Robot Sensors - Massachusetts Institute of...
Transcript of Robot Sensors - Massachusetts Institute of...
Robot Sensors 2.12 Introduction to Robotics
Lecture HandoutSeptember 20, 2004
H. Harry AsadaMassachusetts Institute of Technology
Touch Sensor
CCD Camera Vision System
Ultrasonic Sensor
Torque Sensor
Touch Sensors
Photo removed for copyright reasons:
Sony Aibo™ dog robot. http://www.sony.net/
Products/aibo/.
Ultrasonic Sensor
Photo removed for copyright reasons.
Transition Technology meal delivery robot.
Wrist Force Sensor
Tension Sensor
Tactile Sensor
copyright reasons.
finger and thumb.
Photo removed for
Robot hand with
Infrared
Bumper Sensor
Distance Sensor
Slip Sensors
Internal and External Sensors
Actuators
Internal Sensors
Environment
External Sensors
Reference Command
Robot sensor taxonomy
• Internal sensors – Position sensor – Velocity sensors – Torque and acceleration sensors
• External sensors – Tactile sensors – Force and torques sensors – Proximity sensors – Range sensors – Vision sensors– Others
Actuator &Load
PositionSensors
ReferenceCommand
FeedbackLaw
• Potentiometer• Optical shaft encoder
DC Motor
Arm Links
Gearing
Joint Axis
Internal Position Sensors
Optical Shaft Encoder
Disk with grid patternLight source: LED
Opaque
Translucent
Shaft
Photodetector
As the shaft rotates, a pulse train is generated. Counting the number pulses gives the angle of rotation.
Distinguishing clockwise and counter-clockwise rotations
Track A
Track B
Photodetectors
Clockwise rotation Counter-clockwise rotation
A
-90o
B
+90o
A
B
Track A is 90 degrees ahead of track B. Track A is 90 degrees behind.
Using an up-down counter, CW and CCW rotations are correctly counted.
A Phase Up-Down Counter
Most sensitive bit
B Phase
n-bit parallel
Least sensitive bit
Clear/Initialization
Initialization of the Up-Down Counter
When the joint is brought to a home position, the z-phase pulse is generated for initializing the up-down counter.
Home Position
Z B A
Absolute Encoder
Parallel Data
No initialization needed
Velocity Measurement Using an Encoder
Internal Velocity Sensors
~Velocity = Pulse Frequency
Counter clear
TSampling period
= Pulse counting interval
The drawback of pulse frequency measurement
As the angular velocity gets slower, only a few pulses are observed in the fixed time interval:
discretization error increases.
T
t int
A better alternative is to measure the interval between adjacent pulses tint, and take the reciprocal for estimating the velocity.
1ω ∝tint
Hybrid velocity counterMeasuring the time interval between adjacent pulses:
More accurate in slower speed
Low speed counter
High speed counter
t int
T
Counting the number of pulses in a fixed time interval: More accurate in higher speed
Sensor as a “System”
Multi-stageSignal transduction
and modulationKey Transducer
Signal Source
Low-level Filtering
High-level Filtering
Active Modulation
A sensor is often a system consisting of multiple stages of signal transduction and modulation, low-level and high-level filters, and a modulation unit. It comprises a communication and a power unit as well.
The shaft encoder for measuring both position and velocity
Shaft rotation
Disc rotation
LED-PD
Threshold : binary signals
A-B phase detection and counting
Hybrid velocity estimation
Key Transducer
Signal Source
Low-level Filtering
High-l
Light intensity modulation
evel Filtering
Active Modulation
Torque Measurement
iKtm ⋅=τ
Via armature current measurement:
The current is measured by inserting a small resister (2~3 Ω) in series and measuring the voltage drop across the resister.
i
Rt
iRV tt ⋅=
Internal Torque Sensors
Torque Measurement
θτ ∆⋅= am k
Via measurement of the torsion/strain of the shaft:
Strain Gauges
Strain Gauge Force/Torque Sensors
Strain Gauges
outV
Temperature-Compensated Wheatstone Bridge
6-Axis Wrist Force/Torque Sensor
Strain Gauges
Outputs:y1, y2, …, ym
Fy
NyFz
Nz
Fx Nx
Strain Gauges
Wrist Force/Torque Sensors
Strain Gauges
Outputs:y1, y2, …, ym
6-Axis Wrist Force/Torque Sensor
⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜
⎝
⎛
=⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛=∆
⎟⎟⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜⎜⎜
⎝
⎛
∂∂
∂∂
∂∂
∂∂
∂∂
∂∂
=
∆⋅=
z
z
y
x
m
z
m
x
m
x
zyx
sensor
sensor
N
FFF
y
y
Ny
Fy
Fy
Ny
Fy
Fy
M
M
LL
MO
MO
L
Fy
J
yJF
,1
2
111
#
Fy
NyFz
Nz
Fx Nx
Hybrid Position/Force Control
Wrist Force/Torque Sensor
Position Feedback
control
control
Robot Task
Environment
Position Reference
Inputs
Force Reference
Inputs
+
+
+
+
_
_
Position/velocity
compensator
Force/torque
compensator
Force Feedback
Tactile SensorsPrinciple
Tactile Pad
Resistance R
P
Electrodes
Conductive Rubber:
Force/Pressure
Media impregnated with conductive dopants Force/Pressure P
Other Methods:CapacitiveOpticalPiezoelectricMagneto-resistiveMagneto-strictive
Sensor Pad:2-D sensor array
Pressure distribution
Technical Issues: How to process the 2-D data of pressure distribution How to reduce wires
A tactile sensor = Measuring 2-D pressure distribution
A Matrix Wiring Structure for Reducing Cables
Sensor Element
N Switches
N Switches
B.E. Robertson and A.J. Walkden, 1985
16 x 16, 256 elements
Photo and diagrams removed for copyright reasons.
Integrating sensor elements with signal processing circuitry on a VLSI chip
Integrating sensor elements with signal processing circuitry on a VLSI chip
Pressure patterns (a) Intensity(b) Contour
VLSI tactile array sensor with 20 x 20 grids of 75 um separation
by M.H. Raibert and J.E. Tanner, 1982
Two photos removed for copyright reasons.
Ultrasonic SensorsDistance Sensors
Object
Transmitted Sonic Pulse
Reflected Echo
tpulse
Echo pulse
Transmitted
Measuring the distance d to an object by the time interval between the transmitted and reflected sonic pulses.
2 d = v t v = speed of sound, t= time interval
_ _ _ _ _ _ _ _ _ _
PiezoelectricTransducer for Transmitting and Receiving Acoustic Signals
Actuator Sensor
Pressure Wave
F + + + + + + + + + + ∆x
F = d33 ⋅ q Piezoelectric Material V = d33 ⋅∆x
(Force) = proportional to (Charge) (Voltage) = proportional to (Displacement)
V
Dielectric Capacitance Transducer for Transmitting and Receiving Acoustic Signals
Figure by MIT OCW.
Swept frequency method
Auditory Link (Earphones)
Variable Frequency Generator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
Filter Process
Hearing Process
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Auditory Link(Earphones)
Variable FrequencyGenerator
CWFM Sonar for Blind Persons and Machines
Human Processor
Machine
FilterProcess
HearingProcess
Drive Amplifier
Receive Amplifier
Tx Transducer
Rx Transducer
Figure by MIT OCW.
Proximity Sensors
Basic Principle
Transmitter +
Receiver
Transmitter +
Receiver
The approach of an object changes: Back pressure: pneumatic sensor Inductance: inductive/magnetic sensors Capacitance: capacitive sensor
Pneumatic Proximity SensorSupply Pressure
Object
Distance
Back Pressure
Output Pressure
Threshold
Distance
Magnetic Lead SwitchesFilled with
Glass Tube Inert Gas
S N
S N N S
Leads Permanent OFF ON Magnet
For extending the detectable range Magnetic Lead Switch
Permanent Magnet
Magnetic Material
Magnetic Material:
A Fake Mine
Optical Proximity Sensors
LED Photo Detector
R2
Vout
R1
3V
Photodiode
LED
Photo Detector
Imaging Sensors CCD CameraPhoto-electric effect
Photon Photo Current oc Illumination Intensity
Absorbs photon energy to move electrons to a higher energy level
Energy = (Plank’s Constant) x (Speed of Light)/(Wavelength)
CCD (Charge Coupled Device)
+ + + ---
Light beam
Photo Sensitive ArrayScanned pixel by pixel
Image ProcessingA. Two-dimensional Images
Structured Lighting
Figure by MIT OCW.
CameraCameraCameraCameraCameraCamera Slit LightSlit LightSlit LightSlit LightSlit LightSlit LightSlit LightSlit LightSlit LightSlit Light
Figure by MIT OCW.
Structured LightingSlight light scanned over 3D objects
Photos removed for copyright reasons.
3D range Finders
X
T
B
M
N
L
O
M
B
S O
LN
T
S
D
D
2
2
Rotational Mirror
Detector
Laser Light Source
Laser Range Finder
Known distance between the mirror and the detector
3D Range Finders
Figure by MIT OCW.
Simultaneous Location And Mapping (SLAM)
Sensor Data Map Building
Location EstimationRobot Control
Image courtesy of JPL.
Planet Exploration Robotics
Human Sensors
Human Operator Joystick
Figure by MIT OCW.
Measuring human motion for controlling Remote manipulators
Hazardous environment
Manipulator
Surgical Robot System
Robot ControlVirtual
Reality
Photo removed for copyright reasons. Surgical robot with virtual reality
workstation (left) and robot (right)
Data Glove Fingernail Sensors:Measurement of hand Measurement of Fingertip Touch Force
posture and touch force and Posture through Nail Color Change
Free-Fingered Glove
Photos removed for copyright reasons.
Instrumented Fingernails
Figure by MIT OCW. After Spence, Basic Human Anatomy.
Nail Matrix
Nail
Nail B ed
Micro LED & Photo Detectors
Pressure:vein occlusion
No sensor pad is needed
Measurement Principle
T ransm itted L ight R e f
L ight
3V
R 1 P h o todio d e
660 nm R ed LE D
lec ted Vout
R 2
V ou t 0 Contact
Pressure
Applications
Virtual Switches Task and Skill Monitoring
Photos removed for copyright reasons.