Bionic Dexterous Hand Orthogonal Axes Antagonistic Drive
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Solution Overview
Problem
Existing dexterous hands face challenges such as complex tendon and tendon sheath disassembly, non-orthogonal axes of degrees of freedom, lack of passive degrees of freedom, and rigid exoskeletons, which hinder maintenance, control complexity, adaptability to complex shapes, and compliant operation.
Innovation Solution
A 32-degree-of-freedom bionic endoskeletal dexterous hand design featuring a hand module with orthogonal axes of freedom, passive degrees of freedom, and a flexible structure, utilizing tendon transmission with antagonistic drive mechanisms and capstans, and a forearm module with actuator storage and tendon sheath guide base for efficient assembly and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If tendon transmission is used to transfer large forces to hand joints, then force transmission capability is improved, but the number of tendons and tendon sheaths increases making disassembly and maintenance difficult
Solution Approach 1:
The dexterous hand is divided into modular units (finger units with proximal and distal segments, palm unit, wrist unit) that can be independently assembled and disassembled. Each finger unit contains its own tendon transmission system, allowing localized maintenance without affecting the entire hand structure. The tendon sheaths are segmented to match these modular units, enabling easy removal and replacement.
Solution Approach 2:
The tendon transmission system is designed with tendons that can be extracted from the hand structure for maintenance or replacement. The tendon sheaths are configured to allow tendons to be pulled through and removed without dismantling the entire hand assembly, facilitating easy repair and replacement of worn components.
2Ease of operation
If each joint is driven antagonistically by a pair of actuators, then joint stiffness control and smooth operation are improved, but the number of motors increases making space arrangement difficult
Solution Approach 1:
Multiple actuators are merged into a compact drive unit located in the wrist or forearm. A single actuator can control multiple joints through a shared tendon system, reducing the total number of motors while maintaining antagonistic drive capability. The tendon routing is designed to allow one actuator to influence multiple finger joints simultaneously.
Solution Approach 2:
The actuators are designed with universal mounting interfaces and standardized tendon connection points, allowing the same actuator design to serve multiple joints. The tendon transmission system is configured so that a single actuator can provide antagonistic control for multiple degrees of freedom through strategic tendon routing and attachment points.
3Volume of moving object
If the hand size is kept small, then the dexterous hand fits human hand dimensions, but the transmission of large forces in a small space becomes challenging
Solution Approach 1:
The tendon transmission system is nested within the hollow phalange structures of the fingers. Tendons and tendon sheaths are routed through the internal cavities of the finger bones, maximizing space utilization. The actuator housing and tendon storage are nested within the wrist structure, maintaining a compact overall form while accommodating high-force transmission components.
Solution Approach 2:
Force transmission is achieved by utilizing the length dimension of the forearm rather than expanding hand volume. Tendons are routed from actuators in the forearm through the hand, allowing high-force actuators to be positioned away from the hand while still providing effective force transmission to all joints through optimized tendon routing paths.
4Reliability
If tendon sheaths are used to cover and protect tendons, then tendon protection and directional restraint are improved, but the complexity of assembly and disassembly increases
Solution Approach 1:
Tendon sheaths are divided into multiple segments corresponding to different finger units and wrist sections. Each segment can be independently assembled and disassembled, allowing maintenance personnel to access and replace tendons in specific regions without removing the entire sheath system. The segmented design maintains continuous protection while simplifying maintenance operations.
Solution Approach 2:
Tendon sheaths are pre-assembled with tendons in factory-configured modules before delivery. The sheath segments are pre-positioned with alignment features that guide correct assembly during installation. This preliminary preparation reduces on-site assembly complexity and ensures proper tendon routing and protection from the start.
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 design enhances operational flexibility, adaptability to complex shapes, and ease of maintenance, enabling smooth operation of complex objects while maintaining a compact size similar to a human hand.
Implementation Method 1
the tendon can slide axially within the tendon sheath to restrain the direction of the tendon
Implementation Method 2
a capstan is configured to convert a rotation of an output shaft of the actuator to a pulling force on the tendon
Data Source
AI summary
This application discloses a dexterous hand. The dexterous hand uses the anatomical structure of human hands for reference. The joints adopt dual-actuator antagonistic drive, which gives consideration to both compliant operation and robustness. The tendon joint and tendon sheath fixator are used for easy disassembly of hands and wrists. The metacarpophalangeal joints of each finger have the DOF of circumduction of, so that the fingers can automatically adapt to the complex surface. The axes of the multi-degrees of freedom joints are orthogonal, which is beneficial to control and motion planning calculation. The dexterous hand is ideal for handling objects of complex shape smoothly, facilitating production, disassembly and maintenance.