Sensorless Motor Control via Coil Inductance Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Sensorless brushless DC motors face challenges in detecting the rotor position at low speeds or when the induced voltage is absent, leading to high costs due to the requirement of a magnetometer and magnetization pattern in existing configurations.
Innovation Solution
A motor control apparatus that includes a supply unit for exciting coils, a detection unit to sense changes in inductance, and a control unit to determine and control the rotor position, eliminating the need for a magnetometer by utilizing changes in coil inductance to detect the rotor position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetometer and magnetization pattern are used to detect rotor position, then rotor position detection is enabled, but the cost increases
Solution Approach 1:
The patent extracts the rotor position detection function from the magnetometer-based system and implements it using the existing coil structure. By detecting changes in coil inductance caused by rotor position, the system eliminates the need for a magnetometer while maintaining detection capability.
Solution Approach 2:
The patent makes the existing coil structure serve a dual purpose: both for motor operation and for rotor position detection. The coil's own inductance changes provide the detection signal, eliminating the need for separate detection components.
2Measurement precision
If induced voltage is used to detect rotor position, then rotor position detection is enabled, but detection fails at low speeds or when the motor is not operating
Solution Approach 1:
The patent changes the detection parameter from induced voltage to coil inductance. Inductance is a property that changes with rotor position regardless of motor operation state, enabling detection across the full range of speeds including zero speed and standby conditions.
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 accurate rotor position detection at low speeds and when the motor is not operating, reducing costs by eliminating the need for a magnetometer and its associated components, while maintaining effective motor control.
Implementation Method 1
a first detection unit configured to detect a physical quantity which varies depending on a change in inductance of at least one of the plurality of coils
Data Source
AI summary
A motor control apparatus includes a supply unit to supply a current for excitation to a plurality of coils of a motor, a first detection unit to detect a physical quantity which varies depending on a change in inductance of at least one of the plurality of coils, and a determination unit to determine a rotational position of a rotor of the motor. A control unit controls the rotational position of the rotor of the motor based on a determination result by the determination unit, and a second detection unit detects an inducted voltage of each of the plurality of coils. The determination unit also determines the rotational position of the rotor based on the detected physical quantity when the rotor is at rest and when a rotational speed of the rotor is smaller than or equal to a predetermined value, and determines the rotational position of the rotor based on the detected induced voltage when the rotational speed of the rotor is greater than the predetermined value.