Fruit-Picking Gripper Force Control for Delicate Fruit Removal
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Solution Overview
Problem
Existing gripper mechanisms for picking delicate fruits like strawberries face challenges in reducing the risk of impermissible deformations and uncontrolled movements during fast automatic movements, dealing with variations in fruit sizes, minimizing damage, and avoiding contact with adjacent fruits, especially when fruits grow in bunches or strings.
Innovation Solution
A gripper mechanism with two or more movable fingers that controls the clamping force and mutual distance between fingers to prevent exceeding a maximum clamping force, using a drive system to maintain finger position during the removal stage, ensuring efficient and damage-free picking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gripper mechanism uses fast automatic movements to improve picking speed, then productivity increases, but the risk of impermissible deformations and uncontrolled movements increases
Solution Approach 1:
The gripper mechanism transitions from static clamping to dynamic control during removal. The fingers are initially clamped to secure the fruit, then released during fast movement to prevent uncontrolled movements, and re-clamped upon arrival at the destination. This dynamic adjustment of clamping state enables both high-speed operation and reliable fruit handling.
Solution Approach 2:
The clamping action is applied periodically rather than continuously. The gripper clamps the fruit during approach and initial removal phases, releases during the high-speed transport phase, and re-clamps at the destination. This periodic application of clamping force reduces cumulative deformation while maintaining control when needed.
2Adaptability or versatility
If the fingers are made larger to handle size variations of fruits, then adaptability increases, but the rigidity required to prevent deformations during fast movements decreases
Solution Approach 1:
The system dynamically adjusts the clamping force applied by the fingers based on the operational phase. During fast movements, clamping force is reduced or released to prevent deformation of large fruits. During approach and destination phases, full clamping force is applied to secure fruits of various sizes. This dynamic force adjustment allows large fingers to handle size variations without compromising rigidity when needed.
3Reliability
If the gripper mechanism applies sufficient clamping force to secure the fruit during fast movements, then the fruit remains clamped reliably, but impermissible deformations occur
Solution Approach 1:
The system applies counter-actions at different phases to prevent harmful effects. During approach, preliminary clamping prevents fruit detachment. During fast removal, clamping is released or reduced to prevent deformation from excessive force. Upon arrival, re-clamping secures the fruit for transport. These preliminary and corrective actions prevent both detachment and deformation.
Solution Approach 2:
The clamping force is applied periodically rather than continuously. Full clamping force is applied during approach and destination phases when the fruit is stationary or moving slowly. During the high-speed removal phase, clamping force is reduced or released entirely. This periodic application ensures reliable clamping when needed while preventing deformation during fast movements.
4Measurement precision
If the fingers maintain constant mutual distance during approach, then positioning precision improves, but the ability to adapt to size variations decreases
Solution Approach 1:
The mutual distance between fingers is dynamically adjusted based on the operational phase and detected fruit size. During approach, fingers are positioned with precise mutual distance for accurate targeting. Upon contact with the fruit, the distance is adjusted to accommodate the actual fruit size, allowing the gripper to adapt to size variations while maintaining positioning precision for the approach phase.
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 allows for fast and reliable picking of delicate fruits without causing damage, effectively handling size variations and minimizing contact with adjacent fruits, while maintaining a stable clamping force throughout the picking process.
Implementation Method 1
the at least two fingers are provided with an elongated, elastic deformable surface, which surface is configured for upon contact with the piece of fruit to be picked, assuming a concave shape that at least partially follows the contour of the piece of fruit to be picked
Implementation Method 2
during at least a part of the removal stage, the mutual position of the fingers is controlled by the drive such that their mutual distance does not increase
Data Source
AI summary
An improved method and apparatus for automatically picking a fruit is described. During the clamping stage, the movement of the fingers is controlled such that a specific maximum clamping force is not exceeded. In addition, during at least a part of the removal stage, the mutual position of the fingers is controlled by the drive such that their mutual distance does not increase.