Piezoelectric Materials: Solutions to Questions

First Name Last Name
Instructor
Mechanical Engineering
23 March 2019
Piezoelectric Materials
Solutions to questions:
a. Part:
i. An open loop control refers to a kind of unremitting control system whereby
the output produces no effect on the input signal control mechanism. It is also
known as a non-feedback system. Therefore, in an open loop control there is
no measurement of the output or feedback for purposes of assessment with the
input. The input command remains activated regardless the set point or the
input command of the final outcome. An open loop control system has no
mechanisms for error corrections from instances such as preset value drifts
and deviations from the readings. Any variations in conditions as well as
disturbances are hardly mitigated by such a system as it is poorly equipped to
manage in such situations. This has a negative bearing on its ability to sustain
active tasks whenever such variations or disturbances occur. In fact, the
timing controller remains operative for as long as thirty minutes with internal
functioning already disconnected. This is due to the fact that it lacks feedback
mechanism to adjust accordingly.
ii. I would recommend piezoelectric actuators. Piezoelectric actuators have been
established to have been established to achieve optimum working blend of
moderate to high strain, little to moderate hysteresis, and resistance to stress
depoling (Damjanovic & Newnham 2012). Electro strictive actuators on the
other hand normally used in high frequency transducers have been found to
show some stress induced domain orientation properties that relied on the
operating temperature and the dive conditions. Electro strictive actuators
comprising of high lead titanate compositions are worse as these effects are
more amplified. In respects of all these, piezoelectric actuators would make a
more suitable choice compared to Electro strictive actuators.

iii. Yes, there is a criterion specified by the manufacturer (table 2a) have an
impact on the recommendation in (ii) above.
 Operating temperature range: Electro strictive actuators show less
hysteresis than Piezo actuators, in a restricted temperature go.
Notwithstanding of the diminished hysteresis, they give very nonlinear
movement as a result of the quadratic connection among voltage and
displacement. Additionally, they can't be utilized in a bipolar mode with
decreased electric field quality (switching the electric field does not result
in withdrawal).
 Drive voltage range: Piezoelectric actuators demonstrate an electrical
capacitance four to multiple times as high as piezo actuators requiring
altogether higher driving flows for dynamic applications.
b. For current application I would use series connection. Based on this, which
actuator configurations such as C1p, C2p, C3p, and C4p should be eliminated from
further consideration. Parallel connection will in general keep running at the
equivalent no-heap speed, which will tumble off to some degree with connected
torque; series wiring connection will create a uniform torque, which will tumble off
for all actuators in the arrangement dependent on the aggregate speed of the actuators.
At any minute in time, the rotational speed of the engine will be straightforwardly
relative to the voltage over the "perfect" some portion of the actuator motors, and the
torque on the engine will correspond to the current ("The selection of mechanical
actuators based on performance ..." 2017). These are both bidirectional connections,
so changing the speed will change the voltage and vice versa.
When the actuators are physically connected to such an extent that they will keep
running at a similar speed, wiring them in series will adjust the torque on them. In the
event that they are not associated that way physically but rather should keep running
close to a similar speed, wiring them in parallel will make them do as such, however
in the event that they exposed to contrasting measures of torque that may make the
rotational velocities vary to some degree (Cho, Yang, & Kwon 2010).
c. Based on technique for order preference by similarity to ideal solution (TOPSIS), I
would eliminate piezoelectric 1 designated M1. Young’s modulus identifies materials
2

ability to accommodate linear changes when under compression, and/ or tension.
Based on this consideration, M2 is preferable to M1. M2 has a Young’s modulus of
62GPa while M1 has a Young’s modulus of 83 GPa making M2 more suited as it has
more capacity to accommodate changes in length. Changes in length under loading
shares a direct relation with stress buildup within the material hence when not
properly considered, a material can get ton or deformed hindering its performance.
The ability of the material to accommodate changes in length hence means less strain
resulting and hence the impacts on the material ("Design choices: MEMS actuators -
Free Online Course Materials" 2018).
Based on respective relative permittivity property of the two materials, M1 and M2,
M2 is again a more ideal option. M2 has a relative permittivity value of 3800 with
M2 only having 12. Relative permittivity also known as dielectric constant is a ratio
of absolute permittivity to the permittivity in free space.
Piezoelectric coefficient is an indicator of change in volume when a piezoelectric
material is placed in an electric field (Davim 2017). The lower the value of the
piezoelectric coefficient, the better the piezoelectric material. In that regard, M2 has a
piezoelectric coefficient of 630×10^-12 m/V while M1’s piezoelectric coefficient is
43×10^-12 m/V hence M2 is a better alternative.
The materials dielectric strength relates to the maximum electric field which a given
material can endure under ideal conditions without failure. Materials with higher
dielectric strength properties are better insulating material. M1 has a dielectric
strength of 2×10^8 V/m compared to M2’s of 1×10^8 V/m. this means M1 is not
suited as it records the highest insulating properties, twice as much as M2.
Considering the last property, that is curie point, M1 is a favorable alternative over
M2. Curie point is the temperature beyond which certain materials lose their
permanent magnetic properties, to be substituted by induced magnetism. For M1 this
value is at 110 degree Celsius while for M2 the value s at 250 degree Celsius. This
simply means that M2 takes longer to lose its magnetism than M1 hence takes longer
to fit in the electric field and limit resistance from magnetic properties. This makes it
less ideal but stable.
(Going by the above considerations, M1 is hence eliminated, M2 chosen)
3