Steering Wheel Return Control via Dynamic Correction Gains
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Solution Overview
Problem
Conventional electric power steering devices often cause an uncomfortable steering experience due to complex return control mechanisms, which are triggered by specific torque and torque change rate conditions, leading to inefficient steering wheel return control.
Innovation Solution
An electric power steering device that calculates a return command value by combining a basic return command value with correction gains based on vehicle speed and steering torque changes, allowing for simplified and improved steering wheel return control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional electric power steering devices use complex return control mechanisms triggered by specific torque and torque change rate conditions, then steering wheel return control can be achieved, but it causes an uncomfortable steering experience
Solution Approach 1:
The patent changes the control parameters from complex conditional logic (torque threshold + torque change rate threshold) to a simplified continuous control approach using correction gains. The return command value is calculated by applying correction gains to basic return command values based on steering angle, creating a smoother and more comfortable steering experience without complex conditional judgments.
Solution Approach 2:
The patent introduces dynamic correction gains that continuously adjust the return control based on real-time steering conditions. Instead of fixed threshold-based control, the system dynamically modifies the return command value using correction gains calculated from steering angle and its derivatives, enabling adaptive and comfortable steering wheel return across various operating conditions.
2Device complexity
If conventional electric power steering devices monitor whether two conditions are satisfied simultaneously (steering torque at threshold and steering wheel in let go state), then return control can be triggered, but the control becomes complicated
Solution Approach 1:
The patent extracts the essential function of return control from complex conditional monitoring and implements it through a dedicated return command value calculation unit. This unit continuously calculates return command values based on steering angle and correction gains, separating the return control function from the main steering control logic and eliminating the need for complex conditional judgments.
Solution Approach 2:
The patent implements continuous feedback through correction gain calculation units that monitor steering angle and its changes in real-time. The correction gains are continuously updated based on current steering conditions and fed back to adjust the return command value, creating a reliable and responsive control system without complex conditional logic.
3Speed
If electric power steering devices perform steering wheel return control only when specific conditions are met, then control can be simplified, but the returnability at low speeds is insufficient
Solution Approach 1:
The patent makes the return control adaptive to different vehicle speeds through dynamic correction gains. The correction gain calculation units adjust the return command value based on real-time steering conditions, enabling the system to provide appropriate return force at both low and high speeds, improving returnability at low speeds while maintaining adaptability across all operating conditions.
Data Source
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AI summary
An electric power steering device includes a basic return command value calculation unit configured to calculate a basic return command value in a direction returning the steering wheel to a neutral position, on the basis of detection results of a steering angle detector detecting a steering angle of the steering wheel, a first correction gain calculation unit configured to calculate a first correction gain correcting the basic return command value, on the basis of detection results of a vehicle speed detector detecting vehicle speed, and a second correction gain calculation unit configured to calculate a second correction gain correcting the basic return command value, on the basis of a change amount of the steering torque detected by the torque sensor. The basic return command value is corrected by the first and second correction gains so as to calculate a return command value. The return command value is added to the assist command value so as to drive the electric motor.