Underactuated Soft Gripper Torque Distribution
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Solution Overview
Problem
Existing grasping technologies face challenges in adapting to diverse applications due to design constraints that are not well-aligned, limiting their adoption across different uses, such as robotic grippers, actuated prosthetic hands, and grip augmenting gloves, which often require wearable, lightweight designs that balance force distribution and conformability.
Innovation Solution
A grasping device with at least three actuated fingers and a differential mechanism that distributes torque from a motor to each finger, allowing for balanced force application and independent conformation to object shapes, using wound artificial tendons and gearsets to achieve even torque distribution and adaptive gripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single motor is used to actuate multiple fingers, then device complexity is reduced and weight is minimized, but it becomes difficult to distribute torque evenly and maintain force balance across all fingers
Solution Approach 1:
A differential mechanism is introduced as an intermediary component between the single motor and the multiple fingers. The differential receives rotational input from the motor and distributes torque to each finger through planetary gears, enabling even torque distribution without requiring multiple motors or complex control systems.
Solution Approach 2:
The differential mechanism changes the torque parameter distribution by using planetary gear ratios to automatically allocate torque evenly across multiple output shafts. This mechanical parameter transformation allows a single motor's rotational output to be converted into balanced torques for multiple fingers, solving the control difficulty.
2Strength
If fingers are made rigid to maintain structural strength, then grasping force is improved, but the ability to conform to various object shapes is reduced
Solution Approach 1:
Each finger is divided into multiple rigid segments (phalanges) connected by joints. This segmentation allows each segment to maintain structural strength while the articulated configuration enables the finger to bend and conform to different object shapes, combining rigidity with adaptability.
Solution Approach 2:
The finger structure transitions from a static rigid form to a dynamic articulated mechanism. The joints between segments allow the finger to dynamically adjust its shape and curvature during grasping operations, enabling adaptation to various object geometries while maintaining strength through the rigid segments.
3Ease of operation
If multiple motors are used to independently control each finger, then force balance and independent finger control are improved, but device weight and complexity increase
Solution Approach 1:
Multiple motor functions are merged into a single motor through the differential mechanism. The differential combines the torque output from one motor and distributes it to multiple fingers, achieving the functional equivalent of multiple motors while using only one physical motor, thereby reducing weight and complexity.
Solution Approach 2:
The single motor is given multi-functionality through the differential mechanism, allowing it to simultaneously control multiple fingers. The differential enables the motor to perform the work of multiple independent actuators by distributing torque across multiple output shafts, making the system more efficient and lighter.
4Adaptability or versatility
If the grasping device is designed for wearable applications, then adaptability to human hands is improved, but grasping force and structural strength are reduced
Solution Approach 1:
The patent replaces heavy traditional mechanical actuation systems with a more efficient differential-based torque distribution system. This substitution allows for better force utilization and transmission to the fingers, compensating for the size and weight constraints of wearable applications while maintaining or enhancing grasping force.
Solution Approach 2:
The differential mechanism changes the torque parameter distribution to optimize force delivery. By automatically distributing torque evenly across all fingers regardless of their position or load, the system maximizes grasping force efficiency within the constraints of wearable design, ensuring adequate strength despite reduced size.
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 solution enables a robust, adaptive grip that can conform to various object shapes while maintaining even force distribution across fingers, enhancing grip stability and versatility across different applications, from prosthetics to industrial tasks.
Implementation Method 1
a differential that is configured to distribute torque from a motor amongst the at least three actuated fingers
Implementation Method 2
at least one wound artificial tendon for each of the at least three fingers, wherein the wound artificial tendons couple the at least three fingers to a motor
Data Source
AI summary
A gear arrangement for actuating the fingers of a grasping device is disclosed. The gear arrangement distributes torque and/or rotational motion from a drive interface, such as an input gear or pulley, to three or more output shafts that are axially aligned. The gear arrangements can distribute torque and/or rotational motion to two output shafts that are axially aligned and co-extensive. These gear arrangements can utilise nested differentials, where the output from an outer differential is used as input to one or more inner differentials. The output from the differential is coupled to the fingers of a grasping device by a network of artificial tendons.