Variable Steering Ratio Control for Torque Steer Compensation
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Solution Overview
Problem
Existing steering systems in heavy vehicles with high-power engines face challenges in reducing torque steer-induced steering-wheel pull while maintaining acceleration performance, as electric power steering devices are unsuitable due to limited voltage and increased weight, and conventional braking/driving force control systems compromise acceleration by limiting engine power.
Innovation Solution
A steering ratio control system that includes a variable steering ratio mechanism, a braking/driving force control unit, and a steering ratio control unit to individually adjust steering ratios and forces between wheels, calculating a correction value to cancel torque steer and enhance acceleration performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If electric power steering devices are used to compensate for torque steer, then steering-wheel pull is reduced, but device weight and size increase
Solution Approach 1:
The patent replaces the electric power steering system with a hydraulic power steering system that incorporates a variable steering ratio mechanism. This mechanical/hydraulic substitution eliminates the need for electric motors and complex electronic control systems, thereby reducing device weight and size while maintaining torque steer compensation capability through hydraulic assistance and variable gear ratio adjustment.
Solution Approach 2:
The patent employs a variable steering ratio mechanism that dynamically adjusts the gear ratio between the steering wheel and road wheels. By changing the steering ratio parameter in response to driving conditions and torque steer magnitude, the system achieves effective torque steer compensation without requiring a large electric motor, thus reducing overall system weight.
2Object-affected harmful factors
If braking/driving force control systems limit engine power output to avoid excessive torque steer, then torque steer is reduced, but acceleration performance deteriorates
Solution Approach 1:
The patent implements a dynamic steering ratio adjustment mechanism that continuously varies the steering ratio based on real-time driving conditions, including vehicle speed, steering angle, and detected torque steer. This dynamic adaptation allows the system to maintain optimal steering characteristics across different acceleration scenarios without requiring power output limitations.
Solution Approach 2:
The system changes the steering ratio parameter dynamically to compensate for torque steer while maintaining full engine power output. By adjusting the mechanical steering ratio rather than limiting power, the system achieves torque steer reduction without sacrificing acceleration performance.
Data Source
AI summary
A steering ratio control system of a vehicle includes a variable steering ratio mechanism variably adjusting a steering ratio of a steer angle at left and right steered road wheels to a steering-wheel rotation angle, and a braking/driving force control unit individually controlling braking force and/or driving force of the left and right steered wheels. A steering ratio control unit determines a reference steering ratio based on a vehicle's driving state. The steering ratio control unit calculates a steering-ratio correction value needed for canceling torque steer resulting from a difference in braking force and/or driving force between the left and right steered wheels. A final steering ratio is determined based on both of the reference steering ratio and the steering-ratio correction value to drive the variable steering ratio mechanism responsively to the final steering ratio reflecting the steering-ratio correction value.