Rotary Motor Controller for Parameter-Free Flux Weakening
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Solution Overview
Problem
In magnetic flux weakening control of permanent magnet type synchronous rotary electric machines, accurate information about rotor inductances and interlinkage flux is necessary for setting optimal current command values. However, without this information, or if it varies due to aging or temperature changes, the accuracy of current command settings is compromised, leading to suboptimal magnetic flux weakening and torque output.
Innovation Solution
A controller for rotary electric machines that includes a current detection unit, a current coordinate conversion unit, a current command value calculation unit, a voltage command value calculation unit, and a switching control unit. This controller adjusts the current command value of the d-axis based on the deviation between an offset q-axis current command value and the current detection value of q-axis, allowing for appropriate magnetic flux weakening without relying on information about rotor inductances and interlinkage flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If proportional control or integral control based on q-axis current deviation is used for magnetic flux weakening control, then the current command values of d-axis and q-axis can be calculated without using information on inductance and interlinkage flux, but when induced voltage decreases and q-axis current is no longer limited by voltage limit ellipse, the q-axis current deviation becomes 0 and the current of d-axis cannot be decreased appropriately, causing inappropriate weakening magnetic flux
Solution Approach 1:
The patent introduces feedback control by continuously monitoring the q-axis current detection value and comparing it with the q-axis current command value. The control system adjusts the d-axis current command value based on the detected q-axis current deviation, creating a closed-loop feedback mechanism that maintains stable magnetic flux weakening control across varying rotational speeds without requiring accurate inductance and interlinkage flux information.
2Measurement precision
If accurate information on inductance and interlinkage flux is used for feedforward setting of current command values, then optimal current command values can be set, but if inductance and interlinkage flux vary due to aging change or temperature characteristic, the setting accuracy of current command values deteriorates
Solution Approach 1:
The control system performs self-adjustment by automatically detecting the actual q-axis current and using this detection value to determine the appropriate d-axis current command value. The system serves itself by eliminating the need for external accurate parameter information (inductance and interlinkage flux), instead relying on real-time current detection and feedback to maintain optimal control performance under varying conditions.
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
The controller effectively adjusts the current command values to maintain optimal magnetic flux weakening and torque output, even in conditions where rotor inductance and interlinkage flux information is unavailable or varies, thereby improving the stability and efficiency of the rotary electric machine.
Implementation Method 1
the induced voltage proportional to the rotational angle speed of the rotor is generated by the interlinkage flux of the permanent magnet
Implementation Method 2
the magnetic flux weakening control which increases the current of d-axis in the negative direction, generates the magnetic flux which weakens the interlinkage flux of the permanent magnet in the windings, and reduces the induced voltage
Data Source
AI summary
To provide a controller for rotary electric machine and an electric power steering apparatus which can increases decreases an increase amount of the current of d-axis in the negative direction appropriately, and can perform the weakening magnetic flux appropriately, irrespective of increase and decrease in the rotational angle speed, without using the information on the inductance and the interlinkage flux of the rotor. A controller for rotary electric machine, in a case where the current command value of q-axis is a positive value, changes the current command value of d-axis, based on a deviation between an offset q-axis current command value obtained by subtracting the q-axis offset value of the positive value from the current command value of q-axis, and the current detection value of q-axis.