Steering Rack Blending for Split-Friction Chassis Control
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Solution Overview
Problem
Existing vehicle steering systems struggle to stabilize vehicles under split road friction conditions, where tires on different surfaces cause unintentional yaw moments, leading to uncontrolled vehicle turning, and driver inputs are often ignored due to disconnected handwheel actuators.
Innovation Solution
A coordinated chassis control system that integrates brake controllers with steering systems to manage rack position commands, incorporating driver intent through blending algorithms using high and low pass filters to stabilize the vehicle while honoring driver inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If brake controller intervenes to stabilize vehicle under split road friction conditions, then vehicle stability is improved, but driver input responsiveness deteriorates
Solution Approach 1:
The controller acts as an intermediary between the brake controller and handwheel actuator, receiving rack position commands from both sources and blending them through a blending algorithm. This mediator role allows the system to honor driver inputs while incorporating stability corrections, resolving the contradiction between vehicle stability and driver input responsiveness
Solution Approach 2:
The system dynamically adjusts the blending ratio between brake controller commands and driver input commands based on detected road conditions. Under split road friction conditions, the controller increases the weight of brake controller commands while maintaining responsiveness to driver inputs, allowing adaptive optimization of both stability and driver control
2Stability of the object's composition
If handwheel actuator is disconnected to prevent unintentional turning, then vehicle control stability is improved, but driver intent recognition deteriorates
Solution Approach 1:
The system replaces the mechanical connection between handwheel actuator and rack with an electronic control architecture. The controller receives electronic commands from both the handwheel actuator and brake controller, processes them through a blending algorithm, and generates the final rack position command. This substitution allows simultaneous access to both driver inputs and stability commands without mechanical interference
Solution Approach 2:
The controller continuously monitors commands from both the handwheel actuator and brake controller, processes feedback about road conditions and vehicle state, and dynamically adjusts the blending ratio. This feedback mechanism ensures that driver intent is continuously recognized and incorporated while maintaining vehicle control stability under split road friction conditions
Data Source
AI summary
A method for coordinated chassis control under a split road friction condition includes receiving, in response to a detected split road friction condition, a first rack position command from a brake controller of a vehicle. The method also includes receiving a second rack position command from a handwheel actuator, estimating a driver torque value based on the second rack position command, determining a driver intent value based on the driver torque value, and generating a blended rack position command based on the first rack position command and the driver intent value. The method also includes selectively controlling rack position of a rack associated with a steering system of the vehicle based on the blended rack position command, the first rack position command, and the second rack position command.