JPH07104857A - Digital servo controller - Google Patents

Abstract

PURPOSE:To suppress the speed fluctuation of a servo motor due to disturbance in the case of a digital servo control. CONSTITUTION:Disturbance torque in the next control cycle is predicted by the calculation by the same one-dimensional observer to a digital servo control system corresponding to a rotational angle detected by an angle detecting means from the present control period, the predictive value of the rotational angle, the predictive value of rotating angular velocity, the predictive value of the disturbance torque and the commanded target torque related value (300-302), and the predicted disturbance torque is amplified at an amplification factor in tendency to reduce the amplification factor when the rotational speed of the servo motor is high, and additively corrected to the target torque related value in the next control cycle (304-310).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital servo control device for digitally controlling an AC servomotor, and more particularly, it eliminates the influence of disturbance torque to prevent torque fluctuations and at the same time the torque of the servomotor during high speed rotation. It relates to the one that has further prevented fluctuation.

[0002]

2. Description of the Related Art Conventionally, a digital servo controller has a position feedback loop, a velocity feedback loop,
It has a current feedback loop. Then, in the speed feedback loop, the target current is calculated by the proportional / integral calculation of the speed deviation. Normally, the influence of disturbance is compensated by setting the integral time constant as small as possible, that is, by increasing the integral term.

[0003]

In recent years, digital servo control devices have been used for robot devices. In the case of a robot device, if the integration time constant is set short, a large low frequency vibration is induced at the tip of the robot when the robot operates at high speed. In order to prevent this, the integration time constant is set to be long, but the servo system is vulnerable to disturbance and the speed fluctuation becomes large. In order to solve this, the present applicant has filed Japanese Patent Application No. 5-98.
Filed No. 583. The present invention further eliminates the effects of disturbance torques in this application. That is, when the disturbance torque is predicted by the disturbance torque observer, the disturbance torque estimated to reduce the prediction error has the same effect as passing through the low-pass filter, and the high frequency component is removed. . However, during high speed operation, the frequency component of the disturbance torque becomes high, and the phase delay of the estimated value of the disturbance torque observer becomes large. In such a case, there is a problem that the controllability deteriorates.

The present invention has been made to solve the above problems, and an object thereof is to suppress speed fluctuations of a servo motor due to disturbance in digital servo control.

[0005]

The structure of the invention for solving the above-mentioned problems is to provide a servo controller for providing a target value for each feedback loop by a digital amount,
Based on the detected value detected by the detection means in the current control cycle, the predicted value of the disturbance torque in the current control cycle, and the commanded target torque-related value, the next control is performed by the observer for the digital servo control system. The disturbance torque in the next control cycle is predicted, and the disturbance torque predicted in the next control cycle is amplified by the amplification factor that tends to decrease when the rotation speed of the servo motor is high, and the target torque related in the next control cycle is related. The feature is that the value is added and corrected.

[0006]

The next control cycle is calculated by the observer for the digital servo control system from the detected value detected by the detecting means, the predicted value of the disturbance torque, and the commanded target torque-related value in the current control cycle. The disturbance torque at is predicted. The disturbance torque is amplified with an amplification factor that changes according to the rotation speed of the servo motor (target rotation speed or measured rotation speed). The change characteristic is a characteristic in which the amplification factor decreases when the rotation speed is high.
Then, the predicted disturbance torque corrected by the amplification factor in the next control cycle is added and corrected to the target torque related value in the next control cycle.

Therefore, the target torque-related value is added and corrected by the amount of the disturbance torque that is predicted to be generated in the next control cycle, and the corrected target torque-related value becomes the target current for the current feedback loop. . Further, when the rotation speed of the servo motor is high, the amplification factor becomes small, so that the correction amount of the target torque related value becomes small.
As a result, controllability during high speed operation is improved.

[0008]

As described above, according to the present invention, the disturbance torque generated in the next control cycle is predicted by the predictive calculation using the observer for the digital servo control system, and the target torque related value is added and corrected. , The current of the current feedback loop is controlled based on the correction value.
Therefore, when the disturbance torque is predicted to increase, the target torque-related value is largely corrected, and when the disturbance torque is predicted to be small, the target torque-related value is corrected to be small. Even if a disturbance torque is applied to, the speed fluctuation is suppressed. Further, during high-speed operation, the error of the disturbance torque predicted by the observer (prediction error between the predicted value and the actual value) increases, but at this time the predicted disturbance torque is reduced by changing the amplification factor, or It is zero. As a result, the controllability of the servo motor during high speed operation is improved.

[0009]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 is a block diagram showing the configuration of a digital servo control device according to the present invention. The digital servo control device 10 mainly includes the CPU 11 and the R
OM12, RAM13, digital signal processor (hereinafter referred to as "DSP") 14, common RAM17, C
PU23, A / D converters 15a, 15b, ROM20,
It is composed of a RAM 24 and a current value counter 16. A keyboard 21 and a CRT display device 22 are connected to the CPU 11 via an interface 19.

The DSP 14 performs calculation for position and speed control, the output of the DSP 14 is input to the CPU 23 for current control, the output of the CPU 23 is input to the inverter 25, and the inverter 25 servos according to the output signal of the CPU 23. The motor 31 is driven. A synchronous motor is used as the servo motor 31, and the load voltage of the servo motor 31 is controlled by the PWM voltage control of the inverter 25, and as a result, the output torque is controlled.

The u-phase and v-phase load currents of the servomotor 31 are detected by the current transformers CT32a, 32b and amplified by the amplifiers 18a, 18b.
The outputs of the amplifiers 18a and 18b are the A / D converter 15
It is input to a and 15b, sampled at a predetermined cycle, and converted into a digital value. The sampled value is C as a feedback value of the instantaneous load current.
Input to PU23. Further, a pulse encoder 33 is connected to the servo motor 31, and its current position (current rotation angle) is detected. The output of the pulse encoder 33 is connected to the current value counter 16 via the waveform shaping / direction discrimination circuit 34.

The output signal from the pulse encoder 33 input to the current value counter 16 via the waveform shaping / direction discriminating circuit 34 adjusts the value of the current value counter 16. D
The value of the current value counter 16 is read by the SP 14 as a current position feedback value, and the DSP 14
The position deviation (angle deviation) is calculated by comparing with the target value (target rotation angle) output from the CPU 11. And DS
In P14, the speed target value (rotational angular speed target value) is calculated based on the position deviation.

The current position feedback value input to the DSP 14 is differentiated to calculate the speed feedback value. The DSP 14 compares the speed target value determined according to the position deviation with the speed feedback value to calculate the speed deviation (rotational angular speed deviation), and calculates the current target value based on the speed deviation.

On the other hand, the load currents detected by the CTs 32a and 32b are the amplifiers 18a and 18b and the A / D converter 1.
Input to the CPU 23 via 5a and 15b. And
As will be described in detail later, the rotation angle detected in the current control cycle, the rotation angle predicted value, the rotation angular velocity predicted value,
The disturbance torque in the next current control cycle is predicted and calculated based on the predicted value of the disturbance torque and the commanded target torque-related value. The target torque-related value commanded in the next current control cycle is added and corrected by the predicted disturbance torque. Most specifically, the target torque-related value is a target current. At this time, when the rotation speed of the servo motor 31 exceeds a predetermined threshold value, the estimated disturbance torque is set to zero.

Then, the CPU 23 compares the current target value with the current feedback value to calculate the current deviation. The instantaneous current command value at that current control time is calculated based on the instantaneous current deviation at that time, the cumulative value of the instantaneous current deviation, and the current target value, that is, by the proportional integral calculation.
The instantaneous current command value is compared with a high frequency triangular wave, and a voltage control PWM signal for controlling on / off of each phase transistor of the inverter 25 is generated.

The voltage control PWM signal is sent to the inverter 2
5, and the transistors of each phase of the inverter 25 are driven. By the switching of the inverter 25, the load current of each phase is controlled to the current target value. The positioning of the servo motor 31 is C
When the PU 11 determines that the output value of the current value counter 16 becomes equal to the target position value, the process is completed.
The u-phase and v-phase load current values sampled by the A / D converters 15a and 15b are dq converted by the CPU 23.

As described above, the digital servo controller of this embodiment is composed of three feedback loops of position, velocity and current. A lower feedback loop requires higher responsiveness, for example, the lowest current feedback loop is 100 μs,
The velocity feedback loop is several times as long as the position feedback loop, and the position feedback loop is further synchronously sampled at time intervals, and the processing of each feedback loop is executed.

Next, the operation of the apparatus of this embodiment will be described. FIG. 2 is a flowchart showing a program executed by the CPU 11 stored in the ROM 12.
In the state before this program is executed, the servo motor 31 is in a stopped state.

In step 200, one block of movement command data is read from the RAM 13, and step 2
In 02, the acceleration / deceleration flag in the flag area of the RAM 13 is turned on. Next, in step 204, the interpolation target position (interpolation target rotation angle) in the acceleration region for accelerating the servo motor 31 from the stopped state to the commanded constant speed is calculated, and the interpolation target position is momentarily stored in the common RAM 17. It is output and stored there.

Next, when the acceleration is completed, step 206
In step 20, the acceleration / deceleration flag is turned off, and the next step 20
8, the constant speed flag in the flag area of the RAM 13 is turned on. Next, in step 210, the interpolation target position in the constant speed region is calculated, and the interpolation target position is output to the common RAM 17 every moment and stored therein.

Next, at step 212, it is judged whether or not the movement command data of one block includes a command for temporarily stopping at the command target position. If the stop instruction is not given, the movement instruction data of the next block is input in step 214, and the interpolation target position in the constant velocity region is calculated in step 210. Step 21
By repeating 0 and 214, the target position can be sequentially updated at a constant speed, and the interpolation target position can be sequentially output.

When it is determined in step 212 that the movement command data includes a temporary stop command, the acceleration / deceleration flag is turned on in step 216, and the constant speed flag is turned off in step 218. Then, in step 220, the interpolation target position in the deceleration area is sequentially calculated, and the interpolation target position is momentarily shared by the common RAM.
It is output to 17 and stored there.

Next, after the deceleration interpolation is completed, the servo lock flag in the flag area of the RAM 13 is turned on in step 222 to indicate that the servo lock state is established. Then, in step 224, the same target position is output momentarily to the common RAM 17, and the target position is stored therein. As a result, the servo motor 31 is held at the same position in the servo lock state, that is, in the energized state.

After the temporary stop for the time instructed by the movement command data is completed, the process returns to step 200, the movement command data of the next block is read, and the position control of the servo motor is performed in the same manner as the above-mentioned step. Be seen. In this way, the position of the servo motor is commanded.

Next, the DSP 14 executes the program of FIG. 3 stored in the ROM 20, and the CPU 23 makes the ROM 23.
4 is executed and the position, speed and torque of the servo motor 31 are controlled. The programs of FIGS. 3 and 4 are repeatedly executed by the DSP 14 and the CPU 23 at each predetermined minimum cycle.

In step 100, it is judged whether or not the current execution cycle is the position deviation calculation timing.
The target position θ (i) (interpolation target rotation angle) commanded at that time from M by the CPU 11 is input and stored. Further, the target position within the past fixed time is stored in the common RAM 17.

Next, at step 104, the current position (electrical angle) θa (i) held in the current value counter 16 is read. Next, in step 106, the current time (i)
Position deviation Δθ between the target position θ (i) and the current position θa (i)
(i) is calculated. Next, at step 108, the target speed V (i) is calculated by a value proportional to the position deviation ΔP (i), that is, the following equation.

## EQU1 ## V (i) = k.ΔP (i)

The feedback control of the above position is shown in FIG.
Is executed at the timing indicated by the signal S1.

Next, at step 110, it is judged if the current execution cycle is the speed deviation calculation timing.
If it is the speed deviation calculation tamming, the routine proceeds to step 112, where the current position θa (n) held in the current value counter 16 is read. Next, the process proceeds to step 114 and the current time
The current speed Va (n) (current rotational angular speed) at (n) is calculated. The current speed Va (n) is calculated by the following equation based on the current position θa (n-1) read at the previous speed deviation calculation timing, the current position θa (n) input this time, and the speed control cycle D. Is calculated by

[0030]

[Formula 2] Va (n) = (θa (n) -θa (n-1)) / D

Next, at step 116, the target speed V (i) calculated at step 108 (target rotational angular speed)
And the current speed Va (n), that is, the speed deviation ΔV (n) is calculated. Also, the cumulative value (integration) S of the speed deviation ΔV (n)
Is calculated by S = S + ΔV (n).

Next, in step 118, step 1
16. The speed deviation ΔV (n) and the integration S of the speed deviation calculated in 16 and the integration time T set corresponding to the proportional gain K _p and the target speed V (i) set in the common RAM 17
_{Using i} and _i , the q-axis component of the target current (active current, which is proportional to the tokdle of the servomotor) Iq (n) is calculated by the following equation. The d-axis component (reactive current) of the target current is 0.

[0033]

## EQU3 ## Iq (n) = K _p (ΔV (i) + S / T _i ).

Next, at step 119, the disturbance torque T _L in the nth control cycle is calculated by the same-dimensional observer.
(n) 'is calculated. The prediction calculation by the same dimension observer is executed according to the program shown in FIG. Prior to performing the prediction calculation, the servo motor 31 and the pulse encoder 33 can be modeled as shown in FIG. That is, the following relationship is established among the disturbance torque T _L , the target current Iq, the inertia moment J _m of the servo motor 31, the inertia moment J _{L of the} load, the rotational angular velocity ω and the rotational angle θ.

[0035]

## EQU4 ## K _tn Iq −T _L = (J _m + J _L ) S ² θ where K _tn is a torque constant. Figure 8 based on the above formula
And create the equation of state,

[0036]

[Equation 5] However, J = J _m + J _L This equation is discretized, and the prediction operation is performed by the equation (Equation 7 below) that constitutes the same-dimensional observer.
In step 300 of FIG. 6, the previous time, that is, the (n-1) th
The error in the control cycle is calculated by the following equation.

[0037]

## EQU00006 ## e (n-1) =. Theta. (N-1) '-. Theta.a (n-1) where e (n-1), .theta. (N-1)' and .theta.a (n-1) are These are the error in the (n-1) th control cycle, the predicted calculation value of the rotation angle, and the measured value of the rotation angle, respectively. Where θ (n-1) 'is the initial value θ (1)'
Does not need to be specified, but is usually the same as the measured value θa (1).

Next, in step 302, the above equation 5
The target current Iq (n-1) in the (n-1) th control cycle and the predicted value θ (n-
1) ', the predicted value ω (n-
1) ', predicted value of disturbance torque T _L (n-1)' and error e (n-1)
From, the predicted value θ (n) ′ of the rotation angle in the nth control cycle,
The predicted value ω (n) ′ of the rotational angular velocity and the predicted value T _L (n) ′ of the disturbance torque, which are the time derivatives thereof, are calculated.

[0039]

[Equation 7]

[0040] However, t is the sum of the time interval, J is the moment of inertia J _L of the load and inertia moment J _m of the servo motor rotor between the first n-1 control cycle and the n-th control cycle, K
_tn is a torque constant.

Next, at step 304, it is judged if the current speed Va (n) calculated at step 114 is larger than a predetermined threshold Vth, and the current speed Va (n) is larger than the predetermined threshold Vth. If it is larger, the amplification factor G ₀ is set to 0 in step 306, and step 310 is executed.
When the current speed Va (n) is smaller than the predetermined threshold value Vth, the amplification factor G ₀ is set to the predetermined value Gt in step 308, and step 310 is executed.

In step 310, the target current Iq (n) output by the speed feedback loop in the nth control cycle is output.
Is the current component T corresponding to the predicted value T _L (n) 'of the disturbance torque
_L (n) '/ K _tn gain G ₀ times _{(G 0 × T L (n} )' / K tn) are only additive correction, the corrected target current Iq (n) ^* is calculated. Then, in step 312, the correction target current Iq (n) ^* becomes the current control target of the current feedback loop. In this way, the DSP 14 repeatedly executes the speed control in the speed control cycle. This speed feedback control is executed at the timing shown by the signal S2 in FIG.

The current control CPU 23 executes the program shown in FIG. In step 120, it is determined whether the current execution cycle is the current deviation calculation timing.
If it is the current deviation calculation timing, the routine proceeds to step 122. Step 122 and subsequent steps are current feedback control, and this control is executed at the timing shown by signal S3 in FIG. In step 122, the current detection time Δt ₁ measured from the beginning of the current control period, the load current control time Δt ₂ measured from the beginning of the current control period, and the current speed V.
The current detection electrical angle θ ₁ and the control electrical angle θ _{2 which} are the electrical angles corresponding to the time are interpolated using a (n).

[0044]

[Equation 8] θ ₁ = θa (n) + Va (n) · Δt ₁

[Equation 9] θ ₂ = θa (n) + Va (n) · Δt ₂

The times Δt ₁ and Δt ₂ and the electrical angles θ ₁ and θ
₂ corresponds as shown in FIG. Next, in step 124, the current values of the u-phase and v-phase load currents, that is, the currents Iu and Iv are read from the A / D converters 15a and 15b. Next, at step 126, the currents Iu and Iv are dq converted, and the d-axis component Iad and the q-axis component Iaq are calculated by the following equation.

[0046]

[Equation 10] Iad = 2 ^1/2 {lusin (θ ₁ + 2π / 3) -Ivsin θ ₁ }

[Equation 11] Iaq = 2 ^1/2 {Iucos (θ ₁ + 2π / 3) -Ivcos θ ₁ }

As is well known, the dq coordinate system is d
The axis is in phase with the exciting magnetic field, and the q axis is a coordinate system with a phase difference of 90 ° in electrical angle from the exciting magnetic field. The d-axis component represents an invalid component and the q-axis component represents an effective component. Next, step 1
28, the corrected target current Iq (n) ^* and the target current Id (n) ^* = 0 calculated in step 306, and step 126
Deviations of the present current from the d-axis component Iad and the q-axis component Iaq, that is, the d-axis component deviation and the q-axis component deviation are obtained. Then, based on the d-axis component deviation and the q-axis component deviation, the d-axis component Id of the command current is calculated by proportional / integral calculation.
(j) ^# and the q-axis component Iq (j) ^# are calculated.

Next, in step 130, the d-axis component and the q-axis component Id (j) ^# , Iq (j) ^# of the command current are calculated by the following equation.
Is inversely dq-converted and each phase current command value Iu (j) ^# , Iv (j) ^# ,
Iw (j) ^# is calculated.

[Equation 12] Iu (j) ^# = (2/3) ^1/2 · {Id (j) ^# cos θ ₂ −I
q (j) ^# sin θ ₂ }

[Equation 13] Iv (j) ^# = (2/3) ^1/2 · {Id (j) ^# cos (θ ₂ + 2π /
3) −Iq (j) ^# sin (θ ₂ + 2π / 3)} Note that Iw (j) ^# is calculated by Iw (j) ^# =-(Iu (j) ^# + Iv (j) ^# ). It

Next, in steps 132 and 134,
Within one control cycle, using the level relationship between the phase current command values Iu (j) ^# , Iv (j) ^# , Iw (j) ^# and the high frequency triangular wave, that is, using the average voltage method. A series of PWM signals at is generated. A series of PWM signals can be represented by a voltage vector indicating the voltage application state of each phase. The rotating magnetic field vector is expressed as the integral of this voltage vector. Therefore, the trajectory of the tip of the rotating magnetic field vector is drawn by the sum of each voltage vector × duration. In order to position the rotating magnetic field at a point on the circumference at the shortest path for each angle 2π / n, the inverter 25 is controlled by three vectors of two adjacent voltage vectors and zero vector V ₀ for each control cycle. Needs to be done. The combination of these three voltage vectors and the phase of the rotating magnetic field uniquely correspond to each other. Correspondence table of the combination of the phase of the rotating magnetic field and the voltage vector (zero vector V ₀
Is always one element of the combination, so only a set of two voltage vectors is necessary) stored in the ROM 24 in advance.

In step 132, the control electrical angle θ
_{From 2} (phase of the rotating magnetic field), the table in the ROM 24 is searched to find the combination of voltage vectors at that time.
In step 134, the duration t _1, t of each voltage vector
_2, t ₃ is calculated. For example, _assuming that the combination of the voltage vectors is V _n = (1,1,0), V ₁ = (1,0,0), V ₂ = (0,0,0), The durations t _1, t _2, t ₃ are calculated. As the calculation method, the well-known average voltage method is used in this embodiment.

That is, each phase current command value Iu (j) ^# , Iv
When two of (j) ^# and Iw (j) ^# having the largest absolute value are I ₁ ^* and I ₂ ^{* in} descending order, the durations t _1, t _{2 and} t ₃ are calculated by the following equations.

[Formula 14] t ₁ = | 2I ₂ ^* + I ₁ ^* | T / Vdc

[Equation 15] t ₂ = | I ₁ ^* -I ₂ ^* | T / Vdc

T ₃ = T− (t 1 ₊ t ₂ ) where T is the period and Vdc is the applied DC voltage.

Next, in step 136, the PWM signals of the set of voltage vectors are applied for the durations t _1, t _2, t _3.
Is only output. For example, V ₆ = (1,1,0), V ₁ = (1,0,
0) and V ₀ = (0,0,0) are output in this order for durations t _1, t _{2 and} t ₃ . In other words, the voltage is applied to the U phase for t ₁ + t _{2, the} voltage is applied to the V phase for t _{1, and the} voltage is not applied to the W phase for the control period.

Each execution cycle of the DSP 14 and the CPU 23 is executed in the minimum control cycle, which is an integer multiple n.
_The current feedback loop is controlled by ₁ , the velocity feedback loop is controlled by the integral multiple n ₂ , and the position feedback loop is controlled by the integral multiple n _3, which is a criterion for the determination in steps 100, 110 and 120. The number of times is set. However, n ₁ <n ₂ ≦ n ₃ . By repeatedly executing the above cycle, FIG.
The position, speed, and current feedback control is performed at the timing shown in. However, the timing shown in FIG. 7 is detected by the timing of the program execution by the CPU 11.

By the servo control as described above, the positioning operation by stop, acceleration, constant speed, deceleration, and stop is executed. When the feedback loop of the position, velocity and current is displayed by a transfer function, it becomes as shown in FIG. That is,
In the speed feedback loop, proportional to the speed deviation
As a result of the integration calculation, the target current Iq (n) obtained is added and corrected by the correction current value T _L (n) '/ K _tn corresponding to the disturbance torque T _L (n)' predicted and calculated by the same dimension observer. .
In the above embodiment, the target current Iq in which the high-frequency component is removed by the low-pass filter A is used as the commanded target current Iq (n) in the calculation by the same-dimensional observer.

In the above embodiment, the predicted amplification factor G ₀ of the disturbance torque is 0 and Gt with respect to the change of the current speed Va (n).
, But the gain G ₀ is changed to the current speed V
You may change continuously with respect to the change of a (n). Also,
The smaller value in the amplification factor G ₀ does not have to be 0, and the point is that G ₀ has a small value and a large value. The above embodiment is an example using the same dimension observer as shown in FIG. However, the present invention is applicable not only to the same-dimensional observer but also to the case of using the minimum-dimensional observer. In this case, the result is as shown in FIG. 9, which is the same in that the amplification factor G ₀ is changed. Further, in the present embodiment, the rotation angle is detected by the encoder and the calculation by the observer is performed. However, the predicted value of the disturbance torque may be obtained by detecting the rotation angular velocity and the calculation by the observer.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a digital servo control device according to a specific embodiment of the present invention.

FIG. 2 is a flowchart showing a target position command procedure processed by a CPU 11 of the apparatus of the embodiment.

FIG. 3 is a flowchart showing a processing procedure by a DSP used in the apparatus of the embodiment.

FIG. 4 is a flowchart showing a processing procedure by a DSP used in the apparatus of the embodiment.

FIG. 5 is a block diagram showing a transfer function in a position, velocity, and current feedback loop used in the apparatus of the embodiment.

FIG. 6 is a flowchart showing a procedure of predicting a disturbance torque by the same dimension observer.

FIG. 7 is a timing chart showing timings of position, speed, and current feedback control.

FIG. 8 is a block diagram showing a transfer function of a control system.

FIG. 9 is a view showing a position, a velocity, and the like used in another embodiment of the device.
The block diagram which showed the transfer function in the feedback loop of an electric current.

[Explanation of symbols]

10 ... Digital servo control device 11 ... CPU 12 ... ROM 13 ... RAM 14 ... DSP (digital signal processor) (target torque related value command means, angle detection means, speed detection means, disturbance torque prediction means, target torque related value Correction means,
Amplification means, amplification factor control means) 15a, 15b ... A / D converter 16 ... Current value counter (angle detection means) 17 ... Common RAM 20 ... ROM (target torque related value command means, angle detection means, speed detection means, Disturbance torque prediction means, target torque related value correction means, amplification factor control means) 25 ... Inverter 31 ... Servo motors 32a, 32b ... Current transformer (CT) 33 ... Pulse encoder Steps 110-118 ... Target torque related value command means Step 104 ... Angle detecting means Steps 112, 114 ... Speed detecting means Steps 300 to 302 ... Disturbance torque predicting means Steps 304 to 308 ... Amplification factor controlling means Step 310 ... Amplifying means, target torque related value correcting means

Claims (1)

[Claims] 1. A digital servo control device having a position feedback loop, a velocity feedback loop, and a current feedback loop, wherein a target value for each feedback loop is given as a digital amount, and is output from the velocity feedback loop according to a velocity deviation. , Target torque related value command means for sequentially commanding target torque related values to the current feedback loop, and detection means for detecting at least one of a rotation angle and a rotation angular velocity of the servo motor at each sampling time, From the detected value detected by the detection means in the control cycle, the predicted value of the disturbance torque in the current control cycle, and the commanded target torque-related value, the following operation is performed by an observer for the digital servo control system. In the control cycle Disturbance torque predicting means for predicting a disturbance torque, an amplifying means for amplifying a predicted disturbance torque in the next control cycle, and a disturbance torque amplified by the amplifying means as a target torque related value in the next control cycle. Target torque related value correction means for addition correction, and amplification rate control for changing the amplification rate according to the rotation speed of the servo motor so that the amplification rate of the amplification means tends to decrease when the rotation speed of the servo motor is high. A digital servo controller having a means.