Variable Magnetization Controller Torque Pulsation Feedback
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Solution Overview
Problem
Existing controllers for variable magnetization machines in electric and hybrid electric vehicles face challenges in efficiently managing magnetization levels, leading to pulsating torque and complexity in look-up table creation, which are not motor-specific and require open-loop control, making them inefficient and less adaptable.
Innovation Solution
A variable magnetization machine controller comprising a current command module, a magnetization module, and a reducing current module that computes vector current commands in the dq axis, applies magnetization control pulses to the d-axis, and reduces q-axis current based on estimated and measured torque, ensuring constant torque output and adaptability across different machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If only the d-axis current is increased to increase magnetization level, then the torque output of the motor is increased, but the torque becomes pulsating due to pulsating d-axis current and changes in magnetization level
Solution Approach 1:
The patent employs feedback control by measuring the actual torque output and using it to adjust the q-axis current command. The torque measurement unit continuously monitors the torque, and this information is fed back to the controller which adjusts the q-axis current to compensate for pulsations, thereby maintaining smooth torque output while increasing magnetization level through d-axis current control.
Solution Approach 2:
The patent changes the control parameters by switching from conventional scalar control to vector control in the dq reference frame. By independently controlling d-axis current (for magnetization) and q-axis current (for torque), the system can adjust magnetization level while maintaining torque smoothness through proper parameter coordination and feedback adjustment.
2Ease of operation
If a look-up table is used to set magnetization level based on d-axis and q-axis current values, then the controller can regulate both currents, but the look-up table creation becomes very complicated and time consuming
Solution Approach 1:
The patent extracts the complex look-up table from the control system by eliminating the need for pre-computed tables. Instead of using a 2-dimensional look-up table that requires complicated creation and storage, the system directly calculates current commands based on real-time torque measurement and control algorithms, simplifying the controller structure and reducing computational burden.
Solution Approach 2:
The patent replaces the mechanical approach of using pre-stored look-up tables with a computational approach based on real-time torque measurement and feedback control. This substitution eliminates the need for complex table creation, storage, and retrieval operations, replacing them with direct mathematical calculations that adapt to real-time operating conditions.
3Adaptability or versatility
If open loop control is used to determine q-axis current, then the same look-up table may not necessarily be useful with different motors, but creating a new look-up table for each motor is also complex
Solution Approach 1:
The patent uses feedback control with torque measurement to make the control system adaptive to different motors. By continuously measuring the actual torque and adjusting the q-axis current command based on the difference between target and actual torque, the system automatically adapts to each motor's characteristics without requiring pre-programmed look-up tables, thereby achieving both versatility and simplicity.
Solution Approach 2:
The system performs self-adjustment by using its own torque measurement to automatically tune the control parameters. Each motor essentially calibrates the control system through its own operating characteristics, as the feedback loop learns the motor's response and adjusts accordingly, eliminating the need for external calibration or motor-specific look-up tables.
4Speed
If magnetization level is increased to increase torque for vehicle acceleration, then the vehicle speed can be increased, but the torque output becomes pulsating which affects vehicle performance
Solution Approach 1:
The patent applies feedback control by measuring the actual torque output and using this information to adjust the q-axis current command in real-time. This feedback mechanism compensates for the pulsations introduced by variable magnetization control, ensuring smooth torque delivery to the vehicle while maintaining the ability to increase vehicle speed through magnetization level adjustment.
Solution Approach 2:
The patent changes the control approach by using vector control in the dq reference frame with independent d-axis and q-axis current control. This parameter separation allows the system to adjust magnetization (d-axis) for speed control while independently managing torque smoothness (q-axis) through feedback, thereby achieving both high vehicle speed and smooth torque delivery.
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 solution provides improved torque linearity, reduced pulsating torque, and ease of calculation, making it insensitive to parameter deviations and motor-specific characteristics, thus enhancing the control of magnetization levels for efficient vehicle acceleration.
Implementation Method 1
a magnetization module to apply a magnetization control pulse to a d-axis current
Implementation Method 2
an electric motor having variable magnetization characteristics as understood in the art
Data Source
Figure 1
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AI summary
A variable magnetization machine controller (100) comprises a current command module (102), a magnetization module (104) and a reducing current module (106). The current command module (102) computes a vector current command in a dq axis based on a torque command. The magnetization module (104) applies a magnetization control pulse to a d-axis current of the vector current command. Thus, the reducing current module (106) applies a reducing current to a q-axis current of the vector current command based on the torque command and one of an estimated torque of the variable magnetization machine (10) and a measured torque of the variable magnetization machine (10).