Displacement
The deflection of a beam shaped monomorphic bending actuator, the d31
effect, which shortens the lateral dimension of the active layer if an electric
field is applied in the d33 direction of the polarization. As the active layer is bonded to a passive
layer, this causes bending of the device. More efficient designs, known as
bimorph, trimorph and multimorph bending actuators, can create bidirectional
deflection. By making use of two or more layered piezoelectric structures,
similar to piezoelectric multilayer stack actuators, the operating voltage of
the multimorph benders is significantly reduced by the small electrode distance
[52].
The movement across the temperature range with the reverse charge system
is more than 3 times that for a unipolar drive [31]. Re-poling of the ceramic
is successfully avoided. This is all accomplished without the use of a
temperature sensor or intermediate temperature values. [32]
In recent years there have been some significant advances in extending the
concepts of differential flatness and passivity based control to the
infinite-dimension. For applications with large displacements, range of input
voltage is available. However, at high electric field strengths, piezoelectric
material shows significant hysteretic.
Piezoelectric Trimorph-bending actuators consist of a substrate of metal
or carbon fibre and two metalised piezoceramic films [59]. They found that the
small structural damping the step-response of the uncontrolled bending actuator
has a large overshoot and a large settling time.
For actuation it is needed to know.
ReplyDelete