Grasp Assist Device Using Tendon Drive System
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Solution Overview
Problem
Repetitive manual operations can degrade a human operator's grip strength and productivity due to cumulative stresses, even with optimal ergonomic workspace configurations, as grip strength varies among individuals and over time due to fatigue.
Innovation Solution
A lightweight, servo motor-driven device worn on the hand and forearm that augments finger and thumb flexion by applying controlled tensile force through a tendon drive system, using force-based contact sensors to calculate and apply an optimal augmenting force based on the operator's grasp.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a human operator performs repetitive manual operations requiring grasping, then the task is completed, but the operator's grip strength degrades over time due to cumulative stresses and fatigue
Solution Approach 1:
The patent introduces a tendon drive system as an intermediary mechanical assistant between the operator and the grasping task. The system includes a motorized actuator connected to the operator's finger tendons through a tendon, allowing the actuator to apply augmenting force to the operator's grasp without requiring the operator to directly generate all the grasping force themselves
Solution Approach 2:
The patent replaces part of the operator's biological muscular system with a motorized tendon drive system. The actuator mechanically substitutes for the operator's weakened or fatigued grip muscles, transferring mechanical force through the tendon to augment finger flexion and grasp strength
2Ease of operation
If ergonomic workspace configuration is optimized, then some ergonomic stressors are ameliorated, but repetitive grasping tasks still pose stresses that cannot be lessened
Solution Approach 1:
The tendon drive system acts as a mechanical intermediary that shares the grasping load between the operator and the actuator. The force sharing mechanism allows the operator to perform ergonomic tasks with reduced muscular stress while the actuator provides supplemental force through the tendon connection
3Force
If grip strength is augmented using a motorized device, then grasping force is enhanced, but the device complexity increases
Solution Approach 1:
The patent employs flexible tendons and a compliant glove structure to create a lightweight, adaptable interface between the actuator and the operator's hand. The flexible tendon allows natural finger movement while transmitting augmenting force, and the thin film glove structure provides sensing capability without adding significant complexity or bulk
4Adaptability or versatility
If force-based contact sensors are used to control augmenting force, then the augmenting force becomes adaptive to the operator's needs, but the measurement precision requirements increase
Solution Approach 1:
The patent implements a feedback control system where force-based contact sensors measure the operator's grasping force, and the microcontroller adjusts the augmenting force from the actuator based on these measurements. The feedback loop allows the system to adapt the level of assistance dynamically, providing more help when the operator needs it and reducing help when the operator can handle the task independently
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
Enhances grasping force without straining the operator's hand, allowing for efficient execution of tasks with customizable and adaptive assistance, capable of providing 'super human' grip strength when needed.
Implementation Method 1
force-based contact sensors positioned at a distal end of each finger
Implementation Method 2
the tendon actuators are automatically activated in response to the measured grasp force. Once activated, the tendon actuators may exert an augmenting tensile force on the required tendons
Data Source
AI summary
A grasp assist device includes a glove portion having phalange rings, contact sensors for measuring a grasping force applied by an operator wearing the glove portion, and a tendon drive system (TDS). The device has flexible tendons connected to the phalange rings for moving the rings in response to feedback signals from the sensors. The TDS is connected to each of the tendons, and applies an augmenting tensile force thereto via a microcontroller adapted for determining the augmenting tensile force as a function of the grasping force. A method of augmenting a grasping force of an operator includes measuring the grasping force using the sensors, encoding the grasping force as the feedback signals, and calculating the augmenting tensile force as a function of the feedback signals using the microcontroller. The method includes energizing at least one actuator of a tendon drive system (TDS) to thereby apply the augmenting tensile force.