Vehicle Flap Movement Detection via Floating BLDC Phase Sensing
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Solution Overview
Problem
Existing methods for detecting manual opening or closing of electrically operated flaps in motor vehicles are inefficient and costly, with external sensors or switches increasing system complexity and speed-dependent voltage measurements failing to detect slow movements reliably.
Innovation Solution
A method using a BLDC motor with a three-phase stator, where two phases receive pulse-width modulated voltage and the third phase is floating, allowing the third phase to act as a measuring point for an inductive voltage divider, enabling reliable detection of manual flap movements by monitoring changes in rotor position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external sensors or switches are used to detect manual flap movement, then the detection reliability is improved, but the device complexity and cost increase
Solution Approach 1:
The patent applies multi-functionality by making the third phase of the BLDC motor serve dual purposes: it remains a functional phase for motor operation while simultaneously acting as a measuring point for detecting manual flap movements. This eliminates the need for separate sensors or switches, reducing system complexity while maintaining detection reliability.
2Device complexity
If back-induced voltage measurement is used to detect manual movement, then the device complexity is reduced, but the measurement precision deteriorates for slow movements
Solution Approach 1:
The patent replaces the back-induced voltage measurement method with an inductive voltage divider approach using the third phase. This substitution enables detection of slow manual movements by measuring voltage division ratios rather than relying on speed-dependent back-EMF, thereby improving measurement precision while keeping the system simple.
3Quantity of substance
If the third phase is held free-floating and used as a measuring point, then the component quantity is reduced, but the ease of manufacture may be affected
Solution Approach 1:
The third phase serves dual functionality as both a motor phase and a measuring point for the inductive voltage divider. This eliminates the need for additional components while the control unit handles the measurement and evaluation, maintaining manufacturing feasibility through software-based solutions rather than hardware modifications.
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 reduces system complexity and cost by utilizing existing motor components, providing reliable detection of manual movements independent of speed, and enabling precise determination of rotation angle and direction.
Implementation Method 1
the third phase is held free-floating, wherein the third phase is monitored as a measuring point for an inductive voltage divider formed with the two other phases
Implementation Method 2
When the position of the rotor's magnetic poles relative to the stator poles changes, the inductances of the voltage divider change, and this change can be measured at the floating phase
Data Source
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Figure 3~4
AI summary
A method for detecting the movement of a pivoting body part, in particular a flap, of a motor vehicle, wherein the motor vehicle comprises an electric motor with a stator and a rotor, wherein the electric motor is configured to electrically open or close the pivoting body part, wherein the electric motor is a BLDC motor with a three-phase stator (A, B, C), wherein two phases of the stator (A, B) are supplied with a pulse-width modulated voltage, wherein the third phase (C) is held free-floating, wherein the third phase (C) is monitored as a measuring point for an inductive voltage divider formed with the two other phases (A, B), wherein if the signal at the measuring point or a value derived from the signal exceeds a predetermined threshold, an opening or closing action is initiated.The closing movement of the pivoting body part is detected and a motor vehicle, wherein a control unit of the motor vehicle is equipped to carry out such a procedure.