【机械专业英文文献】轮式装载机工作装置的优化设计.pdf

optimum design of working device of wheel loader* yang yu, lianguan shen, mujun li department of precision machinery and precision instrumentation ustc (university of science and technology of china) hefei, anhui province, china lgshen abstractsome performances of zl50 wheel loader do not meet the requirements, like delivering ratio, translation feature in lifting and automatic reset of the bucket. an optimal strategy for working device is adopted based on a virtual prototype in adams. there are total 22 design variables which are 9 points (x, y) coordinates of the reverse six-bar linkage and two hydraulic cylinders extend and retract length in their axial direction. the simulation is focused on the affect of design variables on the performances of working device. four different combinations of design variables are selected in optimization based on their sensitivity on the optimum objectives. they are “all parameters”, “base on sensitivity”, “bucket unchanged” and “bucket and lift arm unchanged”. some robust optimal solutions with multi constraints are obtained. all the constraints are given some margin. the optimum results show that three end points of the rocker arm and the joint point of tilt cylinder on the frame play an important role in optimizing the performance of the structure. after comparison, the scheme “base on sensitivity” can get the optimal solution with relatively fewer variables. it optimizes the delivering ratio from 0.314 to 0.450, the translation feature in lifting from 24.6 to 12.3, the automatic reset of the bucket from 23.7 to 2.5. the improvement of the performances after optimum design is obvious. keywords-optimum design; wheel loader; working device; adams; sensitivity analysis i. introduction wheel loader is a kind of engineering machinery, which has been widely used in many construction projects such as roads, buildings, ports, mines and others, mainly for transporting and loading bulk materials. its work process is divided into four working phases: shovel, transport, unloading and flat down. the structure size of six-linkage working mechanism directly affects on the performances, such as translation feature in lifting, automatic reset, the ratio of delivering power, unloading angle, unloading height, unloading distance and bucket angle at carrying position, etc. it is extremely significant to obtain productive and dependable performances and a strong and robust main structure. reno filla presented simulation of complete machines for analysis and optimization of overall performance to develop products of equally high performance, efficiency and operational in a shorter time and at a lower total development cost, but with more robustness 1. rongyi zhang used genetic algorithm, ant colony algorithm and particle swarm optimization to optimize the work mechanism to make the ratio of delivering power maximum 2. hongzhong huang optimized the working device of loader based on satisfactory degree theory 3. yangmin li used huston method and software mbda to establish dynamics equations of working mechanism and solve the acceleration of the bucket to predict security of the mechanism 4. xiaobin ning analyzed the strength of the arm, lever and link by coupling hydraulic and mechanism 5. xuyang cao built up a rigid- flexible coupling model of working mechanism of wheel loader to match the real situation 6. wenyue dai carried out an orthogonal experiment to improve performances of the working device. they obtained a satisfactory result for automatic reset and translation feature in lifting 7. xiuhua gao optimized the performances of parallel moving and automatic reset 8. yingli zu optimized the bucket angle and the force of the tilt cylinder 9. the types of loaders in china are mainly 3t, 4t and 5t models. 5t loader is the most popular. even so, the performance of it is not so perfect. there is a zl50 wheel loader has following problems: 1, delivering ratio of working mechanism is too small. the hydraulic cylinder should provide much more force to shovel and dig the same materials. 2, the bucket swing is too much in the lifting process, the material is easy to be spilled out. 3, the bottom of the bucket can not be flat down automatically when it goes back to its original location after unloading. in the case, the operator has to do an additional operation to flat it down. the action would increase the complexity of the operation and waste energy. the research establishes a virtual model of the working mechanism in adams and optimizes the three mentioned performances to meet the requirements. figure 1. reverse six-bar linkage model in adams *the work is?supported by national natural science foundation of china under contract 10775128. 978-1-4244-7739-5/10/$26.00 2010 ieee ii. establish the parameterized model of six-bar linkage of loader the working device of wheel loader is a reverse six-bar linkage which mainly consists of six parts which are: a lift arm, a rocker arm, a connecting rod, a bucket, a tilt cylinder and a lift cylinder. fig. 1 shows the model in adams. in it, the tooths cusp of bucket is as the origin point and the shoveling condition is as the initial state. the parametric model based on structure point is added the restrict pairs and driven functions of hydraulic cylinders. the sliding pairs on hydraulic cylinders are parameterized to follow the changes of structure points in the optimum design process. figure 2. delivering ratio of the mechanism iii. optimization object selection desired improving performances of the mechanism consist of delivering ratio, translation feature in lifting and automatic reset of the bucket. the translation feature is the continuous angle variation range of bottom of the bucket in lifting process. the delivering ratio represents the capability of the power provided by the hydraulic cylinder. with the same force provided by the hydraulic cylinder, the larger the delivering ratio is, the greater the max. digging force is. max. digging force is one of the most important performances of the loader. we use the requirements of the translation feature in lifting and the automatic reset as constraints. but only use the ratio of delivering power as the target of optimization. the function of delivering ratio expression is as follows. )sin( )sin()sin( uclogxlcb ueuflbelfg f = (1) herein, lfg represents the distance between hinge point f and hinge point g on bucket (mm). lbe is the length of the lower rocker arm be (mm). lcb is the length of the upper rocker arm cb (mm). logx is the length of the bottom of bucket(x-component of og minus 100)(mm). uc is the angle between upper the rocker arm bc and the tilt cylinder cd: ? bcd (). uf is the angle between short tie rod fe and gf on bucket: ?gfe (). ue is the angle between short tie rod fe and lower rocker arm eb: ?feb (). fig. 2 shows the curve of the delivering ratio during the work cycle. the delivering ratio reaches its peak point during the lifting process. but in fact, the biggest resistance produces on the bucket is at the shoveling position of initial state. it means that the delivering ratio at the initial location should be the bigger the better. therefore, the delivering ratio at the initial location is selected to be the optimization object. table i. analysis of variables on performances of loader variables coordinate of points delivering ratio unloading distance unloading height unloading angle bucket angle at carrying position translation feature in lifting automatic reset dv_1 g_x -0.0003811 -3.188 -4.4868 0.22358 -0.08456 0.00061 -2.48e-02 dv_2 g_y -0.00080485 -21.865 -13.846 1.14330 0.13424 0.01209 -6.53e-02 dv_3 f_x 0.0001245 8.1727 5.7828 -0.47231 0.089826 -0.00102 2.57e-02 dv_4 f_y 0.0010468 8.9019 6.3019 -0.51464 -0.22226 -0.01721 7.18e-02 dv_5 e_x 2.50e-05 -11.886 -8.2374 0.68306 0.00068 -0.00033 9.48e-04 dv_6 e_y 0.00020986 11.538 8.1168 -0.66624 0.00647 -0.00261 2.93e-02 dv_7 b_x 3.48e-05 8.424 5.996 -0.48783 -0.00464 0.00144 0.011585 dv_8 b_y -0.00095452 -5.0802 -3.705 0.29642 0.17496 0.01486 -0.079622 dv_9 c_x -9.21e-05 -1.0879 -0.78391 0.06319 -0.00003 0.00143 -0.014148 dv_10 c_y 0.00052259 2.2758 1.6428 -0.13227 -0.10076 -0.0479 0.047653 dv_11 h_x - 1.289 -0.61031 -0.02198 0.00012 5.12e-06 1.18e-05 dv_12 h_y - -2.617 1.2421 0.04450 -0.00033 -1.3e-05 -3.38e-05 dv_13 zd_sd - -4.6982 -3.4236 0.27404 -0.29177 -0.16624 -0.21813 dv_14 zd_xz - -4.6982 -3.4236 0.27404 - - -0.21813 dv_15 db_js - 11.936 -5.7745 -0.19812 - 9.55e-05 -0.0005706 dv_16 db_sd - 11.936 -5.7745 -0.19812 -0.12009 0.00014 -0.0005706 dv_17 d_x 3.54e-06 4.5393 3.3059 -0.26471 -0.00434 0.10177 0.00050514 dv_18 d_y -2.01e-05 5.503 4.0283 -0.32153 0.04512 0.18314 -0.0027619 dv_19 a_x - -2.584 -3.767 0.21823 0.00752 -0.10378 0.00043155 dv_20 a_y - 12.723 -10.273 -0.00167 -0.05423 -0.14237 -0.0017216 dv_21 k_x - -4.2763 2.0374 0.07239 -0.00435 -1.4e-05 -0.0002383 dv_22 k_y - -13.51 6.6531 0.21921 0.01588 -0.00015 0.0006876 iv. constraints the measurement functions and running functions in adams are utilized to establish constraints of each operating conditions separately. the main constraints are set up to be the upper limit of translation feature in lifting, lower and upper limit of bucket angle at carrying position, drive angle, unloading distance, unloading height, unloading angle and automatic reset. the optimal solution obtained by the numerical optimization algorithm often falls on the border of the constraints without a good robustness. it is necessary to consider the errors arose in manufacturing and assembly process. that is, there should be necessary redundancy on the constraints. the performance requirements in table ii and table iii are constraints details. the mechanism must satisfy all these constraints. table ii. comparison of the initial model and the optimized model on the main performances main performance parameters translation feature in lifting automatic reset delivering ratio performance requirements 1050 1072 1150 1143 1092 1066 max. of gfe () 15-165 144.578 154.743 154.415 164.988 165.002 max. of gfe () 15-165 14.451 15.750 14.996 14.9927 15.001 max. of feb () 15-165 163.188 161.925 164.998 165.0292 164.996 figure 5. (a) angle feb curve before and after optimization, (b) angle bcd curve before and after optimization, (c) angle gfe curve before and after optimization table iv. coordinate of points of initial and optimum models points original bucket unchanged bucket and lift arm unchanged all parameters based on sensitivity x y x y x y x y x y g 1200 196 1200 196 1200 196 1175.07 184.512 1200 180.80 f 1217 584 1217 584 1217 584 1219.86 624.44 1226.25 627.28 e 1873 506 1884.45 556 1906.99 556 1896.5 499.65 1900.32 500.27 b 1552 1239 1515.97 1189 1552 1239 1534.35 1197.04 1529.58 1196.18 c 1503 1855 1453 1905 1550.58 1905 1500.44 1877.72 1503 1882.28 h 2212 1045 2212 1045 2212 1045 2212 1045 2212 1045 d 2950 2110 2943.61 1981.03 3030.51 1910 2895.75 2017.07 2950 1961.9 a 3339 2067 3332.12 2124.03 3339 2067 3361.76 2079.42 3339 2102.16 k 3468 1484 3468 1514.13 3469.96 1479.67 3468 1486.65 3468 1484 zd_sd zd_xz zd_sd zd_xz zd_sd zd_xz zd_sd zd_xz zd_sd zd_xz tilt -189.73 317.33 -269.013 315.82 -239.556 279.54 -279.517 328.961 -296.138 317.33 db_js db_sd db_js db_sd db_js db_sd db_js db_sd db_js db_sd lift -639 -80 -679.327 -85.1666 -639.591 -81.0413 -642.291 -82.5185 -639 -125.173 viii. conclusion the results show that the delivering ratio, translation feature in lifting and automatic reset can be improved simultaneously to meet the requirements of the various constraints. from these four optimum results, considering the delivering ratio through the whole working process, it shows the “all parameters” and “based on sensitivity” are better relatively. the scheme “based on sensitivity” uses fewer variables which is the best one of the four schemes. it is necessary to emphasis on the fact that the three end points of the rocker arm and the joint point of the tilt cylinder on the frame (the position of point b, c, d and e) play an important role in optimizing the performance of the structure. they affect the delivering ratio seriously. particularly, simulation shows that the corresponding curve of delivering ratio can not be satisfied if point d unchanged. the ideal optimized result should be of high robustness, which should not be sensitive to the disturbance, like manufacturing errors, assembly errors and temperature shifting. so the constraints need to be given some margin. acknowledgment we thank mr. xiaohong xu for his industrial promoting this study. we also like to give our appreciation to mr. hongbin zang for his contribution to this work. references 1 reno filla, jan-ove palmberg, “using dynamic simulation in the development of construction machinery”. the eighth scandinavian international conference on fluid power, tampere, finland, vol. 1, pp. 651-667, may 7-9, 2003. 2 rongyi zhang, jianjia qi, yu cai, “intelligent optimum design of the working mechanism of loader,” proceedings of the 7th world congress on intelligent control and automation (wcic