Gui Cavalcanti 5122011 Locomotion and Manipulation Overview Locomotion Types of locomotion Stability Locomotion design Models Types of control Gaits Manipulation Compliance Forward ID: 333666
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Slide1Slide2
Introduction to Robot Design:
Gui
Cavalcanti5/12/2011
Locomotion and ManipulationSlide3
Overview
Locomotion
Types of locomotionStabilityLocomotion designModelsTypes of control
Gaits
Manipulation
Compliance
Forward
kinematics
Inverse kinematicsSlide4
Types of Locomotion
Air
PlanesHelicoptersOrnithoptersGroundWheelsTracksLegs
Water
Propellers
Fins
Buoyancy Control
Space
Rockets
Inertial OrientationSlide5
Stability
What makes a hot air balloon stable?Slide6
Stability
Center of Lift
Center of MassSlide7
Stability
Lift can be modeled as an always-upward force centered at the COL
Mass can be modeled as an always-downward force centered at the COM Slide8
Passive StabilitySlide9
Air LocomotionSlide10
Air Locomotion
Planes
Wings are shaped to use forward velocity to generate liftControl surfaces on wings control orientation changesHelicoptersSpinning wings (the rotor) are shaped to use rotational velocity to generate lift independent of forward velocity
Many configurations of additional rotors and control of existing rotor blade orientation provide orientation changes
Ornithopters
Flapping, passively-compliant wings deform into airfoils to produce forward velocity and lift at each
wingstroke
Shaped tails or differences in wing amplitude control orientation changesSlide11
Planes
Design space:
Many existing, robust easy-to-modify RC plane kits to choose from.Designing one from scratch is still a guess-and-try scienceBare minimum for robot control: Attitude sensing, inertial measurement, flap control
Existing robots:
Global Hawk, Reaper, Predator
Predator UAV
Global Hawk
RC
Plane
KitSlide12
Plane Stability
Center of Lift
Center of Mass
Center of DragSlide13
Plane InstabilitySlide14
Plane Instability
Center of Drag close to or in front of Center of Lift
Plane always wants to flip end over endInnate tendency makes the plane incredibly maneuverableOnly computerized control can keep it levelAll new fighter planes are robot planesSlide15
Helicopters
Design space:
Many existing RC helicopter kits, VERY DIFFICULT to make autonomous. Quadrotors are the way to go.Designing a classic helicopter from scratch is incredibly difficult, quadrotor
much less so
Bare minimum for robot control: Attitude sensing, inertial measurement, fine motor control
Existing robots:
Firescout
,
Draganflyer
, Parrot
AR.Drone
Parrot
AR.Drone
Fire Scout
Draganflyer
IIISlide16
Helicopter StabilitySlide17
Helicopter Stability
It seems stable, but…
Huge amount of lift is required to keep a mass in the airWhen that lift is redirected, mass both:DropsMoves sideways very quicklyHelicopters need to constantly vary throttle to stay level while maneuveringSlide18
Ornithopters
Design space:
Mechanical design hasn’t even been nailed down yet (though RC toys exist), good luck making a robot out of one. On the other hand, you could get a thesis out of it…Bare minimum for robot control: …?Existing robots:
MIT Robot Locomotion Group
Ornithopter
Project,
Festo
Ornithopter
Festo
Ornithopter
Skybird
OrnithopterSlide19
Ground LocomotionSlide20
Ground Locomotion
Wheels
One or more wheels are used to roll over terrain. Multiple wheels, body configurations and suspension used to cover broken terrain.Turning wheels in place or spinning wheels in opposite directions used to control orientationTracks
Tracks composed of multiple links wrapped around pulleys and form one continuous mobile surface
Spinning tracks in opposite directions used to control orientation
Legs
One or more legs are used to step over terrain. Multiple legs and control styles are used to cover broken terrain.
Stepping in an appropriate pattern used to control orientationSlide21
Wheels
Design space:
Tons and tons and tons and tons of wheeled robot kits. Lots of fun design space – 95% of kits can’t make it over any terrain, though.Designing a wheeled vehicle is incredibly easy, and designing one for rough terrain is both fun and relatively simple.
Bare minimum for robot control:
None.
Existing robots
:
NASA rovers, Crusher, DARPA Grand Challenge cars, 80% of hobby robot kits
Crusher
Spirit Rover
3piSlide22
Design Exercise!
How do you design a wheeled vehicle to traverse a bump as large as its wheels?Slide23
Tracked
Design space:
Very few tracked robot kits, but it is possible to make your own using simple components.
Designing a real tracked vehicle requires a lot of time and manufacturing, but can be done. Taking some shortcuts can simplify the process.
Bare minimum for robot control: None.
Existing robots:
Ripsaw,
Packbot
, MAARS, Talon, many
Battlebots
Ripsaw
Packbot
MAARSSlide24
Design Exercise!
What happens to a tracked vehicle trying to traverse the same bump from the previous question?Slide25
Design Question?
Why would you pick tracks over wheels, or vice versa?Slide26
RipsawSlide27
PackbotSlide28
Legs
Design space:
Small is easy, big is hard. There are tons of little robot kits, but they’ll all cost a lot of money since they use so many motors.Designing a 6-legged walker is challenging and pays off; designing a 4-legged walker is hard but can be done; designing a 2-legged walker is a total pain to get right.
Bare minimum for robot control:
All joint positions, to an exacting degree.
Existing robots
:
BigDog
,
Asimo
, Phoenix Hexapod,
Bioloid
, many legged hobby robotics kits
BigDog
Asimo
Phoenix
BioloidSlide29
Legged Locomotion Topics
Polygon of Support and Center of Pressure
Dynamic and Static BalanceForce control and position controlSpring-Loaded Inverted Pendulum (SLIP)GaitsSlide30
Polygon of Support/
Center of Pressure
Polygon of Support:The stable shape defined by the outer edges of a body’s contact with the groundCenter of Pressure:The center of force from the ground, pushing up on a bodySlide31
Dynamic Balance/
Static Balance
Static Balance:Keeping your center of mass projected onto your polygon of support, and your center of pressure as aligned with your center of mass projection as possible.Dynamic Balance:Relying on multiple footfalls or a dynamically changing center of pressure to maintain balance. Slide32
Force Control/
Position Control
Position control:Control of trajectories and exact positions at all times, with forces and velocities resulting from desired positionsForce control:Control of force at all times, with positions and velocities resulting from desired forces
What do we do as human beings?Slide33
Inverted PendulumsSlide34
Gaits
Gait:
What legs you put down in what orderSlide35
GaitsSlide36
Design Challenge!
Design a gait for a four-legged animal and execute it.
Design a gait for a six-legged animal and execute it.Fastest team to run the length of the building outside wins.Rules:
Team must stay a cohesive, connected whole throughout the entire run
Footfall patterns must be repeated throughout the run. No changing gaits on the fly!
Teams get three attempts per animal type