Compliant Underactuated Grasper with Flexure Joints
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Solution Overview
Problem
Existing robotic graspers require multiple actuators to achieve a full range of motion, which can be cumbersome and inefficient, especially in unstructured environments, and lack the ability to adapt to various object shapes and sizes effectively.
Innovation Solution
A compliant underactuated grasper design featuring a palm base and fingers with compliant flexure joints and pin joints, utilizing fewer actuators than degrees of freedom, along with a thumb for independent movement, and incorporating a return biasing spring to maintain open positions, allowing for adaptive grasping and manipulation of objects through a combination of tendon cables and torsion springs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple actuators are used to achieve full range of motion, then the grasper can manipulate objects effectively, but the device complexity and actuator quantity increase
Solution Approach 1:
The finger is divided into multiple segments (proximal phalanx, intermediate phalanx, distal phalanx) connected by compliant flexure joints. This segmentation allows each segment to move independently, creating multiple degrees of freedom without requiring proportional actuators for each joint. The tendon cable system controls these segmented movements with fewer actuators.
Solution Approach 2:
The grasper employs compliant flexure joints instead of rigid mechanical joints, allowing dynamic adaptation to object shapes. The compliance enables passive adaptation through elastic deformation, reducing the need for active control actuators while maintaining versatility in grasping different objects.
2Adaptability or versatility
If compliant flexure joints are used, then adaptability to object shapes improves, but manufacturing precision requirements increase
Solution Approach 1:
The flexure joints are designed with specific geometric parameters (curvature radii, thickness, length) that can be adjusted to achieve desired compliance characteristics. By optimizing these parameters, the joints provide sufficient adaptability while maintaining manufacturability through standard fabrication processes.
3Device complexity
If fewer actuators are used, then device complexity reduces, but the ability to achieve full range of motion is limited
Solution Approach 1:
The tendon cable system serves multiple functions: it actuates multiple finger segments, provides force transmission, and enables coordinated movement across different degrees of freedom. This multi-functionality allows full range of motion to be achieved with fewer actuators by having each actuator control multiple aspects of the grasping motion.
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
Enables efficient and versatile grasping and manipulation of objects in structured and unstructured environments with fewer actuators, providing stability and adaptability to diverse object shapes and sizes, while minimizing the required spring rates and actuator forces.
Implementation Method 1
a return biasing spring to drive the proximal phalanx in the second direction to a return position
Implementation Method 2
a compliant flexure joint connecting the distal phalanx to the proximal phalanx
Data Source
AI summary
A compliant underactuated grasper includes a palm base and two fingers. Each of the fingers comprises: a proximal phalanx; a distal phalanx; a compliant flexure joint connecting the distal phalanx to the proximal phalanx; and a pin joint connecting the proximal phalanx to the palm base, the pin joint constraining angular movement of the proximal phalanx relative to the palm base to rotation about a pin pivot axis. The grasper further includes at least one actuator to move the fingers. The grasper has fewer actuators than degrees of freedom.