Robot Sensors

7/21/2019 Robot Sensors

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Robot Sensors




6th March 2014, Thursday




1. Our bodies were

created with wisdom.2. Our bodies are

made out of external

parts and internal

parts.

3. Our senses help us

discover and

understand the worldaround us.

Human Senses

NE

T

EYE S




Did you know










http://www.cfcindia.com/web/books/zac/amazing_facts.html#Chapter_2


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A Typical Mobile

Robot system

A typical

Mobile

robot



Sensors are the parts that act like senses and candetect objects or things like heat and light andconvert the object information into symbols or inanalog or digital form so that computers understand.And then Robots react according to information provided by the sensory [email protected] 912/15/2015

Sensor - a device which detects or measures a physical property

and records, indicates, or otherwise responds to it.

‘Transducer' is a device that transfers power /Energy from

one system to another in the same or in the different form




The difference between a sensor and a transducer

is that a sensor detects and reports energywhereas a transducer actually converts energy

from one form to another.

According to the instrument society of America - " A

Sensor or Transducer is a device which provides ausable output in response to a specified

measurand"




Quantity being

Measured

Input Device

(Sensor)

Output Device

(Actuator)

Light Level

Light Dependant Resistor (LDR)

Photodiode

Photo-transistor

Solar Cell

Lights & Lamps

LED’s & Displays

Fibre Optics

Temperature

Thermocouple

Thermistor

Thermostat

Resistive Temperature Detectors

Heater

Fan

Force/PressureStrain Gauge

Pressure Switch

Load Cells

Lifts & JacksElectromagnet

Vibration

Position

Potentiometer

Encoders

Reflective/Slotted Opto-switch

LVDT

Motor

Solenoid

Panel Meters

Speed

Tacho-generator

Reflective/Slotted Opto-coupler

Doppler Effect Sensors

AC and DC Motors

Stepper Motor

Brake

SoundCarbon Microphone

Piezo-electric Crystal

Bell

Buzzer

Loudspeaker



What is Sensing ?

• Collect information about the world /surrounding

• Sensor - an electrical /mechanical

/chemical device that maps anenvironmental attribute to a

quantitative measurement

[email protected] 1212/15/2015



Why Do Robots Need Sensors?• Provides “awareness” of surroundings

– What’s ahead, around, “out there”?

• Allows interaction with environment – Robot lawn mower can “see” cut grass

• Protection & Self-Preservation – Safety, Damage Prevention, Stairwell sensor

• Gives the robot capability to goal-seek – Find colorful objects, seek goals

• Makes robots “interesting”




Why do robots need sensors?

internal information

What is the angle of my arm?





Where am I?

localization

?





Will I hit anything?

obstacle detection




Sensing for specific tasks

Where is the cropline?

Autonomousharvesting





Autonomous material handling

Where are the forkholes?





Where is the face?

Face detection & [email protected] 1912/15/2015



Sensors - What Can Be Sensed?

• Light – Presence, color, intensity, content (mod), direction

• Sound – Presence, frequency, intensity, content (mod), direction

• Heat – Temperature, wavelength, magnitude, direction

• Chemicals – Presence, concentration, identity, etc.

• Object Proximity – Presence/absence, distance, bearing, color, etc.

• Physical orientation/attitude/position – Magnitude, pitch, roll, yaw, coordinates, etc.




Sensors - What Can Be Sensed?

• Magnetic & Electric Fields

– Presence, magnitude, orientation, content (mod)

• Resistance (electrical, indirectly via V/I)

– Presence, magnitude, etc.

• Capacitance (via excitation/oscillation)

– Presence, magnitude, etc.

• Inductance (via excitation/oscillation) – Presence, magnitude, etc.

• Other Things?




Different Types of Sensors

• Feelers (Whiskers, Bumpers) – Mechanical

• Photoelectric (Visible) – Active & Passive

• Infrared (light) – Active & Passive• Ultrasonic (sound) – Active & Passive

• Sonic – Active & Passive

• Resistive/Capacitive/Inductive – Active & Passive




• Visual – Cameras & Arrays (Active & Passive)• Color Sensors (Active & Passive)

• Magnetic (Active & Passive)

• Orientation (Pitch & Roll)• GPS (location, altitude)

• Compass (orientation, bearing)

• Voltage – Electric Field Sensors• Current – Magnetic Field Sensors

• Chemical – Smoke Detectors, Gas Sensors

Different Types of Sensors




Sensors – Feelers

• Whiskers – Piano wire suspended through conductive “hoop”

– Deflection causes contact with “hoop”

– Springy wire that touches studs when deflected

– Reaches beyond robot a few inches – Simple, cheap, binary output

• Bumpers & Guards – Impact/Collision sensor, senses pressure/contact

– Microswitches & wires or framework that moves

– Simple, cheap, binary output, easy to read




Feelers - Whiskers




Feelers - Bumpers & Guards

From Kevin Ross’s “Getting Started Article (SRS Website)




Sensors – Chemical

• Smoke Detectors - Cheap, readily available, $5

• Oxygen concentration sensors - CO, H4S, CH4, pricey

• See HowStuffWorks.com







Classification of Sensors1. Tactile Sensors - Used to tell us if we hit something

– Magnetic

– Ultrasonic

– Microwave

– Optical

2. Time of Flight Sensors - Used to tell us how far objects are from

us

– Ultrasonic

– Laser-Based3. Compasses - Used to tell us our heading (angle from North)

– Mechanical

– Fluxgate

– Hall-Effect

4. Miscellaneous - Used to tell us things about our environment – Gyroscopes

– Motion Detection

– Smoke

– Pressure

– Temperature [email protected] 2912/15/2015






Light sensor

photo-resistor

resistance changeswith light intensity





Light Sensor used to produce an Digital Signal



Temperature sensor

thermal resistor

“thermistor”

resistance changeswith temperature





Thermocouple used to produce an Analogue Signal

Analogue Sensors produce a continuous output signal or voltage which is generally proportional to

the quantity being measured. Physical quantities such as Temperature, Speed, Pressure,

Displacement, Strain etc are all analogue quantities as they tend to be continuous in nature. Forexample, the temperature of a liquid can be measured using a thermometer or thermocouple which

continuously responds to temperature changes as the liquid is heated up or cooled down.



Potentiometer

another

rotational sensor

resistance changes

with positionof dial

R


S B d S d



Sensors Based on Sound

• SONAR: Sound Navigation and Ranging

– bounce sound off of something

– measure time for reflection to be heard - gives a rangemeasurement

– measure change in frequency - gives the relative speed of theobject (Doppler effect)

– bats and dolphins use it with amazing results

– robots use it w/ less than amazing results




Sonar and IR Proxmity




Odor Sensors• Detection of chemical compounds and their

density in an area

– spectroscopy - mostly lab restricted

– fibre-optic techniques - recently developed – chemical detection - sniffers aand electronic noses

via “wet chemistry on a chip”

• No major penetration in robotics yetapplications are vast (e.g. mine detection)




Touch Sensors• Whiskers, bumpers etc.

– mechanical contact leads to

• closing/opening of a switch

• change in resistance of some element

• change in capacitance of some element

• change in spring tension

• ...


P i i

S



Proprioceptive Sensors

• Encoders, Potentiometers

– measure angle of turn via change in resistance or

by counting optical pulses

• Gyroscopes

– measure rate of change of angles

– fiber-optic (newer, better), magnetic (older)

• Compass

– measure which way is north

• GPS: measure location relative to [email protected] 4012/15/2015



Propriceptive Sensors




RANGE SENSING

Range sensing techniques:

1.Triangulation

2.Structured Lighting Approach3.Time of Flight Range Finders

It measures the distance from a

reference point (usually on the sensoritself) to object In the field of operation of

the sensor.




1. Inductive Sensors

2. Hall-Effect Sensors3. Capacitive Sensors

4. Ultrasonic Sensors

5. Optical Proximity Sensors

Proximity sensing

Function:-

Indicates the presence of an object within a specifieddistance interval.

They gives a binary output.

Applications:-

Used in robotics for near-field work in

connection with object grasping or avoidance.




An Inductive

Sensor

Principle:- Based on the change of inductance

due to the presence of a metallic body




Hall-Effect Sensor

Lorentz force = q ( v X B )

where q - the charge

v - Velocity vector

B - magnetic field vector

X - Vector cross-product

Principle:- Based on the principle of a Lorentz force

which acts on a charged particle travelling through amagnetic field.




Capacitive Sensor

Principle:- Based on detecting a change in capacitance induced by a

surface that is brought near the sensing element.

They can detect all solid and liquid materials.




Principle:- Based on the transmission and detection of acoustic energy signals

Ultrasonic Sensor


Ultrasonic sensors use sound to accurately detect objects and measure distances

Ultrasonic



Wave forms associated with an ultrasonic proximity sensor

Ultrasonic

Sensor . . .





Photo-optical Sensor

https://pc-control.co.uk/Optical.htm




Touch sensor - micro switch




Touch sensor - analog type







industrial applications of torque sensors include measuring metal removal rates inmachine tools; the calibration of torque tools and sensors; measuring peel forces,

friction, and bottle cap torque; testing springs; and making biodynamic measurements

Applications for torque sensors include determining the amount of power an engine,

motor, turbine, or other rotating device generates or consumes

Torque is measured by either sensing the actual shaft deflection caused by a twisting

force, or by detecting the effects of this deflection. The surface of a shaft under torque

will experience compression and tension, as shown in Figure 6-4. To measure torque,

strain gage elements usually are mounted in pairs on the shaft, one gauge measuring

the increase in length (in the direction in which the surface is under tension), the

other measuring the decrease in length in the other direction

Tactile sensor – embedded in the fingers of gripper




Tactile sensor embedded in the fingers of gripper

Artificial Skin Sensor






Keep them safe & Sound

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Robot Sensors