Page 57 - Toucpad robotics C11

Characteristics:
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They provide a constant reference for all other frames in the system.
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They are essential for defining the robot’s workspace and the location of objects within that space.
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All other frames’ poses are typically defined in relation to this fixed frame.
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Example: In a robotic arm, the base frame is a fixed frame. It is usually attached to the ground or a sturdy workbench
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and serves as the zero-point for all of the robot’s movements. When a robot is told to move its hand to a specific
coordinate, those coordinates are almost always in reference to this fixed base frame.
Practical Use: When a part is placed at a known location on an assembly line, its position is defined in the factory’s
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fixed frame. The robot uses this fixed frame to calculate its movements.
Moving Frames (Dynamic Reference Frames)
Description: A moving frame is a coordinate system that is attached to a moving object or part of the robot. As the
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object moves, its frame moves with it.

Common Moving Frames
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Link Frames: Each link (or segment) of a robotic arm has its own frame attached to it. When the joint moves, the
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frame attached to the link also moves.
End-Effector Frame: This is the most important moving frame for many tasks. It is attached to the robot’s tool or
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gripper. Its position and orientation in space are constantly changing as the robot arm moves.
Sensor Frame: Each camera or LiDAR sensor has its own coordinate frame attached to it. The measurements
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taken by the sensor (for example, the distance to an object) are expressed in this sensor’s local frame. To be
useful for navigation or mapping, these measurements must be transformed into the world frame (or the robot’s
global reference frame), where all data from different sensors and movements are aligned.
Crucial Role: Moving frames allow the robot to understand the complex geometry of its own body. A robot arm’s
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‘brain’ doesn’t just know the angles of its joints; it knows the location of the end-effector frame relative to the fixed
base frame by calculating the chain of relationships between all the moving link frames.
Characteristics:
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They are used to define the pose of individual components of the robot.
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The pose of a moving frame is typically defined relative to the frame of the component immediately preceding it
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(e.g., the frame of the forearm is defined relative to the frame of the upper arm).
Using moving frames simplifies the mathematical analysis of complex, multi-jointed movements.
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Example: Each link (segment) of a robotic arm has its own moving frame. As the first joint rotates, the frame attached
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to the second link moves along with it. Similarly, the End-effector (the gripper or tool) has its own moving frame,
which defines the precise location and angle of the tool’s tip.

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Mechanical System