BLDC Saliency Tracking for Sensorless Low-Speed Rotor Position
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Solution Overview
Problem
Existing methods for estimating rotor position in brushless direct current (BLDC) motors and permanent magnet synchronous motors (PMSMs) are inadequate at low speeds and standstill, requiring external sensors that incur additional costs and are unreliable.
Innovation Solution
A saliency tracking algorithm that estimates rotor position by injecting a pulsating voltage into the motor, measuring current responses, and using a phase-locked loop to determine rotor position without external sensors, suitable for low-speed and standstill operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sensors (quadrature encoders or hall effect sensors) are used to obtain rotor position, then position accuracy at standstill and low speeds is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the position sensing function from external hardware sensors and implements it through software-based saliency tracking algorithms that process existing motor phase currents to estimate rotor position, eliminating the need for separate sensor components
Solution Approach 2:
The motor's existing electrical components (phase windings and current sensors) are made multi-functional by using them not only for torque production but also for position estimation through saliency tracking, eliminating the need for dedicated position sensors
2Reliability
If external sensors are used to obtain rotor position, then position information is available at standstill and low speeds, but reliability decreases due to additional failure points
Solution Approach 1:
The patent removes external position sensors from the system architecture, using only the motor's inherent electrical characteristics and existing current measurement circuitry to derive position information, thereby eliminating additional failure points
Solution Approach 2:
The motor system uses its own electrical characteristics (saliency effects) and existing current sensors to self-determine rotor position without requiring external sensing components, making the system self-sufficient and more reliable
3Reliability
If BEMF-based position estimation is used, then the method is robust and well developed, but position information is unavailable at standstill and performance is poor at low speeds
Solution Approach 1:
The patent employs periodic high-frequency voltage injection into the motor phases to excite saliency effects, allowing position estimation through the periodic current responses that occur regardless of rotor speed or stationary conditions
Solution Approach 2:
The patent changes the operating parameters by injecting high-frequency voltage signals superimposed on the fundamental drive waveforms, enabling position detection through frequency-domain analysis of current responses that works across the entire speed range including standstill
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
Enables accurate rotor position estimation and eliminates the need for external sensors, reducing costs and improving system performance in applications like micromobility and robotics.
Implementation Method 1
measuring a current responsive to the pulsating voltage
Implementation Method 2
an envelope detector configured to measure a current responsive to the injected pulsating voltage
Implementation Method 3
a phase-locked loop (PLL) configured to estimate a rotor position of the PMSM from an output of the envelope detector
Data Source
AI summary
Saliency tracking for brushless direct current (BLDC) motors and other permanent magnet synchronous motors (PMSMs) is provided. Embodiments generate an accurate estimate of rotor position for use in field-oriented control (FOC) of BLDC motors. In addition, a robust saliency tracking algorithm provides for the use of BLDC motors in low-speed high-torque applications without the need of external sensors. This enables sensorless application of higher level algorithms as well, such as servo control. In addition, accurate measurement of motor phase inductance and flux linkage can be provided without any additional equipment.