robot sensors

7/21/2019 Robot Sensors

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12/15/2015 baburao@karunya.edu 1

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

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

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 systembaburao@karunya.edu 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

Force/PressureStrain Gauge

Pressure Switch

Load Cells

Lifts & JacksElectromagnet

Vibration

Position

Potentiometer

Encoders

Reflective/Slotted Opto-switch

Solenoid

Panel Meters

Tacho-generator

Reflective/Slotted Opto-coupler

Doppler Effect Sensors

AC and DC Motors

Stepper Motor

SoundCarbon Microphone

Piezo-electric Crystal

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

baburao@karunya.edu 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 & trackingbaburao@karunya.edu 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

– 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 baburao@karunya.edu 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

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

• ...

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 globebaburao@karunya.edu 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

robot sensors

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