Dual-Mode Twisted String Transmission for Wider Speed-Torque Range
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Solution Overview
Problem
Conventional actuators for robots, such as those with fixed gear ratios, struggle to achieve a wide speed-torque operating range and are often bulky, limiting the performance and application of robots in various fields.
Innovation Solution
A dual-mode twisted string actuator with a clutch and synchronizer mechanism that allows for selective transmission of rotational force, enabling two-speed auto transmission shifts and eliminating the need for a large gearbox, thereby enhancing the speed-force operating range and reducing system size and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a motor with a fixed gearbox is used, then the structure is simple, but the speed-torque operating range is limited and the volume and weight increase
Solution Approach 1:
The patent implements a dual-mode twisted string actuator where the transmission ratio can be dynamically changed between two modes (first mode and second mode) during operation. This dynamic adjustment allows the system to adapt its speed-torque characteristics based on operational requirements, resolving the contradiction between fixed structure and variable performance needs.
Solution Approach 2:
The actuator changes the transmission ratio parameter between two distinct modes by altering the winding configuration of the string on the pulley. This parameter change enables the system to achieve different speed-torque operating ranges without requiring multiple fixed gearboxes, thereby reducing overall system volume while maintaining versatility.
2Force
If a twisted string actuator is used, then the linear driving force is amplified with small torque, but the speed-force operating range remains narrow
Solution Approach 1:
The system dynamically switches between first and second modes to adjust the transmission ratio. In the first mode, the string winds on the pulley to provide high force amplification. In the second mode, the winding configuration changes to enable higher speed operation. This dynamic switching expands the speed-force operating range while maintaining the force amplification capability.
Solution Approach 2:
The actuator operation is segmented into two distinct modes with different transmission ratios. The first mode operates with a first transmission ratio optimized for force, while the second mode operates with a second transmission ratio optimized for speed. This segmentation allows the system to cover a broader operating range by selecting the appropriate mode for each operational requirement.
3Adaptability or versatility
If a dual-mode twisted string actuator is implemented, then the speed-force operating range is expanded, but the device complexity increases
Solution Approach 1:
The actuator uses a single integrated mechanism that performs multiple functions: it provides force amplification in the first mode and speed enhancement in the second mode. The same pulley and string assembly serve both modes, eliminating the need for separate mechanisms and reducing overall structural complexity despite the expanded functionality.
Solution Approach 2:
The patent merges the two transmission modes into a single actuator unit where the pulley and string system can operate in different configurations. By combining both modes in one integrated structure rather than using separate mechanisms, the system achieves expanded speed-force operating range while minimizing the increase in device complexity.
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 dual-mode twisted string actuator provides a slim and lightweight system with increased speed-force operating range, allowing for immediate transmission response and simultaneous transmission ratio change and brake effect without additional components, thus improving robot performance and versatility.
Implementation Method 1
a twisted string actuator which is a rotary-to-linear transmission that produces a remarkably high transmission ratio by twisting a single string or a pair of strings
Data Source
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AI summary
A dual mode twisted string actuator using a clutch is provided. The twisted string actuator according to an exemplary embodiment of the present disclosure includes: a first actuator; a first coupler which is rotated by the first actuator; a shaft which is coupled to and interlocked with the first coupler; a second coupler which is selectively interlocked with the first coupler and comprises a plurality of string receiving portions; and a string which has one end fixed to the first coupler and the other end fixed to a moving body through the string receiving portions of the second coupler. Accordingly, it is possible to reduce the size of the existing large and heavy transmission system and to miniaturize and lighten the size of the entire drive system.