Surgical Robot Arm Motor Calibration for Precise Instrument Force
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Solution Overview
Problem
Calibration of motor currents in surgical robot arms is crucial for ensuring consistent force delivery to surgical instruments, particularly for gripping actions, but existing methods are inadequate for precise calibration of driving forces.
Innovation Solution
A calibration rig is used to determine the relationship between motor currents and resistive forces, allowing for the calibration of motor currents to achieve desired driving forces by engaging with the drive interface elements of the surgical robot arm and measuring resistive forces using a damper and force sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing calibration methods are used for motor currents in surgical robot arms, then the calibration process can be completed, but the precision and accuracy of force delivery to surgical instruments is insufficient
Solution Approach 1:
A calibration rig is introduced as an intermediary device between the motor and the surgical instrument. The rig includes a drive interface element that engages with the drive interface element of the robot arm, allowing precise measurement of driving forces and resistive forces during calibration. This intermediary setup enables accurate determination of the relationship between motor currents and actual forces applied to the instrument.
Solution Approach 2:
The patent replaces traditional mechanical calibration methods with a sensor-based measurement system. Force sensors and encoders are used to directly measure driving forces and positions, replacing indirect mechanical assumption-based calibration. This substitution of mechanical systems with sensor-based systems significantly improves measurement precision and calibration accuracy.
2Measurement precision
If a calibration rig with force sensors is used to measure driving forces, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The calibration rig is designed to be universally applicable to different surgical instruments and robot arm configurations. The drive interface element can engage with various types of drive interface elements, and the system can calibrate multiple motors through repeated procedures. This multi-functionality reduces the need for multiple specialized calibration devices, thereby managing complexity while maintaining measurement precision.
Solution Approach 2:
The calibration procedure is designed to be performed preliminarily before surgical operations. All calibration measurements and adjustments are completed in advance, establishing accurate motor current to force relationships before actual use. This preliminary action ensures that the complex calibration system is only set up once, rather than requiring continuous complex measurements during surgical procedures.
3Reliability
If precise calibration of motor currents is performed, then force delivery consistency is improved, but calibration time and procedural complexity increase
Solution Approach 1:
The calibration system uses periodic test sequences where a series of test motor currents are applied in sequence, and corresponding resistive forces are measured for each. This periodic application of test currents allows systematic characterization of the motor-force relationship across the full operating range, ensuring comprehensive calibration while following a structured time-efficient procedure.
Solution Approach 2:
The calibration process incorporates feedback loops where measured resistive forces are used to determine calibration values that are then applied to adjust motor currents. The system iteratively refines the calibration by comparing expected forces with measured forces and adjusting accordingly. This feedback mechanism ensures accurate force delivery consistency while automating the calibration process to reduce manual intervention time.
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 calibration method ensures accurate and consistent force delivery to surgical instruments, improving the precision and reliability of surgical procedures by aligning motor currents with desired driving forces.
Implementation Method 1
receiving a measured resistive force applied by a calibration rig, the calibration rig applying the resistive force in response to the rig interface element being driven by the drive interface element
Data Source
AI summary
A method for calibrating a surgical robot arm motor includes running a test sequence. The test sequence includes controlling a set of test motor currents to be applied to the motor, each causing the motor to drive a drive interface element to move; and for each test motor current, receiving a measured resistive force applied by a calibration rig; determining a relationship between the set of test motor currents and the resistive force measurements; determining calibration value(s) from: (i) the determined relationship, and (ii) a known relationship between the resistive force applied by the calibration rig and the driving force applied by the drive interface element; and controlling the calibration value(s) to be applied to subsequent motor currents applied to the motor so as to cause the motor to drive the drive interface element to apply desired driving forces to an instrument interface element of an attached surgical instrument.