interim report ss
TRANSCRIPT
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Sensor Networking and Data Fusion for Condition
Monitoring: A Hands-On Exploration
Interim Progress
The first few weeks went into defining the project objective and title. After having decided
on the project title, the first phase of the project was primarily focused on making high level
technology choices, purchasing equipment, setting up a test framework and defining the
conceptual design. The process that I am following in executing this project may be
described by the following flow diagram.
Figure 1. The Projects Process
The idea underpinning this project may be summarized as follows:
"To develop a modular and inexpensive condition monitoring system that can be easily
deployed in a wide variety of applications"
The key design goal is to be able to distribute sensor nodes on monitored sites (factory,
shipboard environment, home, farm animals etc.) and collect the data remotely for analysis
and fault diagnosis. I intend to use a combination of microcontroller, micro-sensor and ad-
hoc mesh networking technologies to achieve this goal. The architecture of the system may
be seen as a network of inexpensive communicative nodes distributed over objects of
interest in a monitored site. Each such node would have multiple sensors attached, and
would have capability to communicate the sensor readings to designated computer(s),
where purpose-designed software would be used to fuse the monitored data. This data
fusion process would give rise to a global situational awareness about the entire monitored
site. The conceptual design of each node is shown by the following diagram.
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Figure 2. Conceptual Model of a Monitoring Node
The first two conceptual designs I made are shown in Figures 3 and 4. Those could be used
for condition monitoring but these ideas had to be rejected due to cost concerns.
Figure 3. Conceptual Model Version 1 (the first iteration)
The cost per node for such systems would be very high thereby making a full deployment
prohibitively expensive. The problem is that the data acquisition card at the center is very
expensive and is not a programmable piece of hardware and comes with an unnecessary
USB interface. A single microcontroller with analog input pins would do just as good for a
much lower price. What we need for a minimalist and inexpensive design is a
microcontroller with a few analog pins (for the sensors) that has enough memory to host the
networking protocol stack and the sensor data buffering logic. A PIC or Atmel
microcontroller would be just fine. I made a choice in favour of PIC because I already had a
PIC programmer hardware from my 3rd year coursework project, and wanted to reuse it forreduce costs. However it turned out that the programmer did not support the larger
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microcontrollers from the PIC family (as was necessary for hosting the networking protocol
stack). So I bought another programmer that supported the PIC16F77 chips.
Figure 4. Conceptual Model Version 1 (the first iteration)
It was necessary to decide on a networking protocol stack. There are several proprietary and
open protocol solutions. On reading a number of online articles it seemed that going for an
open protocol stack was a better idea because that way there would be a wider base of
component suppliers to choose from. This would make better commercial sense because
commoditized components reduce the cost of large scale production. A proprietary protocol
stack (e.g. ANT+) would lead to vendor lock in (having to buy everything from the same
vendor). There are a few protocol implementations based on the open IEEE 805.15.4
standard (eg. Zigbee, WirelessHart, ISA 100.2), of which the Zigbee stack was chosen due to
its relatively widest supplier base and lower price per unit.
As per the current conceptual design, the communication architecture is shown in thefigures 5 and 6.
Figure 5. Message Hopping Communication in the Wireless Network
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Figure 6. Link between Zigbee modules and Computer
The Zigbee module has two digital I/O pins which would have to be connected to with two
digital I/O pins of the microcontroller. Figure 7 shows the connections to be made between
the Zigbee RF module and the microcontroller. The subsequent pictures (Figures 8, 9, 10
etc.) show the key hardware units acquired for the prototyping to be done during this
project.
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Figure 7. Connection between Zigbee Module and Microcontroller
Figure 8. Zigbee RF modules
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Figure 9. Microcontroller Programmer
Figure 10. Data acquisition card
Figure 8. Microcontrollers
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Figure 11. Acoustic, temperature, and vibration sensors
Figure 12. Microcontroller programmer from 3rd
year coursework
Work done so far include the following:
1. Experimental verification of sensor functioning (using the DAQ USBconnection).
2. Writing of a DLL that picks up data from a USB connection with the DAQ card. Thiswhen combined with a plotting software will serve as a poor mans (low frequency
handling) oscilloscope to inspect sensor signals.3. A detailed survey of technologies and applications of sensors.The following section presents the literature survey I have carried out.
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Literature Survey: The State of the Art in Sensor and Monitoring
Technologies
Sensors:
A sensor is a transducer that responds to a specific physical stimulus and produces a
measurable corresponding electrical signal. A sensor can be electrical, mechanical,
optical or electrochemical.
Energy
Recent advancement of microdevice technology, chemical processes,microfabrication, digital signal processing, etc. have enabled the development of
micro and nanosized low power and low cost microsensors. Microsensors are
applied successfully in many sectors including telecommunication, medical devices,
space equipments, manufacturing, military equipments, etc.
Microsystems are intelligent micro scale machines that combine sensors and
actuators, electronics and mechanical structures to sense information from the
environment and react to it.
MEMS + Electronics + Package Microsystem
Microsensors and Microsystems have certain advantages when compared with
traditional or conventional sensors in various respects.
Low cost Minimise energy and materials used in manufacturing Can be used in narrow spaces and harsh environments Faster devices Wider dynamic range Performance advantages Improved accuracy and reliability
Classification of sensors according to their working principle:
Sensing principle Sensors
Resistance change Potentiometer, thermistor, resistance temperature
detector(RTD), strain gauge, photo-resistive sensor,
piezo-resistive sensor
Inductance change Liner variable differential transformer(LVDT), inductive
angular position sensor, inductive torque meter
Capacitance change Capacitance level sensor, capacitive-type torque meter
Photo electric effect Phototransistor, photodiode, photo-interrupter(optical
encoder)Thermoelectric effect Thermocouple
Sensor Electrical SignalInput Output
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Piezoelectric effect Piezoelectric accelerometer, sound navigation and
ranging (SONAR)
Electromagnetic induction Electromagnetic flow meter
Hall effect Hall sensor
Table: 1
Temperature sensors:
Thermocouple
Thermocouple is a sensor for measuring temperature.
A thermocouple is created when two dissimilar
metals touch and the contact point produces a small
open-circuit voltage as a function of temperature.
This thermo-electric voltage is known as Seebeck
voltage. They are self-powered, low cost, simple,
rugged, available in a wide variety, has reasonably
short response time and has a wide temperature
range.
Limitations: They are least sensitive, least stable, non-
linear and reference is required.
Figure: Thermocouple
ThermistorThermistors are thermally sensitive resistors. They are
used in circuits which are temperature dependent.
For example in fire alarms. They typically work over a
relatively small temperature range, compared to
other temperature sensors, and can be very accurate
and precise within that range.
Limitations: These are fragile, non-linear, have limited
temperature range, self-heating and the current
source is required. Figure: Thermistor
Resistive Temperature Detector (RTD)
RTDs are temperature sensors that contain a resistor
which changes resistance value as its temperature
changes. Typical elements used for RTDs include
nickel (Ni) and copper (Cu), but platinum (Pt) is by far
the most common because of its wide temperature
range, accuracy, and stability. RTD has long-term
stability, very accurate and exhibit the most linear
signal with respect to temperature of any electronic
temperature sensor.
Temperature
Resistance
Vout (mV)
Temperature0C
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Limitations: These are expensive, low absolute
resistance, self-heating and the current source is
required.
Figure: RTD
I.C. Sensor
A silicon temperature sensor or an Integrated circuit
temperature sensor is an integrated circuit. It includes
extensive signal processing circuitry within the same
package as the sensor and comparator or ADCcircuits. It doesn't require designing cold-junction
compensation or linearization circuits for
temperature sensor ICs.
A temperature sensor IC can operate over the
nominal IC temperature range of -55C to +150C.
Some devices go beyond this range. These are most
linear and low cost.
Limitations: I.C. sensors are slow, self-heating,
requires power supply and has limited configurations.
Figure:
Radiation thermometers
Radiation Thermometers (Pyrometers) are non-
contact temperature sensors that measure
temperature from the amount of thermal
electromagnetic radiation received from a spot on the
object of measurement and relate this to its
temperature by means of the Planck law of radiation.These devices enable improvements in processes,
maintenance, health and safety. They are used widely
in many manufacturing process. Figure:
Resistance temperature curve for a
100 Ohm Platinum RTD
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Micro and Nano sensors:Micro-electro-mechanical (MEMS) devices are an integration of micro-sensors,
analog-to-digital converters, signal-processing circuits, programmable memory and a
microprocessor. Modern MEMS contains an antenna for radio signal transmission.
Evolution of smart wireless micro-sensors (Crossbow Technology Inc.)
A wireless micro-sensor
is the integration of a
sensing unit, a
processing unit a power
unit and a
communication unit.
The signal processing
functions are performed
in the processing unit.
The communication part
consists of a receiver, a
transmitter and an
amplifier. All individual
sensor nodes are
operated by a limited
battery power.
Figure: Wireless MEMS model
Nanosensors are used in chemical
and biological sensory
applications to communicate
information about nanoparticles.
For example nanotubes are used
to sense various properties of
gaseous molecules.
Three-dimensional model of
three types of single-walled
carbon nanotubes.
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Literature Survey: The State of Monitoring Technologies in Healthcare
Human body temperature monitoring:
Accurate measurement of the human body's internal temperature is essential in many areas
of healthcare - from cancer treatments, fever screening, monitoring premature babies, to
heart attack or stroke treatments. The traditional approach to temperature monitoring is
through a manual process which often results in unreliable records and paper trails due to
the "human element".
Temperature Sensors:
Vital Sense Monitor:The monitor stores and display core and dermal
temperature data as well as heart rate of up to 10
sensors. Sensors are wireless transmitters and are pre-
calibrated at the factory to simplify activation and
eliminate data entry errors. Vital Sense can provide
multi-day 24 hour monitoring and data logging without
wires or probes.
After sensor activation, each sensor transmits its first
value to the monitor within 15 seconds and then takes
another reading every 15 seconds. The subject must
wear the monitor in order for data to be received. In
Medic mode, the monitor will detect and collect signals
from any sensor in its range. In Medic Mode, data is time
stamped as it is collected.
Human Temperature Monitoring
Device, Bio-Lynx Scientific Equipment
inc.
Jonah Temperature Capsule:Ingestible core body temperature capsule transmitswirelessly to monitor every 15 seconds. The capsule, the
size of a large gel capsule, is swallowed with liquid,
travels and passes through the GI tact within 12 to 24
hours without affecting other bodily functions.
Human Temperature Monitoring
Device, Bio-Lynx Scientific Equipment
inc.
DataTherm Veterinary Temperature Monitor:The DataTherm Vet continuously monitors a patients
body temperature and features a real time temperature
display, updated every 4 seconds. A range of 62.6F to
113F temperatures makes it applicable for most speciesincluding exotics. Features include; programmable high
and low alarms, dual scale Fahrenheit or Celsius,
memory recall for up to 70 readings, and flexible 2mm
diameter x one meter long rectal probe with 25 covers(
core temp). Weighing less than 2 ounces and battery
operated, it is lightweight, portable and easy to use.
Ideal for surgery, recovery, and intensive care.DataTherm Veterinary Temperature
Monitor, Paragon Medical
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Pressure Sensors:
NPC-100 Pressure Sensor:NovaSensors NPC-100 pressure sensor is specifically
designed for use in disposable medical applications.
The device is compensated and calibrated per the
Association for the Advancement of MedicalInstrumentation (AAMI) guidelines for industry
acceptability. The sensor integrates a high-
performance, pressure sensor die with temperature
compensation circuitry and gel protection in a small,
low-cost package.
NPC-100 Pressure Sensor, GE
Sensing and Inspection
Technologies
Intra-uterine Pressure Sensor:Silicon MEMS-based pressure sensors are used in
intrauterine pressure (IUP) sensors to measure
contraction pressure and frequency during childbirth.
This method is more reliable than conventional belts
and is used in critical cases. Additional features can bebuilt into these sensors such as amnion fluid infusion
and extraction. These sensors are inserted through the
uterus and reside in the amnion sack.Intra-uterine Pressure Sensor,
Measurement Specialties, Inc.
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ECG:
The electrocardiogram, or ECG / EKG are
a surface measurement of the electrical
potential generated by electrical activity
in cardiac tissue. Current flow, in theform of ions, signals contraction of
cardiac muscle fibres leading to the
heart's pumping action. The ECG records
the electrical activity that results when
the heart muscle cells in the atria and
ventricles contract. Interpretation of
these details allows diagnosis of a wide
range of heart conditions. These
conditions can vary from minor to life
threatening.
ECG Sensors:
Vital Sense XHR Sensor:The Vital Sense XHR Sensor is an innovative, rechargable,
compact device that wirelessly transmits Heart rate and
respiration rate to the VitalSense monitor. This chest-worn
wireless physiological monitor incorporates an ECG-signal
processor reporting average heart and respiration rate
every 15 seconds to the VitalSense Monitor.
Vital Sense XHR Sensor, Bio-Lynx
Scientific Equipment inc.
Thought Technology ECG/EKG Sensor (SA9306M):
The Thought Technology pre-amplified electrocardiograph
(ECG/EKG) sensor (T9306M) for the Procomp Infiniti
Systems or Procomp+. Used for directly measuring
electrical activity of the heart. The T9306M EKG Sensor
connects via extender cables for a single channel hook up.
Operating Principle:
Use the Sensor Extender Cable (TTL T8720M). The surface
electrodes monitor electrical activity from the heart
muscle. Place the active electrodes along the central axis
of the heart and the reference electrode on the opposite
side of the chest.
Thought Technology ECG/EKG
Sensor (SA9306M)
Condition Monitoring in Maritime Sector
Safety and performance are the top concerns in a cruise ship. Fault monitoring and
failure prevention of the machineries are thus essential in a cruise ship operation.
Preventive maintenance and predictive maintenance also known as condition
monitoring of the machines are thus considered to be very important in determining
the state of the ship engine room machines.
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Maintenance management methods:
Reactive maintenance:Reactive maintenance is the run till failure maintenance mode. This
method is very expensive. It has increased labour cost as it is very
likely to be associated with overtime payments. It also has increased
cost due to unplanned downtime of equipment. It is often involved
with costly possible secondary equipment or process damage from
the failure of the equipment.
Preventative maintenance:Preventive maintenance is a schedule of planned maintenance actions
aimed at the prevention of breakdowns and failures. The primary goal
of preventive maintenance is to prevent the failure of equipment
before it actually occurs. Time based maintenance is not totally
effective when the time to failure of the part cannot be determined
accurately.
Predictive maintenance:Predictive maintenance or condition monitoring is the process of
monitoring equipment as it operates. The main issue is to identify a
suitable parameter which can be used to reliably predict the failure.
Nearly 25% of casualties at sea caused by machinery failure. Land based industries
claim up to 40% savings when switching from planned to predictive maintenance.