Steering System Manual-Autonomous Transition Control
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Solution Overview
Problem
In steer-by-wire systems, the driver's intention is not immediately reflected in the target steered angle during autonomous steering control until the steering torque or operation angle reaches specific threshold values, leading to a delay in reflecting driver input.
Innovation Solution
A steering system with a reaction force motor and a steering motor, equipped with sensors and ECUs that calculate and control command values to immediately reflect the driver's intention by adding manual steering angle command values to autonomous steering angle command values, allowing seamless transition between manual and autonomous steering control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the automatic following system multiplies the target steered angle by a predetermined value larger than 1 when steering torque or operation angle reaches threshold values, then the system can switch between manual and autonomous steering control, but the driver's intention is not immediately reflected in the target steered angle during autonomous steering control
Solution Approach 1:
The reaction force ECU preliminarily calculates a manual steering angle command value based on steering torque detected by the steering torque sensor. This manual steering angle command value is added to the autonomous steering angle command value to generate the final target steered angle, ensuring the driver's intention is immediately reflected without waiting for threshold conditions to be met
Solution Approach 2:
The system merges the manual steering angle command value (calculated from steering torque) with the autonomous steering angle command value by addition. This combination ensures both the driver's immediate intention and the autonomous system's target are integrated into the final target steered angle, eliminating delay in reflecting driver input
2Reliability
If the system waits for steering torque or operation angle to reach threshold values before switching control modes, then control switching can be managed, but the driver's intention cannot be immediately reflected in the steering motor and reaction force motor
Solution Approach 1:
The steering torque sensor continuously provides feedback on the steering torque applied by the driver. The reaction force ECU uses this real-time feedback to calculate the manual steering angle command value, which is immediately combined with the autonomous steering angle command value, ensuring the driver's intention is instantly reflected in the target steered angle while maintaining reliable control switching
Solution Approach 2:
The system preliminarily processes the steering torque signal through the steering torque sensor and calculates the manual steering angle command value in advance, before it needs to be combined with the autonomous steering angle command value. This preliminary action ensures immediate reflection of driver intention without compromising control switching reliability
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
Enables immediate reflection of the driver's intention in the steering motor and reaction force motor during autonomous steering, facilitating cooperative control for smooth manual and autonomous steering transitions without discomfort to the driver.
Implementation Method 1
a steering torque sensor configured to detect steering torque applied to the steering member
Implementation Method 2
a reaction force motor configured to apply reaction torque to the steering member
Implementation Method 3
a steering motor configured to drive the steering operation mechanism
Data Source
Figure 1
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AI summary
A steering system (1; 1A) includes: a steering member (2); a steering operation mechanism (4; 4R, 4L); a reaction force motor (13); a steering motor (19; 19R, 19L); a steering torque sensor (11); a command value setting circuit (41); a reaction force command value calculation circuit (44) configured to calculate a reaction force command value; a steering operation command value calculation circuit (81; 81R, 81L) configured to calculate a steering operation command value based on a steering operation steering angle command value and a manual steering angle command value; a reaction force control circuit (45) configured to cause a rotation angle of the reaction force motor to follow the reaction force command value; and a steered angle control circuit (82; 82R, 82L) configured to cause a rotation angle of the steering motor to follow the steering operation command value.