Dynamic Motor Model Feedforward Control for EPS Torque Precision
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electrical power steering (EPS) systems face challenges in efficiently controlling brushless motors, particularly in quadrants II and IV where regenerative currents can occur, limiting the phase advance angle and requiring effective voltage command calculations to manage torque and current.
Innovation Solution
A motor control system that uses dynamic inverse motor model equations to generate voltage commands based on rotational velocity, torque commands, and phase advance angles, allowing the phase advance angle to exceed the impedance angle and accounting for regenerative currents in quadrants II and IV by limiting motor regenerative current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If steady state representation of motor characteristics is used for feedforward control, then control simplicity is maintained, but control precision deteriorates due to inability to accurately manage regenerative currents in quadrants II and IV
Solution Approach 1:
The patent transitions from steady-state motor models to dynamic motor models that capture transient behavior. The dynamic model includes differential equations that represent the time-varying electrical and mechanical characteristics of the motor, enabling accurate prediction of regenerative currents during transient operations in quadrants II and IV.
Solution Approach 2:
The patent changes the mathematical representation from algebraic steady-state equations to differential dynamic equations. This parameter change allows the model to capture the transient nature of regenerative currents, which cannot be accurately represented by steady-state parameters alone.
2Stability of the object's composition
If phase advance angle is limited to impedance angle, then motor operation stability is maintained, but torque control range deteriorates
Solution Approach 1:
The patent employs feedback mechanisms where the actual motor currents and voltages are continuously monitored and fed back to the controller. This feedback allows the system to adjust the phase advance angle dynamically based on actual operating conditions, ensuring stability while expanding the torque control range beyond the traditional impedance angle limitation.
Solution Approach 2:
The patent uses predictive modeling to calculate the required voltage commands in advance, considering the dynamic behavior of the motor. By predicting the motor response and pre-calculating the necessary voltage adjustments, the system can safely extend the phase advance angle while maintaining stability through proactive control adjustments.
3Measurement precision
If dynamic inverse motor model equations are used to allow phase advance angle to exceed impedance angle, then torque control precision is improved, but calculation complexity increases
Solution Approach 1:
The patent segments the complex dynamic control problem into manageable parts by separating the voltage command calculation into distinct components: back-EMF compensation, resistive voltage drop compensation, and inductive voltage drop compensation. This segmentation allows each component to be calculated and adjusted independently, reducing overall calculation complexity while maintaining precision.
Solution Approach 2:
The patent implements a simplified version of the full dynamic model by selectively applying the necessary dynamic corrections only when needed (e.g., during transient conditions or in quadrants II and IV). During steady-state operation, the system can use simpler control logic, reducing calculation complexity while maintaining torque control precision when it matters most.
Data Source
AI summary
A motor control system comprising a motor configured to operate at a rotational velocity and a control module in communication with the motor is provided. The control module is configured to receive a torque command indicating a desired amount of torque to be generated by the motor, obtain a rotational velocity of the motor, receive a desired phase advance angle for driving the motor; and generate a voltage command indicating a voltage magnitude to be applied to the motor based on the rotational velocity of the motor, the motor torque command, and the desired phase advance angle by using a plurality of dynamic inverse motor model equations that (i) allow the desired phase advance angle to exceed an impedance angle of the motor and (ii) specify that the voltage magnitude is a function of a voltage magnitude of a previous voltage command.