Dynamic Diagonal Model Principles for Energy-Efficient Humanoid Robotics: A Bio-Inspired Architecture Based on Three-Spiral Force Transmission

This theoretical framework proposes a bio-inspired robot architecture derived from the Dynamic Diagonal Model (DDM), a formalized theory of human motor coordination. Current humanoid robots suffer from a fundamental energy efficiency gap, consuming 10–20 times more energy per unit mass than biological systems. This inefficiency stems from architectural differences: robots use linear, joint-isolated force transmission, while biological systems employ helical/spiral transmission through integrated structures. The DDM mechanism centers on three-spiral synchronization: a femoral spiral generating rotational moments at the hip, a pelvic spiral distributing force through a segmented spine, and a foot spiral providing reactive stabilization. These spirals synchronize via a thoracolumbar pivot (T12-L1 analog), enabling emergent whole-body coordination—particularly the diagonal limb-torso patterns characteristic of efficient human gait. This document translates these biological principles into concrete engineering specifications for robotic implementation, including: Active 3-DOF hip rotation (±15°) 4–6 segment compliant spine with series elasticity Instrumented thoracolumbar pivot joint Multi-segment foot with controlled pronation/supination Coupled Central Pattern Generator (CPG) control architecture Computational modeling predicts 20–40% energy reduction compared to conventional architectures through distributed loading, enhanced elastic energy storage, and reduced control effort. The proposal includes a three-phase validation roadmap: (1) simulation in MuJoCo/PyBullet, (2) hardware prototype development, and (3) comparative evaluation against state-of-the-art platforms. This work provides a mechanistically grounded alternative to surface-level biomimicry in robotics, aiming to substantially extend operational autonomy, improve perturbation robustness, and enable more natural, human-like motion in humanoid systems.