Furniture Drive Motor Overload Detection Using Back-EMF Frequency
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Solution Overview
Problem
Existing electromotive furniture drives face challenges in detecting overload or imminent danger situations, such as entrapment, which require complex and resource-intensive additional sensor setups to reliably assess motor current changes or vibrations.
Innovation Solution
The control unit evaluates the frequency of the back EMF signal generated by the brushed DC motor to detect changes in rotational speed, allowing for the detection of collisions or pinching events without additional sensors, simplifying assembly and using standardized motors with a two-wire cable setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional sensors (current sensors, vibration sensors, piezo sensors) are used to detect overload or entrapment situations, then detection reliability is improved, but device complexity and assembly effort increase
Solution Approach 1:
The motor serves itself by generating the back EMF signal that contains information about its operational state. The control unit extracts speed information directly from the motor's own electrical characteristics without requiring external sensors, making the system self-diagnosing and eliminating additional detection components
Solution Approach 2:
The existing motor is made multi-functional by utilizing its back EMF signal not only for speed control but also for safety monitoring and overload detection. This transforms a single component into a multi-purpose element that performs both actuation and sensing functions
2Measurement precision
If additional sensors and circuit boards are installed to monitor motor current and vibrations, then detection precision is improved, but manufacturing cost and assembly effort increase
Solution Approach 1:
The motor provides its own measurement signal through its back EMF, eliminating the need for separate measurement devices. The control unit processes this self-generated signal to detect operational anomalies, reducing manufacturing complexity while maintaining detection precision
Solution Approach 2:
The control unit combines the motor control function with the safety monitoring function into a single integrated system. The same control unit that regulates motor operation also analyzes the back EMF signal for overload and entrapment detection, merging multiple functions into one component
3Device complexity
If motor current evaluation is used to detect overload situations, then device complexity is reduced, but detection reliability deteriorates
Solution Approach 1:
The patent replaces direct mechanical or electrical current monitoring with an electromagnetic field-based measurement. By evaluating the back EMF signal frequency rather than current magnitude, the system achieves more reliable speed-dependent overload detection without additional hardware complexity
Solution Approach 2:
The detection parameter is changed from motor current magnitude to back EMF signal frequency. This parameter transformation provides more reliable speed information for overload detection, as the frequency directly correlates with motor speed and load conditions without being affected by electrical noise or current measurement errors
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 approach provides reliable detection of motor speed changes, enabling efficient switching off or reversing of the motor to prevent damage, while reducing assembly complexity and material usage by leveraging existing motor connections.
Implementation Method 1
the motor of the adjustment drive is designed as a DC motor with brushes, it generates a back EMF (electromotive force) signal from which its rotational speed can be derived
Data Source
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AI summary
The invention relates to an electric motor-powered furniture drive comprising: at least one motor-powered adjustment drive for the motor-powered adjustment of at least one furniture component; at least one control unit (10) which is connected to a motor control system (30) of the at least one adjustment drive; and at least one operating unit (20) for operating the at least one adjustment drive. The control unit (10) is designed to drive, to stop and/or to temporarily reverse at least one motor (40) of the at least one adjustment drive by means of the motor control system (30) depending on the operating situation of the electric motor-powered furniture drive, and the at least one motor (40) is designed as a brushed DC motor. The electric motor-powered furniture drive is characterised in that the control unit (10) is designed to evaluate a frequency of a counter-EMF signal generated by the at least one motor (40) and to detect and signal a collision and/or a jamming incident in accordance with the evaluated signal.