Powertrain Torque Transition Control During Coasting
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Solution Overview
Problem
During coasting operations, powertrain systems face challenges in managing torque transitions smoothly, particularly when transitioning between gear states and under deceleration fuel cut-off conditions, leading to inefficiencies in fuel delivery and braking torque management.
Innovation Solution
A method that determines a desired driveline or transmission output torque transition profile and adjusts the friction braking torque command based on the difference between actual and desired torque levels, increasing or decreasing the command accordingly to maintain a smooth transition during transitional states, including torque converter clutch release and fuel delivery resumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the transmission steps down through lower gears during coasting, then fuel economy is improved through DFCO, but torque transitions become discontinuous and jerky
Solution Approach 1:
The friction braking system is activated in advance during transitional driveline states to preemptively counteract torque disturbances before they manifest as jerky transitions. The controller predicts upcoming gear state changes and applies braking torque proactively to maintain smooth torque delivery throughout the transition.
Solution Approach 2:
The friction braking system serves as an intermediary mechanism between the transmission and the driveline load. By introducing controllable friction braking torque, the system mediates the discontinuous torque changes from gear shifts and TCC release, transforming them into smooth transitions while preserving the fuel-saving benefits of DFCO.
2Use of energy by moving object
If the torque converter clutch is released during coasting, then transmission efficiency is improved, but torque delivery becomes discontinuous
Solution Approach 1:
The controller continuously monitors driveline torque and friction braking system status, using feedback signals to dynamically adjust braking torque commands. During TCC release transitions, the feedback mechanism detects torque disturbances and automatically modulates friction braking to compensate, ensuring continuous smooth torque delivery while maintaining the efficiency benefits of TCC release.
3Use of energy by moving object
If deceleration fuel cut-off is engaged during coasting, then fuel consumption is reduced, but torque management becomes complex during gear transitions
Solution Approach 1:
The friction braking system is designed to perform multiple functions: it provides primary braking, regulates torque during gear transitions, compensates for TCC release disturbances, and maintains smooth operation during DFCO engagement and disengagement. This multi-functionality reduces the need for separate control mechanisms, thereby managing complexity while preserving fuel-saving benefits.
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 enables a smooth and efficient torque transition, optimizing fuel usage and braking performance by leveraging the friction braking system to compensate for torque differences, thereby enhancing the powertrain's operational efficiency during coasting and gear changes.
Implementation Method 1
adjusting the friction braking torque command during a transitional driveline state between the first and second transition points by an amount corresponding to a difference between a magnitude Tout of the driveline output torque profile and a magnitude Tdesired of the desired driveline output torque transition profile
Data Source
AI summary
A method of operating a powertrain system during coasting operation, wherein the powertrain system includes a driveline component (e.g., a transmission, drive shaft, differential, axle or wheel) having an output torque profile. The method includes: (i) determining a desired output torque transition profile for the driveline component between a first transition point before an end of a first state, and a second transition point after a beginning of a second state; and (ii) in response to a braking torque request, generating a friction braking torque command to operate a friction braking system, and adjusting the friction braking torque command during a transitional state between the first and second transition points by an amount corresponding to a difference between a magnitude of the output torque profile and a magnitude of the desired output torque transition profile.