在日常生活活动(ADL)期间,手腕主要从事手部的定位和指挥。研究表明,恢复手腕活动能力可以显著增强,减少由运动补偿引起的身体失真,提高截肢者的生活质量。然而,大多数日常活动,尤其是精致的,对手腕保持一定旋转角度的能力提出了很高的要求,也称为非后向驱动能力,这对假肢手腕的设计提出了挑战。为了解决这个问题,已经提出了各种解决方案,包括电机保持制动器,高减速比减速器,和蜗轮。然而,电动机保持制动器仅在停电后起作用,并且不能连续阻止来自负载端的扭矩。后两种解决方案可能会改变传动比,导致运动速度和传动效率降低。因此,如何在不改变传动比的情况下设计一种小型化的非反向驱动机构,使前臂的旋转自由度可以在任何时间内锁定在任何位置,是假肢腕部设计研究中需要解决的问题。本文提出了一种基于线接触的非反向驱动离合器(NBDC),不会引起传动比的变化,保证假肢的运动性能。同时,它不会在正向传动过程中引入额外的摩擦,保证整体效率。最重要的是,它只允许扭矩从电机传递到负载,即使在电源故障情况下,也可以防止负载反向驱动,显著提高稳定性,安全,和舒适。对工作过程进行了详细的运动学和静态分析,并进行了瞬态动力学仿真以验证其有效性。通过实验,证明了输出端的自锁扭矩可以达到约600Nmm,输入端的解锁力矩约为80Nmm,可以有效地集成在假肢腕关节旋转中,有助于表演,假肢关节系统的安全性和节能性。
During activities of daily living (ADLs), the
wrist is mainly engaged in positioning and directing the hand. Researches have demonstrated that restoring
wrist mobility can significantly enhance the manipulation ability, reduce body distortion caused by motion compensation, and improve the quality of life for amputees. However, most daily activities, particularly the delicate ones, place high demands on the ability of
wrist to maintain a certain rotation angle, also known as non-back-drivable ability, which poses a challenge to the design of prosthetic wrists. To address this issue, various solutions have been proposed, including motor holding brakes, high reduction ratio reducers, and worm gears. However, the motor holding brake only functions after a power outage and cannot continuously prevent torque from the load end. The latter two solutions may alter the transmission ratio, resulting in reduced movement speed and transmission efficiency. Therefore, how to design a miniaturized non-back-drivable mechanism without changing the transmission ratio so that the forearm rotational freedom can be locked at any position for any duration is a problem to be solved in the research of prosthetic
wrist designs. This paper presents a line-contact based non-back-drivable clutch (NBDC) that does not cause changes in the transmission ratio, ensuring the motion performance of the prosthetic limb. At the same time, it does not introduce additional friction in the forward transmission process, guaranteeing the overall efficiency. Most importantly, it only allows the torque transmitting from the motor to the load, prevents the load reversely from driving back even in a power failure condition, significantly improving the stability, safety, and comfort. Detailed kinematic and static analyses of the working process has been conducted, and transient dynamics simulation has been performed to verify its effectiveness. Through experiments, it is demonstrated that the self-locking torque of the output end could reach approximately 600 Nmm, and the unlocking torque of the input end is about 80 Nmm, which can be effectively integrated in prosthetic
wrist rotation joints, contributing to the performance, safety and energy saving of prosthetic joint systems.