Introduction to Robotics

MECE 551

Winter 2009

What is the definition of a 'robot'?

"A reprogrammable, multifunctional

manipulator designed to move

material, parts, tools, or specialized

devices through various programmed

motions for the perform

ance of a

variety of tasks" Robot Institute of

America, 1979

Robotic systems:

1.

Manipulators

2.

Mobile robots

3.

Integrated robotic systems

MANIPULATORS -Industrial robots:

MANIPULATORS -Industrial robots:

MANIPULATORS: High speed robotics:

Microsurgery using telerobotics(NASA-JPL)

RAMS (Robot-Assisted M

icro-

Surgery) system has been developed

to utilize NASA telerobotics

technology for eye surgery.

The system provides scaled-down

human-input motions, tremor filtering

to improve precision, amplified forces

fed back to the human operator, and

programmable constrained m

otion of

the instrument in the eye to m

inim

ize

surgical im

pacts.

MANIPULATORS: Special applications

Microinjection using piezoimpact drive mechanism

It is necessary to insert a m

icro pipette into the cytoplasm in case of

sperm

injection or DNA transplantation.

MANIPULATORS: Special applications

�Provide m

ovements instead of manipulation

�Several different mechanisms for movability

�Dynamics of the m

otion (stability)

�Mobility control

�Sensing and feedback

�Navigation

Mobile robots: wheeled or biped

Mobile robots: multi-leg mechanisms

Boston D

ynamics

Mobile robots: climbing machines

Boston D

ynamics

Smart drug delivery robots

driven by MRI systems: (Ecole

PolytechniqueMontreal)

Micro/(Nano?) Mobile robots:

Endoscopic micro capsules:

Nanorobitcslab, CMU

1.Design and Kinematics analysis of mechanisms

2.Dynamic m

odeling and analysis of multi-body systems

3.Motion planning and control

4.Vision and image processing

5.Sensor design and data diffusion

6.Navigation

7.Intelligence and autonomy

8.Cooperative systems

….

Robotics is a multi-disciplinary science:

,

, ,

43

21

θθ

θθ

1.Degrees of freedom: the number of independent

coordinates that represent a unique configuration

of the robot

2.Configuration space or joint space: the space

of all possible configurations (e.g. spanned by

)

3.Workspace:the space which can be reached by

the end-effector. Usually presented by Cartesian

coordinates: X, Y, Z and orientation angles

4.Kinematics and Dynamics

Frequently used term

s:

End-effector

5.Joint coordinatesvs. end-effector coordinates

6.Actuators: power elements to deliver a prescribed m

otion to the joint coordinates

7.Accuracy: absolute accuracy in the positioning of the end-effector

8.Repeatability: accuracy in repeating a m

otion (which is m

ore important than absolute

accuracy for industrial applications)

9.Path planning: design of the geometrical path of motion for the end-effector. It can be

presented in configuration space or workspace

10.Trajectory: timed path of the m

otion

Frequently used term

s:

Joint

coordinates

Joint coordinates

1.

Serial manipulators: made of several links connected in series (serial chain kinematic)

•Large workspace

•Sim

ple structure

•Decoupled joint motion => sim

ple kinematics and control

•Low structural stiffness => high induced vibration

•Large m

oving inertia

Architecture of robot manipulators:

2.

Parallel manipulators: built of several closed kinematic loops. Actuators work in a

parallel manner (vs. being in series such as in serial manipulators)

•Higher stiffness => better accuracy

•Lower inertia => higher speeds

•Smaller workspace

•More complex kinematics and control

Architecture of robot manipulators:

Stewart-Gough platform

Flight simulator

Hexarobot

Motion of a kinematic chain depends on the

characteristics of its joints

Kinematic joints:

2. Prismatic (1 DoF)

3. Cylindrical (2 DoF)

4. Spherical (3 DoF)

5. Helical (1 D

oF)

1. Revolute (1 D

oF)

Grubler’sequation:

: Number of degrees of freedom

: Dim

ension of the m

otion space (the space

in which the mechanism is supposed to

function)

: Number of the links including the fixed link

: Number of the joints

: Degrees of freedom of the ithjoint

Mechanisms: Degree of freedom

∑ =

+−

−=

j

i

ifj

nF

1

)1(

λ

F λ n j if

Mechanisms: Degree of freedom

33

0)

11

1()

13

4(6

=+

=+

++

−−

=F

Examples:

∑ =

+−

−=

j

i

ifj

nF

1

)1(

λ

2)

11

11

1()

15

5(3

=+

++

++

−−

=F

∑ =

+−

−=

j

i

ifj

nF

1

)1(

λ

Mechanisms: Degree of freedom

Examples:

12

)3

12

6()

118

14

(6

=×

++

−−

=F

But there are 6 dummy D

oFdue to the twist

of the cylinders. Therefore

F = 12 –6 = 6

∑ =

+−

−=

j

i

ifj

nF

1

)1(

λ

Engineering of a typical robotic system:

Kinematics and dynamics

Velocity, Jacobianstatic and

stiffness analysis

Controller design

Path and trajectory planning (motion planning)

Image processing, object recognition (robot

vision) not to be studied in this course!

Machine intelligence, autonomy, etc.

Robotic system: the general block diagram

Task Planner

Geometric Path

Generator

Trajectory

Generator

Controller or

Trajectory

Tracker

Robot

Sensors

Required Task

An ordered set

of points in

Cartesian space

(control points)

Param

eterized path in

the joint space

Tim

e history of

position, velocity and

acceleration

(1)

(2)

(3)

(4)

(Motionplanning algorithm

)