Electric Motor Positioning Using Back-EMF Pulse Correction
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Solution Overview
Problem
Existing methods for positioning electromotive drives in furniture, such as potentiometers, Hall sensors, and rotary encoders, are expensive and not suitable for the low-price furniture market, and counter-EMF evaluations are limited in end positions where the motor is switched off.
Innovation Solution
A method that corrects counter values obtained from processed pulses using a correction value, determined by filtering, averaging, and comparing counter-EMF pulses, and utilizing limit switches and motor control means to minimize errors, allowing for precise positioning without additional measuring devices, and enabling memory functions and optical displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If potentiometers are used for position detection, then position information can be obtained, but the cost increases and mechanical complexity increases
Solution Approach 1:
The patent replaces mechanical position detection devices (potentiometers, Hall sensors, rotary encoders) with an electrical measurement approach. It uses the counter-EMF signal already present in the motor's armature current to detect position, eliminating the need for separate mechanical sensing components. This substitution reduces both cost and mechanical complexity while maintaining position detection capability.
2Measurement precision
If Hall sensors are used for position detection, then position accuracy is improved, but the cost increases
Solution Approach 1:
The patent makes the motor's own counter-EMF signal serve the dual purpose of both driving the motor and providing position detection information. By evaluating the pulses already present in the armature current, the system achieves position accuracy without requiring additional expensive sensors like Hall sensors, thus reducing cost while maintaining measurement precision.
3Measurement precision
If rotary encoders with light barriers are used, then position measurement precision is improved, but space consumption increases and cost increases
Solution Approach 1:
The patent extracts the position detection function from separate physical components (rotary encoders with light barriers) and integrates it into the existing motor control circuitry. By using the counter-EMF pulses already generated by the motor, the system achieves position measurement precision without requiring additional space-consuming optical components, thus reducing space consumption while maintaining measurement precision.
4Measurement precision
If counter-EMF pulses are used for position detection when motor is switched off, then position information can be obtained, but pulse measurement becomes impossible
Solution Approach 1:
The patent performs position detection using counter-EMF pulses before the motor is switched off for extended periods. By continuously monitoring and evaluating pulses while the motor is still running, the system captures position information in advance, ensuring accurate position data is available even when the motor stops and pulse generation ceases.
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 cost-effective positioning of electromotive drives, enabling precise adjustment and memory functions, even with motors having large manufacturing tolerances, and eliminates the need for expensive sensors, making it suitable for the low-price furniture market.
Implementation Method 1
pulses from the counter-EMF of a motor of the electromotive drive are processed by filtering, averaging and comparison, with interference being minimized
Data Source
AI summary
A method for positioning an electromotive drive (1), in particular for a piece of furniture, has the following method steps: determining a last stored position of the electromotive drive (1) by reading out a counter value and recognizing a desired adjustment direction; Adjusting the counter value by adding or subtracting pulses that are processed from the back EMF of the electromotive drive (1); determining a correction value when stopping the electric motor drive (1) based on boundary conditions; and correcting the last counter value obtained using the determined correction value and storing the counter value corrected in this way as the current position of the electric motor drive (1). A device (10) for carrying out the method and an electric motor drive (1) are provided.