IROS2019国际学术会议论文集 1921

Abstract Doffing robot is an important part of the spinning process in the textile production This paper analyzes the doffing process of spinning machines and points out the requirements of the structure and functions of the doffer The locking two finger gripper the three dimensional circulating operation mechanism the collaborating locating mechanism with the toothed disc and the pre loosening mechanism by rotating spindles are designed On this basis the continuous vertical pulling automatic doffing robot named CVP doffing robot for the ring spinning is developed The kinematics and dynamics analysis of the CVP doffing robot are carried out The structural parameters of the CVP doffing robot are optimized by establishing kinematics and dynamics models The forces of pulling out cops before and after the pre loosing operation are tested On this basis the strength of the key components is designed and checked Finally the performance of the CVP doffing robot is verified by the doffing experiment Keywords doffing robot ring spinning vertical pulling gripper mechanism design I INTRODUCTION In recent years the relative number of labor force has declined enterprises are facing increasing risks of labor shortage An effective solution is to improve the automation level of the spinning workshop and reduce the use of manpower Nowadays one of the key links to improve the automation level in the spinning process is yarn dropping There are many kinds of movable doffing machines 1 2 but they all have the characteristics of simple structure low investment low power consumption and high efficiency In the long term production practice they improve the production efficiency and reduce the labor intensity of workers Internationally the representative mobile doffing machines are Mayer mother type doffing machine of Germany Meyer Company TAD type doffing machine of Japan Funghe Company and MD LS type doffing machine of Japan OKK Company 3 4 The reasonable reliable and stable holding of the yarn tube is the prerequisite for the successful yarn dropping of the yarn dropping machine The yarn gripper is a robot hand that holds the yarn tube From the shape there are many robotic hands suitable for holding yarn tubes each has its own characteristics but it needs to be improved on the existing robotic hands to meet the requirements of drawing yarn tubes Underactuated hand has been often used as yarn holder in doffing robot According to different grasping modes This research was supported by National Natural Science Foundation of China No 51575302 Beijing Natural Science Foundation No J170005 and National Key R 12 The 1st plane cam 13 Main drive shaft 14 space cam 15 The 1st balance cam 16 The 2nd balance cam 17 The 2nd plane cam According to the actual needs the doffing robot needs to have 9 functions bobbin gripping operation positioning pre loosening retention intubation walking detection and control On the basis of introducing the structure design of each sub function module this section designs the whole machine of CVP bobbin dropping machine as shown in Fig 5 Spindle Upper guide rail Empty bobbin Scissors mechanism Full bobbin Bobbin gripper Lower guide rail Dragon tendon Intubation mechanism Stereo Cycle Operating Mechanism Basket For empty bobbin Pre loosening mechanism of spindle Leaning wheel Rear wheel Basket for full bobbin Front wheel Frame x y z a Overall structure Upper guide rail Full bobbin Bobbin gripper ereo Cycle Operating echanism Frame x y Transverse motornsverse Linkage Mechanism Spinning frame Front wheel Leaning wheel Uppe guide rail Full bobbin Bobbin gripper Stereo Cycle Operating Mechanism Frame x y Transverse motor Transverse Linkage Mechanism Spinning frame b initial position c Working position Fig 5 The CVP doffing robot As shown in Fig 5 the whole machine of CVP doffing robot mainly consists of bobbin gripper stereo cycle operating mechanism disc coordinated positioning mechanism spindle pre loosening mechanism intubation mechanism scissors mechanism front and rear hanging wheel relief wheel main motor transverse movement mechanism and frame The main motor is installed in the doffing frame and its output shaft is fixed with the rear hanging wheel The front rear relief wheels are connected on the frame of the yarn dropping robot When the dropping machine works the front and rear wheels contact with the upper guide rail of the spinning machine and the lower guide rail which makes the frame of the bobbin dropping machine hang on the guide rail of the spinning machine When the CVP doffing robot works it is necessary to place the doffing machine at the head or tail of the spinning machine and make the front and rear doffing wheels contact with the upper guide rail of the spinning machine and the lower guide rail contact with the wheel The doffing frame is attached to the guide rail of the spinning machine Adjust the position of the doffing robot and start the transverse motor in the transverse mechanism so that the drawing mechanism moves in the opposite direction along the Y axis until the tooth shaped disc in the positioning mechanism contacts with the spindle foot convex platform of the spindle and engages accurately Then the main motor and the cooperative motor are started and the rear sprocket begins to roll along the upper guide rail which drives the doffing machine to move along the guide rail of the spinning machine as a whole When the doffing robot moves along the guide rail of the spinning frame toothed disc is driven by the spindle foot convex and rotates The rotation of the tooth disc drives the first drive shaft and the first sprocket of the bobbin dropping mechanism to rotate through the positioning transmission mechanism and then drives the chain movement In this way the vertical guideways fixed on the chain begin to move with the chain Because the slider the bobbin gripper and the roller are connected together the bobbin gripper will follow the spatial cam groove line for three dimensional rotary motion driven by the vertical guide rail in space The speed of the doffing machine is v0 and the speed of the gripper in the reference frame of the doffing machine is vg as shown in Fig 4 In order to ensure vertical drawing the horizontal component of bobbin gripper speed vg should be equal to the speed v0 of the doffing machine when the yarn holder is in the rising segment of the spatial cam When the gripper reaches position B P the gripper s raw is pushed by the second plane cam and the gripper opens until the gripper reaches the gripper area Then the gripper breaks away from the second plane cam and the gripper closes to realize the grip of the full bobbin Then the friction pad of the pre loosening mechanism contacts the spindle disc of the spindle corresponding to the full bobbin which makes the spindle rod and the full bobbin rotate relatively and realizes the pre loosening After that the bobbin gripper continues to move to the rising section of the spatial cam and the bobbin gripper rises together with the full bobbin gripper When the gripper moves to the upper horizontal section of the spatial 2728 cam the full bobbin is completely separated from the spindle and then the gripper drives the full bobbin away from the spinning frame into the unloading zone i e position C P v0 vg PB PC vg vg z x Fig 6 Dropping Process of the CVP doffing Before the gripper s moving claw contacts the first plane cam the tail bobbin of the full bobbin enters the cutting position of the scissors mechanism first The scissors mechanism cuts the tail bobbin and leaves the raw bobbin head so that the bobbin can be automatically wound on the bobbin after the next spinning process starts Then the gripper s claw is pushed by the first plane cam the gripper opens again the full bobbin is released and falls into the lower basket After that the bobbin gripper continues to move and returns to position B P after passing through the descending section of the spatial cam to start the next extubation Throughout the bobbin dropping process the gripper neither touches the bobbin nor damages the spindle III ANALYSIS OF THE DOFFING ROBOT Static and dynamic models are used to study the methods to ensure the positioning accuracy of the yarn dropping mechanism at different walking speeds and the relationship between the trajectory of the yarn holder and the position of the spinning frame On this basis the optimal design results of the parameters of the yarn dropping mechanism are obtained The working principle of the doffing robot is shown in the following figure Oxyz represents the global coordinate system the point O is fixed on the spindle root rrrr Ox y z is a local coordinate system based on point B the parameters and their corresponding physical meanings are shown in the figure Rd Chain w Major driving shaft Driven shaft First driving wheel Second driving wheel Yarn refining device Rw Rg a Rg y x ds xr yr Or O Rg min Rg max Rg Yarn gripper Yarn overbrimmed tube Spindle PA PB PC PD E FG Db Toothed disc Rw w wt v0 Db EG F Fig 7 working principle of the doffing robot According to the working principle one can conclude that r OAFBFA rrr 1 r OA 0g 0 T v tR r 2 In the equations above BF rrepresents the positon vector of point F in the rrrr Ox y z AF r represents the positon vector of point F in the local coordinate fixed on point A r OAr is the positon vector of point B in the global coordinate system The working process of the doffing robot can be dividedinto 4 steps by conducting kineamtcis analysis for each step the trajectory of the end effector in the robot can be concluded In the first step A P B P the cooresponding kinematics equations should be 1 0 tt 1w t 3 BF gwgwg sincos T RtRth r 4 Similarly in the second step the equations should be 212w 73 ttt t 5 When ww1c tanRttah BF ww1gg TRttRh r 6 When ww1c tanRttah ww1 BF g gcww1 tantan Rtt R hhRtta r 7 As for the third step the kinematical model should be 3w 103t 23 tt t 8 gw2 BF gw2 gc sin cos aRtt Rtt hh r 9 The kinematics equations for the last step should be 4w 143t 34 tt t 9 When ww3c tanRtth ww3 BF g gcww3 tan aRtt R hhRtt r 10 When ww3c tanRtth BF ww3gg TaRttRh r 11 2729 In order to arrange integer vertical guideways within the length range of the chain to ensure accuracy the following relationships need to be satisfied w1s1 2 1 2 3 Rn d n 12 w2s2 22 1 2 3 Ran d n 13 Taking the workspace of the doffing robot into consideration the values for 1 nand 2 nare slected as 6 and 14 accordingly In which 1 nrepresents the number of yarn grippers that can be arranged when the horizontal segment of the spatial cam is a complete arc 2 nrepresents the number of yarn grippers that is arranged in the whole robot During the working principle the speed of the chain should be 0ww vR 14 During the practical design process one set s 70mmd w1s 2 66 8mm Rn d b 18mmD g 140mmR g maxg 25165mmRR g ming 10130mmRR 2sw 2 280mman dR w 43 g 260mmh c 185mmh 30 According to the equations above the trajectory of the bobin gripper point F point G andrelationship among different parameters can be concluded as shown below Trajectory of Dropping Frame Grab the full yarn tube off the spinning frame and release it into the lower basket Vertical tube drawing Move toward the grab area Back to position PA then ready to start the next yarn drop x y z AB C D A B D C A Fig 8 The trajectory of the bobin gripper N N 1 N 2 x O BdsDb y 100 200 300 400 A Rg 120mm Rg 160mm Rg 200mm Rg 140mm Rg 180mm Fig 9 The trajectory of point G dg mm Interference area Fig 10 Relationship among g d t and g R IV EXPERIMENT OF THE DOFFING ROBOT To verify the design and analysis experiments of the doffing robot were conducted The experimental device for testing extrusion force FL without pre loosening is mainly composed of frame tension meter steel wire yarn tube and spindle as shown in Fig 11 The tension meter used has peak holding function Tensimeter Spindle root Spindle bar Bobbin steel wire Frame F Fig 11 Experimental device for measuring pullout force without pre loosening The results of the experiments are shown below Group number Group numberGroup number Group number Fig 12 Experiments for different bobbins The appearance of the CVP yarn dropper prototype is shown in Figure 13 In order to verify the actual performance of the doffing machine we have completed the test experiment of the doffing machine in the spinning workshop of a textile company The performance indicators tested are the drawing rate intubation rate and retention rate of the 2730 doffing machine In the experiment the number of spindles on one side of ring spinning frame is 228 The four groups of data recorded are the number of spindles that failed to extrude the number of spindles that failed to intubate the number of broken ends of yarn before and after dropping A total of 11 spinning frame 5016 spindles were extruded and intubated a b Fig 13 prototype of the doffing robot Experimental results show that the result basically meets the design goal and shows that the doffing machine has good working reliability and stability In addition according to the quality of yarn dropping it is shown that the spindle and yarn will not be damaged when the CVP yarn dropping machine drops the yarn the yarn dropping efficiency is comparable to that of the double disc yarn dropping machine which is higher than other similar products on the market and it is also superior to other similar products in terms of machine power consumption and its own weight V CONCLUSIONS The mechanical structure design of each subsystem of CVP yarn dropping machine was studied and a locking double finger yarn holder was designed Based on the locking double finger yarn holder a three dimensional circulating operation mechanism was designed and the structural design points and operation principle of the three dimensional circulating operation mechanism were introduced in detail In order to ensure the accuracy of drawing a simple structure based on the structure of ring spinning frame was proposed A reliable cooperative positioning scheme of the disc is put forward By simulating the pre loosening mode of the spindle and the yarn tube during artificial doffing a pre loosening scheme of the spindle with low energy consumption high reliability and no damage to the spindle is proposed Finally the overall structure of the CVP doffing machine is designed its working process is analyzed and the control system of the doffing machine is designed The kinematics and dynamics of CVP drop frame are analyzed the kinematics and dynamics model of drop frame is established the structure parameters of drop frame are optimized and the drawing force before and after pre loosening is tested by experiments On this basis the strength design and check of the key parts of the yarn dropping machine are carried out Finally the performance of the designed CVP yarn dropping machine is verified by the whole machine experiment 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