Multi-Axis Positioner With Magnetic Joints for Submicron Precision
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Solution Overview
Problem
Hexapods, commonly used for multi-axis positioning, are cost-prohibitive due to their synergistic motion requiring complex algorithms, high computing power, and expensive actuators, making them unsuitable for applications needing submicron precision without tolerance stack-up issues.
Innovation Solution
A parallel position manipulator using prismatic joint actuators with five Degrees of Freedom (DOF) and magnetic joints, allowing independent actuator movement without binding, and employing magnetic forces to maintain contact with the top plate, enabling precise positioning at a fraction of the cost of hexapods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hexapod multi-axis positioning stage is used, then positioning precision is improved, but device complexity and cost increase exponentially
Solution Approach 1:
The positioning stage is divided into independent actuators, each responsible for a specific degree of freedom. This segmentation allows each actuator to operate independently without requiring complex coordinated control of all actuators, thereby reducing overall system complexity while maintaining positioning precision.
Solution Approach 2:
The actuators are designed with universal five-degree-of-freedom joints that can accommodate multiple motion types (prismatic and rotational) within a single joint structure. This multi-functionality reduces the number of separate components needed and simplifies the overall system architecture.
2Measurement precision
If hexapod multi-axis positioning stage is used, then positioning precision is improved, but computing power requirements increase
Solution Approach 1:
By segmenting the control into independent actuator operations with predefined kinematic relationships, the computing burden is distributed and simplified. Each actuator's motion can be calculated independently based on simple geometric relationships rather than requiring complex real-time solution of coupled differential equations.
3Measurement precision
If spherical joints with tight tolerances are used to reduce slop, then positioning precision is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The joint design changes from traditional spherical joints to a hybrid prismatic-rotational joint with five degrees of freedom. This parameter change in the joint type allows for more relaxed manufacturing tolerances while maintaining positioning precision, as the kinematic constraints are distributed differently across the joint components.
Solution Approach 2:
The joints are designed to dynamically adapt their constraints based on the actuator's position and orientation. This dynamic constraint distribution allows for more forgiving manufacturing tolerances while maintaining precision through active control of the five-degree-of-freedom joint parameters.
4Measurement precision
If hexapod actuators are used to achieve precise motion, then positioning precision is improved, but actuator capability requirements and cost increase
Solution Approach 1:
The motion requirements are segmented and distributed across multiple actuators, each handling a portion of the total motion burden. This segmentation allows each actuator to be smaller and less capable individually, while the collective system achieves the required precision through coordinated operation of the five-degree-of-freedom joints.
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 submicron precision positioning at a significantly lower cost than hexapods, with scalable axes, reduced computing requirements, and no tolerance stack-up, allowing easy actuator movement without binding.
Implementation Method 1
employing magnetic forces to maintain contact with the top plate
Data Source
AI summary
A multi-axis positioning stage or positioner includes a top plate supported and manipulatable by a plurality of prismatic joint actuators. Each actuator includes an actuator joint having four or five Degrees of Freedom (DOF) with the top plate. When one or more of the actuators extends or contracts, the pivot points, or four or five DOF actuator joints, of the remaining actuators are allowed to shift to move the top plate. The actuators can be disposed between at least one base plate or base structure, and can be fixed thereto.