Linear Actuator Magnetic Referencing for Accurate Position Sensing
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Solution Overview
Problem
Existing incremental position detection systems in linear actuators are prone to inaccuracies and unreliability due to mechanical wear and calibration issues, especially when the spindle nut reaches predetermined positions during its travel, and require expensive components and precise mechanical synchronization.
Innovation Solution
The use of magnetic sensors, either digital or analogue, positioned parallel to the spindle's axial direction, with a magnet attached to the spindle nut or activation element, allows for precise synchronization and calibration of the counter system, avoiding mechanical components and ensuring reliability by detecting the proximity of the magnet, thus providing accurate position detection without mechanical wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If incremental position detection systems (magnetic/optical encoders) are used to determine spindle position, then cost is reduced and reliability is improved, but position accuracy deteriorates when supply voltage is interrupted or mechanical adjustments occur
Solution Approach 1:
The patent replaces mechanical position reference systems (physical marks, mechanical switches) with a magnetic field-based reference system. A magnet is attached to the spindle nut, and magnetic sensors mounted on the spindle detect its position. This substitution eliminates mechanical wear and provides reliable position detection even after voltage interruptions, as the magnetic reference points remain intact and can be detected immediately upon system restart.
Solution Approach 2:
The magnetic reference system serves multiple functions: it provides absolute position reference, enables calibration, and allows detection of mechanical adjustments. The same magnet and sensor arrangement that detects normal operational position also serves as a reference for recalibration after voltage interruptions or manual adjustments, eliminating the need for separate reference mechanisms.
2Manufacturing precision
If mechanical reference systems or switches are used to mark predetermined positions, then position calibration is possible, but mechanical wear occurs and components become unreliable over time
Solution Approach 1:
The patent replaces mechanical reference markers and switches with magnetic sensors that detect the position of a magnet attached to the spindle nut. This eliminates all mechanical contact and wear at the reference detection points. The magnetic field interaction requires no physical contact, ensuring that reference components remain reliable indefinitely without degradation from friction or mechanical stress.
3Measurement precision
If potentiometers are used for position detection, then absolute position indication is obtained regardless of voltage interruptions, but cost increases and the components are prone to wear and failure
Solution Approach 1:
The patent replaces the potentiometer's mechanical sliding contact system with magnetic sensors that detect the position of a magnet on the spindle nut. This eliminates the wear-prone sliding contacts while maintaining absolute position indication capability. The magnetic reference points provide a non-contact method of determining position that is equally accurate but free from the wear and failure modes of potentiometers.
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 solution enhances the accuracy and reliability of position detection in linear actuators by eliminating mechanical limitations, maintaining precision over time, and preventing signal loss, even when the system is subjected to mechanical vibrations or manual adjustments, while being cost-effective and resistant to contamination.
Implementation Method 1
A first magnetic sensor (13) and a second magnetic sensor (14) mounted on a print circuit board (11) located in the housing (10), separated from the mechanical parts of the actuator by means of a side wall
Data Source
AI summary
Linear electric actuator (1) comprising a housing (10) with a reversible DC-motor (2), which through a transmission (3) can move an activation element (6) between two end positions, where an incremental position detection system is adapted to indicate the position of the spindle nut (5) during its travel on the spindle (4) and where the accuracy of the position detection system continuously is calibrated in that a magnet (15) is arranged in connection with the spindle nut (5), and at least one magnetic sensor (13,14) is arranged within the housing (10) of the actuator in a position where a proximity with the magnet (15) arranged in connection with the spindle nut (5) on its travel on the spindle (4) is achieved to establish a reference point for the position detection system.