人体运动驱动压电式俘能系统的关键技术及动力学特性研究

Harvesting energy from the human motion has been considered as a promising method for powering portable devices. The human motion involves diverse mechanical motions, various directions of motions, and low-frequency motions. To accommodate to this complex scenario, we develop a novel technology to achieve energy harvesting from the human motion based on the piezoelectric conversion in this proposal. This technology, which is capable of realizing frequency up-conversion, employs two substructures coupled by magnets to sense different motions coming from various directions. The motion characteristics of human's four limbs will be investigated, and mathematical models will be established to describe the motions of the four limbs. A dynamic model of two magnetically coupled piezoelectric cantilever beams will be developed to reveal the interaction between the two beams and the mechanism through which energy can be exchanged. A dynamic model of two magnetically coupled substructures will be proposed to reveal the interaction between the two substructures and the mechanism through which energy can be exchanged. A dynamic model governing the piezoelectric energy harvester (PEH) excited by human motion will be established to examine the performance of the harvester when excited by multiple directions of sway motion, mechanical vibration, and compressive force. The conditions for various actuations to be reciprocal will be obtained and the guide will be acquired for designing PEHs actuated by human motion. On the basis of a series of experiments and theoretical studies, a set of design theory of piezoelectric energy harvesting system excited by human motion will be produced. The achievements made in this proposal are highly significant for meeting the energy demand of portable devices and implementing self-powered portable devices.

从人体运动中收集能量被认为是解决便携式器件能源问题的有效途径。针对人体运动存在的运动形式多样、方向多变、频率低等特点，本项目提出一种人体运动驱动压电式俘能新技术，通过两级结构的耦合感知不同形式和不同方向的运动，并具备频率提升功能。项目主要研究人体四肢的运动特点，建立四肢运动的数学表征模型；建立磁耦合双压电悬臂梁系统的动力学模型，揭示双梁之间的相互激励机制和能量传输机理；建立两级结构的耦合动力学模型，揭示两级结构间的相互作用机制和能量传输机理；建立人体运动驱动压电式俘能器动力学模型，研究俘能器在人体不同部位多方向振动、摆动、压力等联合激励下的性能，揭示不同运动激励相互增强的约束条件，获得人体运动驱动压电式俘能器的设计规律；最后，在系列实验和理论研究的基础上，获得整套人体运动驱动压电式俘能系统的设计理论和方法。本项目的研究成功，将对满足便携式器件的能源需求、实现自供电便携式器件意义重大。

随着微电子和微制造技术的不断进步，各种便携、可穿戴、健康监测器件的数量急剧增长，亟需一种可再生、长续航、环境危害小的供电技术以满足这些数量巨大的电子器件的能量需求。考虑到人体运动中蕴含着丰富的生物机械能，因而收集利用各种人体运动能，并将其转化为电能的压电式俘能器成为一种潜在可行的供能方案。但是，目前主流的压电式俘能器存在工作频率高、频带窄、无法满足各种便携/可穿戴电子能量需求的缺点。针对这一问题，本项目首先研究了人体躯干、四肢、足部的运动形式，获得了人体运动加速度和对地面压力的变化规律。提出了一种单稳态非线性压电式俘能器，通过调整压电梁末端磁铁与两侧固定磁铁的间距，不但可大幅降低俘能器的工作频率、扩展俘能的工作带宽，而且可提高输出功率，有效解决了主流压电式俘能器工作频率高，无法收集低频人体运动能的瓶颈问题。提出了两种两级结构、具备频率提升功能和多向能量收集能力的压电式俘能器，第一种频率提升式俘能器通过小球感知超低频激励，并通过机械碰撞驱动压电梁产生高频振动；第二种频率提升式俘能器通过可滑动的磁铁感知超低频激励，并通过磁力驱动压电梁产生高频振动；两种俘能器在手部摇摆下均可驱动30多个LED发光。提出了一种全新的梁驱式转子，可将悬臂梁的振动转换为转子的高速旋转运动，将输出功率提升了6倍。提出了一种全新的绳驱转子，通过两根线绳将人体的超低频运动转换为转子的高速旋转运动，在手部驱动下可产生6.5mW的电能，穿戴于人体可直接驱动多种商用电子器件正常工作。本项目的研究成果对于解决各种便携/可穿戴电子的长续航供电问题具有重要的促进作用，并对各种低频振动、摆动、波浪能的俘能器的研制具有指导和借鉴价值。