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Digital archive of theses discussed at the University of Pisa


Thesis etd-01122014-165816

Thesis type
Tesi di dottorato di ricerca
Thesis title
Inertial MEMS: readout, test and application
Academic discipline
Course of study
tutor Prof. Fanucci, Luca
tutor Prof. Roncella, Roberto
  • accelerometer
  • gyroscope
  • intertial
  • mems
  • readout
  • sensor
  • test
Graduation session start date
This thesis moves towards the investigation of Micro Electro-Mechanical Systems
(MEMS) intertial sensors from different perspectives and points of view: readout,
test and application.
Chapter 1 deals with the state-of-the-art for the interfaces usually employed for 3-
axes micromachined gyroscopes. Several architecture based on multiplexing schemes
in order to extremely simplify the analog front-end which can be based on a single
charge amplifier are analysed and compared. A novel solution that experiments an
innovative readout technique based on a special analog-Code Division Multiplexing
Access (CDMA) is presented; this architecture can reach a considerable reduction of
the Analog Front-End (AFE) with reference to other multiplexing schemes. Many
family codes have been considered in order to find the best trade-off between
performance and complexity. System-level simulations prove the effectiveness of
this technique in processing all the required signals. A case study is also analysed: a
comparison with the SD740 micro-machined integrated inertial module with tri-axial
gyroscope by SensorDynamics AG is provided.
MEMS accelerometers are widely used in the automotive and aeronautics fields
and are becoming extremely popular in a wide range of consumer electronics
products. The cost of testing is a major one within the manufacturing process,
because MEMS accelerometer characterization requires a series of tests that include
physical stimuli. The calibration and the functional testing are the most challenging
and a wide selection of Automatic Test Equipments (ATEs) is available on the
market for this purpose; those equipments provide a full characterization of the
Device Under Test (DUT), from low-g to high-g levels, even over temperature.
Chapter 2 presents a novel solution that experiments an innovative procedure to
perform a characterization at medium-g levels. The presented approach can be
applied to low-cost ATEs obtaining challenging results. The procedure is deeply investigated and an experimental setup is described. A case study is also analysed:
some already trimmed Three Degrees of Freedom (3DoF)-Inertial Measurement
Unit (IMU) modules (three-axes accelerometer integrated with a mixed signal ASIC),
from SensorDynamics AG are tested with the experimental setup and analysed, for
the first time, at medium-g levels.
Standard preprocessing techniques for removing the ground response from vehicle-
mounted Ground Penetrating Radar (GPR) data may fail when used on rough
terrain. In Chapter 3, a Laser Imaging Detection and Ranging (LIDAR) system
and a Global Positioning System (GPS)/IMU is integrated into a prototype system
with the GPR and provided high-resolution measurements of the ground surface.
Two modifications to preprocessing were proposed for mitigating the ground bounce
based on the available LIDAR data. An experiment is carried out on a set of
GPR/LIDAR data collected with the integrated prototype vehicle over lanes with
artificially rough terrain, consisting of targets buried under or near mounds, ruts
and potholes. A stabilization technique for multi-element vehicle-mounted GPR is
also presented.