Vehicle Steering System Anti-Drift Control via Integrated Torque
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Solution Overview
Problem
Existing vehicle steering systems fail to reduce the physical burden on drivers when navigating cant roads or crosswinds, as they do not effectively assist in maintaining a straight course, leading to impaired comfort and increased steering effort.
Innovation Solution
A vehicle steering system equipped with an electric motor, steering torque and angle detectors, and a control device that calculates an integrated torque value to apply assistive torque, performing anti-unidirectional drift control by compensating for vehicle drift based on mapping information, thereby reducing driver effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a dead zone control is applied across the neutral point for steering torque, then the system avoids unnecessary assist torque generation during normal steering, but it fails to reduce driver burden when the vehicle drifts unidirectionally on cant roads or in crosswinds
Solution Approach 1:
The integrating unit performs preliminary integration of steering torque to calculate an integrated torque value that represents cumulative drift tendency. This preliminary action enables the system to anticipate and compensate for unidirectional drift before it becomes a significant stability issue, allowing assist torque to be generated proactively during drift conditions while maintaining dead zone functionality during normal steering.
Solution Approach 2:
The integrated torque value acts as an intermediary parameter that bridges the gap between instantaneous steering torque and cumulative drift behavior. By using this intermediate integrated value rather than raw steering torque alone, the system can distinguish between normal steering fluctuations (within dead zone) and genuine unidirectional drift patterns, enabling selective assist torque generation that improves both comfort and reliability.
2Measurement precision
If assist torque is generated only when steering torque falls outside the dead zone, then the system maintains steering precision during normal operation, but it impairs comfort by failing to assist during unidirectional drift conditions
Solution Approach 1:
The integrating unit continuously integrates steering torque over time to maintain an updated integrated torque value, ensuring that drift compensation is available continuously during unidirectional drift conditions rather than intermittently. This continuous action allows the system to maintain steering comfort throughout the duration of drift events while preserving precise torque detection accuracy during normal operation when the integrated value remains near zero.
3Reliability
If the system continuously monitors steering torque to detect unidirectional drift, then it can provide timely compensation, but it increases computational load and system complexity
Solution Approach 1:
The integrating unit automatically performs cumulative torque integration without requiring external intervention or complex algorithms. This self-service approach to drift detection uses a simple but effective mathematical operation that continuously updates the integrated torque value based on incoming steering torque data, achieving reliable drift detection while minimizing computational complexity and avoiding the need for sophisticated pattern recognition systems.
Data Source
AI summary
A vehicle steering system can keep the comfort of steering feeling for a driver, even in a situation, such as traveling on a cant road or in a crosswind, where a unidirectional-drift behavior of a vehicle occurs, and includes an electric motor, a steering angle sensor, a steering torque sensor, and an EPS_ECU that controls driving power of the electric motor, when the vehicle is traveling straight, based on vehicle information including a steering torque and a steering angle, to perform a control for applying an assist torque to a steering system. The EPS_ECU includes an integrating unit for calculating an integrated torque value obtained by integrating the steering torque, and a steering effort assist controlling unit for performing an anti-unidirectional-drift control over the driving power of the electric motor, when the integrated torque value exceeds the threshold value, so as to cancel the unidirectional-drift behavior of the vehicle.