Strength Analysis and Optimization Design about the key parts of the Robot

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1 Intenational Jounal of Reseach in Engineeing and Science (IJRES) ISSN (Online): , ISSN (Pint): Volume 3 Issue 3 ǁ Mach 2015 ǁ PP Stength Analysis and Optimization Design about the key pats of the Robot NIU Dong-Ke 1 JIN Xiao-Yi 1, LU Qiu-Hong 2 1. Shanghai Univesity of Engineeing Science,Shanghai HRSTEK Co., Ltd.Shanghai,Shanghai ABSTRACT: Study on stuctue optimization design about Flip Ams of Mobile Robot. Fist conducted peliminay stuctual design, and established finite element analysis model by HYPERMESH, use ANSYS softwae to study Flip Ams Stess distibution and stuctue optimization. Stength check to ensue the stength and stiffness of Flip Ams meet safety equiements, and make sue the eliability of the design, to povide a theoetical basis fo the stuctual optimization design of Flip Ams. Optimization design consideing the weighted compliance as the object function, the fame was impoved by modifying the paametes which ae most sensitive to the chaacte of the fame stuctue. The esults showed that stuctual optimization design without affecting the eliability of Flip Ams, educing the quality of the pats impoved and the Flip Ams flexible mobility, to povide a theoetical basis fo the stuctual design of obot. Key wods-mobile obot, Flip Ams, HYPERMESH, ANSYS, Stength Analysis, Optimization Design I. INTRODUCTION Wheel-Tack obot has both the advantage of wheeled obot and tacked obot, which as an impotant object of study by institute and colleges and univesities. With the apid development of intelligent, some extent, wheel-tack obot has been widely applied in the investigation, inspection, alet, fie-fighting and othe dangeous and hash envionments. Accoding to many complicated wok envionment, must equie the obot woking stable enough, so the obot stuctue design should have highe equiements. In ode to meet the pefomance equiements of the obot enough, all pats obot design is vey impotant. Take the flip ams of the wheel-tack obot as the eseach object, using PROE fo thee-dimensional modeling, and meshing use the Hypemesh establishment of finite element model, then put the finite element model into ANSYS fo stength analysis. Finally, the optimized design and obtains a set of effective method which can make sue the pat stength, povide an effective theoetical basis fo the stuctue optimization of obot. II. THE BASIC THEORY OF STRUCTURAL OPTIMIZATION Optimal design function contains design vaiables, objective function and constaint conditions. Optimization mathematical model defined as: f ( X ) min f ( x1, x2,, x n ) (1) whee g( X ) 0 j 1,, m h ( X ) 0 k 1,, m k L U X X X i 1,, n i i i whee X is design vaiables, f( X) is objective function, g( X ) ( ) The finite element equation of the pats of the stuctue is given as: [ K]{ S} { F} h hx ae constaint conditions whee,[ K ] is Stiffness matix;{ S } is Element node displacement vecto;{ F} is Element node load Using the companion vaiable method to design sensitivity and the deivation of X,and the patial deivative of S defined as: (2) 25 Page

2 Stength Analysis and Optimization Design about the key pats of the Robot [ S] 1 { F} [ K] [ K] { S} (3) X X X Concomitant vaiable E is intoduced when topology optimization. whee [ K]{ E} { Q} (4) Theefoe, the esponse sensitivity of the pats is given as: T g Q T { F} [ K] { S} { E} { S} (5) X X X X III. THE STRENGTH ANALYSIS 3.1 Desciption The flip ams of Wheel-Tack obot used to connect diving wheel and deflection olle is shown in figue1.it is the key components ensue deflection olle movement accuate and flexible[1-2].in ode to ensue its accuacy and eliability duing execise, we need to know the amount of defomation and the imum stess when it s woking, and compaed with the mateial chaacteistics, we can get the safety facto. Then using the finite element analysis softwae to get the simulation model and calculated[3]. Figue1: Pats location diagam 3.2 Model simplification Diffeent analysis puposes need diffeent equiements fo CAD model. To build the finite element models, If only pay attention to the oveall stuctue, it can be to emove fine chaacteistic stuctue. Fo example, to analyze the whole stuctue mode, can emove small fillet, adius and bolt etc Thee ae many small theaded holes and adius in the flip ams, this theaded holes and adius will affect geneating the high quality gid and affect the accuacy of finite element calculation. And these theaded holes and adius on the whole model has little impact, consideing the foce of flip ams and the accuacy of the flip ams model calculation esults, small theaded holes and adius emoved[4]. The position of these theaded holes and adius which should be emoved is shown in Figue 2. Compaing with the oiginal model and the simplified model is shown in Figue 3 Figue2: Eliminates scew Figue3: Rotating Ams Figue4: The finite holes and adius befoe and afte simplify element mesh model 3.3 Finite element analysis Mateial paametes: This pat use the Type 45 steel,mateial chaacteistics as shown in Table 1 Table 1.Mateial popeties Elastic Poisson's Yield Shea Mateial Modulus atio limit Stength (EX) (PRXY) ) ) Type 45 steel ( s ( 2.1E5MPa MPa 178MPa 26 Page

3 Stength Analysis and Optimization Design about the key pats of the Robot The simplify model will be impoted into the HYPERMESH, and the finite element mesh model is established[5]. Consideing the minimum geomety of the model and the gid numbe, the aveage mesh size is set to 2mm, choice of 8-node hexahedal elements SOLID185, got 7887 nodes and units. The finite element mesh model is shown in Figue 4.Accoding to the known constaints and load conditions, to add constaint and load imposed on the coesponding position of the finite element mesh model. Figue5: Condition 1 Figue6: Condition 2 Condition 1 (Figue5): Obstacle cossing and flip am 35- degees angle with the gound. The citical point: The moto is connected with the flip am though the gea shaft, output toque Tc; The small end of the flip am degees angle with the step, in a citical condition. Whee the end of flip am exets a downwad foce and the font diving wheel is lifted, the font diving effect on the gound without the foce. The bounday conditions can be divided into thee pats: 1) Six bolt holes. The stess can be decomposed into downwad adial foce and tangential foce. Radial foce: F ( G/ 4) / 6 sin Tangential foce: F ( G/ 4) / 6 cos 2) The clockwise diection toque of the diving wheel: Tc T * i* n / 2 3) Fixed constaint: Accoding to the position of flip am in the assembly and condition 1, and applying a full constaint except axial otation to the theaded hole of deflection olle, applying axial constaint in the position of between diving wheel and flip am, applying axial otation constaint in the position of between deflection olle and flip am. Whee: G=2500N. 35 o. T 1160Nmm i 250 n 0.73 F. F 59.75N Tc Nmm Calculated: 85.33N Condition 2 (Figue6): Since popped state Desciption: Refes to flip am popped itself unde the action of the dive moto, the angle between flip am and hoizontal diection of. The bounday conditions can be divided into fou pats applied: 1) The clockwise diection toque of the diving wheel: Tc T * i* n / 2 The geat cicle wall and cente auxiliay nodes components of a flexible connection RBE3, and the toque applied in RBE3. 2) Six bolt holes. The stess can be decomposed into downwad adial foce and tangential foce. Radial foce: F ( G/ 4) / 6 sin Tangential foce: F ( G/ 4) / 6 cos 4) Bolt holes on the deflection olle. The stess can be decomposed into upwad adial foce and tangential foce. Radial foce: F ' ( G/ 4) / 2 sin Tangential foce: F' ( G/ 4) / 2 cos 5) Fixed constaint: Applying a full constaint to the theaded hole of deflection olle, applying axial constaint in the position of between diving wheel and flip am, apply axial otation constaint in the position of between deflection olle and flip am. Whee: 8 o, Othe paametes constant 27 Page

4 Stength Analysis and Optimization Design about the key pats of the Robot Calculated: Tc Nmm, F 14.50N, F N, F ' 43.49N, F ' N. 3.4 The esults of finite element analysis The finite element model was established and solved accoding to the known conditions fo each kind of condition[6]. Calculation esults ae as follows: The defomation image and stess image of finite element model of condition1 is shown in Figue 7. Obviously, the imum defomation of the components fo the mm and distibution in the model of the lage end, the imum stess is MPa and distibution in the connecting scew hole nea the guide wheel, the imum shea stess is MPa and distibution in the bolt hole of the guide wheel. Figue7: Results image of Condition 1 Figue8: Results image of Condition 2 The defomation image and stess image of finite element model of condition2 is shown in Figue 8. Obviously, the imum defomation of the components fo the mm and distibution in the model of the lage end, the imum stess is MPa and distibution in the connecting scew hole nea the guide wheel, the imum shea stess is MPa and distibution in the bolt hole of the guide wheel. ANSYS analysis esults ae summaized as follows: imum stess is shown in table 2, the imum shea stess is shown in table 3. Whee: =355MPa, =178MPa, s / s, n ' ' / n Table 2.The imum stess Maximum Compaed stess (MPa) with s Safety facto(n) Condition Condition Table 3.The imum shea stess imum shea Compaed stess ' (MPa) with Safety facto(n ) Condition Condition ``5.4 In conclusion: In two conditions, the flip am of imum stess and imum shea stess ae fa less than the mateial yield limit and mateial shea modulus, safety facto is big enough[7-8]. Theefoe, the flip am is safe and stable wok in the two conditions, meet the design equiements. IV. STRUCTURE OPTIMIZATION DESIGN Accoding to the basic theoy of stuctual optimization design to define the design vaiables, objective function and constaint conditions, in ode to ensue the link stength, the middle aea of flip am as optimize 28 Page

5 Stength Analysis and Optimization Design about the key pats of the Robot aea, the elative density of the design aea as the design vaiables.objective function is the countdown fo stuctual stiffness, when the load is given, stiffness values become lage and the objective function value will be smalle and vice vesa[9]. Accoding to the two conditions fo topology optimization, the volume faction afte many iteative calculations esults of convegence. Afte optimize it can be seen a easonable distibution of the mateial and the load tansfe path, evident pat stuctue is simplified to educe the numbe of quality is shown in Figue 9 and Figue 10. Figue9: The optimization esults image Figue10: Flip Am model afte optimization V. IN CONCLUSION Fistly, though stength analysis of flip am in diffeent conditions, the designed stuctue and mateials of flip am can meet the accuacy, eliability in wok demand, stain and stess in the eliable ange. In geneal, flip am by moe vigoous ole in theaded hole that on the guide wheel, but less than the allowable stess, othe pats of the stess is smalle. Theefoe, the flip am stength, stiffness can meet the safety equiements, though the joint simulation of HYPERMESH and ANSYS, which povides an impotant basis fo the optimization of the stuctue of pats[10]. Based on eliability the model fo the topological optimization and the optimum design of pats, by optimizing the flip am stuctue is simplify, educe the quality of many and achieve the optimization goal, to povide theoetical basis and technical suppot fo the oveall stuctue design of the obot. REFERENCES [1] A.Gag,B.Qwen,D.Belle,etal. A Biomechanical and Egonomic Evaluation of Patient Tansfeing Task: Bed to Wheelchai and Wheelchai to Bed. Egonomics, 1991, 3(34):289~312. [2] Kebshi,Palazzolo JJ. Rehabilitation obotics: pefomance-based pogessive obot-assisted theapy. Autonomous Robots, 2003,(15):7~20. [3] Rithalla S V, Gonsal K M. Assessment of altenating aim mattesses using a time based inteface pessue times hold technique [J]:1998,35(2): [4] Goemka P K,Booke J F.Spheical Beaing :Static and Dynamic Analysis Via the Finite Element method [J].Jounalof Lubication Technology, Tansactions of the ASME,1980,102(3): [5] Li Rui.Study on the Attitude Detection and Contol System of Mobile Robot with Muti-tacked based on Paallel Mechanisms[D]. the maste's degee thesis of Dong Hua Univesity.2008 [6] CHEN Min,MAO Li-min. Reseach on the Obstacle Negotiating Pefomance of Position Changing-Fou Tacked Feet-Robot Mobile Mechanism[P]. Jounal of Dong Hua Univesity. Vol. 31,No. 3 Jun [7] Chen C X, Tivedi M M. Reactive locomotion contol of aticulated-tacked mobile obots fo obstacle negotiation[c]//ieee/rsj Intenational Confeence on Intelligent Robots and Systems. Piscataway, NJ, USA: IEEE, 1993: [8] Zheng, J.M.,Chan, K.W.,Gibson, S., Vitual eality, Potential, IEEE, 1998, 17(2):20 ~23 [9] Tune M.L.,Findley, et al. Development and Testing of a Telemanipulation System with Am and Hand Motion [C], ASME IMECE Symposium on Haptic Intefaces,2000. [10] Yang Tingli,LIU Anxin,LUO Yufeng. Theoy and Application of Robot Mechanism Topology [M],Beijing:Science Pess, 2012(5) Page