Steer Torque Manager Feed Forward Scaling for Driver Activity
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Solution Overview
Problem
Current steer torque managers in advanced driver assistance systems face challenges in simultaneously tracking wheel angle requests and suppressing torque disturbances from drivers resting their hands on the steering wheel, while ensuring comfortable handover of control and maintaining high automotive safety integrity.
Innovation Solution
A steer torque manager that uses a feed forward signal scaled based on driver activity, subtracted from the overlay torque request, to minimize unintentional steering wheel movements and pulsations, incorporating a driver in the loop factor and vehicle traveling velocity adaptation, with a nonlinear scaling of the feed forward signal to ensure smooth control transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wheel angle controller suppresses torque disturbance from the driver, then tracking accuracy of wheel angle request is improved, but the driver experiences high counteracting torque when taking control
Solution Approach 1:
The feedforward functionality anticipates driver torque by scaling the assistance torque signal before the wheel angle controller acts. This preliminary estimation allows the system to prepare for driver input, reducing the need for strong counteracting torque while maintaining tracking accuracy.
Solution Approach 2:
The system uses feedback from the torsion bar torque sensor to continuously monitor actual driver torque. This feedback is combined with the feedforward signal to dynamically adjust the scale factor, enabling the system to adapt to varying driver inputs while maintaining optimal tracking performance.
2Ease of operation
If the DIL functionality limits torque output to hand over control comfortably, then driver comfort is improved, but the system cannot suppress torque disturbance effectively
Solution Approach 1:
The system dynamically changes the scale factor parameter based on driver activity level. When driver activity is low, the scale factor increases to enhance feedforward compensation for better tracking. When driver activity increases, the scale factor decreases to reduce counteracting torque and improve comfort during handover.
Solution Approach 2:
The feedforward signal is made dynamic through continuous adjustment of the scale factor based on real-time driver activity detection. This dynamic adaptation allows the system to optimize both tracking accuracy and driver comfort depending on the current operational context.
3Measurement precision
If the scale factor assumes high values to suppress driver activity, then tracking accuracy is improved, but driver comfort deteriorates when driver takes control
Solution Approach 1:
The system uses feedback from the torsion bar torque sensor to detect when the driver is actively taking control. This feedback triggers a reduction in the scale factor, seamlessly transitioning from high tracking accuracy mode to comfortable handover mode without compromising either objective.
Data Source
AI summary
A steer torque manager (STM) for an advanced driver assistance system (ADAS) of a road vehicle and a method therefor. A driver in the loop functionality determines when to hand over control to a driver. A wheel angle controller uses an ADAS wheel angle request to produce an overlay torque request to be added to a torque request from an electrical power assisted steering. The STM is arranged to receive an assistance torque related signal. When driver assistance is provided by the ADAS, the STM is arranged to feed forward and subtract from the overlay torque request a feed forward signal scaled to be a scaled version of the assistance torque related signal, using a scale factor in the range from 0 to 1 that assumes a lower value if a measure of driver activity indicates high driver activity and a higher value if the measure indicates low driver activity.