Quadruped mammals coordinate spinal bending and axial compression to enhance locomotion agility and efficiency. However, existing robotic spines typically lack the active compliance required to support such dynamic behaviours. We present SPARC, a compact 3-DoF sagittal-plane spine module that enables simultaneous revolute and prismatic motions within a 1.26 kg package. Using a floating-base impedance controller, we facilitate independent, task-space tuning of spinal stiffness and damping to mimic biological load-bearing strategies. Benchtop experiments confirm high-fidelity rendering of commanded impedance, with linear force-displacement error within 1.5%. Systematic locomotion simulations reveal a critical speed-dependency: while low-speed efficiency is insensitive to spinal properties, precise impedance tuning becomes indispensable for high-speed performance. Our results demonstrate that an optimally compliant spine reduces power consumption by 21% at 0.9 m/s compared to a rigid-spine baseline. This efficiency gain is mechanistically attributed to the spine's role in augmenting stride length and acting as a mechanical low-pass filter to attenuate high-frequency torque fluctuations. SPARC provides an open-source platform for systematic studies of spine compliance in legged locomotion. Available at: github.com/YueWang996/sparc

翻译：四足哺乳动物通过协调脊柱弯曲与轴向压缩来提升运动灵活性与效率。然而，现有机器人脊柱通常缺乏支持此类动态行为所需的主动顺应性。本文提出SPARC，一种紧凑型3自由度矢状面脊柱模块，可在1.26 kg的封装内实现旋转与棱柱运动的同步执行。通过采用浮动基阻抗控制器，我们实现了脊柱刚度与阻尼在任务空间的独立可调，以模拟生物负载承载策略。台架实验验证了指令阻抗的高保真呈现，线性力-位移误差控制在1.5%以内。系统性运动仿真揭示了关键的速度依赖性：虽然低速运动效率对脊柱特性不敏感，但精确的阻抗调谐对高速性能至关重要。实验结果表明，在0.9 m/s速度下，具有最优顺应性的脊柱相较于刚性脊柱基准可降低21%的功耗。这种能效提升的机制归因于脊柱在增大步幅长度以及作为机械低通滤波器衰减高频扭矩波动方面的作用。SPARC为系统研究腿式运动中脊柱顺应性提供了开源平台。项目地址：github.com/YueWang996/sparc