Brake-To-Steer Longitudinal Feedback With Transmission Shift Compensation
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Solution Overview
Problem
Brake-to-steer functionality in vehicles often causes rapid and uneven deceleration, leading to an unnatural driving experience due to the lack of longitudinal compensation during lateral steering maneuvers.
Innovation Solution
Implementing a closed-loop longitudinal control system that adjusts transmission gears or equivalent shifts to maintain optimal engine or electric motor speed and torque, using brake and propulsion torque commands to counteract rapid deceleration and enhance the driving experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If brake-to-steer functionality is implemented to achieve lateral control during steering failure, then lateral steering capability is improved, but longitudinal deceleration becomes rapid and unnatural
Solution Approach 1:
The system implements closed-loop longitudinal control by continuously measuring actual vehicle longitudinal acceleration and comparing it to desired longitudinal acceleration. The controller adjusts propulsion torque requests based on the difference between measured and desired acceleration, thereby compensating for the rapid deceleration caused by brake-to-steer and achieving a more natural deceleration feel.
Solution Approach 2:
The system dynamically adjusts transmission gear ratios to maintain optimal engine or electric motor speed and torque during brake-to-steer maneuvers. By changing the gear ratio parameter, the system can modulate the powertrain output to counteract unwanted deceleration while preserving lateral steering capability.
2Ease of operation
If brake torque is applied to individual wheels for lateral steering, then steering control is achieved, but longitudinal disturbance and unnatural driving experience occur
Solution Approach 1:
The closed-loop control system continuously monitors longitudinal acceleration and uses this feedback to adjust propulsion torque requests in real-time. This feedback mechanism allows the system to counteract the longitudinal disturbances generated by differential brake torque application, maintaining steering control while reducing harmful longitudinal effects.
Solution Approach 2:
The system applies counteracting propulsion torque to offset the longitudinal deceleration caused by brake-to-steer. By generating opposing force through the powertrain, the system neutralizes the unwanted longitudinal disturbance while preserving the lateral steering function.
3Speed
If transmission gears are adjusted to maintain optimal engine speed and torque, then longitudinal control is improved, but system complexity increases
Solution Approach 1:
The controller integrates multiple functions including longitudinal control, transmission shift management, and brake-to-steer coordination into a single control module. By making the controller multi-functional, the system achieves improved speed control without proportionally increasing overall system complexity, as the same hardware performs multiple control tasks.
Solution Approach 2:
The system combines longitudinal control, lateral control, and transmission management into an integrated control architecture. By merging these previously separate control functions into a unified system, the patent reduces overall complexity while maintaining optimal engine speed and torque control during brake-to-steer maneuvers.
Data Source
AI summary
A number of illustrative variations may include a system including brake-to-steer algorithms may achieve lateral control of a vehicle without longitudinal compensation but may also force a vehicle to slow down too rapidly before appropriate lateral movement can be achieved and may deliver an unnatural driving experience for vehicle occupants. A more natural feeling deceleration may be achieved by optimally selecting appropriate transmission shifts to allow for optimal engine speed or electric motor speed and torque based on current vehicle speed thereby reducing undesirably longitudinal disturbance.