Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China.
Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
J Biomech. 2019 Jun 11;90:33-39. doi: 10.1016/j.jbiomech.2019.04.025. Epub 2019 Apr 22.
Besides the leg force actuator, humans also use a hip torque actuator during the step-to-step transition to redirect the velocity of CoM (Center of Mass). Although the leg force actuator has been widely studied, few researches analyze the hip torque actuator during the step-to-step transition. In this paper, we build a powered walking model which consists of a point mass linked with two compliant legs. Each leg has a spring and a damper in parallel. Two types of active actuators, the force actuator on the leg and the torque actuator at the hip, are added to simulate the leg force and hip torque actuator during the step-to-step transition. The cycle walk is solved by numerical simulations under different hip torque strength, and the energetics and stability are evaluated. The simulation results show that the hip torque actuator can reduce the energy cost and improve the stability of walking. Further analysis shows that the hip torque actuator can reduce mechanical works of both legs with small extra energy cost. To understand the principle of hip torque actuator, the CoM dynamics is analyzed. It is shown that the hip torque actuator is efficient on the redirection of CoM. Thus, it can improve the stability and reduce required forces of both legs, which decreases the energy cost. Our work provides a fundamental understanding of the hip torque during the step-to-step transition, and may help improve the design of bipedal robots and prosthesis.
除了腿部力致动器，人类在步移转换过程中还使用髋关节扭矩致动器来重新定向质心（Center of Mass）的速度。虽然腿部力致动器已被广泛研究，但很少有研究分析步移转换过程中的髋关节扭矩致动器。在本文中，我们构建了一个由一个点质量与两个顺应腿相连的动力步行模型。每条腿都有一个弹簧和一个阻尼器并联。添加了两种主动致动器，即腿部的力致动器和髋关节的扭矩致动器，以模拟步移转换过程中的腿部力和髋关节扭矩致动器。在不同髋关节扭矩强度下通过数值模拟求解循环行走，并评估能量学和稳定性。模拟结果表明，髋关节扭矩致动器可以降低能量成本并提高行走的稳定性。进一步的分析表明，髋关节扭矩致动器可以减少双腿的机械功，同时只需额外消耗少量能量。为了理解髋关节扭矩致动器的原理，我们分析了质心动力学。结果表明，髋关节扭矩致动器在质心的重新定向方面非常有效。因此，它可以提高稳定性并降低双腿所需的力，从而降低能量成本。我们的工作为步移转换过程中的髋关节扭矩提供了基本的理解，并可能有助于改进双足机器人和假肢的设计。
