Evaluation of Armrest and Handle design on Upper-body rehabilitation equipment Joohyun Sim, Jonghyun Kim, Jaesoo Hong, Keyoungjin Chun Gerontechnology Center, Korea Institute of Industrial Technology, Cheon-an ABSTRACT Objective: The aim of this study is evaluation of arm support and handle design in grahamizer(upper rehabilitation equipment). Background: In this recent, population of elderly has increased in Korea. So upper limb rehabilitation has been increased importance. The grahamizer is rehabilitation equipment of upper-body generally. However, Design research of Grahamizer by exercise Characteristics are nonexistent in development of upper limb rehabilitation. Method: In this study, usability evaluation of armrest and handle design was performed.; (1) The survey of leading research about handle design, (2) Motion analysis of armrest by variation of central axis, (3) Motion analysis of armrest by variation of armrest's length. Results: The leading research showed that diameter of handle: 3.5cm, shape of handle : D type. The results of this study showed that length of armrest: 220cm, Position of central axis: 3. Conclusion: In the results of this study, Method of design evaluation through handle's trajectory and motion analysis of upper body is very effective method. So evaluation method of this study is expected to be used in development of upper limb rehabilitation equipment. Keywords: Grahamizer, Handle, Arm support, Handle trajectory, Motion capture 1. Introduction 한국통계청의고령자인구통계자료에의하면한국은이미 2000년고령화사회로진입하였고, 2014년에는고령사회에진입할것으로예상되어지고있다. 한편, 고령인구증가와함께신체의노화로인한뇌졸중등의후천적운동기능장애에대한재활의중요도도높아지고있다. 그중일상생활에서많이거동하는상지의재활과관련된최근의연구동향을살펴보면상지운동기능장애인을대상으로햅틱장치를사용하여피검자가직선운동을하였을때의 EMG, 손잡이의궤적등에관한연구를진행한사례가있다 (Lee et al., 2011). Grahamizer(Upper limb rehabilitation equipment: 상지재활운동기기 ) 는뇌졸중환자의재활훈련에서일반적으로사용되고있는장비이며구동시에는팔받침대를통해운동의힘을기기로전달하고, 신체를지지한다. 그러나팔받침대와손잡이부분에대한운동특성연구를통한디자인 및평가에대한연구는전무한실정이다. 따라서본연구에서는선행연구분석을통하여손잡이디자인가이드라인을제시하고, 팔받침대의설계요소에대한손잡이궤적분석을통하여 Grahamizer( 상지운동기기 ) 의팔받침대와손잡이디자인평가방법을제시하는것을연구목적으로한다. 2. Research of Handle Design 본연구에서는 쥐는것 : Grip' 에대한선행연구조사를통하여손잡이의중요한두가지디자인요소로형태와굵기를설정하였다. 엄지를제외한네손가락으로손잡이를잡고, 엄지는손잡이를휘감아인지와맞닿게잡는 Grip법이 Power grip이며 Grahamizer( 상지운동기기 ) 손잡이는 Power grip의형태로되어있다.
손잡이와관련된선행연구들중에서설계요소들에변화량을주어악력수치데이터와주관적만족도도출을통한실험결과를참고하여손잡이디자인요소에대한설계값을설정하였다. (Figure 1) Power grip 손잡이의형태에대한연구이다. A, D, I, V의 4가지형태는수공구 50개를조사하여선정한대표적인손잡이모양이다. 각손가락별힘을측정할수있는 MFFM(Multi -Finger Force Measurement system) 에적용하여실험하였으며악력에대한손가락의기여도와악력을발휘할때의편안함의정도에대해설문평가를하였다 (Figure 1). 그결과 D 형태에서주관적만족도와악력의측정값역시높게측정되었다 (Kong et al., 2009). 3.1 Experimental method 본연구에서는 VICON INC. UK의 MX-T20 카메라 10 대와상지회전운동이가능한실험장치를사용하여실험을수행하였다. 실험에사용된마커셋은손잡이의운동궤적을추적할수있는마커 1개를포함한총 11개의마커로마커의위치는 Vicon Support Team의 Upper limb model(vicon supporter team, 2007) 과 ISB(Inter -national Society of Biomachanics) 의 Landmark (Ge wu et al., 2005) 참고로하여구성하였다 (Figure 2~3). Figure 1. MFFM(Multi-Finger Force Measurement system) (Kong et al., 2009). 손잡이의최적굵기결정에관한선행연구에서는동일한길이의원통형실험봉을지름 2.0cm부터 0.5cm 간격으로 5.0cm까지 7가지로나누어실험봉의사용성을평가하였고, 실험결과는지름이 3.5cm일때가가장적합한손잡이굵기로도출되었다 (Byun et al., 1997). 따라서본연구에서는손잡이의지름이 3.5cm, 형태는 D type참고로하여, 향후사용성평가및디자인을진행할계획이다. Figure 2. The composition of segments and the position of axis. 3. Usability Evaluation of Armrest 본실험에서는상지재활기기의여러가지설계변수들중에운동궤적에직접적인영향을줄수있는주요설계변수로팔받침대의회전중심축위치와팔받침대길이를선 정하였다. 회전중심축의위치와팔받침대의길이가변화함에따라정상인의운동궤적을분석하였다. Figure 3. The Grahamizer(experiment equipment) and view from above on the set_up for the tracking task.
실험장치의손받침대길이를 4단계 (280mm, 220mm, 160mm, 100mm) 로나누어서 1차실험을진행하였고, 2 차실험인중심축의위치선정은 1차실험결과에서나온받침대길이 (220mm) 를기준으로하여 4단계 (1: 220mm, 2: 160mm, 3: 100mm, 4: 40mm) 로각부분의중심에서실험을진행하였다 (Figure 4~5). 피실험자는각위치에서반시계방향으로 5번반복하여회전운동을수행하였다. 실험에는총 4명의피실험자 ( 키 : 172.5±2.9cm, 몸무게 : 75.5±2.9kg, 나이 :27.7±1.7세, 남성 ) 가참여하였다. 실험결과변수는 Grahamizer( 상지운동기기 ) 동작에대한팔받침대길이별, 중심축별의핸들마커를토대로 XY 평면에서의운동궤적을도출하였다. 3.2 Result of experimental 팔받침대길이별실험에서의운동궤적결과를보면팔받침의길이가 220mm일때, 비교적일정한원형궤적으로나타났고, 안정적인운동이수행되었음을알수있었다. 궤적이놓인벡터도의한칸을기준으로각각도에서의진폭을비교했을시 1번과 4번은중간크기를벗어나는각도가 2번과 3번에비해많았으며, 각도간의진폭변화차이가크게나타났다.(Figure 6~7). Figure 4. The composition of length. Figure 6. The results of handle trajectory by change of arm support s length. Figure 5. The composition of central axis Figure 7. The results of Amplitude Comparison by change of arm support s length.
중심축위치에따른운동궤적결과는 3번, 4번에에서일정한형태로나타났다. 그러나 4번은 3번보다원형의크기가작으며, 다소일정하지못한부분이발견되었다. 궤적이놓인벡터도의한칸을기준으로각각도에서의진폭을비교했을시 1번과 2번은기준크기를벗어나는각도가확인되었으며, 각도간의진폭차이도크게나타났다. 그에비해 3번과 4번은기준크기내에서진폭의변화가적었다 (Figure 8~9). Figure 8. The results of handle trajectory by position of central axis. 4. Conclusion 본연구에서조사한선행연구들의핸드그립에대한 1970년대부터 1990년대까지의다소오래된연구결과들에서시대, 연령, 국가등의변수가있었지만그결과는큰차이가없었다. 현재의연구들을진행함에있어서참고하기에무리가없을것으로예상된다. 그러나본연구의주제인 Grahamizer( 상지운동기기 ) 의운동시의파지각도및위치에따른변수를제외한직접적인실험결과가아니기에실제운동시의손잡이파지각도및위치등의변수에따른결과차이가예상된다. 따라서향후연구는이를적용하여형태와굵기에대한 EMG, 동작분석, 체압분석등보다객관적이고, 정량적인실험데이터를얻을수있는장비를사용하여진행하고자한다. 팔받침대의사용성평가에서는상지재활기기의다양한설계요소중회전운동의중심축위치와 Grahamizer 팔받침대길이를선정하였고, 설계요소의변화량에따른회전운동궤적 ( 운동특성 ) 에대한결과를동작분석을통하여도출하였다. 본연구에서는중심축위치, 팔받침대길이변화에따라궤적의형태가다르게나타남을확인할수있었다. 이는상지재활기기의개발에있어중심축위치와팔받침대길이변화가운동효과에영향을미칠수있으며, 중심축의위치를가변적으로설계하는것이필요함을확인할수있었다. 이는사용자가자신의팔길이에맞게중심축위치를조절하여재활기기를사용할수있게함으로써최적의재활및운동효과를일으킬수있는실험결과이다. 향후재활및운동효과를최적화할수있는팔받침에대한실험및연구범위를확대하여진행할계획이다. Acknowledgements 본연구는보건복지부, 보건의료연구개발사업의지원을받아수행되어졌습니다. References Figure 9. The results of Amplitude Comparison by position of central axis. Lee, K. H., Kim, Y. T., Takahashi, Y., Miyoshi, T., Suzuki, K. and Komeda T., "Basic Experiment ON Rehabilitation of Upper-Limb Motor Function Using Haptic-Device System", Journal of the Korean Society of Mechanical Engineers, 5 (pp. 459-467), 2011.
Kong, Y. G., Son, S. T., Kim, D. M. and Jung, M. C., "Grip Force Finger Force, and Comfort analyses of young and Old People by Hand Tool Handle Shapes", Journal of the Ergonomics Society of Korea, 2 (pp. 27-34), 2009. Byun, S. N. and Lee, D. H., "A Study on Determination of an Optimal Handle Diameter for a Signal Billy", Journal of the Ergonomics Society of Korea, (pp. 15-27), 1997. VICON supporter team, "Upper limb model Produduct Guide", Vicon motion systems, 05-06, 2007. Ge Wu et al., "ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion-part 2: shoulder, elbow, wrist and hand", Journal of Biomechanics, 38, (981-992), 2005. Author listings Joohyun Sim: nandeh@kitech.re.kr Highest degree: BS, Department of Industrial Design Engineering, KUT Areas of interest: Development of senior friendly product, Usability test Jonghyun Kim: ddalki@kitech.re.kr Highest degree: MS, Department of Industrial Design Engineering, KUT Areas of interest: User Analysis, Usability test Jaesoo Hong: jshong94@kitech.re.kr Highest degree: MS, Department of Mechatronics Engineering, KUT Areas of interest: Development of senior friendly product, Usability test Keyoungjin Chun: chun@kitech.re.kr Highest degree: Ph. D, Department of Biomechanics, Michigan State Univ. Position title: Senior Researcher, Gerontechnology Center, KITECH Areas of interest: Development of senior friendly product