Multiphase Motor Rotor Position Estimation Without Back-EMF Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensorless methods for brushless multiphase electric motors struggle with accurate rotor position determination at low rotational speeds or standstill, leading to inefficient start-up, increased noise, and potential loss of synchronous field, especially in applications where back EMF signals are insufficient.
Innovation Solution
A method that determines phase voltages and currents to calculate a position substitute signal from the angle of current or voltage vectors, allowing for motor control without additional sensors, enabling operation at low speeds and reducing start-up time while improving efficiency and acoustics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless methods based on back EMF detection are used for rotor position determination, then the device complexity is reduced by avoiding additional sensors, but the measurement precision deteriorates at low rotational speeds or standstill due to insufficient back EMF signals
Solution Approach 1:
The patent changes the operating parameters by applying specific voltage vectors and measuring current responses at different excitation states. Instead of relying on back EMF magnitude, the system uses current measurement during voltage application to determine rotor position, effectively changing from a passive detection method to an active measurement method that works at all speeds including standstill
Solution Approach 2:
The patent introduces current measurement as an intermediary parameter to indirectly determine rotor position. Rather than directly measuring back EMF or using mechanical sensors, the system uses the current response to applied voltage vectors as a mediator to infer rotor position, enabling sensorless operation with improved precision at low speeds
2Use of energy by moving object
If the motor is operated at low rotational speeds or standstill with conventional sensorless methods, then energy consumption is reduced, but the reliability deteriorates due to loss of synchronous field and inaccurate position determination
Solution Approach 1:
The patent applies preliminary voltage vectors to the motor phases before attempting to determine rotor position or initiate movement. By pre-applying specific voltage patterns and measuring the resulting current responses, the system establishes accurate position information in advance, ensuring reliable operation from standstill without requiring high energy input or risking loss of synchronous field
3Measurement precision
If additional rotary sensors are used for accurate rotor position determination, then the measurement precision is improved, but the device complexity and cost increase
Solution Approach 1:
The patent enables the motor system to determine its own rotor position using its existing electrical components (power electronics, current sensors already present for control). The system serves itself by using the current measurement infrastructure already required for motor control to also provide position information, eliminating the need for separate rotary sensors while maintaining measurement precision
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 method allows for reliable and efficient operation of brushless multiphase electric motors at low rotational speeds, reducing start-up time and noise, and enhancing motor robustness without requiring additional sensors or specific motor properties.
Implementation Method 1
the rotor of the electric motor suitably has a number of permanent magnets, wherein the interaction of the permanent magnets with the rotary field produces a resulting torque, which sets the rotor in rotation
Implementation Method 2
The motor current is generated as a multiphase output current by way of pulse-width-modulated (PWM) actuation or control of semiconductor switches of the bridge circuit
Data Source
AI summary
A method for operating a brushless and sensorless multi-phase electric motor. At least two phase voltages and at least two phase currents of the electric motor are determined. A voltage vector is determined from the phase voltages and/or a current vector is determined from the phase currents. A position substitute signal is determined as a measure of a rotor position on the basis of an angle of the current vector and/or of the voltage vector. A rotation value is calculated on the basis of the position substitute signals, and the electric motor is controlled by open-loop and/or closed-loop technology on a basis of the rotation value.