Lower-limb motion monitoring is highly desired in various application scenarios ranging from rehabilitation to sports training. However, there still lacks a cost-effective, energy-saving, and computational complexity-reducing solution for this specific demand. Here, a motion capturing and energy harvesting hybridized lower-limb (MC-EH-HL) system with 3D printing is demonstrated. It enables low-frequency biomechanical energy harvesting with a sliding block-rail piezoelectric generator (S-PEG) and lower-limb motion sensing with a ratchet-based triboelectric nanogenerator (R-TENG). A unique S-PEG is proposed with particularly designed mechanical structures to convert lower-limb 3D motion into 1D linear sliding on the rail. On the one hand, high output power is achieved with the S-PEG working at a very low frequency, which realizes self-sustainable systems for wireless sensing under the Internet of Things framework. On the other hand, the R-TENG gives rise to digitalized triboelectric output, matching the rotation angles to the pulse numbers. Additional physical parameters can be estimated to enrich the sensory dimension. Accordingly, demonstrative rehabilitation, human-machine interfacing in virtual reality, and sports monitoring are presented. This developed hybridized system exhibits an economic and energy-efficient solution to support the need for lower-limb motion tracking in various scenarios, paving the way for self-sustainable multidimensional motion tracking systems in near future.

The nonlinear material metallic rubber is used widely in engineering, especially in isolation systems. This paper describes the effects of loading processes on dry friction damping performance, which is based on the Masing model and its derivations. First, the primary loading lines of the full hysteresis loop are obtained from single axial experiments. The lines are used to describe the full loop in the process of coordinate transform. Then, two-dimensional perpendicular loading experiments are conducted to investigate the relationship between axial loading and tangential loading. In the experiments, different loading amplitudes in axial and tangential directions are adopted to study their effects on the damping performance. Particular attention is paid to the description of the relationship between relative frictional force and the displacement in its perpendicular direction. In addition, a test rig is designed for the study.

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