Precision Tripod Motion Platform for Stable Six-DOF Position Recovery
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Solution Overview
Problem
Existing motion systems suffer from reduced positional accuracy due to accumulated error tolerances from multiple actuator devices, leading to instability and an inability to return to a set position after external disturbances.
Innovation Solution
A precision tripod motion system with three spaced-apart single-degree-of-freedom hinges and three-degrees-of-freedom joints, coupled with linear actuators that provide six degrees of freedom, allowing precise positioning and orientation of a workpiece with sub-micron accuracy and stability through decoupled rotational and linear movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple actuator devices are employed to achieve a large number of working positions, then the working positions increase, but the positional accuracy deteriorates due to additive tolerances
Solution Approach 1:
The system segments the motion control into six independent single-degree-of-freedom actuators, each controlling one specific movement axis (three linear and three rotational). This segmentation prevents the accumulation of tolerances that would occur with coupled multi-axial actuators, as each actuator's error does not propagate to other axes. The top plate's six independent movements are achieved through six separate SDOF actuators rather than fewer complex actuators, resolving the contradiction between versatility and precision.
2Adaptability or versatility
If multiple actuator devices are used to provide six degrees of freedom, then the motion capability improves, but the system stability deteriorates due to complicated interactions between components
Solution Approach 1:
The system divides the six degrees of freedom into six independent single-degree-of-freedom actuators, each responsible for one specific movement (three linear translations and three rotations). This segmentation eliminates complicated interactions between actuators that would occur in integrated multi-axial systems, as each actuator operates independently with its own control loop. The decoupled architecture ensures that instability in one actuator does not propagate to other axes, maintaining overall system stability while providing full six-DOF capability.
3Device complexity
If conventional motion systems are used, then the system simplicity is maintained, but the ability to return to set position after disturbance is lost
Solution Approach 1:
The system implements active feedback control through six independent control loops, one for each single-degree-of-freedom actuator. Each actuator continuously monitors its position and receives corrective commands to maintain the top plate at the desired position and orientation. This feedback mechanism enables the system to automatically return to its set position after external disturbances, such as gravity-induced tilting or accidental impacts, without requiring complex mechanical self-correcting mechanisms. The feedback control adds minimal complexity while dramatically improving reliability and position recovery capability.
Data Source
AI summary
A precision tripod motion system is provided. The tripod motion system in one example includes a bottom plate including three spaced-apart bottom single-degree-of-freedom hinges, a top plate including three spaced-apart top three-degrees-of-freedom (TDOF) joints, wherein the top plate is configured to receive a workpiece. Each linear actuator of three linear actuators is coupled to an associated SDOF hinge of the bottom plate and coupled to an associated TDOF joint of the top plate. Each linear actuator is configured to change length over a linear actuation span and configured to return the top plate to a predetermined set position after the top plate is displaced by an external force Each linear actuator includes a ball coupled to the associated three TDOF joint and a positioning actuator configured to move the ball to the predetermined set position prior to the return of the top plate to the predetermined set position.