Steer-by-wire reaction torque generation with duplex motors
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Solution Overview
Problem
Existing steer-by-wire systems fail to flexibly generate reaction torque when the reaction torque motor fails, affecting the driver's ability to accurately control the steering wheel, as they rely on mechanisms like short-circuiting or rotary dampers that do not allow for controlled torque adjustment.
Innovation Solution
A steer-by-wire system with a duplex configuration of reaction torque motors, where each system can generate reaction torque independently, allowing the control device to adjust the torque characteristics in response to steering wheel operations, even in the event of single or dual system failures, ensuring consistent and recognizable feedback to the driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single reaction torque motor is used, then the device complexity is reduced, but the reliability decreases when the motor fails
Solution Approach 1:
The reaction torque generation device is segmented into a first reaction torque motor and a second reaction torque motor, allowing the system to divide the torque generation function across multiple independent components. This segmentation enables backup capability where the second motor can compensate when the first motor fails, thereby improving reliability without requiring a completely redundant complex system.
Solution Approach 2:
The control device is configured to detect failure of the first reaction torque motor in advance and preliminarily switch to using the second reaction torque motor before complete failure occurs. This preliminary action ensures continuous reaction torque generation by pre-establishing the backup mechanism, maintaining reliability while managing device complexity through intelligent control.
2Reliability
If a rotary damper is used as backup, then the reliability improves, but the ease of operation deteriorates due to fixed viscosity feeling
Solution Approach 1:
The control device dynamically adjusts the reaction torque characteristics by controlling the second reaction torque motor based on the operation state of the steering wheel. Unlike a fixed rotary damper, the motorized system can adaptively change torque output, providing optimal steering feel across different operating conditions while maintaining reliability through the backup motor capability.
Solution Approach 2:
The system changes the operational parameters of the second reaction torque motor based on steering wheel operation detection. When the steering wheel is being operated, the control device adjusts the motor's torque output parameters to provide appropriate reaction torque, ensuring ease of operation. This parameter adaptation allows the system to maintain both reliability and operational ease, overcoming the fixed characteristic limitation of rotary dampers.
3Reliability
If short-circuiting is used to secure reaction torque, then the reliability improves, but the ease of operation worsens due to insufficient torque control
Solution Approach 1:
The control device implements feedback control by detecting the operation state of the steering wheel and adjusting the second reaction torque motor's output accordingly. This feedback mechanism ensures that the reaction torque is precisely controlled to match driver intentions, maintaining both reliability through backup torque generation and ease of operation through adaptive torque adjustment based on real-time steering input.
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 maintains the ability to generate desired reaction torque characteristics, enhancing driver confidence and control by allowing flexible adjustment of torque in case of system failures, providing a recognizable and moderate feeling of resistance, thus improving operability even during failures.
Implementation Method 1
a reaction torque motor configured to apply a reaction torque to the steering wheel
Data Source
AI summary
A steer-by-wire system includes a steering reaction torque generation device mechanically separated from a turning device for turning wheels and configured to apply a reaction torque to a steering wheel. The steering reaction torque generation device has a duplex configuration including a first system and a second system, each system including a reaction torque motor. When both systems are normal, a control device generates the reaction torque having a normal characteristic by controlling an operation of the reaction torque motor of at least one system. In a case of single failure where one of the systems fails, the control device generates the reaction torque having a first characteristic by controlling an operation of the reaction torque motor of another of the systems. The reaction torque having the first characteristic is different from the reaction torque having the normal characteristic with respect to a same steering angle.