Notations
$\left[d^t\right]$	Converse piezoelectric effect matrix
$\left[d\right]$	Direct piezoelectric effect matrix
$\Delta t$	Generation time
$\mathsf{\Theta }$	The effective piezoelectric coupling coefficient
$A$	Transducer’s area
$C$	Electrical capacitance
$D$	Displacement of charge density, electric displacement, C m−2
$E$	Electric field strength or intensity, N/C
$E_{\%}$	Mechanical-electrical energy conversion efficiency
$E_e$	Electrical energy
$E_m$	Mechanical energy
$F$	Applied force
$F_t$	The transduced force from electrical domain
$\mathrm{F}\left(\mathrm{t}\right)$	The excitation force
$K$	The effective stiffness
$L_j$	The distance between the electrodes
$M$	The effective mass
$P$	Output power
$P_{avg}$	The average output power
$P_{in}$	Mechanical input power
$P_{out}$	Electrical output power
$P_{res}$	Power density, W/m3
$R$	Resistive load
$S$	Strain
$T$	Stress, N/m2 (Pa)
$T_{pulse}$	The duration of the pulse
$V$	Output voltage
$V_{3j}$	The output circuit voltage when the input force is a bending stress
$Z_{max}$	Maximum displacement
$b$	damping
$d$	Movement distance or piezoelectric coefficient or piezoelectric charge constant
$d_{31}$	Piezoelectric constant
$d_{ij}$, $e_{ij}$, $g_{ij}$, $h_{ij}$	Piezoelectric coefficients
$f_{res}$	Resonance frequency
$g$	Piezoelectric voltage coefficient
$g_{3j}$	The piezoelectric voltage constant when the input force is a bending stress
$i_p$	The current through flowing through the piezoelectric transducer when the circuit is closed
$k$	stiffness
$m$	Inertial mass
$q_c$	Results from the voltage across the capacitor
$q_p$	Electrical charge
$q_t$	Coupled charge induced by the mechanical domain
$s$	Elastic compliance, 1/Pa
$s_{11}^E$	Elastic compliance
$t$	Transducer’s thickness
$t_1$, $t_2$	The start and the end of the pulse
$u\left(t\right)$	The transverse displacement of the traductor
$v$	The applied force’s speed
$v_h$	The electrical domain’s non-linearities
$v_p$	The overall voltage between piezoelectric transducer’s electrodes
$x$	Relative displacement
$y$	Amplitude of vibration of the housing
$\epsilon$	Permittivity, F/m
${\epsilon }_{33}^T/{\epsilon }_0$	Dielectric constant
${\epsilon }_0$	Permittivity in free space or vacuum dielectric constant (8.854 × 10−12 F/m)
${\epsilon }_{\mathrm{r}}$	The relative dielectric constant
$\eta$	The effective damping coefficient
${\eta }_C$	The convertor efficiency
$\rho$	Mass density
${\sigma }_{xx}$	The bending stress
Abbreviations
BaTiO3	Barium titanate
BNT	Bismuth Sodium Titanate
DCM	Discontinues Conduction Mode
EAP	Electrode polymer
IoT	Internet of Things
KNbO3	Potassium niobate
MEMS	Micro ElectroMechanical Systems
PLA	Polylactic acid
PMN	Lead magnesium niobite
PU	Polyurethane
PVDF	Polyvinylidene fluoride
PZT	Lead zirconate titanate
SECE	Synchronous Electrical Charge Extraction
SSHI	Synchronized Switch Harvesting on Inductor
TEG	Thermoelectric Generator
ZnO	Zinc oxide