JP2778341B2 - Servo motor speed control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control method for a servomotor, and more particularly, to a speed control method for a servomotor for driving and controlling a feed shaft of a machine tool.

[0002]

2. Description of the Related Art In a speed control method of a servo motor by digital control, a feedback speed is determined based on how many position feedback pulses obtained from an encoder or a digitally processed resolver are counted within one sampling time.

However, at a low speed, one pulse is not generated within one sampling time, and only one pulse is obtained within a few sampling times.
Become a pulse. That is, after the count continues to be "0" within one sampling time, the count suddenly becomes "1". Therefore, the speed feedback amount suddenly increases after “0” continues. For this reason, pulsating torque is generated, which is not preferable for fine servo operation. In particular, recently, machine tools that are very easy to move due to improvements in bearings have increased, and pulsating torque has become a problem.

The minimum rotation speed Nr (rpm) at which one pulse comes within one sampling time is Nr = 60 / {(number of pulses per rotation) × (one sampling time)}. Even if (the number of pulses per rotation) is increased, Nr is increased because (1 sampling time) tends to be further reduced. That is, one pulse has a large weight.

FIGS. 9 and 10 explain this state. FIG. 9 shows that the feedback speed fluctuates with a considerably large width in response to the speed command. FIG.
0 indicates the effect of the same position pulse on the speed command and the effect on the feedback speed. At this time, the theoretical specific gravity K (feedback speed / speed command) is given by K = 1 / (Kp · ITv), where the position gain is Kp (1 / sec) and one sampling time is ITv. Since the upper limit of the position gain Kp is determined by physical conditions, if the one sampling time ITv is shortened, the theoretical specific gravity K increases. Therefore, not only at low speed but also at high speed, the fluctuation rate is small, but there is a problem in the fluctuation width of the torque command.

Therefore, a method has been proposed in which the speed is determined by the ratio M / T of the number M of incoming pulses and the time T required for the number (this is called an M / T method). FIG.
FIG. 3 is a block diagram of a configuration for performing T-system control. The time counter 140 counts clock pulses. The count value is latched by the latch 141 by the position feedback pulse. Further, the value held by the latch 141 is latched by the latch 142 in response to a speed calculation signal (ITv pulse) which is an interrupt pulse. The value held in the latch 142 is time t. On the other hand, the position feedback pulse is counted by the up / down counter 143. The count value is calculated by the speed calculation signal (IT
(v pulse), and is latched by the latch 144. The value held by the latch 144 is the pulse number P. CPU
Reads the time t and the number of pulses P at different timings, and divides the number of pulses M, which is the difference between the number of pulses P, by the time T, which is the difference between the times t, to obtain the velocity v. That is, v = (difference M of pulse number P) / (difference T at time t).

FIG. 12 is an explanatory diagram of a specific example of the M / T system. The count value of the time counter 140 simply increases. The count value of the up / down counter 143 is determined by the forward rotation pulse PP ₁ , the reverse rotation pulse PP ₂ , the forward rotation pulse PP ₃ , the forward rotation pulse PP ₄ , and the forward rotation pulse PP ₅ which are position feedback pulses, P ₁ , P ₂ , P ₁ , P ₃ , P ₄ , ...
Increase or decrease. At the time of the first sampling (first ITv), the time t ₁ and the pulse number P ₁ are read. At the time of the second sampling (second ITv), the time t ₃ and the pulse number P ₁ are read. Therefore, the speed v is calculated as follows: v = (P ₁ −P ₁ ) / (t ₃ −t ₁ ) = 0. At the time of the third sampling (third ITv), the time t ₄ and the pulse number P ₃ are read. Therefore,
The speed v is calculated as follows: v = (P ₃ −P ₁ ) / (t ₄ −t ₃ ).

FIG. 13 is an explanatory diagram of another specific example of the M / T system. The count value of the time counter 140 simply increases. The count value of the up / down counter 143 is a forward rotation pulse P which is a position feedback pulse.
By P ₁ , forward rotation pulse PP ₂ , forward rotation pulse PP ₃ , P ₁ ,
P ₂ , P ₃ ,... First sampling (first
At time ITv), the time t ₁ and the pulse number P ₁ are read. At the time of the second sampling (second ITv), the time t ₁ and the pulse number P ₁ are read. Since (P ₁ −P ₁ ) = 0, the speed v becomes “0”. At the time of the third sampling (third ITv), the time t ₂ and the pulse number P ₂ are read. Therefore, the speed v is calculated as follows: v = (P ₂ −P ₁ ) / (t ₂ −t ₁ ).

Since the period of the clock pulse is sufficiently short, the time T has a high resolution (one unit is very small). Therefore, as shown in FIG. 14, the fluctuation range of the feedback value becomes very small. Further, even at a low speed in which one pulse does not come within one sampling time, an intermediate speed between "0" and "1" can be obtained.

[0010]

However, when the M / T method is used to obtain the feedback speed, the following two problems occur.

The first problem is that one sampling time (I
This is a problem that the gain of the position fluctuates when the speed becomes low at which no pulse comes to Tv). FIG. 10 shows a speed command, a feedback speed, and a torque command (speed error) at a low speed. When the servo motor is operating at a low speed of one pulse or less in one sampling time, one pulse comes for the first time at the K-th (K is an integer of 2 or more) sampling, and the actual speed can be determined. However,
At this time, the feedback speed is processed as "0" for several sampling times before, and a macro value is balanced only by returning a large value feedback speed at the time of the K-th sampling. For this reason, if the small speed (indicated by the hatched portion) calculated by the M / T method is used as the feedback speed, the feedback speed is insufficient as a whole.

When the feedback speed decreases, as shown in FIG. 15, the position gain increases equivalently, and the position error (droop) changes. Therefore,
Distortion occurs in the trajectory when interpolation is performed on two or more axes.

FIG. 16 shows errors in the case of circular interpolation. FIG. 16A shows the trajectory distortion due to the change in the position error. As the speed decreases as approaching the quadrant switching point, the gain of the position increases, and the position protrudes in the direction of infinite gain, that is, the command circle (the actual servo motor trajectory is inside the position error). Into the dead zone. After the speed reversal, the vehicle quickly enters the inside of the circle, eventually increases in speed, returns to a normal state, and returns to an arc trajectory. FIG. 16 (b) expresses an error due to lost motion at the quadrant switching point of the arc.

The second problem is that when the pulse waveform is distorted, a calculation error occurs in the speed. FIG.
Reference numeral 7 denotes an A-phase pulse, a B-phase pulse, and a position feedback pulse of the encoder. The forward / reverse rotation of the position feedback pulse is determined from the rising / falling edge of one of the A-phase pulse or the B-phase pulse and the polarity of the other. In this example, the forward rotation pulse PP is used as the position feedback pulse.
_1, the reverse rotation pulse PP _2, forward rotation pulse PP _3, forward pulse P
P ₄ and the normal rotation pulse PP ₅ are generated.

The reverse rotation pulse PP ₂ and the normal rotation pulse PP ₃ are B
This is caused by having a crack (dent) at the rising portion of the phase pulse, and is not an original position feedback pulse. These are mutually canceled if they occur within the same sampling period. However, straddles to another sampling period, yet when the forward pulse PP ₄ to the sampling period of the forward pulse PP ₃ does not turn on, will be very that one pulse has come in a short period of time,
It is erroneously determined that the speed is very high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a speed control method of a servomotor corresponding to a low speed in which one pulse does not come in one sampling time (ITv). I do. It is another object of the present invention to provide a speed control method for a servomotor which does not cause a calculation error in the speed even when the pulse waveform is distorted.

[0017]

First, the present invention relates to a method for controlling the speed of a servomotor which generates a current command based on a difference between a speed command and a feedback speed. Time T
Speed (M / T) divided by 1 sampling time (IT
When the speed (1 / a) expressed by the number of position feedback pulses per v) is "1" or less, the total is "1-1 / a".
A servo motor speed control method characterized in that a part of "1-1 / a" divided as follows is used as a feedback speed at each of a plurality of subsequent samplings.

Secondly, according to the present invention, in the above-mentioned first servomotor speed control method, "1-1 / a" is replaced by n
(= Integer) "1 / a" and one " 1-1 / a- n"
/ A ". A third aspect of the present invention is the servomotor speed control method according to the first aspect, wherein" 1-1 / a "is used.
With n (= integer) “A” (where “1 / a” <
“A” <“1-1 / a” and one “1-1 / a− n ·
A "is provided.

Fourth, the present invention relates to a speed control method of a servo motor for generating a current command based on a difference between a speed command and a feedback speed, wherein the number M of position feedback pulses is divided by a time T required for the count. Speed (M
/ T) is expressed as the number of position feedback pulses per sampling time (ITv), and the speed (1 / a) is “1”.
In the following case, there is provided a servo motor speed control method characterized in that "1-1 / a" is used as a feedback speed at the next sampling.

[0020] Fifth, the present invention, depending on the value of the speed (1 / a), first upper SL, the second, the third, the one of the speed control method of the fourth servo motor A speed control method for a servo motor is provided. Sixth
According to a third aspect of the present invention, in the third or fifth speed control method for a servomotor, the value of "A" is changed according to the value of the speed (1 / a). A speed control method is provided.

Seventh, the present invention relates to a servo motor speed control method for generating a current command based on a difference between a speed command and a feedback speed, wherein the number M of position feedback pulses is divided by a time T required for the count. Speed (M
/ T) is expressed as the number of position feedback pulses per sampling time (ITv), and the speed (1 / a) is “1”.
In the following cases, n (= integer) “B” (<1 / a) divided into a total of “1” and one “1-n · B”
Is set to a feedback speed at each of a plurality of samplings from the next time onward.

Eighth, according to the present invention, in a speed control method of a servo motor for generating a current command based on a difference between a speed command and a feedback speed, the number M of position feedback pulses is divided by a time T required for the count. Speed (M
/ T) is expressed as the number of position feedback pulses per sampling time (ITv), and the speed (1 / a) is “1”.
Provided is a servo motor speed control device characterized in that a value determined by a predetermined function is set as a feedback speed at the time of a plurality of subsequent samplings so that the time integration value becomes "1" in the following cases. .

Ninth, according to the present invention, in any one of the first, second, third, fifth, and sixth servomotor speed control devices, the "1-1 / a" A speed control method for a servomotor, characterized in that a speed command is multiplied by a coefficient based on the feedback speed when a part of the speed is used as a feedback speed at a plurality of subsequent samplings.

Tenthly, the present invention provides a method for controlling the speed of a servomotor which generates a current command based on a difference between a speed command and a feedback speed, wherein the number M of position feedback pulses is divided by a time T required for the counting. When the speed (1 / a) representing the speed (M / T) by the number of position feedback pulses per one sampling time (ITv) is within a predetermined range, the number of position feedback pulses actually existing within the sampling time is calculated by the sampling time. A speed control method for a servo motor, wherein a divided value is used as a feedback speed is provided.

Eleventh, the present invention relates to a servo motor speed control method for generating a current command based on a difference between a speed command and a feedback speed, wherein the number M of position feedback pulses is divided by a time T required for the count. When the speed (M / T) is larger than a predetermined value or a value obtained based on the speed command, a value obtained by dividing the number of position feedback pulses actually existing within the sampling time by the sampling time is used as the feedback speed. To provide a speed control method of a servo motor.

Twelfth, the present invention relates to a speed control method of a servo motor for generating a current command based on a difference between a speed command and a feedback speed, wherein the number M of position feedback pulses is divided by a time T required for the count. When the value Me obtained by converting the speed (M / T) into the number of position feedback pulses per sampling time is larger or smaller than the number of position feedback pulses actually existing within the sampling time by 2 or more, the number of position feedback pulses actually existing within the sampling time Is divided by a sampling time to provide a feedback speed, and a speed control method for a servo motor is provided.

According to a thirteenth aspect of the present invention, in any one of the first to twelfth servomotor speed control methods, the clock pulse is counted by a counter to measure the time T, and the counter is used when the counter overflows. A speed control method for a servo motor, wherein a feedback value is a value calculated by a predetermined value or an arithmetic expression.

[0028]

When the feedback speed is obtained by the M / T method, the resolution is increased, so that the current command becomes smooth, and the effect of reducing the vibration is improved. However, if the speed becomes lower than one pulse within one sampling time, the feedback speed becomes insufficient. Therefore, according to the present invention, the shortage is used as the feedback speed at the time of the next and subsequent samplings. This eliminates the shortage.

When the feedback speed is delayed in time, the control phase delay increases, and the control becomes unstable. On the other hand, the speed control characteristics of the servomotor vary depending on the load to be driven and the responsiveness also varies. Therefore, the influence on the phase delay differs even with the same delay time, and the required torque and required accuracy of the locus also differ. come. Therefore, there is a need for a variation in the method of using the shortage as the feedback speed. Thus, the present invention provides various variations of a method of using the shortage as a feedback speed at the time of the next and subsequent samplings. This makes it possible to respond to the actual situation.

The number of pulses in one sampling time is represented by “1 /
a, the shortage becomes “1-1 / a.” The first servo motor speed control method uses the shortage “1-1 / a”.
1 / a "is the feedback speed after the next sampling. The speed control method of the second servomotor is as follows.
The shortage “1-1 / a” is used as the feedback speed by “1 / a” at the time of the next sampling. The last round is “1 / a” or smaller than “1 / a”. The third above
In order to reduce the delay in control, the servo motor speed control method of this embodiment grasps in advance a value "A" that is allowable as a torque command variation value, and sets the value "A" as the feedback speed. The last round is "A" or smaller than "A". The speed control method of the fourth servo motor is an extreme case, and the shortage "1-1 / a" is used as the feedback speed at a stretch.

In the speed control method for the fifth servo motor, the above variations are selectively used depending on the speed (1 / a). In the sixth servomotor speed control method, the value "A" is changed according to the speed (1 / a). These give the optimum feedback speed.

In the seventh and eighth speed control methods of the servomotor, the phase delay of control is emphasized, and the speed (1 / a)
Independently of this, the feedback speed is determined by a predetermined value or a predetermined function. For example, m
(= Integer) If the sampling time is the maximum allowable value, m
1 / m feedback speed for sampling time
And At this time, it is also possible to change the value of m according to the speed (1 / a) to provide an appropriate feedback speed. The position feedback pulse merely gives the feedback speed and the starting point of the waveform.

In the present invention, since the shortage of the feedback speed is supplemented later, the trajectory will be deviated by the delay time, but there is practically no problem. This is because the difference in distance less than one pulse is discussed. Actually becomes a problem, the difference of such a correction (lack of feedback speed) there is a problem in a place that comes is accumulated. However, the ninth method for controlling the speed of the servomotor does not do so. That is, the ninth speed control method of the servomotor multiplies the position gain, that is, the speed command, by a coefficient corresponding to the shortage of the feedback speed, and returns to “1” with the decrease of the shortage, thereby eliminating the influence during replenishment. I have to. In this case, the speed command fluctuates because of the coefficient, but there is no problem because the speed command itself is a small value.

A tenth servomotor speed control method is as follows.
When the speed (1 / a) is within a predetermined range, a value obtained by dividing the number of position feedback pulses actually existing within the sampling time by the sampling time is defined as a feedback speed. The speed control method of the eleventh servomotor is based on the speed (1 / a)
Is larger than a predetermined value or a value obtained based on the speed command, a value obtained by dividing the number of position feedback pulses actually existing within the sampling time by the sampling time is used as the feedback speed. Thus, when the speed becomes unbelievably high due to the influence of the pulse waveform distortion, the speed (M / T) is discarded, and the value obtained by dividing the actual number of position feedback pulses within the sampling time by the sampling time. Is the feedback speed. Therefore,
The effect of the distortion of the pulse waveform can be removed.

The sampling period is generally a short period of less than 1 msec, and the speed is small and the shift is not large in the present situation. Therefore, the pulse distribution is uniform within one sampling time. That is, the pulse is not unevenly distributed within a very short time within the sampling time, and even if unevenly distributed, the pulse is included or deviated at both ends before and after the sampling at the most. Therefore, the difference between the value Me obtained by converting the speed (M / T) into the number of pulses per sampling time and the number M of pulses actually existing within the sampling time is within two. On the other hand, when the pulse waveform is distorted and the speed becomes too large to be considered, the value Me obtained by converting the speed (M / T) into the number of pulses per sampling time and the actual value within the sampling time are used. The difference in the number M of pulses to be performed does not fall within two. Twelfth
The servo motor speed control method of (1) sets the speed (M / T) to 1
Value Me converted to the number of pulses per sampling time
And the difference between the number M of pulses actually existing within the sampling time is almost equal to or less than 2, the speed (M / T)
Is discarded, and the value obtained by dividing the number of position feedback pulses actually existing within the sampling time by the sampling time is used as the feedback speed. Thereby, the influence of the distortion of the pulse waveform can be removed.

When the clock pulse is counted by the counter to measure the time T, the counter may overflow. For example, while the servomotor is stopped, the current P
Although the swing is caused by the influence of the WM control or the like, the swing is irregular, and the counter for measuring the time may overflow without the position feedback pulse coming.
In the thirteenth servo motor speed control method, when the counter overflows, a predetermined value or a value calculated by an arithmetic expression is used as the feedback speed, so that the torque command value does not greatly change even when the counter overflows.

[0037]

FIG. 1 is a block diagram of a servomotor speed control device 1 for implementing a servomotor speed control method according to the present invention. The servo motor speed control device 1 includes a position control loop, a speed control loop, and a current control loop.

The speed control loop includes a first speed calculator 2, a second speed calculator 3, and a coefficient calculator 4. The first speed calculator 2 calculates a feedback speed. When the position feedback pulse number M is equal to or less than "1" per one sampling time (ITv), the second speed calculator 3 has a function of compensating for the insufficient feedback speed. The coefficient calculator 4 calculates a coefficient to be multiplied by the speed command from the output of the second speed calculator 3.

FIG. 2 is a detailed block diagram of the first speed calculator 2. The counter 21 counts clock pulses to measure the time T. The counter 22 counts up and down the number of position feedback pulses arriving within one sampling time.

The switch SWa1 is a switch for selecting a function that does not activate the function of the comparator COM2. The switch SWa2 is a switch for selecting a function for operating the function of the comparator COM2. The switch SWb1 is connected to the comparator COM.
This is a switch for selecting whether to activate the function of No. 3.
The switch SWb2 is a switch for selecting whether to activate the function of the comparator COM4. These switches SW
a1, SWa2, SWb1, and SWb2 are set according to the actual situation so as to select the optimal feedback method variation.

When the counter 21 overflows, the comparator COM1 outputs the first operation speed V1 from the arithmetic unit 25.
Output. If the counter 21 does not overflow, the control is transferred to the comparators COM3 and COM4.

When the comparator COM2 is not stopped and the speed (1 / a) is equal to or less than "1", the arithmetic unit 24 outputs the first calculation speed V1. Otherwise,
The control is transferred to the comparator COM1. Whether the vehicle is in the stop state is determined based on a speed command, a position error, and the like. The speed (1 / a) is
It is calculated by an M / T type arithmetic unit (not shown). The problem of vibration and noise is subjective and subtle, and often causes a problem even though it has nothing to do with performance. For example, while the machine tool is not moving, the vibration may be a concern.However, during the cutting operation where the interpolation trajectory is a problem, there is a considerable cutting reaction force and the load is heavy. Often this is not a problem. In such a case, the function of the comparator COM2 is useful.

When the speed (1 / a) is smaller than the predetermined value Vp, the comparator COM3 causes the calculator 23 to output the first calculation speed V1. Otherwise, the operator 24
Then, the first calculation speed V1 is output. Speed (1 / a)
Is calculated by a not-shown M / T type calculation unit. When the difference between the value Me obtained by converting the speed (1 / a) into the number of pulses in one sampling time and the number M of pulses actually existing in one sampling time is 2 or more, the comparator COM4 operates the arithmetic unit 24. Then, the first calculation speed V1 is output. If not, the arithmetic unit 23 outputs the first arithmetic speed V1. The speed (1 / a) is calculated by an unillustrated M / T type calculation unit.

The arithmetic unit 23 calculates the speed (M / M) by dividing the number M of position feedback pulses by the time T required for the count.
T) is output at the speed (1 / a) represented by the number of position feedback pulses per sampling time (ITv). The calculator 24 outputs the first calculation speed V1 at a speed obtained by dividing the number of position feedback pulses actually existing within the sampling time by the sampling time. The calculator 25 outputs the first calculation speed V1 at a constant value 1 / c (where c> 1).

When the first operation speed V1 is higher than "1", the comparator COM5 uses the first operation speed V1 as a feedback speed. If the first calculation speed V1 is "1" or less, the control is transferred to the second speed calculator 3. The unit of the speed is
(1 / ITv) is set to “1”.

In principle, a value of 1 (1 / ITv) or less 1
In the case of / a, all shortfalls (1-1 / a) are returned,
When the command is stopped, there is no need to return it because it has nothing to do with the path.
However, since there is no problem in returning, a switch SWc indicated by a broken line may be provided.

As a result, the first calculation speed V1 output from the first speed calculator 2 is the speed according to the M / T method or the M / IT
Either the speed according to the v method or the constant speed 1 / c.

FIG. 3 is a detailed block diagram of the second speed calculator 3. The second speed calculator 3 performs a process of supplementing a shortage of the feedback speed when the speed is lower than “1”;
And processing when a plurality of such replenishments overlap. The distributor 31 indicates an empty main arithmetic unit 32 when replenishment for the shortage of the feedback speed is overlapped. Main operation unit 3
Since there are four 2s, it is possible to cope with the case where four replenishments overlap. Note that the number of main arithmetic units 32 may be less than four or five or more. Details of the main arithmetic unit 32 will be described later with reference to FIG. The synthesizer 33 adds the outputs of the main arithmetic unit 32,
The second calculation speed V2 is output. It also outputs the number of overlapping replenishments j.

FIG. 4 is a detailed block diagram of the main arithmetic unit 32. The switches SWd1 and SWd are included in the switches SWd.
There are four switches d2, SWd3, and SWd4. These switches SWd1, SWd2, SWd3, and SWd4 are:
Only one is on or all are off. When SWd1 is turned on, “1/1 /” is set at the next first (i = 1) sampling.
a ″ is the second calculation speed V2, and at the time of the second (i ≠ 1) or later sampling, the remaining R (= 1−1 / a−i /
If a) is larger than “1 / a” (R> 1 / a), “1”
/ A "is set as the second calculation speed V2, and if it is smaller, the remaining amount R is set as the second calculation speed V2.

When SWd2 is turned on, the first time (i =
At the time of sampling 1), “A” is set to the second operation speed V2, and at the time of the second (i ≠ 1) or later sampling, the remaining R (= 1−1 / a−i · A) is shorter than “A”. If it is larger (R> A), “A” is set as the second calculation speed V2, and if it is smaller, the remaining R is set as the second calculation speed V2. The value of “A” may be changed according to the value of the speed (1 / a). When SWd3 is turned on, "1-1 / a" is set to the second calculation speed V2 at the next sampling.

When SWd4 is turned on, the first time (i =
In the sampling of 1), “B” is set to the second operation speed V2, and the remaining R (= 1−i · B) is larger than “B” in the second (i ≠ 1) and subsequent samplings (R >
In B), "B" is set to the second calculation speed V2, and if it is smaller, the remaining shortage R is set to the second calculation speed V2. The value of “B” may be changed according to the value of the speed (1 / a). As shown in FIG. 5, it has been found that good results can be obtained by using an encoder pulse as a feedback speed through a filter in the case of analog servo. Following this, the feedback speed for one pulse is fed back over several sampling times, and the waveform is such that the total becomes "1".

The switch SWe includes switches SWd1, SW
It is turned on when d2, SWd3, and SWd4 are all off. When the switch SWe is turned on, a value based on a predetermined function f (i) is set as a second calculation speed V2 every time sampling is performed. FIG. 6 illustrates the function f (i).

FIG. 7 shows the position feedback pulse P ₀ ,
This shows a case where the replenishment for the shortage of the feedback speed corresponding to P ₁ and P ₂ overlaps. When the replenishments overlap in this way, the sum of the replenishments becomes the second calculation speed V2, which becomes the feedback speed.

The coefficient calculator 4 applies a coefficient to the speed command so as not to change the position gain (to make the ratio between the speed command and the feedback speed the same) even while the shortage of the feedback speed is being supplemented. Is output. This coefficient becomes “1” when all the shortfalls in the feedback speed are replenished. If the replenishment does not overlap, the coefficient becomes exactly the same value as the integrated value of the already returned feedback speed (second calculation speed V2). . If replenishment overlaps, equalize. That is, in the period in which replenishment overlaps, a value obtained by dividing all integrated values of the related second calculation speed V2 by the number j of overlaps is used. To describe in Figure 7, the [k-3, k-2] period, the integrated value of the second operational speed V2 by P _o (this case is "1") and by P ₁ of the second operational speed V2 It is obtained by dividing the sum of the integrated value (in this case, V2 itself) by “2”.

FIG. 8 shows FIG. 10 (conventional) of the present invention.
FIG.

[0056]

According to the servo motor speed control method of the present invention, when the speed of the servo motor is reduced and one pulse does not come in one sampling time, and the feedback speed becomes insufficient, the variation prepared in advance is used. A pattern in which a smooth torque is output within the allowable range of the phase delay is selected, and the shortage of the feedback speed is compensated. Therefore, an accurate trajectory can be obtained even in a smooth operation and an interpolation operation of two or more axes. Also, depending on the load, it may be better to use the M / T method only in a state that is not related to the fluctuation of the position gain, such as to suppress vibration and noise during stoppage. Since the / ITv method is used properly, this can be handled. Further, in the M / T system, there is a possibility that the speed value obtained by the calculation may include a large error when the pulse waveform has a concave portion, but this is detected and switched to the M / ITv system. Therefore, no malfunction occurs.

[Brief description of the drawings]

FIG. 1 is a block diagram of a servomotor speed control device.

FIG. 2 is a detailed block diagram of a first speed calculator.

FIG. 3 is a detailed block diagram of a second speed calculator.

FIG. 4 is a detailed block diagram of a main processing unit.

FIG. 5 is an explanatory diagram of waveform processing of an analog servo encoder.

FIG. 6 is an exemplary diagram of a function.

FIG. 7 is an explanatory diagram in the case where replenishments for the shortage of the feedback speed overlap.

FIG. 8 is an explanatory diagram of a speed command, a feedback speed, and a torque command according to the present invention.

FIG. 9 is a conceptual diagram of a conventional servo motor speed control.

FIG. 10 is an explanatory diagram of an M / T method.

FIG. 11 is a block diagram of an apparatus that implements the M / T method.

FIG. 12 is an explanatory diagram of a specific example of the M / T method.

FIG. 13 is an explanatory diagram of a specific example of the M / T method.

FIG. 14 is an explanatory diagram of a relationship between speed feedback and a speed command in the M / T method.

FIG. 15 is an explanatory diagram of a relationship between a feedback speed and a position gain.

FIG. 16 is a view showing an example of a trajectory when a position gain in circular interpolation changes.

FIG. 17 is an example of a pulse waveform crack of an encoder.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Servo motor control device 2 First speed calculator 3 Second speed calculator 4 Coefficient calculator 21, 22 Counter COM1 to COM5 Comparator SWa1, SWa2, SWb1, SWb2 Switch 31 Distributor 32 Main calculator 33 Synthesizer SWd1 , SWd2, SWd3, SWd4, SWe switch

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshio Shinohara 5-1-1, Yadaminami, Higashi-ku, Nagoya-shi Nagoya Works, Mitsubishi Electric Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) G05D 3/00-3/20

Claims (13)

(57) [Claims] In a speed control method of a servomotor for generating a current command based on a difference between a speed command and a feedback speed, a speed (M / T) obtained by dividing the number M of position feedback pulses by a time T required for the count. When the speed (1 / a) expressed by the number of position feedback pulses per sampling time (ITv) is equal to or less than "1", "1-1 / a" is divided so as to be "1-1 / a" in total. a speed control method for a servo motor, wherein a part of a '' is set as a feedback speed at each of a plurality of samplings from the next time. 2. A speed control method for a servo motor according to claim 1, the "1-1 / a", and n (= integer) "1 / a", 1 single "1 -1 / a -n / a ". 3. The servo motor speed control method according to claim 1, wherein “1-1 / a” is replaced by n (= integer) “A” (where “1 / a” <“A”). <“1-1 / a”
A speed control method of a servo motor, wherein the speed is divided into one " 1-1 / a- nA". 4. In a speed control method for a servomotor that generates a current command based on a difference between a speed command and a feedback speed, a speed (M / T) obtained by dividing the number M of position feedback pulses by a time T required for the count. When the speed (1 / a) expressed by the number of position feedback pulses per sampling time (ITv) is equal to or less than “1”, “1-
A speed control method for a servo motor, wherein 1 / a "is used as a feedback speed at the next sampling. 5. Depending on the value of the speed (1 / a),請 Motomeko 1, claim 2, claim 3, the selection of one of the speed control method for a servo motor according to claim 4 Characteristic servo motor speed control method. 6. The servo motor speed control method according to claim 3, wherein the value of “A” is changed in accordance with the value of the speed (1 / a). Speed control method. 7. A servo motor speed control method for generating a current command based on a difference between a speed command and a feedback speed, wherein a speed (M / T) obtained by dividing the number M of position feedback pulses by a time T required for the count. When the speed (1 / a) expressed by the number of position feedback pulses per sampling time (ITv) is equal to or less than “1”, n (= integer) “B” divided so as to be “1” in total. ”(<
1 / a) and one “1-n · B” as a feedback speed at the time of a plurality of subsequent samplings, respectively. 8. In a speed control method of a servo motor for generating a current command based on a difference between a speed command and a feedback speed, a speed (M / T) obtained by dividing the number M of position feedback pulses by a time T required for the count. When the velocity (1 / a) expressed by the number of position feedback pulses per one sampling time (ITv) is equal to or less than “1”, the value determined by a predetermined function so that the time integration value becomes “1” is calculated next time. A speed control device for a servo motor, wherein a feedback speed is set for each of a plurality of subsequent samplings. 9. The servo motor speed control device according to claim 1, wherein a part of “1-1 / a” is set to the next time. A speed control method for a servo motor, comprising: multiplying a speed command by a coefficient based on the feedback speed when the feedback speed is set at each of a plurality of subsequent samplings. 10. A servo motor speed control method for generating a current command based on a difference between a speed command and a feedback speed, wherein a speed (M / T) obtained by dividing the number M of position feedback pulses by a time T required for the count. When the speed (1 / a) expressed by the number of position feedback pulses per sampling time (ITv) is within a predetermined range,
A speed control method for a servo motor, wherein a value obtained by dividing the number of position feedback pulses actually existing within a sampling time by a sampling time is used as a feedback speed. 11. In a speed control method for a servomotor that generates a current command based on a difference between a speed command and a feedback speed, a speed (M / T) obtained by dividing the number M of position feedback pulses by a time T required for the count. Is greater than a predetermined value or a value obtained based on the speed command,
A speed control method for a servo motor, wherein a value obtained by dividing the number of position feedback pulses actually existing within a sampling time by a sampling time is used as a feedback speed. 12. A speed (M / T) obtained by dividing the number M of position feedback pulses by the time T required for counting in a speed control method of a servo motor that generates a current command based on a difference between the speed command and a feedback speed. Is converted to the number of position feedback pulses per sampling time, and when Me is larger or smaller than the number of position feedback pulses actually existing within the sampling time by 2 or more, a value obtained by dividing the number of position feedback pulses actually existing within the sampling time by the sampling time. A speed as a feedback speed. 13. The servo motor speed control method according to claim 1, wherein the clock pulse is counted by a counter to measure the time T, and when the counter overflows, the predetermined time is determined. A speed control method for a servo motor, wherein a value calculated by a value or an arithmetic expression is used as a feedback speed.