On the structure optimization and kinematics analysis of the lower extremity exoskeleton robot

Transcription

1 On the structure optmzaton and knematcs analss of the lower etremt eoskeleton robot Mng Lu a, Xuanuan Zhu, Shuzh Sun, Xangguang Jang, We Zheng, Xuebn Lu College of Mechancal and Electronc Engneerng, Shandong Unverst of Scence and Technolog Qngdao , Chna. Abstract a @qq.com Desgned a knd of lower etremt eoskeleton robot to assst the dsabled, the elderl and patents wth lower etremt muscle weakness, basng on the analss of human walkng gat and the degrees of freedom of the lower etremtes to carr out the optmzaton desgn of mechancal structure. Usng CAD software Soldworks to model the lower etremt eoskeleton,make ever as of rotaton as possble through the center of the jont, added some buffer devce to make the wearer feel more fleble and comfortable. Usng the D-H method to knematcs analss the unlateral lower etremt of lower etremt eoskeletonand. provded a reference for the net step to desgn a new tpe of asssted walkng lower etremt eoskeleton robot prototpe. Kewords Lower etremt eoskeleton, mechancal structure, Soldworks, D-H method. 1. Introducton Lower etremt eoskeleton robot technolog s an emergng technolog developng rapdl n recent ears, has plaed an mportant role n the feld of mltar, medcne, has made great achevements after decades development[1-2], has become one of research hot spots n the world.there are bascall three knds of lower etremt eoskeleton robots. The frst s the lower etremt eoskeleton robot wth enhances human functon, whch s manl used n mltar and earthquake relef work, such as BLEEX [3-4], XOS;The second s the rehabltaton tranng lower etremt eoskeleton robot, whch s manl used to assst doctors and rehabltaton tranng for patents, such as Lokomat[5].The thrd s the assst walkng lower etremt eoskeleton robot, whch s manl used to assst walkng dsabled people, elderl and lower etremt muscle weakness, and mprove ther self-management ablt, such as HAL [6-7], ReWalk.Ths paper manl studes the thrd, t's dfferent from the frst and two knds, the mechancal structure of the thrd knds has good fleblt and certan bearng stablt.in order to reduce the mpact on the human bod, some cushonng devces should be added to the eoskeleton. 2. Movement Mechansm The lower etremt eoskeleton s worn b people and walkng snchronzaton wth human, so should be research the humans of the gat frst, people s walk has the characterstc of perodc and legs smmetrcal, andmovement basc s completed n the sagttal plane.the gat ccle can be dvded nto support and swng phase, now take rght foot for reference,see Fg. 1. It s defned support phase from the rght foot heel just touches the ground to tptoe just left the ground, whch 196

2 Fg.1.Human walkng ccle accounts for about 60% of the gat ccle.defned swng phase s from the toe of the rght foot to the heel just touchng the ground, whch accounts for about 40% of the gat ccle.in addton, the whole gat can be dvded nto the sngle-foot support perod and the double-foot support perod [8]. The desgn of the robot of lower etremt eoskeleton begns wth the laout of ts structure freedom, so t s necessar to understand the characterstcs of knematcs of human bod.human unlateral lower etremt wth a total of seven degrees of freedom, the hp jont, ankle jont wth three degrees of freedom, abducton/adducton, fleon/etenson and rotaton moton, knee jont has onl one fleon movement.the range of hp jont and knee jont s wde, the range of ankle jont s small and s generall aular [9]. 3. Mechancal Structure The desgn of the mechancal structure of lower etremt eoskeleton should take nto account the followng ponts: (1) The degree of freedom and poston of the lower etremt eoskeleton should be reference to the human bod, and the sze of the bar should be adjusted to sut the human of dfferent heght and bod tpes. (2) The lower etremt eoskeleton robot degrees of freedom of jonts correspondng to the human bod, to ensure the movement form s the same as human, each rotaton aes pass through the center of jont ; (3) There must be a certan lmt devce for each jont of the lower etremt eoskeleton, whch should not onl have the necessar moton scope but also ensure the safet of the wearer's movement. (4) The lower etremt eoskeleton robot s as smple as possble, wth lght weght and eas to carr, whch can accommodate man dfferent envronments, such as flat, slopng land, grassland, star, etc. Due to t s bgger force that hp, knee and ankle n sagttal plane when people n the walk, squat, cetremt stars, and n most sports, the hp, knee, and ankle jonts are actvel drven.the adducton/abducton moton of hp take actvel drven plaed an mportant role n the walk, related to the movement of fleblt. The mechancal structure of the hp jont of the eoskeleton robot,see Fg.2, there are three degrees of freedom of hp, fleon/etenson and adducton/abducton moton n the process of the walkng moton ampltude s bgger to take the motor drve, and t lmts the scope of actvtes to protecton the human bod.rotaton moton s the passve jont, whch s drven b the user's correspondng jonts.the thgh bar and the wast pole are used n the rod structure, and ther length can be adjusted to sut dfferent bod tpes. 197

3 Fg.2. Hp jont mechancal structure Fg.3. Knee jont mechancal structure There s onl one fleon/etenson of the lower etremt eoskeleton robot knee jont see Fg. 3, thgh bars usng rod structure adjusted accordng to human leg length, and lmts the mamum range to protecton the human bod. Fg.4. Ankle mechancal structure The mechancal structure of lower etremt eoskeleton robot ankle jont [10],see Fg. 4,The foot s attached to the lower etremt eoskeleton, and motor fed on the motor frame, t s rotaton can be realzed toe fleon/dorsfleon movement. Inner rotatng bearngs can be rotated, and rotar moton and outreach/adducton movement have nstalled sprng dampng devce, when ou walk along t changes accordngl wth the human bod. 4. Knematcs Analss For the knematcs analss of lower etremt eoskeleton robot, t s necessar to make a proper smplfcaton of the model. Ths paper studes the unlateral lower etremt as an eample. The D-H method [11] s a method for studng the knematcs. The coordnate sstem s establshed see Fg. 5. s the angle from Z ˆ to Zˆ 1 measured about X ˆ ; s the dstance from Z ˆ to Zˆ 1 measured along X ˆ ; d s the dstance from X 1 ˆ from X 1 to X ˆ measured about Z ˆ, see Table Ⅰ. ˆ a to X ˆ measured along Z ˆ ;and s the angle 198

4 Fg.5.A sngle lateral lower etremt knematc coordnate sstem TABLE Ⅰ Lnk parameters Usng the lnkage transformaton formula, the coordnate sstem of the neghborng bars can be connected to each other, and the lnkage transformaton matr s used to represent : Epand on: T R ( ) D ( a ) R ( ) D ( d ) (1) 1 X 1 X 1 Z Z c s 0 a 1 1 s c 1 c c 1 s 1 s 1d T s s 1 c s 1 c 1 c 1d (where s s shorthand for sn, c for cos, Hereafter all adopt ths conventon) Substtutng table 1 parameters nto the values of 0 T, 1 T, 2 T, 3 T, T,the transformaton matr of the relatve base coordnate sstem of the foot s obtaned.: n o a p n o a p 5T = 1T2 T3 T4 T5 T = nz oz az p z The results of the epressons are as follows: T (2) (3)

5 nz s2 s3s45 c3c o s c s s c n c c c c s s s s c s c c (4) n c s c s c c s s s c c c (5) (6) o s s s c c c c s c s c c (7) o c s s c c c s s c c s c (8) z a az (9) a cs s s 1 2 c (10) (11) (12) p L c L s s c c c L s s c c c d c s (13) p L s L c s s c c L c s s c c d s s (14) p d c L s c L c s (15) z When ou enter multple jont varables, ou can get a seres of coordnate ponts (p,p,p z )(=1 n) of the foot relatve to the frame zero, ou can get the trajector. 5. Concluson In ths paper, the mechancal structure of lower etremt eoskeleton robot was optmzed., the results show that reasonable mechancal structure desgn can be both good fleblt and good stablt.the addton of some sprng dampng mechansms to the mechancal structure can reduce the mpact on human jonts.usng the results of the knematcs of the nsttuton, the end poston of the mechansm can be obtaned from the angles of the jonts, whch s the bass of the mechansm veloct analss, acceleraton analss and mechansm snthess.the movement of robot control s actuall controllng the moton of each jont drve motor, so that the moton of each jont s coordnated and the feet can be moved accordng to certan path n space. References [1] B.J. Maknson, General Electrc Co: Research and Development Prototpe for Machne Augmentaton of Human Strength and Endurance, Hardman I Project, General Electrc Report S , Schenectad, NY, [2] M. Vukobratovc, D. Hrstc, Z. Stojljkovc: Development of Actve Anthropomorphc Eoskeletons, Medcal and Bologcal Engneerng, 1974,p [3] Amundson K, Raade J, Handng N, et al. :Hbrd hdraulc-electrc power unt for feld and servce robots, Intellgent Robots and Sstems, 2005.(IROS 2005) IEEE/RSJ Internatonal Conference on. IEEE, 2005,p [4] Chu A, Kazeroon H, Zoss A: On the bommetc desgn of the berkele lower etremt eoskeleton(blee), Robotcs and Automaton, ICRA Proceedngs of the 2005 IEEE Internatonal Conference on. IEEE, 2005,p [5] G. Colombo, M. Jorg, V. Detz: Drven Gat Orthoss to do Locomotor Tranng of Paraplegc Patents, Proceedngs of the 22nd Annual Internatonal Conference of the IEEE Engneerng n Medcne and Bolog Socet (EMBS), Vol. 4, 2000,p [6] Kasaoka K, Sanka Y: Predctve control estmatng operator's ntenton for steppng-up moton b eo-skeleton tpe power assst sstem hal, lntellgent Robots and Sstems, 2001, p

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