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Robotics. R&N: ch 25. based on material from Jean-Claude Latombe, Daphne Koller, Stuart Russell. sensors. environment. ?. agent. effectors. Agent. Robots  Physical sensors and effectors. Sensors. Sensors that tell the robot position/change of joints: odometers, speedometers, etc.

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robotics

Robotics

R&N: ch 25

based on material from Jean-Claude Latombe, Daphne Koller, Stuart Russell

agent

sensors

environment

?

agent

effectors

Agent

Robots  Physical sensors and effectors

sensors
Sensors
  • Sensors that tell the robot position/change of joints: odometers, speedometers, etc.
  • Force sensing. Enables compliant motion--robot just maintains contact with object (video: compliant)
  • Sonar. Send out sound waves and measure how long it takes for it to be reflected back. Good for obstacle avoidance.
  • Vision systems
effectors
Effectors
  • Converts software commands into physical motion
  • Typically electrical motors or hydraulic/pneumatic cylinders
  • Two main types of effectors:
    • locomotion
    • manipulation
locomotion
Locomotion
  • Legs!
    • traditional (video: honda human)
    • Other types
      • Statically stable locomotion: can pause at any stage during its gate without falling
      • Dynamically stable locomotion: stable only as long as it keeps moving (video: hopper)
  • Still, wheeled or tread locomotion like Shakey is still most practical for typical environments
  • Other methods: reconfigurable robots, fish robots, snake-like robots. (video: mod-robot)
manipulation
Manipulation
  • Manipulation of objects
  • Typical manipulators allow for:
    • Prismatic motion (linear movement)
    • Rotary motion (around a fixed hub)
  • Robot hands go from complex anthromorphic models to simpler ones that are just graspers
    • (video: manipulation)
    • (video: heart surgery)
problems in robotics
Problems in Robotics
  • Localization and Mapping
  • Motion planning
localization where am i
Localization: Where Am I?
  • Use probabilistic inference: compute current location and orientation (pose) given observations

At-1

At-1

At-1

Xt-1

Xt-1

Xt-1

Zt-1

Zt-1

Zt-1

motion planning
Motion Planning
  • Simplest task that a robot needs to accomplish
  • Two aspects:
    • Finding a path robot should follow
    • Adjusting motors to follow that path
  • Goal: move robot from one configuration to another
configuration space
Configuration space
  • Describe robot’s configuration using a set of real numbers
  • Flatland -- robot in 2D -- how to describe?
  • Degrees of freedom: a robot has k degrees of freedom if it can be described fully by a set of k real numbers
    • e.g. robot arm (slide)
  • Want minimum-dimension parameterization
  • Set of all possible configurations of the robot in the k-dimensional space is called the configuration space of the robot.
example
Example
  • workspace for 2-D robot that can only translate, not rotate
  • configuration space describes legal configurations
    • free-space
    • obstacles
  • Configuration space depends on how big robot is—need reference point
path planning
Path planning
  • Goal: move the robot from an initial configuration to a goal position
  • path must be contained entirely in free space
  • assumptions:
    • robot can follow any path (as long as avoids obstacles)
    • dynamics are completely reliable
    • obstacles known in advance
    • obstacles don’t move
assumption 1
Assumption #1
  • robot can follow any path
  • what about a car?
  • degrees of freedom vs. controllable degrees of freedom
    • holonomic (same)
    • nonholonomic
    • (video: holonomic)
motion planning14
Motion planning
  • reduces to problem of finding a path from an initial state to a goal in robot’s configuration space
  • why is this hard?
reformulate as discrete search
Reformulate as discrete search
  • finely discretized grid
  • cell decomposition: decompose the space into large cells where each cell is simple, motion planning in each cell is trivial
  • roadmap (skeletonization) methods: come up with a set of major “landmarks” in the space and a set of roads between them
issues in search
Issues in Search
  • Complete
  • Optimality
  • Computational Complexity
motion planning algorithms
Motion planning algorithms
  • grid
  • cell decomposition
    • exact
    • approximate
  • roadmap (skeletonization) methods:
    • visibility graphs
    • randomized path planning
robotics summary
Robotics: Summary
  • We’ve just seen a brief introduction…
  • Issues:
    • sensors, effectors
    • Locomotion, manipulation
  • Some problems:
    • Localization
    • Motion Planning
  • Lots more!!
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