Steer-by-Wire Steering Reaction Force Control
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Solution Overview
Problem
Steer-by-wire steering systems often cause driver discomfort due to the steered wheels' inability to follow sharp steering angles, especially under varying road conditions and motor performance limitations.
Innovation Solution
A steer-by-wire steering system that includes a steering-side motor to supply a steering reaction force and a steered-side motor to steer the wheels, with a power supply control circuit that adjusts the duty ratio of the steered-side motor's power supply to increase the steering reaction force when the steered angle cannot follow the steering angle, enhancing followability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the steered-side motor operates at high power to enable sharp steering angle changes, then the steering response speed improves, but the motor performance limitations and road surface conditions cause the steered angle to become unable to follow the steering angle, making the driver feel discomfort
Solution Approach 1:
The system monitors the duty ratio of the steered-side motor as a feedback parameter to detect when the motor is operating at its performance limit. When the duty ratio reaches a predetermined threshold, the system recognizes that the steered angle cannot follow the steering angle properly, and responds by adjusting the steering reaction force to improve followability and reduce driver discomfort.
Solution Approach 2:
The system dynamically changes the steering reaction force parameter based on the operating conditions. By adjusting the magnitude of the steering reaction force according to the duty ratio level, the system optimizes the balance between steering responsiveness and followability under different operating conditions.
2Reliability
If the steering reaction force is increased to improve followability during sharp steering operations, then the steered angle can better follow the steering angle, but this requires additional control complexity to determine when to apply the increased reaction force
Solution Approach 1:
The control system uses the duty ratio of the steered-side motor as a simple feedback parameter to determine when increased steering reaction force is needed. This feedback mechanism provides a straightforward way to detect motor performance limits and trigger appropriate control actions without requiring complex sensing or calculation systems.
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
This solution reduces the likelihood of driver discomfort by improving the steered wheels' ability to follow steering angles, regardless of motor performance, by increasing the steering reaction force when the steered angle lags, thus addressing the issue of sharp steering operations and road conditions.
Implementation Method 1
a steering-side motor that supplies the steering input device with a steering reaction force that opposes the steering input to the steering input device by a driver
Implementation Method 2
a steered-side motor that supplies the steering operation device with a steering force that causes the steered wheel to be steered
Data Source
AI summary
The steer-by-wire steering system comprise a steering input device and a steering operation device that steers wheels which are mechanically coupleable. The steering input device includes a steering-side motor that supplies a steering shaft with a steering reaction force, the steering operation device includes a steered-side motor that supplies a rack shaft with a steering force, and a power supply control circuit that controls the steering-side motor to generate the steering reaction force and that controls the steered-side motor to generate the steering force. When the duty ratio of a duty signal that is generated to control the power supply to the steered-side motor reaches a setting value that is defined to indicate that a steered angle becomes unable to follow a steering angle, the power supply control circuit controls the power supply to the steering-side motor such that the steering-side motor increases the steering reaction force.