Motor Control for Surgical Instrument Mechanical Limit Detection
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Solution Overview
Problem
Existing surgical devices with powered drive systems for linear clamping, cutting, and stapling require multiple mechanical limit sensors and switches, increasing complexity and cost, and are not compatible with devices using rotary motion, necessitating a more efficient method for detecting mechanical limits.
Innovation Solution
A surgical instrument with a motor and controller that measures current draw and angular velocity, calculating instantaneous rates of change to detect mechanical limits and terminate power supply, allowing for early collision detection and motor calibration without relying on multiple sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple mechanical limit sensors and switches are used to detect operational state, then the reliability of detecting mechanical limits is improved, but the device complexity and cost increase
Solution Approach 1:
The patent extracts the mechanical limit detection function from multiple separate sensors and switches and consolidates it into a single controller that uses motor current and speed measurements. This removes unnecessary components while maintaining detection capability through mathematical analysis of motor parameters during actuation.
Solution Approach 2:
The controller is designed to perform multiple functions: it controls motor actuation, monitors motor current and speed, detects mechanical limits, and prevents damage. By making the controller universal, the patent eliminates the need for dedicated limit sensors and switches, reducing device complexity while maintaining reliability.
2Reliability
If multiple switches and sensors are included to detect operational state, then the reliability of mechanical limit detection is improved, but the cost of the surgical device increases
Solution Approach 1:
The patent extracts the limit detection function from expensive dedicated sensors and switches and implements it through software-based analysis in the controller. This eliminates hardware costs while maintaining detection reliability through mathematical processing of motor parameters.
Solution Approach 2:
The motor itself serves as the sensor by providing its own diagnostic information through current and speed measurements. The controller analyzes these self-provided signals to detect mechanical limits, eliminating the need for external sensing components and reducing overall device cost.
3Productivity
If the motor continues to supply power after reaching mechanical limit, then the productivity is maintained, but the risk of component damage increases
Solution Approach 1:
The controller continuously monitors motor current and speed, calculating their derivatives to detect when mechanical limits are reached. When the derivative of current is positive and derivative of speed is negative (indicating a hard stop), the controller provides feedback to shut off power, preventing component damage while allowing continuous operation during normal conditions.
Solution Approach 2:
The controller detects approaching mechanical limits before actual damage occurs by monitoring the derivatives of current and speed. It takes preliminary action to shut off power before the motor can cause harmful effects, preventing component damage while maintaining productivity during normal operation.
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 early detection of mechanical limits, reducing the risk of damage to components, conserving power, and simplifying the system by eliminating the need for multiple sensors, while allowing for precise calibration and efficient operation.
Implementation Method 1
A motor control circuit measures a current draw of the motor and an angular velocity of the motor
Implementation Method 2
The controller may be configured to calculate an instantaneous rate of change of each of the current draw of the motor and the angular velocity of the motor
Implementation Method 3
The controller may also be configured to terminate the supply of electrical current to the motor from the power supply in response to detection of the mechanical limit
Data Source
AI summary
A surgical instrument includes: an end effector; a power source; a motor coupled to the power source, the motor configured to actuate the end effector; and a controller operatively coupled to the motor and configured to control the motor based on a current draw of the motor and an angular velocity of the motor.