Rotor Angle Determination Using Self-Calibrating Sensor Offset Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional brushless direct current motors experience high power dissipation and noise due to angular errors in rotor position measurement, which are not effectively addressed by existing calibration methods that do not allow for calibration during operation.
Innovation Solution
A method and apparatus for continuously determining the rotation angle of a rotor using sensors, where signal values from angle sensors are measured during a full revolution, offset values are computed, and correction angles are calculated to normalize and standardize the signal values, enabling automatic calibration and compensation of interference fields during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional calibration methods using external Hall sensors are used, then initial rotor position measurement is possible, but calibration during operation is not permitted and mounting tolerances are restricted
Solution Approach 1:
The motor system performs self-calibration during operation by using its own coils and permanent magnets to generate the magnetic field needed for sensor calibration. The control unit automatically determines offset values and correction angles without external intervention, enabling the system to service itself and adapt to mounting tolerances and positional changes during operation.
Solution Approach 2:
The calibration process dynamically adjusts sensor parameters (offset values and correction angles) based on actual motor operation conditions. By measuring magnetic field values at different rotor positions during operation and computing corrected values, the system adapts to changes in mounting tolerances, sensor positions, and interference fields, transforming a static calibration process into a dynamic adaptive one.
2Reliability
If angular errors in rotor position measurement occur, then power dissipation increases and torque decreases, but continuous calibration during operation is not available in conventional systems
Solution Approach 1:
The system continuously monitors magnetic field values from the angle sensor during motor operation and feeds this information back to the control unit. The control unit computes offset values and correction angles based on this feedback, automatically adjusting the rotor position measurement to minimize angular errors and their harmful effects on power dissipation and torque.
Solution Approach 2:
The calibration process is not a one-time initial operation but continues throughout motor operation. The system continuously determines rotor position, measures magnetic field values, and updates correction parameters during operation, ensuring sustained measurement accuracy and preventing power loss from angular errors throughout the motor's operational life.
3Measurement precision
If static and dynamic interference fields are present, then measurement accuracy deteriorates, but automatic compensation during operation is not available
Solution Approach 1:
The system measures magnetic field values including the effects of interference fields during normal operation and uses these measurements to compute correction parameters. By incorporating the actual interference conditions into the calibration process, the system converts the harmful effect of interference fields into useful information for automatic compensation, maintaining measurement precision despite the presence of static and dynamic interference.
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 continuous calibration and compensation of static and dynamic interference, reducing power dissipation and noise, and enabling greater mounting tolerances and positional changes, thereby improving the accuracy and efficiency of motor control.
Implementation Method 1
A permanent magnet is mounted on an axle that is connected to the rotor. This permanent magnet generates the magnetic field used for capturing the rotor position.
Implementation Method 2
a correction angle is computed by using the ARCTAN value of the normalized/standardized reference values. The rotation angle is then determined by computing the ARCTAN value of the normalized/standardized amplitude values in the X direction and in the Y direction after deduction of the correction angle.
Data Source
AI summary
A method and an apparatus for determining a rotation angle of a rotor in a motor with the aid of angle sensors by measurement of reference values and correction of the effected computations. The method is used, for example, in a synchronous motor.