JPH04361644A - Control of drive motor of rotary drum type length measuring device of weaving machine and device therefor - Google Patents

Abstract

PURPOSE:To make short pick not occur even in the case of response lag of driving motor for working a drum of length measuring device. CONSTITUTION:A following control device 10 is provided with a resetting means 20. The following control device 10 follows a main shaft A of weaving machine at a given ratio (a) and regulates revolution of a driving motor M. Since the resetting means 20 generates a clear signal Sc to the following control device 10 at least in a given weft inserting cycle and clears regulation deviation of the following control device 10, the driving motor M follows the main shaft A in a normal ratio (a) and will not cause short pick in the next weft inserting.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to the response of the drive motor when weft insertion is performed via a rotating drum-shaped weft length measuring and storage device (hereinafter simply referred to as length measuring device) driven by a dedicated drive motor. The present invention relates to a drive motor control method for a rotating drum length measuring device for a loom, which can effectively prevent short picks due to delays, and the device.

0002

2. Description of the Related Art A rotating drum type length measuring device includes a drive motor M consisting of a variable speed motor, a drum D driven by the drive motor M, a restraint pin P, and a yarn W from a yarn feeder Wa to the drum D. (FIG. 6).

A pulse generator PG for detecting the amount of rotation of the drum D is connected to the drive motor M. restraining pin P
is mounted on a bracket Pa on the front end side of the drum D, and when it moves forward toward the annular groove Da formed on the drum D and inserts its tip into the groove Da, the yarn W on the drum D and When the thread W is engaged and then retreated to remove the tip from the groove Da, the engagement with the thread W can be released.

[0004] When the yarn W is unwound from the yarn supply body Wa,
It is supplied to the rear side of the drum D via the delivery rollers R, R and the yarn guide G1, and is wound onto the drum D and stored. The yarn W on the drum D is unwound from the front side of the drum D, passes through the yarn guide G2, the clamp device CL, and the weft insertion nozzle NZ, and is inserted into a warp opening (not shown).

[0005] The delivery rollers R, R move the yarn W from the yarn supply body Wa at the same yarn speed as the circumferential speed of the drum D, for example, by sliding one of them against the rear end of the drum D. This forms an active yarn feeding mechanism that actively supplies the yarn to the drum D. The restraint pin P, the clamp device CL, and the weft insertion nozzle NZ operate at a predetermined time of the loom cycle to perform a weft insertion operation for the yarn W. In other words, the restraining pin P is connected to the drum D.
Drum D
The yarn W stored above can be inserted in a free flying state, and by inserting the restraining pin P into the groove Da in this state, so-called restrained flying can be realized.

When a plurality of such length measuring devices are installed in parallel to realize multicolor weft insertion, focusing on one length measuring device, the storage amount Q of yarn W stored on the drum D is For a plurality of loom cycles N or time t constituting one repeat of the weaving pattern, the result is as shown in FIG. 7, for example. however,
Here, it is assumed that one repeat consists of five loom cycles, in which weft insertion is not performed in the first, second, and fourth cycles, and weft insertion is performed in the third and fifth cycles.

The storage amount Q is Q=0 (turns) at the start point of the first cycle, but the drum D is rotated following the main shaft (not shown) at a ratio a=3 (turns/cycle). Therefore, by the end of the second cycle, Q=6(
turn). Then drum D has a ratio a=2
(turn/cycle), and in the middle of the third cycle, the weft insertion nozzle NZ is operated, the restraining pin P is moved backward, and the clamping device CL is opened (Fig. 7
point X1), the yarn W is inserted in a free flying state (
Free flight section T1) in the same figure. Subsequently, when only the restraint pin P is advanced (point X2 in the figure), the thread W enters a restrained flight state (restricted flight section T2 in the figure). In the restricted flying state, the yarn W supplied by the sending rollers R and R is directly supplied to the weft insertion nozzle NZ via the drum D, so the amount Q stored on the drum D cannot be kept constant. can.

When the weft insertion is completed at the end of the third cycle, the length q of the yarn W inserted here (hereinafter referred to as the length per pick) will be the same as if the weft insertion had not been performed in the third cycle. From the virtual storage amount Qa and the actual storage amount Qb after weft insertion, q = Qa - Qb = 6
(turn). Thereafter, weft insertion is not performed in the fourth cycle, and in the fifth cycle, yarn W of length q = 6 (turns) per pick is similarly carried out.
Insert the weft and complete one repeat. In addition, the 4th and 5th
The storage amount curve in the cycle is determined by translating the virtual storage amount curve (dotted chain line in the same figure) based on the actual storage amount Qb at the end point of the third cycle and assuming that weft insertion is not performed in the third cycle. Can be done. At the end of the fifth cycle, the actual storage amount Qb = 0 (turn)
The state returns to the starting point of the first cycle.

Here, the amount of rotation of the drum D is controlled by a tracking control device (not shown) so that the drive motor M follows the main shaft at a predetermined ratio a, and the ratio a is set to At the end of each loom cycle, a weft selection device (not shown) specifies that the virtual storage amount Qa is equal to or greater than a predetermined length q per pick. Also, the actual storage amount Qb at the end point of one repeat
Instead of setting Qb = 0, it is also possible to set Qb ≠ 0 by moving the storage amount curve shown by the solid line in FIG. 7 upward in parallel.

0010

[Problems to be Solved by the Invention] According to this prior art, when changing the ratio a of the drive motor M to the main shaft, if there is a delay in the response of the drive motor M, long picks or short picks occur. There is a problem that stable weft insertion operation cannot be performed.

For example, in FIG. 7, when the ratio a is changed from a=3 (turns/cycle) to a=2 (turns/cycle) at the starting point of the third cycle, the drive motor M Immediately the ratio a=2(turn/
cycle), and the virtual storage amount curve at that time curves upward (double-dashed line in the figure).

On the other hand, since the rotation amount of the drive motor M is controlled by the follow-up control device, the deviation ΔQ at this time
After reaching its maximum value (point Y1 in the figure), it gradually decreases and eventually disappears (point Y2 in the figure). However, as shown in the figure, if the deviation ΔQ is not resolved by the end of the weft insertion cycle (hereinafter referred to as the weft insertion cycle) and remains in the storage section for the next weft insertion, the third The weft insertion length in the cycle is a long pick by Δq=Qa1-Qa with respect to the predetermined length q per pick, and the weft insertion length in the fifth cycle is as follows:
The short pick will be Δq=Qa−Qa2. However, Qa1 and Qa2 indicate the virtual storage amount at the end of the third cycle and the fifth cycle, respectively, when the drive motor M has a response delay, and the virtual storage amount Qa2 at the end of the fifth cycle is as follows: Using the actual storage amount Qb at the end point of the third cycle as a base point, it can be determined by translating the virtual storage amount curve when the drive motor M has a response delay.

[0013] This situation occurs not only when changing the ratio a within one repeat, but also when the loom starts up, when the loom's load fluctuates due to changes in the shedding movement pattern, and when the power supply voltage fluctuates, etc. The same problem occurs when there is a change in the number. That is, when controlling the rotation of the drive motor M by following the main shaft at a predetermined ratio a, if there is a change in the ratio a or a fluctuation in the rotational speed of the loom, a deviation ΔQ will occur due to the response delay of the drive motor M, and , if the deviation ΔQ is not resolved by the end of the weft insertion cycle,
Not only is there an excess or deficiency in the weft insertion length at that time, but also an excess or deficiency in the weft insertion length opposite to the previous weft insertion length will occur in the next weft insertion.

[0014] In general, long picks do not have a fatal drawback to woven fabrics, but short picks
This is a fatal defect because it causes missing parts of the weft threads within the woven fabric.

SUMMARY OF THE INVENTION Therefore, in view of the problems of the prior art, an object of the present invention is to clear the control deviation of the follow-up control device at least in a predetermined weft insertion cycle, so that even if there is a response delay in the drive motor, at least An object of the present invention is to provide a drive motor control method for a rotating drum type length measuring device for a loom, which can effectively prevent the occurrence of short picks, and the device.

[0016]

[Means for Solving the Problems] The configuration of the first invention according to this application for achieving the above object is to rotate a drive motor for driving a drum following a main shaft at a predetermined ratio via a follow-up control device. The gist of the control is to clear the control deviation of the follow-up control device at least in a predetermined weft insertion cycle.

The configuration of the second invention is such that the following control device inputs the rotation amount of the main shaft and the rotation amount of the drive motor and controls the rotation of the drive motor by following the main shaft at a predetermined ratio. The gist thereof is to provide a reset means for clearing the control deviation of the follow-up control device in the input cycle.

The reset means may input a crank angle and clear the control deviation of the follow-up control device at a predetermined set crank angle, or may input a weft selection signal from a weft selection device. , the loom cycle in which the control deviation of the follow-up control device should be cleared may be determined.

[0019]

[Operation] According to the configuration of the first invention, the control deviation of the follow-up control device occurs due to the response delay of the drive motor, and therefore, it is necessary to forcibly clear it at least in a predetermined weft insertion cycle. Since the drive motor is then controlled to rotate without any control deviation, it can be made to follow the main shaft at a predetermined ratio. In other words, after the control deviation is cleared, the storage amount curve for the next weft insertion has a normal slope because the drive motor follows the main axis at a regular ratio, and therefore, at the next weft insertion, There is no risk of short picks occurring.

[0020] When clearing the control deviation in this manner, the cause of the occurrence of the control deviation does not matter. In other words, the cause of this is not only when the ratio of the drive motor to the main shaft is changed, but also when the rotational speed of the loom changes due to the start of the loom, changes in the load on the loom due to changes in the shedding movement pattern, changes in the power supply voltage, etc. etc., or a combination thereof. Furthermore, here, the predetermined weft insertion cycle refers to the first weft insertion cycle after the cause of the control deviation has occurred.

Generally, the point at which the control deviation is cleared is after the absolute value of the control deviation changes from an increasing trend to a decreasing trend, until the amount of yarn stored on the drum starts to increase for the next weft insertion. Any time is fine. Therefore, it is easiest to set the point at which the control deviation is cleared at the end of the loom cycle. This is because the point in time can be uniquely determined by monitoring the crank angle.

According to the configuration of the second invention, since the reset means clears the control deviation of the follow-up control device at least in a predetermined weft insertion cycle, the first invention can be implemented as is as a whole.

[0023] If the crank angle is input to the reset means,
By monitoring the crank angle, the reset means can uniquely determine the point in time at which the control deviation should be cleared, and if the weft selection signal is input, the reset means can select one of the plurality of loom cycles constituting one repeat by inputting the weft selection signal. It is possible to determine the loom cycle in which weft insertion is currently being performed and in which the control deviation should be cleared, and to clear the control deviation, for example, at the end of that loom cycle.

[0024]

[Embodiment] An embodiment will be explained below with reference to the drawings.

A drive motor control device (hereinafter simply referred to as a control device) 1 for a rotary drum type length measuring device of a loom includes a follow-up control device 10 and a reset means 20 (FIG. 1). However, here, two length measuring devices having the configuration shown in FIG. 6 are installed in parallel, and the drive motor M of each length measuring device is
While the rotation is controlled by following the main axis A of the loom through individual control devices 1, each control device 1 and the unillustrated restraint pins P and clamp devices CL of each length measuring device are connected to a common weft selection device 2. shall be controlled by.

An encoder EN for detecting the crank angle θ is connected to the main shaft A of the loom, and the output of the encoder EN is sent as a pulse train signal Sa to the follow-up control device 10 of each control device 1, the reset means 20, and others. , are also input to the weft selection device 2. In addition, from the weft selection device 2,
A weft selection signal S1 and a ratio signal S2 are output to each control device 1, the former being input to the reset means 20, and the latter being input to the follow-up control device 10 via the ratio setting device 31. Further, the output of the reset means 20 is inputted to the follow-up control device 10 as a clear signal Sc. The weft selection device 2 outputs further outputs as drive signals S3 and S3, and the weft selection device 2
It is assumed that each drive signal S3 individually drives the restraint pin P and clamp device CL belonging to each length measuring device.

The output of the follow-up control device 10 is transmitted to the control amplifier 3
2, it is connected to a drive motor M that drives the drum D. Note that the output of the pulse generator PG connected to the drive motor M is the rotation amount Pf of the drive motor M and the drum D.
As a pulse train signal Sf representing
It is fed back to 0.

The follow-up control device 10 includes a frequency divider 11 and a deviation counter 12 (FIG. 2). The frequency divider 11 receives the crank angle θ from the encoder EN and the ratio setter 3.
1 is input, and the output of the frequency divider 11 is connected to the addition terminal U of the deviation counter 12.

The rotation amount Pf of the drive motor M from the pulse detector PG is input to the subtraction terminal D of the deviation counter 12, and the output of the deviation counter 12 is externally transmitted via the DA converter 13 and the summing point 14. control amplifier 3
It is guided by 2. Note that the rotation amount Pf of the drive motor M
are also input to the summing point 14 via the FV converter 15.

The reset means 20 inputs the crank angle θ, inputs the comparator 21 provided with the setter 22, and the weft selection signal S1 from the weft selection device 2, and receives the weft selection signal S1.
1, a comparator 43 that connects the counter 41 and the setting device 42, and the comparator 21.
, 43 (FIG. 3). The output of the AND gate 23 is the clear signal S
c is guided to the follow-up control device 10 (FIG. 2) and input to the reset terminal R of the deviation counter 12.

Now, when the loom is in steady operation, the encoder EN outputs a pulse train signal Sa indicating the crank angle θ.
is output and input to the frequency divider 11 of the follow-up control device 10. Here, if the frequency divider 11 divides the frequency of the pulse train signal Sa by the frequency division ratio k given from the ratio setter 31, the frequency divider 11 divides the frequency of the pulse train signal Sa by the frequency division ratio k given from the ratio setter 31.
The target rotation amount signal Sa1 consisting of /k pulses can be sent to the addition terminal U of the deviation counter 12. However, Na is the number of pulses of the pulse train signal Sa output by the encoder EN per one revolution of the main shaft A, and therefore, the frequency divider 11 substantially has the rotation amount Pa of the main shaft A.
is entered.

On the other hand, since the pulse train signal Sf from the pulse generator PG is input to the subtraction terminal D of the deviation counter 12, if the amount of rotation of the main shaft A is Pa and the amount of rotation of the drive motor M is Pf, then The deviation counter 12 calculates the difference ΔP between the number of pulses between the target rotation amount signal Sa1 and the pulse train signal Sf, ΔP=PaNa/k−PfNf, and
Via a converter 13, it can be outputted as a control deviation ΔP1 to a summing point 14. However, Nf is the number of pulses of the pulse train signal Sf output by the pulse detector PG per one rotation of the drive motor M. Therefore, the control amplifier 32 controls the rotation of the drive motor M in the direction in which the control deviation ΔP1 is eliminated, and therefore, the follow-up control device 10
Overall, the rotation of the drive motor M can be controlled so as to follow the main axis A. In addition, the FV converter 15
feeds back the rotation speed of the drive motor M to the summing point 14, forming a speed minor loop of the drive motor M.

Note that per rotation of the main shaft A, that is, 1
By rotating the drive motor M a number of revolutions per loom cycle, the drive motor M can store the yarn W on the drum D at a ratio a (turns/cycle). Therefore, in order to realize this, aNf = Na
The frequency division ratio k from the ratio setter 31 may be determined so that /k k=(Na /Nf )/a.

Now, it is assumed that one of the two length measuring devices is operated in accordance with FIG. 7 so as to realize the storage amount curve shown in FIG. 4. That is, this length measuring device realizes one repeat consisting of five loom cycles, and in the third and fifth cycles, there is a free flight section T1 and a restrained flight section T2.
At the same time, the ratio a of the drive motor M to the main shaft A is a=3 (turns/cycle) in the first and second cycles, and a=2 in the third, fourth, and fifth cycles. (turn/cycle). Note that at this time, the other length measuring device performs weft insertion in the first, second, and fourth cycles, and the ratio a is the same as that in the first, second, and fourth cycles.
a = 4.5 (turns/cycle) in 5 cycles
By operating with a=3 (turns/cycle) in the second, third, and fourth cycles, two-color weft insertion can be performed as a whole.

Therefore, the weft selection device 2 selects the crank angle θ
By inputting , it is determined which loom cycle of one repeat the current loom cycle corresponds to, and based on the result, a predetermined ratio a is set to the ratio signal S2 for each control device 1. At the same time, a drive signal S3 is sent at a predetermined time to the restraint pin P and clamp device CL of the length measuring device that is to perform weft insertion in the loom cycle. The ratio setter 31 sends the frequency division ratio k=(Na/Nf)/a to the frequency divider 11 of the follow-up control device 10 based on the ratio a from the weft selection device 2, so that the drive motor M , the rotation can be controlled to follow the main axis A at a predetermined ratio a for each loom cycle. Therefore, each length measuring device can execute a weft insertion operation at a predetermined time and realize a predetermined weft insertion pattern.

In FIG. 4, in the third, fourth, and fifth cycles, not only does the ratio a change from a=2 (turns/cycle) to a=3 (turns/cycle), but also, for example, the opening movement The width of each loom cycle in the horizontal axis direction is illustrated to be longer, assuming that the rotational speed of the loom decreases because the load on the loom increases due to the change in pattern. However, the drive motor M, via the follow-up control device 10,
Continuously follows the main axis A, restraining pin P, clamping device C
Since the drive of L is controlled via the weft selection device 2 based on the crank angle θ, even if the rotational speed of the loom changes, these weft inserting members operate while maintaining a predetermined synchronous relationship. is possible.

The responsiveness of the drive motor M is changed by changing the ratio a,
If the rotation speed of the loom is insufficient for fluctuations in rotation speed, the storage amount curve curves upward (double-dashed line in Fig. 4), and the storage amount Q has a deviation Δ.
Q occurs, and in response to this, the reset means 20 is activated.

The reset means 20 uses a counter 41 to count the number n of times the weft selection signal S1 is outputted from the weft selection device 2 during one repeat, and the comparator 43 calculates n=
When no is detected, the comparator 21 detects that the crank angle θ has become θ=θo and outputs a clear signal S.
c can be output. However, no, θo
are the set weft insertion cycle and the set crank angle set in the setters 42 and 22, respectively. Therefore, no = 1
Then, the output of the comparator 43 can be continuously output from the start point to the end point of the first weft insertion cycle in one repeat, that is, the third cycle in FIG. 4, and at this time, θo =360 (degrees), the reset means 20 can generate the clear signal Sc at the end of the third cycle in FIG.

It is assumed that the weft selection signal S1 is continuously output from the start point to the end point of the weft insertion cycle Ni, and the counter 41 is cleared at the end point of the final loom cycle of one repeat.

The clear signal Sc clears the contents of the deviation counter 12 of the follow-up control device 10, and the control deviation ΔP1
(Figure 2). Therefore, after that, the control deviation ΔP1 is cleared, so that the drive motor M operates as follows.
Since it is possible to follow the main axis A so as to realize the normal slope of the storage amount curve (double-dotted line from the 4th cycle onward in Figure 4), a short pick occurs during weft insertion in the next 5th cycle. There is no risk of it happening. This is because the storage amount curve from the fourth cycle onwards can be made to match the regular storage amount curve whose base point is the actual storage amount Qb at the end point of the third cycle. However, in Figure 4, Q
a, Qa1, and Qb respectively indicate the normal virtual storage amount at the end point of the weft insertion cycle, the virtual storage amount when there is a response delay in the drive motor M, and the actual storage amount after weft insertion, as in FIG. Let q indicate the regular weft insertion length per pick. At this time, the weft insertion length in the third cycle in FIG. 4 is a long pick by Δq=Qa1-Qa, but this does not constitute a fatal fabric defect.

In the above explanation, the reset means 20 may output the clear signal Sc in every weft insertion cycle. That is, in the reset means 20, by omitting the counter 41, setter 42, and comparator 43 and directly inputting the weft selection signal S1 to the AND gate 23, the clear signal Sc is set at the end point of the fifth cycle in FIG. is also output from the reset means 20. However, in this case, there is no response delay of the drive motor M, and therefore, there is no content remaining in the deviation counter 12 to be cleared, so the clear signal Sc at this time is
It doesn't do anything special.

Generally, the clear signal Sc is determined by the absolute value |ΔQ| of the deviation ΔQ of the storage amount Q and the control deviation ΔP1 of the follow-up control device 10 in the loom cycle in which weft insertion is to be performed.
The point at which |ΔP1| changes from an increasing trend to a decreasing trend (Figure 4
It is sufficient to generate it within the interval T from point Y1) onward to the end point of the loom cycle. When the control deviation ΔP1 is cleared by the clear signal Sc, the drive motor M can then realize the normal slope of the storage amount curve, thus effectively preventing the occurrence of short picks for the next weft insertion. This is because it is possible. Therefore, the set crank angle θo in FIG. 3 is determined by the clear signal Sc
As long as is within the interval T, θo≦360 (degrees) may be used. Further, the set crank angle θo may be made to match the crank angle at which the clamp device CL is in the closed state.

[0043]

[Another Embodiment] The reset means 20 omits the counter 41, the setting device 42, and the comparator 43, and uses a weft selection signal S1 and a speed control signal Sn from a control circuit of the loom (not shown).
It is possible to add an OR gate 24 that inputs (
Figure 5).

The speed control signal Sn is generated, for example, by differentiating the output of a speed sensor that measures the rotational speed of the loom to detect the acceleration of the loom, and when the absolute value of this acceleration is larger than a predetermined set value. If so, the clear signal Sc
The rotation speed of the loom suddenly fluctuates for some reason, and the deviation ΔQ and control deviation ΔP1 are caused by the response delay of the drive motor M.
This can be caused whenever there is a risk that the amount of weft may become excessive, and short picks can be prevented during subsequent weft insertion. Note that such a speed control signal Sn
can be generated in response to an increase or decrease in the rotational speed of the loom, so it is effective against fluctuations in the rotational speed during steady operation due to any cause, as well as response delays in the drive motor M when starting the loom. It is possible to deal with it.

Alternatively, the speed control signal Sn may be a shedding movement pattern command signal or a loom start signal.

Generally, as mentioned above, the clear signal Sc has no response delay in the drive motor M, and the control deviation ΔP1
Even if it occurs when it does not exist, there is no particular harm. Therefore, even if multi-color weft insertion is performed using a plurality of length measuring devices, the reset means 20 uses a weft selection signal S.
1, the clear signal Sc may be generated in all loom cycles without determining the loom cycle in which the control deviation ΔP1 should be cleared. Further, when the loom cycle in which the control deviation ΔP1 occurs is not a weft insertion cycle, it is sufficient to output the clear signal Sc in the first weft insertion cycle thereafter. That is, it is sufficient that the clear signal Sc is generated at least in a predetermined weft insertion cycle. It should be noted that when performing one-color weft insertion using only one length measuring device and without using the weft selection device 2, it is possible to uniformly generate the clear signal Sc in all loom cycles. Not even.

Further, the present invention provides a length measuring device that does not use the delivery rollers R, R, but always has a plurality of turns of yarn W at the rear of the drum D, and realizes restrained flight through the yarn W. It can also be applied as is.

[0048]

As explained above, according to the first invention of this application, at least in a predetermined weft insertion cycle, by clearing the control deviation of the follow-up control device that controls the rotation of the drive motor, , the drive motor can follow the main shaft without any control deviation and can achieve the regular storage amount on the drum, so when inserting the next weft, short picks, which are a fatal drawback for woven fabrics, can be avoided. It has the excellent effect of being able to effectively prevent the occurrence of.

According to the second invention, by attaching the reset means to the follow-up control device, the reset means can forcibly clear the control deviation of the follow-up control device as necessary, so that the control deviation of the follow-up control device can be forcibly cleared. The first invention can be implemented.

[Brief explanation of drawings]

[Figure 1] Overall configuration schematic block diagram

[Figure 2]
Detailed block diagram of main parts (1)

[Figure 3] Detailed block diagram of main parts (2)

[Figure 4] Operation explanation diagram

[Figure 5] Main part block system diagram equivalent to Figure 3 showing another embodiment

[Figure 6] Explanatory diagram of the configuration of the length measuring device

[Figure 7] A diagram equivalent to Figure 4 in the conventional example

[Explanation of symbols]

A...Main shaft D...Drum M...Drive motor N...loom cycle Pa, Pf...rotation amount ΔP1...Control deviation a...Ratio θ…Crank angle θo...Set crank angle S1...Weft selection signal 1... Drive motor control device 2...Weft selection device 10...Following control device 20...Resetting means

Claims (4)

[Claims] 1. When controlling the rotation of a drive motor for driving a drum by following the main shaft at a predetermined ratio via a follow-up control device, a control deviation of the follow-up control device is cleared at least in a predetermined weft insertion cycle. A method for controlling a drive motor of a rotating drum type length measuring device for a loom, characterized in that: 2. A tracking control device that inputs the rotation amount of the main shaft and the rotation amount of the drive motor and controls the rotation of the drive motor by following the main shaft at a predetermined ratio, at least in a predetermined weft insertion cycle. A drive motor control device for a rotating drum-type length measuring device of a loom, which is provided with a reset means for clearing a control deviation of a follow-up control device. 3. The rotary drum type length measurement for a loom according to claim 2, wherein the reset means inputs a crank angle and clears the control deviation of the follow-up control device at a predetermined set crank angle. Device drive motor control device. 4. The resetting means inputs a weft selection signal from a weft selection device and determines a loom cycle in which a control deviation of the follow-up control device should be cleared. A drive motor control device for the rotary drum type length measuring device of the described loom.