Page 72 - Toucpad robotics C11

Sub-Micron Resolution: For high-precision applications like semiconductor manufacturing, robots often need to
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operate at sub-micron levels. This means they must be able to move in increments of less than one micrometre
(one-millionth of a metre). Such robots are used for tasks like placing microchips or inspecting tiny components.
Integrated Vision Systems: Integrated vision systems that allow for real-time adjustments based on visual
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feedback further enhance a robot’s effective resolution. The robot can ‘see’ a slight positioning error and correct
it on the fly, allowing it to perform tasks with a level of precision that exceeds the mechanical resolution of its
components alone.
Real-time Example: A robot sorting fruit on a conveyor belt uses a high-resolution camera. The camera can
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detect a tiny blemish on an apple. The robot’s arm, while having a certain mechanical resolution, uses the
camera’s feedback to make minute adjustments in its grasp, ensuring it can precisely pick up and place the
apple without damaging it.

Accuracy
Accuracy is the ability of a robot to position its end-effector precisely at a desired location in three-dimensional space.
It measures how close the robot’s actual position is to the target position. A robot can have high resolution (it can make
very small movements) but low accuracy (it can’t get to the exact desired location). Accuracy is affected by factors like
mechanical imperfections, joint play, temperature, and gravitational forces.
Current Trends: Enhanced Calibration Techniques: To achieve better absolute accuracy, modern robotics relies on
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advanced calibration techniques. Calibration is a process where the robot is precisely measured to account for all of its
mechanical imperfections, such as link lengths, joint alignments, and gear backlash. This data is then used by the control
system to create a more accurate mathematical model of the robot, minimizing errors in each part of the robot arm.
Real-time Example: In a car factory, a robotic arm is used to drill holes for screws on a car’s chassis. The robot is
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initially calibrated using a laser tracker, which measures the exact position of the robot’s end-effector throughout
its workspace. This calibration data is then fed into the robot’s control software. Consequently, when the robot is
commanded to move to a specific drilling location, it can do so with much greater accuracy, ensuring the hole is
drilled in the correct spot.
Dynamic Error Compensation: In real-world applications, factors like temperature changes (which cause materials
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to expand or contract) or wear and tear on joints can degrade accuracy over time. Modern control systems use
dynamic error compensation to adjust for these factors. Sensors can monitor temperature, for example, and the
control system can apply corrections in real time to maintain a high level of accuracy.
Real-time Example: In a metal fabrication plant, a robotic arm is used for welding. The heat from the welding
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torch can cause the robot’s arm to expand slightly, leading to a loss of accuracy. The robot’s control system,
equipped with temperature sensors, can compensate for this expansion in real-time, ensuring the weld remains
in the correct position.
Feedback Mechanisms: High-end robots use sophisticated feedback mechanisms to maintain accuracy. Techniques
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such as laser-based tracking systems or external vision systems can measure the robot’s actual position and provide
real-time correction signals back to the control system. This ensures that the robot is constantly adjusting its position
to match the desired location.
Real-time Example: A surgical robot performing a delicate operation uses a laser-based tracking system to
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continuously monitor the position of its surgical instruments. This system provides real-time feedback to the
robot’s control unit, which makes minute adjustments to the instruments’ position to ensure they remain on the
intended trajectory, enhancing the surgeon’s precision.

Repeatability
Repeatability is a robot’s ability to return to a specific position under identical conditions repeatedly. It is a measure of
the consistency of the robot’s motion. Think of it as a robot’s ability to place a pen in the exact same spot on a piece of
paper over and over again, even if that spot is not exactly where you wanted it to be (that would be an accuracy issue).

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Touchpad Robotics - XI