Robot Mode Switching for Precise Torque-Controlled Gripping
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Solution Overview
Problem
Conventional robots face challenges in switching between position-regulated and torque-regulated operating modes efficiently, leading to issues with positional accuracy and stability, especially in tasks requiring precise gripping or manipulation, as they often require costly cycle times or unrealistic precision in shape and orientation knowledge.
Innovation Solution
A method that allows flexible switching between operating modes by determining an intermediate state through modeling the robot's motion in torque and axis spaces, using a spring model to identify an inflexion point for smooth mode transition, and adjusting stiffness settings to improve positional accuracy and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the robot is moved in position-regulated operating mode to approach the target position, then positional accuracy is improved, but the robot cannot reliably grip objects without unrealistic precise knowledge of their shape and orientation
Solution Approach 1:
The robot dynamically switches between position-regulated and torque-regulated operating modes based on the task requirements. The control system adapts the operating mode in real-time: using position-regulated mode for approach movements requiring accuracy, and torque-regulated mode for gripping tasks requiring adaptability to object properties without precise prior knowledge.
2Adaptability or versatility
If the robot is switched to torque-regulated operating mode for gripping, then gripping capability is improved, but positional accuracy deteriorates and the robot becomes prone to positional drifting
Solution Approach 1:
The control system dynamically adjusts the operating mode based on task phase. Position-regulated mode is used during approach and positioning phases to maintain high positional accuracy, while torque-regulated mode is activated only during the gripping phase where adaptability to object properties is more critical than positional precision.
3Ease of operation
If the robot is moved to a complete standstill before switching to torque-regulated mode for gripping, then mode switching is simplified, but cycle time increases and productivity decreases
Solution Approach 1:
The control system performs preliminary positioning in position-regulated mode to bring the robot close to the target position before switching to torque-regulated mode. This preliminary action reduces the distance that must be covered in torque mode, allowing for smoother transitions and eliminating the need for complete standstill, thereby reducing cycle time while maintaining operational simplicity.
4Productivity
If the robot uses torque-regulated operating mode to approach the target position, then cycle time is reduced, but positional accuracy deteriorates and the robot is susceptible to positional errors from disturbances
Solution Approach 1:
The control system dynamically selects the operating mode based on the approach phase. Position-regulated mode is used during the initial approach to ensure high positional accuracy and robustness against disturbances. Torque-regulated mode is then used for the final positioning and gripping phase to reduce cycle time, creating an optimized sequence that balances accuracy and productivity.
Data Source
Figure 1~2
AI summary
The invention relates to a method (6) for operating a robot as well as to a correspondingly operated robotic system. As part of the method (6) it is determined, if a difference between a current position of the robot and a target position of the robot exceeds a predetermined threshold value while the robot is in a torque-regulated operating mode (4). If the difference exceeds the threshold value, a predicted model-based intermediate state that the robot reaches before the target position according to the model is determined, wherein a speed of the robot in the intermediate state is lower than a predetermined speed threshold. When the robot reaches the intermediate state, the robot is automatically switched from the torque-regulated operating mode (4) to a position-regulated operating mode (3). The robot then moves into the target position in the position-regulated operating mode (3).