Abstract:
A process and a device for the correction of the regulation onset point and of the intensity of regulation relate to a regulated drawing frame of the textile industry, i.e. a drawing frame in which drafting can be regulated or can be changed in a controlled manner. A selected transient signal of the fiber sliver thickness starts the process for a limited time span so that, independently of the existing regulation, the response signal is detected at the drawing frame output and its difference with the input signal is evaluated in order to correct the regulation onset point and/or the intensity of regulation.

Description:
This is a continuation of U.S. application Ser. No. 07/983,579 filed Feb. 4, 1993 which was abandoned upon the filing hereof. 
    
    
     BACKGROUND OF THE INVENTION 
     The instant invention relates to a regulated drawing frame of the textile industry, i.e. a drawing frame in which draft is controlled or controllably adjustable. The concept of control comprises in this case the application of controls or of a multi-looped control system. 
     In this invention fiber slivers are processed and the thickness of the end-product must be uniform. It is the task of the control system to recognize a change in fiber sliver thickness and to bring it to the desired uniform thickness by drafting. 
     The thickness signals are detected at the measuring station before the inlet of the drawing frame. All along the subsequent course taken by the measured points in the fiber sliver, and up to the place where drafting occurs, the appertaining measuring signal is buffer-stored with a delay time. At the end of this delay time the control system intervenes immediately as a function of the deviation of the fiber sliver thickness. This onset of this control application is called the regulation onset point. 
     The problem in this case is that the regulation onset point must occur neither too early nor too late with respect to the onset of drafting because this would result in faulty drafting. Similarly, the intensity of regulation, i.e. the amplification, may be neither too low nor too high. 
     In practice, influences attributable to the machine or environmental influences are the cause that the drafting point cannot be determined precisely, and therefore errors occur in determining the regulation onset point and the intensity of regulation. 
     When erratic fluctuations of fiber sliver thickness occur, for example as a result of needle impulses exceeding the tolerance limits, the mechanical components are unable to follow quickly enough in driving the drawing frame rollers because of their inertia. Complete compensation for the variations in thickness is hardly possible in this case. The problem is aggravated by the existing need to increase the speed of the fiber sliver from an average of 500 m per minute to 800 m per minute and more. 
     Thickness fluctuations which increase very slowly over time are yet another extreme case. Here the reaction of regulation is also insufficient. 
     DE-OS 36 19 248 proposes that a correction value be determined for the delay period as a function of the steepness or the relative magnitude of mass fluctuation. The result is a shorting of the delay time as a function of the steepness and magnitude of the mass fluctuation. This solution has the disadvantage that the result of regulation cannot be checked. This is a disadvantage insofar as the correction made can be subject to influences attributable to the machine or by environmental influences. 
     The solution according to EP 412 448 proposes the utilization of a multi-looped control system on the drawing frame, whereby the measuring signal is detected and evaluated after the drawing frame output. The proposed solution here is to ascertain the result of controlled drafting change through supervision along the drawing frame course, to re-enter it into the same control system and to evaluate it in an optimization process broken down into low-frequency and high-frequency portions. The setting magnitude Y which is optimized by the main control is thus used as a setting value for the controller 8.2 of the drive of the main drafting zone 12 (EP 412 488, page 12, lines 12 -15). This solution is mainly based on the utilization of the measured values in order to always optimize the setting value. The clear drawback in this method is the fact that correction values to be used to set the setting values are not processed independently by the control system, and are therefore not free from influences. 
     To be able to detect changes in the regulation with certainty and independently of the regulation, the &#34;sliver test&#34; was conducted in the past. The &#34;sliver test&#34; is conducted by spot-checking and manually determining the correct levelling out of fluctuations in fiber sliver thickness. A test sliver is produced. The operator adds an individual sliver segment to the presented slivers or produces a limited sliver interruption through sliver breakage. The length of this created fiber sliver is cut out and its actual sliver thickness is determined by weighing (see instruction manual of the RIETER Spinning Systems, drawing frame RSB 851, SB 851, point 4.5.6, edition 8/1990). It is thus impossible to avoid an interruption of production counted in minutes. This is a considerable disadvantage in continuous production at high production speeds. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is the object of the instant invention to create a process and a device which improves the correction of the regulation onset point and of the intensity of regulation in regulating the drawing frame. Additional objects and advantages of the invention will be set forth in part in the following description, or will be obvious from the description, or may be learned by practice of the invention. 
     Contrary to existing control methods utilizing the FFT analysis to obtain correction values, the method according to the invention has as one of its characteristics the selection of merely individual occurrences of fiber thickness in order to start the process which functions independently of the existing control system in order to determine and to carry out necessary corrections of the control system (i.e. correction of the regulation onset point or of regulating intensity) within a predetermined time span. The process according to the invention is therefore not constantly in operation. The process is started up only when a special signal is detected and is stopped after a predetermined time span. 
     This process does not involve a feedback of the control magnitude in the sense of a closed control circuit or of an interference magnitude lock-on. 
     The process consists in obtaining a transient signal of the fiber sliver thickness at the measuring station. The transient signal must possess high amplitude so that it is evident during a sufficiently long period of time that the fiber thickness is exceeding tolerance limits. At the same time, this amplitude must be steep enough to differentiate from a constantly increasing fiber thickness, but be less steep than for a needle impulse. 
     This signal must resemble a surge signal. This surge signal is transmitted to the control system and is utilized at the same time to start the correction process of the regulation onset point and of the intensity of regulation. The response signal is detected as an impulse diagram at the drawing frame output independently of current regulation and its deviation from the surge signal is evaluated in order to correct the regulation onset point and the intensity of regulation. The process is terminated after a defined time span. 
     Parallel to the existing control system, component groups are installed in the device which make it possible to recognize a transient signal as well as to evaluate the response signal with respect to the regulation onset point and to the regulating intensity. 
     The advantage of the process consists in the fact that it functions independently and is therefore free of influences from an existing regulation. The correction value is thus defined more precisely, since internal machine influences and environmental influences upon the drafting point can be taken into account with greater precision. Linked to this advantage is the further advantage of partial automation of the &#34;sliver test&#34; , in that a test sliver is produced automatically without interruption of the production process. 
     Since the process requires the targeted selection of a random individual occurrence of abnormal fiber sliver thickness, the process requires no constant operating mode. 
     The functioning of the process and its interaction with a known regulating system is described below through figures in an embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a modular mimic display depicting the process and the device of the invention; 
     FIG. 2a is a representation of a surge signal; 
     FIG. 2b is a representation of reply signal wherein regulation onset is premature; 
     FIG. 2c is a representation of a reply signal wherein regulation onset is too late; 
     FIG. 2d is a representation of response signal wherein regulation onset is premature and amplification is excessive; 
     FIG. 2e is a representation of a response signal wherein regulation onset is premature and amplification is insufficient; and 
     FIG. 3 is a representation of modular mimic display depicting the process and the device without reserve sliver feed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the presently preferred embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. The numbering of components in the drawings is consistent throughout the application, with the same components having the same number in each of the drawings. 
     FIG. 1 shows the modular mimic display pertaining to the process according to the invention with the essential characteristics of the device. The fiber sliver 5 runs through a measuring station 1. This measuring station 1 can be a mechanical pair of scanning rollers, for example. The draw-in rollers of reserve sliver feed 3 together with reserve sliver 4 are shown upstream of the measuring station 1. The fiber sliver is drafted in drawing frame 6. At the output of the drawing frame a measuring station 2 is provided. The conventional regulating system 7 receives the measuring signals from measuring station 1. These measuring signals are stored in a measured-value memory 7.1 with an appropriate delay time and are then transmitted to an amplifier 7.2, with the signal being transmitted from the output of the amplifier 7.2 to an adjusting element 7.3. The adjusting element 7.3 changes the rotational speed of a pair of rollers in the drawing frame 6 so that drafting is changed. 
     A component group 8 was installed in the device to implement this described regulating system 7. This component group 8 of the process according to the invention functions parallel to and independently of the conventional control regulating system 7. Shown in the component group 8 are a regulating circuit 8.1, a measured-value evaluating unit 8.2, a counting and evaluating unit 8.3 and a mean-value former 8.4, a buffer memory 8.5 and a comparator 8.6. 
     It is the task of a reserve sliver feed system to avoid production stoppages caused by fiber sliver breakage or by sliver ends in a can. The function of the reserve sliver feed system 3 is transferred to another area of application for the purpose of the invention. The reserve sliver feed system 3 is used in double function as part of a device to carry out the process. 
     One of the ways to start the process is for the regulating circuit 8.1 to transmit a starting signal to the reserve sliver feed system 3. At the end of a defined period of reserve sliver feeding, the reserve sliver feed system 3 is stopped. The length of that period is equal to the time required for the process. 
     Another way to start the process is provided by the presented slivers themselves. This possibility is shown in FIG. 3. 
     The presented slivers themselves can produce a transient signal at the measuring station 1 upstream of drawing frame 6 through a random deviation in fiber thickness. For this it is necessary that the transient signal possess high amplitude. The amplitude must differ by approx. 10% from the mean value and a time span (at least three clocking impulses of the measuring impulse) must be present. This signal must be recognized. For this purpose a measured-value analysis system 8.0 is installed between the measuring station 1 and the regulating circuit 8.1 (FIG. 3). A comparison value is defined by the mean of the measured-value analysis system 8.0 by constituting long-term mean values of the measured values. When the comparison value is exceeded by at least 10%, this is recorded as a threshold excess by the measured-value analysis system 8.0. The amplitude in this case must last for at least three clocking impulses. Parallel to the detection of amplitude, its steepness is detected. When its steepness is at the same time increasing in surges, the required transient signal has been found. The detection of such a signal starts the process. The process is terminated after a predetermined number of clocking impulses. The number of clocking impulses corresponds to at least the time it takes to go from measuring station 1 to measuring station 2. 
     The process functions parallel to and independently of the existing control system. By connecting the reserve sliver 4, or as a result of random deviation of the fiber sliver thickness, a defined surge signal (represented in an idealized form) according to FIG. 2a is triggered. This surge signal is transmitted to measuring station 1 and the course of the output signal over time is detected by means of measuring station 2 at the output of the drawing frame 6. The output signal may for example take on idealized forms as shown in FIGS. 2b, 2c, 2d or 2e. The measured-values evaluating unit 8.2 which follows the measuring station 2 has two paths in its output, one path for the control of the regulation onset point, and another path for the control of regulating intensity. 
     Two amplitudes are detected (FIG. 2d) in the processing arm for the control of the regulation onset point in function of the impulse diagram of the response signal of two amplitudes, whereby the first amplitude in progression and phase position is generally used for evaluation. According to FIG. 2 the delay t and the difference -f (t) between the background level of control and the background level of the response signal are evaluated. These values are referred to in the result of the evaluation in component group 8 to rate the effectiveness of regulation. According to FIG. 1 these values are introduced as signals into the measured-values memory 7.1 or into the amplifier 7.2 of the existing regulating system 7 and thus make it possible to correct the parameters in the control system. 
     The following explanations concerning the feeding of the reserve sliver are given to further facilitate the understanding of the process. With the feeding of the reserve sliver 4, the measuring station 1 registers a sudden increase in fiber sliver thickness. This corresponds to the surge signal. As the leaping signal is detected at the measuring station 1, the regulating circuit 8.1 receives the information on the start of the process. At the same time the measured-value evaluating unit 8.2 starts the mean-value former 8.4. The latter detects first the signals which come into measured-value evaluating unit 8.2 at the measuring station 2 until the arrival of the response signal, i.e. of the corrected sliver. These constituted mean values are stored in the buffer memory 8.5. 
     As the first flanks of the response signal arrive, the mean value former 8.4 will again form mean values for the period of the response signal&#39;s passing. These mean values are however transmitted directly to the comparator 8.6 which now also receives the values from the buffer memory 8.5. The amount difference between the background signal level at the start of the reserve sliver and the background signal level delivered with the response signal is determined in the comparator 8.6. A possible difference found in this comparison corresponds to a measure of regulation intensity. The output of the comparator 8.6 is connected to an amplifier 7.2 which determines the intensity of amplification as a function of the amount difference and its polarity. 
     Together with the arrival of the flank of the first impulse of the response signal at the measuring station 2, the counting and evaluating unit 8.3 is started through the measured-value evaluating unit 8.2. After the passage of the first impulse of the response signal the counting and evaluating unit 8.3 is again stopped. This result is delivered into the measured-values buffer memory 7.1. The number of time pulses of the first impulse of the response signal supplies the characteristic for the magnitude of the wrong control setting. The phase position (polarity) gives an indication on the direction of the wrong setting, i.e. the onset point of control is too slow with a positive phase position, and too rapid with a negative phase position. The last impulse of the response signal is not taken into consideration. It is always a trailing impulse with a polarity contrary to the first one. The simplicity of this process step consists in the fact that the length of this counted impulse is already a measure for the control application onset point. This characteristic is transmitted to the measured-values memory 7.1 which simultaneously corrects the control application point in function of the characteristic. 
     It is characteristic for the counting and evaluating unit 8.3 that it is started and stopped by the measured-value evaluating unit 8.2 and that it functions according to a machine-dependent measuring phase 7.4. The machine-dependent setting of the phase 7.4 is synchronized with the fiber sliver speed so that the evaluation of the impulse diagram takes place at the correct moments. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.