Compliant Gripper with Dual-Sensitivity Force Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing compliant grippers face limitations in achieving a large gripping range while maintaining a compact design, bidirectional actuation, and accurate force sensing for micro-manipulation and micro-assembly tasks, with most grippers having limited unidirectional gripping ranges and requiring separate force sensors for grasping and interaction forces.
Innovation Solution
A dual-sensitivity, dual-range force sensor is integrated into a compliant gripper design using compound parallelogram flexures and radial flexures, allowing for bidirectional actuation and simultaneous detection of grasping and interaction forces using a two-stage force sensing mechanism, enabling a larger gripping range and compact structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a compliant gripper is designed with a larger gripping range, then the applicability to objects of various sizes is improved, but the overall dimensions of the gripper become larger and less compact
Solution Approach 1:
The gripper is divided into two independent actuators (first actuator for closing motion, second actuator for opening motion) that can be controlled separately. This segmentation allows each actuator to be optimized for its specific function while working together to achieve bidirectional actuation and large gripping range without excessive overall dimensions
Solution Approach 2:
The gripper employs compliant mechanisms with variable stiffness characteristics that allow the structure to adapt dynamically during operation. The compliant fingers can deform elastically to accommodate objects of various sizes, enabling a large gripping range while maintaining a compact overall structure through dynamic adaptation rather than static size increase
2Adaptability or versatility
If bidirectional actuation is implemented to double the gripping range, then the operational capability is improved, but the device complexity and hardware costs increase due to requiring two actuators
Solution Approach 1:
The actuation system is segmented into two specialized actuators: a first actuator dedicated to closing motion and a second actuator dedicated to opening motion. This functional segmentation allows each actuator to be simpler and more reliable, while the overall system achieves bidirectional capability. The segmentation principle resolves the contradiction by making the complexity manageable through clear functional division
Solution Approach 2:
The compliant mechanism structure serves multiple functions: it acts as both the mechanical linkage for motion transmission and the spring element for restoring force generation. This multi-functionality reduces the need for additional components, offsetting the complexity introduced by having two actuators and achieving bidirectional actuation with manageable device complexity
3Measurement precision
If separate force sensors are used for grasping force and interaction force detection, then the sensing accuracy is improved, but the device complexity and hardware costs increase
Solution Approach 1:
A single force sensor is strategically positioned to simultaneously measure both grasping forces (when fingers close on an object) and interaction forces (when the gripper contacts the environment). This merging of sensing functions into one sensor reduces device complexity and hardware costs while maintaining measurement precision through careful sensor placement and signal processing
Solution Approach 2:
The force sensor is designed with multi-functionality to detect different types of forces depending on the operational state of the gripper. By universalizing the sensor's function to handle both grasping and interaction force detection, the system avoids the complexity of multiple specialized sensors while preserving measurement accuracy through appropriate sensor selection and signal interpretation
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 a gripping range of over 4 mm with high sensitivity in a smaller range and lower sensitivity in a larger range, facilitating precise grasping and interaction force detection, enhancing its applicability in micro-assembly tasks.
Implementation Method 1
The compliant gripper with integrated strain-gauge position and force sensors utilizes the piezoresistive effect to detect both position and force through resistance changes in strain gauges
Data Source
AI summary
A compliant gripper with integrated position and force sensors dedicated to automated micro-assembly tasks. The gripper possesses a larger gripping range with a bidirectional drive, and is capable of detecting grasping force and environmental interaction forces in horizontal and vertical axes. The gripper has a compliant rotary flexure bearing. The gripper further has a compliant mechanism with two-stage stiffness designed to provide force sensing with dual sensitivities in two measuring ranges to accommodate the grasping of objects with different sizes. The dual-sensitivity, dual-range force sensor provides finer and coarser force sensing in a small and large ranges, respectively. Analytical models are derived to predict the grasping range, force sensing sensitivities, and force measuring ranges. These models are verified by conducting finite-element analysis simulations.