Kinetic and Dimensional Optimization for Dual-Mode Tendon-Driven Grippers
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Solution Overview
Problem
Existing robotic end-effectors face challenges in achieving versatile and stable grasping of objects in unstructured environments while maintaining low complexity and cost, particularly in transitioning between fingertip and enveloping grasps without active control.
Innovation Solution
A low-complexity, underactuated gripper design with passive tendon mechanisms and optimized joint torques, allowing for passive adaptation to object shape, enabling both fingertip and enveloping grasps through a single motor actuation, and optimized dimensions for a wide range of household objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single motor actuates multiple joints via tendon mechanisms, then device complexity is reduced, but precise control of joint torques and grasp stability deteriorates
Solution Approach 1:
The gripper employs dynamic optimization of tendon routing paths and joint torque ratios to adapt to different object shapes and sizes. The system transitions from static fixed-ratio actuation to dynamic adaptive control, where the tendon routing is optimized to provide appropriate torque distribution across multiple joints during grasping operations, enabling reliable performance across diverse objects despite using a single actuator.
2Device complexity
If the gripper uses fixed joint torque ratios, then device complexity is reduced, but adaptability to different object shapes and sizes deteriorates
Solution Approach 1:
The patent optimizes the torque ratio parameters of the tendon-driven joints to achieve appropriate force distribution for different object shapes and sizes. By carefully designing the tendon routing paths and joint moment arms, the system achieves variable torque ratios without active control, allowing the gripper to adapt to diverse objects while maintaining low complexity through passive parameter optimization.
3Reliability
If the gripper is designed for enveloping grasps, then stability against external disturbances is improved, but the range of graspable objects (especially small objects) deteriorates
Solution Approach 1:
The gripper divides the grasping function into two distinct grasp modes: fingertip grasps for small objects and enveloping grasps for larger objects. Each mode is optimized for specific object size ranges and application scenarios. This segmentation allows the system to achieve both high precision for small objects and robust disturbance resistance for larger objects, with the appropriate mode being activated based on object dimensions and task requirements.
4Ease of operation
If the gripper uses passive adaptation mechanisms, then ease of operation is improved, but control precision and active adjustment capability deteriorates
Solution Approach 1:
The gripper employs passive adaptation mechanisms where the tendon-driven joints automatically adjust their configuration based on object contact and resistance forces. The system uses the object's own properties (shape, size, surface) to guide the grasping process without active sensing or control, allowing the gripper to self-adjust to different objects while maintaining operational simplicity through purely passive mechanical adaptation.
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 gripper achieves stable grasping and versatile manipulation of various objects by passively adapting to object shapes, ensuring robustness against external disturbances and maximizing the range of graspable objects with optimized tendon routing and joint torques.
Implementation Method 1
passive tendon mechanisms and optimized joint torques, allowing for passive adaptation to object shape
Implementation Method 2
Extension is entirely passive, achieved with joint springs
Data Source
AI summary
A tendon-driven robotic gripper is disclosed for performing fingertip and enveloping grasps. One embodiment comprises two fingers, each with two links, and is actuated using a single active tendon. During unobstructed closing, the distal links remain parallel, creating exact fingertip grasps. Conversely, if the proximal links are stopped by contact with an object, the distal links start flexing, creating a stable enveloping grasp. The route of the active tendon and the parameters of the springs providing passive extension forces are optimized in order to achieve this behavior. An additional passive tendon is disclosed that may be used as a constraint preventing the gripper from entering undesirable parts of the joint workspace. A method for optimizing the dimensions of the links in order to achieve enveloping grasps of a large range of objects is disclosed and applied to a set of common household objects.