Steering Reaction Torque Control for Low-Torque Wheel Stability
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Solution Overview
Problem
In steer-by-wire steering systems, the steering wheel may rotate under the influence of reaction force torque when the driver's operation torque input is low, leading to discomfort due to varying reaction force torque depending on turning motor operation restrictions.
Innovation Solution
A steering control device and method that calculates and applies a deviation-compensating reaction force torque, switching between calculation states based on driver operation conditions, including torque, positional deviation, and motor operation status, to mitigate discomfort by inferring the likelihood of wheel movement under reaction force torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reaction force torque is increased to compensate for positional deviation when the turning motor is restricted, then the positional accuracy is improved, but the steering wheel may rotate unexpectedly when the driver's operation torque is low
Solution Approach 1:
The system dynamically switches between two calculation states for the deviation-compensating component based on operating conditions. In the first calculation state (normal operation), a standard compensation value is used. In the second calculation state (when turning motor operation is restricted), a larger compensation value is calculated. This dynamic adaptation allows the system to optimize positional accuracy when needed while maintaining steering wheel stability during normal operation.
Solution Approach 2:
The system changes the parameter of the deviation-compensating component based on the operational state of the turning motor. When the turning motor is restricted, the parameter (compensation magnitude) is increased to maintain positional accuracy. When operation is normal, the parameter is reduced to prevent unwanted steering wheel rotation. This parameter adjustment resolves the contradiction between accuracy and stability.
2Measurement precision
If the reaction force torque varies depending on turning motor operation restrictions, then the positional deviation compensation is improved, but the driver experiences discomfort due to varying steering feel
Solution Approach 1:
The system dynamically adjusts the reaction force torque based on the operational state of the turning motor. When the turning motor is restricted, the system switches to the second calculation state and applies a larger deviation-compensating component to maintain positional accuracy. When operation is normal, it uses the first calculation state with standard compensation. This dynamic switching ensures accurate positioning while minimizing driver discomfort by only applying enhanced compensation when necessary.
Solution Approach 2:
The system continuously monitors the operational state of the turning motor and adjusts the reaction force torque accordingly. By detecting whether the turning motor is restricted or operating normally, the system provides feedback-based adjustment of the deviation-compensating component. This feedback mechanism ensures that positional deviation is compensated accurately when needed while maintaining smooth steering feel during normal operation, thereby reducing driver discomfort.
3Measurement precision
If a larger deviation-compensating component is calculated when the turning motor is restricted, then the positional accuracy is improved, but the steering wheel may rotate under low driver operation torque
Solution Approach 1:
The system dynamically selects between two calculation states based on the turning motor's operational status. In the first calculation state (normal operation), a standard deviation-compensating component is applied. In the second calculation state (motor restriction), a larger compensation component is calculated. This dynamic selection allows the system to achieve high positional accuracy when the motor is restricted while maintaining appropriate steering resistance during normal operation.
Solution Approach 2:
The system changes the parameter of the deviation-compensating component based on the operational state. When the turning motor is restricted, the parameter is increased to improve positional accuracy. When operation is normal, the parameter is kept at a standard level to maintain appropriate steering wheel rotation resistance. This parameter change strategy resolves the contradiction between achieving high accuracy and maintaining sufficient rotation resistance.
Data Source
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AI summary
A steering control device (1) includes a processor configured to execute a reaction force control process. The reaction force control process includes a reaction force torque calculation process of calculating a reaction force torque operation amount. The reaction force torque calculation process includes a deviation compensation calculation process of calculating a deviation-compensating component. The deviation compensation calculation process includes a process of calculating a positional deviation, a process of calculating the deviation-compensating component based on the positional deviation, and a process of switching among a plurality of calculation states for calculating the deviation-compensating component. The process of switching among the calculation states is a process of permitting switching among the calculation states on the condition that a permission condition is met. The permission condition is met based on an operation amount that varies in association with a driver's operation of an operation member.