Sensorless Motor Startup With Observer-Based Acoustic Noise Reduction
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Solution Overview
Problem
Conventional BLDC motor control techniques face challenges in minimizing acoustic noise during startup, particularly in sensorless systems, which can cause reverse rotation, increased startup time, or unreliable operation due to high current ripple.
Innovation Solution
A motor control system with a controller that includes a d-axis and q-axis control loop, an observer for speed and angle estimation, and a startup module that adjusts the q-axis voltage based on an observer error to smoothly transition from open-loop to closed-loop operation, minimizing acoustic noise without extending the startup interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional open-loop startup control is used in sensorless systems, then the motor can be started without sensors, but reverse rotation occurs and startup reliability decreases
Solution Approach 1:
The patent implements a feedback mechanism by monitoring the actual motor current and comparing it with the applied starting current. This feedback allows the system to detect misalignment between stator and rotor magnetic fields and adjust the starting current phase accordingly, preventing reverse rotation and improving startup reliability in sensorless systems.
Solution Approach 2:
The patent replaces mechanical sensor-based position detection with an electrical feedback system that uses current sensing and phase angle calculation. Instead of using physical sensors to detect rotor position, the system uses electrical measurements and mathematical computations to achieve the same control objective.
2Reliability
If high startup current is applied to overcome static friction, then the motor can start reliably, but current ripple increases causing acoustic noise
Solution Approach 1:
The patent applies dynamic adjustment of the starting current magnitude and phase angle during the startup process. Rather than using a fixed high current, the system continuously adapts the current parameters based on real-time feedback from motor current sensing, allowing reliable startup while minimizing current ripple and acoustic noise.
Solution Approach 2:
The patent changes the parameters of the starting current (magnitude, phase angle, frequency) dynamically during the startup interval. By adjusting these parameters based on feedback, the system achieves reliable motor startup while minimizing harmful current ripple that causes acoustic noise.
3Productivity
If conventional startup techniques are used, then the motor can be started, but transition to closed-loop operation causes high current ripple and acoustic noise
Solution Approach 1:
The patent performs preliminary alignment of the starting current phase with the actual motor current phase before transitioning to closed-loop operation. This preliminary action ensures that the magnetic fields are properly aligned, preventing high current ripple and acoustic noise during the transition from open-loop to closed-loop control.
Solution Approach 2:
The patent uses feedback from actual motor current measurements to adjust the starting current phase angle before and during the transition to closed-loop operation. This feedback mechanism ensures smooth transition without high current ripple or acoustic noise by maintaining proper magnetic field alignment throughout the transition process.
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
The system optimally transitions from open-loop to closed-loop operation, reducing acoustic noise and ensuring reliable motor startup without increasing the startup duration, suitable for sensorless control in electric vehicles.
Implementation Method 1
a motor control system for controlling operation of a motor having a plurality of windings
Implementation Method 2
BEMF (back emf) information for position estimation, however, BEMF information is not available at zero speed
Data Source
AI summary
Methods and apparatus for motor startup with reduced acoustic noise include a startup module to generate a startup d-axis voltage during a startup interval and a startup q-axis voltage during the startup interval, wherein the startup interval ends at a time based on the observer error, and wherein the startup q-axis voltage increases during the startup interval. The startup module is configured to continuously linearly increase the speed of the motor during the startup interval. An observer generates a speed estimate, an angle estimate, and an observer error representative of a difference between an actual angle and the angle estimate. A voltage increment by which the startup q-axis voltage is increased during the startup interval is adjusted based on the observer error. The voltage increment can be equal to a constant value plus the observer error.