Motion Terminal Position Calibration for Backlash Error Correction

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Solution Overview

Problem

Radiotherapy devices face positioning accuracy issues due to backlash errors in motion terminals driven by transmission devices like screw drives, leading to inconsistencies between intended and actual positions of components like multi-leaf collimators, affecting treatment precision.

Innovation Solution

A method and system that utilize dual sensors (e.g., encoder and Hall sensor) to measure displacements, calculate an offset value, and determine a calibration displacement to correct position errors, ensuring accurate positioning of motion terminals by adjusting the driving component's displacement values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a transmission device (e.g., screw drive or gear drive) is used to drive the motion terminal, then the motion terminal can be driven to the target position, but a position error caused by backlash is generated, decreasing the positioning accuracy

Engineering Contradiction:

Improvepositioning accuracyVSAvoidtransmission device structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The system performs preliminary action by acquiring displacement measurements from both the driving component and the motion terminal before actual positioning operations, calculates offset values in advance, and establishes a calibration displacement relationship that is stored for subsequent use. This preliminary calibration process eliminates the need for complex mechanical adjustments during operation, resolving the contradiction by preparing correction data beforehand that simplifies the operational phase while maintaining high positioning accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex mechanical adjustment mechanisms with an electronic calibration system. Instead of using complex mechanical structures to eliminate backlash errors, the system uses sensors to acquire displacement data, processors to calculate offset values, and electronic storage to save calibration relationships. This substitution of mechanical correction mechanisms with electronic measurement and calculation systems resolves the contradiction by achieving high positioning accuracy through software-based correction rather than complex mechanical design.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If the screw rod changes direction, then the screw nut may not move until the backlash is eliminated, but this causes the movement of the screw nut to lag behind the screw rod, generating a backlash error

Engineering Contradiction:

Improvemotion transmissionVSAvoidposition accuracy

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The system implements feedback by acquiring displacement information from both the driving component (screw rod) and the motion terminal (screw nut) using sensors, comparing these measurements to identify backlash errors, and using the calculated offset values to correct the positioning. This feedback mechanism continuously monitors the motion transmission process and compensates for directional changes and backlash, resolving the contradiction by maintaining position accuracy despite the inherent lag in mechanical transmission.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies parameter changes by measuring the actual displacement parameters of both the driving component and the motion terminal, calculating the offset parameter that represents the backlash error, and using this parameter to adjust the target position. By changing from using only the driving component's displacement parameter to using the difference between driving component displacement and actual motion terminal displacement, the system compensates for backlash effects and maintains positioning accuracy during directional changes.

Inventive Principle:

Principle #35Parameter changes

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

Enhances the positioning accuracy of motion terminals in radiotherapy devices by compensating for backlash errors, thereby improving the precision of radiation field adjustments and treatment outcomes.

Implementation Method 1

a first sensor associated with the driving component, the first sensor being configured to acquire a first movement displacement of the motion terminal inputted by the driving component

Methodology Applied

Scientific EffectEncoder measurement:

Implementation Method 2

a second sensor associated with the motion terminal, the second sensor being configured to acquire a second movement displacement of the motion terminal

Methodology Applied

Scientific EffectHall effect: Hall Effect

Data Source

PatentUS10960227B2Systems and methods for correcting a position error of a motion terminal

Publication Date: 2021.03.30 SHANGHAI UNITED IMAGING HEALTHCARE

AI summary

A method for correcting a position error for a motion terminal driven by a driving component may include obtaining a first displacement of the motion terminal acquired by a first sensor associated with the driving component. The method may also include obtaining a second displacement of the motion terminal acquired by a second sensor associated with the motion terminal. The method may further include determining an offset value based on a difference between the first displacement and the second displacement. The method may include determining a calibration displacement value relating to the first displacement based on the offset value.