Unit 3: Workspace Analysis and Trajectory
Planning
Q. Workspace Analysis
Definition: The workspace of a robot refers to the total volume or area within which
the end-effector of the robot can operate or reach.
Importance: Determines the robot's suitability for specific tasks.
Factors Influencing Workspace:
o Robot configuration (e.g., SCARA, articulated).
o Length of links and range of joint motion.
o Joint limits and singularities.
Analysis Techniques:
o Geometric modelling to identify reachable points.
o Simulation software for visualizing reachable spaces.
Q. Work Envelope of Robots
Four-Axis SCARA Robot:
o Shape: Typically, a cylindrical workspace.
o Description: SCARA (Selective Compliance Assembly Robot Arm) is
optimized for horizontal tasks like pick-and-place and assembly.
o Features:
High-speed operation in 2D planar regions.
Limited Z-axis reach.
Applications: PCB assembly, material handling.
o Application:
Assembly: Quickly positioning components in electronics (e.g., PCB
assembly).
Material Handling: Palletizing or transferring objects.
Pick-and-Place: Sorting lightweight parts efficiently.
Five-Axis Articulated Robot:
o Shape: Complex 3D shape, often spherical or irregular due to jointed arm
flexibility.
o Features:
Extended reach and high dexterity.
Can handle both horizontal and vertical tasks.
Applications: Welding, painting, advanced assembly.
o Application:
Welding: Precise welding in automotive industries.
Painting: Evenly spraying paint on complex surfaces.
Advanced Assembly: Assembling large or irregularly shaped
components.
Q. Pick and Place Operations
Pick-and-place operations involve a robot selecting an object from one location and placing it
at another with precision and efficiency. The process starts with object detection, using
sensors or vision systems to locate and identify the item. The robot’s end-effector, such as a
gripper or suction cup, securely grasps the object based on its size and material. It then moves
the object along a planned path, avoiding obstacles, and ensuring stability. Finally, the robot
accurately places the object in the target location, often with sensor feedback for fine
adjustments. This operation is key in industries like manufacturing and packaging for
repetitive, high-precision tasks.
Q. Joint Space Technique:
Continuous Path Motion
Continuous path motion involves the robot moving smoothly along a defined trajectory,
passing through multiple intermediate points without stopping. Unlike point-to-point motion,
where the robot stops briefly at designated points, continuous motion ensures a fluid
transition between all points. This is essential for tasks requiring precision, such as arc
welding, painting, or writing, where a consistent path and velocity are critical for maintaining
quality. The robot's controller calculates the necessary joint movements to follow the path,
ensuring smooth acceleration and deceleration. This method minimizes abrupt changes in
joint angles, reducing wear on components and enhancing motion precision.
Interpolated Motion
Interpolated motion is a trajectory-planning method where the robot calculates and follows a
precise path between start and end points. Common types of interpolation include:
Linear Interpolation: The robot’s end-effector moves in a straight line between two
points. This is used in tasks like drilling, cutting, or precision assembly, where the
shortest, most direct path is needed.
Circular Interpolation: The robot follows an arc or circular path, which is useful in
machining or robotic painting.
The interpolation process ensures the robot achieves the desired path by coordinating the
movement of multiple joints. This allows for smooth and predictable motion, making it ideal
for tasks requiring exact positioning and orientation.
Straight Line Motion
Straight-line motion ensures the robot’s end-effector travels in a direct line in Cartesian
space, regardless of the complexity of joint movements required to achieve this. It is critical
for tasks like inserting components, moving tools along a surface, or welding along a straight
seam.
To achieve straight-line motion, the robot’s control system calculates joint movements such
that the end-effector maintains the linear trajectory. This often requires synchronized
movement across all joints, as small deviations can cause the end-effector to stray from the
desired path. Straight-line motion is particularly useful in operations requiring high precision
and minimal deviation from the intended path.
Q. Cartesian Space Technique in Trajectory Planning
The Cartesian space technique focuses on controlling a robot's end-effector directly in
Cartesian coordinates (X, Y, Z), rather than joint movements. Paths are planned as straight
lines, curves, or other shapes, with the robot's controller solving inverse kinematics to
calculate joint movements for smooth execution.
Advantages
Intuitive Planning: Easy to define paths like straight lines or curves.
High Precision: Ensures accurate end-effector positioning and orientation.
Simplified Tasks: Ideal for tasks like welding, painting, or assembly.
Challenges
Computationally Intensive: Solving inverse kinematics requires significant
processing.
Workspace Constraints: Some positions may be unreachable due to robot limits.
Applications
Welding, painting, cutting, drilling, and precise assembly.
Tasks requiring consistent end-effector paths.
Cartesian vs. Joint Space
Cartesian space offers more precision and intuitive planning for end-effector paths but
requires more computation compared to joint space techniques.
