EP0038927B2 - Method and device for regulating the unevenness of a sliver - Google Patents

Abstract

An autolevelling drawframe for levelling out staple fibre slivers in the spinning mill operation, in which deviations of the sliver weight (linear density) from the preset desired value detected are processed into correcting signals and are transmitted to a correcting member, which adapts the input speed of the drafting arrangement. The correcting signal transmitted is generated from the product of a voltage proportional to the rotational speed of the main motor and a voltage determined by the deviation in linear density. The apparatus consists of a computer (34,41; 60,41; 67,71) for computing the correcting signal, which computer is connected electrically with the correcting member (48), with a transducer (20) transmitting the voltage proportional to the rotational speed of the main motor, and with means for generating the voltage determined by the deviation in linear density. The computer can consist of a control device (36) and a multiplicator (41) or of a microprocessor (71) (digital computer).

Description

The invention relates to a method and a device for regulating the titre fluctuations of a fiber sliver, which is obtained by drawing in a drafting system from several individual slivers.

Regulating sections are already known in which a measuring device measures titer deviations of the strip at the end of the section, compares them with a setpoint value, and supplies the actuator with correction commands for detected deviations. This then changes the drawing-in speed of the drafting system and thus the main draft until the band number (titer) corresponds to the target value. Since the belt runs through the measuring element after the regulation has been delayed, the correction effect is automatically checked continuously. Such closed control loops guarantee excellent band uniformity (USTER NEWS, Bulletin No. 24, October 1976, page 1).

Although such regulation works perfectly in normal operation, it still has serious disadvantages. With today's high-speed lines, the line must be turned off each time the storage cans are changed so that a perfect change with clean belt separation is possible and high mechanical stress on the cans or the can changer can be avoided. The consequence of this is that a tape error occurs both when stopping and when starting again. This error inevitably arises when parking and starting, because the speed of the intake rollers of the drafting system is proportional to the speed of the delivery rollers of the drafting system due to auxiliary circuits, and the delay in these operating phases thus remains constant and the titer is not evened out. At the current discharge speeds of approx. 600 m / min, this error corresponds to approx. 20 m belt length when starting and approx. 10 m belt length when parking and is approximately the difference between the target and actual values of the infeed belts. Because the can change, for example when presenting cans with a small capacity, as required for open-end spinning, is carried out in an alternating rhythm of 2 to 10 minutes, the described error is particularly annoying here. The machine is started up and shut down very quickly in order to only have to generate the above-mentioned error over a short length. As a result, not only is the belt additionally stressed, so that there is a risk of a belt breakage, but the machine is also mechanically unduly stressed.

It is also known (DE-OS 24 48 512) to make the inertia of the control loop dependent on the throughput speed of the sliver in such a way that the control loop is fast at high throughput speeds and sluggish at low throughput speeds. This is to prevent the controller from overshooting or responding too late. A disadvantage of this type of control is that overcorrection takes place at very low throughput speeds, such as occur both when starting up and when switching off, which can result in considerable deviations in the sliver thickness.

In a further known drafting device for slivers with a regulating drafting device with an associated output device and regulating device for regulating the sliver thickness (DE-OS 26 50 287), an I-controller, which is matched to the operating speed, supplies a signal representative of the sliver thickness deviations, which has a signal which is dependent on the outlet speed of the Fiber band derived voltage signal is multiplied so as to obtain a control variable matched to the respective outlet speed. When starting up or shutting down, however, the controller is switched off, whereby it is ensured that the sliver thickness deviation signal which is last present at the output of the controller is stored and determines the delay of the drafting system both during shutting down and also during the subsequent startup. In addition to the fact that in this known warping device, any regulation during shutdown and start-up is completely dispensed with, a fiber band thickness which is currently present and which deviates greatly from the setpoint may cause a high correction signal at the moment the controller is switched off, which thus results in a complete correction signal during the entire shutdown and Start-up process is retained, so that a greatly changed sliver thickness can occur during start-up and shutdown and, depending on the value of the control variable at the time of shutdown, there may even be very different sliver thicknesses during shutdown and start-up.

Furthermore, a device for producing a uniform textile sliver is already known (DE-AS 2543839), in which a sliver supplied by a card is fed to a receiving device which is driven independently of the card. A regulating drafting device is arranged between the card and the receiving device, which has a pair of measuring rollers and an independently driven pair of drawing rollers, one measuring roller of the pair of measuring rollers being driven by the card and the other measuring roller being deflectable in accordance with the change in thickness of the sliver guided by the measuring rollers. The deflection of the measuring roller is used to control the drive speed of the pair of stretching rollers and the take-up device. In order to take into account the effects of changes in the speed of the card, the sliver thickness signal is passed through a multiplier, to which a signal representative of the speed of the card is also fed. This is a sliver thickness control that works depending on the fluctuations in the thickness of the sliver fed. Since the titer is measured in front of the drafting system, any irregularities that occur within the drafting system cannot be corrected. So there is not a rule problem, but a tax problem.

The object of the invention is to overcome the disadvantages mentioned with the aim of creating a method and an apparatus for regulating titre fluctuations in a sliver, in which no titer deviations and excessive stresses arise in the sliver both when starting up and when turning off, and also the. mechanical parts of the machine and the cans are only minimally stressed.

This object is achieved by the invention specified in claims 1 and 3, 8 and 11, respectively.

Due to the joint application of the change in the control speed with the throughput speed and the multiplication of the voltage determined by the titer deviation with the voltage proportional to the main engine speed, as well as the keeping of the control loop even when switching off and starting up, the operating speed down to standstill is optimally matched to the current one Throughput speed adapted sliver thickness control created.

• Fig. 1 den Streckwerksantrieb samt Schema einer Streckwerksregulierung in schematischer Darstellung,
• Fig. 2 ein Schema eines Reglers,
• Fig. 3 eine Variante der Vorrichtung gemäß Fig. 1,
• Fig. 4 ein Schema einer hierzu passenden Variante des Reglers,
• Fig. 5 ein Schema einer Digitalschaltung.

The invention is explained in more detail below on the basis of illustrated exemplary embodiments. It shows

• 1 is a schematic representation of the drafting system drive including a drafting arrangement regulation,
• 2 is a diagram of a controller,
• 3 shows a variant of the device according to FIG. 1,
• 4 shows a diagram of a suitable variant of the controller,
• Fig. 5 is a diagram of a digital circuit.

Distortionable staple fiber tapes 1, which are fed to a drafting device 4 of a regulating path (not shown) by means of pairs of rollers 2 and 3 of an inlet table (not shown), reach a tensioning delay of approximately 1.05 times at the speed _Velol . to the input roller pair 5, from there to a roller pair 6 running at a higher peripheral speed in relation to a selected preliminary draft, whereupon the main distortion takes place by means of the delivery roller pair 7 at the speed V. After leaving the main draft zone defined between the latter pairs of rollers 6 and 7, the fleece 8 formed in the drafting system is laterally combined into a compact belt 10 by means of a funnel 9 and fed to a pair of measuring rollers 11, 12. This pair of measuring rollers can consist of the driven roller 11 having a groove 13 and the complementary non-driven counter roller 12 which engages in the groove 13. The distance D between the pairs of rollers 7 and 11, 12 is approximately 10 mm in the lines which are common today. From there, the belt 10 arrives by means of a turntable 14 for storage in the can 15 placed underneath. This can be driven in rotation or stationary.

A main motor 16, designed as a stop motor, is used to drive all of the rollers and drives the roller pairs 7 and 11, 12 via the drive connections 17, 18 and 19 at a constant, reduced speed in a rigid ratio. This speed is such that the fleece 8 or the belt 10 is conveyed at a speed of 600 m / min to about 800 m / min. A pulse signal transmitter 20, which acts as a proximity initiator in a contactless manner and cooperates with an element (not shown) of the drive connection 17, supplies a signal proportional to the speed of the roller pair 7 or 11, 12 to a frequency / voltage converter 21, which supplies a corresponding voltage signal Un ₁₇ .

The drive connection 17 also transmits the rotary movement n ₁₇ via a differential gear 22 and via drive connection 23 at speed n to the driven rollers of the pairs 2, 3, 5 and 6 rotating in constant relation to one another. The differential gear 22 also has one with the variable one Speed n, driven drive connection 24 by a voltage-controlled DC motor 25, which also drives a control tachometer generator 27 via drive connection 26. Its outputs are electrically connected on the one hand to a motor control 29 via a speed monitor 28 and on the other hand to an adder 30. The measuring roller 12 is mechanically connected to a signal converter 31 which, in accordance with the deflections of the roller 12 caused by the strip thickness (= local titer), emits a representative signal via line 32 to an addition element 33, which is connected to a manually adjustable setpoint potentiometer 34, which delivers a voltage signal U _target . The adder 33 outputs a the Titerabweichung from Solltiter voltage signal proportional to AU = U _{target -U} via line 35 to a described in more detail below PI controller 36 from where it is transferred to a necessary for the control voltage U _R and a control area monitor 37 is supplied . This breaks the connection 38 to the engine control 29 when the set control range is exceeded. The controller 36 is also connected to the engine control 29 via line 39. A line 40 leads to a multiplier 41, which on the other hand receives the signal Un ₁₇ from the frequency voltage converter 21 via line 42. The controller 36 and the multiplier 41 together form an analog computer. The addition element 30 connected via line 43 to the multiplier 41 supplying the manipulated variable outputs its difference signal via a switch 44 to a power preamplifier 45 and then to the DC motor 25. The outputs of the motor control 29 each have a connecting line 46, 47 to the switch 44 and to the main motor 16. If the prescribed maximum speed of the DC motor 25 is exceeded, the speed monitor 28 causes the motor 25 to be switched off by the motor control 29. The parts 25, 27, 30 , 40 and 45 form the actuator 48, a closed control loop.

The structure of the controller 36 can be seen in FIG. 2. It consists of a slow PI controller 49, switchable for the stop-start phase, and from a fast PI controller 50, switchable for the normal operating phase.

für eine Verstärkerstufe 52 für den I-Anteil :

und der Regler 50 die Kenngrößen : für eine Verstärkerstufe 53 für den P-Anteil :

für eine Verstärkerstufe 54 für den I-Anteil :

The controller 49 has the following parameters: for an amplifier stage 51 for the P component:

for an amplifier stage 52 for the I component:

and controller 50 the parameters: for an amplifier stage 53 for the P component:

for an amplifier stage 54 for the I component:

The above-mentioned characteristic values are based on a travel distance Dw ≅100 mm, measured between the clamping line of the pair of rollers 7 'and that of the pair of measuring rollers 11, 12.

The switchover from the start to the normal phase and from this to the stop phase takes place via line 39, from the motor control 29 by means of a changeover switch 55. The operational amplifiers 56 present in the controller 36 are commercially available, e.g. B. Type 6P 3521 from Burr Browri, International Airport Park, P.O. Box 11 400, Tucson, Arizona, USA.

In the starting phase, the device now works as follows: The voltage AU supplied by line 35 initially reaches the slow regulator 49, then the regulator voltage supplied by it via the changeover switch 55, which is brought into the position shown in FIG. 2 by the motor control 29 , to the control area monitor 37. When the delivery speed V of z. B. about 500 m / min, the switch 55 is flipped, and the nimble controller 50 takes over the signal AU from line 35, whereby the normal working phase is initiated. When the route is switched off, the same happens in reverse order. Construction and operation with an additional slow controller 49 are required to avoid that the controller overshoots in the start and stop phase due to a lack of inertia (this is undesirable in normal operation) and the drafting device 4 therefore produces misalignments and band breaks. Both the controller 49 and the controller 50 have to be adapted to the changing operating conditions by appropriate setting. In the controller 49, an adjustment of the setting by means of the potentiometer 56a connected upstream of the operational amplifier 56 and the potentiometer 56b of the RC element to the acceleration and deceleration of the machine is required. This adjustment depends on the final speed to be reached. An adjustment to the material to be processed is necessary due to the distortion forces depending on the material. The inertia of the cans and their contents must also be taken into account. The current operating state, i.e. H. Whether the machine is already warming up or starting from a cold start also plays a role in the setting. When switching off, the influence of different wear of the brake pads in motor 16 (stop motor) must also be taken into account.

The controller 50 requires adjustment when the delivery speed changes, e.g. B. when switching from operation at 400 m / min to 500 m / min, by changing the corresponding potentiometers 56c and 56d. This adjustment work is time-consuming if no skilful operator is on hand. It should also not be forgotten that new settings should be made when the operating conditions change, which requires reliable personnel.

Otherwise, the device works as follows: in the multiplier 41, by multiplying the two voltage signals supplied by lines 40 and 42, the manipulated variable y required for regulating the titre fluctuations of the fiber sliver 10 is continuously determined, which is fed to the actuator 48, which in turn is supplied via the differential gear 22 has a corrective effect on the speed of the drafting rollers 2, 3, 5 and 6, so that fluctuations in the titre in the strip to be stretched are continuously adjusted until the desired value is reached.

When starting, the main drive motor 16 accelerates from standstill to its constant operating speed n, to which n _{17 is} in a fixed ratio given by change gears (not shown). The motor control 29 is provided with a time switch device (not shown), as a result of which the control circuit is switched on when the main motor 16 is switched on and is only switched off again when the main motor 16 is at a standstill. In this way, when starting and stopping of the distance of the rule engine forming DC motor is electrically coupled to the drive motor 16 25, this because the pulse signal generator 20 continuously n the instantaneous value of the rotational speed during starting and stopping of the _currently Roll pair 7 detected, so that the product of the signals U _R x U ₁₇ is continuously formed in the multiplier 41, which is necessary for the regulation of the corresponding titer deviation. Thus, the speed of the rollers 2, 3, 5, 6 is automatically tracked proportionally to the speed of the rollers 7, 11, 12 and a perfect start-up or braking is achieved.

das dem Multiplikator 41 als titer- und liefergeschwindigkeitsabhängige Größe eingeht. Der Regler 60 und der Multiplikator 41 bilden wiederum den Analogrechner.The construction and the mode of operation of the device according to FIG. 1 can be further perfected in order to eliminate the skillful adjustment work by the delivery speed V ₁ , ie the speed, generated by the pulse signal generator 57 (FIG. 3). n ₁₇ proportional frequency is supplied to the frequency / voltage converter 58, which supplies a voltage U ₅₉ via line 59 to a PI controller 60. The signal from line 59 (FIG. 4) reaches multipliers 61 and 62, while that from line 35 reaches multiplier 61 and a multiplier 63. Multiplier 61 supplies a signal V ₁ × ΔU (titer) of an amplifier stage for P component 64, and multiplier 63 receives a signal V ₁ ² from multiplier 62 and a signal AU from line 35 and outputs their product V ₁ ² . ΔU to the amplifier stage for the I component 65. Both amplifier stages 64 and 65 each have an operational amplifier 66, type 2521 L from Burr Brown. The multipliers 61-63 are types 4203 of the same origin. The signal emitted on line 40 thus corresponds to the sum

which the multiplier 41 receives as a titer and delivery speed-dependent quantity. The controller 60 and the multiplier 41 in turn form the analog computer.

In the devices according to the invention, the required speed change of the DC motor 25 is automatically proportional to the titer deviation and proportional to the speed of the strip 10 when starting up and coasting down, that is, the speed at which the strips 1 run in changes in proportion to the speed of the strip 10, and thus the main delay is as desired , regardless of the speed n ₁₇ , the control parameters change automatically when starting up from sluggish to quick and vice versa when turning off. This means that the controller is optimally set for every delivery speed without manual intervention. Since starting and stopping can be mastered independently of the speed of the drafting rollers, the starting and stopping processes can be carried out slowly (ie per 5-10 seconds, corresponding to a tape exit speed of up to 800 m / min). This leads to a very significant reduction in mechanical stress due to the absence of abrupt braking and starting up the machine and to a reduction in the risk of belt breakage.

The analog circuits shown in FIGS. 3 and 4 can advantageously be replaced by the digital circuit shown in FIG. 5 described below. The elements 20, 31, 34 and 57 and the line 32 correspond to those of FIG. 3. They thus have the same reference numerals in FIG. 5.

A peripheral board 67 consists of an analog-digital converter (not shown) (e.g. Burr Brown Type ADC 85-12) for the input of the analog actual value signal (line 32) from the signal converter 31, a circuit (not shown) for Reading in digital data (e.g. type SN 74 LS 241 from Texas Instruments Inc., MOS Microcomputer Products, Box 1443 MS 6404, Houston, Texas 77 001, USA) for digital input from lines 68, a frequency-time Converter (not shown), consisting of commercially available oscillators and counters for the signals from lines 69 and 70 and corresponding auxiliary circuits (not shown) for decoding the addresses and generating the necessary control, control and auxiliary signals, a digital-to-analog converter (not shown) (e.g. Burr Brown.DAC 71-COB-V) for the output (line 43) (manipulated variable y).

definiert ist. Darin bedeuten c₁ und c₂ Konstanten, V_einl. die Einlaufgeschwindigkeit des Faserbandes beim Walzenpaar 5, T die Integrationszeit.A microprocessor 71 (for example Texas Instruments, type TM 990/100 M) which interacts with the circuit board 67 is connected to data bus lines 72, address bus lines 73 and control bus lines 74. The microprocessor 71 contains, by means of a plug-in EPROM memory 75 (eg type TMS 2716 from Texas Instruments Inc.), the necessary computing program, which is determined by the control algorithm

is defined. Here c ₁ and c ₂ mean constants, V _einl . the infeed speed of the sliver in the pair of rollers 5, T the integration time.

The circuit board 67 now processes the input signals as they are called up by the microprocessor 71 and exchanged via the data bus line 72, the address bus line 73 and the control bus line 74 and transmits the calculation result in the form of the manipulated variable y to line 43, which it passes on to the actuator 48.

This digital solution has a number of special advantages: 1. Exact numbering of the delivered sliver over a long period of time and regardless of the environmental conditions in the spinning mill (e.g. air temperature, humidity) due to the elimination of the drift of electronic components. The control, readjustment and re-calibration are not necessary, which is of great importance given the lack of suitable personnel in the spinning mill.

2. High flexibility in operation

A program change, e.g. B. new control algorithm or other parameters, can be accomplished extremely simply by replacing the Eprom memory. If desired, an additional feedforward control can also be easily implemented.

3. The assumption of additional control functions, eg. B. Detection of a tape break, calculation, registration, display and possibly monitoring of the Cy values of the delivered tape without much additional effort.

Claims (12)

1. Method for compensating titer variations of a fibre sliver in the form of a single sliver drawn in a drafting mechanism of an evener drawing frame from a plurality of fibre slivers, the titer of the single sliver being measured at the delivery from the drafting mechanism, being compared with a set value and a signal proportional to titer deviations being fed to a controller which feeds corrections commands to the adjusting element by means of an adjustment quantity, said element varying the sliver infeed speed via a differential gear driven by a main motor and by a control motor until the set value has been reached, characterised in that the adjustment quantity fed to the adjusting element (48) is formed by the product of a voltage proportional to the speed of rotation of the main motor and a voltage determined by the titer deviation ; and in that on starting up the control parameters automatically change from damped to quick acting and vice versa on stopping.

2. Method in accordance with claim .1, characterised in that the voltage determined from the titer deviation is produced during starting up and stopping of the drawing frame by a P-I-controller contained in the said controller and adequately damped to avoid over-shooting, and is produced during the normal operating phase by a quick acting P-I-controller which is likewise contained in the above said controller and which keeps deviations from the set value minimal.

3. Apparatus for carrying out the method of claim 1, characterised in that a computer (34, 31) is provided for forming the adjustment quantity from the product of the voltage proportional to the speed of rotation of the motor, which is delivered from a generator (20), and the voltage determined from the titer deviation, and the computer (36, 41) is electrically connected to the adjustment element (48) to transfer the adjustment quantity and the adjustment element is mechanically connected to the infeed roller drive (23) via the differential gear (22) ; and in that the controller (36) comprises a damped P-I-controller (49) which can be switched in in the start-up and stopping phases and a quick acting P-I-controller (50) which can be switched in in the normal operating phase.

4. Apparatus in accordance with claim 3, characterised in that the damped P-I-controller (49) has the characteristics

for a spacing of the drafting mechanism outfeed roller pair (7) from the measuring roller pair (11, 12) of ca. 100 mm.

5. Method in accordance with claim 4, characterised in that the quick acting P-I-controller (50) has the characteristics

for a spacing of approximately 100 mm between the drafting mechanism outfeed roller pair (7) and the measuring roller pair (11, 12).

6. Apparatus in accordance with claim 3, characterised in that the controller (36) is connected to a motor control (29) for the purpose of switching over from the starting up and stopping phases to the normal operating phase.

7. Apparatus in accordance with claim 3, characterised in that the motor control (29) controls both the adjusting element (48) and the main motor (16) and is connected with both a control region monitor (37) and a rotational speed monitor (28).

8. Apparatus for carrying out the method in accordance with claim 1, characterised in that a computer (60, 41) is provided for forming the adjustment quantity from the product of the voltage proportional to the speed of rotation of the motor, which is delivered by a generator (20), and the voltage determined from the control deviation, and a computer (60, 41) is electrically connected to the adjusting element (48) to transfer the adjustment quantity and the latter is connected mechanically to the infeed roller drive (23) via the differential gear (22) and in that the controller (60) has a P-I-characteristic and is additionally connected to the signal generator (57) which delivers a signal proportional to the output speed V₁ of the drawing frame (fig. 3).

9. Apparatus in accordance with claim 8, characterised in that the P-I-controller (60) automatically sets the characteristics

in dependence on the voltage supplied to it proportional to the delivery speed, with a spacing of ca. 100 mm between the last drafting mechanism roller pair (7) and the measuring rollers (11, 12).

10. Apparatus in accordance with claims 3 and 9, characterised in that the computer (36) is formed from the controller (36, 60) which takes up the voltage representing the titer deviation and a multiplier (41) which is fed from the controller (36, 60), with the multiplier (41) being connected, on the one hand, to the adjusting element (48) and, on the other hand, to the generator (20).

11. Apparatus for carrying out the method of claim 1, characterised in that a computer (67, 71) is provided for forming the adjustment quantity from the product of the voltage proportional to the speed of rotation of the motor, which is delivered by a generator (20), and the voltage determined from the titer deviation, and the computer (67, 71) is electrically connected to the adjusting element (48) to transfer the adjustment quantity and the latter is mechanically connected to the infeed roller drive (23) via the differential gear (22) ; and in that the computer (61, 71) is formed by a microprocessor (71) which is connected to the generator (20), to the means (31, 34) which delivers the signal determined from the titer deviation, and also to the adjusting element (48).

12. Apparatus in accordance with claim 11, characterised in that the microprocessor (71) operates with the following control algorithm

wherein _C1 and c₂ are constants, V_in is the infeed speed of the fibre sliver into the drafting mechanism and T is the integration time.

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