Robotics Research Lab, Computer Science Department, Technische Universität Kaiserslautern, Kaiserslautern, Germany. Author to whom correspondence should be addressed.
Bioinspir Biomim. 2019 Sep 6;14(6):066002. doi: 10.1088/1748-3190/ab3896.
In a lower extremity musculoskeletal leg, the actuation kinematics define the interaction of the actuators with each other and the environment. Design of such a kinematic chain is challenging due to the existence of the redundant biarticular actuators which simultaneously act on two joints, generating a parallel mechanism. Actuator kinematics is mainly dependent on the moment arm profile of the actuation system. It is a common practice to select a constant moment arm value for robotic actuation system; nevertheless, biological muscles feature a distinctive nonlinear moment arm profile that has been ignored in the design of the musculoskeletal robots. In this paper, we propose a design paradigm for compliant robotic leg [Formula: see text] based on the direct replication of the human leg anatomy. The resulting mechanical system should (a) demonstrate a similar moment arm profile as in leg musculature, (b) exhibit expected physiological behavior of the muscles, (c) provide insight into the interaction of the actuators and possible improvement in the efficiency of the movements. We provide a comprehensive analysis of the moment arm profile of the leg musculature. The actuator kinematics of the designed leg is validated by comparing the contraction velocities of the muscles and actuators. The biological characteristics of the actuators are analyzed using the jump experiment data conducted on the previous version of the leg. The major physiological characteristics of the biarticular muscles, ligamentous action, and distal power transfer, is successfully demonstrated by the robotic leg. Our analysis demonstrates that the proposed structural design of the actuation system can improve the mechanical efficiency of this particular jump experiment up to [Formula: see text] compared to the leg without actuator redundancy. Compared to the previous version of the leg, by only modifying the moment arm profiles, we can achieve an efficiency improvement of approximately [Formula: see text].
在下肢运动骨骼中，驱动运动学定义了执行器之间以及与环境的相互作用。由于冗余双关节执行器同时作用于两个关节，产生一个并联机构，因此设计这样的运动链具有挑战性。执行器运动学主要取决于驱动系统的力臂轮廓。为机器人驱动系统选择一个恒定的力臂值是一种常见的做法；然而，生物肌肉具有独特的非线性力臂轮廓，这在运动骨骼机器人的设计中被忽略了。在本文中，我们提出了一种基于人体腿部解剖结构直接复制的柔顺机器人腿部[Formula: see text]的设计范例。由此产生的机械系统应该(a)表现出与腿部肌肉相似的力臂轮廓，(b)表现出肌肉的预期生理行为，(c)深入了解执行器的相互作用和运动效率的可能提高。我们对腿部肌肉的力臂轮廓进行了全面分析。通过比较肌肉和执行器的收缩速度，验证了设计腿部的执行器运动学。使用以前版本腿部进行的跳跃实验数据，对执行器的生物特性进行了分析。机器人腿部成功地展示了双关节肌肉、韧带作用和远端动力传递的主要生理特性。我们的分析表明，与没有执行器冗余的腿部相比，所提出的驱动系统结构设计可以将特定跳跃实验的机械效率提高[Formula: see text]。与以前版本的腿部相比，只需修改力臂轮廓，我们就可以实现大约[Formula: see text]的效率提高。
