Regenerative Braking Torque Control for Vehicle Stability
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Solution Overview
Problem
During active regenerative braking events in hybrid electric vehicles, the application of regenerative braking torque can lead to wheel slip, affecting vehicle stability and steering performance, particularly on low friction surfaces, as existing systems like ABS, TCS, and ESC primarily react to slipping rather than preventing it.
Innovation Solution
A method and apparatus that utilize inertial sensors to calculate and apply a maximum regenerative braking torque without causing under-steer or over-steer, by comparing sensor data to calibrated thresholds and allocating braking torque between regenerative and frictional braking systems, ensuring optimal stability and steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking torque is applied to capture braking energy, then energy recovery is improved, but wheel slip and loss of vehicle stability occur
Solution Approach 1:
The controller preemptively limits regenerative braking torque based on predicted wheel slip conditions and vehicle state, rather than reacting after slip occurs. This prevents wheel slip before it happens by calculating a maximum allowable regenerative braking torque that accounts for current traction conditions, vehicle speed, and driver braking input.
Solution Approach 2:
The system continuously monitors wheel speed, vehicle speed, and braking torque to dynamically adjust the maximum regenerative braking torque limit. This closed-loop feedback ensures that energy recovery is optimized while maintaining vehicle stability by adapting to changing road conditions and vehicle states in real-time.
2Use of energy by moving object
If regenerative braking torque is applied to recharge the ESS, then energy efficiency is improved, but steering control is degraded
Solution Approach 1:
The controller preemptively calculates and limits regenerative braking torque to prevent wheel slip that would compromise steering control, rather than reacting after steering degradation occurs. This ensures steering control is maintained while still capturing useful braking energy.
Solution Approach 2:
The system uses continuous feedback from wheel speed sensors and vehicle state monitors to dynamically adjust regenerative braking torque, ensuring that energy recovery does not compromise steering control under any operating conditions.
3Speed
If maximum regenerative braking torque is applied without limits, then braking performance is improved, but wheel slip increases on low friction surfaces
Solution Approach 1:
The controller preemptively establishes a maximum regenerative braking torque limit based on current road friction conditions, vehicle speed, and wheel slip risk assessment, preventing wheel slip before it occurs while maintaining effective braking performance.
Solution Approach 2:
The maximum regenerative braking torque limit is dynamically adjusted based on real-time vehicle conditions including wheel speed, vehicle speed, and inferred road friction conditions, allowing optimal braking performance across varying conditions without causing wheel slip.
4Productivity
If regenerative braking is used continuously, then fuel economy is improved, but vehicle control precision is reduced
Solution Approach 1:
The controller preemptively limits regenerative braking torque to maintain precise vehicle control, preventing the loss of control precision that would occur with unlimited regenerative braking application.
Solution Approach 2:
The system continuously monitors vehicle state and dynamically adjusts regenerative braking torque to maintain precise control while maximizing fuel economy benefits from regenerative braking.
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 approach enhances vehicle stability and steering performance by preemptively managing regenerative braking torque, reducing the likelihood of wheel slip and improving overall control during regenerative braking events.
Implementation Method 1
an electric motor/generator can be selectively operated in such a manner as to allow the device to act as a generator during an active regenerative braking event. When acting as a generator, the electric motor/generator recharges the ESS
Implementation Method 2
the electric motor/generator recharges the ESS while applying a negative torque to the drive wheels and/or the drive shaft, thus electronically slowing the HEV
Implementation Method 3
a frictional braking torque or FBT, with the calculated maximum RBT ranging from a theoretical maximum value or unrestricted value down to a zero value
Data Source
AI summary
A method of optimizing steering and stability performance of a vehicle includes measuring a set of inertial data during a regenerative braking event (RBE), calculating a set of vehicle performance data using the inertial data, and comparing the performance data to calibrated threshold data to determine a maximum regenerative braking torque (RBT). The maximum RBT is automatically applied during the active RBE. The vehicle includes a chassis, an electric motor/generator for applying an RBT, a frictional braking system, chassis inertial sensors for measuring a set of chassis inertial data, and a controller having an algorithm for calculating a set of vehicle performance data using the chassis inertial data. The controller determines the maximum RBT by comparing the vehicle performance data to corresponding threshold data. The chassis inertial sensors can include accelerometers, a yaw rate sensor, a steering rate sensor, speed sensors, and/or a braking input sensor.