Lower Limb Assistive Devices

丧失行动能力和独立性通常被描述为一个人能忍受的最可怕的创伤之一。为了应对这一挑战，截肢者依靠假肢，或者更广为人知的假肢。根据美国矫形与假肢学会的数据，到2020年，仅在美国，使用矫形器和假肢的总人数预计将分别达到730万人和240万人。更令人震惊的是，数据表明，使用辅助装置的人数日益增加，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。*尽管在技术和医学上取得了进步，但下肢截肢者仍然面临着许多挑战，这些挑战使他们无法恢复原来的运动能力，也无法减少运动过程中的代谢能量消耗。在过去的十年中，目前开发的下肢假体有了很大的改进；然而，绝大多数仍然缺乏与生物肢体骨骼肌相对应的驱动元件。从机械角度来看，常见的设备为患者提供稳定性，通常包括一个吸收和消散能量的机制，以实现舒适的步态；然而，这些装置不能收集和产生肢体关节的净能量。这种不足对于平地行走来说是可以接受的；然而，使用者不能上下楼梯，也不能从坐姿站起来。*在过去的几十年里，开发动力下肢假肢一直是一个工程挑战。许多原型已经在研究实验室开发，目前OSSUR的商业设备（即Power Knee）可用。然而，这些装置的成功主要受到其驱动系统的效率的阻碍，该系统经常依赖于笨重而强大的电动机和齿轮。与骨骼肌不同，电动机不具有被动行为，这禁止它们收集步态能量，因此，在整个关节运动中，甚至在稳定位置时，必须连续消耗电能。虽然有大量的执行器可以用于广泛的商业应用，但很少有下肢辅助技术是可行的。这种独立的应用需要一种紧凑、轻便、强大和节能的执行器。气动人造肌肉（PAM）具有类似的机械行为，作为一种有前途的人体辅助装置执行器一直受到人们的追捧。由于其生物肌肉般的特性，pam具有主动和被动使用的潜力，从而允许步态能量的收集，这可以产生一个高效的驱动系统。*虽然有许多人声称PAM是生物医学应用的理想执行器，但没有定量研究证实PAM用于下肢辅助装置的可行性。本研究首先对下肢生物力学进行了全面的研究，以表征其驱动要求，随后验证了新设计的用于下肢辅助装置的PAM。接下来，本研究提出设计PAM驱动的经股骨和经胫骨假体，使下肢截肢者重新获得运动自由，减少运动时的代谢能量消耗。与目前技术先进的下肢假体不同，所提出的设备价格合理，功能齐全，可以恢复用户原有的运动能力，并减少运动过程中的代谢能量消耗。

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.