Steering Rack Force Reduction via Vehicle Motion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Autonomous vehicle steering systems face performance issues when the expected turning radius cannot be achieved, leading to diminished steering capabilities, especially when stationary and under high steering loads, which can render certain maneuvers impossible.
Innovation Solution
A computing device is programmed to determine the required and available rack force for the steering system, initiating vehicle movement and activating the actuator when the available force is insufficient, and using vehicle motion to supplement the steering actuator in a diminished mode, allowing for reduced torque operation and torque vectoring to aid in low-speed maneuvers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the vehicle is stationary and the steering actuator operates under high steering loads, then the steering system should provide sufficient torque to achieve the expected turning radius, but the actuator may be unable to generate enough force to overcome static friction and achieve the required steering maneuver
Solution Approach 1:
The system transitions the vehicle from a static state to a moving state to dynamically change the steering conditions. By inducing vehicle motion, the steering rack force requirements are reduced due to decreased tire scrubbing and static friction, enabling the diminished actuator to achieve the necessary steering maneuvers that would be impossible in a stationary condition.
Solution Approach 2:
The system changes the vehicle's operational parameters by modulating speed and inducing motion. This parameter change transforms the steering problem from a high-force static condition to a lower-force dynamic condition, where the actuator's limited torque becomes sufficient to achieve the required steering rack force for the maneuver.
2Force
If the vehicle initiates movement to supplement the steering actuator, then the required steering force is reduced through decreased tire scrubbing, but the maneuver requires additional time and speed modulation
Solution Approach 1:
The system employs periodic or intermittent vehicle motion rather than continuous movement. The vehicle is moved forward or backward in controlled increments to achieve the necessary steering rack force reduction, then the motion is paused while the actuator completes the steering maneuver. This periodic action reduces the overall time compared to attempting a stationary maneuver that would fail, while minimizing unnecessary movement time.
3Adaptability or versatility
If the steering system operates in a diminished mode with reduced actuator torque, then certain steering maneuvers become impossible when stationary, but the system can maintain operational capability by coordinating vehicle motion with steering actuation
Solution Approach 1:
The system merges the vehicle motion control function with the steering control function. By coordinating the propulsion system and steering actuator through a unified control algorithm, the system achieves enhanced maneuver capability in diminished mode. The control system integrates speed modulation, direction control, and steering actuation into a single coordinated operation, enabling maneuvers that would be impossible with the actuator alone.
Solution Approach 2:
The vehicle's propulsion system is utilized for dual purposes: both for forward movement during normal operation and for supplementing the steering actuator during diminished mode maneuvers. This multi-functionality allows the same hardware components to serve multiple functions, reducing the need for additional specialized equipment while expanding the system's operational capabilities in reduced-torque conditions.
Data Source
AI summary
Controlling a vehicle steering system includes determining a rack position of a rack needed to execute a maneuver. A minimum velocity allowing the desired steering angle to be reached is determined. The velocity of the vehicle is increased to the determined minimum velocity. The rack is moved to the rack position needed.