Rolling-Friction Kinematic Chain for Torque Transfer Along Any Path
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Solution Overview
Problem
Existing kinematic transmission systems face challenges in efficiently transmitting torque between rotating elements with non-parallel axes, as traditional solutions like pulleys require parallel axes or are stiff, while bowden cables are inefficient due to friction and limited range of rotation.
Innovation Solution
A kinematic chain comprising pulleys with adjustable rotation axes and connecting elements that allow a transmission element to follow a predetermined path through rolling friction, enabling adaptable and efficient torque transmission between pulleys with any relative orientation, using a cable or belt transmission element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional belts and pulleys are used for torque transmission, then the transmission path is fixed and requires parallel rotation axes, but the adaptability to non-parallel axes and changing orientations is lost
Solution Approach 1:
The transmission system is divided into multiple segments: a first pulley, a second pulley, and intermediate connecting elements. Each connecting element contains a passage with a rotating element that can independently orient itself. This segmentation allows the transmission element to follow a determined non-linear path while maintaining reliable torque transmission through rolling friction at each interface, resolving the contradiction between transmission reliability and adaptability to non-parallel axes.
Solution Approach 2:
The connecting elements are designed with rotational freedom about axes perpendicular to the transmission element's path. This dynamic capability allows the system to adapt to changing orientations and non-parallel rotation axes while maintaining continuous contact through rolling friction. The rotating elements within passages can dynamically adjust their orientation to accommodate the determined path, enabling both reliable torque transmission and adaptability to varying geometric configurations.
2Adaptability or versatility
If bowden cables are used to transmit rotational motion with adaptability to any path, then the adaptability is improved, but the friction between cable and sheath reduces transmission efficiency
Solution Approach 1:
The system replaces the sliding friction mechanism of bowden cables with a rolling friction mechanism. Instead of a cable sliding within a sheath, the transmission element rolls along the determined path defined by the passages of connecting elements. This substitution of sliding friction with rolling friction dramatically reduces energy loss while maintaining the adaptability to follow any determined path, resolving the contradiction between adaptability and energy efficiency.
Solution Approach 2:
The rotating elements within the passages of connecting elements serve as intermediaries between the transmission element and the pulleys. These intermediaries enable the transmission element to follow a determined non-linear path through rolling contact rather than sliding contact. The rotating elements mediate the motion transmission, allowing adaptability to any path while minimizing frictional energy loss through rolling rather than sliding contact.
3Loss of energy
If pulleys arranged in series are used for efficient torque transmission, then the transmission efficiency is improved, but the system becomes stiff and cannot adapt to changing orientations
Solution Approach 1:
The connecting elements are designed with rotational freedom about axes perpendicular to the transmission element's path. This dynamic capability allows the system to adapt to changing orientations while maintaining efficient torque transmission through rolling friction. Unlike stiff series pulley systems, these connecting elements can dynamically adjust their orientation to accommodate the determined path, resolving the contradiction between transmission efficiency and adaptability to changing orientations.
Solution Approach 2:
The transmission system is divided into multiple independent connecting elements, each with its own passage and rotating element. This segmentation provides flexibility at each joint while maintaining efficient rolling contact for torque transmission. Each segment can independently orient itself to follow the determined path, combining the efficiency of multiple pulleys with the flexibility to adapt to changing orientations and non-linear paths.
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 a modular, versatile, and lightweight kinematic chain that efficiently transmits rotational motion with high adaptability to various paths and orientations, suitable for applications like robotics and wearable exoskeletons, maintaining high efficiency and flexibility.
Implementation Method 1
The transmission element is adapted to be, in said transmission configuration, fixedly in contact with said or each rotating element by means of a rolling friction, in order to allow a modelling of the determined path according to a predetermined geometry.
Data Source
AI summary
A kinematic chain comprises a first pulley, arranged to rotate about a rotation axis x, and a second pulley arranged to rotate about a rotation axis y. The kinematic chain comprises then at least one connecting element comprising at least one passage having at least one rotating element, said or each connecting element also comprising at least one interface arranged to connect the connecting element to an adjacent connecting element or to a pulley, generating a rotational constraint about a rotation axis z. The kinematic chain also comprises a transmission element arranged to develop along a determined path for transmitting a rotational motion between the first pulley and the second pulley. The transmission element is adapted to be, in use, fixedly in contact with said or each rotating element by a constraint of rolling friction, in order to allow a modelling the determined path according to a predetermined geometry.