Linear Actuator Absolute Positioning with Hall Sensors
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Solution Overview
Problem
Existing linear actuators face challenges in achieving accurate absolute positioning due to limitations in mechanical position detection methods, such as Reed-switches and potentiometers, which suffer from mechanical wear, reliability issues, and high costs, leading to inaccuracies and the need for extensive testing and calibration.
Innovation Solution
The use of incremental position sensors like Hall sensors or Reed switches, combined with a microprocessor and battery backup, allows for absolute position determination by registering signals during motor operation and converting them into a proportional output voltage, mimicking the functionality of a potentiometer without its drawbacks, using a D/A converter and low-pass filtering to achieve accurate position measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Reed-switches or potentiometers are used for position detection, then position measurement can be achieved, but mechanical wear and reliability issues occur
Solution Approach 1:
The patent replaces mechanical position detection components (Reed-switches, potentiometers) with a magnetic encoder system consisting of a magnetic frame yoke with poles and non-contact sensors (Hall sensors or Reed switches). This substitution eliminates mechanical wear by using magnetic field interaction instead of physical contact, thereby improving reliability while maintaining measurement precision.
2Measurement precision
If mechanical end stops are used to reset the counting cycle, then position accuracy can be maintained, but the system requires manual intervention and calibration
Solution Approach 1:
The patent implements a self-calibrating system where the control unit automatically detects the magnetic pole positions and establishes the counting cycle reference points without manual intervention. The system performs automatic calibration by detecting when magnetic poles pass the sensors, eliminating the need for manual reset operations while maintaining position accuracy throughout the actuator's range of motion.
3Ease of manufacture
If incremental position sensors are used instead of absolute sensors, then system cost is reduced, but position determination requires continuous counting which can accumulate errors
Solution Approach 1:
The patent employs feedback mechanisms where the control unit continuously monitors the positions of magnetic poles relative to the sensors and adjusts the counting cycle accordingly. By detecting the passage of magnetic poles and using this feedback to reset and recalibrate the counting cycle, the system prevents error accumulation and maintains accurate position determination throughout operation, achieving absolute positioning accuracy through incremental sensing with feedback-based correction.
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 provides accurate and reliable absolute positioning with reduced mechanical wear, lower costs, and simplified recalibration, ensuring position accuracy even during power interruptions and manual adjustments, offering a more robust and cost-effective alternative to traditional potentiometers.
Implementation Method 1
a magnetic encoder comprises a magnetic frame yoke with a number of poles, which activate a Reed-switch or a Hall-sensor every time one of the poles passes by the switch, alternatively the Hall-sensor, at which an electric signal is discharged
Implementation Method 2
a magnetic frame yoke with a number of poles
Data Source
AI summary
A linear actuator includes a spindle nut, where the spindle nut and the spindle between a first and a second point, indicating the length of stroke, can move axially in proportion to each other, depending on whether the spindle or the spindle nut is being driven around via the transmission, and where the position is determined with incremental position sensors, such as at least two Hall sensors or Reed-switches. For determining the position an initiating procedure, where the nut/spindle is moved from a first point on the spindle/nut to a second point on the spindle nut is carried out, and that the number of pulses from the incremental position sensors appearing by it are registered as a measurement for the length of stroke, and the position is subsequently determined in relation to that. It is noted that the control is active before, during and after the operation of the motor. Hereby, absolute position detection is achieved with incremental sensors, where one formerly was obliged to use rotary potentiometers. Simultaneously an optional determination of the length of stroke and its position and immediate possibility to change the same at any time is achieved.