Link Actuator Origin Positioning via Preload and Shaft
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Solution Overview
Problem
Existing link actuators face challenges in achieving a compact size with a wide operating range and high positioning accuracy due to increased dimensions and reduced rigidity, as well as backlash issues that affect positioning precision, especially in medical and industrial applications.
Innovation Solution
A method for initially setting the position of an origin in a link actuator with a configuration of proximal and distal link hubs connected by three or more link mechanisms, involving a preload application to eliminate backlash and store the operation amount for accurate posture control, using an origin positioning shaft and an absolute type encoder for precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the link length is increased to expand the operating range, then the travelling plate can cover a wider area, but the dimensions of the mechanism increase and the apparatus becomes bulky
Solution Approach 1:
The link mechanism is divided into multiple links (first link, second link, third link, fourth link) connected in series, allowing the mechanism to achieve extended operating range through angular articulation rather than increasing the overall length of individual components. This segmentation enables compact packaging while maintaining wide coverage area.
2Area of moving object
If the link length is increased to expand the operating range, then the travelling plate can cover a wider area, but the rigidity of the mechanism is lowered
Solution Approach 1:
By dividing the mechanism into multiple shorter links connected by rotational joints, each link can be designed with sufficient rigidity while the overall mechanism achieves extended range through angular coordination. The multiple links work together to maintain structural stiffness despite the extended operating envelope.
3Area of moving object
If the link length is increased to expand the operating range, then the travelling plate can cover a wider area, but the weight capacity of the travelling plate is limited
Solution Approach 1:
The multi-link configuration distributes the mechanical load across multiple connection points and structural elements, allowing the mechanism to support heavier loads at the travelling plate without requiring proportionally larger individual components. The segmented structure provides multiple load paths that enhance overall weight capacity.
4Volume of moving object
If three or more trinodal chain link mechanisms are used to achieve compact size and wide operating range, then the link actuator can be compact, but backlash in meshing portions causes positioning deviation
Solution Approach 1:
A preload mechanism is implemented to apply preliminary force to the meshing gear portions, eliminating backlash before positioning operations begin. This preliminary action ensures that the gears remain in constant contact without gaps, preventing positioning deviation caused by backlash during operation.
Solution Approach 2:
The preload mechanism applies a counteracting force that opposes the tendency of gears to separate under load, preventing the harmful effect of backlash. By applying this preliminary anti-action, the system maintains precise positioning without requiring larger or more complex gear mechanisms.
5Volume of moving object
If three or more trinodal chain link mechanisms are used to achieve compact size and wide operating range, then the link actuator can be compact, but positioning accuracy is lowered due to backlash increase over time
Solution Approach 1:
The preload mechanism is designed to compensate for backlash that develops over time through wear and usage. By continuously applying preliminary force to maintain gear contact, the system preserves positioning accuracy throughout the operational life of the actuator without requiring larger components.
Solution Approach 2:
Position detection means are provided to monitor the actual position of the travelling plate and provide feedback to the control system. This feedback enables real-time correction of positioning errors caused by backlash, maintaining manufacturing precision despite the compact multi-link mechanism design.
Data Source
AI summary
A link actuator includes a proximal end side link hub, a distal end side link hub, and link mechanisms which connect the distal end side link hub to the proximal end side link hub. Each of the link mechanisms includes a proximal side end link member, a distal side end link member, and an intermediate link member. Each of the proximal end side link hub and the distal end side link hub is provided with a through-hole which allows an origin positioning shaft to be inserted therethrough. The distal end posture of the link actuator is set to a specified posture by inserting the origin positioning shaft through the through-holes. An amount of operation of actuators in a state where preload is applied to the link actuator is set as a position of an origin of the actuator.