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ROBOTICS ROBOTICS 01PEEQW 01PEEQW 01PEEQW 01PEEQW Basilio Bona - - PowerPoint PPT Presentation
ROBOTICS ROBOTICS 01PEEQW 01PEEQW 01PEEQW 01PEEQW Basilio Bona - - PowerPoint PPT Presentation
ROBOTICS ROBOTICS 01PEEQW 01PEEQW 01PEEQW 01PEEQW Basilio Bona Basilio Bona DAUIN DAUIN Politecnico di Torino Politecnico di Torino Mobile & Service Robotics Mobile & Service Robotics Sensors for Robotics Sensors for
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Laser sensors (laser scanners, laser range-finders))
They measure the distance from reflecting obstacles on a plane Rays are transmitted and received coaxially The target is illuminated by collimated rays The receiver measures the time-of-flight (back and forth) It is possible to change the rays direction (2D or 3D measurements)
D D′
Transmitter Receiver
L D D′
( ) 2 ( ) 2 c f L D D L D θ λ λ π ′ ′ = + + = + +
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half mirror
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mplitude
λ
Laser sensors
Phase Ampli
θ
Transmitted Reflected
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Laser sensors
METHODS Pulsed laser: direct measurement of time-of-flight: one shall be able to measure intervals in the picoseconds range Beat frequency between a modulating wave and the reflected Beat frequency between a modulating wave and the reflected wave Phase delay
It is the easiest implementable method
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Laser sensors
; 2 2 c D L D L f c f D θ λ λ π ′ = = + = + = = ′ = speed of light frequency of the moduling wave total distance The confidence on distance estimation is inversely proportional to the square value of the received signal amplitude 5 60 D f λ ′ = = = total distance MHz; m
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Laser sensors
A typical image from a rotating mirror laser scanner. Segment lengths are proportional to the measurement uncertainty
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Laser scanners for accurate measurements
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LIDARS
LIDARs are laser scanners that rotate around an axis allowing to scan a 3D space region The technology requires a precise synchronization between the laser scan process and the rotation around the axis for precise map creation
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Example: DRC 2013
These are the rotating scanners
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The CHIMP (CMU Highly Intelligent Mobile Platform)
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Triangulation
Triangulation is the process of determining the location of an
- bject by measuring angles from known points to the object at
either end of a fixed known baseline The point can be chosen as the third point of a triangle with one known side and two known angles In practice: Light sheets (or other patterns) are projected on the target Reflected light is captured by a linear or 2D matrix light sensor Simple trigonometric relations are used to compute the distance
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Triangulation
d β
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; tan tan 1 1 tan tan d d d α β α β = + ⇒ = + ℓ ℓ
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baseline ℓ
β α
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Triangulation
sin sin sin sin sin BC AC AB RC AC BC α β γ α β α β = = = ⋅ = ⋅ ⋅ ⋅ C γ
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sin sin sin sin sin sin( ) AB RC AB RC α β γ α β α β ⋅ ⋅ = ⋅ ⋅ = +
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A B R β α
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Triangulation
Transmitter
D f
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L D f x =
Transmitter
L x f
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Structured light (infrared or visible spectrum)
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Structured light
Monodimensional case cot Du x f u α = − cot f u α −
D f α
u cot Df z f u α = −
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