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Starter Motor
Описание: Starter Motor Motor starters are usually fitted with a trip device which deals with overcurrents from just above normal running current of the motor to the stall current. The aim should be for the device to match the characteristics of the motor so that full advantage may be taken of any overload capacity. Equally, the trip device must open the starter contactor before there is any danger of permanent damage to the motor. Contactors are not normally designed to cope with the clearance of short-circuit conditions, and it is therefore usual for the contactor to be backed up by HRC fuses or by circuit-breaker. The arrival on the scene of very compact motor starters and the need to provide proper back-up protection to them has posed a problem. BS EN 60947-4-1 (1992) (previously BS 4941) ‘Motor starters’, describes three types of co-ordination, the most onerous condition (type C) requiring that under fault conditions there shall be no damage to the starter or to the overload relay. The usual back-up device will be the HRC fuse. It is important that the user check with the manufacturer's catalogue to ensure that the correct fuse is used to secure this co-ordination. The starter motor in your automobile is a DC motor. If you were to accidentally reverse the battery polarity, the DC motor would still rotate in the same direction. Reversing polarity of the battery will not cause the motor to rotate in the opposite direction. To reverse the direction of rotation of this type of motor, either the current through the stator winding or the current through the armature must be reversed. Reversing both of them will result in the same magnetic polarities between the armature and the stator poles. This results in the same direction of rotation. The industry's standard for reversing the direction of rotation of a DC motor is to reverse the direction of the current through the armature. When a DC motor has more than one set of windings, shunt and series, as well as interpoles, the currents through all the stator windings would need to be reversed in order to change direction of rotation. This is far more complicated than merely reversing armature current. All engines require a toyota starter motor to turn them over before firing. In conventional vehicles, this is a straightforward, but powerful, direct-current electric motor. When the starter switch is activated by the driver, current flows to a solenoid attached to the starter motor. This current moves a lever into the solenoid that then causes a cogwheel of the motor to mesh with the teeth on the circumference of the flywheel. At the same time, an electrical contact is closed to allow a large current to flow and rotate the starter motor as well as the engaged flywheel. Typically, currents of hundreds of amperes are required to start the engine and are provided by the battery, which is generally a 12-V lead–acid module. The battery is recharged by the alternator–rectifier combination when the engine is running. Automotive batteries have improved enormously over the years and have far longer lives than formerly, even though they may be called upon to power many more functions. Although guarantees may be for two or three years, in practice batteries often operate for eight years or longer before failing. Moreover, modern car batteries no longer require periodic ‘topping-up’ with de-ionized water. Further information on the evolution of the lead–acid battery is given in Section 7.4, Chapter 7. A starter motor is required to run the internal combustion engine up to a speed sufficient to produce satisfactory carburation. The starter motor is mounted on the engine casing and a pinion on the end of the BMW starter motor shaft engages with the flywheel teeth. The gear ratio between pinion and flywheel is about 10:1. A machine capable of developing its maximum torque at zero speed is required. The series wound motor has speed and torque characteristics ideal for this purpose. The engagement of the pinion with the flywheel is effected in different ways. Perhaps the two most commonly used are the inertia engaged pinion and the pre-engaged pinion methods.
Дата Публикации: 03-11-21
5 of the best yoga pants: Health benefits and risks
Описание: 5 of the best yoga pants: Health benefits and risks Wearing yoga suit while exercising may make a workout more comfortable and therefore more enjoyable. It may also prevent overheating. That said, it also carries some health risks. This article discusses the health benefits and risks of wearing yoga pants, what to look for, some of the best options available to buy online, and alternative gym clothing to consider. Yoga pants describe a variety of different styles of pants, from formfitting leggings to looser trousers. However, nearly all yoga pants have some stretch to them due to the materials that they contain. Many yoga pants contain materials that wick moisture from the body and promote airflow. The moisture-wicking technology prevents overheating by keeping body temperature stable during exercise, while ventilating fabrics increase airflow. A 2014 studyTrusted Source found that synthetic polyester was more beneficial than a 100% cotton T-shirt in terms of both breathability and moisture-wicking. This may suggest that yoga suit-summer made of synthetic material, such as polyester and elastane, may prevent overheating and promote airflow. This in turn may make workouts more comfortable, especially in warm or hot environments. Health risks of wearing yoga pants The stretchy material in yoga pants should not feel too tight or limit movement, as restrictive clothes can contribute toward musculoskeletal disorders. For example, a 2016 studyTrusted Source found that males wearing tight pants are at a greater risk of musculoskeletal disorders, because they cause abnormal movement and posture in the lumbar spine and pelvis. While this study focused on males and restrictive clothing, especially around the waist, it suggests that wearing flexible and comfortable clothing may decrease the risk of abnormal movement and posture. Wearing tight or formfitting yoga pants may also lead to other conditions: Yeast infection Some people may develop a vaginal yeast infection. Certain clothes, such asTrusted Source those that are too tight or use synthetic materials, are factors in people developing this infection. Tight clothes and sweating allow the yeast that naturally occurs in the vagina to thrive, which leads to inflammation. Learn more about yeast infections here. Tinea cruris Another condition that people may develop while wearing yoga suit-autumn is tinea cruris, or jock itch. Excessive sweating, restrictive clothing, and not showering properly after exercise are risk factorsTrusted Source for developing this condition. People wearing tight yoga pants that do not have moisture-wicking or breathable fabrics may be at risk of jock itch. Learn more about jock itch risk factors and prevention here.
Дата Публикации: 03-11-21
Yoga Equipment Guide for Beginners
Описание: Yoga Equipment Guide for Beginners When you first start doing yoga, it's hard to know what you really need to buy. The yoga mat continues to develop so much clothing and equipment that you might feel you need to spend hundreds of dollars before ever stepping foot in a studio. The good news is, you actually need very little to get started. That said, if you're starting a home practice, or you'd feel better purchasing yoga-specific apparel and equipment prior to your first class, here's what you need to know. It should go without saying that most aerial yoga accessories want you to wear something to class, but you don't need scores of printed yoga pants or designer gear to be accepted by your peers. Start with the comfortable, breathable athletic apparel you already have on hand, and purchase mid-level basics for anything you're missing. Pants or Shorts: You can't go wrong with a few pairs of solid-color yoga pants in black, dark grey, navy, or brown. You can mix-and-match these tights with a wide variety of tops, and if you purchase high-quality options, they can last a long time. If tight pants aren't your thing, look for jogger-style pants or the popular harem-style pants that have elastic around the ankles. These pants are stretchy and offer a little extra room, but due to the ankle elastic, they'll stay in place throughout your practice. Shorts are a popular option for guys, and they're also appropriate for women, especially if you plan to try hot yoga. Just keep in mind, you may want to wear form-fitting spandex shorts or looser shorts with connected tights underneath because some poses require you to position your legs in a way that could leave you uncomfortably uncovered with looser, running-style shorts. Tops: It's important to wear tops that are fairly form-fitting so your shirt doesn't fly over your head during forward bends. Wicking material is helpful, especially if you tend to sweat a lot or if you plan on attending a hot yoga class. Because yoga rooms are sometimes kept cool, you may want to bring a light cover up or sweater with you to class. You can wear it until class starts, and if you keep it by your mat, you can put it on before the final savasana. Sports Bras: If you're a woman, make sure you wear a sports bra. While TPE yoga mat tends to be a low-impact activity, a decent sports bra can help keep your "girls" in place as you transition between poses, making your practice more comfortable. Hair Ties or Headbands: Whether you're a man or woman, if you have long hair, you need to secure it in place before you start class to prevent stray locks from falling in your eyes and face. A basic hair tie or headband should do the trick. Yoga Socks: To be clear, yoga socks are not a requirement to attend a class. In fact, it's preferable to do yoga barefoot. That said if you can't fathom the thought of taking your socks and shoes off in front of strangers, invest in a pair of yoga socks with grips on the bottom so you can keep your feet covered while maintaining good traction. Standard socks absolutely won't do, as you'll end up slipping and sliding all over your mat. These days, you can buy yoga apparel practically anywhere, and it's not unusual to see yoga pants priced at over $100. Don't feel you need to lay out that much cash for a single pair of pants! Target, Amazon, and YogaOutlet offer quality options for well under $50. Buy a couple pairs of pants and a few tops, and you'll be set for months. As you commit yourself to your practice, you may decide to add trendy prints or styles to your wardrobe. In gyms and yoga studios, it’s commonplace to use a yoga mat, also called a sticky mat. The mat helps define your personal space, and, more importantly, it creates traction for your hands and feet so you don’t slip, especially as you get a little sweaty. The mat also provides a bit of cushioning on a hard floor. Most gyms provide mats and studios have them for rent, usually for a dollar or two per class. This is fine for your first few classes, but the disadvantage to these mats is that lots of people use them and you can't be sure how often they're being cleaned, so you may consider buying your own. Premium yoga mats can be expensive, often around $80 to $120, but it's possible to find a starter mat for as little as $20 from retailers like Target and Amazon. Just keep in mind, if you decide to buy a cheaper mat, you'll probably find yourself replacing it in short order if you use it often. If you're really ready to commit to a yoga practice, your mat is one place it's worth it to lay out some cash. Decide which mat features are important to you—for instance, length, thickness, material, durability, comfort, traction, or how to keep it clean—then buy a mat with good reviews based on your needs. Manduka and Lululemon are known for the quality of their Pro Mat and The Reversible Mat, respectively, but other brands, including Jade and Yellow Willow, also offer high-quality, durable mats with good traction and support. Yoga props are a boon to a fledgling suede yoga mat practice. Props allow students to maintain the healthiest alignment in a range of poses as the body bends, twists, and opens up. They also help you get the most out of each pose while avoiding injury.1 You should familiarize yourself with the props described below, but you don't need to buy your own (unless you're starting a home practice) because they are almost always provided by studios and gyms.
Дата Публикации: 03-11-21
Circular Knitting Machine
Описание: Circular Knitting Machine The term knitwear includes two main textile techniques, weft and warp knitting (Spencer, 2001; Weber and Weber, 2008) (Table 7.1). After weaving, it is the most common method of manufacturing textile fabrics. Because of the interlooped structure of the knitted fabric, the properties are completely different to woven fabrics. The difference in weft and warp knitting originates in the way the needles move during the production and in the way the yarn is supplied. Weft knitting is a one fibre technique, which means that only one fibre is needed to build the stitches. The needles are moved separately, whereas the warp knitting needles are moved simultaneously. Therefore, all needles need the fibre material at the same time. For this reason, the yarn is supplied with the help of warp beams. The most important knitwear fabrics are circular knitted, warp knitted, flat-knitted fabrics and fully-fashioned fabrics. The specific features influencing yarn delivery on large-diameter single jersey circular knitting machine are high productivity, continuous knitting and a great number of simultaneously processed yarns. Some of these machines are equipped with a striper (yarn guide exchange), but only a few enable reciprocated knitting. Small diameter hosiery machines have up to four (or occasionally eight) knitting systems (feeders) and an important feature is the combination of rotary and reciprocal movement of the needle bed (beds). Between these extremes are the middle diameter machines for ‘body’ technologies. Figure 4.15 shows the simplified yarn supply system on a large-diameter double jersey circular knitting machine. Yarns (1) are brought from the bobbins (2), passed through the side creel to the feeder (3) and finally to the yarn guide (4). Usually the feeder (3) is equipped with stop-motion sensors for yarn checking. The knitted textile structure evolves from loops that are intermeshed row after row. The needle hook is responsible for the formation of a new loop with the supplied yarn. During the upward movement of the needle in order to catch the yarn to build a new loop, the old loop slides down the needle (Fig. 7.20). This causes the opening of the needle. The needle hook is now open to catch the yarn. The newly built loop is drawn through the old loop from the previous knitting circle. During this movement, the needle is closed. Now the old loop can be released as the new loop remains in the needle hook. The creel of the knitting machine controls the placement of yarn packages (bobbins) on all machines. Modern large-diameter circular machines use separate side creels, which are able to hold a large number of packages in a vertical position. Floor projection of these creels may differ (oblong, circular, etc.). If there is a long distance between the bobbin and the yarn guide, the yarns may be threaded pneumatically into tubes. The modular design facilitates the changing of the number of bobbins where required. Small-diameter machines with a smaller number of cam systems use either side creels or creels designed as integral to the machine.
Дата Публикации: 03-11-21
Towards understanding the improved stability of palladium supported on TS-1 for catalytic combustion
Описание: Towards understanding the improved stability of palladium supported on TS-1 for catalytic combustion A novel Pd supported on TS-1 combustion catalyst was synthesized and tested in methane combustion under very lean and under highly humid conditions (
Дата Публикации: 03-11-21
State of the art baby strollers
Описание: State of the art baby strollers The current work is an attempt to design and fabricate an ergonomic baby stroller with the latest state of the art features. A review on the design of baby strollers in the previous years was done ranging from the year 1980 to 2014. Based on the review it was found out that the idea of a foldable frame emerged since the early 1980s where people started to prioritize space saving. The use of electronics devices in strollers has not been properly implemented due to the bulkiness of the battery and the clutter mess of wires. Infant’s safety and comfort has always been the number one priority by designing a seat that is contoured to a baby’s spine, ultimately making baby’s growth much safer. In lieu of the current work, a harmonious prototype design was fabricated using Rapid Prototyping system. The idea was to fuse the usage of electronics with the stroller by inventing modular “plug and play” attachment devices that provide customizability to baby strollers which include headlights and cooling fan attachments. Besides that, the latest state of the art designs of the ergonomic baby stroller such as a ventilated back rest, on-board rocking baby chair, bidirectional push handle with ergonomic grip support, frame with integrated hooks for storing different types of “plug and play” attachments and hooks for attaching the foldable stroller to a typical standard shopping cart were implemented. Baby strollers are increasingly popular among the generations of baby boomers. Despite the popularity, the state of innovations in the design of baby strollers has plateaued in recent years. This article illustrates the evolution of the design of baby strollers from the year 1980 to 2014. Based on the review, it was found out that the idea of a foldable frame emerged since the early 1980s where users started to prioritize space saving. The use of electronics devices in strollers has not been properly implemented due to the bulkiness of the battery and the clutter mess of wires. In lieu of the current work, the idea was to fuse the usage of electronics with the 3 in 1 stroller by inventing modular “plug and play” attachment devices that provide customizability to baby strollers that include headlights and cooling fan attachments. The possibilities of various types of attachments will be endless. There is significant design knowledge of baby strollers since 1980 to 2014, in which, is reviewed to identify flaws and advantages of each design. There are many methods used to transport babies around and it varies among different cultures and countries. The idea of infant transportation emerges as multitasking and convenience becomes a necessity in parent’s everyday lives. Having an infant transportation made it easier for parents as babies are no longer needed to be carried by the parents or sit on top of their parents’ back. Babies that are lacking the ability to support their head still and upright are usually carried with slings. Cradleboards are popular among Native Americans to keep babies secure and comfortable (Garrett, McElroy, & Staines, 2002). The early stroller was developed by William Kent in 1733. William Kent designed the pockit stroller to be clam shaped and it was richly decorated and meant to be driven by a small animal such as a goat. Benjamin Potter Crandall saw the potential of this and was the first person in America to sell baby strollers commercially in 1830s. His son, Jesse Armour Crandall further improves the design by adding brake to carriages, designing a frame that is foldable, and a frame that receives devices such as an umbrella (Amato, 2004).
Дата Публикации: 03-11-21
Paper Bag Making Machine: The Ultimate Guide
Описание: Paper Bag Making Machine: The Ultimate Guide I know you’re looking for a paper bag making machine that’s why you are here. Maybe, you want to be a paper bag wholesaler or make branded designs for your retail business. The truth is, paper bags are dear packages for food vendors, retailers, and even manufacturers. But, how can you venture in this business? Or, what is the most cost effective way of making paper bags? Today’s guide debunks the facts behind paper bag making process and machine such basic definition, working principle, classification, design, technical specification, etc. So stay with me to be an expert in paper bag making industry. Let’s begin with some facts. Apart from the other devastating problems associated with plastic bags, did you know that synthetic bag manufacturers produce about one trillion of those bags in a year globally? Did you also know that it takes one thousand years for a single bag of this kind to biodegrade? Yes, that’s the scariest part of it. Due to that, most governments are imposing bans on these carriers. The alternative? A mega-shift to more environmentally friendly paper bags. So basically a plastic shopping bag making machine is a state of the art machine that gathers, folds, stamps, and processes papers to produce clean paper bags. These paper bags are for use in the packaging of goods in various industries such as food, pharmaceutical products, grocery, and baking industries. The plastic t shirt bag making machine come in various configurations depending on the type of bags for final production. Therefore, the paper bag making system should be versatile enough to cater to the dynamics in the paper bag manufacturing. Today different paper bag making stakeholders such as the machine manufacturers, raw material suppliers face a lot of shifting customer demands, government regulations, changing prices, etc. It’s thus good only if the machine can afford the manufacturer some relief. For that matter, it means that you need to know all the factors related to the paper bag making the machine. Besides, all the accompanying dynamics before making a purchase. Luckily, I have compiled all that you need to know in this article. The history of development and use of eco friendly carry bags manufacturing machine dates back to the 19th century. During these early stages, the systems were simple and mechanically operated.
Дата Публикации: 03-11-21
How a laser printer works
Описание: How a laser printer works Have you ever tried writing with a beam of light? Sounds impossible, doesn't it, but it's exactly what a CO2 laser printer does when it makes a permanent copy of data (information) from your computer on a piece of paper. Thanks to sci-fi and spy movies, we tend to think of lasers as incredibly powerful light beams that can slice through chunks of metal or blast enemy spaceships into smithereens. But tiny lasers are useful too in a much more humdrum way: they read sounds and video clips off the discs in CD and DVD players and they're vital parts of most office computers printers. All set? Okay, let's take a closer look at how laser printers work! Laser printers are a lot like photocopiers and use the same basic technology. Indeed, as we describe later in this article, the first laser printers were actually built from modified photocopiers. In a photocopier, a bright light is used to make an exact copy of a printed page. The light reflects off the page onto a light-sensitive drum; static electricity (the effect that makes a balloon stick to your clothes if you rub it a few times) makes ink particles stick to the drum; and the ink is then transferred to paper and "fused" to its surface by hot rollers. A laser printer works in almost exactly the same way, with one important difference: because there is no original page to copy, the laser has to write it out from scratch. Imagine you're a computer packed full of data. The information you store is in electronic format: each piece of data is stored electronically by a microscopically small switching device called a transistor. The printer's job is to convert this electronic data back into words and pictures: in effect, to turn electricity into ink. With an inkjet printer, it's easy to see how that happens: ink guns, operated electrically, fire precise streams of ink at the page. With a 30W CO2 laser printer, things are slightly more complex. The electronic data from your computer is used to control a laser beam—and it's the laser that gets the ink on the page, using static electricity in a similar way to a photocopier. When you print something, your computer sends a vast stream of electronic data (typically a few megabytes or million characters) to your laser printer. An electronic circuit in the printer figures out what all this data means and what it needs to look like on the page. It makes a laser beam scan back and forth across a drum inside the printer, building up a pattern of static electricity. The static electricity attracts onto the page a kind of powdered ink called toner. Finally, as in a photocopier, a fuser unit bonds the toner to the paper. Millions of bytes (characters) of data stream into the printer from your computer. An electronic circuit in the printer (effectively, a small computer in its own right) figures out how to print this data so it looks correct on the page. The electronic circuit activates the corona wire. This is a high-voltage wire that gives a static electric charge to anything nearby. The corona wire charges up the photoreceptor drum so the drum gains a positive charge spread uniformly across its surface. At the same time, the circuit activates the laser to make it draw the image of the page onto the drum. The laser beam doesn't actually move: it bounces off a moving mirror that scans it over the drum. Where the laser beam hits the drum, it erases the positive charge that was there and creates an area of negative charge instead. Gradually, an image of the entire page builds up on the drum: where the page should be white, there are areas with a positive charge; where the page should be black, there are areas of negative charge. An ink roller touching the photoreceptor drum coats it with tiny particles of powdered ink (toner). The toner has been given a positive electrical charge, so it sticks to the parts of the photoreceptor drum that have a negative charge (remember that opposite electrical charges attract in the same way that opposite poles of a magnet attract). No ink is attracted to the parts of the drum that have a positive charge. An inked image of the page builds up on the drum. A sheet of paper from a hopper on the other side of the printer feeds up toward the drum. As it moves along, the paper is given a strong negative electrical charge by another corona wire. When the paper moves near the drum, its negative charge attracts the positively charged toner particles away from the drum. The image is transferred from the drum onto the paper but, for the moment, the toner particles are just resting lightly on the paper's surface. The inked paper passes through two hot rollers (the fuser unit). The heat and pressure from the rollers fuse the toner particles permanently into the fibers of the paper. The printout emerges from the side of the copier. Thanks to the fuser unit, the paper is still warm. It's literally hot off the press!
Дата Публикации: 03-11-21
Design and Analysis of a Novel Tension Control Method for Winding Machine
Описание: The filament winding technique has evolved in recent decades moving from classical lathe-type towards winding with an increased number of degrees of freedom using more complex equipment. These advancements complicate the selection of an optimum toroid winding machine set-up for the realization of particular winding methods and correlating part designs. This is further complicated by the variety of approaches. In order to investigate existing equipment technologies regarding feasibility, operational and economic aspects, different filament winding equipment is established in an experimental environment. Thereby advantageous solutions can be assigned to particular winding methods and the selection of appropriate filament winding equipment is facilitated. Filament winding has emerged as the main process for carbon fiber reinforced plastic (CFRP) fabrication, and tension control plays a key role in enhancing the quality of the winding products. With the continuous improvement of product quality and efficiency, the precision of the tension control system is constantly improving. In this paper, a novel tension control method is proposed, which can regulate the fiber tension and transport speed of the winding process by governing the outputs of three different driven rollers (the torque of the unwind roll, the torque of the magnetic powder brake roller, and the speed of the master speed roller) in three levels. The mechanical structures and dynamic models of the driven rollers and idle rollers are established by considering the time-varying features of the roller radius and inertia. Moreover, the influence of parameters and speed variation on fiber tension is investigated using the increment model. Subsequently, the control method is proposed by applying fiber tension in three levels according to the features of the three driven rollers. An adaptive fuzzy controller is designed for tuning the PID parameters online to control the speed of the master speed roller. Simulation is conducted for verifying the performance and stability of the proposed tension control method by comparing with those of the conventional PID control method. The result reveals that the proposed method outperforms the conventional method. Finally, an experimental platform is constructed, and the proposed system is applied to a gear toroidal winding machine. The performance and stability of the tension control system are demonstrated via a series of experiments using carbon fiber under different reference speeds and tensions. This paper proposes a novel tension control method to regulate the fiber tension and transport speed. High modulus carbon fiber is an excellent industrial material, which is widely used in several fields such as satellite supporting cylinder, shells of rocket engine, and solar array. The composite manufacturing process is the key to the application of carbon fiber. Filament winding has emerged as the main process for fabricating composite structures. It is widely used in building rotational parts. In the filament winding process, the carbon fiber is delivered from the unwind roll and passed through the resin bath to mix with resin under different temperatures and finally wrap around the surface of the mandrel in the designed pattern. The major specifications that should be satisfied during the winding process are the winding line type and the fiber tension, which are considered to be the key factors related to the tensile strength of the fiber products. The winding line type is determined using the numerical control system, so this paper focuses on the tension control problem during the winding process. Researchers have shown that unstable tension may lead to loss in strength of fiber winding products . Therefore, fiber tension should be maintained at the reference value during the winding process for ensuring the product quality. Several factors shape the tension control design to be challenging, which include significant parameter variations and disturbances. Small variations in the change of velocity of the transport rollers can cause significant variations in tension. On the other hand, we used different shapes of mandrels for maintaining the line speed in acceleration or deceleration states. Because of the coupling between the tension and the line speed, it is difficult to maintain the tension at a desired value. Researchers have investigated considerably for acquiring better control result. Lee et al. used a magneto rheological brake to provide back tension to prevent frequent part changes and fatal malfunction for a tension control system, and a PID controller was designed, and test results showed the feasibility with satisfying the time constant and the allowable error. Nishida et al. divided the transport system into several subsystems and a self-tuning PI controller with an estimator based on a novel adaptive particle swarm optimization method was constructed to solve the strong coupling between the velocity and tension of the web. A self-tuning PID controller to control the tension for tape winding of composites was designed and the constant extension ratio is guaranteed. To reduce the time required for the stabilization of the tension, a faststabilization method for web tension is proposed. The model of dancer system and stabilization of web tension in drying process are established, and the variation of tension is used as a reference value for the tension stabilization. The integration of load cells and active dancer system for printed electronics applications was used to improve the accuracy of web tension, and self-adapting neural network control was proposed to reduce tension spikes due to the change in roll diameter of winder and unwinder rolls. Wu et al. developed a tension detection and control mechanism and analyzed the main causes of wire tension variation, and then a PI algorithm was proposed to reduce tension variation. An accurate dynamic model for the unwind roll by considering the time variation of the roll inertia and radius was developed, and a decentralized controller for computing the equilibrium inputs for each driven roller was proposed . A sliding mode control with guaranteed cost technique was applied for reducing the system uncertainties. The simulation results showed that the proposed method had good robustness and quick response time. Compensation method by calculating the torque of a driven loop lifter was developed to control the tension and thickness of hot-rolled strip. For the control strategy, several control methods have been proposed including disturbance rejection control , neuro-fuzzy control , and H∞ control . Choi et al. conducted a survey on various types of control algorithms by investigating their strengths and weaknesses, and demonstrated some areas of potential future development. Most of the above studies considered the dynamics of driven rollers in the models but the behavior of idle rollers was ignored. Consequently, the models were under some limited conditions, which ignored detailed complex tension dynamics. On the other hand, most research focused on dynamic modeling and control strategy design, but the mechanical structure and the influence of parameter variation on fiber tension were ignored. In this paper, a novel tension control method is presented, which can regulate the tension and speed of the filament winding process. The mechanical structure and dynamic model of the system are established, and the influences of the parameter and the speed variation on fiber tension are examined. Subsequently, according to the features of driven rollers and the influence of variation, the control method is proposed by regulating the outputs of the torque of unwind roll, the torque of magnetic powder brake roller, and the speed of the master speed roller in three levels. Simulations are conducted for verifying the effect by comparing the results with those of the conventional PID controller. Finally, the performance of the proposed control system is verified through experimental studies using a filament slider coil winding machine. The structure of the paper is organized as follows. Section 2 presents the mechanical structure of system. In addition, the dynamic models are constructed, and the influence of parameter and speed variation on the rollers is examined. In Section 3, the control strategy is proposed. Simulations are conducted for verifying the effect of the proposed controller by comparing with that of the conventional PID controller in Section 4. In Section 5, the proposed mechanical structure and control strategy are applied to a belt head winding machine, and the experimental study is conducted for verifying the performance of the tension control system. The process line is divided into three zones (Figure 1): the unwind section, the process section, and the rewind section. In each zone, one or two rollers are driven using motors for transporting the carbon fiber from the unwind roll to the rewind roll. The carbon fiber is delivered from the unwind section to the process section, which consists of the magnetic powder brake roll, the master speed roller, and some idle rollers. In the process section, the carbon fiber passes through the surface of the master speed roller. As the carbon fiber is comprised of thousands of threads, the resin is properly pasted on the surface of the carbon fiber. The master speed roller is driven using an AC servomotor, and the speed is controlled for acquiring the desired speed and tension. The rewind section consists of a four-axis CNC system for acquiring the winding pattern. The control method of hook type winding machine is shown in Figure 2 in three levels. The control system can regulate the tension and speed of the filament winding process by governing the output of three different driven rolls—the torque of the unwind roll, the torque of the magnetic powder brake roller, and the speed of the master speed roller. In the first level, the unwind roll, which is driven using a torque motor generates a reverse force for applying a pretension to the carbon fiber. The pretension is set at a small value because large tension will cause the tension to deviate from the set point owing to the time-varying radius and the disturbance caused by the periodic swing. In the second level, the magnetic powder brake generates another pretension to the carbon fiber. The feature of the magnetic powder brake is to generate torque in a wide range without introducing considerable tension interference. However, its disadvantage is that the accuracy and response speed are inadequate than the speed control using the AC servomotor. Finally, in the third level, as the tension is close to the set value, the master speed roller is controlled for acquiring the desired tension. On one hand, the speed of the master speed roller traces the line speed of the carbon fiber as the reference speed. On the other hand, the speed is adjusted for maintaining tension at a desired value. The response speed is high when the AC servomotor operates in the speed control mode. Consequently, when the line speed of the carbon fiber changes rapidly or in the start-time period, the master speed roller maintains tension in a small range. The control system measures the speed and tension of the carbon fiber, and then controls the multivariable output of the torque of the unwind roll, the torque of the magnetic powder brake roller, and speed of the master speed roller. The mechanical structure and dynamic modeling of the system is presented as follows.
Дата Публикации: 03-11-21