Hunt Alexander J, Odle Brooke M, Lombardo Lisa M, Audu Musa L, Triolo Ronald J
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA.
Department of Mechanical and Materials Engineering, Portland State University, 1930 SW 4th Ave, Portland, OR, 97201, USA.
J Neuroeng Rehabil. 2017 Jun 10;14(1):54. doi: 10.1186/s12984-017-0266-6.
Implanted motor system neuroprostheses can be effective at increasing personal mobility of persons paralyzed by spinal cord injuries. However, currently available neural stimulation systems for standing employ patterns of constant activation and are unreactive to changing postural demands.
In this work, we developed a closed-loop controller for detecting forward-directed body disturbances and initiating a stabilizing step in a person with spinal cord injury. Forward-directed pulls at the waist were detected with three body-mounted triaxial accelerometers. A finite state machine was designed and tested to trigger a postural response and apply stimulation to appropriate muscles so as to produce a protective step when the simplified jerk signal exceeded predetermined thresholds.
The controller effectively initiated steps for all perturbations with magnitude between 10 and 17.5 s body weight, and initiated a postural response with occasional steps at 5% body weight. For perturbations at 15 and 17.5% body weight, the dynamic responses of the subject exhibited very similar component time periods when compared with able-bodied subjects undergoing similar postural perturbations. Additionally, the reactive step occurred faster for stronger perturbations than for weaker ones (p < .005, unequal varience t-test.) CONCLUSIONS: This research marks progress towards a controller which can improve the safety and independence of persons with spinal cord injury using implanted neuroprostheses for standing.
植入式运动系统神经假体在提高脊髓损伤导致瘫痪者的个人移动能力方面可能是有效的。然而，目前用于站立的神经刺激系统采用恒定激活模式，对不断变化的姿势需求无反应。
在这项研究中，我们开发了一种闭环控制器，用于检测脊髓损伤患者向前的身体干扰并启动稳定步骤。通过三个安装在身体上的三轴加速度计检测腰部向前的拉力。设计并测试了一个有限状态机，以触发姿势反应并对适当的肌肉施加刺激，以便在简化的急动信号超过预定阈值时产生保护性步骤。
对于体重10%至17.5%之间的所有扰动，控制器有效地启动了步骤，对于体重5%的扰动偶尔启动姿势反应并伴有步骤。对于体重15%和17.5%的扰动，与经历类似姿势扰动的健全受试者相比，受试者的动态反应表现出非常相似的成分时间段。此外，较强扰动的反应性步骤比较弱扰动的反应性步骤发生得更快（p < 0.005，方差不等t检验）。结论：这项研究朝着一种控制器取得了进展，该控制器可以使用植入式神经假体站立来提高脊髓损伤患者的安全性和独立性。
