Multi-phase Rotor Position Detection via High-Frequency Injection
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Solution Overview
Problem
Existing methods for determining the rotor position in rotating electrical machines, especially in highly dynamic drives, face challenges in reducing noise and torque ripple, which can deteriorate the machine's performance and require complex calculations.
Innovation Solution
The method involves using multi-phase subsystems with PWM-controlled inverters, where high-frequency voltages with shifted phase positions are applied to achieve a position-dependent current change, allowing for accurate rotor position determination with reduced noise and minimal impact on machine performance, and validating results with existing rotor bearing sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency voltages are applied to determine rotor position, then measurement precision is improved, but noise and torque ripple increase
Solution Approach 1:
The patent divides the motor windings into multiple independent subsystems (first subsystem, second subsystem, etc.), each with its own inverter. High-frequency voltages are applied alternately to different subsystems rather than simultaneously to all subsystems. This segmentation allows the harmful torque ripples generated by each subsystem to cancel each other out when the subsystems are properly phased, while still achieving accurate rotor position measurement through the cumulative effect of multiple measurements.
Solution Approach 2:
The patent employs periodic application of high-frequency voltages to different subsystems in a structured sequence. Between controller sampling steps, high-frequency voltages are alternately applied to the first subsystem, then the second subsystem, and so on. This periodic action allows the system to gather position information from multiple subsystems while ensuring that the torque ripple effects occur at different times and cancel each other out, reducing overall noise and vibration.
2Object-generated harmful factors
If multiple subsystems are used with shifted phase positions, then noise is reduced, but device complexity increases
Solution Approach 1:
The patent designs multiple subsystems that are structurally identical and can be controlled by a single controller. Each subsystem serves multiple functions: it contributes to torque production, enables rotor position measurement, and participates in noise cancellation through its specific phase positioning. The controller universally manages all subsystems using the same control algorithm, adapting the high-frequency voltage application pattern based on which subsystem is being activated. This multi-functionality approach reduces overall system complexity despite having multiple subsystems.
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 effectively reduces noise and torque ripple, enabling precise rotor position determination with low computational effort and minimal interference with the machine's operation, while optimizing high-frequency voltage alignment to minimize mechanical vibrations.
Implementation Method 1
At low speeds, so-called anisotropic-based methods are used, which determine the rotor layer via the magnetic anisotropy of the machine
Implementation Method 2
an inverter with pulse width modulation (PWM) is used to generate the adjustable phase voltage of the electrical machines
Implementation Method 3
The control signals of the inverter are calculated by means of a room pointer modulation, which converts the predetermined voltages determined by the regulation in PWM probes
Data Source
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AI summary
The invention relates to a method for determining a rotor position of an electric rotating machine (10). The electric machine (10) comprises at least one first, multi-phase subsystem (21) and one second multi-phase subsystem (22), which each comprise a PWM-controlled inverter (41, 42) for feeding respective winding groups (31, 32). The winding groups (31, 32) of the at least first and second subsystems (21, 22) are arranged substantially electrically offset from one another by 360°. In the method, voltages (u control ) predefined by a controller (50) are altered by feeding high-frequency voltages (u inj ) in order to attain high-frequency current changes. The current changes are then detected in that a current curve of phase currents is ascertained for each subsystem (21, 22) by measuring at least one first phase current and one second phase current. The rotor position is then determined depending on the ascertained current curves and the fed high-frequency voltages (u inj ). The invention additionally relates to an electric machine (10) which is designed for carrying out a method according to the invention.