A closed-loop wide-range tunable mechanical resonator for energy harvesting systems

Abstract

This paper presents a novel electrically tunable structure which can be used as a resonator for vibration-based energy harvesters. The adjustment of the resonance frequency is provided by mechanical stiffening of the structure using piezoelectric actuators. This concept can easily be stand-alone integrated to realize an autonomous, tunable harvester. The resonator was simulated using ANSYS to find the optimum operation point concerning tuning range. The scalability of this tuning concept is also investigated in this work. A phase shift control circuit was developed for very efficient autonomous closed-loop control of the resonance frequency. Prototypes of the resonators were fabricated and measured with and without the control circuit. The tuning voltage can be kept as low as ±5 V leading to a measured resonance shift of ±15% for the larger resonator (40 mm) and around ±8% for the smaller resonator (27 mm). This tuning range can be simply enhanced by increasing the tuning voltage.

Toward Broadband Vibration-based Energy Harvesting

“…The continuous power required by the microcontroller system was in μW level. Peters et al (2009) proposed another novel tunable resonator whose mechanical stiffness and hence the resonance can be adjusted through two piezoelectric actuators. The free actuator swings around the axis of rotation with a deflection angle α, as shown in Figure 23(a).…”

A Novel Tunable Multi-Frequency Hybrid Vibration Energy Harvester Using Piezoelectric and Electromagnetic Conversion Mechanisms

“…These solutions include generator array [10][11][12], mechanical impact [13,14], nonlinear spring stiffness [15,16], magnetic coupling [17][18][19][20], hybrid conversion mechanism [21,22] and active/passive tuning techniques [23][24][25]. However, these generators are only effective in a continuous frequency range or at a single dominant resonant frequency.…”

Strategies for Wideband Mechanical Energy Harvester

“…For the present approach, the electromechanical coupling has a significant effect on the resonant frequency tuning ratio as shown by the equation (14). It is better to choose a material with a high electromechanical coupling.…”

“…The application of a force means that the VEH is equipped with an actuator, magnetic [13], piezoelectric [14] or electrostatic actuator [15]. The main task of this actuator is to apply an additional force on the seismic mass in the same direction as the vibration one in order to affect the mechanical stiffness of the VEH (added or substituted a force to the spring force of the resonator).…”