Two-link Robot Arm Trajectory Control for Substrate Transport
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Solution Overview
Problem
Conventional robot SCARA arms for substrate transport face challenges in avoiding contact between the end effector and the substrate during rotation, which can lead to interference and inefficient path planning, especially when picking up or placing substrates.
Innovation Solution
A method and apparatus that control the rotation of the robot arms to provide a path for the end effector that avoids contact with the substrate before or after pickup/placement, and ensures a partially straight linear path of the substrate's center relative to the robot's rotational axis, using a controller with a processor and memory to manage the arm movements and prevent interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the robot arm rotates the end effector to pick up or place the substrate, then the substrate transport function is achieved, but the end effector may contact the substrate causing interference
Solution Approach 1:
The system performs preliminary path planning that predicts potential contact between the end effector and substrate before motion execution. The controller calculates a contact-free trajectory in advance, adjusting the end effector's path to avoid interference zones where the substrate may be located during pickup or placement operations.
Solution Approach 2:
The patent extends the path planning from traditional two-dimensional XY plane to three-dimensional space by incorporating the Z-axis (vertical dimension). This allows the end effector to adjust its height and avoid contact with the substrate by moving in the vertical dimension while maintaining the required pickup and placement functionality.
2Object-affected harmful factors
If the end effector follows a complex path to avoid substrate contact, then contact interference is prevented, but the motion path becomes less efficient
Solution Approach 1:
The path planning system dynamically adjusts the end effector's trajectory based on real-time substrate position and arm configuration. Rather than using fixed complex avoidance paths, the controller continuously optimizes the motion path to maintain clearance from the substrate while minimizing deviation from the most efficient route, balancing contact avoidance with motion efficiency.
Solution Approach 2:
The system changes motion parameters such as end effector height (Z-coordinate), approach angle, and speed profiles to achieve contact-free operation. By dynamically adjusting these parameters during motion, the system can prevent substrate contact while maintaining efficient transport paths, rather than relying on overly conservative fixed trajectories.
3Adaptability or versatility
If the robot arm uses conventional three-axis rotation with wrist joint, then the robot arm can perform complex maneuvers, but the path planning complexity increases
Solution Approach 1:
The patent extracts and isolates the contact avoidance requirement from the overall path planning problem. By identifying and separating the substrate interference zones, the system can apply simplified avoidance logic specifically to critical regions while maintaining standard motion planning for the remainder of the workspace, reducing overall planning complexity while preserving maneuverability.
Solution Approach 2:
The system introduces an intermediary computational layer that translates complex three-axis rotation requirements into simplified two-dimensional path planning problems. By using the substrate center as a reference point and planning paths relative to this intermediary coordinate system, the controller reduces the complexity of managing three-axis rotations while maintaining full maneuverability.
Data Source
AI summary
Providing a first movement including rotating a first arm about a rotational axis of a robot drive; rotating a second arm on the first arm, where the first and second arms form a robot arm, where the first and second arms are the only arms of the robot arm, where the robot arm has an end effector rotationally fixed to the second arm, and where the end effector is configured to support a substrate thereon for transporting the substrate by the robot arm; and controlling the rotating to provide a path of the end effector such that the end effector does not contact the substrate during the rotating. Providing a second movement including rotating the arms to provide an at least partially straight linear path of a center of the substrate relative to the rotational axis of the drive robot when the substrate is on the end effector.