Steer-by-Wire Mode Transition Torque Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In vehicles equipped with a steer by wire (SbW) system, changing driver modes from comfort to sports modes results in rapid increases in motor torque, leading to noise and changes in steering feel, and can affect vehicle behavior by altering the target rack position.
Innovation Solution
A steering control apparatus that includes a communicator to receive driver mode change commands, rack position information, and torsion bar torque information, and a controller to determine mode changes and control output torque for the steer wheel feedback actuator, using rate limiting and initial value resetting to smooth mode transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If driver mode is changed from comfort mode to sports mode in SbW system, then driver mode switching functionality is achieved, but motor torque rapidly increases causing noise and changing steering feel
Solution Approach 1:
The controller determines whether to change the driver mode based on the rack position before actually executing the mode change. By checking the rack position in advance and only allowing mode changes when the rack is at a specific position (indicating the steering wheel is centered), the system prevents abrupt torque transitions and associated noise. This preliminary check ensures smooth mode transitions without disturbing the driver.
Solution Approach 2:
The controller continuously monitors the rack position feedback from the road wheel actuator and uses this information to determine when to execute driver mode changes. The feedback mechanism ensures that mode changes only occur when the steering system is in an appropriate state (rack at center position), preventing unwanted torque changes and maintaining steering feel consistency.
2Adaptability or versatility
If driver mode is changed when torsion bar torque becomes 0 Nm like general-purpose steering system, then driver mode switching is achieved, but target rack position changes affecting vehicle behavior and creating steering different from driver's intention
Solution Approach 1:
The controller checks the rack position in advance before allowing driver mode changes. By requiring the rack to be at a specific position (centered state) before executing mode switching, the system ensures that the steering system is in a neutral state where mode changes won't cause unintended rack position changes. This preliminary verification maintains steering accuracy and ensures the steering matches the driver's intention.
3Ease of operation
If driver mode change is allowed at any rack position, then driver mode switching flexibility is improved, but steering behavior becomes inconsistent with driver's intention
Solution Approach 1:
The controller performs a preliminary check of the rack position before allowing driver mode changes. By restricting mode changes to occur only when the rack is at the center position, the system maintains steering consistency and ensures that mode switching doesn't create unintended steering behavior. This condition-based approach balances operational flexibility with steering reliability.
Data Source
AI summary
According to an embodiment of the present disclosure, a steering control apparatus of a steer by wire (SbW) system including a steer wheel feedback actuator (SFA) and a road wheel actuator (RWA) includes a communicator configured to receive a driver mode change command, information on a rack position of the RWA, and information on a torsion bar torque of the SFA, a determiner configured to determine whether to change a driver mode based on the driver mode change command and the information on the rack position and to generate a driver mode change signal based on the determined result, and a controller configured to control output torque for the SFA based on the driver mode change signal, information on a current torsion bar torque, and information on a target torsion bar torque of a target driver mode.