Power Steering Torque Compensation for Braking Trajectory Deviation
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Solution Overview
Problem
Motor vehicles experience course deviations during braking due to asymmetrical braking capacities, undercarriage geometry variations, and uneven mass distribution, leading to driver discomfort and insecurity, especially during emergency braking at high speeds.
Innovation Solution
A method for the power steering system that calculates a raw correction torque based on vehicle speed, yaw rate, and steering force to compensate for course deviations, using internal and external vehicle signals, and applies a safe correction torque to resist deviation, without adding equipment, by filtering and weighting the torques to avoid amplification and ensure driver safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the power steering system applies motor torque to assist steering during braking, then the driver's steering effort is reduced, but the course deviation caused by braking asymmetry is amplified
Solution Approach 1:
The power steering system applies a preliminary counteracting torque in the opposite direction of the detected course deviation before the deviation fully manifests. The calculator detects yaw rate changes indicating deviation and applies motor torque to counteract the asymmetrical braking force, preventing the deviation from amplifying while maintaining reduced steering effort for the driver.
Solution Approach 2:
The system continuously monitors yaw rate signals from the vehicle's sensor network to detect course deviation during braking. The calculator processes this feedback information and dynamically adjusts the motor torque output to compensate for the detected deviation, creating a closed-loop control system that maintains steering accuracy while preserving power steering assist functionality.
2Reliability
If the power steering system applies strong correction torque to counteract course deviation, then steering accuracy is improved, but the driver experiences unnatural steering feel and additional stress
Solution Approach 1:
The power steering system applies only the necessary portion of correction torque to counteract course deviation, rather than fully compensating for it. The calculator modulates the motor torque to provide just enough counteracting force to maintain steering accuracy during braking, avoiding excessive correction that would create unnatural steering feel or additional driver stress.
3Measurement precision
If the power steering system uses additional sensors to detect course deviation, then compensation precision is improved, but the system complexity and cost increase
Solution Approach 1:
The system utilizes the vehicle's existing yaw rate sensor, which serves multiple functions including stability control and course deviation detection. The calculator processes the yaw rate signal to detect course deviation during braking, eliminating the need for dedicated deviation detection sensors. This multi-functional use of existing sensors maintains compensation precision while avoiding increased system complexity and cost.
Data Source
AI summary
A method for a power steering system of a motor vehicle delivering, to the steering, a torque controlled by a computer for compensating for trajectory deviation of the vehicle when this vehicle is braking, which, from a request to activate the method while braking, in a first step, calculates a rough correction torque taking into account the speed of the vehicle, the yaw of this vehicle, and a signal representing the force applied by the steering to the steered wheels.