Robotic Cable Transmission Layout for Non-Parallel Pulley Axes
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Solution Overview
Problem
Existing mechanical transmissions for robotic devices, particularly those with non-parallel axes, face challenges such as cable slipping off pulleys, fluctuations in transmission ratio, and increased friction, which affect the stability and efficiency of the drive system.
Innovation Solution
The introduction of one or more intermediate pulleys in the mechanical transmission system, which are arranged with their axes of rotation inclined at a specific angle relative to the input and output pulleys, helps to reduce the angle between the axes of consecutive pulleys, allowing for deeper grooves and more effective retaining elements to prevent cable slipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the angle between the axes of consecutive pulleys is reduced to prevent cable slipping, then the reliability of the transmission is improved, but the overall size and complexity of the transmission system increases
Solution Approach 1:
The transmission system is divided into multiple independent pulleys (first pulley, second pulley, third pulley) with specific angular relationships. Each pulley is segmented with grooves at specific angles to guide the cable independently, allowing the system to maintain reliability while managing complexity through modular segmentation of the cable path.
Solution Approach 2:
The patent introduces a third dimension by arranging pulleys with axes at different angles in three-dimensional space. The first and second pulleys have axes at a first angle, while the second and third pulleys have axes at a second angle, creating a spatial arrangement that prevents cable slipping without requiring excessively small angles between all consecutive pulleys.
2Reliability
If deeper grooves and retaining elements are added to pulleys to prevent cable slipping, then the reliability is improved, but the manufacturing complexity and precision requirements increase
Solution Approach 1:
Each pulley is equipped with grooves and retaining elements positioned at specific local angles relative to its axis. The first pulley has a groove at a first angle, the second pulley has grooves at first and second angles, and the third pulley has a groove at a second angle. This localized angular positioning distributes the retention function across multiple pulleys rather than requiring excessive precision in a single pulley's groove geometry.
3Adaptability or versatility
If the transmission system is designed to accommodate complex articulations with non-parallel axes, then the adaptability of the robotic device is improved, but the friction and energy loss in the transmission increase
Solution Approach 1:
The transmission system is designed to dynamically accommodate the movement of robotic articulations with non-parallel axes. The multiple pulleys are arranged to follow the cable path through varying angular relationships, allowing the transmission to adapt to changing articulation positions while maintaining relatively low friction through the distributed groove and retaining element design.
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
This configuration enhances the robustness of the transmission by maintaining a stable gap between pulleys, reducing the risk of cable slipping, and allowing for a more compact and lightweight design, while maintaining the same drive distances and deflection angle.
Implementation Method 1
these mechanical drives are also characterized by non-negligible friction that varies according to the curvature taken by the sheaths during the movement of the articulations
Implementation Method 2
The transmission comprises: an input pulley configured to rotate around a first axis of rotation; an output pulley configured to rotate around a second axis of rotation; and at least one intermediate pulley configured to rotate around a third axis of rotation
Data Source
AI summary
A transmission element intended to be diverted between an input and output direction, an input pulley rotating around a first axis of rotation orthogonal to the input direction and partly wrapped by the transmission element, an output pulley rotating around a second axis of rotation orthogonal to the output direction and partly wrapped by the transmission element, the second axis of rotation being non-parallel to the first axis of rotation. The first and second axis of rotation form between them a deflection angle having predefined width, an intermediate pulley positioned between the input and output pulley and configured to rotate around a third axis of rotation, and inclined with respect to one of the axes of rotation by an angle having smaller width than the width of the deflection angle, and partly wrapped by the transmission element. The planes of rotation of the pulleys are non-parallel.