TMPT06
Robot Technology
Luis Ribeiro (luis.ribeiro@liu.se)
IEI – Manufacturing Engineering
Robot Technology
Electrical Engineering
Production
Mechatronics
Mechanical Engineering
System Engineering
Robotics
Computer
Science
Control
Theory
Mathematics
2
System and Signal
Analysis
Physics
What will you learn in this part of the course?
• The main architectural aspects of a robot and its controller.
• The main performance indicators of robot.
• The main concepts and terminology in the field of robotics from
a manufacturing engineering perspective
• The methods for robot programming:
•
Offline
•
Online (focus of the practical exercise)
• Main safety requirements
3
Industrial Robots
Why Studying Industrial Robots:
• It is an emerging and challenging research area
•
It is a very important component in automated systems!
Robots improve:
•
Productivity
•
Quality (specially in some processes due to high repeatability and
accuracy)
•
Work environment (by removing human from hazardous
environments)
4
Potential Additional Costs
Examples of costs that may apply are:
- The cost of custom tray material supply needs.
- The cost of fixtures.
- The cost of achieving an automatic cycle, for example,
automation of inspection, measurement, or other operations
that the operator normally performs in a manual method.
5
Flexibility and Industrial Robots
Variant Flexibility –
reconfigurability between product
variants
Product Flexibility – Rebuild
Flexibility
Capacity Flexibility – Volume
Flexibility
REF. http://mtm-international.org/wpcontent/uploads/2013/12/int-19.png
6
The statistics – Shipments of Industrial Robots
7
The Statistics – By Industry
8
The statistics - Expected
9
Where are industrial robots normally used?
Welding
10
Where are industrial robots normally used?
Water jet
Cutting
Ref. ABB Robotics
11
Where are industrial robots normally used?
Packaging
Ref. ABB Robotics
12
Where are industrial robots normally used?
Painting
Ref. ABB Robotics
13
Where are industrial robots normally used?
Assembly
14
What is a robot then?
Industrial robot as defined by ISO 8373:
An automatically controlled, reprogrammable, multipurpose manipulator
programmable in three or more axes, which may be either fixed in place or
mobile for use in industrial automation applications.
Physical alterations: alteration of the mechanical
structure or control system except for changes of
programming cassettes, ROMs, etc.
Reprogrammable: whose programmed motions or auxiliary
functions may be changed without physical alterations;
Multipurpose: capable of being adapted to a
different application with physical alterations;
Axis: direction used to specify the robot motion
in a linear or rotary mode
REF: http://www.ifr.org/industrial-robots/
15
Robot and Its Controller
Robot
Controller
Robot
Teach
Pendat
REF: http://www.kuka-robotics.com/en/company/
16
Robot Architecture (Simplified Model)
Control signals
Motor
Gear
Joint
I
N
T
S
E
N
S
O
R
S
C
O
M
P
U
T
E
R
Robot model
Environment
model
Task model
Control
Algoritm
Computer- language
E
X
T
Environment
17
S
E
N
S
O
R
S
Task
ref. Coiffet & Chirouze
Control system
Manual control
Stored programs
Stored paths
The Control Flow
Path planning
Direct kinematics
Inverse
kinematics
Mechanical arm
Servo
Motor
Internal sensors
Gearbox etc
Joint
The arm is composed of a number of links
Gripper/tool
Gripper / sensors
Workpiece
External sensors
Fixtures etc
18
Do consider that some of the
interactions are mechanic while
others are electrical/electronic
Exploring the Mechanical Arm (Joint)
Servo
Motor
Internal sensors
Gearbox etc
Joint
The arm consists of a number of joints
The block diagram for the mechanical arm. Note that there is a number of
links in the arm, in series or in parallel.
19
Mechanical arm - open kinematic chains
Cartesian robot arm – PPP
Cylindrical robot – RPP
Spherical robot – RRP
Examples of open end chains. In the English
literature the P stands for Prismatic and the
R for Revolute.
Revolute robot - RRR
20
Mechanical arm - closed kinematic chains
Ref. ABB Robotics
21
One example showing a robot with parallel
build up for the main movements. The wrist is
equipped with serial kinematics. This type of
robot is used for machining and assembly
(ref. NEOS Robotics).
Closed Kinematic
ABB Irb 340 ”FlexPicker”
The robot is fast and can perform
150 handling per minute, the robot
can pick up one part, move it
to the new position and release it
in 0.4 s.
It can be integrated with
computer vision for the detection
of the pick up and release positions.
Pick up can also be performed
from and to moving conveyors.
Ref. ABB Robotics
22
Process performance with IRB 340
•
More than 150 picks / minute
– Single pick and place
– Multiple conveyor tracking
187
– Vision recognition
Pick Rates PickMaster/IRB340
100 g
500 g
1000 g
2000 g
200
180
187
182
170
150
160
130
150
140
139
130
Pick Rate [ppm]
127
120
118
117
118
118
107
107
100
97
86
80
74
65
60
40
Includes:
Pick and place time 0.35s each
Double conveyor tracking
Ref. ABB Robotics
23
20
0
25/100/25
25/305/25
25/500/25
Cycle Length [mm]
25/700/25
Exploring the Mechanical Arm (Joint)
Motors
•
pneumatic
•
oil hydraulic
•
electric
Servo
Motor
Internal sensors
Gearbox etc
24
Gear boxes
•
ball screw
•
harmonic drive
•
CYCLO
•
planet gear
•
gear wheel drive
•
others
Joint
The arm consists of a number of joints
Motors & Gear Boxes
Motors
Gear boxes
- pneumatic
- oil hydraulic
- electric
- ball screw
- harmonic drive
- CYCLO
- planet gear
- gear wheel drive
- others
Piston type &
rotary type
+
high effect/volume ratio
low cost
-
hard to control due
to air compressability
Motors & Gear Boxes
Motors
Gear boxes
- pneumatic
- oil hydraulic
- electric
- ball screw
- harmonic drive
- CYCLO
- planet gear
- gear wheel drive
- others
Piston type &
rotary type
+
high effect/volume ratio
-
expensive
high maintenance cost
expensive to install piping
precision due to
temperature variation
Motors & Gear Boxes
Motors
Gear boxes
- pneumatic
- oil hydraulic
- electric
- ball screw
- harmonic drive
- CYCLO
- planet gear
- gear wheel drive
- others
(Stepper motors)
DC servo drives
AC servo drives
+
low price
low maintenance
easy to install
-
low effect/volume ratio
Motors & Gear Boxes
Motors
- pneumatic
- oil hydraulic
- electric
Gear boxes
- ball screw
- harmonic drive
- CYCLO
- planet gear
- gear wheel drive
- others
Motors & Gear Boxes
Motors
- pneumatic
- oil hydraulic
- electric
Gear boxes
- ball screw
- harmonic drive
- CYCLO
- planet gear
- gear wheel drive
- others
Motors & Gear Boxes
Motors
- pneumatic
- oil hydraulic
- electric
Gear boxes
- ball screw
- harmonic drive
- CYCLO
- planet gear
- gear wheel drive
- others
Motors & Gear Boxes
Motors
- pneumatic
- oil hydraulic
- electric
Gear boxes
- ball screw
- harmonic drive
- CYCLO
- planet gear
- gear wheel drive
- others
Motors & Gear Boxes
Motors
- pneumatic
- oil hydraulic
- electric
Gear boxes
- ball screw
- harmonic drive
- CYCLO
- planet gear
- gear wheel drive
- others
Motors & Gear Boxes
Motors
Gear boxes
- pneumatic
- oil hydraulic
- electric
- ball screw
- harmonic drive
- CYCLO
- planet gear
- gear wheel drive
- others
i.e. steel belt drive
belt drive
gear belt drive
Exploring the Mechanical Arm (Joint)
Analog
Digital
Servo
Absolute
Incremental
Motor
Internal sensors
Gearbox etc
Joint
The arm consists of a number of joints
34
Position (angular position)
Velocity (angular velocity)
Accelaration
Force
Robot Programming
Control system
Manual control
Stored programs
Stored paths
Path planning
Direct kinematics
Inverse kinematics
Servo
Robot Programming
There are many ways of programming a robot
Teach method (using the teach pendant)
•
The robot is displaced through the several points and the different positions are
memorized.
•
Easy to learn and use!
Walkthrough
•
The user teaches the robot the exact trajectories by displacing it physically.
•
Extremely easy to use and has a good trajectory control.
•
Uses a considerable amount of memory (all the points in the trajectory are memorized).
•
Difficult to characterize the trajectories.
Offline
•
The robot program is developed in a specific environment.
•
Programs can be generated automatically using a simulation model.
•
Programming does not require stopping the robot
36
Robot Programming
Robot Programming Languages offer a set of functions that affect the positioning of
the robot.
Typically robot movement can happen different coordinates:
• Joint Space Coordinates - as a function of the joint movement
• Cartesian Space Coordinates - as a function of a “world “ reference frame.
• Tool Space Coordinates - as a function of the reference frame associated with the
tool.
• Object Space Coordinates - as a function of the reference frame associated with a
specific object.
Movement can be absolute or relative and the trajectory can be controlled:
•
Linear Movement
•
Circular Movement
•
Contour following
37
TCP
The positioning is
normally defined in
respect to the TCP.
Tool Center Point - TCP
Tool-Center-Point. The manual control of the robot is decoupled in a positioning part
and rotational part in a pre-programmable TCP.
38
Forward and Inverse Kinematics
39
Denavit-Hartenberg Transformations
40
How to setup the reference frames?
• Zi is always defined along the robot joint.
• The sense of Zi is arbitrary.
• Zi is associated with the i+1 joint, hence Z0 is associated with
the first joint.
• The Z axis must be along the joint in Z0.
• The origin of each reference frame should be placed where the
common normal between Zi and Zi-1 intersects Zi . If Zi and Zi-1
are parallel then the origin can be placed in any position along
the Z axis.
• Xi is placed along the common normal between Zi and Zi-1 or in
the direction normal to the plane Zi - Zi-1 if Zi and Zi-1 intersect.
41
Application to the PUMA robot
42
43
44
45
Rotary Encoders
Rotating
shaft
Motion Sensor and
encoding
mechanism
46
The detection of
motion can be:
•Optical
•Mechanical
•Magnetic
Mechanical Rotary Encoders
REF:
http://www.robotroom.c
om/Counter5.html
“The printed pattern of teeth is what causes a repeating output
pattern such as: A on / B on, A off / B on, A off / B off, A on / B off. If
the dial is turned in the opposite direction, the pattern is reversed.”
47
Magnetic Encoders
The rotating disc denotes different sectors
featuring different polarizations.
The electro-magnetic variations detected by the
pick up enable the measurement.
Hall effect - pick-ups use a semiconducting
sensing element that relies on the Hall effect to
generate a pulse for every gear tooth that
passes the pickup.
Variable reluctance - pick-ups use a simple coil of wire
in the magnetic field. As the gear teeth pass by the pickup and disturb the flux, they cause a change in the
reluctance of the gear/magnet system. This induces a
voltage pulse in the sensing coil that is proportional to
the rate flux change.
REF: http://www.ni.com/white-paper/4500/en/
48
Optical Encoders
One or more leds
emit light that
either passes
through or is
blocked by a
marked disc.
REF: http://machinedesign.com/sensors/basics-rotaryencoders-overview-and-new-technologies-0
49
Optical vs Magnetic
REF:http://www.globalspec.com/learnmore/sensors_transducers_d
etectors/encoders_resolvers/encoder_absolute_rotary
50
Absolute vs Incremental Encoders
Absolute Encoders provide
persitent positionning
information
REF: http://www.electro-labs.com/rotary-encodersunderstanding-practical-implementation/
51
Incremental
Encoders
require
additional equipment to keep track
of position as they mainly count the
variation in the marks of the
encoding disc
Additional sensors can provide further
information
Built in sensor for generating
search stop
Gripper
Robot arm
Search in magasin
Part
Stack of parts in magasin
Example: search movement along a line in a stack magasin
52
Additional sensors can provide further
information
The Robot Velocity
is adjusted when
the force changes
Robot Arm
Rotating Deburring Tool
Workpiece
53
Sensor for sensing the
processing force
Burr to be removed
Sensors
Capacitive Sensors
REF:
http://www.auto
mationdirect.com/
adc/Overview/Cat
alog/Sensors_-z_Encoders/Capacit
ive_Proximity_Sen
sors
Force and torque
sensors.
REF:
http://www.directi
ndustry.com/prod/
schunk/load-cellstorque-function-6axis-12463903013.html
54
Vision Sensors
REF:
http://robohub.or
g/vision-sensorcapable-ofdetecting-movingspots-0-05mm-insize-across-fromdistance-of-2m/
Safety related Sensors
Switches
REF:
http://www.directindustry.c
om/prod/fortressinterlocks/safety-switcheselectromechanical-29543229593.html
Light Curtains.
REF:
http://www.directindustry.c
om/prod/schunk/load-cellstorque-function-6-axis12463-903013.html
55
Accuracy and Repeatibility
Accuracy and Repeatibility
Accuracy and Repeatibility
Accuracy and Repeatibility
Accuracy and Repeatibility
Accuracy and Repeatibility
Accuracy and Repeatibility
Good Accuracy
Good Repeatability
Good Accuracy
Bad Repeatability
(IF the robot has
moved to the desired
positions)
Bad Accuracy
Good Repeatability
What affects accuracy and repeatability
Effect of
parameter faults
Environmental
effect, temp.
Effect of
load
Numerical
errors
Repeatability
Accuracy
What affects accuracy
and repeatability
Dimensional tolerances
Effect of
Effect of
parameter
faults
parameter
faults
Environmental
effect, temp.
Effect of
load
Numerical
errors
Repeatability
Accuracy
Misalignment in joints
Dimensional tolerances
Effect of
Effect of
parameter
faults
parameter
faults
Environmental
effect, temp.
Effect of
load
Numerical
errors
Repeatability
Accuracy
Misalignment in joints
Dimensional tolerances
Effect of
Effect of
parameter
faults
parameter
faults
faults
Environmental
effect, temp.
Effect of
load
Numerical
errors
Calibrating errors
Repeatability
Accuracy
Misalignment in joints
Dimensional tolerances
Effect of
Effect of
parameter
faults
parameter
faults
Environmental
effect, temp.
Errors in the drive train
- dimensional tolerances
- backlash
Numerical
errors
Effect of
load
Calibrating errors
Repeatability
Accuracy
Effect of
parameter faults
Environmental
effect, temp.
Effect of
load
Effect of load
Numerical
errors
Bending, twisting and elongation
Repetability
Accuracy
Path Accuracy and Repeatability
2
3
Path Accuracy and
Repeatability
Positions defined
170 mm
1
4
135 mm
1
Start position & final
position
2.
Via position
3.
Via position
4.
Via position
Sequence 1 -> 2 -> 3 -> 4 -> 1
2
3
Path Accuracy and
Repeatability
Positions defined
1
170 mm
2.
3.
4.
Start position
( Fine, 40 mm/s )
Via position
( Fine, 40 mm/s )
Via position
( Fine, 40 mm/s )
Via position
( Fine, 40 mm/s)
Sequence 1 -> 2 -> 3 -> 4 -> 1
1
4
135 mm
2
3
Path Accuracy and
Repeatability
Positions defined
1
170 mm
2.
3.
4.
Start position
( Rough, 400 mm/s )
Via position
( Rough, 400 mm/s )
Via position
( Rough, 400 mm/s )
Via position
( Rough, 400 mm/s)
Sequence 1 -> 2 -> 3 -> 4 -> 1
1
4
135 mm
2
3
Path Accuracy and
Repeatability
Positions defined
1
170 mm
2.
3.
4.
Start position
( Fine, 800 mm/s )
Via position
( Fine, 800 mm/s )
Via position
( Fine, 800 mm/s )
Via position
( Fine, 800 mm/s)
Sequence 1 -> 2 -> 3 -> 4 -> 1
1
4
135 mm
2
3
Path Accuracy and
Repeatability
Positions defined
1
170 mm
2.
3.
4.
Start position
( Rough, 1600 mm/s )
Via position
( Rough, 1600 mm/s )
Via position
( Rough, 1600 mm/s )
Via position
( Rough, 1600 mm/s)
Sequence 1 -> 2 -> 3 -> 4 -> 1
1
4
135 mm
ISO 9283 defines the Robot performance
measurements
ETC.
The ISO standard specifies measurement
conditions and procedures
Load, speed and accuracy are related to each other
One example of a measurement system with
integrated software for robot measurements is
Leica Smart 310, a laser tracking- and
interferometry-based system.
http://www.youtube.com/watch?v=d3fCkS5xFlg
Good performance characteristics lead to good
results
http://www.youtube.com/watch?v=SOESSCXGhFo
76
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