global positioning system integrated with an inertial navigation system
DESCRIPTION
Global Positioning System Integrated with an Inertial Navigation System. Michael Bekkala Michael Blair Michael Carpenter Matthew Guibord Abhinav Parvataneni Dr. Shanker Balasubramaniam. Inertial Navigation System. The use of inertial measurements in navigation - PowerPoint PPT PresentationTRANSCRIPT
Global Positioning System Integrated with an Inertial Navigation System
Michael BekkalaMichael Blair
Michael CarpenterMatthew Guibord
Abhinav ParvataneniDr. Shanker Balasubramaniam
Inertial Navigation System The use of inertial measurements in
navigation Measurements come from inertial
sensors such as:• Accelerometers• Gyroscopes
Very accurate over short term Errors integrate with time
Physics of Accelerometers/Gyroscopes
Accelerometers• Measure acceleration in x, y, z
directions• Types:
MechanicalMicro Electromechanical (MEMS)
• Capacitive• Piezoelectric
Mechanical Accelerometers
Mass suspended in a case by a pair of springs
Acceleration along the axis of the springs displaces the mass.
This displacement is proportional to the applied acceleration
Picture from “Basic Inertial Navigation” by Sherryl Stoval
Capacitive Accelerometers Sense a change in capacitance with respect
to acceleration Diaphragm acts as a mass that undergoes
flexure Two fixed plates sandwich diaphragm,
creating two capacitors Change in capacitance by altering distance between
two plates http://www.sensorland.com/HowPage011.html
Piezoelectric Accelerometers Commonly uses 1 crystal
made of quartz Force exerted by acceleration changes electrostatic force Low output signal and high
output impedance requiresthe use of amplifiers
Picture from Wikipedia.org
Physics of Accelerometers/Gyroscopes
Gyroscopes• Measure Angular velocity in yaw,
pitch, and roll directionsMicro Electromechanical (MEMS)Optical
Micro Electromechanical Gyroscopes
• Coriolis effect• Vibrating elements measure
Coriolis effect (vibrations on sense axis)
• When rotated, 2nd vibration on the drive axis• Angular Velocity
Picture from http://www.howyourelectronicswork.com/2008/09/fiber-optic-gyroscopes.html
Optical Gyroscopes
Sends out two beams of light Sensor can detect interference in the light
beam Very accurate No inherent drift Expensive
Navigation Equations Accelerations and angular velocities
are measured in the body coordinate frame
Need a constant reference for navigation
Rotation from bodyframe to North, East,Down frame gives areference.
Picture from “Accuracy and Improvement of Low Cost INS/GPS for Land Applications” by Shin
Inertial Navigation System
Diagram from Basic Inertial Navigation by Sherryl Stovall
System View of INS Equations
Navigation Equations The navigation equations can be
represented as (Shin, 2001):
100
0cos)(
10
00)(
1
)()2(
1
1
hR
hR
D
CgvfC
vD
Cvr
e
e
bin
bib
nb
nnnen
nie
bnb
n
nb
n
n
Navigation Equations BodyNED
RollPitchθYawψ
cossin0sincos0001
cosθ0sinθ010sinθ0cosθ
1000cosψsinψ0sinψcosψ
CNB
Navigation Equations GPS and INS need to be in the same
reference frame for proper measurements.
GPS data is in Earth Centered Earth Fixed (ECEF)
INS data is in Body frameand has to be translated to the North-East-Down frame
BodyNED, ECEFNEDPicture from “Accuracy and Improvement of Low Cost INS/GPS for Land Applications” by Shin
Integration of GPS and INS Different integration levels:
• Loosely Coupled Corrects errors in the IMU and INS Does not correct GPS
• Tightly Coupled Corrects both INS and GPS errors
Kalman filtering integrates both systems to achieve a more accurate overall system
GPS/INS Integration
Diagram from http://inderscience.metapress.com/media/59dam5dyxldjpg54uc5v/contributions/8/3/w/2/83w217t06m878447.pdf
System View of Integration