Rotary Motor Current Control With Speed-Adaptive d-Axis Gain
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Solution Overview
Problem
Existing controllers for rotary electric machines do not effectively set control gains for d-axis current command values based on q-axis current deviations, leading to variable responses of q-axis current and torque due to rotational angle speed changes, which affects performance.
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, and a switching control unit, which adjusts the proportional gain for d-axis current command values in inverse proportion to the rotational angle speed to stabilize q-axis current responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the current command value of d-axis is controlled based on q-axis current deviation with a fixed proportional gain, then the control structure is simple, but the response of q-axis current and torque varies with rotational angle speed
Solution Approach 1:
The proportional gain is changed from a fixed value to a dynamic value that varies with rotational angle speed. Specifically, the proportional gain is set in inverse proportion to the rotational angle speed, making the control system adaptive to different operating conditions and maintaining stable response characteristics across the speed range.
Solution Approach 2:
The control parameter (proportional gain) is changed according to the operating condition (rotational angle speed). By adjusting the proportional gain based on the detected rotational angle speed, the system maintains optimal control performance across different speed ranges while keeping the overall control structure relatively simple.
2Speed
If the proportional gain is increased to improve q-axis current response, then the response speed increases, but the torque response becomes unstable at different rotational speeds
Solution Approach 1:
The proportional gain is made dynamic by linking it to the rotational angle speed. At higher speeds, the gain is reduced to prevent excessive response and maintain stability, while at lower speeds, the gain is increased to ensure adequate response speed. This dynamic adjustment resolves the contradiction between response speed and stability across different operating conditions.
Solution Approach 2:
The proportional gain parameter is adjusted according to the rotational angle speed parameter. This parameter change strategy allows the system to optimize the balance between response speed and stability for each operating condition, preventing the torque response from becoming unstable while maintaining adequate response performance.
3Power
If magnetic flux weakening control is performed at high speed rotation, then the induced voltage is reduced, but the q-axis current cannot be properly energized without proper gain adjustment
Solution Approach 1:
During magnetic flux weakening control at high speeds, the proportional gain is automatically reduced due to the inverse proportionality relationship with rotational angle speed. This gain adjustment ensures that the q-axis current control remains accurate and reliable even when the induced voltage is reduced, maintaining proper current energization and torque production throughout the high-speed operating range.
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 stabilizes q-axis current responses and ensures a desired torque response by canceling the effect of rotational angle speed on current changes, improving the overall performance 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
Data Source
AI summary
To provide a controller for rotary electric machine and an electric power steering apparatus which can set a control gain which is used for controlling the d-axis current command value based on the q-axis current deviation between the current command value of q-axis and the current detection value of q-axis, considering the response of the current of q-axis. A controller for rotary electric machine changes the current command value of d-axis, based on a value obtained by multiplying a proportional gain to a q-axis current deviation which is a deviation between the current command value of q-axis and the current detection value of q-axis; and changes the proportional gain in inverse proportion to the rotational angle speed.