x	the displacement of the actuator
S 3	the strain of the piezoelectric stack
T 3	stress
d 33	piezoelectric constant
E 3	external electric field
$S_{33}^E$	short circuit elastic compliance coefficient with constant electric field
h	the thickness of a single piezoelectric ceramic sheet
n	the number of layers of piezoelectric laminated ceramics
l	the length of the piezoelectric ceramic sheet
b	the width of the piezoelectric ceramic sheet
F out	the direction output force of piezoelectric stack
ua	the drive voltage of the piezoelectric stack
kamp	series circuit of gain
R	resistance
Ca	capacitors
uc	the output voltage of driving amplifier
q	the charge produced by quartz
A	the area of the piezoelectric quartz
εr	the relative permittivity of quartz
ε 0	the dielectric constant of air
m	the equivalent mass of moving part of piezoelectric sensor-actuator system
cf	the equivalent viscosity coefficient of actuator structure
kf	the stiffness coefficient of actuator
ka	the equivalent stiffness of preload