Steering Control Device Torque Feedback Optimization
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Solution Overview
Problem
Steering control devices for steer-by-wire systems face challenges in optimizing steering properties, particularly in transferring road surface information to drivers through mechanical separation of steering and steered components, leading to suboptimal steering torque and angle relationships.
Innovation Solution
A steering control device with a control circuit that computes torque command values, input torque fundamental components, and target steering angles to apply appropriate steering reaction forces, incorporating grip state and vehicle speed considerations to optimize steering properties and enhance steering feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steering and steered portions are mechanically separated in a steer-by-wire system, then steering control flexibility and safety are improved, but the natural transfer of road surface reaction force to the driver is lost, degrading steering feel
Solution Approach 1:
A reaction force generation device acts as an intermediary between the steered portion and the driver. This device generates artificial reaction forces based on detected steered wheel angles and vehicle states, simulating the natural road surface feedback that would otherwise be mechanically transmitted through direct connection. The intermediary reproduces the missing sensory feedback electronically and mechanically.
Solution Approach 2:
The patent replaces the direct mechanical connection for force transmission with an electronic control system. Sensors detect steering operations and vehicle states, processors compute appropriate reaction forces, and actuators generate these forces. This substitution allows flexible, adaptive reaction force generation while maintaining steering safety, replacing rigid mechanical force transfer with intelligent electronic control.
2Adaptability or versatility
If steering reaction force is applied through a steering-side actuator, then steering properties can be controlled, but the complexity of the control system increases
Solution Approach 1:
The patent merges the steering reaction force control with the overall steering control architecture. The reaction force generation device is integrated with the steering control unit, sharing sensors, processors, and control algorithms. This consolidation reduces system complexity compared to having separate independent control systems, while maintaining full adaptability for optimizing steering properties under various driving conditions.
Solution Approach 2:
The steering control system performs multiple functions: detecting steering operations, controlling steered wheel angles, generating reaction forces, and adapting to different driving conditions. By designing a universal control architecture that handles all these functions, the patent avoids the complexity of multiple specialized systems, achieving versatile steering property control through a unified multi-functional platform.
3Force
If torque command value computation is performed based on drive torque, then steering torque can be optimized, but precise control of steering angle becomes more difficult
Solution Approach 1:
The patent employs feedback control where the actual steering angle is continuously detected and compared with the target steering angle. The steering control unit adjusts the steered portion based on this feedback to minimize angle errors. Additionally, feedback from the reaction force generation ensures that torque application does not deviate the steering angle from the intended trajectory, maintaining precise angular control despite torque optimization efforts.
Solution Approach 2:
The system dynamically changes control parameters including torque command values, target steering angles, and reaction force magnitudes based on detected driving conditions. By adaptively adjusting these parameters in real-time, the patent optimizes steering torque for comfort and control while simultaneously maintaining precise steering angle accuracy through coordinated parameter modification rather than fixed control relationships.
Data Source
AI summary
An input torque fundamental component computation circuit includes: a torque command value computation circuit that computes a torque command value corresponding to a target value for steering torque that is to be input by a driver for drive torque obtained by adding the steering torque to an input torque fundamental component; and a torque F/B control circuit that computes the input torque fundamental component through execution of torque feedback control for causing the steering torque to follow the torque command value. A target steering angle computation circuit computes a target steering angle on the basis of the input torque fundamental component. A steering-side control circuit computes target reaction force torque on the basis of execution of angle feedback control for causing a steering angle to follow a target steering angle. The torque command value computation circuit computes the torque command value in consideration of the grip state amount.