Drivetrain Speed-Regulated Crawling via Electric Machine Torque Control
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Solution Overview
Problem
Existing methods for operating a drivetrain, particularly in parallel hybrid and purely electric vehicles, are not suitable for speed-regulated crawling operations without a planetary or overlap gear system, as they cannot effectively regulate torque between an electric machine and an internal combustion engine.
Innovation Solution
A method that regulates the torque supplied by the electric machine to approximate a nominal speed value by operating it as a motor for positive crawling torque and as a generator for negative crawling torque, allowing for speed-regulated crawling operations, and dynamically allocates crawling torque between the electric machine and internal combustion engine, with assistance from a brake system when necessary, to maintain the desired speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a planetary or overlap gear system is used between the drive aggregate and transmission, then speed-regulated crawling operation can be achieved, but the device complexity increases
Solution Approach 1:
The patent extracts the crawling torque generation function from the mechanical gear system and relocates it to the electric machine. By controlling the electric machine to supply positive or negative torque, the crawling function is achieved without requiring a planetary or overlap gear system, thereby reducing mechanical complexity while maintaining the desired speed-regulated crawling operation
Solution Approach 2:
The patent replaces the mechanical crawling torque generation mechanism (planetary or overlap gear system) with an electrical control mechanism. The electric machine, controlled through torque regulation based on speed feedback, substitutes for the mechanical gear-based crawling torque generation, achieving the same functional result through electrical rather than mechanical means
2Force
If the electric machine operates as a motor during crawling operation, then positive crawling torque is produced, but the electrical energy accumulator is discharged more intensively
Solution Approach 1:
The patent dynamically switches the electric machine's operating mode between motor and generator based on the required crawling torque direction. When positive crawling torque is needed, the electric machine operates as a motor (discharging the accumulator). When negative crawling torque is needed, it operates as a generator (charging the accumulator). This dynamic adaptation optimizes energy usage by utilizing both charging and discharging phases of the accumulator
Solution Approach 2:
The patent changes the operating parameters of the electric machine, specifically switching between motor and generator modes. This parameter change allows the system to adapt to different crawling torque requirements and optimize energy management by utilizing both charge and discharge cycles of the electrical accumulator, rather than operating in a single fixed mode
3Loss of energy
If the internal combustion engine is completely disengaged during crawling operation, then purely electric-powered crawling is achieved, but the crawling torque may be insufficient
Solution Approach 1:
The patent applies partial engagement of the internal combustion engine through clutch slipping operation. Instead of complete engagement or complete disengagement, the clutch operates in a slipping state, allowing partial torque transmission from the engine to the drive output. This enables the system to achieve the required crawling torque by combining electric machine torque with partial engine torque, maintaining energy efficiency while ensuring sufficient force
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
Enables speed-regulated crawling operations in drivetrains without a planetary or overlap gear system, optimizing energy usage by charging or discharging the electrical accumulator and efficiently dividing torque between the electric machine and internal combustion engine to maintain the specified speed.
Implementation Method 1
since the electric machine is being operated as a motor
Implementation Method 2
since the electric machine is being operated as a generator
Implementation Method 3
when the crawling torque is negative, if necessary also with assistance from a brake system
Data Source
AI summary
A method of operating a drivetrain of a motor vehicle. The drivetrain comprising a drive aggregate with at least one electric machine. During operation of the drivetrain according to the method, when an accelerator pedal and a brake pedal are not actuated, the drivetrain is operated in a speed-regulated crawling mode and during this mode a nominal speed value is compared with an actual speed value and, on the basis of the difference between these speed values, a crawling torque is produced as a control output. During a purely electrical speed-regulated crawling operation, if a positive crawling torque is produced as the control output, then the torque produced by the electric machine is regulated such that the actual speed value is approximately equal to the nominal speed value and, during such operation, an electrical energy accumulator of the drivetrain is discharged more intensively since the electric machine is operated as a motor.