Motor Controller Rotor Position Detection Using Transient Current
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Solution Overview
Problem
Conventional methods for determining the starting position of a brushless DC motor are inefficient and time-consuming, often requiring external sensors that increase parts count and circuit complexity, making them cumbersome and wasteful of time and energy.
Innovation Solution
A motor controller that measures transient current responses in the motor windings using integrated and digital signal processing techniques, such as analog-to-digital conversion and sigma-delta weighting, to accurately determine the rotor position without external sensors, reducing noise interference and improving processing speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sensors (hall sensors or optical sensors) are used to detect rotor position, then measurement precision of rotor position is improved, but device complexity and parts count increase
Solution Approach 1:
The patent extracts the position detection function from external sensors and implements it within the motor controller itself. The controller determines rotor position by analyzing current waveforms and inductance characteristics during startup, eliminating the need for separate hall sensors or optical sensors and their associated circuitry.
Solution Approach 2:
The motor controller performs multiple functions: it controls motor operation and simultaneously determines rotor position during startup by analyzing current characteristics. This multi-functionality eliminates the need for dedicated external position sensors, reducing parts count while maintaining position detection capability.
2Reliability
If conventional startup methods are used to determine rotor position, then reliability of position detection is improved, but loss of time during startup increases
Solution Approach 1:
The patent performs preliminary rotor position determination during the startup sequence by analyzing current waveforms and inductance characteristics. This preliminary action enables the controller to identify the rotor's starting position quickly and accurately, allowing immediate transition to proper commutation without time-consuming external sensor measurements.
Solution Approach 2:
The patent changes the approach from using external sensor signals to analyzing electrical parameters (current waveforms, inductance characteristics) already present in the motor system during startup. This parameter change enables faster position detection while maintaining reliability through electrical characteristic analysis.
3Measurement precision
If external sensors and extra circuitry are added to detect rotor position, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The motor controller uses the motor's own current waveforms and electrical characteristics during startup to determine rotor position, without requiring additional external sensors or circuitry. This self-service approach eliminates the energy consumption associated with external position sensing systems while maintaining accurate position detection.
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 faster and more efficient startup of the motor by accurately determining the rotor position within 60 degrees, reducing noise influence and energy consumption, and enabling quicker transition to operational speeds.
Implementation Method 1
A motor controller measures transient current responses in the motor windings to accurately determine the rotor position
Implementation Method 2
The rotor is permanently magnetized, and turns to align its own magnetic flux with the flux generated by the windings when current flows through the windings
Data Source
AI summary
A system and method for determining the start position of a motor. According to an embodiment, a voltage pulse signal may be generated across a pair of windings in a motor. A current response signal will be generated and based upon the position of the motor, the response signal will be greater in one pulse signal polarity as opposed to an opposite pulse signal polarity. The response signal may be compared for s specific duration of time or until a specific integration threshold has been reached. Further, the response signal may be converted into a digital signal such that a sigma-delta circuit may smooth out glitches more easily. In this manner, the position of the motor may be determined to within 60 electrical degrees during a startup.