Cable-Driven Manipulator with Compensation Device
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Solution Overview
Problem
Conventional cable-driven manipulators experience variations in tensile force and unintended malfunctions due to changes in cable length during forearm pivoting, leading to improper operation of end effectors.
Innovation Solution
A cable compensation device is installed between the upper arm and forearm, comprising pulleys with equal radii and interlocking rotating bodies, which maintain constant cable length by compensating for length variations through pulley movement, preventing interference and ensuring precise position control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a cable-driven manipulator uses a simple pulley system for power transmission, then the device complexity is reduced, but the cable length varies during forearm pivoting causing tensile force variations and end effector malfunctions
Solution Approach 1:
The patent introduces an intermediary cable compensation device between the upper arm and forearm pulley systems. This device acts as a mediator that absorbs cable length variations caused by forearm pivoting, preventing these variations from affecting the end effector operation. The compensation device includes additional pulleys and cables arranged to counterbalance length changes, thereby maintaining stable tensile force on the end effector driving cable.
Solution Approach 2:
The patent changes the geometric parameters of the pulley system by adding multiple pulleys with specific radius relationships and arranging them at predetermined intervals. The cable is wound in a specific pattern around these pulleys to create a compensation mechanism that maintains constant effective cable length despite forearm position changes. This parameter optimization resolves the contradiction between simple structure and reliable operation.
2Reliability
If the cable length is maintained constant using a compensation device, then the reliability of end effector operation is improved, but the device complexity increases due to additional pulleys and rotating bodies
Solution Approach 1:
The patent segments the cable-driven system into multiple independent cable paths, each serving specific functions. The cable is divided into multiple sections that are wound around different pulleys, with some sections responsible for power transmission and others for compensation. This segmentation allows the compensation function to be integrated into the existing structure without requiring a complete redesign, thus limiting the increase in complexity.
Solution Approach 2:
The patent merges the compensation function with the existing pulley system by integrating compensation pulleys and rotating bodies into the upper arm and forearm structures. The compensation device is combined with the power transmission mechanism rather than being added as a separate system, thereby achieving cable length stability while minimizing the increase in overall device complexity.
3Manufacturing precision
If multiple pulleys and rotating bodies are added to compensate cable length, then manufacturing precision requirements increase, but the ability to maintain constant cable length during pivoting is improved
Solution Approach 1:
The patent employs asymmetric arrangements of pulleys with different radius values positioned at specific locations. The first, second, and third pulleys have predetermined radius relationships that create an asymmetric compensation mechanism. This asymmetric design allows the system to compensate for cable length variations while being less sensitive to manufacturing tolerances, as the compensation effect is built into the geometric configuration rather than relying on precise symmetry.
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 effectively prevents tensile force variations and unintended malfunctions, allowing for precise control of end effectors during forearm pivoting, thereby enhancing the reliability and performance of cable-driven manipulators.
Implementation Method 1
a cable compensation device that is installed between the upper arm and the forearm and maintains constant a length of a cable wound on a pulley provided in a operating unit
Data Source
AI summary
The present invention discloses a cable-driven manipulator comprising an operating unit having a drive motor, and a pulley rotated by the drive motor. An upper arm is coupled, through a joint, to one side of the operating unit. A forearm coupled, through a joint, to the other side of the upper arm by the cable. A gripper of an end effector operably coupled to the forearm, a cable compensation device is installed between the upper arm and the forearm so as to maintain constant the length of the cable that transmits the power of the operating unit to the end effector during the pivoting of the forearm. It is thus possible to prevent the variation of tensile force due to the variation of the length of the cable for operating the end effector during the pivoting of the forearm or the unintended malfunction of the end effector.