Control Valve Positioning System with Backlash Calibration
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Solution Overview
Problem
Existing systems for precise positioning of rotary devices, such as brushless DC motors, face inaccuracies due to backlash in gears and spring-like responses, leading to discrepancies between sensed and actual positions, which can result in undesirable component positioning.
Innovation Solution
An electromechanical system that uses sensors to determine the apparent position of a rotary device based on rotation of permanent magnets and accounts for both desired and undesired directions of rotation, with a control mechanism to calibrate the actual position by comparing it to an expected position and adjusting for differences, utilizing a counter to track valid pulses and account for spring forces when the motor is stopped.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gear speed change arrangements are used between motor shaft and component shaft, then speed reduction and torque multiplication are achieved, but backlash and spring-like responses cause position discrepancies
Solution Approach 1:
The system uses continuous position monitoring and comparison between actual and expected positions to detect errors introduced by gear backlash and spring-like responses. The calibration function periodically re-establishes accurate position mapping by moving the component to reference positions, compensating for the cumulative effects of mechanical play in the gear train.
Solution Approach 2:
The system changes the operational parameters by periodically performing calibration routines that move the component through its full range of motion to reference positions. This dynamic recalibration adjusts the position mapping parameters to account for changes in backlash and spring-like responses that may occur during operation, maintaining position accuracy despite the mechanical transmission elements.
2Measurement precision
If calibration is performed frequently to maintain position accuracy, then position precision is improved, but system complexity and calibration time increase
Solution Approach 1:
Instead of performing full calibration routines continuously, the system uses a threshold-based approach that triggers calibration only when position discrepancies exceed a predetermined amount. This partial action approach maintains position precision by calibrating only when necessary, reducing the overall calibration frequency and system complexity while still compensating for position drift caused by backlash and spring effects.
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
This approach provides a more accurate determination of the actual position of the component, ensuring it aligns closely with the desired position by identifying and correcting for discrepancies through calibration, thereby improving positional accuracy.
Implementation Method 1
sensors for determining an apparent position of the component based upon rotation of the permanent magnets
Implementation Method 2
the shafts have a spring like response to the torque from the motor to the component
Implementation Method 3
backlash within the gears due to torsional spring features
Data Source
Figure 1A~1B
Figure 2~3
AI summary
An electromechanical system (20) has a component (42) to be positioned, a rotary permanent magnet motor (24) for positioning the component (42), and sensors (30) for determining an apparent position of the component (42) based upon rotation of the permanent magnets. A control (40) counts movement of the permanent magnets that pass the sensors (30) in a desired direction and also in an undesired direction. The control (40) reaches an actual position of the component (42) based upon both directions of rotation. The control (40) also compares the actual position to an expected position of the component (42) and identifies a need to calibrate should a difference between the actual and expected positions differ by more than a determined amount. A method is also disclosed.