Sensorless Brushless DC Motor Rotor Positioning via Voltage Gradient
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional sensorless brushless direct current motors struggle to accurately determine the rotor position at rest or low speeds, limiting efficient startup and operation.
Innovation Solution
A method involving measurement voltage signals applied between two terminals of a three-phase motor, with the resulting voltage's gradient used to determine the rotor position, considering the variation in inductance due to the magnetic field and current flux, allowing for precise angular positioning even at low speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless commutation is used to eliminate sensors, then device complexity is reduced, but measurement precision of rotor position deteriorates at low speeds and rest
Solution Approach 1:
The patent applies parameter changes by utilizing the frequency characteristic of the current signal. Specifically, it separates the current signal into different frequency components: a first frequency component corresponding to the rotation frequency of the rotor and a second frequency component corresponding to the rotation frequency multiplied by the number of pole pairs. By analyzing the phase difference between these frequency components, the system can determine rotor position accurately even at low speeds without requiring additional sensors.
Solution Approach 2:
The patent transitions from spatial measurement (physical sensor placement) to frequency-domain measurement. Instead of using physical sensors to directly detect rotor position in space, the system transforms the problem into the frequency domain by analyzing the spectral characteristics of the current signal. This dimensional transformation enables position detection without physical contact or additional hardware.
2Ease of operation
If counter-e.m.f. evaluation is used for rotor position detection, then ease of operation is improved, but measurement precision deteriorates below minimum rotor speed
Solution Approach 1:
The patent applies preliminary action by injecting a test voltage signal into the armature winding before normal operation begins. This test signal excites the magnetic circuit and generates a measurable current response that reveals rotor position information. By performing this preliminary excitation, the system obtains position data without relying on counter-e.m.f., which requires the rotor to be already rotating at sufficient speed.
Solution Approach 2:
The patent introduces an intermediary test voltage signal as a mediator between the control system and the rotor position. Instead of directly measuring counter-e.m.f. during rotation, the system uses this intermediate test signal to indirectly probe the rotor position through the magnetic coupling between stator and rotor. The current response to the test signal serves as an intermediary carrier of position information.
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
Enables reliable and efficient determination of the rotor position from rest to average speeds, improving startup reliability and operational efficiency by accurately accounting for inductance changes and induced electromotive forces.
Implementation Method 1
a measurement voltage signal is applied between a first and second of the terminals, a resulting voltage is measured on a third of the terminals
Implementation Method 2
detection of the rotor position is achieved by means of the negative field voltage, which is induced in the armature coils of the stator
Implementation Method 3
a gradient value which indicates the gradient of the resulting voltage in a time interval is determined with reference to the progression over time of the resulting voltage
Data Source
AI summary
A method for operating a brushless direct current motor wherein, by the energization of a plurality of armature coils which are arranged on a stator and form a three-phase current winding for generating a rotating field which rotates around the stator, and having three terminals, a rotating field is generated in order to drive a rotor, which is rotatable about an axis of rotation relative to the stator and has at least two opposing permanent magnet poles. For the determination of the position of the rotor relative to the stator a measurement voltage signal is applied between a first and second of the terminals, a resulting voltage is measured on a third of the terminals, a gradient value which indicates the gradient of the resulting voltage in a time interval is determined with reference to the progression over time of the resulting voltage.