Regenerative Torque Control for Hybrid Powertrain Deceleration
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Solution Overview
Problem
Hybrid powertrain architectures in the BAS configuration do not fully utilize the maximum capability of the electric machine to capture regenerative energy in lower transmission gear states to maintain a constant vehicle deceleration rate, limiting the capture of regenerative energy.
Innovation Solution
A method is implemented to detect operator brake requests and monitor the time between brake requests, initiating a maximized regenerative deceleration event by selecting a current fixed gear ratio and applying sufficient torque to achieve the maximum capability of the electric machine in that gear ratio, while reducing torque for each successive downshift to maintain a constant deceleration rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the maximum capability of the electric machine is applied in lower transmission gear states, then regenerative energy capture is maximized, but the vehicle deceleration rate becomes non-constant and unacceptable
Solution Approach 1:
The system dynamically adjusts the electric machine torque capability based on the current transmission gear state. In lower gear states, the controller allows the electric machine to operate at higher torque levels appropriate for that gear, rather than applying a static limitation. This dynamic adaptation enables full utilization of the electric machine's capability in each gear state while maintaining acceptable deceleration characteristics through proportional adjustment.
Solution Approach 2:
The controller changes the operational parameters of the electric machine based on transmission gear state. Specifically, the maximum torque capability parameter is adjusted according to the current gear ratio, allowing higher torque in lower gears and lower torque in higher gears. This parameter change enables the system to capture maximum regenerative energy in each gear state without causing non-constant deceleration.
2Stability of the object's composition
If the electric machine capability is limited to maintain constant deceleration rate, then vehicle stability is maintained, but the electric machine's maximum capability is not fully utilized
Solution Approach 1:
Rather than applying a static torque limitation, the system implements dynamic torque management that adapts to the current gear state. The electric machine torque capability is continuously adjusted based on the transmission gear ratio, enabling the system to capture maximum regenerative energy in each gear state while maintaining proportional deceleration characteristics that are acceptable for each gear level.
Solution Approach 2:
The controller modifies the electric machine torque parameter based on the current gear state. In lower gear states, higher torque levels are permitted, while in higher gear states, lower torque levels are applied. This parameter change strategy allows the electric machine to operate at its maximum capability in each gear state, thereby maximizing regenerative energy capture while maintaining vehicle stability through gear-appropriate deceleration rates.
3Loss of energy
If maximum regenerative torque is applied in lower gear states, then energy capture is maximized, but the deceleration rate becomes non-linear and unacceptable
Solution Approach 1:
The controller adjusts the electric machine torque parameter based on the current gear state, allowing maximum torque application in lower gears where it is appropriate. The torque magnitude is changed proportionally to the gear ratio, ensuring that the deceleration characteristics remain linear and predictable from the driver's perspective, while still capturing maximum regenerative energy in each gear state.
Solution Approach 2:
The system dynamically adapts the electric machine torque output to match the current gear state. In lower gear states, the electric machine can apply higher torque levels that are appropriate for that gear, maintaining linear deceleration characteristics. This dynamic adjustment ensures that the deceleration feels natural and predictable to the driver while maximizing regenerative energy capture in each gear state.
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 maximizes regenerative energy capture by the electric machine while maintaining a constant vehicle deceleration rate, allowing for greater utilization of the electric machine's capability across various gear states.
Implementation Method 1
Electric machine(s) may transform vehicle kinetic energy that is transmitted through the drive wheels to energy that is storable in an energy storage device
Data Source
AI summary
A method for maximizing regenerative energy captured by an electric machine in a powertrain including an engine, the electric machine and a transmission device configured to transfer torque through a driveline includes detecting an operator brake request and monitoring a time between the detected operator brake request and a preceding operator brake request that was last detected. A maximized regenerative deceleration event is initiated if the time exceeds a predetermined threshold time that includes monitoring a current fixed gear ratio that is selected from among a plurality of fixed gear ratios of the transmission device when the operator brake request is detected and applying a magnitude of torque at the axle that is sufficient for achieving a maximum capability of the electric machine to capture regenerative energy in the current fixed gear ratio.