Sensorless Motor Initial Position Estimation via Multi-Angle Inductive Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensorless-type brushless DC motors face challenges in accurately estimating the initial position of the magnetic pole of the rotor, particularly at low voltages and short voltage application times, due to motor structure dependencies and the risk of rotor movement during estimation, which can lead to detection errors and start-up failures, especially in inner rotor-type motors with low inertia.
Innovation Solution
A motor control device that applies voltage to the stator winding at multiple energization angles with controlled voltage and time, converts peak currents into components with specific electrical angles, calculates integrated values using cosine and sine corrections, and estimates the magnetic pole position based on the ratio of these values to ensure accurate initial position detection without rotor rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage is applied to the stator winding at high levels and for long durations to achieve magnetic saturation for accurate position estimation, then measurement precision of magnetic pole position is improved, but the rotor may rotate during estimation which causes detection errors and start-up failures
Solution Approach 1:
The patent changes the parameters of voltage application by applying voltage at multiple different energization angles (phases) rather than at a single angle. By varying the energization angle parameter and measuring current responses at each angle, the system can accurately estimate magnetic pole position through comparative analysis without needing to apply high voltage for long durations that would cause rotor rotation.
2Measurement precision
If the rotor is pulled to estimate initial position, then measurement precision of magnetic pole position is improved, but the rotor vibration increases and paper feeding jamming occurs
Solution Approach 1:
The patent replaces the mechanical pulling method with an electrical measurement method. Instead of mechanically moving the rotor to estimate position, the system applies electrical voltage at multiple energization angles and measures the resulting current responses. This electrical substitution eliminates mechanical vibration and paper feeding jamming while achieving accurate magnetic pole position estimation through inductive sensing.
3Reliability
If voltage application time is shortened to prevent rotor rotation, then reliability of start-up is improved, but measurement precision of magnetic pole position deteriorates
Solution Approach 1:
The patent employs periodic action by applying voltage at multiple discrete energization angles in sequence. Instead of applying voltage continuously for a long duration, the system periodically applies voltage at different angles (e.g., 0°, 60°, 120°, etc.) and measures current responses at each angle. This periodic measurement approach achieves accurate position estimation through comparative analysis while keeping each voltage application brief to prevent rotor rotation.
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 method allows for accurate estimation of the magnetic pole position even at low voltages and short times, reducing detection errors and enabling reliable start-ups, while minimizing the risk of rotor movement, thus improving the reliability of sensorless-type motor control.
Implementation Method 1
A sensorless-type brushless DC motor does not include a sensor for detecting a magnetic pole position of a permanent magnet of a rotor with respect to each phase coil of a stator. Thus, in general, before starting the motor, a stator is energized at a prescribed electrical angle so as to pull the magnetic pole of the rotor
Implementation Method 2
When a stator current is caused to flow in a d-axis direction corresponding to the direction of the magnetic pole of the rotor, a magnetic flux by a permanent magnet of the rotor and a magnetic flux by the current are added. Thereby, a magnetic saturation occurs to reduce the inductance
Data Source
AI summary
In a motor control device in one embodiment, an initial position estimation unit estimates an initial position of a magnetic pole of a rotor of a motor in an inductive sensing scheme. At each of energization angles, the initial position estimation unit multiplies a γ-axis current component Iγ corresponding to a peak value of a current flowing through a stator winding by each of a cosine value and a sine value of a correction angle obtained by correcting each of the energization angles. The initial position estimation unit estimates the initial position of the magnetic pole of the rotor based on a ratio between an integrated value of a multiplication result about the cosine value and an integrated value of a multiplication result about the sine value.