Hybrid Powertrain Regenerative Braking Control for Degraded Transmission
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Solution Overview
Problem
Hybrid vehicles experience delayed and inadequate braking during regenerative braking due to transmission degradation, as the negative torque provided by the electric machine is not effectively applied, leading to suboptimal deceleration and increased reliance on friction brakes.
Innovation Solution
A method that predicts the transmission input shaft speed based on the output shaft speed and adjusts the actuator to maintain the input shaft speed above a threshold, allowing for earlier initiation of automatic friction braking and reduction of negative torque, thereby compensating for transmission degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If negative torque is applied by the electric machine during regenerative braking, then vehicle deceleration is improved, but transmission degradation causes delayed and inadequate braking response
Solution Approach 1:
The system predicts transmission input shaft speed based on output shaft speed before actual degradation occurs, enabling early detection and preliminary corrective actions. The controller compares predicted vs. actual input shaft speed to identify degradation trends before they compromise braking performance, allowing proactive adjustment of braking strategy.
Solution Approach 2:
The control system acts as an intermediary between the electric machine's negative torque and the friction brakes, coordinating their interaction. When degradation is detected through speed prediction discrepancies, the controller modulates the distribution of braking force between regenerative and friction systems, ensuring reliable deceleration despite transmission issues.
2Force
If friction brakes are engaged to provide desired braking force, then vehicle braking performance is improved, but response time is delayed due to transmission degradation detection
Solution Approach 1:
The system performs preliminary detection of transmission degradation by continuously predicting input shaft speed from output shaft speed and comparing it with actual measurements. This early warning system allows the controller to prepare friction brake engagement before actual braking performance deteriorates, minimizing response time delays.
Solution Approach 2:
The controller uses feedback from the comparison between predicted and actual transmission input shaft speed to continuously monitor transmission health. When degradation is detected through this feedback mechanism, the system automatically adjusts braking force distribution, reducing the time needed to achieve desired braking performance.
3Reliability
If transmission input shaft speed is maintained above threshold, then transmission fluid flow and pressure are improved, but negative torque application is reduced
Solution Approach 1:
The system dynamically adjusts the transmission input shaft speed by modulating the negative torque from the electric machine. When degradation is detected, the controller dynamically changes operating parameters to maintain input shaft speed above the threshold needed for proper fluid flow, while continuously adjusting torque levels to compensate for the reduced braking effectiveness.
Solution Approach 2:
The controller changes operating parameters including negative torque magnitude and transmission input shaft speed to maintain optimal fluid flow conditions during degradation. By adjusting these parameters in real-time based on predicted vs. actual speed comparisons, the system ensures transmission pump receives adequate input speed while compensating for reduced braking force.
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 improves vehicle performance and braking efficiency during transmission degradation by reducing the time to detect and respond to transmission issues, ensuring timely control actions and maintaining desired transmission fluid flow or pressure.
Implementation Method 1
a threshold input shaft speed below which a transmission pump outputs less than a desired amount of transmission fluid flow or pressure
Data Source
AI summary
Systems and methods for operating a transmission of a hybrid powertrain that includes a motor/generator are described. The systems and methods may adjust one or more actuators in response to an estimated transmission input shaft speed that is determined from transmission output shaft speed. The one or more actuators may include a transmission clutch, the motor/generator, or a gear selection solenoid.