Classification of Robots Based on Configuration

Robot configurations refer to the physical structure and movement mechanisms of the robot’s arm and body. These are primarily classified based on the type and combination of joints used to provide the robot with its range of motion. The major configurations include:

1. Polar Configuration
2. Cylindrical Configuration
3. Cartesian Coordinate Configuration
4. Spherical Configuration (also referred to as polar in some texts)
5. Jointed-arm Configuration
6. SCARA Configuration

a. Polar Configuration (Spherical Configuration)

• Structure: It combines rotary and linear motions. The arm can:
  • Rotate about a vertical axis (T-joint)
  • Pivot up/down along a horizontal axis (R-joint)
  • Extend/retract using a linear joint (L-joint)
• Working Range: The robot can reach in a spherical or polar coordinate system, making it suitable for 3D arc-like movements.
• Applications:
  • Welding
  • Handling at foundries
  • Material transfer tasks
• Example: A robotic arm picking items from a circular storage rack.

b. Cylindrical Configuration

• Structure: The arm moves in a cylindrical workspace. It consists of:
  • A rotary joint that rotates around the vertical base axis (T-joint)
  • A vertical linear motion to move the arm up/down (L-joint)
  • A radial linear motion to move in/out from the center (O-joint)
• Working Range: Creates a cylindrical-shaped workspace—ideal for operations along curved paths.
• Applications:
  • Assembly operations
  • Handling at machine tools
  • Spot welding
• Example: Robots that insert or extract parts from a press machine.

c. Cartesian Coordinate Configuration (Rectilinear or Gantry Robot)

• Structure: Uses three linear joints that move in:
  • X-direction
  • Y-direction
  • Z-direction
• Working Range: Operates in a rectangular/cuboidal workspace. Movements are straight and orthogonal, like a 3D printer.
• Advantages:
  • High precision and simplicity
  • Easy programming and maintenance
• Applications:
  • CNC machines
  • 3D printing
  • Pick and place robots
• Example: Robotic arms used in PCB assembly and inspection.

d. Spherical Configuration

Note: Often used interchangeably with Polar Configuration.

• Structure:
  • One rotary joint at the base (vertical rotation)
  • One rotary joint for elevation (up/down)
  • One linear joint for arm extension
• Motion: Similar to the polar robot but sometimes distinguished in textbooks based on specific joint arrangement.
• Applications: Same as polar robots, used in wide-range access applications like spray painting, die casting.

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