Variable Gain Integrator for EPS Motor Control
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Solution Overview
Problem
Existing electric power steering (EPS) systems face challenges in efficiently managing the calculation load when switching between manual driving and automatic driving modes, requiring expensive arithmetic circuits with high data processing demands.
Innovation Solution
A control device with a processor and memory that performs proportional integral (PI) control to calculate a target assist torque for the EPS motor, with a variable gain integrator and the ability to switch between enabling and disabling the integrator based on driving modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switching control between assist control unit and angle control unit by adjusting weighting factor is implemented, then both manual driving and automatic driving functions are realized, but calculation load increases and expensive arithmetic circuits are required
Solution Approach 1:
The patent changes the control parameter from a continuously adjustable weighting factor to a discrete switch between two extreme states (assist control and angle control). This eliminates the need for complex real-time calculation of weighting factors and their derivatives, significantly reducing the computational load while maintaining dual-mode functionality.
Solution Approach 2:
The control system is segmented into distinct manual driving mode (assist control) and automatic driving mode (angle control), with clear switching conditions. This segmentation avoids the need for continuous weighted addition calculations by treating each mode as an independent control strategy that is activated based on driving mode detection.
2Adaptability or versatility
If switching control between assist control unit and angle control unit by adjusting weighting factor is implemented, then both manual driving and automatic driving functions are realized, but expensive arithmetic circuits with high data processing demands are required
Solution Approach 1:
By changing from continuous parameter adjustment (weighting factor) to discrete mode switching, the patent simplifies the arithmetic circuit requirements. The circuit only needs to implement basic switching logic and two distinct control algorithms, rather than complex real-time weighted addition and derivative calculations, thereby reducing manufacturing costs.
3Device complexity
If variable gain integrator is used in PI control, then calculation load is reduced, but control precision may be affected
Solution Approach 1:
The integrator gain is made dynamic by switching between enabled and disabled states based on the driving mode. In manual driving mode, the integrator is disabled to provide responsive steering assistance. In automatic driving mode, the integrator is enabled to eliminate steady-state errors and improve positioning precision. This dynamic switching maintains control precision when needed while reducing calculation load when the integrator is not required.
Data Source
AI summary
In a control device to control a motor in an electric power steering apparatus including the motor, processor executes, according to a program calculation of a target assist torque by performing proportional integral (PI) control based on a target steering wheel angle and a steering angle, and control of the motor based on the target assist torque. A gain of an integrator used for integral (I) control of the PI control is variable.