Articulated Arm Tool Pose Control During Joint Motion
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Solution Overview
Problem
Articulated arms and end effectors in medical devices face challenges in maintaining a stable tool pose due to motion-induced disturbances, which can lead to undesirable alterations, potentially causing injuries, damage, or breaches in a sterile field.
Innovation Solution
A control unit maintains the tool pose by determining a reference coordinate frame, calculating the reference and actual transforms, and adjusting the second joints based on the differences to compensate for motion in the first joints, ensuring consistent position and orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If redundant degrees of freedom are present in articulated arms to provide flexibility in control, then the flexibility in control of tool pose is improved, but the stability of tool pose deteriorates due to multiple possible joint combinations creating null spaces where joint movement does not affect tool pose
Solution Approach 1:
The control unit continuously monitors the actual tool pose and compares it with the desired pose, using feedback signals to adjust joint positions. This closed-loop control ensures that even with redundant degrees of freedom, the tool pose remains stable by actively correcting any deviations caused by joint movements in the null space.
Solution Approach 2:
The system changes the control parameters by transforming the joint space into a task space representation, where the control unit manages the redundancy by selecting appropriate joint configurations that maintain the desired tool pose. This parameter transformation allows the system to exploit redundant degrees of freedom while maintaining pose stability.
2Manufacturing precision
If articulated joints are manipulated to obtain desired position and orientation of the tool, then the precision of tool pose is improved, but the reliability deteriorates due to motion-induced disturbances that can cause undesirable alterations to the tool pose
Solution Approach 1:
The control unit continuously monitors the actual tool pose and compares it with the desired pose, using feedback signals to adjust joint positions. This closed-loop control ensures that even with joint movements, the tool pose remains stable by actively correcting any deviations caused by disturbances.
Solution Approach 2:
The system performs preliminary calculations of the desired joint positions and compensates for potential disturbances before they affect the tool pose. By predicting and preparing counter-measures in advance, the system maintains both precision and reliability of the tool pose.
3Ease of operation
If motion is allowed in articulated joints to provide flexibility and avoid collisions, then the ease of operation is improved, but the harmful effects worsen due to potential injuries, damage, and breach of sterile field
Solution Approach 1:
The control unit continuously monitors the actual tool pose and compares it with the desired pose, using feedback signals to adjust joint positions. This closed-loop control ensures that even with joint movements, the tool pose remains stable by actively correcting any deviations caused by disturbances.
Solution Approach 2:
The system replaces direct mechanical control with computational control, where the control unit calculates and executes precise joint movements based on real-time feedback. This substitution allows for more precise and controlled manipulation, reducing the risk of harmful effects while maintaining ease of operation.
Data Source
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AI summary
A system and method of maintaining a tool pose for a computer-assisted medical device with an articulated arm including one or more first joints and one or more second joints, a tool distal to the first joints and the second joints, and a control unit coupled to the first joints and the second joints. The control unit maintains a pose of the tool during movement of the first joints using the second joints by determining a reference coordinate frame for the tool, determining a reference transform of the tool in the reference coordinate frame prior to the movement of the first joints, determining an actual transform of the tool in the reference coordinate frame while the first joints are being moved, determining differences between the reference transform and the actual transform, and maintaining the pose of the tool by driving the second joints based on the differences.