Surgical Manipulator Input Device with Variable Reduction Ratios
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Solution Overview
Problem
Conventional surgical manipulators with speed reducers hinder light movement of input devices due to increased drag, making it difficult for operators to maneuver them effectively.
Innovation Solution
The design incorporates an input device with an arm unit and a wrist unit, each with specific reduction ratios (0.5 to 30) for motors and joints, along with auxiliary springs to counteract gravity, allowing for lighter movement and reduced motor load, while maintaining posture control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a speed reducer is provided between the motor and the link of the input device, then the motor can drive the link with reduced speed and increased torque, but the operator cannot move the input device lightly due to increased frictional drag
Solution Approach 1:
The patent applies dynamics by making the reduction ratio variable rather than fixed. The reduction ratio is changed dynamically based on the operational state: a first reduction ratio is used when the motor drives the link, and a second (smaller) reduction ratio is used when the operator manually moves the input device. This dynamic adjustment allows the system to optimize between motor-driven performance and manual operability.
Solution Approach 2:
The patent changes the parameter of reduction ratio according to different operational modes. By adjusting the reduction ratio parameter between a first value (for motor-driven operation) and a second value (for manual operation), the system resolves the contradiction between needing high torque for motor driving and low friction for light manual movement.
2Ease of operation
If the reduction ratio is decreased to reduce frictional drag, then the input device can be moved more lightly, but the operation distance required for the operation unit to move the surgical manipulator by a predetermined distance increases
Solution Approach 1:
The patent dynamically adjusts the reduction ratio based on operational needs. When manual movement is required, a smaller reduction ratio is applied to reduce friction and enable light movement. When precise positioning or force multiplication is needed, a larger reduction ratio can be applied. This dynamic switching resolves the contradiction between operation ease and movement distance.
Solution Approach 2:
By changing the reduction ratio parameter between different operational phases, the patent optimizes both the friction characteristics and the operation distance. The system selects appropriate reduction ratio values to balance the trade-off between light movability and operational efficiency.
3Weight of stationary object
If the reduction ratio in the arm unit is increased to reduce motor size, then the motor can be made smaller, but the frictional drag increases making the input device harder to move
Solution Approach 1:
The patent applies different reduction ratios to different units (arm unit and wrist unit) dynamically. The arm unit, which has a larger impact on overall friction, is assigned a smaller reduction ratio to maintain light movability. The wrist unit, which has less impact on overall friction, can have a larger reduction ratio to reduce its motor size. This differential dynamic assignment resolves the contradiction.
Solution Approach 2:
The patent applies local quality by assigning different reduction ratios to different parts of the system (arm unit vs. wrist unit). The arm unit uses a smaller reduction ratio to prioritize movability, while the wrist unit uses a larger reduction ratio to prioritize motor size reduction. This localized differentiation resolves the contradiction at each specific location.
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
Enables operators to move the input device lightly and maintain posture stability, improving operability and reducing motor size, with the wrist unit having a larger reduction ratio than the arm unit to minimize frictional drag.
Implementation Method 1
an auxiliary spring that generates a force to apply to the arm unit and the wrist unit
Implementation Method 2
a rotation angle sensor that detects a rotation angle of the motor or the joint
Data Source
AI summary
An operation device for a surgical manipulator includes an input device that operates the surgical manipulator. The input device includes a plurality of joints and a plurality of motors that drives the plurality of joints, and reduction ratios in power transmission paths from the plurality of motors to the plurality of joints, respectively, are 0.5 or more and 30 or less.