BLDC Motor Position Detection Using Complementary Driving Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional BLDC motor control techniques face challenges in accurately detecting motor position at zero speed due to the unavailability of BEMF information and noise issues in existing Initial Position Detect (IPD) methods, leading to potential reverse rotation and increased startup time.
Innovation Solution
The implementation of complementary driving and detect (CDD) signals, specifically using high-frequency signals to determine motor position by detecting inductance differences and inductor saturation, allowing for precise alignment of the rotor magnetic poles within a narrower sector range, reducing noise and startup time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional IPD techniques are used to detect motor position at startup, then motor position can be determined, but acoustic noise and vibration increase due to torque generated during current injection
Solution Approach 1:
The patent converts the harmful torque effect into a useful measurement signal. By measuring the voltage on the floating phase during complementary driving, the inductance difference caused by rotor position is detected without generating significant torque. The harmful torque that would normally result from direct current injection is transformed into a non-intrusive voltage measurement that still provides position information.
Solution Approach 2:
The patent replaces the mechanical torque-based detection method with an electrical voltage measurement method. Instead of relying on mechanical torque effects to indicate rotor position, the system uses voltage measurements on the floating phase to detect inductance differences, thereby eliminating the acoustic noise and vibration associated with mechanical torque generation.
2Measurement precision
If conventional IPD techniques are used to detect motor position at startup, then motor position can be determined, but detection accuracy is poor because six relatively close signals are compared
Solution Approach 1:
The patent extracts only the necessary position information from the phase voltages by focusing on the floating phase voltage during complementary driving. Instead of comparing six different current injection signals, the system extracts position information from a single voltage measurement, simplifying the detection process while maintaining or improving accuracy.
Solution Approach 2:
The patent changes the detection parameter from comparing multiple current signals to measuring voltage on the floating phase. This parameter change transforms a complex six-signal comparison problem into a simpler voltage measurement task, improving both accuracy and reducing computational complexity.
3Measurement precision
If BEMF information is used for position estimation, then position can be estimated during motor operation, but position cannot be determined at zero speed
Solution Approach 1:
The patent performs preliminary position detection using complementary driving and floating phase voltage measurement before the motor starts rotating. This preliminary action determines the initial rotor position at zero speed, enabling subsequent BEMF-based control to function properly once the motor begins moving.
Solution Approach 2:
The patent inverts the conventional approach by not relying on BEMF (which requires motion) but instead using the floating phase voltage during complementary driving to detect position. This inverted method works at zero speed where BEMF is unavailable, extending the detection capability to standstill conditions.
4Reliability
If open loop startup without position estimation is used, then reverse rotation is avoided, but startup time increases with conservative profiles or reliability decreases with aggressive profiles
Solution Approach 1:
The patent performs preliminary position detection using complementary driving before initiating the startup sequence. By knowing the initial rotor position in advance, the motor can immediately apply the correct phase voltages for forward rotation, eliminating the need for conservative alignment delays and enabling reliable and fast startup.
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
CDD techniques provide accurate motor position detection at zero torque with reduced acoustic noise and vibration, achieving faster startup and higher position resolution compared to conventional methods, with the ability to determine rotor position within 30 degrees instead of 60 degrees.
Implementation Method 1
An inductance difference is detected based upon the motor position after which inductor saturation is detected from magnet polarity
Implementation Method 2
An inductance difference is detected based upon the motor position after which inductor saturation is detected from magnet polarity
Data Source
AI summary
Methods and apparatus for determining a position of a rotor in motor, such as a three-phase motor by determining first and second ones of sectors in which a first one of the magnetic poles of the rotor may be positioned by driving phase pairs with complementary signals and examining a voltage of a floating one of the phases. Embodiments can further include driving first and second currents towards the first and second ones of the sectors and analyzing a time for each of the first and second currents to reach a threshold to identify which of the first and second ones of the sectors is aligned with the first one of the magnetic poles of the rotor.