Steering Effort Hysteresis Shaping for SbW Systems
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Solution Overview
Problem
Steering systems, particularly in connected steering systems like electronic power steering (EPS) and steer-by-wire (SbW), face challenges in achieving the desired hysteresis in the steering effort profile, leading to either a springy or high-friction feel for the driver.
Innovation Solution
A method for performing hysteresis shaping in SbW steering systems, which involves determining the desired hysteresis and deciding whether to perform hysteresis subtraction or addition. This method calculates the respective hysteresis values and modifies the estimated rack load to generate a reference torque, thereby controlling the handwheel based on the adjusted torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If hysteresis is increased in the steering effort profile, then the natural feel is improved, but the friction increases making the steering feel heavy
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the hysteresis parameter in the steering effort profile. The controller modifies the reference torque command based on calculated hysteresis values, changing the system parameters in real-time to achieve the desired natural feel while controlling friction. This involves calculating hysteresis addition or subtraction values and applying them to the reference torque generated by the effort function.
2Force
If hysteresis is decreased in the steering effort profile, then the friction is reduced, but the steering feel becomes springy
Solution Approach 1:
The patent uses parameter changes to dynamically adjust the hysteresis level in the steering effort profile. By calculating appropriate hysteresis addition or subtraction values and applying them to the reference torque, the system can reduce friction when needed while preventing the steering feel from becoming springy. The effort function generates reference torque that incorporates these hysteresis adjustments.
3Ease of operation
If hysteresis is added to the steering effort profile, then the natural feel is improved, but the device complexity increases
Solution Approach 1:
The patent implements feedback by calculating the actual hysteresis from sensor data (handwheel torque sensor and rack position sensor) and comparing it with the desired hysteresis. The controller uses this feedback to determine whether hysteresis addition or subtraction is needed, and calculates appropriate correction values. This closed-loop approach manages control complexity through systematic feedback processing.
Solution Approach 2:
The patent introduces an intermediary approach by using a dedicated effort function that generates reference torque commands. This intermediary layer between the raw sensor data and the final handwheel control allows the system to manage complexity through a structured intermediate processing stage that handles hysteresis calculations and torque generation separately.
4Force
If hysteresis is subtracted from the steering effort profile, then the friction is reduced, but the natural feel deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the hysteresis parameter in the steering effort profile. The controller modifies the reference torque command based on calculated hysteresis values, changing the system parameters in real-time to achieve the desired natural feel while controlling friction. This involves calculating hysteresis addition or subtraction values and applying them to the reference torque generated by the effort function.
Data Source
AI summary
A method for performing hysteresis shaping in a steer-by-wire (SbW) steering system of a vehicle includes determining a desired hysteresis associated with rotating a handwheel of the vehicle, determining, based on the desired hysteresis, whether to perform hysteresis subtraction or perform hysteresis addition, in response to a determination to perform hysteresis subtraction, calculating a hysteresis subtraction value, modifying an estimated rack load based on the hysteresis subtraction value, and generating a reference torque based on the estimated rack load as modified based on the hysteresis subtraction value, in response to a determination to perform hysteresis addition, calculating a hysteresis addition value and generating the reference torque based on hysteresis addition value, and controlling the handwheel based on the reference torque.