Robotic Locomotion Howie Choset 16-311

Robotic LocomotionHowie Choset

16-311

Design Tradeoffs with Mobility Configurations

• Maneuverability• Controllability• Traction• Climbing ability• Stability• Efficiency• Maintenance• Environmental impact• Navigational considerations• Cost• Simplicity in implementation and deployment• Versatility• Robustness

Differential Drive

Where D represents the arc length of the center of the robotfrom start to finish of the movement.

Pictures from “Navigating Mobile Robots:Systems and Techniques” Borenstein, J.

Differential Drive (continued)

Advantages:• Cheap to build• Easy to implement• Simple design

Disadvantages:• Difficult straight line motion

Photo courtesy of Nolan Hergert

Problem with Differential Drive: Knobbie Tires

Changing diameter makes for uncertainty in dead-reckoning error


Skid Steering

Advantages:•Simple drive system

Disadvantages:•Slippage and poor odometry results•Requires a large amount of power to turn

Synchro Drive

Advantages:•Separate motors for translation and

rotation makes control easier•Straight-line motion is guaranteed mechanically

Disadvantages:•Complex design and implementation


Distributed Actuator Arrays:Virtual Vehicle

• Modular Distributed Manipulator System• Employs use of Omni Wheels

Omni Wheels

Advantages:•Allows complicated motions

Disadvantages:•No mechanical constraints to require straight-line motion•Complicated implementation


NourkbashMason

Morevac

Morevac

Airtrax

They say that omniwheels don’t have problems….

Make a Coaster with Omniwheels

Tricycle

Advantages:•No sliding

Disadvantages:•Non-holonomic planning required


Ackerman Steering

Advantages:Simple to implement•Simple 4 bar linkage controls

front wheels

Disadvantages:•Non-holonomic planning required


Magnets? (Paint Stripping/Bares)

Are wheels good?

• Power efficient

• Constant contact with (flat) ground (no impacts)

• Easy and inexpensive to construct

• Easy and inexpensive to maintain

• Easy to understand

• Minimal steady-state inertial effects

Can only go on flat terrains?

Rocker Bogie

http://www.robotthoughts.com/index.php/lego/archives/2007/07/20/lego-nxt-rocker-bogie-suspension/

http://www.huginn.com/knuth/blog/2007/06/24/lego-nxt-rocker-bogie-suspension/

Taken from Hervé Hacot, Steven Dubowsky, Philippe Bidaud

Why Robots and not people, now• Safety

– 30 probes sent to Mars in the last ten years

– Only 1/3 made it– Radiation

• Cost– Without life support and other needs, 1

million dollars per pound– 900 pounds of food per person– MER $820 million total (for both rovers)

$645 million for design/development + $100 million for the Delta launch vehicle and the launch + $75 million for mission operations

• Return– Fuel– Landing

Spirit and Opportunity• The rovers can generate power with their solar panels and store it in their

batteries. • The rovers can take color, stereoscopic images of the landscape with a pair of

high-resolution cameras mounted on the mast. • They can also take thermal readings with a separate thermal-emission

spectrometer that uses the mast as a periscope. • Scientists can choose a point on the landscape and the rover can drive over to it.

The rovers are autonomous -- they drive themselves • The rovers can use a drill, mounted on a small arm, to bore into a rock. This drill

is officially known as the Rock Abrasion Tool (RAT). • The rovers have a magnifying camera, mounted on the same arm as the drill, that

scientists can use to carefully look at the fine structure of a rock. • The rovers have a mass spectrometer that is able to determine the composition of

iron-bearing minerals in rocks. This spectrometer is mounted on the arm, as well.

• Also on the arm is an alpha-particle X-ray spectrometer that can detect alpha particles and X-rays given off by soil and rocks. These properties also help to determine the composition of the rocks.

• There are magnets mounted at three different points on the rover. Iron-bearing sand particles will stick to the magnets so that scientists can look at them with the cameras or analyze them with the spectrometers.

• The rovers can send all of this data back to Earth using one of three different radio antennas.

Sprit (1/4/4)

More Pictures from Spirit

Rocker Bogie

Lunakod: Were we first?

1969 Lunokhod 1A was destroyed at launch1970 Lunokhod 1landed on the moon 1973 Lunokhod 2 landed on the moon

In 322 days, L1 traveled 10.5kmBoth operated 414 days, traveled 50kmIn 5 years, Spirit and Opportunity 21km

Did they find it? (Russian)

Marsakhod

Articulated Drive:Nomad

Advantages:•Simple to implement except for turning mechanism

Disadvantages:•Non-holonomic planning is required

Internal Body AveragingMotors in the wheels

UGCV (Crusher) [Bares/Stentz, REC]

IRobot, Packbot

Dragon runner (Schempf, REC)

Gyrover (Brown and co.)

Ball Bot, Hollis

“A Dynamically stable Single-Wheeled Mobile Robot with Inverse Mouse-Ball Drive."

Challenge for next Lab

Framewalker: Jim2

Advantages:•Separate actuation of translation

and rotation•Straight-line motion is guaranteed

mechanically

Disadvantages:•Complex design and implementation•Translation and rotation are excusive

Legged Robots

Advantages:•Can traverse any terrain a human can

Disadvantages:•Large number of degrees of freedom•Maintaining stability is complicated

Are legs better than wheels?

Dante II

Honda Humanoid

Raibert’s Robots (First ones)

3D Hopper, CMU/MIT, 1984

actively balanced dynamic locomotion could be accomplished with simple control algorithms.

3D Biped, MIT, 1989-1995

Passive dynamics to help with maneivers

More Raibert robots• Quadruped, 1984-1987

• Planar Quadruped (Hodgins, 1985-1990)

RHexKodischek, Buhler, Rizzi

Act like wheels……compliance…

Sprawlita, Cutkowsky

Big Dog, Boston Dynamics

http://video.google.com/videoplay?docid=5349770802105160028&q=robot+raibert

Quadruped robot that walks, runs, and climbs on rough terrain and carries heavy loads.

Powered by a gasoline engine that drives a hydraulic actuation system.

Legs are articulated like an animal’s, and have compliant elements that absorb shock and recycle energy from one step to the next.

Size of a large dog or small mule, measuring 1 meter long, 0.7 meters tall and 75 kg weight.

Benefits of Compliance: Robustness

• Handle unmodeled phenomena• Regulate friction (e.g. on textured surfaces)

• Minimize large forces due to position errors• Overcome stiction• Increase grasp stability• Extra passive degree of freedom for rolling • Locally average out normal forces (provides uniform pressure,

no precise location)• Lower reflected inertia on joints [Pratt]• Energy efficiency (probably not for snakes)

Whegs, Quinn

No compliance….

SNAKE ROBOTS: Many DOF’shttp://snakerobot.com

• Thread through tightly packed volumes

• Redundancy• Minimally invasive• Enhanced mobility• Multi-functional

Thanks to JPL

Hyper-redundant MechanismsMobile-trunk Free-crawling

RoadmapsSLAM

Coverage

Bio

log

yR

ob

oti

c

ConnectionsReduction

Scaled MomentumGait generation

Manipulation

Climbing: Contact

DistributedManipulation

(J. Luntz)

OmniTread

SAIC/CMU

SARCOS

• Still looking

Biologically Inspired Gait #1:Linear Progression

http://youtube.com/watch?v=xUQ_SMCCPN4

Biological Snakes

•Anchors at sites - travel backwards•Symmetric movement in axial direction•Anteroposterior flexible skin •Momentum is conserved as the snake travels at a fairly constant speed/little drag

Biologically Inspired Gait #2: Sidewinding

http://video.nationalgeographic.com/video/player/specials/most-watched-specials/adder_peringuays_kids.html

Lateral Undulation

http://www.youtube.com/watch?v=sembodyhZUo

Biological Snakes

Gans

•*Energy Efficiency compared to tetrapods

•Jayne – comparable

•Gans/Chodrow&Taylor – more

•High endurance

Concertina Locomotion

Biological Snakes Robotic Snakes

•Uses static friction•Energy inefficient (7X)* due to stop and go movement•Tree climbers use some form of concertina

*Jayne

Concertina in 3DHirose

Gans

NXT Snake

Are snakes better than legs?

Helicopter Lab

First autonomous helicopter using vision.Best dynamic performance for “big” helicopters.Best digital terrain maps. 13 cm accuracy. Mapped flight 93 site.

DepthX Wettergreen, Kantor, Fairfield, NASA

ShallowX: Kantor, Choset

Robotic Locomotion Howie Choset 16-311

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