Elastic Cable Drive System for Robot Joint Weight Reduction
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Solution Overview
Problem
Cable-driven articulated joints in robots are difficult to control, result in increased weight, cost, and complexity, and lack the energy absorption and transfer capabilities of biological joints, leading to imbalance, stress, and high energy consumption.
Innovation Solution
A motorized drive system using relatively stretchable elastic cables connected to a pulley with a variable radius, which directs the elastic cables through guide rings to articulate the joint along a predetermined path, allowing one motor to flex the joint and absorb impacts by storing energy as potential for kinetic use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If joint-mounted motors are used to articulate the joint, then control is simplified, but the joint assembly becomes heavy and bulky
Solution Approach 1:
The motor is extracted from the joint assembly and relocated to the robot body. This removes the heavy motor component from the moving joint, significantly reducing joint assembly weight while maintaining the ability to control the joint through cable transmission.
Solution Approach 2:
Cables serve as intermediaries to transmit force from the body-mounted motor to the joint. This allows the motor to remain on the body while still effectively controlling the joint articulation, resolving the contradiction between motor location and control effectiveness.
2Weight of moving object
If non-stretchable cables are used to reduce joint weight, then the joint becomes lighter, but control difficulty increases and additional motors are required
Solution Approach 1:
The cable material property is changed from non-stretchable to elastic. This parameter change allows a single motor to control the joint through elastic cable deformation, eliminating the need for additional motors and simplifying the control system while maintaining lightweight joint design.
Solution Approach 2:
The elastic cable provides self-adjusting tension and energy storage capabilities. The cable's elasticity automatically manages force transmission and energy absorption during joint articulation, reducing control complexity and eliminating the need for additional motors.
3Manufacturing precision
If rigid motorized drive units are used, then joint articulation is precise, but energy consumption increases due to inability to absorb impacts
Solution Approach 1:
The elastic cable acts as a pre-configured energy absorption mechanism. During joint articulation, the elastic cable absorbs impact energy through deformation before it can cause imbalance or stress, preventing energy waste and reducing overall energy consumption while maintaining articulation precision.
Solution Approach 2:
The elastic cable converts harmful impact forces into beneficial elastic potential energy. This energy can be stored and later released to assist joint articulation, transforming what would be wasted energy into a useful resource that reduces overall energy consumption.
4Use of energy by moving object
If elastic cables are used to reduce weight and improve energy absorption, then energy consumption decreases, but control precision may be compromised
Solution Approach 1:
The system transitions from static rigid cable control to dynamic elastic cable control. The elastic cable's time-varying stiffness and energy storage capabilities allow it to adapt to different articulation phases, maintaining precision while improving energy efficiency through dynamic energy management.
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 system reduces the weight and cost of the motorized drive system, absorbs impacts to maintain smooth movement, and converts stored potential energy into kinetic energy for improved performance, reducing energy consumption and enhancing joint flexibility.
Implementation Method 1
the elastic cable is capable of absorbing and transferring kinetic energy for this purpose
Implementation Method 2
storing energy as potential for kinetic use
Implementation Method 3
The pulley has a variable radius adapted to balance the tension along the elastic cable
Data Source
AI summary
A motorized drive system and method for articulating an articulated joint having a motor and an elastic cable. The elastic cable is operatively connected to both the motor and the articulated joint such that the motor articulates the joint via the elastic cable. In addition, the elastic cable is adapted to be sufficiently elastic such that the motorized drive system is configured to use one motor for each degree of freedom through which the articulated joint moves.