A scalable piezoelectric impulse-excited energy harvester for human body excitation

Abstract

Harvesting energy from low-frequency and non-harmonic excitations typical of human motion presents specific challenges. While resonant devices do have an advantage in environments where the excitation frequency is constant, and while they can make use of the entire proof mass travel range in the case of excitation amplitudes that are smaller than the internal displacement limit, they are not suitable for body applications since the frequencies are random and the amplitudes tend to be larger than the device size. In this paper a piezoelectric, impulse-excited approach is presented. A cylindrical proof mass actuates an array of piezoelectric bi-morph beams through magnetic attraction. After the initial excitation these transducers are left to vibrate at their natural frequency. This increases the operational frequency range as well as the electromechanical coupling. The principle of impulse excitation is discussed and a centimetre-scale functional model is introduced as a proof of concept. The obtained data show the influence of varying the frequency, acceleration and proof mass. Finally, a commercially available integrated circuit for voltage regulation is tested. At a frequency of 2 Hz and an acceleration of 2.7 m s−2 a maximal power output of 2.1 mW was achieved.

Design and development of a multipurpose piezoelectric energy harvester

“…The beam-roller PEH is similar to the scalable PEH reported in Ref. [17] in terms of the operating principle, but the former can avoid the torsional deformation of the beam when the beam stiffness is comparatively low or the beam width is comparatively large. Moreover, the scalable PEH is only designed to harvest energy from the travel of the roller, and then the collision between the roller and the proof mass caused by the z-directional vibration is not considered in the design.…”

“…Tang et al [16] proposed to replace the mechanical impact with repulsive magnetic force to convert the low-frequency vibration caused by wave heave motion to the high-frequency vibration of the piezoelectric cantilever beam. Pillatsch et al [17] developed a scalable PEH, in which a cylindrical proof mass driven by human motion was used to actuate an array of piezoelectric bimorph beams through magnetic coupling, and thus realized frequency up-conversion. Kwon et al [18] presented a design to convert the external low-frequency vibrations to the free vibrations of a piezoelectric cantilever beam via the magnetic attraction between the beam and a flexible substrate.…”

Design of a body energy harvesting system for the upper extremity

“…It was first simulated, then designed and evaluated. The generator was tested during different activities and the electrical power output is comparable to that of other energy harvesting systems for the upper extremities [6][7][8][9] and sufficient to provide e.g. a sensor based monitoring system [15].…”

“…However, most systems are designed to convert energy from motions of the lower extremities. Only a few systems have yet been presented to explicitly convert energy from movements of the upper extremity [6][7][8][9]. The only commercialized technology can be found in automatic wrist watches [10].…”

Piezoelectric energy harvester converting strain energy into kinetic energy for extremely low frequency operation

“…7 For low-frequency operation, several methods have been studied. Impact-type 8-10 and non-impact-type [11][12][13] frequency up-conversion techniques were proposed to convert a low-frequency input into a high-frequency input to a harvester with a high resonant frequency. In addition, a bistable harvester 14 and a shell-structured harvester 15 were introduced for low-frequency operation.…”