Industrial to mobile robots
Professor Gurvinder S Virk
Technical Director
InnotecUK Limited
Email: gurvinder.virk@innotecuk.com
Stationary industrial manipulator robots
Cartesian/Gantry SCARA robots
Cylindrical robots: 2T, 1R Articulated robots (R)
Spherical robots
Parallel robots
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Industrial robot workspace
Typical workspaces for common robot
configurations
Main robot sectors
Industrial robots: powerful, precise robots for manufacturing
Spot welding Handling Assembling Machining Polishing Inspecting Palletizing
Robots for hazardous environments: Mobile robot applications
Power lines Petrochemical High buildings Oil tanks Power stations De-mining
Service robots: Useful tasks for humans (medical, non-medical)
Garbage Domestic Servant Assistance Person carrier Rehabilitation Surgery
Classification of robots
Locomotion Application
• Stationary robots • Industrial robots
o Industrial • Service robots
manipulators
• Medical robots
• Mobile robots
• Domestic robots
o Wheeled robots
o Legged robots • Military robots
o Climbing robots • Space robots
o Hybrid robot
o Snake robots
o Swimming robots
o Flying robots, etc
• Micro robots
• Modular robots
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Wheeled and legged robots
Wheeled Legged
Single wheeled (ball) One legged
Two wheeled Two legged
Three wheeled Three legged
Four wheeled Four legged
Five or more wheels Five/six legged
Tracked robots Lots of legs
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Wheeled and tracked robots
Biggest range of robots developed to date.
Continuous track for motion needed.
• Cars, rovers, tanks
• Mainly for 2D environments but designs can handle 3D
cases as well at low speed.
• Many different design and configurations for handling a
range of environments
o soft ground
o uneven ground
o loose material /uneven traction
Locomotion is achieved by providing traction using
motors/engines, gears and tyres/ tracks, etc
Non-holonomic constraints: constraint on the
velocities possible. Your robot can move in some
directions (forward and backward), but not others
(sideward)
Wheeled Drive System Terms
Gear Ratio: Can be described many ways
• Motor Speed / Output Speed
Efficiency - Work lost due to drive losses
• Friction, heat, misalignment
Friction Force - Tractive (pushing) force
generated between floor and wheel.
W is rotational speed & V is linear speed
(velocity)
N1 is # of teeth on input gear/sprocket
N2 is # of teeth on output gear/sprocket
Good Features for Wheeled Systems
Attribute Good Features to Have
high top speed high power, low losses, the right gear ratio
acceleration high power, low inertia, low mass, the right gear ratio
pushing/pulling ability high power, high traction, the right gear ratio, low losses
maneuverability good turning method
accuracy good control calibration, the right gear ratio
obstacle handling ground clearance, obstacle "protection," drive wheels on floor
climbing ability high traction, the right gear ratio, ground clearance
reliability/durability simple, robust designs, good fastening systems
ease of control intuitive control method, high reliability
Good Wheeled Design Features
Attribute Good Features to Have
high top speed high power, low losses, the right gear ratio
acceleration high power, low inertia, low mass, the right gear ratio
pushing/pulling ability high power, high traction, the right gear ratio, low losses
maneuverability good turning method
accuracy good control calibration, the right gear ratio
obstacle handling ground clearance, obstacle "protection," drive wheels on floor
climbing ability high traction, the right gear ratio, ground clearance
reliability/durability simple, robust designs, good fastening systems
ease of control intuitive control method, high reliability
Traction Fundamentals Terminology
maximum friction normal
torque tractive = x
turning the
coefficient force
force
weight wheel
tractive normal
force force
The friction coefficient for any given contact with the floor, multiplied by
the normal force, equals the maximum tractive force can be applied at
the contact area.
Tractive force is important! It’s what moves the robot.
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Traction Fundamentals “Friction Coefficient”
Friction coefficient is dependent on:
• Materials of the robot wheels (or belts)
• Shape of the robot wheels (or belts)
• Material of the floor surface
• Surface conditions
Important also for climbing robots: adhesion
to the surface being climbed
Wheel types
Fixed wheel Centered orientable wheel
Off-centered orientable wheel
(Castor wheel) Swedish wheel: omnidirectional
property
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Number & Location of Drive Wheels
Many variations, and there is no “right” answer
Front
simple simple simple simple 6 wheel
rear wheel drive front wheel drive all wheel drive center drive center drive
Drive elements can:
steer (to enable turning or “crabbing”)
move up and down (to engage/disengage,
tracked drive
or to enable climbing)
** Can combine some of these features together **
Advice: Don’t make it more complex than it has to be!
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Legged systems
Legged systems provide best form of locomotion
in unstructured environments by stepping
motions
Require foothold contact points rather than
continuous tracks for locomotion: less damage
to environment
Static and dynamic stability for locomotion: CoG
always in the support area of machine
Walking and Running: one leg always in contact
with ground
Different configurations and different number of
legs: walking gait, periodic gait, free gait
Periodic versus Free gait
Periodic gaits are simple and thus often used
They include, however, certain problems:
• legs are forced to go to support state in a certain
order, which may stop the motion if a proper
footplace is not available
• stability may be difficult to maintain if critical
terrain conditions coincidence with the low
stability margin support pattern
Free gaits offer more flexibility, but are
individual in nature but need more complex
control
Number of Legs?
1 legged systems
• Hopping machines: statically unstable
2 legged systems
• Bipeds: complex walking
4 legged systems
• Many animals: static and dynamic easier to
control
6 legged systems
• Insects: alternating tripod gait
etc
Walking pattern in legs
Load: touching down and taking load of body
Drive: supporting body and pushing for
motion
Unload: releasing load and getting ready to
step
Recover: stepping
Running also has a flight phase
Insect walking
leg driving
left rear 3
left middle 2
left front 1
Slow gait
right rear 4 1 6
right middle 5
right front 6
2 5
left rear 3
left middle 2 3
left front 1 4
Faster gait
right rear 4
right middle 5
right front 6
left rear 3
left middle 2
left front 1
Even faster gait – Alternating tripod gait
right rear 4
right middle 5
right front 6
Zero Moment Point
Definition: The ZMP is the point where the
total forces and moments acting on the robot
are zero
If ZMP is inside the contact polygon between
the feet/foot and the robot, the (biped) robot is
stable
Climbing robots
Adhesion/ climbing using different methods
• Magnetic (permanent and electro-magnets) Bigfoot
• Vacuum
• Van der Waals forces
• Special limbs (peg climbing)
Sadie
Maggie
Peg climber
Winspecbot
Zigzag
Vacuum gripper design
Stop slipping µ F>W h
CoG F
h/R>1/µ
R
µ
Stop falling FR>hW
W
Gecko robots
• Geckos are known for their
remarkable wall-climbing ability.
• Microscopic structures on toe pads
are responsible for adhesion.
• Adhesion by van der Waals forces
Gecko materials
• Artificial Gecko materials being
developed
1 cm 75 µm 20 µm 1 µm
Hybrid and special locomotion Robots
Combine a number of locomotion method to
give better motions
• Legs + wheels
• Wheels + boat
• Wheels + flying (aeroplane!)
Hylos, LRP, WorkPartner,
• Hovering and flying, etc France Helsinki Univ
• Snakelike
• Wegs
Modular snake,
CMU, USA
X-Rhex Lite robot, Univ
Pennsylvania, USA
The Grand Challenge for Robotics
By Mid-21st Century, a team of fully autonomous
humanoid robots shall win a soccer game against
human World Cup Champion team under the official
regulation of FIFA
Robocup competition exists to promote the
development of technologies needed
• Different leagues: wheeled, 2 legs, 4 legs, etc
• Simulation League
• Small-Size League (F-180)
• Middle-Size League (F2000)
• Sony Four Legged Robot League
• Humanoid League
More details on www.robocup.org
GS Virk: Personal interests
Robotics and control
• Climbing and walking robots
• Mobile robots (olfaction)
• Physical assistant robots
o Mobility exoskeletons for the elderly
o Non-medical and Medical exos
Standardisation to widen robotic applications
• Robot safety
• Robot modularity
Renewable energy technologies
• Built sector; water desalination
Help use professional work for public benefit
globally
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NERO 3 and Robug 2 Climbing robots
Nero3: Nuclear inspection
and remedial works robot
Robug2: Self-launching
wall climbing robot
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Robugs for UoP/Portech
R
o
b
u
g
I Robug IIs
Robug III Robug IV
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Winspecbot inspection robot
Goal: Make a four legged
climbing robot to perform pipe
inspection tasks on several
terrain condition such as
horizontal straight, vertical
straight, and upside down
ferromagnetic surfaces
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Smelling robots: Navigation
Blind cat
Applications (unstable fields)
• Leak detection: chemical plants
• Detection of explosives
• Drug detection: airports
• Cleaning/painting: no map needed
• Multiple agents co-operating
Chemotaxis Non-cooperative Cooperative
Conclusions
Shift from industrial manipulators
to mobile robotics for in-situ
operations
Types of mobility described
Examples of mobile robots given
Thanks are expressed to all the colleagues (too many to
mention individually) across the world who have helped with
the formulation of this lecture on Robotics from material
placed on the www
