aub191 l01 robot
TRANSCRIPT
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MANUFACTURING EQUIPMENT:
Lecture 6Industrial Robotics - Introduction
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Module structure
Safety, programming strategiesF7
Computer Aided Robotics, ProgrammingF8
ReglerteknikF12
KinemtikF11Motorer/GivareF10
Programming (Rapid)1
History, definitions, robot systemcomponents and anatomy,
F1,F6
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Today History
Definitions System components
Control systems
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Robot A mechanical device which performs automatedphysical tasks, either according to direct human
supervision, a pre-defined program, or a set ofgeneral guidelines using artificial intelligencetechniques.
- WikiPedia
En programmerbar flerfunktionell maskin som rkonstruerad fr att hantera material, detaljer,verktyg eller speciell apparatur och, genompreogrammerade rrelser, fritt utfra varieranderenden i en 3-dimensionell rymd utankontinuerlig vervakning.
- Lennart Hgeryd et. al
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History 1(3) 1921: R.U.R. (Rossum's
Universal Robots), a play byCzech writer Karel apekfeatures the first mention of theword robot, from the Czechword robota, meaning forcedlabor.
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History 2(3) 1956 - The world's first robot company
1961 Unimate, the first industrial robot goesonline in a GM automobile factory in NJ, USA.
1963 The first artificial robotic arm to be
controlled by a computer is designed 1974 Aseas first robot, IRB 6, is developed
Late 1970s: The robot industry starts its rapidgrowth, with a new robot or company enteringthe market every month.
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History 3(3)The development of robotics technology followed
the development of numerical control, and thetwo technologies are quite similar. They bothinvolve coordinated control of multiple axes(joints rob.), and they both use dedicated digitalcomputers as controllers. Whereas NCmachines are designed to perform specificprocesses, robots are designed for a wider
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 certainantropomorhic characteristics.
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Industrial roboticsThe study, design and use of robot systems
for manufacturing.
Robotics
RobotDesign
Robot Applications
KinematicsDynamicsControlsMachine DesignElectrical Systems
SelectionProgrammingOperation
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Commonly used configurations1. Articulated (industrial) robots (the original and most
common)2. SCARA robots (Selective Complience Assembly Robot Arm)3. Gantry robots
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Less common configurations Parallell 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.
The controllercontains an operatingsystem and softwarethat dictates how thesystem operates andcommunicates.
Controller
Teaching Pendant
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 pose 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, in
the base of the robot Hand coordinate system,
tool mounting platecoordinate system Tool Center 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 that
usually consists of a series of
segments jointed or slidingrelative to one another, for thepurpose of grasping and/ormoving objects, usually inseveral DOF
A good manipulator designcombines strength and rigiditywith minimal geometric volumeand great agility.
Influence from load and
acceleration forces tends tobend the manipulator linksaffecting 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)- sliding
movement, but the input andoutput links are perpendicularto each other.
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)- the
rotation joint is parallel to theinput link and perpendicularto the output link.
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Spherical arm Polar configuration
(Spherical) TRL+ Big workspace (two rotaryjoints and one prismatic).
- complex coordinates, difficult
too visualize and control. Applications: Used were few vertical
movements are required.
Pick and place applications. Pendel robot IRB 1000
(pendulum) assembly
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Cylindrical arm Cylindrical configuration,
TLO+ Easy to visualize andcontrol
+ 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)
- Requires a big volume to
operate, cant use all of it.- Difficult to adapt to new
applications
Applications: Pick-and-place, heavy loads. Electronic industry and in
measurement 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
control
- Difficult to visualize- Linear motion difficult to control- Structure not very rigid at full
reach.
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+ Rigid in vertical direction
- 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 establishthe orientation of the endeffector (tool, gripper etc.)
Can have 1- 3 axis Rotation in 3 axis
Roll ( T ) Pitch ( R )
Yaw ( R )(compare whit airplanemaneuvers)
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.
Different types of actuators, sensors andtransmissions are used. The design and choiceof components is vital for the control andaccuracy of the robot.
Terms Speed- the speed at the tool mounting plate, what's moreimportant is acceleration and retardation figures
Speed of response- The time it takes to move from one poseto another
Stability- refers to the amount of overshoot, from thecalculated 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
(air is compressed)- Difficulties with control of
speeds and take up of loads Applications
Small robots
Often pick and place withsimple control Use often by peripheral
equipment
Hydraulic+ Large lift capacity
+ High power to weight ratio
+ Good servo control
+ Fast response
- 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
+ Relatively inexpensive
- 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
A few specialized systems contain a clutch to
disengage the motor from the drive train in the caseof an emergency Some experimental 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.
To minimize inertia, improve dynamics
However, these systems typically have two majordisadvantages:
First, they introduce an additional element of inefficiency into
the system in the form of lost motion or windup in thetransmission; this effect is termed backlash Second, they introduce a certain amount of compliance into
the 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 4(4) How to minimize backlash? Careful design and manufacture, and certain types of
gear trains (such as harmonic drive, ball screwtransmission ) produce significantly less backlash. Systems have been developed that allow this
deflection to be predicted and corrected for within therobot control system, enhancing accuracy.
Harmonic Drive
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End effector A device or tool connected
to the end of a robot arm.The structure of an endeffector, and the nature ofthe programming and
hardware that drives it,depends on the intendedtask.
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 manystandard vacuumgrippers to buy
Vacuum control
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Magnetic grippers Magnetized often
used on flat partsmanufactured inmagnetic materials
Adhesive- use somekind of adhesivesubstance
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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 byitself, thereby increasing flexibility.