Leaf-Spring Robot Joint With Rotation Feedback for Accurate Positioning
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Solution Overview
Problem
Existing robotic arms face challenges with high cost and limited absolute accuracy due to friction, play, and shifting behavior in ball bearings, which are exacerbated by the need for precise positioning in horticultural tasks like fruit and vegetable harvesting, sorting, and packaging.
Innovation Solution
A robot joint utilizing leaf springs with integrated measuring means to measure angular rotation between elements, allowing for low-cost production and compensation of inaccuracies through calibration and smart software control, while maintaining high accuracy by using concentric cylinders and contactless direct drive motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ball bearings are used in robotic arms, then positioning reproducibility is improved, but absolute accuracy deteriorates due to friction, play, and shifting behavior
Solution Approach 1:
The patent replaces traditional ball bearing mechanical joints with a leaf spring-based compliant mechanism. This substitution eliminates friction, play, and shifting behavior inherent in ball bearings, thereby improving absolute accuracy while maintaining positioning reproducibility through the elastic properties of the leaf springs.
Solution Approach 2:
The patent changes the mechanical parameters of the joint system by using leaf springs with specific elastic properties instead of rigid ball bearing connections. This parameter change allows for controlled deformation and rotation, improving absolute positioning accuracy by eliminating the cumulative errors from mechanical wear and play in traditional ball bearings.
2Ease of manufacture
If low-cost robot joints using leaf springs are used, then cost price is reduced, but position accuracy deteriorates because the point of rotation moves during rotation
Solution Approach 1:
The patent incorporates measuring means (sensors) that detect the actual position and orientation of the robot arm segments. This feedback is used by the control system to calculate and compensate for the movement of the rotation point, thereby maintaining position accuracy despite using low-cost leaf spring joints without expensive mechanical compensation mechanisms.
Solution Approach 2:
Instead of using expensive mechanical mechanisms to maintain a fixed rotation point, the patent substitutes a combination of leaf springs with integrated measuring means and software-based compensation. This approach achieves comparable accuracy at lower cost by using sensors and control algorithms rather than precision mechanical components.
3Manufacturing precision
If measuring means are integrated into rotatable elements, then position accuracy is improved through compensation, but device complexity increases
Solution Approach 1:
The patent merges the measuring means directly into the rotatable elements (leaf spring joints) themselves. This integration combines the structural and measurement functions into a single component, reducing the number of separate parts and simplifying assembly while enabling accurate position measurement for compensation purposes.
Solution Approach 2:
The measuring means are designed to be self-integrating with the rotatable elements, where the measurement components work together with the joint's natural movement characteristics. This self-service approach reduces the need for additional complex mounting and calibration mechanisms, thereby improving position accuracy without proportionally increasing device complexity.
4Ease of manufacture
If leaf springs are used for rotation, then cost is reduced and mechanical wear is minimized, but friction and play from traditional bearings must be eliminated
Solution Approach 1:
The patent replaces traditional ball bearing mechanical systems with leaf spring-based compliant joints. This substitution eliminates the friction and play inherent in ball bearings by using elastic deformation of the leaf springs for rotation, thereby improving reliability while reducing cost and mechanical wear.
Solution Approach 2:
The patent changes the fundamental mechanical parameters of the joint by transitioning from rigid ball bearing connections to flexible leaf spring connections. This parameter change eliminates friction and play by using controlled elastic deformation instead of mechanical contact, improving reliability while maintaining low cost and minimizing wear.
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 provides high accuracy and cost-effective robotic joints by integrating measuring means and contactless motors, enabling precise positioning and reducing mechanical wear, thus enhancing the reliability and efficiency of robotic arms.
Implementation Method 1
A disadvantage of such a robot joint is that the position of the elements relative to each other during rotation is not very accurate because the point of rotation moves during rotation
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A robot joint 1 has two adjacent outer cylinders 3 and 5 and an inner cylinder 7 which extends inside the two outer cylinders and is provided with openings 9 in the cylinder wall. The inner cylinder 7 is connected via leaf springs 11, 13 to the two outer cylinders. The robot joint is provided with measuring means comprising markings 15 which are formed by holes 15 in the cylinder wall of one of the outer cylinders 3, as well as detection means 17, 19 for counting the number of markings that passes the detection means during rotation of the two outermost cylinders 3, 5 relative to each other, which detection means are connected to the other outer cylinder 5. By measuring the rotation of the outer cylinders relative to each other and linking it back to the robot arm drive, the consequences of the inaccuracies in the joint can be compensated.