Enhancing Robotic Milling Capabilities through Mechatronic Coupling of Industrial Robots

Conceitos Básicos

Coupling two industrial robots at the flanges can enhance the dynamic stiffness of a robotic milling system, enabling the shifting of natural frequencies to suppress chatter.

Resumo

The paper proposes a new robotic milling system that consists of two industrial robots coupled at the flanges using a passive mechanical coupling module. The key insights are:

Modal analysis experiments confirmed that the natural frequencies of the coupled system can be shifted by applying tension to the coupling module. This enables the suppression of chatter in robotic milling applications.

The coupled system exhibits a more uniform stiffness distribution across the workspace compared to a single robot, making the natural frequencies easier to predict.

Milling experiments showed that it is possible to machine a workpiece even under tension forces, though the deformation of the system needs to be compensated for. A model to predict the deformation based on the tension forces and robot positions is identified as future work.

The redundant degrees of freedom introduced by the coupling can be exploited to shift the natural frequencies, which is a novel approach compared to prior work on overactuated milling systems.

Overall, the proposed coupled robotic milling system shows promise in addressing the key challenges of robotic milling, such as low dynamic stiffness and chatter, through the strategic use of mechatronic coupling.

Estatísticas

The modal analysis experiments showed a shift in the natural frequency in the x-direction from 159 Hz without tension to 202 Hz with 2000 N of tension force.
The deformation of the coupling module under 1000 N of tension force reached up to 2 mm in the y-direction and 1.2 mm in the z-direction.

Citações

"We hypothesize that due to the nonlinearities of the real system, the resonant frequency will shift. In turn, shifting natural frequencies has been shown as an effective strategy to suppress chatter [7] in robotic applications."
"Comparing the results of the x direction with the results of the y direction which is plotted in Figure 5 we observe that the frequency shift starts at much higher frequencies. While we observe a similar shift in natural frequencies, the natural frequency is too high to be relevant for chatter suppression."
"Applying this transformation to our measured tensioned path, we see that the deformation is almost completely compensated. This is a promising result as without any compensation the milling system would be unusable under tension forces."

Principais Insights Extraídos De

Milling using two mechatronically coupled robots

by Max ... às arxiv.org 04-18-2024

https://arxiv.org/pdf/2404.11271.pdf

Perguntas Mais Profundas

How can the deformation of the coupled system under tension be accurately predicted based on the tension forces and robot positions?

To accurately predict the deformation of the coupled system under tension based on tension forces and robot positions, a comprehensive model incorporating the mechanical properties of the system is essential. Here are the steps to achieve accurate prediction:

Develop a Detailed System Model: Create a detailed model of the coupled system, including the robots, coupling module, and the workpiece. This model should consider the stiffness properties of the robots, the coupling module, and any other relevant components.

Incorporate Tension Force Model: Develop a model that relates the tension forces applied to the coupling module to the resulting deformation of the system. This model should consider the material properties, geometry, and attachment points of the coupling module.

Calibrate the Model: Use experimental data to calibrate and validate the model. Measure the deformation of the system under different tension forces and robot positions to refine the accuracy of the model.

Utilize Robot Position Feedback: Implement a feedback system that continuously monitors the positions of the robots during operation. This real-time data can be used to adjust the tension forces and predict the resulting deformation.

Machine Learning and AI: Consider employing machine learning algorithms or artificial intelligence techniques to analyze the complex relationships between tension forces, robot positions, and system deformation. These advanced tools can enhance the accuracy of the prediction model.

By following these steps and continuously refining the model based on experimental data, it is possible to accurately predict the deformation of the coupled system under tension forces based on the robot positions.

What are the limitations of the proposed approach in terms of the maximum achievable tension forces and the resulting frequency shifts?

The proposed approach of coupling two robots at the flanges to enhance dynamic stiffness and suppress chatter in milling processes has several limitations:

Maximum Achievable Tension Forces: The maximum achievable tension forces are limited by the mechanical properties of the coupling module and the robots themselves. Excessive tension forces can lead to structural deformation or failure of the components. Therefore, there is a practical limit to the tension forces that can be applied without compromising the integrity of the system.

Frequency Shifts: While tension forces can effectively shift the natural frequencies of the system, there are limitations to the extent of these shifts. The relationship between tension forces and frequency shifts may not be linear across all frequency ranges. Additionally, the system's non-linearities may introduce complexities in predicting the exact frequency shifts under different tension forces.

Complexity of Control: Implementing a control system that accurately adjusts tension forces to achieve desired frequency shifts can be complex. Real-time monitoring and adjustment of tension forces based on robot positions require sophisticated algorithms and sensors, adding to the system's complexity.

Material Compatibility: The proposed approach may be limited by the material compatibility of the workpiece being machined. Certain materials may not respond well to the application of tension forces, leading to unpredictable deformations or machining inaccuracies.

Scalability: Extending the coupling concept to more than two robots may introduce challenges in system coordination, control, and stability. As the number of coupled robots increases, the complexity of the system also grows, potentially impacting performance and reliability.

Could the coupling concept be extended to more than two robots to further enhance the dynamic stiffness and chatter suppression capabilities?

Extending the coupling concept to more than two robots can indeed enhance the dynamic stiffness and chatter suppression capabilities of the system. Here are the potential benefits and considerations of coupling multiple robots:

Increased Stiffness: By coupling multiple robots in a parallel kinematic structure, the overall stiffness of the system can be further enhanced. Redundant degrees of freedom from additional robots can contribute to a more rigid and stable machining platform.

Redundancy for Chatter Suppression: Additional robots provide more redundant actuators that can be utilized to shift natural frequencies and suppress chatter effectively. The increased redundancy allows for more flexibility in controlling the system's dynamics.

Expanded Workspace: With more robots working in coordination, the workspace of the system can be expanded, enabling the machining of larger and more complex workpieces without compromising stiffness or accuracy.

Improved Load Distribution: Distributing the machining load among multiple robots can reduce individual robot fatigue and wear, leading to longer system lifespan and improved machining quality.

Control and Coordination Challenges: Extending the coupling concept to multiple robots introduces challenges in control and coordination. Synchronizing the movements of multiple robots, adjusting tension forces, and ensuring stability across all axes require advanced control algorithms and precise feedback mechanisms.

System Scalability: The scalability of the system with multiple coupled robots should be carefully considered. As the number of robots increases, the complexity of the system grows, impacting maintenance, calibration, and overall system performance.

In conclusion, extending the coupling concept to more than two robots can offer significant advantages in terms of stiffness, chatter suppression, and workspace flexibility. However, it also introduces challenges in control, coordination, and scalability that need to be addressed for successful implementation.