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PR 502 Robot Dynamics & Control 2/28/2007
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PR 502: Robot Dynamics and Control
Asanga RatnaweeraDepartment of Mechanical Engineering
Faculty of Engineering University of Peradeniya
Introduction
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Robot Structure
Joints:
Links
End Effector
WristShoulder
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End effectorsGripperSuction/VacuumGlueHooksRack and PinionScrew and Fastener Devices
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End Effectors: Mechanisms
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Robot Links and Joints
Sliding –Prismatic (P)Rotating –
Revolute (R)
Spherical joint
Universal joint
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Robot CoordinatesCartesian/rectangular/gantry (3P or PPP)
Three linear (prismatic) joints
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Robot CoordinatesCylindrical (R2P or RPP)
Two prismatic joints and a revolute joint
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Robot CoordinatesSpherical (2RP or RRP)
One prismatic joint and two revolute joint
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Robot CoordinatesArticulated/anthropomorphic (3R or more)
All revolute joints
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Two Famous Industrial ManipulatorsPUMA. (Programmable Universal Machine for Assembly). ‘78.SCARA. (Selective Compliant Articulated Robot Assembly). ‘79.
SCARAPUMA
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Robot Configuration:
Cartesian: PPPCylindrical: RPP Spherical: RRP
SCARA: RRPArticulated: RRR
Hand coordinate:
n: normal vector; s: sliding vector; a: approach vector, normal to the tool mounting plate
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Robot reference frameWorld reference frame
A universal coordinate frame as defined by x, y, z coordinatesUsed to define the motion path reference to other objects
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Robot Reference FrameJoint reference frame
Coordinate system defined at each jointUsed to specify movements of each joint
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Robot Reference FrameTool reference frame
Coordinate system defined at the end effectorUsed to defined the movement of the end effector
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Robot CharacteristicsPayload
The maximum weight a robot can carryReach
Maximum distance a robot can reach within its work envelop
PrecisionHow accurately a specified point can be reached
RepeatabilityHow accurately the same position can be reached it the motion is to be repeated many times
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Robot Selection MeasuresPayloadPrecisionResolutionAccuracyRepeatabilitySpeedWork Envelope and ConfigurationControl System
Degrees of FreedomMemory SizeSoftware CapabilityInstallation FactorsCostDrive SystemProgramming MethodInterfacing Capabilities
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Robot SpecificationsNumber of Axes
Major axes, (1-3) => Position the wristMinor axes, (4-6) => Orient the toolRedundant, (7-n) => reaching around obstacles, avoiding undesirable configuration
Degree of Freedom (DOF)WorkspacePayload (load capacity)Precision v.s. Repeatability
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Robot Applications in ManufacturingMaterial Handling/PalletizingMachine Loading/UnloadingArc/Spot WeldingWater jet/Laser cuttingSpray CoatingGluing/SealingAssemblyInspection/TestingInjection MoldingPolishingPackaging
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AdvantagesRobots are more accurateRobots can work without breaksRobots don’t get sick or take vacationsRobots can be used in dangerous conditionsRobots are very clean
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DisadvantagesCost increases
Initial equipmentMaintenance staffPreventative maintenanceUtilitiesService contracts
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