Surgical Instrument Drive Unit with Flexure Shaft
Solution Overview
Problem
Existing surgical robotic systems face challenges in providing sufficient rotational freedom and precise torque control for surgical instruments, which are crucial for minimally invasive procedures.
Innovation Solution
The robotic arm assembly incorporates an instrument drive unit with a casing that rotates about a longitudinal axis, featuring a cluster of electric motor assemblies and encoders. This setup provides five degrees of rotational freedom and includes flexure sections in the output shaft to accommodate torque loads, along with proximal and distal encoders to determine rotational positions and calculate torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional motor assembly with a rigid output shaft is used, then the structure is simple, but the system cannot accommodate torque loads and achieve precise rotational position measurement under load
Solution Approach 1:
The output shaft is segmented into multiple sections including a first section, a flexure section, and a second section. This segmentation allows the shaft to flex under torque loads while maintaining structural integrity, enabling accurate rotational position measurement even when the shaft is subjected to mechanical stress during surgical procedures
Solution Approach 2:
A flexure section is introduced as an intermediary element between the motor assembly and the surgical instrument. This flexure section acts as a mediator that can elastically deform under torque loads, allowing the rigid encoder components to remain stationary while the surgical instrument experiences the necessary mechanical compliance for precise positioning
2Adaptability or versatility
If five degrees of rotational freedom are provided for complex surgical maneuvers, then the versatility is improved, but the device complexity increases
Solution Approach 1:
Multiple motor assemblies are merged into a single integrated instrument drive unit that provides five degrees of rotational freedom. The casing itself is designed to rotate about a longitudinal axis, while additional motors provide rotation about other axes, combining multiple rotational capabilities into one unified device that interfaces with the surgical instrument
Solution Approach 2:
The instrument drive unit is designed as a multi-functional device that can provide rotation about multiple axes (five degrees of freedom) to accommodate various surgical maneuvers. The same drive unit structure supports both the rotation of the casing about the longitudinal axis and the additional rotational movements required for complex surgical tasks
3Measurement precision
If accurate torque control is implemented using encoders, then the control precision is improved, but the device complexity and cost increase
Solution Approach 1:
Encoders are installed to measure the rotational position of the output shaft with high precision. This feedback information is used to accurately determine torque applied to the surgical instrument, enabling closed-loop control that maintains precise torque levels during surgical procedures while compensating for variations in tissue resistance and instrument positioning
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 solution enhances the robotic arm's ability to perform complex surgical maneuvers with high precision, offering improved rotational freedom and accurate torque control, which are essential for effective minimally invasive surgeries.
Implementation Method 1
a plurality of flexure sections positioned between the proximal and distal end portions of the output shaft and configured to flex under a torque load
Implementation Method 2
One of the electric motor assemblies includes a magnetic rotor rotatably supported in the casing, a motor stator coil fixed to and positioned within the casing
Data Source
AI summary
A surgical robotic system for use in a minimally invasive surgical procedure includes an instrument drive unit having five degrees of rotational freedom.