command correction. The torque command correction by the torque command controller compensates for the torque change corresponding to the torque ripple from the torque command generated by the speed loop compensator. The torque ripple correction is performed. The torque command control unit used for the torque ripple correction of the servo motor of the present invention captures the change of the torque ripple as the change of the torque constant, and the correction of the torque command by the torque command control unit is the change of the torque constant due to the torque ripple. This can be done by obtaining the rate and multiplying the torque command by a coefficient determined by the obtained rate of change of the torque constant. This torque command control unit can store the rate of change of the torque constant used for the correction of the torque command in the form of a table, and can input / output to / from the table using the rotor phase of the motor and the torque command as variables. You can In addition, the torque command control unit can hold the rate of change of the torque constant used to correct the torque command as an arithmetic expression determined by the peak value of the torque ripple and the cycle, and obtain the rotor phase of the motor and the torque command as variables. You can Further, the torque command control unit used for correcting the torque ripple of the servo motor of the present invention catches the change of the torque ripple as the change of the generated torque, and the correction of the torque command by the torque command control unit corresponds to the torque ripple. This can be done by obtaining the generated torque and correcting the torque command from the torque command so as to compensate for the torque change equivalent to the torque ripple.

[0006]

According to the present invention, as described above, the torque command control section is provided in the speed loop including the speed loop compensator, and the torque command control section controls the torque command generated by the speed loop compensator. The object of the present invention is achieved by correcting the torque command so as to compensate for a torque change equivalent to the torque ripple. FIG. 1 is a block diagram of a speed loop of a position control system of a servo motor to which the torque ripple correction method for a servo motor of the present invention is applied. In FIG. 1, 1 is a velocity loop compensator, k1 is an integral gain, and k2 is a proportional gain.
2 is a torque constant Kt, and 3 is a term of a motor and a mechanical system. Further, 6 is a torque command control unit for correcting the torque command in the torque ripple correction method of the servo motor of the present invention. Then, the motor and mechanical system 3
Output negatively as velocity feedback vfb,
It is input to the speed loop compensator 1 together with the speed command Vcmd, and the speed loop compensator 1, the torque command controller 6, the torque constant 2, the motor, and the mechanical system 3 form a speed loop. Note that in FIG. 1, only the velocity loop is shown, and the position loop shown in FIG. 20 is omitted.

In a position loop (not shown), the position deviation detected by subtracting the position detected by a position detector or the like from the position command, and the speed command vcmd is calculated by multiplying the position deviation by the position loop gain, and the speed loop is calculated. Sent. Then, in the speed loop shown in FIG. 1, the actual speed vfb detected by the speed detector or the like is subtracted from the speed command vcmd by the speed feedback to obtain the speed deviation, the speed deviation is integrated, and the integrated value is integrated gain. k1
A loop for forming a torque command (current command) Tc (hereinafter referred to as a torque command) is formed by adding values multiplied by. In a servo motor, torque ripple (hereinafter referred to as torque ripple Tl) is a rotor phase θ that is a spatial positional relationship between a rotor magnet of the servo motor and an electric winding.
And the current value I flowing in the electric winding, the torque ripple Tl can be treated as Tl.
It can be represented as (θ, I). When the torque command control unit 6 is not provided, the torque value generated by the motor (hereinafter referred to as torque Tm) is the torque value on the input side of the motor and mechanical system 3 in the speed loop of FIG. Using (θ, I), the following equation (1)
Can be expressed as Tm = Kt · Tc + Tl (θ, I) (1) On the other hand, when the torque ripple correction method of the servo motor of the present invention is applied to the torque Tm, the torque command Tc is corrected by the torque command control unit 6. Then, the corrected torque command Tc ′ is obtained, and the torque Tm is expressed by the following equation (2). Tm = Kt · Tc ′ + Tl (θ, I) (2) Then, the torque command correction of the correction torque command Tc ′ is, for example, the torque ripple Tl (θ, I) as shown in the following equation (3). Can be represented by a correction term A that compensates for Tc ′ = Tc · (1 + A) (3) In this case, the torque Tm is: Tm = Kt · Tc · (1 + A) + Tl (θ, I) (4) = Kt · Tc + Kt · Tc · A + Tl (θ, I) ) (5), the second term in the equation (5) is obtained by the correction by the correction term A
The torque ripple Tl (θ, I) can be corrected by setting the item as Kt · Tc · A + Tl (θ, I) = 0.
Therefore, the torque command control unit 6 corrects the torque command Tc by forming the correction term A such that A = −Tl (θ, I) / Kt · Tc (6), and the corrected torque command Tc ′ is obtained. Is output.

Here, since the current value I can generally be set as the torque command Tc, the torque command control unit 6
Can be represented by the block diagram shown in FIG. 2, and the corrected torque command Tc ′ is obtained with the torque command Tc and the rotor phase θ as variables. Next, the procedure of torque ripple correction of the servo motor by the speed loop shown in FIG. 1 will be described with reference to the flowchart of FIG. 3 showing the torque ripple correction of the servo motor of the present invention. Note that the flowchart of FIG. 3 is described according to the reference numeral of step S. First, the torque command Tc is calculated in the speed loop compensator (step S1). The calculation in this speed loop compensator is similar to the processing in the speed loop compensator in the conventional speed loop, and the speed command v
The cmd and the velocity feedback vfb are input to obtain the deviation, and the torque command Tc is obtained by adding the value obtained by integrating the deviation by the integral gain k1 and the value obtained by multiplying the deviation by the proportional gain k2.

Next, the rotor phase θ is fetched (step S2). The acquisition of the rotor phase θ can be obtained, for example, from the value of a pulse coder attached to the motor shaft. By the processes of steps S1 and S2, the torque command Tc and the rotor phase θ, which are variables for obtaining the correction torque command Tc ′, are obtained. Therefore, in step S3, the torque command T
A correction term is obtained using c and the rotor phase θ. This correction term can be obtained, for example, from the relationship of the equation (6). Next, the correction torque command Tc 'is calculated using the correction term obtained in step S3 (step S4). The calculation of the correction torque command Tc ′ can be performed by, for example, the calculation represented by the equation (6), and the correction represented by the equation (3) that compensates the torque ripple Tl (θ, I). The torque command Tc 'can be obtained. Then, the correction torque command Tc ′ obtained in step S4 is passed to the current loop (step S5), and the processing of steps S1 to S5 is performed for each speed loop to drive the motor. Therefore, in the torque ripple invention method of the present invention, a correction torque command for compensating the torque ripple is formed for each speed loop,
With this correction torque command, the drive of the servo motor can be controlled so as to suppress the torque ripple itself.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. [Servo Motor Control System for Implementing the Present Invention] First, a servo motor position control system for implementing the present invention will be described. FIG. 4 is a block diagram of a main part of servo motor control of a machine according to an embodiment for implementing the servo motor control method of the present invention. In the figure, 10 is a control device such as a numerical control device for controlling a machine, 11 is a device for receiving various commands and the like output from the control device 10 to a servo motor, and passing them to a processor of a digital servo circuit 12. Shared memory, 12 is a digital servo circuit, processor, R
It is composed of an OM, a RAM, etc., and performs processing of position, speed, and current control of the servomotor 14 by a processor. 13 is a servo amplifier including an inverter,
Reference numeral 14 is a servo motor, 15 is a rotational position and speed of the servo motor 14, and the position of the digital servo circuit 12 is detected.
A position / speed detector that feeds back the speed.

First Embodiment of Torque Ripple Correction of the Present Invention Next, a configuration diagram of a first embodiment of torque ripple correction of the present invention will be described. The configuration diagram of the first embodiment is the same as that shown in FIG.
The detailed description is omitted because it is the same as the block diagram of the speed loop of the position control system of the servo motor to which the torque ripple correction method for the servo motor of the present invention shown in FIG. In FIG. 1, the speed loop compensator 1 outputs a negative feedback speed feedback vfb and a speed command Vcmd as inputs, and outputs a torque command Tc to the torque command control unit 6. The torque command control unit 6 corrects this torque command Tc and outputs a corrected torque command Tc '. Then, the correction torque command Tc ′ is the torque constant 2
After the torque is set to Tm by, the torque is fed back to the speed loop compensator 1 via the motor / mechanical system 3 to form a speed loop. In FIG. 1, only the speed loop is shown. In the servo motor, the torque ripple Tl depends on the rotor phase θ, which is the spatial positional relationship between the rotor magnet of the servo motor and the electric winding, and the current value I flowing through the electric winding, and Tl (θ, I) Can be expressed as

If the torque command controller 6 is not provided,
The torque value Tm generated by the motor is the torque value on the input side of the motor and mechanical system 3 in the speed loop, and the torque constant 2
Can be represented by the above-mentioned equation (1) as the sum of the output of the above and the torque ripple Tl (θ, I).

Tm = KtTc + Tl (θ, I) (1) Since the current I and the torque command Tc can generally be set substantially equal to each other, the torque value Tm of the above equation (1) can be calculated by the following equations (7), ( It can be represented by 8). Tm = Kt · Tc + Tl (θ, Tc) (7) = Kt · (Tc + Tl (θ, Tc) / Kt) = Kt · Tc (1 + Tl (θ, Tc) / Kt · Tc) (8) where Letting some of the terms in the equation (8) be Tl (θ, Tc) / Kt · Tc = α (θ, Tc) (9), the equation (8) is expressed by the following equation (10). To be done. Tm = Kt · Tc (1 + α (θ, Tc)) (10) The above expression (10) is compared with the case where the torque value Tm or the torque constant Kt has no torque ripple because the torque ripple is added. It is shown that it can be seen that the value becomes (1 + α (θ, Tc)) times, and this α (θ, Tc) can be regarded as the rate of change of the torque constant.

Therefore, in the torque command control unit 6, the torque command Tc generated by the speed loop compensator is expressed by (1 / (1 + α) as shown in the following equations (11) and (12).
(Θ, Tc)) times or (1-α (θ, T
The correction torque command Tc ′ can be obtained by multiplying c)). If α is sufficiently small, (1
+ Α (θ, Tc)) = (1−α (θ, Tc)). Tc ′ = Tc / (1 + α (θ, Tc)) (11) Tc ′ = Tc · (1-α (θ, Tc)) (12) The torque value Tm is calculated using this correction torque command Tc ′. Then, Tm = Kt · Tc · (1 / (1 + α (θ, Tc))) · (1 + α (θ, Tc)) = Kt · Tc, and the torque ripple can be compensated.

Further, the correction torque command T of the equation (11)
When c ′ is rewritten using the relationship of the equation (10), it can be expressed by using the torque value Tm as Tc ′ = Tc ² · Kt / Tm (13) = 2Tc−Tm / Kt (14) , This correction torque command T
Similarly, when the torque value Tm is obtained using c ′, T
m = Kt · Tc · Torque ripple can be compensated.

The correction term A expressed by the above equation (3)
When using the change rate α of the torque constant, (-α /
(1 + α)) or (−α), and when the torque value Tm is used, (Tc · Kt / Tm−1),
Alternatively, it is (2Tc-Tm / Kt-1). In the first embodiment of the present invention, the processing in the torque command control unit 6 is performed by the correction term in the form of a table, and the correction term is held in advance in the form of a table, and the torque command Tc and the rotor are stored from this table. The phase θ is read as a variable, and the torque command Tc is corrected by the read correction term to form a corrected torque command Tc ′.

Next, the configuration of the torque command controller used in the first embodiment of the present invention will be described with reference to FIG. 5, and its operation will be described with reference to the flowcharts of FIGS. 6 and 7. In FIG. 5, a portion surrounded by a broken line is the torque command control unit 6 in FIG. 1, which receives the torque command Tc and the rotor phase θ as variables and outputs the corrected torque command Tc ′. The torque command control unit 6 has a table in which the correction term is stored, and the torque command Tc
With the rotor phase θ as a variable, a correction term is output. The flowcharts of FIGS. 6 and 7 show the steps of only the torque command control unit 6, and in the flowchart showing the processing for each speed loop shown in FIG.
3 and step S4 are shown. The flowchart of FIG. 6 is for the case of using the rate of change α of the torque constant, and the flowchart of FIG. 7 is for the case of using the torque value Tm.

First, the case where the torque command is corrected using the change rate α of the torque constant will be described with reference to the flowchart of FIG. After reading the torque command Tc and the rotor phase θ obtained in steps S1 and S2 as described above (step S31), the change rate α of the corresponding torque constant from the table using Tc and θ as variables.
(Θ, Tc) is read and obtained (step S32).
Therefore, the change rate α (θ, Tc) of the torque constant with respect to Tc and θ is calculated and stored in advance in the table. Then, the obtained rate of change of the torque constant α (θ, Tc)
The correction torque command Tc 'is calculated by using. This calculation is performed by using the above equation (11) or equation (12). Next, a case where the torque command is corrected using the torque value Tm will be described with reference to the flowchart of FIG. 7. As described above, after the torque command Tc and the rotor phase θ obtained in steps S1 and S2 are read (step S31), the corresponding torque value Tm is read from the table by using Tc and θ as variables (step S33). . Therefore, the torque value Tm for Tc and θ is obtained and stored in the table in advance. Then, the correction torque command Tc ′ is calculated by using the calculated torque value Tm. In this calculation, the above equation (13) or equation (14)
Using. In this case, equations (13) and (14)
The torque constant, which is Kt, is input in advance.

Next, regarding the configuration example of the torque ripple correction table used in the first embodiment of the present invention, the configuration diagram shown in FIG. 8 and the diagrams for explaining the creation of the torque ripple correction table shown in FIG. 9 and FIG. It demonstrates using. In the configuration diagram of the torque ripple correction table in FIG. 8, the torque command Tc and the rotor phase θ shown by solid lines are used as input variables,
Rate of change of torque constant stored in the table α (θ, T
c) Alternatively, the torque value Tm is read out, and the value is applied to the equations (12) to (14) to correct torque command T.
Find c '. In the table, for example, θ ₁ , θ ₂ , and θ of different rotor phases θ are set for values Tc ₁ , Tc ₂ , Tc ₃ , ... Of certain torque commands Tc.
Change rate of torque constant α (θ, Tc) for ₃ , ...
Α ₁₁ , α ₁₂ , α ₁₃ , ..., α ₂₁ , α ₂₂ , α ₂₃ , ...
・ Stored as, and the torque value Tm is Tm ₁₁ , Tm
₁₂ , Tm ₁₃ , ..., Tm ₂₁ , Tm ₂₂ , Tm ₂₃ , ...
It stores like this. In the storage in this table, the rate of change of the torque constant α (θ, Tc) or the torque value Tm is previously obtained for the values of the torque command Tc and the rotor phase θ, and the value is stored in a memory or the like. Can be done by.

The value stored in this table may be either the change rate α (θ, Tc) of the torque constant or the torque value Tm. Next, the creation of this torque ripple correction table will be described. The torque ripple correction table is created by obtaining the torque command Tc from the output of the speed loop compensator and the rotor phase θ from the output of the pulse coder as shown in the block diagrams of FIGS. 9 and 10 (solid line in the figure). ) On the other hand, the torque value Tm at this time is obtained (broken line in the figure), and the rate of change of the torque constant α (θ, Tc) is calculated from the relationship of the equation (10).
Then, the table can be created by storing the change rate α (θ, Tc) of the torque constant or the value of the torque value Tm in the memory using the torque command Tc and the rotor phase θ as addresses.

Second Embodiment of Torque Ripple Correction of the Present Invention Next, a second embodiment of torque ripple correction of the present invention will be described. The configuration of the second embodiment of the present invention is the same as that of the first embodiment.
The difference is in the calculation of the correction torque command Tc ′ in the torque command control unit. Therefore,
Below, only the calculation of the correction torque command Tc ′ in the torque command control unit will be described.

In the first embodiment of the present invention, in the processing in the torque command control unit 6, the correction term is held in the form of a table, and the torque command Tc is stored from this table.
And the rotor phase θ as variables, the torque command Tc is corrected by the read correction term to form the corrected torque command Tc ′, whereas in the second embodiment of the present invention, the processing in the torque command control unit 6 is performed. In the equation for calculating the torque constant α, the torque command Tc
And the rotor phase θ as variables, and the torque command Tc is corrected by the calculation of this arithmetic expression to form the corrected torque command Tc ′.

The constituent blocks of the torque command controller used in the second embodiment of the present invention will be described below with reference to FIG.
The operation will be described with reference to the flowchart of FIG.
In FIG. 11, the portion surrounded by the broken line is the torque command control unit 6 in FIG. 1, which receives the torque command Tc and the rotor phase θ as variables, calculates the correction term α, and outputs the corrected torque command Tc ′. It is a thing. The torque command control unit internally has an arithmetic expression for the rate of change of the torque constant, calculates the arithmetic expression using the torque command Tc and the rotor phase θ as variables, and outputs the correction term. The flowchart of FIG. 12 shows only the steps of the torque command control unit, and shows steps S3 and S4 in the flowchart showing the processing for each speed loop shown in FIG. First, after reading the torque command Tc and the rotor phase θ obtained in steps S1 and S2 as described above (step S31), this Tc is read.
And θ are used as variables to calculate an arithmetic expression of the rate of change of the torque constant to obtain a correction term (step S33). Therefore, the torque command control unit controls the rate of change of the torque constant α (θ, T
owns c) as an arithmetic expression. Then, the correction torque command Tc ′ is calculated by using the calculated change rate α (θ, Tc) of the torque constant (step S41). This calculation is performed by using the above equation (11) or equation (12).

(Example of Calculation Formula for Torque Ripple Correction of the Present Invention) Next, an example of the calculation formula for the above torque ripple correction will be described. The rate of change α of the torque constant used for torque ripple correction can be generally treated as a sine wave as shown in the explanatory diagram of FIG. 13, and can be expressed by the following equation (15). α (θ, Tc) = α (I) · cos (A · θ + ψ) (15) where α (I) is the peak value of the torque constant change rate,
A represents the period of the torque constant change rate, and α
By determining (I) and A, the rate of change α of the torque constant represented by the equation (15) can be determined. Hereinafter, an example of setting the torque constant change rate α will be described with respect to an arithmetic expression for torque ripple correction.

(Calculation Formula Example 1) A calculation formula example 1 for torque ripple correction is an example in which the torque ripple is measured and obtained from the peak value of the ripple and the number of ripples repeated in the electrical angle 2π. FIG. 14 is a diagram for explaining an example of a calculation formula for torque ripple correction, and FIG. 14A shows a case where the drive current is repeated for four cycles during one rotation of the motor. In this case, 1/4 rotation of the motor has an electrical angle of 2π. At this time, when the torque ripple as shown in (b) is generated, it means that six ripples having the peak value α (I) are generated within the electrical angle 2π. Therefore, in this case, A in the equation (15) is
Is 6, and the torque constant change rate α is represented by α (θ, Tc) = α (I) · cos (6 · θ + ψ) (15 ′).

(Calculation Formula Example 2) A calculation formula example 2 for torque ripple correction is an example in which torque ripple is measured, frequency analysis is performed on the torque ripple, and the result is obtained from the frequency analysis. FIG. 15 is a frequency analysis result of the torque ripple, and shows the number of ripples n during one rotation of the motor and its amplitude α. The amplitude α can be set to α (I) in the above equation (15), and the number of ripples n during one rotation of the motor is n.
Can be obtained as the number of ripples A in the electrical angle 2π by dividing the number of ripples n by 1/2 of the number of poles of the motor. For example, the number of ripples n during one rotation of the motor is 24
When the motor has 8 poles, the number of ripples A in the electrical angle 2π is (24 / (8/2)) = 6, and the above equation (1)
The torque constant change rate α similar to that of 5 ′) is determined. In the case of this arithmetic expression example 2, the torque ripple of the cycle to be reduced is selected from a plurality of ripples obtained from the frequency analysis result of the torque ripple, and the torque constant change rate α is determined for the torque ripple of the cycle. By performing the torque command correction based on the torque constant change rate α, it is possible to suppress the selected torque ripple.

[Examples] FIGS. 16 to 19 show examples, and FIG. 16 shows the feed unevenness when the torque ripple correction of the present invention is not performed during one rotation of the motor.
7 shows the result of ripple frequency analysis when the torque ripple correction of the present invention is not performed. Further, FIG. 18 shows the feed unevenness during one rotation of the motor when the torque ripple correction of the present invention is performed, and FIG. 19 shows the ripple frequency analysis result when the torque ripple correction of the present invention is performed. Shows. Then, the torque ripple correction performed in FIG. 19 is an example in which the above-described arithmetic expression example 2 is applied,
In the frequency analysis shown in FIG. 17, a periodic ripple having a wave number of 24 per rotation having the maximum amplitude is selected, and a torque constant change rate α corresponding to the ripple is obtained by the above-mentioned calculation expression example 2. As a result, as shown in FIG. 19, the peak value of the periodic ripple of 24 wave numbers per rotation can be reduced, and as shown in FIG. 18, the amount of uneven transmission can be reduced.

[0028]

As described above, according to the present invention, it is possible to provide a method capable of correcting the torque ripple of the servo motor without increasing the gain of the speed loop corrector.

[Brief description of drawings]

FIG. 1 is a block diagram of a speed loop of a position control system of a servo motor to which a torque ripple correction method for a servo motor of the present invention is applied.

FIG. 2 is a block diagram illustrating a torque command control unit.

FIG. 3 is a flowchart of torque ripple correction of the servo motor of the present invention.

FIG. 4 is a block diagram of a main part of servo motor control of a machine according to an embodiment that implements the servo motor control system of the present invention.

FIG. 5 is a block diagram of a torque command control unit according to the first embodiment of the present invention.

FIG. 6 is a flowchart of Embodiment 1 of torque ripple correction of the servo motor of the present invention.

FIG. 7 is another flowchart of Embodiment 1 of torque ripple correction of the servo motor of the present invention.

FIG. 8 is a table configuration diagram of torque ripple correction of the present invention.

FIG. 9 is a diagram for explaining how to create a torque ripple correction table according to the present invention.

FIG. 10 is a diagram illustrating the creation of a torque ripple correction table according to the present invention.

FIG. 11 is a block diagram of a torque command control unit according to the second embodiment of the present invention.

FIG. 12 is a flowchart of a torque ripple correction example 2 of the servo motor according to the present invention.

FIG. 13 is a diagram illustrating a calculation formula for torque ripple correction according to the present invention.

FIG. 14 is a diagram for explaining a calculation example 1 of the torque ripple correction of the present invention.

FIG. 15 is a diagram for explaining a calculation example 2 of the torque ripple correction of the present invention.

FIG. 16 is a diagram of uneven feed when torque ripple correction is not performed.

FIG. 17 is a frequency analysis result diagram of ripples when torque ripple correction is not performed.

FIG. 18 is a diagram of uneven feed when torque ripple correction according to the present invention is performed.

FIG. 19 is a frequency analysis result diagram of ripples when the torque ripple correction of the present invention is performed.

FIG. 20 is a block diagram illustrating a control loop of a conventional servo motor position control system.

[Explanation of symbols]

 1 speed loop compensator 2 torque constant 3 motor, mechanical system 6 torque command control unit Tc torque command Tc 'correction torque command Tm generated torque θ rotor phase α torque constant change rate

Claims (5)

[Claims] 1. In a servomotor control, a torque command control unit provided in a speed loop including a speed loop compensator corrects a torque command, and the torque command correction corrects a torque ripple of the servomotor. A torque ripple correction method for a servo motor characterized in that the torque command correction by the torque command controller compensates a torque change corresponding to a torque change due to a torque ripple from a torque command generated by a speed loop corrector. 2. The torque command control unit obtains a rate of change of a torque constant corresponding to a torque ripple, and multiplies the torque command by a coefficient determined by the rate of change of the torque constant to correct the torque command. Torque ripple correction method for servo motors. 3. The torque ripple correction method for a servo motor according to claim 2, wherein the rate of change of the torque constant is stored in a table having variables of a rotor phase of the motor and a torque command. 4. The torque ripple correction method for a servo motor according to claim 2, wherein the rate of change of the torque constant is calculated by an arithmetic expression determined by a peak value and a cycle of the torque ripple. 5. The torque ripple correction method for a servomotor according to claim 1, wherein the torque command control unit obtains a generated torque corresponding to the torque ripple and corrects the torque command based on the generated torque.