Steer-by-Wire Artificial Hysteresis for Natural Steering Feel
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Solution Overview
Problem
Steer-by-wire steering systems lack the natural hysteresis effect present in electromechanical power steering systems, leading to a noticeable difference in driving feel, especially during high dynamic maneuvers.
Innovation Solution
Implementing an artificial hysteresis mechanism in the steer-by-wire system by modifying the steering wheel angle to mimic the hysteresis component of electromechanical systems, using a control unit to calculate an operation signal for the road wheel actuator based on the modified steering wheel angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the connection between the road wheel actuator and the steering wheel is simulated to be infinite stiff, then the steering system achieves precise position control, but the driver experiences a notable difference in driving feel compared to electric power steering systems
Solution Approach 1:
The patent applies parameter changes by modifying the steering wheel angle through artificial hysteresis. The control unit adjusts the reference steering wheel angle based on detected steering wheel angle and torque, creating a modified angle that mimics the compliant mechanical connection of traditional EPS systems. This allows the system to maintain infinite stiffness for position control while simulating the natural hysteresis effect for improved driving feel.
2Ease of operation
If artificial hysteresis is applied to modify the steering wheel angle, then the driving feel mimics electromechanical power steering, but the complexity of the control system increases
Solution Approach 1:
The patent replaces the mechanical hysteresis component of traditional EPS with a software-based artificial hysteresis mechanism. Instead of using compliant mechanical elements, the control unit calculates a modified steering wheel angle by comparing the actual steering wheel angle with a reference angle and applying hysteresis logic. This substitution reduces mechanical complexity while achieving the desired driving feel.
3Adaptability or versatility
If the steering wheel angle is modified by applying artificial hysteresis, then the hysteresis component depends on torque applied to the steering column like in electromechanical systems, but the calculation complexity increases
Solution Approach 1:
The patent implements feedback by continuously detecting the steering wheel angle and torque using sensors, then using this information to calculate the modified steering wheel angle. The control unit adjusts the reference angle based on the detected torque and current steering position, creating a dynamic hysteresis effect that adapts to driving conditions. This feedback mechanism enables torque-dependent hysteresis while keeping calculations manageable through iterative approximation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified steering feel in steer-by-wire systems mimics that of electromechanical power steering, providing a more comfortable driving experience.
Implementation Method 1
The compliance is noticed as a hysteresis component in rotational movement of the steering wheel with respect to the pinion, which is dependent upon torque applied on the steering column
Implementation Method 2
a road wheel actuator for turning the steerable road wheels
Data Source
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AI summary
The invention relates to a method to control a steer-by-wire steering system (1) of a road vehicle, wherein the steer-by-wire steering system (1) comprises a steering wheel (3) coupled to a steering shaft (2), a road wheel actuator (5) for turning steerable road wheels (4), a shaft sensor, which detects a rotation of the steering shaft (2) and a control unit (10), which calculates an operation signal for the road wheel actuator (5) from the signal detected by the shaft sensor, wherein the method includes the following steps: - Determining the real steering wheel angle (α) by the shaft sensor; - Modifying the real steering wheel angle (α) by applying an artificial hysteresis, which creates an offset between the real steering wheel angle (α) and the modified steering wheel angle (αmod) to mimic the behavior of electromechanical power steering mechanisms; and - Calculating the motor torque request for the road wheel actuator (5) based on the modified steering wheel angle (αmod).