Most legged animals use their flexible body and supporting muscles to produce power for their locomotion, resulting in superior mobility and fast motions. In reality, an animal body consists of multiple bones and joints as well as legs having two or three segments with mass and inertia. In this paper, we study the bounding locomotion of a quadruped robot with a model closer to a real animal, i.e., a model that has one spinal joint, multiple two-segmented prismatic legs with masses and series elastic actuators, to obtain an insight into the robot’s dynamic behaviors. The models with passive mechanical properties are optimized with open-loop control to achieve the periodic bounding gait. The effects of spine flexibility in a segmented body are investigated on quadrupedal bounding gait by changing dynamic properties and hardware parameters. Comparisons of models reveal that body flexibility affects energy consumption and increases leg recirculation and stride length. The cost of transport of the articulated spine models is smaller than that of the rigid body one at low speed (\(< 0.45\sqrt{gl_0}\)) and bigger at high speed (\(>0.45\sqrt{gl_0}\)). The stride length increases 25%. Furthermore, the study on location of spinal joint reveals that the asymmetric segmented body possesses bigger spine oscillation; up to 370% higher actuator force/torque in the rear leg but 36.1% smaller in the front leg; shorter stride period; and smaller cost of transport which helps the robot to run more efficiently. The study also shows that the asymmetric mass distribution of the body caused the torque/force increase at the rear leg, especially at hip joint, and the decrease at the front leg.

中文翻译：

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四足机器人对脊椎关节的影响研究

大多数有腿动物利用其灵活的身体和支撑肌肉为其运动产生动力，从而实现出众的活动性和快速运动。实际上，动物的身体由多个骨骼和关节以及具有两个或三个具有质量和惯性的部分的腿组成。在本文中，我们研究了四足机器人的边界运动，该模型具有更接近真实动物的模型，即具有一个脊椎关节，具有质量的多个两段式棱柱形腿和一系列弹性致动器的模型，以深入了解机器人的动态行为。通过开环控制对具有被动机械性能的模型进行优化，以实现周期性的边界步态。通过更改动态属性和硬件参数，研究了四肢包围步态对脊椎柔性的影响。模型的比较表明，身体的柔韧性会影响能量消耗并增加腿部循环和步幅。在低速时，铰接式脊柱模型的运输成本比刚体模型的运输成本小（\（<0.45 \ sqrt {gl_0} \））并在高速下更大（\（> 0.45 \ sqrt {gl_0} \））。步幅增加25％。此外，对脊椎关节位置的研究表明，不对称的节段体具有较大的脊柱振荡；后腿的执行器力/扭矩高出370％，而前腿的减小36.1％; 步幅更短；以及较小的运输成本，这有助于机器人更高效地运行。研究还表明，身体的不对称质量分布导致后腿（尤其是髋关节）的扭矩/力增大，而前腿的扭矩/力减小。