Radial Force Sensing in Ball Screws for Accurate Preload Monitoring
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Solution Overview
Problem
Existing ball screws with axial force sensors cannot accurately measure preload separately from motor thrust, affecting the measuring accuracy of the preload due to the axial direction alignment of the force sensor.
Innovation Solution
A ball screw with a force sensor in the radial direction, featuring a screw rod, screw nut, and force sensor with a stationary base and elastic component, where the force sensor is positioned in the screw nut's cavity to measure preload component forces independently of axial motor thrust by utilizing a displacement restraint and strain sensors to detect deformation in the radial direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an axial force sensor is installed in the screw nut to measure preload, then the ball screw can monitor preload change in real time, but the axial force sensor cannot separate motor thrust from preload, affecting measurement accuracy
Solution Approach 1:
The patent changes the sensing dimension from axial direction to radial direction. The force sensor measures preload component forces in the radial direction, which is perpendicular to the motor thrust direction. This dimensional change allows the preload to be measured independently without being affected by the axial motor thrust, thereby separating the measurement of preload from motor thrust and improving measurement accuracy.
2Reliability
If a force sensor is installed in the screw nut, then preload monitoring is enabled, but the sensor measures combined force of motor thrust and preload, reducing measurement precision
Solution Approach 1:
The force sensor is configured to measure in the radial direction rather than the axial direction. This allows the sensor to detect only the preload component forces acting radially on the ball screw, excluding the axial motor thrust from the measurement. The radial measurement approach maintains reliable preload monitoring while achieving precise separation of preload from motor thrust.
3Measurement precision
If the screw nut is made movable along the radial direction, then the force sensor can detect radial forces, but the screw nut structure becomes more complex
Solution Approach 1:
The screw nut is divided into functional segments: a movable portion that detects radial forces and a stationary base that provides structural support. The force sensor is installed in the movable portion, which can move radially to detect preload component forces. This segmentation allows radial force detection while the stationary base maintains structural stability, managing the complexity through functional division.
Solution Approach 2:
The movable portion of the screw nut acts as an intermediary between the radial preload forces and the force sensor. It transmits the radial forces to the sensor while isolating the sensor from the complex axial thrust environment. This intermediary structure enables precise radial measurement without requiring the entire screw nut to be overly complex.
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 configuration improves the accuracy of preload measurement by isolating the radial preload forces from axial motor thrust, enabling precise monitoring and reducing maintenance costs by preventing damage from installation errors and extending the service life of the ball screw.
Implementation Method 1
The elastic component includes a contact end and a fixed end, and at least one strain sensor is disposed on the elastic component
Implementation Method 2
at least one strain sensor is disposed on the elastic component
Data Source
AI summary
A ball screw with force sensor in radial direction including a screw rod, a screw nut, a plurality of balls, and a force sensor is provided. The screw nut has a cavity. The cavity is extended along a radial direction from an outer surface of the screw nut. The force sensor is disposed in the cavity of the screw nut, and the force sensor includes a stationary base and an elastic component. The stationary base includes a displacement restraint, and the elastic component includes a contact end and a fixed end. The displacement restraint is coupled to the cavity to prevent the stationary base from being displaced in the radial direction for fixing stationary base firmly in the cavity. The fixed end is connected to the stationary base, and the contact end contacts a bottom surface of the cavity in order to sense a force along the radial direction.