管道相贯线自动切割机器人支撑定位系统设计含proe三维及17张CAD图
收藏
资源目录
压缩包内文档预览：(预览前20页/共23页)
编号：81009534
类型：共享资源
大小：16.49MB
格式：ZIP
上传时间：2020-05-24
上传人：QQ14****9609
认证信息
个人认证
郭**（实名认证）
陕西
IP属地：陕西
50
积分
- 关 键 词：
-
管道
相贯线
自动
切割
机器人
支撑
定位
系统
设计
proe
三维
17
CAD
- 资源描述：
-
管道相贯线自动切割机器人支撑定位系统设计含proe三维及17张CAD图,管道,相贯线,自动,切割,机器人,支撑,定位,系统,设计,proe,三维,17,CAD
- 内容简介：
-
Available online at Mechanism and Machine Theory 43 (2008) 984995Mechanism andMachine Theory/locate/mechmtA type synthesis method for hybrid robot structuresAlexandre Campos *, Christoph Budde, Ju rgen HesselbachInstitute of Machine Tools and Production Technology, Technical University of Braunschweig, Langer Kamp 19 B, D-38106 Braunschweig, GermanyReceived 11 May 2006; received in revised form 30 April 2007; accepted 11 July 2007Available online 24 October 2007AbstractIn this paper a new methodology to synthesize hybrid robots as a whole structure is presented. The method is based on Assur groups as the simplest basic blocks to build kinematic chains. Criterions like symmetry and low inertia are consid- ered in the design process. The method results in hybrid robots whose structures are as simple as possible. The closed chains of some of them are known parallel structures, however one of them is a new hybrid structure. 2007 Published by Elsevier Ltd.Keywords: Hybrid robot; Synthesis method; Assur groups1. IntroductionHybrid structures combine the advantages of parallel and serial chains, e.g. stiffness and manipulability 16. Most robots designed are either built up of serial or in-parallel connected kinematic chains. Serial robotsconsist of a series of active joints connecting the base to the end effector and feature large workspaces and highdexterity but they suffer from lack of stiffness and from relatively large positioning errors due to their canti-lever type of kinematic arrangement. On the other hand, parallel manipulators consist of a set of parallel legseach with active and passive joints required to maintain the system mobility and controllability. They connectthe base to the moving platform resulting in structures able to achieve high stiffness and high force-to-weightratio. However, parallel manipulators are known for a restricted workspace and low dexterity.Aiming to merge the advantages of serial and parallel robots, the basic principle of hybrid kinematic structures is to divide the task of manipulation 1. This task is divided into a position task (position mechanism)and an orientation task (orientation mechanism), respectively. The position mechanism controls the positionwhereas the orientation mechanism manipulates the orientation of the end effector. Then, these mechanismsmay be connected in series, called conventional hybrid structure, or in parallel, i.e. cooperative structure 1,8.Additionally, the serial combinations of serial and parallel structures can be sub-divided into 3: parallelparallel type 6, parallelserial type 7 and serialserial type, i.e. a conventional serial manipulator. In this* Corresponding author.E-mail addresses: a.camposiwf.ing.tu-bs.de (A. Campos), ch.buddetu-bs.de (C. Budde).0094-114X/$ - see front matter 2007 Published by Elsevier Ltd. doi:10.1016/j.mechmachtheory.2007.07.006A. Campos et al. / Mechanism and Machine Theory 43 (2008) 984995985work, we focus on the conventional hybrid structure of parallelserial type, named hybrid structure for short. Therefore, by using hybrid structures it is intended to retain the merits of serial structures, i.e. large workspace and high dexterity, and parallel structures, i.e. high stiffness and high force-to-weight ratio, while their disad- vantages are minimized.Analysis and modeling have been the main research field in hybrid robots 1,3,912, additionally some researches have dealt with the design of hybrid robots 46. In spite of the cited advantages of hybrid robots, there is no systematic method to design or synthesize hybrid robots as a whole structure instead of a separated synthesis for the parallel and the serial structure.This paper proposes a synthesis method for hybrid robots as a whole, built up of sets of Assur groups. It is based on a method for finger synthesis which guarantees the simplest structures, i.e. the least number of bodies and one degree of freedom (dof) joints 13, however the presented method does not use computer algorithms which may result in chain isomorphisms.Section 2 presents a brief introduction to Assur groups, then the hybrid kinematic design and some require-ments for a suitable hybrid robot are introduced. To illustrate the method, all simplest possible chains for sixdegrees of freedom (DOF) of the end effector with 3, 4 and 5 fixed drives are presented. Based on the method asymmetrical hybrid robot is found whose closed structure topology is new according to the knowledge of theauthors. Finally, the joints are allocated into the hybrid chain and for the new robot an embodiment is pro-posed based on legs for fully isotropic translational parallel robots 14.2. Assur groupsOne of the main approaches employed in the literature for carrying out the structural synthesis of kinematic chains is to build up desired chains by addition of links to simpler chains with fewer links 15. Assur (1952) introduced kinematic chains named Assur groups, that are open subsets of links, which can be added to a kine- matic chain without affecting the mobility of the chain 16,17. Additionally, when the group is connected to a link through all of its free joints, shown as black joints in Fig. 1, it becomes a structure with zero degrees of freedom.Assur proposes that complex chains may be formed from the addition of Assur groups to chains with fewer links because this addition does not alter the degree of freedom of the chain. Manolescu uses the Assur groups to build kinematic chains with 8-, 9- and 10-links 1719. Tischler et al. implement a systematic method to generate Assur groups from minimal kinematic chains for several screw systems and apply it to the structural synthesis of multi-tipped fingers of a robotic hand 20. Jinkui et al. apply Assur groups to investigate chains with multiple joints 21. Yannou et al. use Assur groups as modular components for the design of platforms for planar mechanisms 22.Regarding that an Assur group may be built up by sequential addition of Assur groups, Tischler 13 intro- duced the concept of Minimal Assur groups, i.e. Assur groups which contain no Assur groups as subsets. Min- imal Assur groups provide a considerably improved basis of building-blocks, that have the least number of links and one dof joints, for the structural synthesis and selection of mechanisms.Aiming at hybrid robot design, we employ building-blocks derived from Assur groups. Let B be the degrees of freedom of the space in which a mechanism is intended to function, then Assur groups may be obtainedFig. 1. Some basic Assur groups.986A. Campos et al. / Mechanism and Machine Theory 43 (2008) 9849951Fig. 2. Null mobility kinematic chains.eliminating a link of a B-system kinematic chain with null mobility M = 0. For instance, the Assur groups inFig. 1 may be obtained from the kinematic chains of Fig. 2 through this link elimination.These suitable null mobility chains may be designed applying the general mobility Gru blerKutzbach criterion to a subset of n links and j single-freedom joints 2325M Bn j l j;M BL j; where L =n + j + 1 is the number of independent loops in the chain. However, to comprise over constrained kinematic chains, i.e. chains where the same constrain is imposed more than once on a link (e.g. on the end effector), we may use a modified Gru blerKutzbach criterion 26 which includes the number of over con- straints qM BL j q: 2Generally speaking, over constrained mechanisms are potentially simpler and stiffer than statically deter- mined ones (they comprise fewer joints and distribute non-working loads to a great extent), even though they require higher construction accuracy and stricter tolerances in order to operate properly 27.Using Eq. (2) for different numbers of loops (L 0), over constraints (q 0) and null mobility (M = 0) chains we obtain various couples (n, j) of links and joints that could form suitable kinematic chains in the screw system B, aiming at the generation of Assur groups. For instance, let L = 3, q = 0, M = 0 and B = 6, therefore the suitable kinematic chain must contain j = 18 single-freedom joints and n = 16 links.Different options to arrange a given couple (n, j) may be found through the partition 28 of the integer 2j into n parts, regarding that there is no link with just one joint. So, e.g. the partition of 2j = 36 joint halves (each joint is counted twice because the same joint appears in two links simultaneously) on n = 16 links is shown in Table 1 where 2n is a binary link, 3n is a ternary link and so on.In spite of all the options of Table 1 fulfilling the mobility criterion some of them are unsuitable to generate proper Assur groups for the generation of hybrid robots. Requirements for suitable kinematic chains for hybrid robots are introduced in Section 4. In the next section, based on the characteristics of Assur Groups, a synthesis method for hybrid kinematic chains is presented.Table 1Partition of 2j = 36 joints halves into n = 16 linksLink type2n3n4n5n6nOption 1124Option 21321Option 3142Option 41411Option 5151A. Campos et al. / Mechanism and Machine Theory 43 (2008) 9849959873. Hybrid kinematic chain designThe presented method for hybrid kinematic chain design is based on the synthesis method introduced by Tischler 20 where Assur groups are used as fingers. Considering the characteristics of Assur groups, it is pos- sible to construct the simplest hybrid kinematic chains introducing Assur groups between the base and the end effector. Given that Assur groups may be formed by the elimination of a link in a suitable kinematic chain, simpler hybrid kinematic chains may be built by cutting a convenient link of a null mobility kinematic chain. So, one part of this link is considered the base and the other one is considered the end effector. Therefore, using this procedure the mobility of the hybrid chain is M = Bq.For instance, consider a minimal kinematic chain with M = 0, L = 2, q = 0 and B = 3. Then the minimal kinematic chain must contain j = 6 single-freedom joints and n = 5 links. So, from the partition results that a possible chain consists of two ternary and three binary links. Fig. 3 presents two possible chains that result in two hybrid chains through the cutting of a suitable link.4. Hybrid robot designIn order to design hybrid robots that maintain the advantages of parallel structures, mentioned in Section 1, some considerations on hybrid kinematic chains must be observed. Sometimes, establishing these consider- ations is a step which depends more on intuition and imagination rather than on the ability to analyze. There- fore, different considerations could well arrive at a different final result.Let the hybrid robot mobility be M = Mf + Mm, where Mf and Mm are the number of fixed (to the base) and mobile drives, respectively. High stiffness and high force-to-weight ratio benefits of parallel structures are directly related to the drive positions. Best results are obtained when all the drives are fixed to the base, how- ever others low inertia arrangements as motors tilting with respect to the ground or attached at ball-screw tele- scopic legs are considered in this paper as fixed drives as well. Therefore, a suitable hybrid chain must contain at least a link with (Mf + 1) joints, to be the base, which will be cut according to the procedure introduced inFig. 3. Procedure to obtain hybrid structures with M = 3 from suitable kinematic chains with M = 0, L = 2, q = 0 and B = 3.988A. Campos et al. / Mechanism and Machine Theory 43 (2008) 984995Fig. 4. Fractionated chains: (a) two closed sub-chains and (b) one open and one closed sub-chain.Section 3. Considering this base cut, that opens a loop, the number of loops in the M = 0 suitable chain (before the cutting) must be L = Mf. Through this cut the serial structure is created, so Mm consecutive joints must exist, which are driven by the mobile drives, between the cut and a non-binary link (the mobile base of the serial chain).Additionally, to set the fixed drives in a unique link, i.e. the base, the hybrid chain must not be a fraction- ated chain. A fractionated chain contains a link which divides the chain into two independent kinematic chains. These independent chains may be closed, i.e. every link is connected to at least two other links, or open as shown in Fig. 4.Regarding the manipulation task division remarked in Section 1, the position (translational DOFs) and the orientation (rotational DOFs) tasks are assigned to the parallel and to the serial structure of the hybrid chain, respectively. In general, for spatial tasks, this consideration drives us to place at least three fixed drives in the base Mf = 3. Another consideration that is important for hybrid robots is the symmetry which results in design advantages and simplicity of the velocity and acceleration calculations.At last, aiming at a general joint position in the space, the screw system for the hybrid robots is fixed to beB = 6. In the next section we apply the method to get hybrid structures as a whole.5. Hybrid structures with 3, 4 and 5 fixed drivesIn order to illustrate the presented method, we implement it to obtain possibilities for a hybrid structure in the general space, i.e. M = B = 6. Aiming at advantages of parallel and serial structures we have at least Mf = 3 (to have at least three motors in the base), therefore the number of loops of the M = 0 suitable chain should be L = 3, 4 or 5. Hence, Eq. (2) results in several potential chains, with different numbers of links n and joints j. Each couple (n, j) may be arranged with different kind of links (binary, ternary, etc.), according to the partition. These options are detailed in Table 2 for q = 0, L = 3, 4 and 5.It is noted, through Eq. (2) and the partition, that if the value of q increases by one (one over constrained degree), the quantity of binary links decreases by one, and so on. For instance, the option q = 0, L = 3, 18 joints, 16 links (2n = 12 and 3n = 4) becomes q = 1, L = 3, 17 joints, 15 links (2n = 11 and 3n = 4).Considering the cut procedure and that at least Mf driven joints are required in the base at least one link with L + 1 (= 4, 5 or 6, respectively) or more joints to be the base is necessary. The options that do not fulfill this condition are unsuitable. Besides, those options in Table 2 that contain serial chains (sequence of binary links) between two joints of the same link are fractionated chains and unsuitable for hybrid robot design too, as shown in Fig. 5. A technique to avoid fractionated chains consists in jointing non-binary links (links with n 2 joints) to the base through at least one but less than n serial chains.Applying the above criterions, only some chains (marked with gray columns in Table 2) are suitable to result in hybrid robots using the presented method. These chains are presented in a general form in Figs.68 for L = 3, 4 and 5, respectively, where the number of binary links 2n depends on the number of over con- straints q P 0.A. Campos et al. / Mechanism and Machine Theory 43 (2008) 984995989Table 2Different options of couples (links, joints) (n, j) for chains with M = 0, L = 3, 4 and 5, q = 0 and B = 6, arranged for different kinds of linksSuitable chains to generate hybrid robots are marked with gray columns.Fig. 5. Chains that present serial chains between two joints of the same link are fractionated.Fig. 6. Suitable chains with L = 3 to generate hybrid robots (through cuts in base): (a) 2n 6 13, 3n = 2 and 4n = 1; (b) 2n 6 14 and 4n = 2.990A. Campos et al. / Mechanism and Machine Theory 43 (2008) 984995Fig. 7. Suitable chains with L = 4 to generate hybrid robots (through cuts in base): (a) 2n 6 17, 3n = 3 and 5n = 1; (b) 2n 6 18, 3n = 1, and4n = 1 and 5n = 1; (c) 2n 6 19 and 5n = 2.Fig. 8. Suitable chains with L = 5 to generate hybrid robots (through cuts in base): (a) 2n 6 21, 3n = 4 and 6n = 1; (b) 2n 6 22, 3n = 2,4n = 1 and 6n = 1; (c) 2n 6 23, 4n = 2 and 6n = 1; (d) 2n 6 23, 3n = 1, 5n = 1 and 6n = 1; (e) 2n 6 24 and 6n = 2.The next step is to cut the base in such a way that a hybrid chain is obtained. It is important to notice that some cuts may produce the same hybrid chain, i.e. isomorphisms. For instance four different cuts in the base of the suitable chain in Fig. 6a result in the same hybrid chain as shown in Fig. 9. However, isomorphisms in this method may be detected through simple inspection due to the limited number (4, 5 or 6) of possible cuttings. Comparing only L + 1 = 4, 5 or 6 possible hybrid chains (one for each possible cut) it is possible to visually identify the existence of isomorphisms and reject them. Possible cuts which result in non-isomorphic hybrid chains are represented by a semicircle in Figs. 68.Fig. 9. Four possible different cuts produce the same hybrid chain: isomorphism.A. Campos et al. / Mechanism and Machine Theory 43 (2008) 984995991Figs. 1012 show the hybrid kinematic chains obtained through the presented method, with 3, 4 and 5 fixed drives in the base, respectively. These chains may be divided in symmetrical and non-symmetrical chains.In this paper we are interested in symmetrical chains due to the advantages cited above. From Figs. 1012 we may observe that hybrid chains: a and b in Fig. 10, a.l, b.2 and c in Fig. 11 and b.1.1, d.l and e in Fig. 12 are symmetrical structures.It is important to notice that sometimes the symmetry is not obvious with only a glance and some effort is necessary to detect the symmetrical axis of the structure. For instance, the structures a in Fig. 10 and b.2 in Fig. 11 are rearranged in Fig. 13 to demonstrate their symmetry.Considering these symmetrical hybrid chains, three of them are typical hybrid robots, known parallel manipulators with a serial chain attached to their mobile platforms: Figs. 10b, 11c, and 12e. For instance see Fig. 14, where a serial chain with three rotative joints (for the orientation) is attached to the mobile plat- form of the fully parallel structure 14. The completed structure may be designed from a null mobility chain with L = 3, q = 0, 2n = 14 and 4n = 2 (see Table 2 and Fig. 6). Additionally, the closed part of the hybrid chains a in Fig. 10, b.2 in Fig. 11 and d.l in Fig. 12 are observed in fully isotropic parallel mechanisms for Schoenies motion, i.e. a shaft (constant-speed-ratio coupling) is hinged to the mobile platform of a fully iso- tropic translational parallel manipulator 27. To illustrate it, see the structure in Fig. 15 which corresponds to the closed part of a hybrid chain designed from a null mobility chain with L = 4, q = 3, 5n = 1, 4n = 1, 3n =1 and 2n = 15 (Table 2 considering q = 3). Thus, it becomes a six DOF hybrid robot through adding two serial joints to the end effector. Furthermore, the closed part of hybrid chain a.1 in Fig. 11 corresponds toFig. 10. Hybrid chains with three fixed drives in the base.Fig. 11. Hybrid chains with four fixed drives in the base.992A. Campos et al. / Mechanism and Machine Theory 43 (2008) 984995Fig. 12. Hybrid chains with five fixed drives in the base.Fig. 13. Rearranged chains of Fig. 10a and Fig. 11b.2.Fig. 14. Hybrid robot based on a serial chain attached to a fully parallel structure corresponding to the hybrid chain of Fig. 11c.A. Campos et al. / Mechanism and Machine Theory 43 (2008) 984995993Fig. 15. Fully isotropic four-degrees-of-freedom parallel mechanism 27 corresponding to the closed part of the hybrid chain ofFig. 11b.2.the topology of the H4 parallel robot 29. However, hybrid robot b.1.1 in Fig. 12 is a new simple symmetrical structure according to the authors knowledge.In order to complete the synthesis process and obtain the hybrid robot, in the next section we distribute the joints along all the sequences of binary links and substitute them by rotative or prismatic joints.6. Joint distribution and robot embodimentThe next synthesis step is to distribute the joints among the different serial kinematic chains between non- binary links. Initially, we assign Mm joints between the end effector and the next non-binary link which defines the serial chain of the hybrid robot. The distribution of the rest of the joints in the parallel chain may be accomplished regarding some patterns concerning symmetry, number of degrees of freedom and the type of movement. Considering that all the serial chains must exist but be non-redundant, the minimum and maxi- mum number of joints per serial chain is 1 and 6, respectively. For instance, if a hybrid robot of the type of Fig. 11a.1 without over constraints q = 0 is desired, we may distribute 24 joints at all (Table 2, L = 4). In this case, we have Mf = 4 drives fixed to the ground and Mm = 2 mobile drives corresponding to the serial chain. Therefore, 22 = 242 joints must be symmetrically distrib- uted in the six serial chains of the 3-loops closed kinematic chain. Aiming at symmetry, for instance, the serial chains are named A and B in Fig. 16a. It is important to notice that other possible symmetrical structures mayFig. 16. Symmetrical distribution of joints the hybrid chain of the Fig. 12b.1.1 whose closed part corresponds to H4 parallel robot 29.994A. Campos et al. / Mechanism and Machine Theory 43 (2008) 984995Fig. 17. Distribution of joints in new hybrid robot corresponding to the hybrid chain of Fig. 12b.1.1.be obtained. In this case only two symmetrical options are possible to distribute the 22 joints: A = 5 and B = 1 or A = 4 and B = 3.The last phase of the synthesis process presented in this paper is to substitute the serial chains of the hybrid robot by suitable physical links and joints according to the type of movement required for the end effector. In the literature various leg alternatives for parallel manipulators 14,26,27,30 exist which may be used to sub- stitute serial chains of the selected hybrid structure. For this substitution, in particular for translational move- ments, we use the elementary or complex legs, used in the structural synthesis of fully isotropic translational parallel robots 14.Considering the joint distribution for the structure given in Fig. 16a, we may obtain several options. One of them is shown in Fig. 16b, in such a way that the closed chain allows three translational and one rotational (around vertical axis) DOFs and the serial chain allows two more rotational DOFs. A new hybrid robot may be obtained based on the new hybrid chain of Fig. 12b.1.1. In this case, if a hybrid robot without over constraints (q = 0) is desired, we may distribute 30 joints in total (Table 2, L = 5). Con- sidering that, there are Mf = 5 drives fixed to the ground and Mm = 1 mobile drive in the serial chain. There- fore, 29 = 301 joints must be symmetrically distributed among the seven serial chains of the closed kinematic chain consisting of 4-loops. Aiming at symmetry, the joints may be distributed in two different ways: A = 5, B = 2, C = 5 or A = A, B = 4, C = 5 (see Fig. 17a). An alternative for the embodiment for this robot using elementary legs 14 is shown in Fig. 17b where the two ternary links possess the three translational DOFs (X, Y, Z) and one rotational DOF, around X and Y respectively. The quaternary link possesses the three translational DOFs and two rotational DOFs around X and Y. A unique rotative joint (around the Z axis) forms the serial chain, therefore the end effector has the six DOF in the general space.7. ConclusionsA new method to synthesize simple hybrid robots based on Assur groups is introduced. Through the method a bank of simple symmetrical hybrid structures for 3, 4 and 5 fixed drives is developed. It is important to notice that this bank is additionally useful for closed structures if the serial chain attached to the end effec- tor is removed. In this method low inertia (as many fixed drives as possible) and symmetry are regarded in order to chose more suitable hybrid robots. Some of the obtained results are well known parallel robots (e.g. fully parallel robots, mechanisms for Schoenies motion and the H4 robot) with a serial chain attached to the end effector. Furthermore, one new symmetrical topology for hybrid kinematic chains is found. Exemp- larity, a kinematic chain embodiment is performed resulting in a new hybrid robot.AcknowledgementThis work was funded by the Stiftung Braunschweigischer Kulturbesitz and the German Research Foun- dation (DFG) within the framework of the Collaborative Research Center SFB562.A. Campos et al. / Mechanism and Machine Theory 43 (2008) 984995995References1 L. Tsai, S. Joshi, Kinematic analysis of 3-dof position mechanisms for use in hybrid kinematic machines, Transactions on ASME, Journal of Mechanical Design 124 (2002) 245253.2 G. Thornton, The gee tetrabot a new serialparallel assembly robot, in: Proceedings of the ICRAI988.3 S. Lee, S. Kim, Ecient inverse kinematics for serial connections of serial and parallel manipulators, in: Proceedings RSJ/ICIRS,IEEE, Yokohama, 1993, pp. 16351641.4 G. Yang, W. Chen, E. Hui, L. Ho, Design and kinematic analysis of a modular hybrid parallelserial manipulator, in: Proceedings ofthe ICARCV02.5 D. Chablat, P. Wenger, J. Angeles, Kinematic design of a 3-dof hybrid manipulator, in: Proceedings of the 2nd InternationalConference On Integrated Design and Manufacturing in Mechanical Engineering, Compiegne, France, 1998.6 L. Romdhane, Design and analysis of a hybrid serialparallel manipulator, Mechanism and Machine Theory 34 (7) (1999) 10371055.7 B. Siciliano, The tricept robot: inverse kinematics, manipulability analysis and closed-loop direct kinematics algorithm, Robotica 17(4) (1999) 437445.8 M. Callegari, A. Suardi, Functionally-oriented pkms for robot cooperation, in: Proceedings of the 8th conference in IntelligentAutonomous Systems.9 G. Chung, B. Yi, D. Lim, W. Kim, An ecient dynamic modeling methodology for a general type of hybrid robotic systems, in:Proceedings of the ICRA2004.10 U. Thomas, I. Maciuszek, F. Wahl, A unified notation for serial, parallel, and hybrid kinematic structures, in: Proceedings of theICRA2002.11 K. Zanganeh, J. Angeles, Displacement analysis of a six-degree-of-freedom hybrid hand controller, in: Proceedings of
- 温馨提示:
1: 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
人人文库网所有资源均是用户自行上传分享，仅供网友学习交流，未经上传用户书面授权，请勿作他用。
川公网安备: 51019002004831号