Steering Assist Control for LSD Torque Steer Compensation
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Solution Overview
Problem
Conventional steering force control systems with limited slip differential gears face challenges in determining the necessary steering assisting force to counteract torque steer and steering reaction forces, especially during starting up from a standstill or accelerating on unstable road surfaces, leading to vehicle instability and discomfort for the driver.
Innovation Solution
A steering force control system that includes a steering assist control mechanism using proportional and integration control to calculate and apply an additional torque to counteract steering reaction forces, utilizing wheel speed detection and limited slip differential gear inhibiting torque, while also considering single wheel spin conditions and vehicle speed to optimize steering assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the inhibiting force of the LSD is increased to improve rough-terrain traversability, then the rough-terrain traversability is improved, but the steering wheel pulls excessively and the steering force control system cannot determine the necessary steering assisting force
Solution Approach 1:
The steering assist control means uses feedback from wheel speed detection means to detect wheel speed differences between left and right steered wheels. This feedback mechanism allows the system to dynamically adjust the steering assisting force based on the actual differential action of the LSD, enabling accurate compensation even when the inhibiting force is large. The feedback loop includes detecting wheel speeds, calculating wheel speed differences, and adjusting steering assist accordingly.
Solution Approach 2:
The system changes the parameter of steering assisting force dynamically based on wheel speed differences. When the wheel speed difference exceeds a threshold indicating LSD actuation, the system calculates and applies an additional steering assisting force proportional to the wheel speed difference. This parameter change allows the steering system to adapt to varying LSD inhibiting forces and maintain proper steering control.
2Power
If the multiplate clutch transmits torque from fast rotation to slow rotation, then torque transmission is achieved, but the direction of torque transmission becomes unknown when wheels are connected directly
Solution Approach 1:
The wheel speed detection means provides continuous feedback on the rotational speeds of left and right steered wheels. By comparing these speeds, the system can determine the direction of wheel speed difference and thus infer the direction of torque transmission through the LSD. This feedback allows the steering assist control means to apply steering assisting force in the correct direction even when torque transmission direction is not directly observable.
Solution Approach 2:
The wheel speed difference acts as an intermediary parameter that reveals the torque transmission direction. Instead of directly measuring torque direction, the system uses wheel speed differences as a mediator to infer the direction of torque flow through the LSD. This intermediary measurement allows indirect detection of torque transmission direction without requiring direct torque sensors.
3Device complexity
If conventional steering force control is used with LSD, then the system structure is simple, but vehicle stability deteriorates during starting up from standstill or accelerating on unstable road surfaces
Solution Approach 1:
The system incorporates wheel speed detection means that continuously monitors the rotational speeds of left and right steered wheels. This feedback allows the steering assist control means to detect when wheel speed differences indicate LSD actuation during unstable conditions such as starting from standstill or accelerating on slippery surfaces. The system then applies appropriate steering assisting force to maintain vehicle stability.
Solution Approach 2:
The steering assist control means calculates and applies additional steering assisting force in advance when wheel speed differences indicate impending LSD actuation. This preliminary action prevents excessive steering wheel pull and maintains vehicle stability before the torque steer effect fully develops, particularly during critical phases like starting from standstill or accelerating on unstable road surfaces.
Data Source
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AI summary
A steering force control system includes a steering means for changing directions of pair of left and right wheels in response to control by a driver of a vehicle, a steering toque detection means for detecting a steering torque when the steering means is controlled, a steering assist means for applying a steering assisting force to the control of the steering means, wheel speed detection means for detecting wheel speeds of the pair of left and right wheels. An additional torque calculation means calculates an additional torque which is sufficient to suppress an occurrence of a steering wheel pulling phenomenon when a limited slip differential gear for applying an inhibiting torque which is a differential limiting force between the pair of left and right wheels is actuated through proportional control and integration control of a steering torque detected by the steering torque sensor and a basic assisting torque which is determined based on a steering assisting force control performed by the steering assist means. A steering assist control means controls the steering assist means so that an additional torque calculated by the additional torque calculation means refers to the steering assisting force.