Electric Propulsion System Sequential Gear Shift
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Solution Overview
Problem
Electric propulsion systems in commercial and industrial vehicles face challenges in maintaining robustness and performance due to the distinct characteristics of electric motors compared to internal combustion motors, requiring dedicated control strategies to manage torque distribution and gear changes without interrupting torque delivery.
Innovation Solution
A propulsion system with two parallel lines, each comprising an electric motor, gearbox, and clutch, where the control of one line is independent of the other, allowing sequential gear ratio changes to avoid torque interruption, with the operational line supplying maximum torque during gear changes and dynamic torque calculation to prevent motor damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If simultaneous gear change is performed on both propulsion lines, then gear ratio is updated to match vehicle speed, but torque delivery is interrupted during gear change
Solution Approach 1:
The gear change operation is segmented into sequential steps across the two propulsion lines rather than simultaneous execution. The control unit coordinates the gear changes to occur at different times, with one propulsion line completing its gear change while the other maintains torque delivery, thereby avoiding complete torque interruption.
Solution Approach 2:
The control unit prepares and coordinates the gear change sequence in advance, determining which propulsion line should perform gear change first based on current operating conditions. This preliminary coordination ensures that torque delivery is maintained by the operational line before the other line begins its gear change.
2Adaptability or versatility
If one propulsion line is deactivated for gear change, then gear ratio is updated, but the line cannot supply torque during the change
Solution Approach 1:
The two propulsion lines are merged in their torque delivery function to the common axle. When one line is deactivated for gear change, the other line compensates by supplying the full torque requirement, combining their capabilities to ensure continuous power delivery to the vehicle.
Solution Approach 2:
The system dynamically redistributes torque requirements between the two propulsion lines based on their operational state. When one line undergoes gear change, the control unit dynamically adjusts the torque demand on the operational line to match the total vehicle requirement, ensuring continuous power supply.
3Productivity
If both propulsion lines operate with different torque values, then torque distribution is optimized, but thermal stress increases on electric motors
Solution Approach 1:
The control system implements periodic alternation in the operation pattern of the two propulsion lines. When one line is subjected to higher thermal stress, the system periodically switches roles or distributes torque differently in subsequent operations, allowing thermal load to be distributed over time across both motors rather than concentrating stress on one.
Data Source
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AI summary
Electric propulsion system (S) comprising first (L1) and second (L2) propulsion lines, operably individually connectable with a common drive axle (X), each propulsion line comprising an electric motor (M1, M2), a gearbox (G1, G2) comprising at least two gear ratios (1st Gear, 2nd Gear), a clutch (C1, C2) to connect/disconnect the relative propulsion line from the respective driving axle (X, Y) of the same vehicle, processing means (ECU) configured to command the interruption of the torque delivery and consequent gear change first in the propulsion line whose maximum deliverable driving torque is lower and, at the end of the gear change, the interruption of the torque delivery and consequent gear change in the other propulsion line.