Introduction to Robotics Ph.D. Antonio Marin-Hernandez Artificial - - PDF document

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Introduction to Robotics Ph.D. Antonio Marin-Hernandez Artificial - - PDF document

Mar 13, 2023 223 likes •513 views

4/15/20 Introduction to Robotics Ph.D. Antonio Marin-Hernandez Artificial Intelligence Research Center Universidad Veracruzana Sebastian Camacho # 5 Xalapa, Veracruz Robotics Action and Perception LAAS-CNRS 7, av du colonel Roche

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Introduction to Robotics

Ph.D. Antonio Marin-Hernandez

Artificial Intelligence Research Center Universidad Veracruzana Sebastian Camacho # 5 Xalapa, Veracruz Robotics Action and Perception LAAS-CNRS 7, av du colonel Roche Toulouse, France

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Topics

  • Introduction
  • Locomotion
  • Kinematics of Mobile Robots
  • Perception
  • Navigation
  • Localization
  • Path Planning
  • Task Planning

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Mobile Robots: Locomotion

  • Locomotion is the complement of

manipulation

  • Study of actuators that generate

interaction forces, and mechanisms that implement desired kinematic and dynamic properties.

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Mobile Robots: Locomotion

  • Locomotion and manipulation

share as issues:

–stability, –contact characteristics, and –environmental type.

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Mobile Robots: Locomotion

  • stability

–number and geometry of contact points –center of gravity –static/dynamic stability –inclination of terrain

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Mobile Robots: Locomotion

  • characteristics of contact:

–contact point/path size and shape –angle of contact –friction

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Mobile Robots: Locomotion

  • Type of environment

–Structure –medium (e.g. water, air, soft or hard ground)

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Mobile Robots: Locomotion

  • Theory of locomotion includes:

–Mathematics, –Mechanics –Physics

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Mobile Robots: Locomotion

  • To be able to do certain task a robot

must be able to move in the environment

  • Two main problems

–Given some inputs how the robot is going to move ? (kinematics) –Which inputs are required to move a robot to a given position or with desirable movement ? (inverse kinematics)

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Mobile Robots: Locomotion

  • The field of study where the forces

involved are modeled is Dynamics

–Energy and Forces associated with movements

  • Different Mobile Robots in:

–Terrestrial –Aquatic –Aerial –Space

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Mobile Robots: Locomotion

  • Legged Robots
  • Characterized by a series of contact points

between the robot and the ground.

  • Advantages: include adaptability and

maneuverability in rough terrain.

  • Disadvantages of legged locomotion

include power and mechanical complexity

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Mobile Robots: Locomotion

  • Legged Robots
  • Insects

–6 or more legs

  • Mammals and reptiles

–4 legs

  • Some mammals (Humans)

–2 legs

  • Humans can jump in one leg

–complex active control to maintain balance

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Mobile Robots: Locomotion

  • Legged Robots
  • Adding degrees of freedom to a robot leg

increases the maneuverability of the robot

  • Disadvantages:

– energy, control, and mass.

  • Additional actuators require energy and

control, and they also add to leg mass, further increasing power and load requirements on existing actuators.

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Mobile Robots: Locomotion

  • Legged Robots
  • The number of possible gaits depends on

the number of legs

  • The gait is a sequence of lift and release

events for the individual legs.

  • For a mobile robot with k legs, the total

number of possible events N for a walking machine is:

N = 2k −1

( )!

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Mobile Robots: Locomotion

  • Legged Robots
  • For a mobile robot with 2 legs, there are 6

possible events :

  • lift right leg, lift left leg
  • release right leg, release left leg
  • lift both legs together, release both legs

together.

N = 2k −1

( )!= 3!= 3⋅ 2⋅ 1 = 6

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Mobile Robots: Locomotion

  • Legged Robots

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Mobile Robots: Locomotion

  • Legged Robots

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Mobile Robots: Locomotion

  • Legged Robots
  • Static walking with six legs.
  • A tripod formed by three legs always exists.

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Mobile Robots: Locomotion

  • Legged Robots
  • Minimize the number of legs

–Mass –Legs coordination

  • Legged robots can cross a gap

–Easier when they have less legs –Jump and running

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Mobile Robots: Locomotion

  • Legged Robots
  • Two legged robots have been shown to:

–run, –jump, –travel up and down stairways, –and even do aerial tricks such as somersaults

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Mobile Robots: Locomotion

  • Legged Robots
  • Honda Asimo

HRP2, HRP3, HRP4

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Mobile Robots: Locomotion

  • Legged Robots
  • Sony Qrio

Toyota

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Mobile Robots: Locomotion

  • Legged Robots
  • Aldebaran NAO and ROMEO

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Mobile Robots: Locomotion

  • Legged Robots
  • Four legs
  • Standing is passively stable
  • Walking is challenging because to remain

stable the robot’s center of gravity must be actively shifted during the gait

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Mobile Robots: Locomotion

  • Legged Robots
  • Six legs
  • Static stability reducing the control

complexity

  • In most cases, each leg has three degrees
  • f freedom, including hip flexion, knee

flexion, and hip abduction

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • relatively simple mechanical implementation
  • balance is not (usually) a problem
  • all wheels are in ground contact
  • Other problems:

–traction and stability, –maneuverability, and –control

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • The four basic wheel types:
  • (a) Standard wheel: two degrees of

freedom; rotation around the (motorized) wheel axle and the contact point.

  • (b) castor wheel: two degrees of freedom;

rotation around an offset steering joint.

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • The four basic wheel types:
  • (c) Swedish wheel: three degrees of

freedom; rotation around the (motorized) wheel axle, around the rollers, and around the contact point.

  • (d) Ball or spherical wheel: realization

technically difficult.

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • Standard wheels and castor wheel

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • Swedish wheels

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • Balls or spherical wheels

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Mobile Robots: Locomotion

x Rotation y d

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • Small speeds d is negligible
  • We use odometry to estimate robot’s motion
  • Simple case, the distance traveled by the

wheel is:

–2πr

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • The Instantaneous Center of Curvature

(ICC) must coincide with the axes of rotation of each wheel in contact

  • ICC should not only exist, but each wheel

must describe a movement consistent with a rotation of the vehicle around the ICC

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Mobile Robots: Locomotion

ICC

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • A Wheeled robot in the plane has three

degrees of freedom

–(x, y, θ)

  • Position (x, y)
  • Orientation θ
  • The robot doesn’t have independent control
  • ver this DoF

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • Robot can’t change arbitrary their position
  • Changes depend on orientation

–Holonomic restrictions

  • Sometimes castor wheels are required

–Kinematics undone

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • We are going to focus on:

–Traction and stability –Maneuverability –Control

  • We are not deal with balance

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • The choice of wheel types for a mobile

robot is strongly linked to the choice of wheel arrangement, or wheel geometry

  • When design

–What type of wheels? and –Which geometry ?

  • The choices are in function of:

maneuverability, controllability, and stability.

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • Ackerman wheel configuration (used in

cars) is not a solution for mobile robots because it has poor maneuverability

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • 2 wheels
  • One steering wheel in the

front, one traction wheel in the rear

  • Two-wheel differential

drive with the center of mass (COM) below the axle

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • The minimum of wheel required to have

stability is two

  • Stability is achieved if the center of mass is

below the axis of the wheels

  • Under ordinary conditions, wheel diameter

is impractical

  • Robots with two wheels can hit the ground

due to torque

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • Static stability it is required 3 wheels
  • The center of gravity must be contained in

the triangle formed by the three contact points

  • Stability can be improved by adding more

wheels

–The hyper-static nature of geometry requires flexible suspension on roughly terrain

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • 3 wheels
  • Two-wheel centered

differential drive with a third point of contact

  • Two independently driven

wheels in the rear/front, 1 unpowered

  • mnidirectional wheel in

the front/rear

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • 3 wheels
  • Two connected traction

wheels (differential) in rear, 1 steered free wheel in front

  • Two free wheels in rear,

1 steered traction wheel in front

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • 3 wheels
  • Three motorized Swedish or

spherical wheels arranged in a triangle; omnidirectional movement is possible

  • Three synchronously

motorized and steered wheels; the orientation is not controllable

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • 4 wheels
  • Two motorized wheels in the rear,

2 steered wheels in the front; steering has to be different for the 2 wheels to avoid slipping/skidding.

  • Two motorized and steered

wheels in the front, 2 free wheels in the rear; steering has to be different for the 2 wheels to avoid slipping/skidding.

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • 4 wheels
  • Four steered and motorized

wheels

  • Two traction wheels

(differential) in rear/front, 2

  • mnidirectional wheels in the

front/rear

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • 4 wheels
  • Four omnidirectional wheels
  • Two-wheel differential drive

with 2 additional points of contact

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • 4 wheels
  • Four motorized and steered

castor wheels

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Mobile Robots: Locomotion

  • Wheeled Mobile Robots
  • 6 wheels
  • Two motorized and steered

wheels aligned in center, 1

  • mnidirectional wheel at

each corner

  • Two traction wheels

(differential) in center, 1

  • mnidirectional wheel at

each corner

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  • Maneuverability
  • Omnidireccional robots
  • Swedish or spherical wheels

Mobile Robots: Locomotion

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  • Maneuverability
  • Four drive castor wheels
  • All controlled in traction and turn

Mobile Robots: Locomotion

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Mobile Robots: Locomotion

  • Maneuverability
  • Pioneer by Adept Robotics

(former Active Media Robotics)

  • PR2 by Willow Garage

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  • Maneuverability
  • Four drive castor wheels
  • All controlled in traction and turn

Mobile Robots: Locomotion

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