Robotic Arm Pulley Tensioning With Adjustable Split Pulleys
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Solution Overview
Problem
Robotic arm pulley arrangements face issues with cable loosening and breakage due to high driving forces, leading to performance degradation, and require a compact design that can withstand significant forces while maintaining tension.
Innovation Solution
A pulley arrangement with an adjustable pulley portion that can be locked in a selected rotational position relative to a base pulley, using a movable element and fasteners to secure the driving member, and incorporating tensioning mechanisms to maintain optimal tension levels, including split pulleys and adjustable pulleys with sliding blocks for bilateral tensioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a pulley arrangement is made compact to fit within the robotic arm, then the volume is reduced, but the ability to withstand high driving forces is compromised
Solution Approach 1:
The pulley is divided into a base pulley portion and an adjustable pulley portion that can be positioned independently. This segmentation allows the driving member to wrap around both portions, creating multiple load paths that distribute and reinforce the force transmission, enabling the compact design to withstand high driving forces effectively
Solution Approach 2:
The adjustable pulley portion can be positioned at different radial distances from the axis of rotation, adding a dimensional adjustment capability. This allows optimization of the wrap angle and force distribution without increasing the overall volume, as the adjustment occurs within the existing spatial envelope of the pulley arrangement
2Device complexity
If the driving member is wrapped around a fixed pulley, then the structure is simple, but cable loosening and breakage occur due to high driving forces
Solution Approach 1:
The pulley arrangement transitions from a fixed structure to a dynamic one where the adjustable pulley portion can be repositioned. This dynamic capability allows the system to adapt to varying driving forces and maintain optimal tension distribution, preventing cable loosening and breakage while managing the increased structural complexity through controlled adjustability
Solution Approach 2:
The radial position of the adjustable pulley portion can be changed to modify the wrap angle and tension distribution. By adjusting this parameter, the system optimizes the mechanical advantage and force distribution along the driving member, enhancing reliability under high driving forces without requiring a completely complex structure
Data Source
AI summary
In one variation, a pulley arrangement includes a base pulley portion rotatable within a driving plane, an adjustable pulley portion coupled to the base pulley portion wherein the adjustable pulley portion is rotatable relative to the base pulley portion within the driving plane, and a driving member including an end coupled to the adjustable pulley portion wherein at least a portion of the driving member is wrapped at least partially around the adjustable pulley portion. In another variation, a pulley arrangement includes a base pulley portion rotatable around an axis, an adjustable pulley portion coupled to the base pulley portion and movable in a first direction parallel to the axis, and a sliding block engaged with the adjustable pulley portion, wherein the sliding block moves in a second direction different from the first direction, in response to compression of the adjustable pulley portion against the base pulley portion.