Vehicle Flap Movement Detection via BLDC Phase Inductance
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Solution Overview
Problem
Existing methods for detecting the manual movement of pivotable vehicle body components, such as flaps, are inefficient and costly due to the use of external sensors or switches, and speed-dependent back-induced voltage measurements are unreliable for slow movements.
Innovation Solution
A method using a brushless DC (BLDC) motor with a three-phase stator, where two phases are pulse-width-modulated and the third phase is free-floating, allowing the detection of manual movements by monitoring changes in the inductive voltage divider formed by the phases, enabling reliable and cost-effective detection of opening and closing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external sensors or switches are used to detect manual movement, then detection reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies multi-functionality by making the existing motor phases serve dual purposes: both actuation and sensing. The three-phase motor's phases are used not only to drive the flap but also to detect manual movements through inductance changes, eliminating the need for separate sensors or switches while maintaining reliable detection capability
Solution Approach 2:
The system applies self-service by enabling the motor itself to perform the detection function that would otherwise require external components. The motor's own electrical characteristics (inductance variations in its phases) are exploited to sense manual movements, making the system self-diagnostic and reducing component count
2Device complexity
If back-induced voltage measurement is used to detect manual movement, then detection can be implemented without additional components, but detection reliability deteriorates for slow movements
Solution Approach 1:
The patent changes the measurement parameter from back-induced voltage (which is speed-dependent) to phase inductance (which is position-dependent and speed-independent). By monitoring inductance variations in the motor phases caused by rotor position changes during manual movement, the system achieves reliable detection regardless of movement speed
Solution Approach 2:
The patent replaces the voltage-based detection method with an inductance-based method. Instead of measuring electrical voltage generated by motor motion, the system measures the magnetic circuit's inductance properties that change with rotor position, providing a more reliable sensing mechanism for slow movements
3Speed
If inductance measurement is used to detect rotor position, then speed-independent detection is achieved, but measurement precision requirements increase
Solution Approach 1:
The system implements feedback by continuously monitoring the inductance of motor phases and using this information to determine rotor position and detect manual movements. The control unit processes the inductance measurements and provides feedback signals to trigger appropriate responses, enabling reliable detection without requiring extremely high measurement precision
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 allows for reliable and cost-effective detection of manual movements of pivotable vehicle body components without additional components, being speed-independent and accurately determining the direction and extent of the movement.
Implementation Method 1
the electric motor comprises a brushless DC (BLDC) motor having a three-phase stator, having two phases thereof that are loaded with a pulse-width-modulated voltage and a third phase that is kept free-floating. The third phase is monitored as a measuring point for an inductive voltage divider which is formed using the two other phases.
Data Source
AI summary
A method for detecting movement of a vehicle body component moveable by an electric motor having a rotor and a three-phase stator, and a motor vehicle. The method includes: loading two stator phases with a pulse-width-modulated voltage and maintaining a third stator phase at a free-floating state; monitoring the third stator phase as a measuring point for an inductive voltage divider formed using the two stator phases; and detecting movement of the vehicle body component when an electric signal at a measuring point or a variable derived from the electric signal exceeds a specified threshold value. The motor vehicle includes a control device that is operable to perform the method.