Regenerative Braking Torque Control During Transmission Downshifts
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Solution Overview
Problem
Regenerative braking in electric and hybrid vehicles experiences reduced capacity and sudden increases in braking power during downshifts, leading to wheel slip, jerky operation, and compromised safety and comfort.
Innovation Solution
A method and control arrangement that limits braking torque by the electric machine after a downshift to maintain braking power within a threshold range of the pre-downshift level, ensuring smooth transitions and preventing wheel slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a downshift is performed to increase regenerative braking capacity, then braking power is improved, but wheel slip and jerky operation occur
Solution Approach 1:
The control arrangement detects a downshift event and proactively limits the braking torque during a predetermined time period following the downshift. This preliminary action prevents the sudden increase in braking power that would cause wheel slip, while still allowing the vehicle to benefit from increased regenerative braking capacity after the transition period.
Solution Approach 2:
The system dynamically adjusts the braking torque based on the vehicle's transmission state. By detecting downshift events and temporarily modifying the braking torque profile, the system adapts to changing mechanical conditions to prevent wheel slip while maintaining effective regenerative braking.
2Power
If a downshift is performed to increase regenerative braking capacity, then braking power is improved, but passenger comfort deteriorates
Solution Approach 1:
The control arrangement anticipates the discomfort caused by sudden braking power increases during downshifts by implementing a predetermined time period following each detected downshift event. During this period, braking torque is limited to ensure smooth transitions, thereby maintaining passenger comfort while still enabling effective regenerative braking.
3Power
If a downshift is performed to increase regenerative braking capacity, then braking power is improved, but operational safety deteriorates
Solution Approach 1:
The control arrangement detects downshift events and proactively limits braking torque during a predetermined time period following the downshift. This preliminary protective action prevents wheel slip and maintains stable force transfer between wheels and road surface, thereby ensuring operational safety while still enabling effective regenerative braking.
Solution Approach 2:
The system continuously monitors transmission state and braking conditions, using feedback from downshift detection to dynamically adjust braking torque. This closed-loop control ensures that braking power remains within safe limits while maximizing regenerative braking effectiveness.
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
Maintains regenerative braking capacity while ensuring smooth retardation, enhancing passenger comfort, preventing cargo shifting, and maintaining operational safety.
Implementation Method 1
The electric machine of an at least partially electric vehicle can be used to regeneratively brake the vehicle. Regenerative braking refers to a process where the electric machine is used as a generator during braking.
Implementation Method 2
One way to increase the regenerative braking capacity is to increase the transmission ratio between the electric machine and the wheels, such as by performing a downshift in a gearbox arranged between the electric machine and the wheels.
Data Source
AI summary
A method of controlling retardation of a vehicle is disclosed, wherein the method is performed by a control arrangement, and wherein the vehicle comprises a transmission and an electric machine operably connected to driven wheels of the vehicle via the transmission. The method comprises the step of, in a retardation phase of the vehicle, limiting a braking torque provided by the electric machine during a time period following a downshift in the transmission such that the braking power applied to the driven wheels after the downshift is within a threshold range of the braking power applied to the driven wheels prior to the downshift. The present disclosure further relates to a computer program, a computer-readable, a control arrangement, and a vehicle.