EV Drivetrain Torque Distribution for Efficiency
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Solution Overview
Problem
Conventional electric vehicle drive trains face inefficiencies in low load ranges, failing to meet performance criteria for torque and power, especially in urban and homologation cycles, leading to reduced range and increased battery capacity needs.
Innovation Solution
A method controlling an electric vehicle drivetrain with multiple drive units, optimizing torque distribution based on efficiency in different operating modes, allowing for efficient operation in low load cycles and high performance scenarios by activating additional drive units as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the electric motor is designed with nominal values for power and torque optimized for the homologation cycle load path, then the efficiency in typical urban drive cycles and homologation cycles is improved, but the starting torque at high engine speeds deteriorates
Solution Approach 1:
The drive train is segmented into multiple electric motors (first electric motor and second electric motor) that can operate independently or in combination. This segmentation allows each motor to be optimized for different operating ranges, with the first motor handling low-load efficient operation and the second motor providing high-torque capability when needed, thereby resolving the contradiction between efficiency and high-speed torque delivery.
Solution Approach 2:
The control system dynamically switches between different operating modes and motor combinations based on real-time operating conditions. The control unit selects whether to operate in first operating mode (using first motor only), second operating mode (using second motor only), or third operating mode (using both motors together), enabling the system to adapt its torque distribution strategy to maintain both efficiency and performance across varying drive conditions.
2Device complexity
If a conventional drive train with fixed translation ratio is used, then the structure is simple, but the drive train efficiency deteriorates in low load ranges
Solution Approach 1:
The drive train employs variable transmission ratios through the coordinated operation of multiple electric motors with different gear ratios. The system can dynamically adjust the effective transmission ratio by selecting different motor combinations and control strategies, allowing the drive train to operate at optimal efficiency points across the entire load spectrum rather than being constrained to a fixed ratio.
Solution Approach 2:
The system changes operating parameters (motor selection, torque distribution, rotation speeds) based on the load range. In low load ranges, the control unit optimizes the operating parameters to maximize efficiency, while in high load ranges, it adjusts parameters to deliver required performance, thereby maintaining high efficiency across varying operating conditions without requiring a complex multi-gear mechanical transmission.
3Duration of action of moving object
If the electric motor operates in low load range, then the range of the electric vehicle is extended, but the torque and power output deteriorates
Solution Approach 1:
The drive train is divided into multiple electric motors with different power and torque characteristics. The first electric motor is optimized for low-load efficient operation to extend range, while the second electric motor provides high-torque capability for acceleration and hill climbing. This segmentation allows the system to achieve both extended range through efficient low-load operation and sufficient power output when high performance is required.
Solution Approach 2:
The system merges the capabilities of multiple electric motors to achieve both extended range and high power output. When high torque and power are needed, the control unit activates both motors working together in the third operating mode, combining their outputs to deliver the required performance while maintaining overall system efficiency through intelligent torque distribution and rotation speed coordination.
Data Source
AI summary
A method for controlling an electric vehicle drivetrain having least two drive units with wheels located on opposite axles are driven by respective drive units, includes in a first operating mode, the ratio of the torques provided by the drive units in each case for a given torque requirement is set taking into account the efficiency applicable to each drive unit under the given operating conditions, and in a second operating mode, the ratio of the torques provided by the drive units in each case for a given torque requirement is set independently of the efficiency applicable to each drive unit under the given operating conditions.