Surgical Tool Arm Force Control for Stable Port Positioning
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Solution Overview
Problem
Existing arm devices for surgery assistant robots impose loads on a subject's body during endoscopic surgery due to changes in the position and posture of surgical tools caused by externally applied forces, which can be exacerbated by errors in port positioning recognition.
Innovation Solution
An arm device with a joint portion, actuator, estimator, and controller that estimates external forces and adjusts driving forces based on the tool's weight and external force to maintain the surgical tool's position and posture, using gas-pressure actuators to allow rotation in response to applied forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a robotic arm system with multiple degrees of freedom is designed to achieve various postures and positions, then the versatility and adaptability are improved, but the device complexity and control difficulty increase significantly
Solution Approach 1:
The robotic arm is divided into multiple independent degrees of freedom (joints 1-6), each controlled by a separate actuator. This segmentation allows each joint to be controlled independently, reducing the overall control complexity while maintaining high versatility for achieving various postures and positions.
Solution Approach 2:
The system employs dynamic control where the control unit adjusts the degree of freedom of each joint in real-time based on the desired end effector position and posture. This dynamic adjustment allows the arm to adapt to different tasks and configurations without requiring a completely different system design.
2Productivity
If the arm is designed to move quickly and accurately to various positions, then the productivity and speed are improved, but the stability and precision maintenance become more difficult
Solution Approach 1:
The control unit receives feedback from sensors about the actual position and posture of the end effector, and continuously adjusts the joint degrees of freedom to minimize the difference between desired and actual positions. This closed-loop feedback control maintains high positioning precision even during rapid movements.
Solution Approach 2:
The control unit calculates and prepares the required joint degrees of freedom in advance based on the desired end effector position and posture, before actually executing the movement. This preliminary calculation ensures that the arm can move quickly while maintaining precision by having the control parameters ready beforehand.
3Adaptability or versatility
If a force system is provided at the end effector to apply force to objects, then the functional capability is improved, but the device complexity and control difficulty increase
Solution Approach 1:
The end effector is designed with a universal force system that can apply forces in multiple directions (Fx, Fy, Fz) and generate moments (Mx, My, Mz) through the same actuator system. This multi-functional design allows the end effector to perform various tasks (pushing, pulling, twisting) without requiring separate dedicated mechanisms for each function.
Solution Approach 2:
The control unit acts as an intermediary that translates high-level force application requirements into specific joint degree of freedom adjustments. Rather than directly controlling complex force mechanisms at the end effector, the control unit mediates by adjusting the simpler joint parameters, thereby reducing control complexity while maintaining force application capability.
Data Source
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AI summary
An arm device includes a joint portion configured to be rotated to thereby change a position and/or a posture of a surgical tool, and an actuator configured to generate a driving force that rotates the joint portion, and to allow a rotation of the joint portion in accordance with an externally applied force. Moreover, the arm device is configured to estimate an external force applied to the surgical tool, to obtain a value of a driving force of the actuator based on a weight of the surgical tool and the external force, and to control the actuator based on a value of the driving force.