Robotic Locomotion Howie 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 Pictures from “Navigating Mobile Robots: Systems and Techniques” Borenstein, J. Where D represents the arc length of the center of the robot from start to finish of the movement.

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

Distributed Actuator Arrays: Virtual Vehicle Modular Distributed Manipulator System Employs use of Omni Wheels

Omni Wheels Nourkbash Advantages: Allows complicated motions Mason Pictures from “Navigating Mobile Robots: Systems and Techniques” Borenstein, J. Morevac Morevac Advantages: Allows complicated motions Disadvantages: No mechanical constraints to require straight-line motion Complicated implementation

Airtrax They say that omniwheels don’t have problems….

Make a Coaster with Omniwheels

Tricycle Advantages: Disadvantages: No sliding Pictures from “Navigating Mobile Robots: Systems and Techniques” Borenstein, J. 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 Pictures from “Navigating Mobile Robots: Systems and Techniques” Borenstein, J.

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 Taken from Hervé Hacot, Steven Dubowsky, Philippe Bidaud 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/

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? In 322 days, L1 traveled 10.5km 1969 Lunokhod 1A was destroyed at launch 1970 Lunokhod 1landed on the moon 1973 Lunokhod 2 landed on the moon In 322 days, L1 traveled 10.5km Both operated 414 days, traveled 50km In 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 Averaging Motors 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 ? Are legs better than wheels? 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)

RHex Kodischek, Buhler, Rizzi Act like wheels……compliance…

Sprawlita, Cutkowsky

Big Dog, Boston Dynamics 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. http://video.google.com/videoplay?docid=5349770802105160028&q=robot+raibert

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’s http://snakerobot.com Thread through tightly packed volumes Redundancy Minimally invasive Enhanced mobility Multi-functional Thanks to JPL

Hyper-redundant Mechanisms Mobile-trunk Free-crawling Manipulation Biology Robotic Connections Reduction Scaled Momentum Gait generation Roadmaps SLAM Coverage Climbing: Contact Distributed Manipulation (J. Luntz)

OmniTread

SAIC/CMU

SARCOS Still looking

Biologically Inspired Gait #1: Linear Progression 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 http://youtube.com/watch?v=xUQ_SMCCPN4

Biologically Inspired Gait #2: Sidewinding http://video.nationalgeographic.com/video/player/specials/most-watched-specials/adder_peringuays_kids.html

Lateral Undulation Biological Snakes Propulsion by summing the longitudinal resultants of posterolateral forces Momentum is conserved Efficiency* increases with lower sliding friction Used for traversing flat clear ground with some irregularities *Energy Efficiency compared to tetrapods Jayne – comparable Gans/Chodrow&Taylor – more High endurance Gans http://www.youtube.com/watch?v=sembodyhZUo

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 Gans *Jayne Concertina in 3D Hirose

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