Abstract- This paper presents a high accuracy and precise controllable laser based autoleveller draw frame and deals with a new cutting edge technology in textile mills. When correlating with the conventional electronic draw frame, the proposed system has compact in nature and data can be easily controllable. The entire system can be connected to a PC which will act as a closed loop control system that is controlling signal from PC will be sent to the servo driver thereby servo motor. Wide range of control, high accuracy and centralized or distributed control networks are the key advantages of the proposed system.


I. INTRODUCTION

Drafting is the process of elongating a strand of fibers, with the intention of orienting the fibers in the direction of the strand and reducing its linear density. In a roller drafting system, the strand is passed through a series of sets of rollers, each successive set rotating at a surface velocity greater than that of the previous set. During drafting, the fibres must be moved relative to each other as uniformly as possible by overcoming the cohesive friction. Uniformity implies in this context that all fibres are controllably rearranged with a shift relative to each other equal to the degree of draft.

The parallel arrangement of fibres in the sliver is taken care by the draw frame to which 4 to 8 card slivers are presented. Feed roller pair taken care of the slivers. The slivers then running into the drafting arrangement consisting of three pairs of rollers forming the back and the main draft zone. The card short term Auto leveler is being a proposed project of this paper. The auto leveler using laser beam detection is going to be implemented rather than conventional electronics system. The proposed system may give a better result in terms of performance and also cheaper in cost. The control signals applied to servomotor and their process can be simplified. The proposed auto leveller leveling the card silver for highly efficient card processing cotton, chemical fibres and their blends. The proposed system will have a future of on-line system by comparing chosen quality parameters of the feed and delivery livers.

II. CONVENTIONAL AUTO LEVELLER SYSTEM

A pair of tongue and groove rollers called as scanning rollers senses the thickness of the incoming sliver. Open loop control system is used in conventional auto leveling systems. Displacement transducer converts this angular movement into voltages. A plate is connected to the rollers and is moved into the Electro magnetic field of the transducer. This movement of the plates cuts the flux and a voltage is induced. This signal is transferred to the electronic memory, which then transmits it to the set point stage with a certain delay.

The correction delay is determined by the pulses, which can be set by FIFO (First in First out). The distance between the measuring rollers and the front draft zone is divided into 177to 192 pulses. FIFO is a register with the first measured variation stored in the first register and so on. This system ensures the change in the draft takes place exactly when the corresponding deviating length of the sliver passes the main draft zone. The set point stage uses the measuring voltage and the machine speed, which may be measured by two Tachogenerator to calculate the speed of the servo drive. The middle roller is driven by a differential gear arrangement, which has a constant drive from the front roller and variable speed from the servomotor. The correction length is further reduced for effective autolevelling. Speed of the variable speed motor is continuously measured and it does not correspond with the intended speed the machine is switched off. Accurate leveling is ensured by the high dynamic servo drive [1]. The basic block diagram of conventional auto leveling system is shown in Figure1. This system comprises of electronic unit, control drive using servomotor with control Tacho generator with constant Tacho transducer, measuring trumpet, transformer, Actuator and actuator controllers and break resistance, and a capacitive measuring unit.


A. PRINCIPLE OF MEASUREMENT AND AUTO LEVELLING SYSTEM

In case of short-term variations, a control circuit with dead time and P-controller with delay and a capacitive measuring unit are capable of doing the job in a perfect manner. In case of medium and long-term variations, a closed control loop with dead time and PI- controller can be used. A measuring unit can be used on request.

The draw frame Autoleveller was the first to achieve universal acceptance. In these systems the measurement is made either at the input or the output sliver. The sliver count is automatically corrected with reference to the required value by variation of the draft. A version of Uster ADC system is used to level the sliver input and output. In this system count of the sliver at the output stage is measured. The Autoleveller detects deviations, if any, from the pre-set nominal value. If deviations are determined, the actuator changes the input speed of the drafting rollers changing the draft in proportion to the control signal. The Tacho-generator at the input roller and the actuator controller ensure that the actuator corrects the count in proportion to the deviation. The degree of correction is automatically and continuously checked. This is a closed loop system, which controls the mean sliver count and guarantees the best possible accuracy. The length of the sliver over which correction of count takes place as the `correction length'. This corresponds to approximately 6 times the distance between the measuring point and the autolevelling correction point. The time taken by the sliver to travel between these two points is called the `dead time' [2, 3].

B. STORAGE OF THE MEASURED VALUES

The measured values transmitted in phase with the sliver movement to an electronic memory. The correction value is immediately transmitted via a highly dynamic servo drive to the feed system. An epicycle gear super imposes the constant speed of the main motor with the variable speed of the servo drive. The signal in the correction computer actuates a change in Autoleveller draft as soon as the measured part of the sliver enters the drafting zone. Even with high delivery speed of 900 m/m, the correction speed is twice that of the quickest cross sectional changes normally occurring in the sliver.

III. INTERNATIONAL STATUS

At international level, Rieter, Toyoda, Marzoli, Trutzschler & Vouk are the some of the familiar Textile machinery manufacturing company who are manufacturing the electronic auto leveler draw frame. All the above said companies are manufacturing the machines with the mechanical tongue and groove scanning discs as the sensing element, which has lot of disadvantages. With the help of indigenously developed technology we can prevail over all the disadvantages and it can be fully automated, so that the technology can be competed with foreign players. This auto leveler draw frame machine can be easily marketed through out the world at reasonable price.

IV. CURRENT STATUS IN INDIA

Presently auto leveler machines are manufactured in technological collaboration with foreign manufacturers. Present day draw frame manufacturers are manufacturing the electronic auto leveler with the mechanical tongue and groove roller scanning principle. The machine manufactured by this concept will have high national value and no need to depend upon the foreign technology. It can be indigenously designed fabricated and manufactured with high-speed laser beam scanning technology, high production, and superior quality, less manpower and economic cost. But some of the disadvantages are incorporated in this system that may overcome by the proposed project.

V. TECHNOLOGY

Draw frame consists of mechanical tongue and groove roller arrangement which is used for the measuring the material thickness in the auto-leveler system. In some auto levelers they are using pneumatic controls for closed loop auto leveling system. The mechanical system has so many disadvantages like slow in response, minimum deviations, fiber rupture, etc. Even in the case pneumatic control close loop system group drive is used for controlling the speed. In this project, open loop laser beam controlled auto leveling system, it incorporates laser beam for the sliver thickness measurement in which all the mechanical parts are eliminated. Also thickness is accurately measured with high speed operation. Direct laser beam with LDR is involved for the sliver thickness measurement, it is represented by the induced voltage in the LDR which is then amplified and used for speed controlling. Because of this arrangement conventional method of using transducers for thickness measurement can be eliminated. High speed controller and servo motors are used to control the quality of the output sliver [4]. Instead of group drive mechanism for speed controlling, individual drive concept is used in the drafting system leads to accurate control drafting rollers which improves the quality of the output sliver. The system also incorporates a PC for storing all the data in user friendly manner

A. OPERATION OF A LASER BEAM SYSTEM

Figure 2 shows the design and development of laser based auto leveller drawing frame. The data which are stored in processor can be connected to a PC to control the entire system.



This gives one more advantage that, even these data can be transmitted (using SCADA or FOC) to a centralized monitoring station from which the plant may be controlled. Light dependent resistance principle is used to measure the thickness of the double sliver here [5]. High intensity Laser beam is projected towards the doubled sliver. This arrangement will be placed in the feeding zone. At the receiving end there will be light dependent resistor which resistance value will get changed according to the laser signal received. The intensity of light received will vary according to sliver thickness. Received electrical signal will be the direct representation of sliver thickness.

The electrical signal from the LDR is amplified and converted into digital by means of ADC. Hence digital signal can be processed easily. For processing the digital signal DSP will be used. From DSP the control will be transferred to the speed control elements which controls the drafting roller speed according to the sliver thickness measured. For every 1 mm, the feed silver variations can be measured and controlled by means of the high speed electronic circuits [6]. The controlling process will continued through out length which yields uniform quality of material output. Since the DSP is connected with PC, monitoring of the quality and production is managed by it.


B. FUNCTIONAL BLOCK DIAGRAM

Figure 3 shows the functional block diagram of the lased based auto leveller drawing machine. From fig.3, we conclude that the given system can be monitored by a PC. A control algorithm can be developed and stored in the PC which will control the entire system.



VI. CONCLUSION

The proposed paper may enhance to a centralized networking applications where the data stored in the PC can be shared to some other systems. The data may be shared using SCADA, FOC or wireless transmission. This will provide a controllable system even when the draw frame is located in remote areas. In future this technology may replace the existing system though the cost of the proposed system is comparable. The on going research may provide comparable cost based system and more research has to be done in processor area for fast and reliable control of the system.

REFERENCES

[1] Grosberg.P..Iype.C. "The automatic control of Card Web linear density" Part 1 Textile Institute 1992.No.3
[2] Idzik.M. "Optimization of Work parameters of a short term autoleveller" Fibres and Textile 2000, No.4
[3] McAllister. I, "Parkclate moves up to a new quality level" Textile World 2003, No.5
[4] Yermolin, N.P, "Small Electrical Machines", Rajkamal Prakashan Private Ltd., Delhi 1963.
[5] Cyril G Veinott, Joseph E Martin, "Fractional and Sub fractional Horsepower Electric Motors", McGraw Hill International Editions, New Delhi, 1987
[6] John Webb, Kevin Greshock, "Industrial Control Electronics", Merrill Publishing Company, USA, 1990.