Torque Distribution Control for Steering Stability in Electrified Vehicles
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Solution Overview
Problem
Conventional electronic stability control systems in through-the-road electrified vehicles are reactive and do not prevent oversteer or understeer from occurring, nor do they improve steering performance during linear steering conditions.
Innovation Solution
A torque distribution control system that uses wheel speed sensors and a steering wheel angle sensor to estimate virtual yaw rates and adjust torque distribution between independent torque generating systems for the front and rear axles, employing feedback control loops or model predictive control to maintain equal virtual yaw rates and prevent oversteer or understeer, with an ESC system operating in parallel to mitigate any detected conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ESC systems are used to detect and correct oversteer/understeer, then vehicle stability is improved during oversteer/understeer conditions, but the systems are reactive and do not prevent oversteer/understeer from initially occurring, and do not improve steering performance during linear steering conditions
Solution Approach 1:
The control system performs preliminary action by proactively adjusting torque distribution based on estimated virtual yaw rates before oversteer or understeer actually occurs. The system continuously monitors wheel speeds and steering wheel angle to estimate virtual yaw rates of front and rear axles, and adjusts torque distribution in advance to prevent the vehicle from entering oversteer or understeer conditions, rather than waiting for yaw rate sensors to detect the problem.
Solution Approach 2:
The system dynamically adjusts torque distribution between front and rear axles based on real-time estimation of virtual yaw rates. The torque distribution is continuously modified according to the difference between front and rear virtual yaw rates, allowing the system to adapt to changing driving conditions and maintain optimal steering performance during both linear and non-linear steering conditions.
2Ease of operation
If torque distribution is adjusted based on estimated virtual yaw rates from wheel speed sensors and steering wheel angle sensors, then steering performance during linear conditions is improved and oversteer/understeer is prevented, but the control system complexity increases
Solution Approach 1:
The system introduces virtual yaw rate estimation as an intermediary parameter that bridges the gap between available sensor data (wheel speeds and steering wheel angle) and the desired control objective (preventing oversteer/understeer and improving linear steering performance). By estimating virtual yaw rates from these sensors and using the difference between front and rear virtual yaw rates as a control signal, the system achieves improved steering performance without requiring additional complex sensors or computational models.
3Device complexity
If virtual yaw rate estimation is performed using wheel speed differences and steering wheel angle, then the need for yaw rate sensors is eliminated, but measurement precision for virtual yaw rate estimation may be reduced
Solution Approach 1:
The system creates a virtual copy of yaw rate information by estimating virtual yaw rates from wheel speed differences and steering wheel angle measurements. Instead of directly measuring actual yaw rates with physical sensors, the system computes virtual yaw rates that represent the rotational behavior of the front and rear axles, using the relationship between wheel speeds and steering input to infer the vehicle's rotational state.
Data Source
AI summary
Torque distribution control systems and methods for through-the-road electrified vehicles having distinct first and second torque generating systems for distinct first and second axles, respectively, utilize existing vehicle sensors to (i) obtain measured wheel rotational speeds and a measured steering wheel angle, (ii) estimate virtual yaw rates of the first and second axles using these measured values and other known vehicle parameters, (ii) predict whether oversteer or understeer of the vehicle is likely to occur based on the estimated first and second axle virtual yaw rates, and (iv) when oversteer or understeer of the vehicle is predicted to occur, adjust a torque distribution between the first and second torque generating systems to prevent the oversteer or understeer from occurring and to keep the vehicle on a constant turn path.