Electric Power Steering Motor Control with Disturbance Torque Compensation
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Solution Overview
Problem
Existing motor control systems for electric power steering in automated and assisted driving face challenges in maintaining angle control accuracy due to non-linear disturbance torques such as road surface load torque, friction torque, and steering torque, which are not effectively addressed by traditional PID control methods.
Innovation Solution
A motor control apparatus that includes a manual steering command value generation unit, a summed angle command value calculation unit, and a control unit with a basic torque command value calculation, disturbance torque estimation, and compensation units, which calculates and corrects the torque command based on estimated disturbance torque to improve angle control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If PID control is used for angle feedback control, then the control system is simple to implement, but angle control accuracy decreases due to non-linear disturbance torque
Solution Approach 1:
A disturbance observer is introduced as an intermediary component that estimates disturbance torque (including friction torque, road surface load torque, and steering torque) and feeds this estimation back to the control unit. The control unit then compensates for the estimated disturbance torque in the torque command value, effectively canceling out the non-linear disturbance effects and improving angle control accuracy without significantly increasing system complexity
Solution Approach 2:
The system implements feedback control by using the disturbance observer to continuously monitor and estimate disturbance torque, then feeding this information back to adjust the torque command value. This closed-loop feedback mechanism allows the system to dynamically compensate for non-linear disturbances, resolving the contradiction between simple control implementation and high angle control accuracy
2Measurement precision
If disturbance torque compensation is added to improve angle control accuracy, then angle control accuracy improves, but device complexity increases
Solution Approach 1:
The disturbance observer serves as an intermediary that handles the complex task of disturbance estimation separately from the main control logic. By isolating the complexity into this dedicated observer module, the system achieves high angle control accuracy through disturbance compensation while keeping the overall control system architecture manageable and structured
Solution Approach 2:
The control system is segmented into distinct functional modules: the basic PID control unit, the disturbance observer unit, and the torque compensation unit. This segmentation allows each module to perform its specific function independently, making the overall complex system easier to implement, debug, and maintain while achieving high angle control accuracy through coordinated operation of these modular components
Data Source
AI summary
A manual steering command value generation unit generates a manual steering command value, using a steering torque. A summed angle command value calculation unit calculates a summed angle command value, by adding the manual steering command value to an automatic steering command value. A control unit performs angle control of an electric motor, based on the summed angle command value. The control unit includes a basic torque command value calculation unit that calculates a basic torque command value, a disturbance torque estimation unit that estimates a disturbance torque other than a motor torque of the electric motor applied to an object driven by the electric motor, and a disturbance torque compensation unit that corrects the basic torque command value, based on the disturbance torque. The manual steering command value generation unit uses an estimated torque calculated based on the disturbance torque, when generating the manual steering command value.