Scaramuzza - Sensors PDF
Scaramuzza - Sensors PDF
Scaramuzza - Sensors PDF
Introduction | perception
knowledge, mission
data base commands
Localization “position“ Cognition
Map Building global map Path Planning
environment model
path
local map
Information Path
Motion Control
Extraction Execution
Perception
see-think-act actuator
raw data
commands
Sensing Acting
Real World
Environment
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Perception | definition
Places / Situations
A specific room, a meeting situation, …
•Functional / Contextual
Servicing / Reasoning Relationships of Objects
• imposed
Objects • learned
Compressing Information
• spatial / temporal/semantic
Doors, Humans, Coke bottle, car , …
Navigation •Models
• imposed
Raw Data • learned
Vision, Laser, Sound, Smell, …
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Perception | challenges
Probabilistic Reasoning
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Laser scanners
Obstacle avoidance, motion estimation, scene
interpretation (road detection, pedestrians)
Cameras Wheel encoders
Texture information, motion estimation, scene
interpretation
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Classification of sensors
What:
Proprioceptive sensors
measure values internally to the system (robot),
e.g. motor speed, wheel load, heading of the robot, battery status
Exteroceptive sensors
information from the robots environment
distances to objects, intensity of the ambient light, extraction of features from the environment
How:
Passive sensors
Measure energy coming from the environment; very much influenced by the environment
Active sensors
emit their proper energy and measure the reaction
better performance, but some influence on environment
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Classification of sensors
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Uncertainty Representation
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Uncertainty Representation
The density function identifies for each possible 𝑥 value of 𝑋 a probability 𝑓(𝑥)
density along the 𝑦-axis
The area under the curve is 1, indicating
the complete chance of 𝑋 having some value
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x i = (i , i)
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Encoder | definition
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Heading sensors
Definition:
Heading sensors are sensors that determine the robot’s orientation and inclination with
respect to a given reference
Heading sensors can be proprioceptive (gyroscope, accelerometer) or
exteroceptive (compass, inclinometer).
Together with an appropriate velocity information, they allow integrating the
movement to a position estimate.
This procedure is called deduced reckoning (ship navigation)
Sensor types:
Compass: senses the absolute direction of the Earth magnetic field
Gyroscope: senses the relative orientation of the robot with respect to a given reference
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Gyroscopes
Mechanical gyroscopes
Angular momentum associated with a spinning wheel keeps
the axis of the gyroscope inertially stable.
No torque can be transmitted from the outer pivot to the wheel axis
however, friction in the axes generates drift
Quality: 0.1° drift in 6 hours (a high quality mech. gyro costs up to 100,000 $)
Optical Gyroscopes
Uses two monochromatic laser beams travelling in an optical fiber in two
opposite directions
The laser beam traveling in direction opposite to the rotation experiences
a slightly shorter path (Sagnac effect)
The phase shift of the two beams is proportional to the angular velocity
Half-silvered mirror
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MEMS accelerometer
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Range sensors
Sonar
Laser range finder
sonar Laser range finder
Time of flight camera
Structured light
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Structured light
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Major components
IR Projector
IR Camera
VGA Camera
Microphone Array
Motorized Tilt
RGB IR IR Laser
Camera Camera Projector
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