End Effector Force Sensing for Assisted Robotic Arm Repositioning
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Solution Overview
Problem
Conventional robotic arms used in image-guided medical procedures can be awkward and difficult to manually position due to their heavy mass and mechanical resistance, making it tiresome for surgeons to correct positioning errors, which can also lead to contamination risks.
Innovation Solution
An automated positioning system equipped with a force-moment sensor (FMS) that detects external forces and torques applied to the end effector, allowing motors to assist the user in moving the positioning arm, thereby facilitating smoother and easier manual actuation through intelligent assistive control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a conventional robotic arm is used for positioning medical instruments, then automated positioning can be achieved, but the arm becomes difficult and tiring to manually reposition when corrections are needed
Solution Approach 1:
The robotic arm transitions between locked automated mode and unlocked manual mode dynamically. The lock mechanism allows the arm to be held firmly during automated operation but can be quickly released for manual repositioning, adapting the system's degree of freedom based on operational needs.
Solution Approach 2:
A force-moment sensor acts as an intermediary between the surgeon's manual input and the robotic arm's movement. The sensor detects forces applied by the surgeon and translates them into controlled arm movements, facilitating smooth transition and reduced effort during manual repositioning.
2Manufacturing precision
If multiple manual forces are applied at multiple segments of the robotic arm to correctly position it, then positioning accuracy can be achieved, but the complexity and time required increases
Solution Approach 1:
The force-moment sensor extracts and measures the forces applied at the end effector, allowing the system to calculate the necessary compensatory movements at each joint. This eliminates the need for the surgeon to manually force multiple joints, as the sensor data drives automated compensation.
Solution Approach 2:
The force-moment sensor provides real-time feedback on forces applied during manual repositioning. The controller uses this feedback to calculate and execute compensatory joint movements, ensuring accurate final positioning without requiring the surgeon to manually coordinate multiple joints.
3Ease of operation
If the robotic arm is manually moved against heavy mass and mechanical resistance, then repositioning can be achieved, but the surgeon experiences fatigue and increased contamination risk
Solution Approach 1:
The motors provide counteracting forces that compensate for the heavy mass and mechanical resistance of the robotic arm. When the surgeon applies manual force, the motors generate opposing forces to balance the arm's weight and resistance, making repositioning effortless and reducing fatigue.
Solution Approach 2:
The force-moment sensor and control system act as intermediaries that translate small surgeon inputs into coordinated motor responses. This intermediary system amplifies the surgeon's effort while maintaining precise control, eliminating the need for the surgeon to directly overcome the arm's heavy mass and resistance.
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 system enables more precise and efficient manual positioning of the robotic arm, reducing fatigue and contamination risks while allowing for more intuitive control of medical instruments during procedures.
Implementation Method 1
a force-moment sensor (FMS) that detects external forces and torques applied to an end effector
Data Source
AI summary
An automated positioning system and methods of controlling the same. The positioning system includes a multi-joint positioning arm, an end effector coupled to a distal end of the positioning arm, a force-moment sensor (FMS) coupled to the end effector and a controller coupled to communicate with the positioning arm and the FMS. Using signals from the FMS, at least one external force or torque applied to the end effector is determined. A drive velocity for moving the end effector is determined, based on the at least one external force or torque. One or more joint movements of the positioning arm for moving the end effector is calculated, according to the drive velocity. The positioning arm is moved according to the one or more calculated joint movements.