Traction Motor Current Observer With DQ-Axis Predictive Control
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Solution Overview
Problem
Current current regulators for vehicle electric traction motors face challenges in accurately predicting and controlling current signals for IPM motors, leading to inefficiencies in torque delivery and potential errors in sensor measurements.
Innovation Solution
A current observer system that includes separate controllers and models for direct-axis and quadrature-axis current predictions, with adjustable bandwidths and parameter tuning using look-up tables, polynomial functions, and online derivative calculations, to provide accurate predicted current signals for the next control cycle, and to convert three-phase AC to direct-axis and quadrature-axis currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single controller and model are used for current prediction, then device complexity is reduced, but current control accuracy deteriorates due to inability to independently adjust direct-axis and quadrature-axis parameters
Solution Approach 1:
The patent divides the current control system into two independent parallel controllers: one for direct-axis current prediction and another for quadrature-axis current prediction. Each controller has its own model and parameter set, allowing independent optimization of each axis without interfering with the other, thereby achieving higher overall control accuracy while maintaining manageable system complexity through modular architecture
2Measurement precision
If sensor bandwidth is increased to improve measurement accuracy, then measurement precision improves, but susceptibility to sensor errors and noise increases
Solution Approach 1:
The patent implements feedback mechanisms where the predicted current values from the models are continuously compared with actual sensor measurements. The bandwidth of each controller is independently adjusted based on this feedback to optimize the balance between tracking accuracy and noise rejection, allowing the system to adapt to varying operating conditions and maintain reliability across different scenarios
3Productivity
If parameter tuning is performed offline using look-up tables, then computational complexity during operation is reduced, but adaptability to changing operating conditions deteriorates
Solution Approach 1:
The patent employs dynamic parameter adjustment where controller bandwidths and model parameters are tuned based on real-time operating conditions such as motor speed, load, and temperature. The system can switch between pre-computed look-up tables for high-speed operation and online adaptive tuning for varying conditions, combining the advantages of both approaches to maintain both computational efficiency and adaptability across the full operating range
Data Source
AI summary
A system in a vehicle includes a current regulator to obtain current commands from a controller based on a torque input and provide voltage commands and an inverter to use the voltage commands from the current regulator and direct current (DC) supplied by a battery to provide alternating current (AC). An electric traction motor provides drive power to a transmission of the vehicle based on injection of the AC from the inverter. A current observer obtains measured input current signals based on the AC for a current control cycle and provides predicted current signals for a next control cycle to the current regulator using a model. The current observer includes a controller to check output of the model against the measured input current signals. The current observer tunes parameters of the controller and the model used to generate the predicted current signals based on the measured input current signals.