Robotic Arm Acceleration Control for Semiconductor Wafer Transport
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Solution Overview
Problem
Automated transfer devices used in clean room environments, such as those for semiconductor wafers, experience disturbances like velocity ripple, leading to uneven acceleration, abrasions, and misalignment, which reduce manufacturing yield and increase costs.
Innovation Solution
A robotic apparatus with a first arm member pivoting about a first axis and a second arm member, equipped with a direct drive motor and a control unit that limits acceleration to a predetermined value, ensuring smooth and precise transport of workpieces by determining and adhering to an acceleration-limited motion profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If automated transfer devices are used to transport workpieces quickly and precisely, then manufacturing efficiency and speed are improved, but velocity ripple and acceleration disturbances occur causing abrasions and misalignment
Solution Approach 1:
The patent applies parameter changes by implementing acceleration limiting that dynamically adjusts the motion parameters of the robotic apparatus. The control system monitors and constrains acceleration values to remain below a predetermined threshold, transforming the motion profile from aggressive high-speed movement to a controlled acceleration-limited trajectory. This resolves the contradiction by maintaining productivity through automated transport while ensuring manufacturing precision by preventing excessive acceleration that causes velocity ripple and workpiece misalignment.
2Loss of time
If higher acceleration is applied to reduce transport time, then productivity is improved, but workpiece abrasion and contamination risk increase
Solution Approach 1:
The patent changes the acceleration parameter from high to limited values, establishing a maximum acceleration threshold that prevents workpiece damage. By controlling the acceleration parameter to remain below the predetermined limit, the system reduces transport time compared to manual handling while eliminating the harmful effects of excessive acceleration such as abrasions and contamination. This parameter control approach directly addresses the contradiction between speed and workpiece integrity.
3Device complexity
If traditional drive units with gears and belts are used, then device complexity is reduced, but velocity ripple and acceleration disturbances occur
Solution Approach 1:
The patent applies mechanics substitution by replacing traditional mechanical drive units with gears and belts with a direct-drive motor system. The robotic apparatus utilizes a direct-drive motor that eliminates intermediate mechanical transmission components, thereby removing the source of velocity ripple and acceleration disturbances. Although this increases device complexity slightly, it significantly improves reliability and transport stability by providing smooth, disturbance-free motion that prevents workpiece abrasion and misalignment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively minimizes disturbances, reduces the risk of abrasion and contamination, and enhances the reliability of workpiece transport, ensuring accurate tracking of motion profiles and maintaining the integrity of the workpieces during transfer.
Implementation Method 1
the first drive unit including a direct drive motor having a rotor coaxially disposed about the first axis
Implementation Method 2
The control unit is also configured to control the first drive unit such that the surface is not moved at an acceleration value that exceeds a predetermined acceleration limit during the transport of the workpiece
Data Source
AI summary
A robotic apparatus for transporting a workpiece includes a first arm that pivots about a first axis and a second arm that is pivotably connected to the first arm. The second arm has a surface upon which the workpiece can be received. A first drive unit of the robotic apparatus drives the first arm member to pivot about the first axis. The robotic apparatus includes a controller that controls the first drive unit to move the surface of the second arm member to transport the workpiece. The control unit also controls the first drive unit such that the surface is not moved at an acceleration value that exceeds a predetermined acceleration limit during the transport of the workpiece.