Lower Limb Assistive Devices

丧失行动能力和独立性通常被描述为一个人所能忍受的最可怕的创伤之一。为了科普这一挑战，截肢者依靠假肢，或更好地称为假肢。根据美国矫形师和修复师学会，到2020年，仅在美国，使用矫形器和修复器的总人数预计将分别达到730万和240万。更令人震惊的是，数据表明，使用辅助设备的人数日益增加，特别是在18至44岁的年轻人中，他们希望享受健康和积极的日常生活。尽管技术和医学不断进步，但下肢截肢者仍然面临许多挑战，这些挑战阻止他们恢复原始运动能力并减少运动期间的代谢能量消耗。目前开发的下肢假体在过去十年中已经有了显著的改进;然而，绝大多数仍然缺乏与生物肢体中的骨骼肌相对应的致动元件。从机械角度来看，常见的可用装置为患者提供稳定性，并且通常包括吸收和耗散能量以实现舒适步态的机构;然而，这些装置不能在肢体关节周围收集和产生净功率。对于平地行走，这种缺陷可能是合理可接受的;然而，使用者不能上下楼梯或从坐姿站起来。在过去的几十年里，开发动力下肢假肢一直是一项工程挑战。许多原型已经在研究实验室中开发，目前可从OSSUR获得商业器械（即Power Knee）。然而，这些装置的成功主要受到其致动系统的效率的阻碍，致动系统反复地依赖于重型且大功率的电动机和齿轮。与骨骼肌不同，电动马达不具有被动行为，这阻止它们收集步态能量，因此，在整个关节运动中，甚至在稳定位置期间，必须消耗连续的电能。虽然有大量的致动器可用于广泛的商业应用，但很少有可用于下肢辅助技术。这种独立的应用需要紧凑、重量轻、功能强大且节能的致动器。气动人工肌肉（PAM）具有相似的力学行为，是一种很有前途的人体辅助装置驱动器。由于其生物肌肉样特性，PAM具有主动和被动使用的潜力，从而允许采集步态能量，这可以产生高效的致动系统。虽然有许多人声称PAM是生物医学应用的理想致动器，但没有定量研究证实PAM用于下肢辅助设备的可行性。本研究首先实现了下肢生物力学的全面研究，以表征其驱动要求，随后验证了一种新设计的PAM下肢辅助设备。接下来，本研究提出了PAM动力经股骨和经胫骨假体的设计，这将允许下肢截肢者恢复他们的运动自由度，并减少运动过程中的代谢能量消耗。与目前技术先进的下肢假肢不同，所提出的设备将是负担得起的和功能性的，允许用户的原始运动能力被恢复，并实现运动期间代谢能量消耗的减少。

The loss of mobility and independence is commonly described as one of the most horrific traumas that an individual can endure. To cope with this challenge, amputees rely on prostheses, or better known as artificial limbs. With reference to the American Academy of Orthotists and Prosthetists, by the year 2020, in the United States alone, the total number of individuals who use orthotics and prosthetics is expected to reach 7.3 and 2.4 million, respectively. More alarming, data indicate increasing growth in use of assistive devices particularly among the young age segment 18 to 44 years old who expect to enjoy a healthy and active daily life. Despite progression in technology and medicine, lower limb amputees still endure many challenges that prohibit them from regaining their original movement abilities and reducing the metabolic energy consumption during locomotion. Current developed lower limb prostheses have drastically improved over the past decade; however, the vast majority still lacks the actuation elements that correspond to the skeletal muscle in a biological limb. From a mechanical perspective, the common available devices offer patients stability and often include a mechanism to absorb and dissipate energy for a comfort gait; however, these devices are incapable of harvesting and generating net power about the joints of the limb. This deficiency may be reasonably acceptable for level ground walking; however, users are unable to ascend and descend stairs or to stand up from a sitting position. Developing powered lower limb prostheses has been an engineering challenge for the past decades. Many prototypes have been in development in research laboratories and presently a commercial device is available from OSSUR (i.e. Power Knee). However, the success of these devices has been mainly hindered by the efficiency of their actuation system which recurrently relies on heavy and powerful electrical motors and gears. Unlike skeletal muscle, electrical motors do not possess a passive behavior, which prohibits them from harvesting gait energy, and thus, continuous electrical energy must be consumed throughout joint motion and even during steady position. While there are a large number of actuators that can be used for a wide range of commercial applications, very few have been feasible for lower limb assistive technologies. Such self-contained applications require a compact, lightweight, powerful and energy efficient type of actuator. Possessing similar mechanical behaviors, the Pneumatic Artificial Muscle (PAM) has been long-sought as a promising actuator for human assistive devices. Due to its biological muscle-like properties, PAMs have the potential to be used actively and passively, thus allowing for gait energy to be harvested, which can yield to a highly efficient actuation system. Whereas there have been many claims that the PAM is an ideal actuator for biomedical applications, there is no quantitative study that confirms the feasibility of the PAM for lower limb assistive devices. This research has first achieved a comprehensive study of lower limbs biomechanics to characterize its actuation requirements and subsequently validated a newly designed PAM for lower limb assistive devices. Next, this research proposes the design of PAM powered transfemoral and transtibial prostheses which would permit lower limb amputees to regain their freedom of movement and reduce the metabolic energy consumption during locomotion. Unlike current technologically advanced lower limb prostheses, the proposed devices will be affordable and functional allowing the user’s original movement abilities to be restored and a reduction of the metabolic energy consumption during locomotion is achieved.