Angle Frequency Selector for Sensorless Motor Control
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Solution Overview
Problem
Conventional sensorless motor control techniques are not well-suited for low-speed control of AC motors due to inadequate back emf signal strength, leading to inaccuracies and the need for mechanical sensors, which increase complexity and cost.
Innovation Solution
A controller architecture combining high-speed and low-speed estimators, with an angle/selector function that switches between them based on motor speed, using either sensorless or sensor measurements to maintain accurate control from zero speed to maximum speed with minimal glitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless motor control techniques are used, then cost and complexity are reduced, but measurement precision deteriorates at low speeds
Solution Approach 1:
The control system is segmented into two distinct estimation paths: a high-speed estimator using back emf signals and a low-speed estimator using injected excitation signals. The angle/frequency selector switches between these segments based on operating speed, allowing each segment to be optimized for its specific speed range without compromising overall system accuracy
Solution Approach 2:
The system changes the estimation parameters dynamically based on motor speed. At high speeds, the system uses back emf-based estimation with specific frequency thresholds. At low speeds, it transitions to excitation signal-based estimation with different frequency characteristics, thereby maintaining measurement precision across the entire speed range while keeping the system sensorless
2Measurement precision
If mechanical sensors are used, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent replaces mechanical sensors (encoders, resolvers) with an electronic estimation system that uses electrical signals (back emf and injected excitation signals) to determine rotor position and velocity. This substitution eliminates mechanical components, wiring, and connectors while maintaining measurement precision through intelligent signal processing and dual-estimator architecture
3Device complexity
If a single estimator is used, then device complexity is reduced, but adaptability deteriorates across speed ranges
Solution Approach 1:
The estimator architecture is made dynamic through the angle/frequency selector that continuously monitors motor speed and switches between the high-speed and low-speed estimators. This dynamic adaptation allows the system to maintain optimal estimation accuracy across the entire speed range, from zero speed to maximum speed, while managing complexity through structured modular design
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 stable control of AC motors across their entire speed range, reducing reliance on mechanical sensors and improving efficiency by using a hybrid estimation method that adapts to different speed regimes.
Implementation Method 1
Sensorless induction motor control is commonly implemented by estimating the back electromagnetic force induced in the stator windings by the rotation of the rotor, from which the rotor position and velocity can be determined.
Implementation Method 2
One class of these technique uses the inherent saliency (i.e., the extent to which induction is dependent on rotor position) of the electric motor to produce a signal from which rotor position may be deduced. These conventional IPD techniques inject a high frequency carrier signal into the stator reference voltage signal. The response of the stator windings to these high frequency components, as reflected in stator feedback current, is then evaluated by a processor in the motor control system to determine the position of the rotor.
Data Source
AI summary
A motor controller architecture and method of operating the same. The motor controller includes a function for estimating the low speed operation of the motor, for example by evaluating the response to a periodic excitation signal injected into the control loop of the controller architecture. Control logic for controlling the motor at transitional speeds between low speed control and high speed (back emf) control is provided in some embodiments.