Dual-Motor Planetary Drivetrain for Speed-Decoupled EV Transmission
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Solution Overview
Problem
Conventional electric drivetrains (e-drives) are constrained by a fixed motor speed for a given road speed, limiting efficiency, torque optimization, and regenerative power capacity, and existing solutions like multi-mode gearboxes and dual motors on a common axis fail to alleviate this single degree of freedom constraint.
Innovation Solution
A dual motor input-coupled planetary gear train configuration that decouples motor speed from vehicle speed by positioning motors on opposite sides of a planetary gear set, allowing pseudo mechanical points and enabling both electrically and infinitely variable transmission capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional electric drivetrain uses a fixed motor speed for a given road speed, then the system structure is simple, but the efficiency, torque optimization, and regenerative power capacity are limited
Solution Approach 1:
The drivetrain is segmented into two independent motor units (first motor unit and second motor unit), each capable of independent operation. This segmentation allows the system to achieve variable transmission ratios through different operational modes (first mode with both motors operating, second mode with only the first motor operating), thereby improving efficiency and torque optimization without requiring a complex overall structure.
Solution Approach 2:
The system dynamically switches between different operational modes based on driving conditions. The controller can transition between the first operational mode (both motors operating) and the second operational mode (only first motor operating), enabling the drivetrain to adaptively optimize efficiency, torque output, and regenerative power capacity across varying road speeds and load conditions.
2Use of energy by moving object
If a multi-mode gearbox is employed to address efficiency limitations, then the efficiency may be improved, but the device complexity increases
Solution Approach 1:
Each motor unit is designed with universal functionality to operate in multiple roles. The first motor unit can operate independently in the second mode, while the second motor unit can join in the first mode. This multi-functionality allows the system to achieve variable transmission capabilities without requiring separate dedicated components for each function, thereby improving efficiency while controlling complexity.
3Force
If dual motors are arranged on a common axis, then the torque capability is increased, but the single degree of freedom constraint to vehicle speed remains
Solution Approach 1:
The system transitions from a single-degree-of-freedom constraint to a two-degree-of-freedom system by introducing a second independent motor unit. This dimensional change in the control space allows independent adjustment of torque and speed characteristics, enabling the drivetrain to operate at optimal efficiency points across a wider range of vehicle speeds and torque demands.
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 configuration enhances efficiency by conserving battery power, supports high efficiency operation, and allows for adjustable modes between single and dual motor operations, expanding operational modes to meet efficiency targets.
Implementation Method 1
a first torque generated by the first motor and a second torque generated by the second motor are summed at an output node of a planetary gear set coupled to each of the first motor and the second motor
Data Source
AI summary
Methods and systems are provided for an electric drive train of a vehicle. In one example, a four-node planetary gear set is included in the electric drive train with a first motor coupled to a first input node and a second motor coupled to a second input node of the four-node planetary gear set. The drive train may be operated at a first mechanical point when the first electric machine is operated at a substantially zero speed, and the drive train may be operated at a second mechanical point when the second electric machine is operated at a substantially zero speed, in one or more examples. Operation at either the first mechanical point or the second mechanical point may be achieved without clutches or hydro-mechanical devices.