EV Transmission Preloading for Smooth Motor Direction Reversal
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Solution Overview
Problem
Electric-propulsion cars experience metallic noises, vibrations, and jolts during reverse gear changes due to mechanical backlash in the transmission, which is caused by the high driving torque reversing the electric motor's rotation direction, leading to uncomfortable driving experiences.
Innovation Solution
Implement a transmission preloading procedure using an electronic motor-control equipment that regulates the electric motor's rotation speed and torque to minimize mechanical backlash by ensuring gentle contact of transmission gears, including a mechanical backlash compensation transient step and a stabilised preloading step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electric motor reverses rotation direction with high driving torque, then the vehicle can quickly change gear direction, but mechanical backlash causes metallic noises, vibrations and jolts
Solution Approach 1:
The control method applies a preliminary action by first reducing the electric motor's rotation speed before reversing direction. This preliminary speed reduction allows the transmission gears to engage smoothly without violent impacts, eliminating metallic noises and vibrations while maintaining efficient direction changes
Solution Approach 2:
The invention dynamically adjusts the electric motor's rotation speed during the gear reversal process. By continuously modulating the speed according to transmission state, the system optimizes the balance between quick response and smooth engagement, preventing harmful vibrations while maintaining operational efficiency
2Power
If the electric motor generates high driving torque during reversal, then the vehicle responds quickly to driver requests, but the gear teeth violently strike and rebound
Solution Approach 1:
The control method applies preliminary anti-action by reducing the electric motor's rotation speed before the reversal occurs. This pre-conditioning prevents the violent impact between gear teeth that would otherwise occur with high torque reversal, eliminating the harmful striking and rebound effects
Solution Approach 2:
The invention changes the operational parameters of the electric motor during reversal by dynamically adjusting rotation speed. This parameter modulation ensures that torque is applied smoothly without causing gear tooth impacts, while still maintaining the power needed for effective vehicle movement
Data Source
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Figure 3a~3c
AI summary
Method of controlling the electric motor of a road motor vehicle (1) comprising: a plurality of ground-resting wheels (8, 9); and an electric motor (4) which is mechanically connected to at least one drive wheel (9) of the vehicle by means of a transmission (11), and is adapted to drive into rotation said at least one drive wheel (9); the method of controlling the electric motor comprising a transmission preloading phase, in which the electric motor (4) delivers a driving torque capable of bringing the teeth of the various gears of the transmission (11) stably into abutment to one another, substantially without causing rotation of said at least one drive wheel (9); said transmission preloading phase comprising a mechanical backlash compensation transient step, wherein the rotation speed of the electric motor (4) is controlled such that the teeth of the various gears of the transmission (11) come into contact to one another with an approaching speed lower than a predetermined maximum threshold.