system on chip for micro vibration measurement
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SYSTEM ON CHIP FOR MICRO-VIBRATION MEASUREMENT. Prepared by: Tarun Mishra Department of Electrical and Computer Engineering Utah State University Email: [email protected] Ph No: 510-364-9864. OUTLINE. Introduction Bi-Morph Sensor Basic Design and Structure

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system on chip for micro vibration measurement


Prepared by:

Tarun Mishra

Department of Electrical and Computer Engineering

Utah State University

Email: [email protected]

Ph No: 510-364-9864

  • Introduction
  • Bi-Morph Sensor
  • Basic Design and Structure
  • Specifications & Results
  • Advantages
  • Limitations
  • Proposed System
  • Advances in precision micro-machining has led to an interest in micro-robotics.
  • Applications of micro-robotics range from micro-assembly, to biomedics (inner space), to land mine sweeping, to city water system analysis.
  • As with conventional robotics one of the biggest challenges is making robots that are mobile and can traverse a wide variety of terrain.
  • Furthermore, in micro-robotics there is the problem that as the robot gets smaller the terrain obstacles seem bigger.

A pebble is no problem for a six meter long HMV, but it is real challenge for a ten millimeter surveillance robot. Actuation systems for mobile micro-robotics must meet the following challenges:

  • Traverse terrain with obstacles bigger than robot
  • Low power/ high efficiency
  • Simple control
  • Withstand harsh environments
  • Simple mechanics for both scalability and ease of manufacturing
bi morph sensor
Bi-Morph Sensor
  • Piezoelectric crystal or element primarily responds to force -input.
  • Multiple forces can also be applied
  • To increase the charge sensitivity more than one element can be used to form a transducer system and such combinations are known as bimorphs.
bimorph continued
Bimorph Continued….

Abimorph actuator is composed of two thin panels of ceramic elements bonded together with a flexible metallic panel as it\'s central electrode. By wiring these two elements in such a way as to make one elongate and the other contract by applying voltage, inflection deviation occurs conforming to the waveform of the applied voltage.

basic designs of piezoelectric positioning elements
Basic Designs of Piezoelectric Positioning Elements
  • Bender Type Actuators A Piezo bimorph operates similarly to a bimetallic strip in a thermostat. When the ceramic is energized the metal substrate is deflected with a motion proportional to the applied volt-age. Bimorph actuators providing motion up to 1000 µm are available and greater travel range is possible. Apart from the classical strip form, bimorph disk actuators are available, where the center arches when a voltage is supplied.
two electrode and three electrode bimorph
Two Electrode and Three Electrode Bimorph
  • Instead of a Piezo/metal combination Piezo/Piezo combinations are possible where individual Piezo layers are operated in opposite mode (contraction/expansion).
  • Two basic versions are available: the two electrode bimorph (serial bimorph) and the three electrode bimorph (parallel bimorph).
two electrode bimorph serial bimorph
Two Electrode Bimorph (Serial Bimorph)
  • Here one of the two ceramic plates is always operated opposite to the direction of polarization.
  • To avoid depolarization, the maximum electric field is limited to few hundred volts per millimeter.
  • These type of actuator is widely used in accelerometers and force sensors.
three electrode bimorph parallel bimorph
Three Electrode Bimorph (Parallel Bimorph)
  • Here the two piezoelectric plates are of the same polarization directions and the actuator is driven by applying electrical field between surface electrodes and the bonding layer
bimorph structure
Bimorph Structure
  • Bimorphs are composed of two sheets of Piezo-electric electrodes securely glues together and there are two different ways to do so.
  • The first is to have electrodes on both sides of the sheets. Then the sheets are glued together with their poled directions in the same direction as seen below.  Equal but opposite electric fields are then applied to the two sheets.  One of the sheets shrinks in length and the other expands causing the bimorph to bend.
bimorph structure1
Bimorph Structure
  • The second way to create bimorphs is to put electrodes on just one side of the electrode sheet and glue them so that the poled directions are in the opposite direction. The electrodes are on the outer sides of the bimorph and the electric field is applied across the entire as seen below.
electric field across bimorph
Electric Field Across Bimorph
  • When an electric field is applied across a bimorph one of the electrode sheets expands while the other shrinks causing the bimorph to bend, below. In the picture the deflection of a bimorph is represented by the arrow.
  • The deflection distance can be measure to determine the performance of the bimorph. 
some results
Some Results
  • Some results are shown below for DC voltages
  • AC voltages produce different displacements than the DC, it depends what the frequency is. At resonance the AC deflection is more than double that of the DC
  • Video of bimorph under AC voltage at resonance (Fig.2)
  • For bimorph actuator specifications, we need to take into account the following parameters:
    • Maximum Displacement (mm/V)
    • Blocked Force (N)
    • Maximum Voltage (volts)
    • Stiffness (N/mm)
    • Resonance Frequency (Hz)
    • Capacitance (F)
    • Compliance
    • Response Time (ms)

There are other factors to be considered too along with this specifications like:

Young’s Modulus

Operating Temperature

Storage Temperature

Mechanical quality factor etc.

  • Microphone, acoustic pressure sensor, micro speaker, acoustic transducers, vibration measurement
  • MEMS piezoelectric sensors and actuators (numerous arbitrarily shaped structures on silicon substrate)
  • High performance and low cost parts in Audio system, communication system, multimedia system, hearing aid system
  • High sensitive and biomedical compatible acoustic and ultrasonic transducers
general advantages
General Advantages
  • Size miniaturization with extremely small weight
  • Little power consumption and no polarization voltage needed
  • Potentially low cost due to the batch processing and possibility of integrating microphones and circuits on a single chip
unique advantages
Unique Advantages
  • Easier control of the neutral plane position than a uni-morph structure and effective conversion of mechanical strain into electrical voltage and vice versa
  • Simple structure containing only piezoelectric film, electrodes and very flexible parylene (does not introduce any significant stiffness in the diaphragm, nor residual stress);
  • With larger sensitivity and signal/noise ratio and higher fundamental resonant frequency, it has inherently higher figure of merit than a uni-morph device.
  • Conformal deposition allowing various diaphragm shapes

There are three major limitations to the bimorph piezoelectric actuator.

  • The shaping of the electrodes and laminate.
  • The bandwidth.
  • Blocking force.

The Shaping of the electrodes and laminate can be in several forms

  • C-shape
  • Bar, rectangular
  • Disk

Each shape will have a different response time and force when a specific voltage is applied.

limitations cont
Limitations (cont.)
  • Shaping can also effect bandwidth.
  • A larger laminar area will cause the bandwidth to drop. As the bandwidth drops the response time also drops.
  • This could either be an advantage or a disadvantage depending on the plant.
  • Blocking force is also determined by the deflection and compliance of the two laminar surfaces.
  • This ends up being inversely proportional to the length which indicates longer the lamina the less force it is able to exert.
mem system on chip
MEM System-On-Chip

A typical SoC consists of:

  • One microcontroller, microprocessor or DSP  core(s)
  • Memory blocks
  • Analog interfaces including ADCs and DACs
  • External interfaces including industry standards such as USB, FireWire, Ethernet, USART
  • Voltage regulators and power management circuits.
  • FPGAs contain programmable logic components called Configurable logic blocks (CLBs)
  • CLBs cab be configured to perform complex combinational functions
  • FPGA configuration is usually specified using any HDL
  • Costs between $10 ~10,000
  • Analog counter parts of FPGA
  • They are programmed using a bit-stream
  • various analog functions can be implemented using a set of configurable analog block (CAB) and programmable interconnect networks
  • Each CAB can implement a number of analog signal processing functions

As low vibration amplitude cannot be neglected in any design. With the help of some reconfigurable SoC, vibration estimation in the can be done easily. This system can be used for rapid adaptation to any function, guaranteeing both low cost and short design times.

  • A. M. Flynn, Piezoelectric Ultrasonic Micromotors, MIT PhD. Thesis, Thesis in Electrical Engineering and Computer Science, June 1995.
  • Craing L. Horn and Natarajan Shankar, "Modeling the Dynamic Behavior of Electrostrictive Actuators", SPIE Conference Procedings Vol. 3041, pp.268-280, 1997.
  • "Basis of Piezoelectric Positioning", Products for Microposionting Catalog, Physik Instrumente Co., 1995.