Semi-Autonomous Steering Torque Scaling
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Solution Overview
Problem
Semi-autonomous steering systems in road vehicles experience torque artifacts due to driver resistance against steering guidance, leading to fluctuations in scaling factors and noticeable torque interactions.
Innovation Solution
A method for intelligent scaling of torque overlay intervention, which determines active intervention and driver override through torsion bar torque measurement, adjusts the scaling factor to its lowest value for specific driving situations, and fades out the factor completely if override persists, ensuring reduced torque artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the overlay torque is scaled by a scaling factor that is a function of driver applied steering wheel torque, then the steering assistance is adapted to driver input, but torque artifacts and fluctuations occur when the driver significantly overrides the intervention for an extended period
Solution Approach 1:
The patent applies dynamics by making the scaling factor adaptive rather than static. The scaling factor dynamically changes based on the duration of driver override, transitioning from a function of torque magnitude alone to a time-dependent function. This allows the system to adapt to prolonged override situations by progressively reducing the scaling factor, thereby eliminating torque artifacts while maintaining normal adaptive steering assistance during standard operation.
2Ease of operation
If the scaling factor is continuously adjusted based on driver torque input, then the steering system responds to driver intent, but noticeable torque interactions and artifacts occur during prolonged driver override
Solution Approach 1:
The patent implements periodic action through time-based evaluation intervals. The system periodically assesses the duration of driver override and adjusts the scaling factor in discrete time steps. This periodic adjustment mechanism allows the system to maintain responsive steering during normal operation while progressively reducing assistance during prolonged override periods, thereby eliminating torque artifacts without compromising ease of operation during standard use.
Data Source
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AI summary
Disclosed herein is a method for intelligent scaling of torque overlay intervention for a semi-autonomous steering system in a road vehicle (1) having a semi-autonomous steering function arranged to selectively apply a steering wheel overlay torque (Tc). If decided that a driver is significantly overriding an intervention the overlay torque (Tc) is scaled by a scaling factor (α) being a function of the applied steering wheel torque (Ta) (104). If decided that the driver has been significantly overriding the lane keeping aid intervention for more than a pre-determined first time period (ta) the scaling factor (α) is set to its lowest possible value for the specific driving situation (T3, 105). If decided that the driver has been significantly overriding the lane keeping aid intervention for more than a pre-determined second time period (tb), where the pre-determined second time period (tb) is equal to or exceeds (tb ≥ ta) the pre-determined first time period (ta) the scaling factor (α) is faded-out (T4, 106).