Furniture Drive Back-EMF Monitoring for Sensorless Position Control
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Solution Overview
Problem
Existing electric furniture drives, particularly those using Hall sensors, are complex, expensive, and difficult to retrofit, with limited reliability and high error rates in positioning due to the need for precise direction detection and synchronization of multiple motors.
Innovation Solution
An electromotive furniture drive system incorporating a digital potentiometer for memory control and synchronous control, with a monitoring device that evaluates the pulse width ratio of the back EMF of the electric motor to enhance reliability and reduce error rates, using a filter unit, pulse shaper, comparator, and signal generator to detect and respond to changes in load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall sensors are used for direction detection and positioning, then positioning accuracy is improved, but device complexity and installation difficulty increase
Solution Approach 1:
The patent extracts the direction detection function from complex Hall sensor systems and implements it using the back EMF of the motor itself. The back EMF naturally provides directional information through its polarity changes, eliminating the need for separate Hall sensors and their associated magnets, circuit boards, and wiring.
Solution Approach 2:
The motor's own back EMF is used for direction detection and positioning. The system serves itself by utilizing the motor's inherent electrical characteristics rather than requiring external sensing components. This self-service approach simplifies the overall system while maintaining positioning accuracy.
2Reliability
If multiple Hall sensors are used for reliable direction detection, then positioning reliability is improved, but device complexity and installation difficulty increase
Solution Approach 1:
The patent removes the need for multiple Hall sensors by using the back EMF of the motor for direction detection. The back EMF inherently provides reliable directional information through its polarity changes during motor rotation, eliminating the complexity of installing and wiring multiple sensors.
Solution Approach 2:
The back EMF serves multiple functions simultaneously: it provides direction detection, positioning information, and motor status monitoring. This multi-functionality replaces what would otherwise require multiple separate components, simplifying the system while maintaining reliability.
3Ease of manufacture
If standard motor cables are used without additional wiring, then ease of installation and retrofitting is improved, but measurement precision for direction detection deteriorates
Solution Approach 1:
The motor's back EMF is utilized for direction detection using only the existing motor cables. The system extracts directional information from the motor's own electrical characteristics without requiring additional sensors or specialized wiring, enabling easy installation and retrofitting while maintaining measurement precision.
Solution Approach 2:
The patent changes the approach from using external sensor signals to using the motor's back EMF parameters. By monitoring the polarity and characteristics of the back EMF voltage, the system achieves accurate direction detection using standard motor cables, eliminating the need for specialized wiring or additional components.
4Adaptability or versatility
If existing furniture without memory control is retrofitted, then adaptability is improved, but device complexity and installation effort increase
Solution Approach 1:
The patent extracts the memory control functionality and integrates it into the existing motor control system using the back EMF. This approach allows retrofitting of existing furniture without requiring separate Hall sensor systems or complex additional components, simplifying the installation process while adding memory control capability.
Solution Approach 2:
The back EMF monitoring system serves multiple purposes: it enables direction detection, positioning, and memory control functionality. This multi-functional approach allows existing furniture to be retrofitted with advanced features without requiring multiple separate systems, reducing installation complexity while improving adaptability.
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
The system provides reliable and accurate positioning with reduced error rates and simplified retrofitting, using standard components and minimizing the need for complex Hall sensors, while maintaining high-quality positioning accuracy.
Implementation Method 1
a positioning device for the output element with a control block with a counter and a storage device for evaluating pulses of a back EMF of the at least one electric motor
Data Source
Figure 1
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Figure 3
AI summary
The invention relates to an electromotive furniture drive (100) for adjusting a moveable part (4, 5) of a piece of furniture (1) by means of an output element, comprising a) at least one adjusting drive (7, 8) with respectively at least one electric motor, a speed reducing mechanism which is coupled thereto and which ensures that the output element is drivenly coupled and can be linearly displaced and/or rotatably moved, and when said output element reaches a predetermined position, said output element actuates an end switch and/or reference switch and/or switching means, b) at least one control device (9) and c) at least one control unit (10), said control device (9) comprising a positioning device for the output element provided with a control block with a counter and a recording device for evaluating impulses of a counter EMK of the at least one electric motor. Said control device (9) comprises a digital potentiometer which emits as an output value, an electric value which is proportionate to the position of said output element. The control device comprises, in a further embodiment, a monitoring device. The invention also relates to a method for monitoring a pulse width ratio of an electromotive furniture drive and a piece of furniture (1).