Distributed Modular Powertrain for Electric Vehicles
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Solution Overview
Problem
State-of-the-art electric vehicle powertrains face inefficiencies in low torque and speed ranges, failing to meet performance criteria while optimizing for efficiency, and require higher rated torque and power for hill climbing and high-speed scenarios, leading to suboptimal torque output.
Innovation Solution
A distributed modular powertrain with wheel hub motors and a torque distribution control algorithm that connects electric motors to each wheel, determining power loss and optimizing torque distribution between axles for maximum efficiency, enabling efficient low-power operation and boosting performance as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single central electric motor is designed to cover the entire load range, then performance requirements (high torque and power) are met, but efficiency in the typical low torque and speed range deteriorates
Solution Approach 1:
The powertrain is segmented into multiple independent traction units distributed across different axles. Each unit has its own electric motor and can operate independently or in combination. This allows the system to select only the necessary units for operation based on load requirements, keeping individual motors operating in their high-efficiency ranges even during low-power typical drive cycles.
Solution Approach 2:
The system dynamically adjusts which traction units are active based on real-time power and torque demands. During typical urban drive cycles, only one axle's traction units operate. During high-performance scenarios like acceleration or hill climbing, additional traction units are activated. This dynamic configuration allows the motors to operate near their optimal efficiency points across varying load conditions.
2Loss of energy
If the motor's best point of operation is set in the homologation cycle load path, then efficiency is improved, but torque output at high motor speed deteriorates
Solution Approach 1:
Multiple traction units with identical or similar motor characteristics are distributed across axles. When one unit operates in its optimal efficiency range during typical drive cycles, other units remain standby or are activated when higher torque is needed. The segmentation allows the system to maintain motors in their efficient operating zones while providing torque on demand through coordinated operation of multiple units.
Solution Approach 2:
Each traction unit is designed with universal capability to handle both typical low-power operation and high-performance scenarios. The distributed architecture allows any combination of units to contribute to total torque output, enabling the system to meet diverse operational requirements from efficient city driving to high-speed hill climbing with the same hardware configuration.
3Loss of energy
If distributed traction units are used for lower power output, then efficiency in typical drive cycles is improved, but device complexity increases
Solution Approach 1:
The powertrain is divided into modular traction units that can be independently controlled. Each unit contains an electric motor and associated control systems. This segmentation enables efficient operation during typical drive cycles by activating only necessary units, while the modular design allows for scalable complexity - systems can be configured with 2, 4, or more units depending on performance requirements.
Solution Approach 2:
The control system continuously monitors power and torque demands, battery state, and operational conditions to dynamically determine which traction units should be active. This feedback mechanism optimizes efficiency by keeping motors in their high-efficiency operating ranges while automatically managing the complexity of coordinating multiple distributed units across different axles.
Data Source
AI summary
A method for controlling a vehicle driveline includes connecting an electric motor to each of respective vehicle wheels, determining from driver input a magnitude of demanded wheel torque, determining speed of each wheel, using demanded wheel torque and the respective wheel speed to determine from a power loss map a current power loss for each motor, and transmitting power from the motor having the lowest current power loss to the respective vehicle wheel.