Sensorless Electric Motor Control via Current Harmonic Analysis
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Solution Overview
Problem
Traditional electric motor control systems in alternative fuel vehicles require costly feedback devices and sensors, increasing complexity and assembly time, and existing sensorless control algorithms face challenges in initiating motor operation without accurate motor voltage measurement.
Innovation Solution
A method and system that control an electric motor with a plurality of windings coupled to sets of switches, where current flow is monitored to determine if the motor is below or above a predetermined threshold, triggering different control methods to estimate rotor position and speed, either using a sensorless algorithm or a current-based method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback device or position sensor is used to provide speed and position information, then motor control precision is improved, but system cost and complexity increase
Solution Approach 1:
The patent extracts the position sensing function from a separate physical sensor and integrates it into the existing current sensor by utilizing the sixth harmonic component of the phase current. This eliminates the need for dedicated position sensors and their associated wiring harnesses, thereby reducing system complexity while maintaining position measurement capability
Solution Approach 2:
The patent makes the current sensor multi-functional by using it for both current measurement and position estimation. By analyzing the harmonic components of the phase current, the system derives rotor position information from the same sensor that measures current, thus serving multiple purposes with a single device
2Measurement precision
If a feedback device or position sensor is used, then motor control accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive position sensors with a software-based estimation approach that uses existing current measurement infrastructure. The position information is derived computationally from the harmonic analysis of phase currents, eliminating the need for costly hardware sensors and reducing manufacturing costs
3Device complexity
If sensorless control algorithms are used to eliminate position sensors, then system complexity is reduced, but startup control reliability deteriorates due to unavailable motor voltage information
Solution Approach 1:
The patent applies preliminary action by using current measurements taken during the startup phase to estimate initial rotor position and speed before normal sensorless control begins. The sixth harmonic analysis is performed on startup currents to provide accurate initial conditions, ensuring reliable transition to steady-state sensorless operation
Solution Approach 2:
The patent introduces an intermediary estimation process that bridges the gap during startup. By using harmonic analysis of phase currents as an intermediate step, the system obtains reliable position and speed estimates during the critical startup phase where direct voltage measurement is unavailable, enabling smooth transition to normal operation
4Ease of operation
If vector control scheme is used with six power transistors, then motor control performance is improved, but system cost and complexity increase
Solution Approach 1:
The patent extracts the position sensing function from the inverter hardware and relocates it to the control algorithm domain. By deriving position information from current harmonics rather than dedicated sensors, the inverter hardware complexity is reduced while maintaining full vector control capability in the software
Data Source
AI summary
Methods and systems for controlling an electric motor are provided. The motor includes a plurality of windings. Each winding is coupled to a respective set of first and second switches. The first switch of each set of switches is simultaneously activated. Current flow through the plurality of windings is measured while the first switch of each set of switches is activated. The electric motor is controlled according to a first motor control method if the measured current is below a predetermined threshold. The electric motor is controlled according to a second motor control method if the measured current is above the predetermined threshold.