Cantilevered piezoelectric harvesters have been extensively considered in the energy harvesting literature.
Mostly, a traditional cantilevered beam with one or more piezoceramic layers is located on a vibrating host
structure. Motion of the host structure results in vibrations of the harvester beam and that yields an alternating
voltage output. As an alternative to classical cantilevered beams, this paper presents a novel harvesting device;
a flexible L-shaped beam-mass structure that can be tuned to have a two-to-one internal resonance to a primary
resonance ω<sub>2</sub> ≅ 2ω<sub>1</sub> which is not possible for classical cantilevers). The L-shaped structure has been well
investigated in the literature of nonlinear dynamics since the two-to-one internal resonance, along with the
consideration of quadratic nonlinearities, may yield modal energy exchange (for excitation frequency ω≅ ω<sub>1</sub>or the so-called saturation phenomenon (for ω≅ω<sub>2</sub>). As a part of our ongoing research on piezoelectric
energy harvesting, we are investigating the possibility of improving the electrical outputs in energy harvesting
by employing these features of the L-shaped structure. This paper aims to introduce the idea, describes the
important features of the L-shaped harvester configuration and develops a linear distributed parameter model
for predicting the electromechanically coupled response. In addition, this work proposes a direct application
of the L-shaped piezoelectric energy harvester configuration for use as landing gears in unmanned air vehicle
A switching sliding mode controller for the static shape control of a membrane strip is considered. The membrane
strip is augmented with two macro fiber composite (MFC) bimorphs. MFC patches are modeled as monolithic
piezoceramics. The combined structure is modeled as an
Euler-Bernoulli beam under tensile load. The two
bimorphs are actuated independently. One bimorph operates in bending, whereas the other bimorph operates
in tension. The presence of the later causes the system to be nonlinear, hence the use of the sliding mode
technique, and gives rise to a structural singularity. To evade this problem, a switching command is introduced.
Hence, the closed loop system utilizes a hybrid control law, which can cause stability problems. Fortunately, the
same Lyapunov function can be used to analyze the stability of both subsystems. Consequently, the switching
is safe, and asymptotic stability is guaranteed. Simulation results are presented to demonstrate the efficacy of
the switching slide mode controller.