Motor Control Device Switching Axes for Sensorless Estimation
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Solution Overview
Problem
Conventional motor control devices face challenges in accurately estimating rotor position and speed, especially at low speeds, due to the need for complex parameter adjustments and the interdependence of calculation parameters, which complicates optimal motor control.
Innovation Solution
A motor control device that switches between different control methods by varying the rotating axes used for control, allowing easier adjustment of calculation parameters and reducing calculation complexity, by employing a dual estimation processing system that adapts based on rotor speed and time since switching, enabling smooth transitions between high-speed and low-speed control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensorless control methods are used to estimate rotor position and speed, then control can be performed without physical sensors, but estimation accuracy deteriorates at low speeds due to reliance on induced voltage which is insufficient at low rotation speeds
Solution Approach 1:
The patent changes the control parameters by switching between different coordinate systems (d-q axes for high-speed, α-β axes for low-speed) based on rotation speed. This parameter change allows the system to use appropriate estimation methods for each speed range, maintaining accuracy across the full operating range.
Solution Approach 2:
The patent implements dynamic switching between control coordinate systems based on real-time speed detection. The system automatically transitions from d-q axis control at high speeds to α-β axis control at low speeds, and vice versa, making the control system adaptive to operating conditions and maintaining estimation accuracy throughout.
2Adaptability or versatility
If multiple control methods are switched according to rotation speed, then stable control across wide speed range is achieved, but the complexity of switching control increases
Solution Approach 1:
The patent creates a universal control system that can operate in multiple coordinate systems (both d-q and α-β axes) within a single controller. This multi-functionality allows the system to handle both high-speed and low-speed operations without requiring separate control systems, reducing overall complexity while maintaining versatility.
Solution Approach 2:
The patent segments the control range into high-speed and low-speed regions, with each region having its optimized control method. The switching between segments is managed by a simple speed-threshold-based controller, which reduces the complexity of the switching logic while achieving stable control across the full speed range.
3Stability of the object's composition
If different control types are switched within a signal coordinate system, then the rotating axes remain consistent, but the calculation parameters become interdependent and difficult to adjust for optimal control
Solution Approach 1:
The patent uses the rotation speed as an intermediary parameter to determine which coordinate system to use. This simple speed-based selection mechanism decouples the complexity of parameter adjustment from the coordinate system switching, making the system easier to operate while maintaining coordinate consistency within each control mode.
Data Source
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AI summary
Let the rotating axis whose direction coincides with the direction of the current vector that achieves maximum torque control be called the qm-axis, and the rotating axis perpendicular to the qm-axis be called the dm-axis. A motor control device switches its operation between low-speed sensorless control and high-speed sensorless control according to the rotation speed of the rotor. In low-speed sensorless control, the magnetic salient pole of the motor is exploited, and the d-q axes are estimated by, for example, injection of a highfrequency rotating voltage. In high-speed sensorless control, the dm-qm axes are estimated based on, for example, the induction voltage produced by the rotation of the rotor. During high-speed sensorless control, the γ(dm)-axis current is kept at zero irrespective of the δ(qm)-axis current.