Robotics and Automation
Robotics and Automation
This domain tests robot anatomy, degrees of freedom, workspace and payload limits, coordinate frames, teach-pendant work and robot safety within automated cells. Expect questions comparing accuracy with repeatability and identifying the axes needed for a task.
Core rules
- A robot has a base, arm, wrist and end effector. Six degrees of freedom (three positioning, three orienting) allow an arbitrary pose in space; fewer means the orientation is constrained.
- Joint types: revolute (rotary), prismatic (linear). A SCARA gives fast planar pick-and-place; a Cartesian gantry gives large rectangular workspace; an articulated six-axis arm gives flexibility.
- Payload is rated at the tool centre point and must include gripper mass; payload falls as reach increases and with dynamic motion.
- Accuracy is how close the robot reaches the commanded point; repeatability is how closely it returns to the same taught point. Industrial arms are far more repeatable than accurate, so absolute hole positions are handled by teaching, vision or calibration.
- Safety: perimeter fencing, interlocked gates, light curtains, area scanners, hard-wired emergency stop and restricted speed in manual mode. Safety distance depends on stopping time and approach speed.
Worked example
A cell must insert a pin into a hole with 0.1 mm clearance. The available robot is rated repeatability ±0.05 mm but accuracy ±0.3 mm. Reasoning: the robot cannot be trusted to reach an absolute coordinate within 0.1 mm, but it can return repeatedly to a taught position within 0.05 mm. Solution: teach the position with a compliant float or visual alignment, or use a vision sensor with calibration; do not programme from CAD coordinates alone.
Traps
Using payload rating without adding gripper mass; confusing accuracy with repeatability; assuming a five-axis robot can orient freely; ignoring reach limits at full extension.