Hand Exoskeleton Glove With Series Elastic Grasp Assistance
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Solution Overview
Problem
Existing grasp assistance devices struggle to mimic the natural motion of the human hand, often resulting in inefficiency, discomfort, and limited grasp types due to friction, bulkiness, and reliance on sensors that add to the device's bulk and suffer from signal noise.
Innovation Solution
A hand exoskeleton design with independent motion of MCP and PIP joints, using series elastic actuators and a motion amplification controller to achieve all 33 grasps in the GRASP taxonomy without conforming to the shape of an object, allowing fingers and thumb to move independently or in sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If soft designs using cable systems or inflatable membranes are used, then the device can conform to the hand, but friction between cables and surrounding materials reduces efficiency and position control accuracy
Solution Approach 1:
The patent replaces traditional cable-based mechanical actuation with a robotic actuation system that uses direct drive motors and flexible tendons. This substitution eliminates the friction problems inherent in cable systems while maintaining the soft, conformable structure. The robotic actuators provide precise position control without the energy losses associated with cable friction.
2Adaptability or versatility
If rigid devices are used to achieve more grasp types, then the device can effectively engage movement of the joints, but the device becomes bulky and requires a large number of actuators and rigid linkages
Solution Approach 1:
The patent segments the hand into individual finger modules, each with its own actuator. This modular approach allows each finger to be independently controlled while keeping the overall device compact. The segmentation enables the system to achieve multiple grasp types without requiring a complex centralized actuation system with numerous rigid linkages.
Solution Approach 2:
The patent employs dynamic actuation where the stiffness and resistance of the device can be adjusted in real-time based on the grasping task. This dynamic behavior allows a single actuator to effectively control multiple degrees of freedom through variable impedance control, reducing the total number of actuators needed compared to static rigid systems.
3Device complexity
If rigid devices selectively actuate only a few joints and rely on translation of force throughout the length of the finger, then the device reduces bulkiness, but the mechanical coupling limits the number and types of grasps the exoskeleton is capable of achieving
Solution Approach 1:
The patent replaces mechanical force translation through rigid linkages with independent robotic actuators for each finger joint. This substitution eliminates the constraints of mechanical coupling while maintaining a compact form factor. Each actuator can independently control its associated joint, enabling a full range of grasp types without the bulkiness of complex mechanical transmission systems.
4Extent of automation
If sensors such as electromyography sensors are used to determine user intent, then the device can detect user signals, but the sensors add to the bulk of the device and suffer from signal noise
Solution Approach 1:
The patent implements a system where the user's intent is detected through the interaction forces and motion patterns during grasping tasks, rather than requiring separate sensing systems. The control system infers user intent from the mechanical interaction between the user's hand and the device, as well as from motion sensors that track finger position and velocity. This approach eliminates the need for bulky EMG sensors while maintaining accurate intent detection.
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 exoskeleton achieves a wide variety of grasps efficiently, providing comfortable and accurate assistance in daily tasks, enhancing user mobility and reducing fatigue in repetitive tasks.
Implementation Method 1
An actuator for a finger exoskeleton device includes a leadscrew configured for attachment to a motor assembly, a lead nut, one or more compression springs, and a housing. Rotation of the leadscrew is capable of causing linear motion of the motor assembly, with the lead nut held in place by one or more of the compression springs.
Data Source
AI summary
A device for providing assistance in dexterous grasping operations. The device is a nine degree of freedom exoskeleton glove capable of reproducing grasping tasks present in ordinary daily activity. The device relies on series elastic actuators and a motion amplification controller for movement and support of finger joints of a user and is easily modifiable to fit individual users with different hand sizes. The user driven control scheme requires no additional hardware (e.g., camera or EMG sensors) but relies on user movements (even weak movements). Intelligent assistance prevents uncomfortable motion beyond the natural range of motion of the fingers while reacting very quickly to the user's physical input.