Power Steering Control Arbitration for Stable Manual and Autonomous Modes
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Solution Overview
Problem
Existing electromechanical power steering mechanisms for motor vehicles face challenges in achieving optimal steering feel during both manual and autonomous driving modes due to oscillations caused by parallel operation of position and torque controllers, which reduces performance.
Innovation Solution
A motor vehicle power steering mechanism with a steering controller that includes a steering column reference controller, an arbitration unit, and a column torque controller, where the arbitration unit weights and adds reference steering column torques calculated for position and torque control modes to eliminate parallel connection, improving steering feel by connecting these controllers in series.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If position controller and torque controller are connected in parallel to realize both position and torque control simultaneously, then both control functions are achieved, but oscillation occurs in the closed feedback loop and controller performance is reduced
Solution Approach 1:
The patent implements dynamic switching between position control mode and torque control mode based on detected driver torque. When driver torque exceeds a threshold, the system switches to torque control mode; otherwise, it operates in position control mode. This dynamic adaptation eliminates the oscillation problem of parallel control while maintaining both control capabilities through temporal separation.
2Ease of operation
If position controller output is limited to ensure column torque controller dominance in hands-on situation, then manual steering control is improved, but position control performance in automatic driving mode is reduced
Solution Approach 1:
The system dynamically adjusts the active controller based on operating conditions. In hands-on situations (high driver torque), torque control mode is activated for optimal manual steering control. In hands-off situations (low driver torque), position control mode takes over for precise automatic driving control. This dynamic allocation eliminates the need for artificial output limiting while ensuring each mode performs optimally in its designated operating range.
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
This configuration enhances steering feel by reducing oscillations and improving overall control performance, allowing for better target motor torque calculation and reduced limitations on motor torque, thereby enhancing both manual and autonomous driving experiences.
Implementation Method 1
An electromechanical power steering mechanism has an electric motor for steering assist
Implementation Method 2
The steering shaft is coupled to a steering rack via a gear pinion. A rotation of the steering shaft causes an axial displacement of the steering rack by means of the gear pinion
Implementation Method 3
the arbitration unit weights and adds the first and second reference steering column torques
Data Source
AI summary
A motor vehicle power steering mechanism with an electric motor for steering assist and/or steering, and a steering controller, which controls the electric motor with a position control mode for autonomous driving and/or automatic steering and a torque control mode for manual steering by a driver. The steering controller includes a steering column reference controller, an arbitration unit, a column torque controller, a steering algorithm, and the steering system. The steering column reference controller calculates for position control based on a reference position and a measured position, and a first reference steering column torque. A steering algorithm calculates for torque control based on a measured column torque and a second reference steering column torque. The arbitration unit weights and adds the first and second reference steering column torques, and the output of the arbitration unit is input to the column torque controller.