Hexapod Joint Force-Absorbing Structure for Shear Load
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Solution Overview
Problem
Current hexapod systems used in robots for nuclear reactor inspection and repair lack sufficient load capacity and robustness, especially in environments with shear forces and high temperatures, such as sodium-cooled reactors, due to inadequate force absorption and mechanical stress distribution.
Innovation Solution
A hexapod system with a force-absorbing structure integrated into the joint, where the center of rotation of the ball joint is located within the second support, reducing unnecessary forces on linear actuators and allowing them to focus on necessary movements, while the force-absorbing structure takes up shear forces, enhancing load capacity and reducing the system's bulk and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional hexapod system is used, then the robot can achieve mobility and access difficult-to-reach areas, but the load capacity is insufficient when shear forces are present
Solution Approach 1:
The joint is segmented into distinct functional components: a force-absorbing structure embedded in the first support, a ball joint connecting the force-absorbing structure to the second support, and linear actuators connecting the first and second supports. This segmentation allows each component to handle specific forces independently, with the force-absorbing structure taking up shear forces and the linear actuators focusing on generating motion forces perpendicular to the supports.
Solution Approach 2:
The force-absorbing structure acts as an intermediary element between the first support and the second support. It absorbs shear forces that would otherwise be transmitted to the linear actuators, protecting them from lateral loads and allowing the actuators to operate within their optimal force generation range.
2Ease of operation
If the center of rotation of the ball joint is positioned away from the second support, then the ball joint can provide rotational freedom, but unnecessary forces are exerted on the linear actuators
Solution Approach 1:
The center of rotation of the ball joint is positioned within the thickness of the second support, creating a balanced configuration where the lever arm between the ball joint and the second support is eliminated. This positioning ensures that forces are distributed evenly and that the linear actuators only need to generate the minimum necessary forces for movement, without additional moments caused by offset lever arms.
3Adaptability or versatility
If pivot joints mounted in series are used, then the robot can achieve articulation and mobility, but the solution is not sufficiently robust in sodium-cooled reactor environments
Solution Approach 1:
The joint employs a composite structural approach combining a force-absorbing structure embedded in the first support with a ball joint and linear actuators. This composite design creates a more robust system that can withstand the harsh conditions of sodium-cooled reactors, including high temperatures and chemically reactive environments, while maintaining full articulation capability.
4Device complexity
If hexapod joints are designed without force absorption capability, then the structure can be simpler and lighter, but the load capacity is reduced when shear forces are present
Solution Approach 1:
The force-absorbing structure serves multiple functions: it absorbs shear forces, provides structural support, and works in conjunction with the ball joint and linear actuators to enable full hexapod functionality. This multi-functional design allows the joint to handle both shear forces and perpendicular forces effectively without requiring separate systems for each function.
Data Source
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AI summary
The present invention concerns a hexapod system (1) comprising first (2) and second (3) supports and six linear actuators (10a, 10b, 10c, 10d, 10e, 10f), each linear actuator having two ends articulated respectively at the first (2) and second (3) supports by a ball and socket joint (41, 42, 43, 44), characterised in that it comprises: a force transfer structure (50) embedded on the first support (2) and coupled to the second support (3) by a ball and socket joint (51, 52) of which the centre of rotation (60) is located in the thickness of the second support (3). The invention also concerns an inspection and/or repair robot characterised in that it comprises a poly-articulated arm provided with a plurality of hexapod systems (1) according to the invention and in which the hexapod systems (1) are disposed in series.