au319g l01 robot
TRANSCRIPT
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MANUFACTURING EQUIPMENT:
Lecture 1-
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Today History Warning!! Mad scientist
Definitions
System components
Control systems
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Robot A mechanical device which performs automated physical
tasks, either according to direct human supervision, a pre-defined
program, or a set of general guidelines using artificial intelligencetechniques.
- WikiPedia
any automatically operated machine that replaceshuman effort, though it may not resemble human beings inappearance or perform functions in a humanlike manner. Byextension, robotics is the engineering discipline dealing with thedesign, construction, and operation of robots.
-Encyclopdia Britannica
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History 1(4) 1921: R.U.R. (Rossum's
Universal Robots), a play byCzech writer Karel apek
word robot, from the Czechword robota, meaning forcedlabour.
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History 2(4)
A picture from the film Metropolis, directed by Fritz Lang, 1927.
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History 3(4) 1956 - The world's first robot company, Unimate.
1961 Unimate, the first industrial robot goesonline in a GM automobile factory in NJ, USA.
controlled by a computer is designed
1974 Aseas first robot, IRB 6, is developed
Late 1970s: The robot industry starts its rapid
growth, with a new robot or company enteringthe market every month.
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History 4(4)The development of robotics technology followed
the development of numerical control, and thetwo technologies are quite similar. .
NC machines are designed to perform specific,
variety of tasks.-M.P.Groover
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What is an industrial robot?
ISO 8373:1994:
A manipulating industrial robot is an automaticallycontrolled, reprogrammable, multipurpose manipulatorprogrammable in three or more axes which may beeither fixed in place or mobile for use in industrialapplications
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Another definitionA general-purpose, programmable
machine possessing certainanthropomorphic (human-like)
.
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Commonly used configurations1. Articulated (industrial) robots (the original and most
common)
2. SCARA robots (Selective Compliance Assembly Robot Arm)
3. Gantry robots
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Less common configurations Parallel arm robots (E.g Tricept, Flexpicker,
f200ib) Linear units (articulated robot on a slider)
Tricept
Fanuc f-200ib
Flexpicker
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Robot system components Manipulator
Wrist
Actuators
Transmissions End Effector
Controller Sensor
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Robot system components An Industrial robot
contains several
electrical andmechanicalcomponents actingtogether as a system.
Teaching Pendant
The controllercontains an operatingsystem and softwarethat dictates how thesystem operates andcommunicates.
Controller Manipulator(robot arm and wrist)
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Degrees of freedom, DOF Each joint, moveable axis,
on the arm is considered a
degree of freedom. (DOF) the number of different ways inwhich a robot arm can move.
How many DOF areneeded in order too
achieve an arbitraryposition? How many DOF are
needed in order too
achieve an arbitraryorientation? Roll, Pitch, Yaw Pose: position and
orientation taken together
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Redundancy Robots with more than 6
DOF or with parallel jointsare redundant, whichmeans that they canachieve the same ose in
more than one way. Singularity- pose that can
be reached in differentways sometimes creates
problems.
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Coordinate systems All robot control andmovement is according todefined base coordinatesystem.
World coordinate system,referenced to shop floor
Base coordinate system, inthe base of the robot
Hand coordinate s stem
tool mounting platecoordinate system Tool Centre Point (TCP)
coordinate system,referenced to the toolworking point
Object coordinate system.Object relative basecoordinate system
z
x
y
Object coordinate system
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Robot anatomy 1(2) Manipulator- a mechanism for
the purpose of grasping and/or
moving objects
A good manipulator designcombines strength and rigidity
w m n ma geome r c
volume and great agility.
Influence from load andacceleration forces tends tobend the manipulator links
affecting negatively the accuracyof the robot.
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Robot anatomy 2(2)(Groover page 212-214)
Prismatic joints (sliding joints)*P:
a) Linear joint (L)- sliding
movement with the axis of thetwo links being parallel.
b) Orthogonal joint (O)- slidingmovement, but the input andoutput links are perpendicular
.
Rotary joints *R:c) Rotational joint ( R) the axis
of rotation is perpendicular toboth in and output links.
d) Twisting joint ( T)- the axis of
rotation is parallel to the axesof the two links.
e) Revolving joint ( V)- therotation joint is parallel to theinput link and perpendicularto the output link.
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Cylindrical arm Cylindrical configuration,
TLO+ Easy to visualize and
control
+ Very powerful when
hydraulic drives used+ Good access into cavities
and machine openings
- Restricted work space
Applications Material handling, pick-
and- place, assembly.
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Cartesian arm
Cartesian arm (gantry)
+ Easy to visualize
+ Easy kinematics andprogramming
+ Rigid structure (gantry)
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operate, cant use all of it.- Difficult to adapt to new
applications
Applications:
Pick-and-place, heavy loads.
Electronic industry and inmeasurement applications.
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Articulated (Jointed) arm Pros and cons:+ Maximum flexibility and covers
biggest work space relative tovolume of robot.
+ Revolute joints easy to seal
+ Reach over and under objects
- Complex kinematics, difficult to
- Difficult to visualize
- Linear motion difficult to control
- Structure not very rigid at fullreach.
Applications: Most common arm configuration
Painting, arc and spot-welding,material handling, etc.
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SCARA Selective Compliance
Assembly Robot Arm+ Compliant in the horizontal
direction
+ High acceleration
- Limited work space- Often only 3 DOF, with no
orientation
Applications Assembly
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Tricept Tricept, Parallel axis
robot, Swedish design byNeos robotics.
+ Powerful, stiff, sturdy,accurate.
- Small work space Applications:
Suitable for processing,heavy-duty cleaning and
pre-machining of aluminumcasting.
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Work envelope
The region of space a robot can reach.
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Robot wrist The wrist is used to establish
the orientation of the endeffector (tool, gripper etc.)
Can have 1- 3 axis Rotation in 3 axis
Roll ( T )
Pitch R
Yaw ( R )(compare whit airplane
maneuvers)
Difficult to design.
Small size
No singularities in work area
Rigid etc.
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Joint drive system Robot joints are actuated driven systems.
Terms Speed- the speed at the tool mounting plate, what's more
important is acceleration and retardation figures Speed of response- The time it takes to move from one pose
to another Stability- refers to the amount of overshoot, from the
calculated robot path, due to the weight and speed of the endeffector
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Actuators Pneumatic
+ Relatively inexpensive
+ High speed+ Common energy source in
industry- Limited control and accuracy
Hydraulic
+ Large lift capacity
+ High power to weight ratio
+ Good servo control
+ Fast responsea r s compresse
- Difficulties with control ofspeeds and take up of loads
Applications Small robots
Often pick and place withsimple control Use often by peripheral
equipment
- Maintenance problems withseals causing leakage
- Not suitable for high speedcycling.
- Expensive Applications:
Used on very big machines
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Actuators Electrical
(DC- servo and stepper motors)
+ Fast and accurate+ Possible to apply
sophisticated controltechniques to motion
+ e a ve y nexpens ve
- Brakes needed to lock them inposition
- Problems with overheating installed conditions
- Gear backlash limits precision
- High speed with low torque
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Transmissions 1(4) A robotic transmission can contain a variety of
different devices (gears, tendons and linkages) Virtually all robotic systems employ some sort of geartrain, and many contain at least a parking brake
from the drive train in the case of an emergency Some systems make use of direct drive motors that
do not contain a gear train at all
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Transmissions 2(4) Why transmissions?
To convert the high speed - low torque output of the prime
mover into a reduced speed - high torque input to the roboticjoint.
However, these systems typically have two majorsa van ages:
First, they introduce an additional element of inefficiency intothe system in the form of lost motion or windup in thetransmission; this effect is termed backlash
Second, they introduce a certain amount of compliance intothe system
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Transmissions 3(4) When backlash occurs, the gear teeth are able
to move without imparting motion upon the nextgear. This results in energy being wasted in
"winding up" the transmission.
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Transmissions 3 (4)
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Transmissions 4(4) How to minimize backlash?
Careful design and manufacturing
Harmonic Drive
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Transmissions 4(4) How to minimize backlash?
Harmonic Drive
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End effector A device or tool connected
to the end of a robot arm.
Grippers and tools
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Mechanical grippers 1(2)
Mechanical grippers are usually pneumatic or electricaldriven
Consist of two or more fingers
Special variants Double grippers, increase work cycle efficiency. Sensory feedback, can be used to detect whether part is on
place or not and to use the right amount of force
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Mechanical grippers 2(2) Multiple-fingered
gripper: possesses thegeneral anatomy of ahuman hand
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Vacuum grippers Used when objects are
soft or difficult to grasp There are many
standard vacuumgr ppers o uy
Vacuum control
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Magnetic grippers Magnetized often
used on flat partsmanufactured inmagnetic materials
Adhesive- use somekind of adhesive
substance
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Tools The robot performs
some processingoperation on the workpart
Arc welding tool Spot welding gun
Spray painting gun
Water jet cutting, etc.
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Tool changers
The robot can change between different tools by
itself, thereby increasing flexibility.