Planar Positioning Device with Segmented Linear Motors
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Solution Overview
Problem
Existing planar positioning devices face challenges with heat dissipation due to high current intensity in elongate coils, mechanical contact issues, and complex control structures, which affect precision and performance.
Innovation Solution
A planar positioning device with three degrees of freedom (X, Y, Rz) using linear motors with magnet and coil assemblies, where sliders with reluctance actuators follow the stage's movement, allowing contactless coupling and reducing mechanical disturbances, and employing linear encoders for precise measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If elongate electrical coils are used to provide sufficient stroke length, then the stroke length is improved, but heat generation increases due to large current intensity
Solution Approach 1:
The positioning device is divided into multiple independent linear motors, each with shorter coils that operate in parallel. This segmentation allows each coil to be shorter (reducing heat generation) while the combined effect of multiple motors provides the necessary stroke length through coordinated operation.
2Adaptability or versatility
If mechanical contact elements (pin or bolt in groove) are used to move coil pairs with the stage, then the coil pairs can follow stage movement, but mechanical contact creates disturbances in positioning precision
Solution Approach 1:
The mechanical contact-based following mechanism is replaced with an electromagnetic following mechanism. The linear motors use electromagnetic fields to couple the coil assemblies to the moveable stage, eliminating mechanical contact elements like pins or bolts that cause positioning disturbances.
3Manufacturing precision
If a separate drive with complex control structure is used to move coil pairs, then the coil pairs can be moved without mechanical contact, but the control and drive structure becomes complex
Solution Approach 1:
The driving function and following function are merged into a single linear motor system. The linear motors simultaneously provide the driving force for stage movement and the electromagnetic coupling to follow stage movement, eliminating the need for a separate complex control and drive structure.
4Reliability
If air bearings are used to support the stage without contact, then friction is reduced, but the device complexity increases due to additional components
Solution Approach 1:
Air bearings are integrated into the linear motor assemblies to provide contactless support for both the moveable stage and the coil assemblies. This pneumatic support system reduces friction and mechanical wear while maintaining relatively simple integration within the existing linear motor structure.
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 provides dynamic submicron motion accuracy, reduces heat generation, and enhances precision by minimizing mechanical contact, resulting in a cost-effective and high-precision positioning system suitable for semiconductor industry applications.
Implementation Method 1
each of said linear motors includes a magnet assembly arranged on the moveable stage and a coil assembly that is arranged on the base
Implementation Method 2
the moveable stage including air bearings and being supported without contact by the bearing surface of the base via said air bearings
Implementation Method 3
the sliders each have a reluctance actuator arranged on it, which reluctance actuator is configured and arranged to cooperate with (ferro)magnetic material on the moveable stage such that the slider follows the movement of the stage
Data Source
AI summary
A planar positioning device having three degrees of freedom (X, Y, Rz) includes a static base having a flat bearing surface and a moveable stage. The stage is moveable over the bearing surface in an XY-plane. The moveable stage includes air bearings and is supported without contact by the bearing surface via said air bearings. The device includes a linear motor acting in the X-direction and a linear motor acting in the Y-direction, and at least one additional linear motor acting in the X-direction or in the Y-direction. Each of the linear motors includes a magnet assembly arranged on the moveable stage and a coil assembly arranged on the base. The base includes a slider track extending in the X-direction and a slider track extending in the Y-direction. The sliders each have a reluctance actuator arranged on it to cooperate with (ferro)magnetic material on the moveable stage.