Synchronous Motor Rotor Angle Detection Without Position Sensors
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Solution Overview
Problem
Conventional methods for determining the angular position of a rotor in an inverter-fed synchronous motor often require additional sensors, which increases complexity and cost, and may not provide unambiguous results due to symmetries in the flux-value dependence.
Innovation Solution
A method using signal electronics with a control unit and current-acquisition device to control stator current to predefined setpoints, determine stator flux from voltage and current characteristics, and utilize interpolation functions to unambiguously determine the angular position without additional sensors, by comparing flux values at different actuation angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional sensors are used to determine angular position, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system uses existing current-acquisition devices and control units to determine angular position, making the system self-sufficient without additional sensors. The control unit processes stator current and voltage data that are already being acquired for motor control purposes, thereby serving dual functions.
Solution Approach 2:
The patent replaces physical sensors (mechanical/electrical detection devices) with a computational approach using mathematical models and signal processing. The angular position is derived through calculations based on electrical measurements rather than direct physical sensing.
2Measurement precision
If conventional sensor-based methods are used, then angular position can be determined, but cost increases
Solution Approach 1:
The control unit and current-acquisition devices serve dual purposes: both motor control and angular position determination. This eliminates the need for separate sensing systems, reducing component count and manufacturing cost.
Solution Approach 2:
Existing components (control unit, current-acquisition devices, voltage measurements) are made multi-functional by using them for both motor control operations and angular position determination, thereby avoiding additional costs for dedicated sensing hardware.
3Device complexity
If single setpoint current is used for flux determination, then measurement process is simplified, but angular position determination becomes ambiguous
Solution Approach 1:
The system performs periodic measurements by alternating between different setpoint currents (e.g., d-axis and q-axis directions). This periodic switching enables the determination of multiple flux components, which are then used to calculate the unambiguous angular position.
Solution Approach 2:
The patent transitions from single-dimensional measurement (one setpoint current) to multi-dimensional measurement by using multiple setpoint currents in different directions. This adds temporal and directional dimensions to the measurement process, enabling unambiguous angle determination through comparison of multiple flux values.
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 and unambiguous determination of the rotor's angular position without additional sensors, reducing complexity and cost, while utilizing minimal memory storage for flux-value dependence representation.
Implementation Method 1
the inverter is controlled by a signal electronics having a control unit... the synchronous motor has a stator winding, which is fed by a three-phase voltage, i.e. stator voltage, which is set by the inverter such that the acquired stator current is controlled to a predefined setpoint stator current
Implementation Method 2
a stator flux is determined from the time characteristic of the stator voltage and the acquired values of the stator current
Implementation Method 3
an angle value, in particular the angular position, is determined from the determined stator flux and a flux-value dependence as a function of the stator current
Data Source
AI summary
A method for determining an angular position of a rotor of a synchronous motor, having a stator winding fed by a three-phase voltage set by an inverter, includes: supplying a control signal to the inverter to set the three-phase voltage fed to the motor as a stator voltage to control a motor current, acquired by a current-acquisition device, to a setpoint stator current; determining a stator flux from a time characteristic of the stator voltage and an acquired value of the stator current; and determining the angular position of the rotor from the stator flux and a flux-value dependence as a function of the stator current.