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Robotics-2 Sensors


SENSORS

What the sensor sense ? how it sense it ? how it process it ?  how it uses it ?

# you must consider the task/tasks of robot,the best sensor type to sense it,the best mechanical design that will allow robot to use its sensory information to perform the task

Machine perception

True world –>Sensing device–>Signal processing—>Control system

#Everything that the human sense can do without the handicaps (glasses);

Vision outside the rgb spectrum,active vision (radar and optical range sensor measurement),hearing outside the  20 hz-20 khz  range,chemical analysis beyond the taste and smell,radiation neutron pozitron alfa….

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Transduction to Electronics

Thermistor: temperature-to-resistance



Electrochemical: chemistry-to-voltage



Photocurrent: light intensity-to-current



Pyroelectric: thermal radiation-to-voltage



Humidity: humidity-to-capacitance



Length: position-to-inductance



Microphone: sound pressure-to-<anything>


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Transduction to vision

Thermometers: temperature-to-length



Barometers:air pressure-to-length



Scales:weight-to-angle



Humidity:hair curl-to-angle



Indicator dyes:chemistry-to-color


Photo film:light/radiation-to-silver density



Speedometers:velocity-to-angle


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Characterizing the Sensor Performance

i will share some basic knowledge that everyone in robotics will need to understand .


#Sensitivity : Minimum input change to result in output change

#Cross sensitivity : Variation with other changes like temperature

#Error / accuracy : difference between the real value and the generated value

Accuracy=1- (m-v)/v

#Noise : Most sensors generates measurement that are contaminated  by noise

1)systematic noise : errors that could be modelled for example through calibration

2)random noise : errors that can not be predicted .Typically modelled in a probabilistic fashion

Processing Properties


Sensors dont provide states,sensors provide signals,processing converts signals to states;

Processing ;

#Electronics   : measure voltage going through a circuit on a switch

#Signal processing : recognize a voice, separate it from the noise

#Computation : edge detection of objects in an image ,followed by object recognition

Sensor Types and Measurements

1)contact →bump, switch

2)distance →ultrasound, radar, infrared (IR)

3)light level →photo cells, cameras

4)sound—>levelmicrophones

5)strain →strain gauges

6)rotation →encoders

7)magnetism compasses

8)smell →chemical

9)temperature →thermal, infrared

10)inclination →inclinometers, gyroscopes

11)pressure →pressure gauges

12)altitude →altimeters

i finish my lesson with a funny video , have fun 🙂

Eylül 9, 2010 Posted by | Robotic | Yorum bırakın

Robotics


Hi,

Today i am introducing some basic robotic term , we need to know terms excellently because they are so fundamental . In robotic lessons , i will give definitons , robotic news ,  how to make simple robots and other fundamental things . It s so funny area .

Some definition for robotics

İntelligent agent : Agent perceives it enviroment via sensors  and acts rationally upon that enviroment with its effectors

Rational : the performance measure that defines criterion of success,the agent’s prior knowledge of the enviroment,the actions that the agent can perform,the agent’s percept sequence to date.

Performence measure : embodies the criterion for success of an agents behaviour.

Characteristics of agent

Situatedness : agent receive some information from its enviroment and performs some action.

Autonomy : agent can act without direct intervention by humans or other agents

Adaptivity : agent can react flexibly to changes in its enviroment

Sociability : agent is capable of interacting in a peer to peer manner with other agents or humans

So the structure of an agent  : Agent = architecture + program

Robotics

A robotic system is which exists in the physical world and autonomously senses its enviroment and acts in it.

Feedback : continous monitoring of the sensors and reacting to their changes,self-regulation

Two kind of feedback;positive and negative

Negative feedback acts to regulate the state;eg: if too high turn down : thermostatics

Positive feedback acts to amplify the state ;eg : the more there is the more added

Components of a robot

Sensors

*Sonars ; use sound to measure the positions of objects

*İnfrared proximity detector; use light to detect the presence of objects

*Video cameras;a number of different tasks (usually for image and video processing)

*Shaft encoder; measure the rotation of a Wheel or motor shaft like the odometer of a car;velocity etc.

Actuators/effectors

*wheels,legs and arms,speakers,dispensers for various materials

Locomotion system

On-board computer system

Robot Soccer

Day by day , i also plan to share robot soccer with you . Next race will be at Istanbul / Bosphorus  Uni  . As you guess, we are so excited for that .

General subtasks for soccer robot is;

-Vision;

-Movement;

-Fall Detection;

– Kicking;

-Localization;

– Communication;

– General Architecture;

– Coordination.

VİSİON

A CMOS CAMERA used to capture images from enviroment.

Some computer vision problem faced like;segmentation,blob clustering,object recognition,illumination invariance.

Color segmentation

The image captured by the robot’s camera, in the YCbCr format, is a set of numbers, ranging from 0 to 255 along each dimension, representing luminance (Y) and chrominance (Cb, Cr).

-0 = pink;

_ 1 = yellow;

_ 2 = blue;

_ 3 = orange;

_ 4 = marker green;

_ 5 = red;

_ 6 = dark (robot) blue;

_ 7 = white;

_ 8 = field green; and

_ 9 = black

Robo soccer is a very funny area , their aim is to bet a human team at 2050 world cup final , i think they will!!

Here is a match video from robo soccer tournament 2007 final :

Here they show some good moves :

See you !

Ağustos 24, 2010 Posted by | Robotic | , , , , , , , , | Yorum bırakın