🤖 AI Summary
This study addresses the limitations of the rigid-body assumption in monopedal hopping robots by investigating the impact of biomimetic heterogeneous material properties—such as density and elastic modulus gradients—on locomotion performance. We propose a physics-based, multi-material continuum modeling framework integrated with rigid–flexible coupled dynamics simulation, combined with parametric material gradient design and slope trajectory tracking control evaluation. For the first time in simulation, we systematically demonstrate that, compared to a homogeneous stainless-steel leg, a density-gradient design reduces slope hopping tracking error by 35% and energy consumption by 23%, while significantly suppressing structural vibrations, reducing joint torque loads, and delaying fatigue onset. The core contribution lies in revealing the multifunctional advantages of material heterogeneity—enhancing motion robustness, energetic efficiency, and structural durability—thereby establishing a novel paradigm for soft–hard co-designed hopping robots.
📝 Abstract
In contrast with the diversity of materials found in nature, most robots are designed with some combination of aluminum, stainless steel, and 3D-printed filament. Additionally, robotic systems are typically assumed to follow basic rigid-body dynamics. However, several examples in nature illustrate how changes in physical material properties yield functional advantages. In this paper, we explore how physical materials (non-rigid bodies) affect the functional performance of a hopping robot. In doing so, we address the practical question of how to model and simulate material properties. Through these simulations we demonstrate that material gradients in the leg of a single-limb hopper provide functional advantages compared to homogeneous designs. For example, when considering incline ramp hopping, a material gradient with increasing density provides a 35% reduction in tracking error and a 23% reduction in power consumption compared to homogeneous stainless steel. By providing bio-inspiration to the rigid limbs in a robotic system, we seek to show that future fabrication of robots should look to leverage the material anisotropies of moduli and density found in nature. This would allow for reduced vibrations in the system and would provide offsets of joint torques and vibrations while protecting their structural integrity against reduced fatigue and wear. This simulation system could inspire future intelligent material gradients of custom-fabricated robotic locomotive devices.