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FUNDAMENTALS OF ROBOTICS��Module 5���- Dr. Adithya Hegde�Assistant Professor�Department of Robotics and AI, MITE, Moodabidre

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About the course – Module 5

Module 5 – Robot Applications (8 Hrs.)

  • Industrial Application, Material Handling: Material Transfer Applications
  • Machine Loading and Unloading Application, Palletizing Application
  • Processing Applications: Arc Welding, Robot for Arc Welding Application, Arc Welding Robot Requirements, Assembly
  • Applications: The Assembly Task, Peg-in-hole Assembly, Steps in Assembly
  • Compliance, Providing Compliance, Inspection Application: Sensor Based Inspection, Vision Based Inspection
  • Robot Safety, Non-Industrial Applications

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Industrial applications

  • Robot applications classified into four main categories:
    • Material handling operations
    • Processing applications (operations category)
    • Assembly operations
    • Inspection operations
  • Common material handling applications in hazardous environments:
    • Foundry operations
    • Die casting
    • Plastic molding
    • Forging operations
    • Handling dangerous/radioactive materials
  • End-effector is typically a suitable gripper
  • During workcycles, robots perform processes using tools as end-effectors
  • Automotive industry leads in robot usage for these applications

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Industrial applications

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Material Transfer Applications

  • Definition: Primary objective is moving parts from one location to another without complex constraints
  • Characteristics:
    • Simplest robot operation
    • Requires relatively simple robot with few degrees of freedom
    • Simple controller adequate
  • Common name: Pick-and-place or pick-n-place operations
  • Motion requirements: Point-to-point motion (path not important)

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Material Transfer Applications

  • Typical workcycle (A-B-C-D):
    • A: Pickup point (fixed, known location)
    • B: Safe distance point
    • C: Move to desired position
    • D: Delivery point (place part)
  • Essential requirements:
    • Part available at stationary pickup point in specific orientation
    • Previous part removed before next delivery

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Material Transfer Applications

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Machine Loading and Unloading Applications

  • Definition: Loading material/parts into machines and unloading finished parts
  • Three possible cases:
    • Machine loading only
    • Machine unloading only
    • Both loading and unloading
  • Key requirement: Timing coordination between robot and machine cycles
  • Communication methods:
    • Robot controller establishes communication with machine
    • Monitor machine operation with sensors and controllers

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Machine Loading and Unloading Applications

  • Typical setup: Robot-centered workcell containing:
    • Robot
    • Production machine(s)
    • Part delivery and removal systems
  • Applications: Die casting, plastic molding, machining, forging, heat-treating
  • Sequence example: Pick raw material → Load into fixture → Machine processes → Unload finished part → Place in pallet

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Machine Loading and Unloading Applications

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Machine Loading and Unloading Applications

  • Definition: Process of stacking/storing material, parts, or cartons on pallet in specified manner
  • Two processes:
    • Palletizing: Pick from fixed point, place on pallet (delivery point changes each cycle)
    • Depalletizing: Pick from pallet, place at fixed delivery point (pickup point changes)
  • Key difference from simple pick-n-place: Delivery point not fixed - changes with every part until pallet full

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Machine Loading and Unloading Applications

  • Next location computation based on:
    • Part count
    • Pallet size
    • Part size
    • Corner location of pallet
  • Complex variations:
    • Multi-layer pallets (3D stacking)
    • Inclined or vertical pallets
    • Bins or slots for specific parts
  • Robot programming: Easily programmed to compute delivery points and track part count

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Machine Loading and Unloading Applications

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Machine Loading and Unloading Applications

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Arc Welding

  • Definition: Most common process application for industrial robots requiring continuous long welding
  • Process: Arc initiated between electrode and metal pieces creates temperatures sufficient to melt parts and form molten pool
  • Human welder challenges:
    • Skill and judgment required for path movement
    • Quality depends on electrode speed
    • Consumable electrode requires movement toward parts

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Arc Welding

  • Hazards making it suitable for robots:
    • Ultraviolet radiation injurious to vision
    • High temperature
    • Molten metal and flying sparks
    • Toxic fumes
  • Process variations:
    • Consumable electrode: contributes filler metal, size reduces
    • Non-consumable electrode: separate wire/rod supplied continuously

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Arc Welding

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Robot for Arc Welding Application

  • Manipulator capabilities:
    • Move tool-point (electrode end) along 3D trajectory
    • Continuous path movement capability (point-to-point insufficient)
    • Feed mechanism for consumable electrode or filler metal wire
  • Degrees of freedom:
    • 5 DOF: Can weld parts in a plane
    • 6 DOF: Required for welding complex contours
  • Workcell controller coordination:
    • Robot motion
    • Electrode/wire feed
    • Spark gap control
    • Welding current control

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Robot for Arc Welding Application

  • Workspace requirements:
    • Large enough to accommodate part sizes
    • Two workstations option for continuous operation
  • Programming needs:
    • Mechanism to feed welding contour
    • Interpolation algorithms for paths between points
  • Enhanced capabilities: Sensors for path tracking and weld monitoring to overcome difficulties and compensate for process parameter variations

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The Assembly Task

  • Definition: Fitting two or more discrete parts together to form new product or subassembly
  • Assembly process:
    • Final stage of manufacturing
    • Manual labor intensive (40-50% of human labor)
    • Sequential assembly of components to subassemblies
  • Assembly operations involve:
    • Considerable handling, positioning, and orienting of parts
    • Applying controlled force to mate parts properly
    • Close interaction between parts being assembled

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The Assembly Task

  • Types of assembly:
    • Permanent: Welding, brazing, riveting, adhesives
    • Temporary: Screwdriver with screw, spanner with nut
  • Assembly methods:
    • Mating two parts directly
    • Placing parts together and fastening with third part
    • Joining them through various processes
  • Key difference from other applications: Assembly requires close interaction between parts, and assembled parts maintain relationship adding value to product

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The Peg in a hole assembly

  • Definition: Most common assembly task involving inserting one part (peg) into another part (hole)
  • Difficulty levels vary:
    • Round peg in round hole: Orientation about axis not required (5 DOF minimum)
    • Square peg in square hole: Additional orientation required (6 DOF needed)
  • Complex variations:
    • Multiple peg-in-hole: All pegs must align with corresponding holes simultaneously
    • Example: Electronic components (resistors, transistors, ICs) on printed circuit boards

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The Peg in a hole assembly

  • Human vs Robot challenge:
    • Extremely simple for humans
    • Very difficult for robot manipulators
    • Shows complexity of apparently simple tasks
  • Difficulties for robots:
    • Physical limitation of mechanical compliance
    • Lack of mating strategy for various initial positions
    • Uncertainties in physical world
  • Failure scenarios: If hole not in expected location or peg grasped incorrectly, robot usually cannot complete assembly without human help

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The Peg in a hole assembly

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The Peg in a hole assembly

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Steps in assembly

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Steps in assembly

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Steps in assembly

  • Four-step process:
    • Step 1: Approach - Initial positioning toward hole
    • Step 2: Hole crossing - Moving across hole opening
    • Step 3: One-point contact - Initial contact with hole edge
    • Step 4: Two-point contact - Full engagement, peg may get stuck
  • Problem stage: Last stage where peg may get stuck due to wrong forces and moments

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Steps in assembly

  • Solutions to increase success rate:
    • Special hardware devices
    • Sophisticated sensors and controllers
    • Software exploiting mechanical compliance
    • Utilize compliance in otherwise rigid robot manipulator
  • Success factors: Proper force and moment application throughout all stages

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The Compliance

  • Definition: Allowed or initiated movement of peg for alignment with hole
  • Three types of misalignments requiring compliance:
    • Lateral misalignment: Parallel axes but laterally offset
    • Angular misalignment: Non-parallel axes
    • Axial misalignment: Along axis direction
  • Three corresponding compliance types:
    • Lateral compliance: Movement in lateral direction to correct parallel axis misalignment
    • Rotational compliance: Angular movement to correct non-parallel axes
    • Axial compliance: Movement along axis to ease assembly initiation

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The Compliance

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The Compliance

  • Applications beyond peg-in-hole:
    • Turning doorknobs
    • Playing musical instruments
    • Scraping paint from glass
    • Performing surgery
  • Purpose: Correct lateral and angular errors during assembly to prevent peg getting stuck and ensure successful assembly

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Providing Compliance

Two methods of providing compliance:

Active Compliance:

  • Based on exploiting sensory data for successful assembly
  • Uses active force/torque sensing at manipulator wrist
  • Measures interaction forces between peg and hole
  • Computes degree of misalignment from sensor information
  • Robot controller programmed with algorithms to minimize misalignments
  • Alternative sensing: optical sensors and vision systems
  • Multiple sensors increase assembly success rate

Passive Compliance:

  • Uses passive mechanical device: Remote Center Compliance (RCC) device
  • Attached between wrist-end and gripper
  • Provides all three compliance types: lateral, rotational, and axial
  • Typical RCC device components:
    • Four lateral compliance elements (springs)
    • Four rotational compliance elements (springs)
    • Eight elements together provide axial compliance

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Providing Compliance

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Providing Compliance

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Providing Compliance

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Sensor Based Inspection

  • Purpose: Determine variety of part quality characteristics traditionally performed by manual inspection
  • Advantages over manual inspection:
    • Can inspect 100% of parts (vs statistical sampling)
    • Faster than manual inspection
    • Reduces human error
  • Limitation: Can only inspect for limited range of part characteristics
  • Sensor applications in inspection:
    • Quality control sensors detect part characteristics
    • Automated inspection systems
    • Statistical sampling replacement
  • Integration with robotics: Robots often used to implement inspection applications as fourth major sensor category
  • Applications include:
    • Dimensional checking
    • Surface quality assessment
    • Feature verification
    • Defect detection

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Vision Based Inspection

  • Purpose: Determine variety of part quality characteristics traditionally performed by manual inspection
  • Advantages over manual inspection:
    • Can inspect 100% of parts (vs statistical sampling)
    • Faster than manual inspection
    • Reduces human error
  • Limitation: Can only inspect for limited range of part characteristics
  • Sensor applications in inspection:
    • Quality control sensors detect part characteristics
    • Automated inspection systems
    • Statistical sampling replacement
  • Integration with robotics: Robots often used to implement inspection applications as fourth major sensor category
  • Applications include:
    • Dimensional checking
    • Surface quality assessment
    • Feature verification
    • Defect detection

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Robot Safety

Critical importance: Safety for all is important when using robots

Five main safety hazards:

  1. Human error in operation: Casual observer may approach stationary robot and be injured when it resumes operation
  2. Mechanical failures: Robot components can fail causing unpredictable movements
  3. Unauthorized access: People entering robot work envelope without proper safety procedures
  4. Electrical hazards: High voltage and current used in robot systems
  5. Flying objects: Components can slip or fly out of grippers, striking persons outside assumed danger zone

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Robot Safety

  • Safety devices and procedures:
  • Physical safeguards (contact microswitches, restrained keys)
  • Access door monitoring systems
  • Emergency stop systems
  • Safety barriers and fencing
  • Proper training and procedures
  • Regular maintenance and inspection

Design principle: Safety procedures and devices allow authorized human entry into robot work envelope with minimum injury risk while monitoring all anticipated access points

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Non-Industrial Applications

  • Service Sector Applications:
  • Healthcare: Hospital duties, medical care assistance, patient monitoring
  • Agriculture and Farms: Limited use but growing - plowing, seeding, fruit picking, livestock breeding, animal shearing
  • Research and Exploration:
    • Space exploration
    • Under-sea exploration
    • Nuclear research
    • Geological exploration

Domestic Applications:

  • Household tasks: Dishwashing, vacuuming, bed making, furniture dusting, window washing

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Non-Industrial Applications

Security: Traffic control, fire fighting

Entertainment and Service: Restaurant service, mall management, office cleaning

Expanding Applications:

  • Recreation: Sports playing, musical instruments
  • Specialized tasks: Diamond polishing, tire repair, gasoline dispensing, painting
  • Communication: Talking, listening, dancing

Future Potential: Robots designed for various industries including pharmaceuticals, textiles, chemicals, mining, construction, and energy sectors, with growing applications in non-manufacturing domains

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End of Module 5

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