BLDC Sensorless Block Commutation for Accurate Runup Position Tracking
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Solution Overview
Problem
Existing sensorless commutation methods for brushless DC motors suffer from reduced accuracy in tracking rotor position due to the presence of both control and position detection current components during the runup phase, which affects the accuracy of rotor position tracking.
Innovation Solution
Utilizing changes in stator inductance, such as saturation and saliency effects, to detect rotor position through position detection signals during the runup phase, employing primary and secondary pulses with adjustable hysteresis and pause times, and transitioning to block commutation in the normal operation phase based on zero crossings of back-emf.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If both control current components and position detection current components are used during runup phase, then high runup torque is achieved, but rotor position tracking accuracy is reduced
Solution Approach 1:
The patent segments the current signal analysis into two distinct components: control current components and position detection current components. By separating these components through signal evaluation, the system can extract pure position detection information from the mixed current signal, thereby achieving accurate rotor position tracking while maintaining the high torque produced by control currents during the runup phase.
2Device complexity
If BEMF-based methods are used for sensorless motor regulation, then simple implementation is achieved, but tracking accuracy is limited below certain speeds
Solution Approach 1:
The patent changes the detection parameter from back-EMF (BEMF) to stator inductance variations. By monitoring changes in stator inductance caused by saturation effects and saliency effects at different rotor positions, the system achieves accurate position detection across a wider speed range, including low speeds where BEMF-based methods fail, while maintaining a relatively simple sensorless implementation.
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
Enhances rotor position tracking accuracy and robustness by using stator inductance properties to differentiate current responses, allowing precise rotor position detection and efficient commutation transition from runup to normal operation.
Implementation Method 1
changes in stator inductance can be used in the sensorless motor regulation in order to be able to detect and track the rotor position beneath the limit at which tracking is possible on the basis of BEMF-based methods. In this case, two basic physical properties of the motor can be used, namely saturation effects of the stator
Implementation Method 2
changes in stator inductance can be used in the sensorless motor regulation in order to be able to detect and track the rotor position beneath the limit at which tracking is possible on the basis of BEMF-based methods. In this case, two basic physical properties of the motor can be used, namely saturation effects of the stator and/or saliency effects.
Data Source
AI summary
Method for the sensorless block commutation of a brushless DC motor, wherein a current sensor for detecting a current flowing through the DC motor, a detection circuit for detecting the zero crossings of the back-emf and a control unit are used, wherein the control unit is suitable for providing block control signals and position detection signals for a motor inverter assigned to the DC motor on the basis of the detected current and/or the zero crossings of the back-emf, wherein the block control signals are used for generating a propulsion force in order to drive a rotor of the DC motor causing it to rotate, and the position detection signals are used for detecting a rotor position of the rotor, and wherein the DC motor goes through a plurality of rotor position sectors in a runup phase prior to a normal operation phase being reached, and the control unit outputs exclusively position detection signals to the motor inverter in the runup phase.