Clutched elastic actuator to drive a lower limb exoskeleton hip joint for paraplegic patients
Yulin LIU,Yinbo LI,Renhao LU,Xinyu GUAN*(),Linhong JI
Division of Intelligent and Biomechanical System, State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
Lower limb exoskeletons can help paraplegic patients walk through rehabilitation. Powered exoskeletons do not require much muscle strength in the affected limbs, but the drive motors are rather large and heavy. Unpowered energy-storage exoskeletons do not require motors, but require more patient muscle strength which may cause fatigue during continuous use. This paper describes a clutched elastic actuator based on a ratchet mechanism that can be used as the hip joint driver for a lower limb of an exoskeleton. Patients rely on their upper limb and trunk muscles and crutches to slowly transfer the center of gravity during the support phase. The motor then stores energy during this motion in a torsional spring. During the swing phase, the torsional spring then quickly releases energy to help the patient step forward and complete a gait cycle. This paper presents a model for the driver during the support phase (spring energy storage) and the swing phase (spring energy release). The angular acceleration and deceleration are selected to minimize the peak power. Simulations show that the clutched elastic actuator significantly reduces the average power and the peak power compared with a motor and gearbox driving the patient's hip joint. Therefore, the system can have small low torque, low power motors to reduce the size and weight of the actuators and the entire exoskeleton.
KIRSHBLUM S C , BURNS S P , BIERING-SORENSEN F , et al. International standards for neurological classification of spinal cord injury (Revised 2011)[J]. The Journal of Spinal Cord Medicine, 2011. 34 (6): 535- 546.
doi: 10.1179/204577211X13207446293695
2
MAIMOUN L , FATTAL C , MICALLEF J , et al. Bone loss in spinal cord-injured patients:From physiopathology to therapy[J]. Spinal Cord, 2006. 44 (4): 203- 210.
doi: 10.1038/sj.sc.3101832
3
JOHNSON W B , FATONE S , GARD S A . Walking mechanics of persons who use reciprocating gait orthoses[J]. Journal of Rehabilitation Research and Development, 2009. 46 (3): 435- 446.
4
COLOMBO G , WIRZ M , DIETZ V . Driven gait orthosis for improvement of locomotor training in paraplegic patients[J]. Spinal Cord, 2001. 39 (5): 252- 255.
doi: 10.1038/sj.sc.3101154
5
陈峰.可穿戴型助力机器人技术研究[D].合肥:中国科学技术大学, 2007.
5
CHEN F. Research on the wearable power assist robot[D]. Hefei: University of Science and Technology of China, 2007. (in Chinese)
6
ESQUENAZI A , TALATY M , PACKEL A , et al. The ReWalk powered exoskeleton to restore ambulatory function to individuals with thoracic-level motor-complete spinal cord injury[J]. American Journal of Physical Medicine & Rehabilitation, 2012. 91 (11): 911- 921.
7
PAN Y T, LAMB Z, MACIEVICH J, et al. A vibrotactile feedback device for balance rehabilitation in the EksoGTTM robotic exoskeleton[C]//Proceedings of the 7th IEEE International Conference on Biomedical Robotics and Biomechatronics (Biorob). Kuala Lumpur, Malaysia: IEEE, 2018: 569-576.
8
IMAI H, NOZAWA M, KAWAMURA Y, et al. Human motion oriented control method for humanoid robot[C]//Proceedings of the 11th IEEE International Workshop on Robot and Human Interactive Communication. Berlin, Germany: IEEE, 2002: 211-216.
9
AUDU M L , TO C S , KOBETIC R , et al. Gait evaluation of a novel hip constraint orthosis with implication for walking in paraplegia[J]. IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2010. 18 (6): 610- 618.
doi: 10.1109/TNSRE.2010.2047594
10
GUAN X, JI L, WANG R, et al. Optimization of an unpowered energy-stored exoskeleton for patients with spinal cord injury[C]//Proceedings of the 38th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). Orlando, FL, USA: IEEE, 2016: 5030-5033.
11
WHITTLE M W . Gait analysis:An introduction[M]. 2nd ed. London: Reed Educational and Professional Publishing, 1997. 125- 142.
12
吴谦.截瘫助行下肢外骨骼稳定步态参数学习及其仿真实现[D].成都:电子科技大学, 2019.
12
WU Q. Simulation realization of stable gait parameters learning for paraplegic lower limb walking assistance exoskeleton[D]. Chengdu: University of Electronic Science and Technology of China, 2019. (in Chinese)
13
LI Y, LI Z, PENZLIN B, et al. Design of the clutched variable parallel elastic actuator (CVPEA) for lower limb exoskeletons[C]//Proceedings of the 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). Berlin, Germany: IEEE, 2019: 4436-4439.
14
LI Y , GUAN X , LI Z , et al. Analysis, design, and preliminary evaluation of a parallel elastic actuator for power-efficient walking assistance[J]. IEEE Access, 2020. 8, 88060- 88075.
doi: 10.1109/ACCESS.2020.2993183
16
WINTER D A . Biomechanics and motor control of human movement[M]. 4 ed. New Jersey: John Wiley & Sons, 2009. 83- 86.
17
LI Y , GUAN X , HAN X , et al. Design and preliminary validation of a lower limb exoskeleton with compact and modular actuation[J]. IEEE Access, 2020. 8, 66338- 66352.
doi: 10.1109/ACCESS.2020.2985910
18
GUAN X , LIU Y , GAO L , et al. Trunk muscle activity patterns in a person with spinal cord injury walking with different un-powered exoskeletons:A case study[J]. Journal of Rehabilitation Medicine, 2016. 48 (4): 390- 395.
doi: 10.2340/16501977-2065
2021, Vol. 61 
),季林红
