Steering Control Apparatus Rack Axial Force Compensation
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Solution Overview
Problem
The existing steering control systems face challenges in accurately controlling the steered angle of vehicle wheels due to the elastic support of the steering gearbox on the vehicle body, leading to errors in steering angle control and potential impact during large steering operations.
Innovation Solution
A steering control apparatus that includes a target value setting processing circuit, an axial-force acquisition processing circuit, and a correction processing circuit to adjust the relative displacement of the rack shaft based on the acquired rack axial force, thereby mitigating the adverse effects of the elastic support and improving steering control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the steering gearbox is elastically supported on the vehicle body using rubber mount bushes, then impact during large steering operations is reduced, but the steering gearbox may be displaced relative to the vehicle body in the axial direction due to elasticity of the mount bushes, causing error in control of the steered angle
Solution Approach 1:
The control device measures the actual relative displacement between the rack shaft and vehicle body using sensors, compares it with the target displacement, and adjusts the steering operation actuator to compensate for the discrepancy caused by elastic deformation of mount bushes, thereby maintaining accurate steered angle control
Solution Approach 2:
A regulation member is introduced as an intermediary component between the rack shaft and the steering gearbox. This regulation member can be firmly fixed to the vehicle body, providing a stable reference point that eliminates the influence of elastic deformation of mount bushes on the relative displacement measurement
2Measurement precision
If the steering gearbox is firmly fixed directly to the vehicle body without using rubber mount bushes, then error in control of the steered angle is suppressed, but impact is likely to be transmitted to the vehicle when steered wheels are steered through a large angle
Solution Approach 1:
The mounting system is segmented into two functional parts: a regulation member that is firmly fixed to the vehicle body to provide a stable reference for displacement measurement, and a steering gearbox that is elastically supported by rubber mount bushes to reduce impact transmission. This segmentation allows each part to fulfill its specific function without compromising the other
3Device complexity
If the relative displacement of the rack shaft relative to the steering gearbox is controlled to achieve target steered angle, then steering operation control is simplified, but the displacement of the steering gearbox relative to the vehicle body creates a difference that acts as an error in control
Solution Approach 1:
The control system transitions from purely mechanical displacement control to an electromechanical system that uses sensors to detect actual displacement and electronic control to adjust the steering operation actuator. This substitution enables real-time compensation for elastic deformation while maintaining relatively simple control logic
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
The system effectively corrects the target value for relative displacement to reduce errors in steering angle control and minimize impact on the vehicle body, enhancing controllability and reducing unintended forces on the steering wheel.
Implementation Method 1
the steering gearbox is elastically supported on the vehicle body by forming mounting holes in the steering gearbox at a plurality of positions, fitting mount bushes in the mounting holes
Data Source
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AI summary
A steering control apparatus is provided which allows mitigation of an adverse effect of a technique for fixing a regulation member to a vehicle body on a phenomenon resulting from execution of steering operation control on steered wheels. An axial-force acquisition processing circuit M42 calculates a rack axial force AF based on currents iu, iv, and iw flowing through a steering operation motor. A correction processing circuit M40 corrects a target steered angle θp1* based on the rack axial force AF to obtain a target steered angle θp*. A steered angle control processing circuit M36 calculates a torque command value Trqt* as the amount of operation for adjusting a steered angle θp to the target steered angle θp* through feedback control. An operation signal generation processing circuit M38 controllably adjusts a torque of a steering operation motor to the torque command value Trqt*.