Ball Screw Preload Loss Detection Using Vibration Frequency Bands
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Solution Overview
Problem
Existing methods for detecting abnormalities in ball screws, such as PTL 1, 2, and 3, are inadequate for detecting decreased preload due to wear, as they require prior calculations and comparison with normal product vibration signals, and cannot distinguish between damage and preload loss.
Innovation Solution
A method involving vibration measurement, calculation processing to acquire a vibration value in a specific frequency band, and abnormality detection to determine preload decrease by comparing the value with a threshold based on initial operation reference values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior calculation methods (shaft rotation frequency, ball revolution cycle, ball-passing signal) are used for abnormality detection, then detection accuracy for specific abnormalities is improved, but device complexity and operational difficulty increase
Solution Approach 1:
The patent extracts only the essential vibration signal measurement function, removing the complex calculation processing steps (shaft rotation frequency calculation, ball revolution cycle calculation, ball-passing signal generation) required by prior art. The solution uses direct vibration signal comparison with reference values, eliminating unnecessary computational complexity while maintaining detection capability.
Solution Approach 2:
Instead of calculating multiple derived parameters (rotation frequency, revolution cycle, ball-passing signal) from vibration data as in prior art, the patent inverts the approach by directly using the raw vibration signal values and comparing them with reference values. This reversal eliminates the need for complex forward calculations.
2Reliability
If comparison with normal product vibration signals is required, then detection reliability is improved, but ease of operation deteriorates due to need to acquire reference signals
Solution Approach 1:
The patent applies preliminary action by pre-acquiring vibration signals during the initial operation stage of the ball screw and storing them as reference values. This preliminary reference data is then used for subsequent abnormality detection, eliminating the need for operators to manually acquire normal product signals at the time of detection and simplifying operation.
3Measurement precision
If existing vibration analysis methods are used, then detection capability for damage (indentation, peeling) is improved, but ability to detect preload decrease deteriorates
Solution Approach 1:
The patent applies universality by creating a detection method that serves multiple functions: it can detect both traditional abnormalities (indentation, peeling) through vibration signal analysis and newly the specific condition of preload decrease. The same vibration measurement and reference comparison mechanism handles both detection tasks, making the system versatile.
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 detection of decreased preload without requiring prior calculations or comparison with normal product signals, effectively monitoring preload loss due to wear by using existing vibration measuring devices.
Implementation Method 1
a vibration measurement step of measuring vibration during operation of the ball screw
Data Source
AI summary
A linear motion drive device including a ball screw, a linear motion table driven by the ball screw to move linearly, and an abnormality detection device configured to detect a decrease in a preload applied to the ball screw. The abnormality detection device includes a vibration sensor configured to measure vibration during operation of the ball screw, a calculation processing unit configured to acquire a vibration value of a vibration signal in a specific frequency band among vibration signals measured by the vibration sensor, and an abnormality detection unit configured to determine that a decrease in the preload has occurred in the ball screw when the vibration value is less than a previously determined threshold with respect to a reference value, the reference value being a vibration value in an initial stage of the operation of the ball screw or during a normal operation of the ball screw.