Recent advances in the development of ultra-low power electric devices have drawn attention to the study of wind power generation flags based on piezoelectric elements. However, the piezoelectric film wind power generation method has been a challenge to improve power generation density and durability. Therefore, a new piezoelectric cylindrical shell wind power generation flag had been proposed by the authors as a flexible and durable power generation structure that utilizes vortex excitation vibrations. Preliminary experiments showed that it was expected to generate more than 10 times power than the conventional planar-shaped wind power generation flag. It is also shown through theoretical considerations that in order to construct a cylindrical generator flag using piezoelectric film that increased power generation in the low wind speed region, it was necessary to excite the vibration mode of circumferential wavenumber n=2 in order to utilize Kalman vortex excitation in this wind region. Moreover, in order to make the conventional structure, which generates power at high wind speeds, resonate at lower wind speeds, the radius of the cylinder must be large when the thickness was fixed and the thickness must be thin when the radius was fixed. However, the effect of variation of size on power generation characteristics has not been verified experimentally. In this report, wind energy harvesting experiments were performed with a number of flexible cylindrical shell type piezoelectric harvester flags, which has different dimensions and also thickness/radius ratios, and the structural design method to construct superior energy harvesting shell type generator, which will be able to generate large power at low wind speed, was discussed.
In recent years, wind energy harvesting systems using piezoelectric materials have been studied by a lot of researchers. However, energy harvesting methods using flexible thin piezoelectric wind energy harvesting method using high-polymer films was investigated experimentally. At first, the feasibility of the systems was shown in laboratory experiment by using various shapes, sizes, and boundary conditions of piezoelectric films subjected to the artificial wind airflow from consumer air blower. Then, a flag-type piezoelectric wind energy harvester was manufactured and the characteristic against natural winds was verified by outdoor experiments.
In order to overcome the difficulties of multimodal active vibration
damping of the flexible thin structure using simultaneous piezoelectric
sensing and actuation,
an noncollocated vibration control method, in which
piezoelectric film sensors and actuators were shaped using different shaping
functions, was proposed in this paper.
At first, fundamental equations were summarized and vibration responses of
the beam were derived based on the modal coordinate systems.
Then, it was shown that by considering phase characteristics of the
controller in conjunctions with the polarity of the piezofims in high
order modal frequencies, multimodal control will be implemented both
theoretically and experimentally.
Using direct and inverse piezoelectric effects of high-polymer piezoelectric films simultaneously, flexible structures
are expected to be realized which possess vibration damping ability and are able to behave actively and
autonomously such as biological systems. However, conventional studies have been limited to either developing
high order controller in conjunction with sensor/actuator of basic shaping or developing sensor/actuator of
complicated shaping function in conjunction with simple controller. In this paper, a new shaping design method
of distributed piezoelectric film sensor/actuator for vibration control of flexible beams is proposed. At first,
fundamental equations are derived, and a new shaping method in which the shaping function is described by
the superposition of the modal strain functions is proposed. In the proposed method, the weighting coefficient
is determined by a reciprocal of the cube of wavenumber. It is proved that in the case of simply supported
beam, one example of the proposed shaping function is reduced to the conventional triangular shaping function.
Numerical examples of designed shaping function for a simply supported beam and a cantilever beam are shown
for single mode, multi mode and all mode sensor/actuator.
Using dirct and inverse piezoelectric effects of distributed piezoelectric films simultaneously, active flexible structures
which posess vibration damping ability can be able to construct. However, conventional studies are limited
to the control of relatively small (micron-order) displacements of thin flexible structures as well as numerical
studies by handling controller design of software aspects. In this paper, several fundamental active vibration
control principles, which will be valid in actual implementation, of smart flexible structures using piezoelectric
films as distributed sensor/actuator have been developed. By applying each of these methods, it was verified
that the enough vibration control effects were actually obtained and the theory agrees well with the experiment.