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
)