Modeling and Siulation on Soft-starting for AM Driving Belt Conveyor 1 Yunxia Li, Zengcai Wang, 3 Wanzhi Zhang 1, First Author School of Mechanical Engineering,Shandong University,China, lyyffr@16.co *,Corresponding Author School of Mechanical Engineering,Shandong University,China, wangzc@sdu.edu.cn 3 School of Mechanical Engineering,Shandong University,China, zhangwanzhi@163.co Abstract In order to start belt conveyor softly, Autoated Mechanical ransission (AM) is applied to a new starting device. he siulation odel of AM driving belt conveyor is established by the coercial software AMESi. he dynaic siulations of start-up process at first gear condition and shifting process fro first to eighth gear are discussed. Single paraeter is accepted as the law of gearshifts in which belt velocity is used as the controlled paraeter to judge the oent of shifting. Siulation results show that the belt controlled with the equal acceleration (0. /s ) could achieve the purpose of softstarting of AM driving conveyors successfully. he belt appears short-tie acceleration utations during shifting process which results in the belt axiu tension, the driving pulley torque, and other paraeters changing within their allowable liits. he belt axiu tension is about 60 KN when the belt is accelerated with the equal acceleration (0. /s ) stably. he belt axiu tension appears short-tie utations when the clutch is just engaged, in which case the peak value of belt axiu tension can achieve 110 KN approxiately, and is less than its allowable liit. After shifting actions, the belt axiu tension and other paraeters curves tend to be stable. Keywords: Autoated Mechanical ransission, Belt Conveyor, Soft Start, Dynaic Siulation 1. Introduction Belt conveyors are widely used in the fields of etallurgy, ining, food, ports and cheical engineering. So far, ost of soft-starting devices for belt conveyors are variable frequency speed regulating, fluid coupling, AC otor soft starter, and liquid viscous speed regulating differential frequency speed regulating. hese soft-starting devices are ostly prices higher, and restricted by external condition, such as high-voltage power supply. Recently, autoated echanical transission (AM) is being used in vehicles because of the advantages of low cost and higher efficiency. his paper provides AM as the soft-starting device on belt conveyors. Researches on soft-starting belt conveyors ainly focus on how to reduce the conveyor belt tension and tension changes [1-4]. Belt acceleration control has becoe research hotspots in recent years [5-9]. Research shows that belt acceleration can be influenced on belt velocity and belt tension. Weigang Song proposed four soft-starting concepts: (1) equal acceleration starting; () cobination cycloid starting; (3) cobined parabola starting; (4) trapezoid acceleration starting. He proposes that if the starting tie is short, the equal acceleration starting will get the iniu dynaic load coefficient. Considering the start-up process of belt conveyor is siilar to the vehicle s start, the equal acceleration control is adopted to control the soft-starting of AM driving belt conveyor.. Modeling of soft-starting for AM driving belt conveyor AM soft starting syste includes three-phase induction otor, AM, reducer and belt conveyor. he ain coponents of AM are clutch and transission. hree-phase induction otor provides power for belt conveyor. Equation of echanical property is ainly considered in odeling of three-phase induction otor. Gear ratios should be ainly considered in odeling of transission and reducer. Characteristics of disengageent and engageent should be taken into account in odeling of clutch. Motor torque is delivered to transission by eans of clutch which uses friction to transit torque. It is possible to odulate clutch pressure to International Journal of Advanceents in Coputing echnology(ijac) Volue5,Nuber8,April 013 doi:10.4156/ijact.vol5.issue8.58 515
affect torque transission during engageent. Mechanical properties of the belt are ainly considered in odeling of conveyor belt. he siulation odel is shown in figure 1 by AMESi..1 hree-phase induction otor Figure 1. Siulation odel of AM driving belt conveyor he paraeters are given by the electrical products catalog including rated power, rated speed, and axiu torque coefficient. herefore, echanical properties equation can be used to ake atheatical odeling for the three-phase induction otor. he echanical properties equation can be described as s s s s (1) Where is induction otor output torque, is the axiu output torque of induction otor, s is slip ratio of induction otor, and s is the slip ratio under the condition of axiu output torque. s s N 1 () Where s N and are the slip ratio at rated speed condition and the axiu torque coefficient respectively. he slip ratio of induction otor can be described as s n n 1 (3) n1 Where n 1 and n are synchronous speed and rotor speed respectively.. Belt conveyor Belt has visco-elastic characteristic which akes belt odel becoe coplicated. Maxwell and Kelvin odel are often used to ake belt odel [10][11]. Kevin odel is selected in this paper because ore data in ters of correlative coefficients of conveyor belt can be referred. As is shown in 516
figure, spring and daper are connected in parallel to describe Kelvin odel with visco-elastic characteristic. he stress-strain equations of spring and daper can be described respectively as E (4) 1 1 d (5) dt Where 1 and are stresses of spring and daper respectively, 1 and are strains of spring and daper respectively, E and are odulus of elasticity and daping coefficient respectively. hen the stress-strain equation of Kelvin odel can be described as d E (6) dt Where (7) 1 (8) 1 he driving force offered by the driving pulley ust be large enough to overcoe the running resistance of conveyor. he running resistance of belt conveyor can be described as F f F F F F (9) H N St S F f is running resistance of conveyor, Where resistance, F is hoist resistance, and St F S is special kind of resistance. F H is priary resistance, F N is additional ensioning force is related to the way of tensioning device. he types of tensioning devices are weight tensioning, stationary tensioning and autoatic tensioning. he inertia force of weight will affect the value of tensioning force when the belt conveyor is started or stopped. he autoatic tensioning device has coplicated structure and controlling principle. Consequently, stationary tensioning device is selected for its relative stable tensioning force in this paper. here are different requireents for iniu tensioning force under different load conditions. Moreover, the tensioning force is affected by the axiu driving force which is delivered by driving pulley. he tension scheatic of driving pulley is shown in figure 3. 1 F t ax Figure. Kelvin odel Figure 3. ensions scheatic of driving pulley he relationship between tensioning force and belt tension for driving pulley is shown in figure 4. he expression of tensioning force can be described as 517
s ( F ) (10) fs Where s is tensioning force, and driving pulley, and is loose edge tension at driving pulley. Where Ft ax e 1 F fs is running resistance of conveyor between tensioning device 1 t ax (11) F (1) Where F t ax is the axiu driving force delivered by driving pulley, is friction coefficient between belt and driving pulley, is surrounding angle between belt and driving pulley, and 1 is tight edge tension at driving pulley. 1 F fs.3 Clutch s Figure 4. Relation Scheatic Between tensioning force and driving pulley tension Belt acceleration can be controlled by eans of controlling clutch friction torque. Belt acceleration is generally controlled within the liit of 0.3 /s. In this paper, 0. /s is chosen as the belt acceleration for soft-starting of AM driving belt conveyor. As is known, clutch needs fast disengageent and slow engageent [1-16]. In view of clutch applications in vehicles, we use 0.1 second as the tie of clutch disengageent and 0.4 second as the tie of clutch engageent. In other words, the value of clutch torque is increased fro zero to the corresponding target linearly at one gear position, and the value of clutch torque is decreased fro the target to zero linearly to wait for shifting. Clutch friction torque needed at one gear position is described as C ( F f Lab ) D (13) igi0 Where C is clutch friction torque, belt acceleration, D is diaeter of driving pulley, g reducer, and is echanical efficiency of the total driving syste..4 ransission L is equivalent load quality of total driving syste, a b is i is gear ratio of transission, i 0 is gear ratio of It is known that transission with synchronizer has nice perforance. We choose it rather than noral transission without synchronizer. o better the starting perforance, transission with eight 518
gears is chosen. It takes 0.3 second during shifting process which 0.1 second is used as the tie of disengaging one gear and 0. second is used as the tie of engaging one gear..5 Main paraeters Rated power and rated speed of the three-phase induction otor are 110 kilowatt and 1480 r/in separately. he gear ratios of transission are 14.8, 10.6, 7.87, 5.87, 4.375, 3.6,.43, and 1.80 orderly. he gear ratio of reducer is 10. he belt data is described as follows. It is 400 eters in length. It is flat belt. he belt specification is S-150 with a belt width of 100 illieters and the ass per unit length of 6.64 kilogras per eter. he freight volue is 1600 tons per hour. he odulus of elasticity is 150 N/. here are ainly six pulleys on the conveyor. Diaeter and oent of inertia for driving pulley are 1 eter and 6 kg separately. he tail pulley and the tensioning pulley are identical which diaeter and oent of inertia are 800 illieters and 87 kg separately. here are two bend pulleys on both sides of the tensioning pulley. Diaeter and oent of inertia for the two bend pulleys are 630 illieters and 38 kg separately. heir surrounding angle is 90 degrees. he paraeters of rollers are as follows. Its diaeter is 133 illieters. he grove angle is 35 degrees. he spaces of upper rollers and under rollers are 1. eters and 3 eters separately. Mechanical efficiency is ignored in order to siplify odeling. 3. Siulation analysis he ost coplex condition of conveyors is full load condition. So we ainly take full load condition into account to analyze the siulation results which include the curves for otor, clutch, transission, driving pulley and conveyor belt. 3.1 Siulation analysis of start-up process at first gear position he first disengageent of clutch is scheduled as the zero oent before the gear position shifted to first gear. he tensioning force is applied at negative ten seconds before zero oent, and the otor is started at negative two seconds before zero oent. he iportant research points are belt velocity and acceleration during the start-up process at first gear position. As is clearly shown in figure 5, the curves of belt velocity are set out which rises stably at fist gear position. he velocity of rear belt has delay phenoenon. Figure 6 shows the curves of belt acceleration which depicts that the front port and the rear port have different acceleration during startup process. he belt axiu acceleration is less than 0.3 /s at fist gear. Figure 5. Belt velocity curves at first gear Figure 6. Belt acceleration curves at first gear 3. Siulation analysis during shifting process fro first to eighth gear position As is known, it should be considered driver s intervention and engine conditions on vehicles. Multi-paraeters are adopted for shift schedule on vehicles. AM is only used as the soft-starting device for belt conveyor in this paper, so the belt velocity is chosen as the single paraeter for shift schedule. AM syste copletes shifting operation when the belt velocity reaches the final target 519
velocity. We use the induction synchronous speed to calculate the belt target velocity for each gear position in table 1. he flow path of shift process is shown in figure 7. Start Belt velocity tracking Shift yes or no N Y Shifting operation End shift arget belt velocity at eighth gear position Figure 7. Flow Path of shift process able 1. Belt target velocity fro first gear to eighth gear position gear position 1 3 4 5 6 7 8 belt target velocity (/s) 0.54 0.79 0.984 1.319 1.770.376 3.187 4.303 According to the requireents of soft-starting, we need to observe the changes of ain characteristic paraeters. In this paper, the ain paraeters are belt velocity, belt acceleration, tight edge tension at driving pulley (or the belt axiu tension), driving pulley torque, transission output torque, clutch output torque, and induction output torque. Using AM as the soft-starting device is to ake the conveyor belt creep fro low velocity to high velocity via shifting gears gradually. he dynaic tension of belt should be as low as possible. he induction otor output torque should be steady. hen we discuss and analyze the curves in details. otal siulation tie is 40 seconds in which shifting operations of eight gears are finished in sequence. Siulation deonstrates that AM syste can fulfill the ai of soft-starting for belt conveyor. Figure 8. Belt Velocity and Belt Acceleration Curves during shifting process 50
Figure 9. ight edge tension and torque curves at driving pulley during shifting process Firstly, belt velocity and belt acceleration curves are shown in figure 8. With the increase of gear position, the belt speeds up stably. he belt velocity has a slight decline during shifting process owing to the inertia of belt conveyor. he belt conveyor has not power delivered fro otor when the clutch is disengaged. he belt velocity achieves 4.303 /s when the siulation tie reaches 9.08 seconds. he final belt velocity reaches 4.313 /s and runs soothly. Copared with the belt controlled acceleration (0. /s ), the value of belt acceleration utations can reach 1.8 /s during shifting process. It is caused by gear position change and clutch engageent. In a sense, it is inevitable for AM, but it is feasible to softly start belt conveyor if the ipacts are endurable. Secondly, the influence of acceleration utations is studied. Belt tension and driving pulley torque of belt conveyor are discussed. It is shown that the tight edge tension at driving pulley also has utation phenoenon in figure 9. he belt axiu tension can reach 110 KN during shifting process fro first to eighth gear position. By contrast, the tight edge tension of belt is about 60 KN when the belt acceleration keeps 0. /s steadily at one gear position. he longitudinal tensile strength of belt is 150 N/, that is to say, the belt can support longitudinal tension of 1500 KN farthest. So the belt axiu tension does not exceed the liit of belt longitudinal tension. It can be seen that the driving pulley torque also has utation phenoenon in figure 9. he driving pulley torque can reach 45 KN during shifting process which is within the allowable torque liit of 5 KN, while the noral torque is about 0 KN when the belt acceleration keeps 0. /s steadily at one gear position. For this reason, we can dee that the driving pulley could withstand the ipacts of acceleration utations. Figure 10. orque curves of driving devices 51
Figure 11. Speed curves of driving devices Finally, the ain curves of driving devices are discussed for otor, clutch and transission. orque curves are shown in figure 10 and speed curves are shown in figure 11. heir torque changes are related to the belt acceleration. With the increase of gear position, the induction otor output torque and clutch output torque increase. he otor output torque curve changes soothly, but the clutch output torque and transission output torque change concussively. he proble is resulted fro the disengageent and engageent of clutch during shifting gears. When the clutch engages, the clutch powers the transission and conveyor which akes ipacts on each relative coponent of the syste. his is the reason of belt acceleration utations during shifting process. With the increase of gear position, the induction output shaft speed and the clutch output shaft speed decrease. his is because there is relationship between the otor output torque and its output shaft speed, which can be found in forula (1). After the copletion of belt accelerating, the induction output shaft speed is stable and its value is 1483. r/in. 4. Conclusion he paper describes the atheatical odeling and siulation of AM driving belt conveyor. Equal acceleration control is used to control the belt acceleration through clutch torque control. Siulations deonstrate that AM can be used as soft-starting device to start the belt conveyors. he driving pulley torque and the belt axiu tension are within their allowable liits under the condition of equal belt acceleration control (0. /s ). he belt acceleration appears short-tie utations during shifting process which arouses ore curves fluctuate. It is inevitable for AM syste which results in changes of dynaic load in shifting. he proble of belt acceleration utations can be solved better by eans of appropriate clutch engaging law. So, we find that AM can be used as softstarting device to softly start the belt conveyor. 5. References [1] Weigang Song, Yongsheng Deng, Zhaoxing Peng, et al, Siulation of the starting process of belt conveyor, Journal of Northeastern University (Natural Science), China, Vol. 19, No. 3, pp. 31-315, 1998. []. W. Zur, Viscoelastic properties of conveyor belts-odelling of vibration phenoena in belt conveyors curing starting and stopping, Bulk Solids Handling, Vol. 6, No. 3, pp. 553-560, 1986. [3] A. Harrison, A. W. Roberts, echnical requireents for operating conveyor belts at high speed, Bulk Solids Handling, Vol. 4, No.1, pp. 99-104, 1984. [4] L. K. Nordell, he channer 0 k overland-a flagship of odern belt conveyor technology, Bulk Solids Handling, Vol.11, No.4, pp. 781-79, 1991. [5] Yujin Li, Dynaic analysis and soft starting design of belt conveyor, Journal of China Coal Society, Vol. 7, No. 3, pp. 94-99, 00. [6] Weigang Song, Hongyi Liu, Ying Wang, Research on Dynaic and Coputer Siulation of the Belt Conveyor, Chinese Journal of Mechanical Engineering, Vol. 39, No. 9, pp. 133-138, 003. 5
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