Robotic Gripper With Magnetic Springs For Variable Stiffness
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Solution Overview
Problem
Existing robotic grippers face limitations in safely handling fragile or sharp objects due to sensor failures and limited mechanical and electrical bandwidth in active compliance control methods, necessitating the development of grippers with adjustable stiffness for enhanced safety and robustness in dynamic environments.
Innovation Solution
A two-finger gripper design utilizing magnetic springs in a repulsive configuration with antagonistic actuators allows for simultaneous adjustment of position and stiffness, enabling external force estimation and improved compliance through the use of experimentally fitted models, enhancing grasping robustness and safety during collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If active compliance control methods are used with sensor feedback, then position control accuracy is improved, but the system becomes susceptible to sensor failure and has limited mechanical and electrical bandwidth for shock tolerance
Solution Approach 1:
The patent introduces a compliant mechanism as an intermediary between the actuator and the grasped object. This compliant mechanism passively absorbs shocks and impacts through its elastic deformation, eliminating the need for high-speed sensor feedback and complex control algorithms while maintaining position control accuracy and improving reliability during unexpected collisions
2Device complexity
If constant stiffness actuators are used, then the system structure is simpler, but the trade-off between position accuracy and energy absorbing capacity cannot be optimized
Solution Approach 1:
The patent employs a compliant mechanism with variable stiffness characteristics that can adaptively change its stiffness level based on the operational requirements. The compliant mechanism transitions from a static structure to a dynamic system that can passively adjust its compliance level, enabling both high position accuracy and sufficient energy absorbing capacity without requiring complex active control systems
3Productivity
If higher stiffness is used in the actuator, then load capacity and position control speed are improved, but shock tolerance and safety during collisions are reduced
Solution Approach 1:
The patent incorporates a compliant mechanism that acts as a pre-designed cushioning element between the high-speed actuator and the grasped object. This compliant mechanism is specifically designed to absorb impact energy through elastic deformation, protecting fragile or sharp objects from high-impact forces during unexpected collisions while allowing the actuator to maintain high stiffness for fast position control
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 effectively demonstrates improved safety and robustness in handling fragile objects by providing adjustable stiffness and contact force measurement capabilities, protecting objects from high-impact forces and ensuring stable grasping during unexpected collisions.
Implementation Method 1
Magnetic springs in a repulsive configuration may be used as the non-linear preload springs
Data Source
AI summary
Safety is one of the most important factors in the robot interaction with unknown and dynamic environments. Recent studies have shown that the use of compliant components as a solution to the safety issue, especially in the physical human-robot interaction. To overcome performance degradation caused by including compliant elements into the systems, variable stiffness approaches have been introduced at the cost of an extra actuator. A variable stiffness gripper is presented. Embodiments of the disclosed gripper may have, for example, with two parallel fingers (jaws). Compliance of the system may be generated by using magnets as the nonlinear springs. Based on the presented design, the position and stiffness level of the fingers can be adjusted simultaneously by changing the air gap between the magnets.