Abstract
Recently, the development of agile-legged robots that mimic the structures and functions of biological muscles and tendons of quadruped mammals has attracted significant attention. The driving force of muscles and the elastic force of muscles and tendons can help improve the performances of these robots. Thus far, most of these robots have been developed based on the muscle-tendon complex of the lower legs. However, some mammals have a larger muscle-tendon complex on the upper legs, which contributes significantly to agile movements. In this study, a legged robot that mimics the functions of the bi-articular muscle-tendon complex of the thigh was developed, and its effects on static and dynamic movements were verified through simulations and experiments. While maintaining a static posture, the transfer of torque between two joints in the thigh mechanism reduced the power consumption by the robot’s motors by half, used for balancing the gravity of the robot. For a dynamic vertical jump, the motion trajectory generation for the robot was performed using non-linear optimization to maximize the jump height. As a result, the jump height was significantly enhanced by the effect of the thigh mechanism, and the height was more than twice the leg length.
Highlights
Among the quadruped mammals, felines enable agile performances
Because a large torque is required for extending the knee joint both for maintaining the posture in the stance phase and for kicking on the ground in dynamic motions, both static and dynamic performances of a legged robot may be improved by introducing the thigh muscle-tendon complex
DYNAMIC EFFECT OF THIGH MUSCLE-TENDON COMPLEX Based on the results presented in Section III, the large muscle-tendon complex was found to be effective in maintaining a static posture
Summary
Felines enable agile performances. For example, a cheetah is the fastest mammal on land and is known to run at a maximum speed of 29 m/s [1]. Among the one-legged robots that have elastic elements that mimic the structure of the muscles and tendons of mammals, some robots have an elastic mechanism that extends the knee joint to enhance performance. Focusing on the musculoskeletal structure of feline mammals that move instantaneously, a leg ‘‘Sugoi-Neco Legs’’ that mimics the muscle-tendon complex between the knee and ankle joints was developed [19]. Because a large torque is required for extending the knee joint both for maintaining the posture in the stance phase and for kicking on the ground in dynamic motions, both static and dynamic performances of a legged robot may be improved by introducing the thigh muscle-tendon complex. A mechanism that mimics the functions of the thigh muscle-tendon complex is introduced in a legged robot to enhance its performances during both the static and dynamic movements. The muscle-tendon complex can store and reuse elastic energy using its elasticity
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