Hybrid Engine Clutch Engagement Control During TCS Operation
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Solution Overview
Problem
The existing methods for controlling engine clutch engagement during traction control system (TCS) operation in hybrid vehicles face instability and delayed engagement due to sudden changes in motor speed caused by reduced frictional force on the road surface, leading to a difference between engine speed and motor speed.
Innovation Solution
The method involves determining a compensation value based on the difference between front and rear wheel speeds and slip amount to control engine clutch engagement, allowing for stable engagement by comparing engine speed with a relative speed and compensation value, and ensuring engine stall prevention by calculating rear motor speed based on rear wheel speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If engine clutch engagement control is performed based on motor speed during TCS operation, then the control system can respond to TCS torque requests, but the sudden change in motor speed causes difference between engine speed and motor speed, leading to deterioration of engagement stability and delay of engagement
Solution Approach 1:
The patent introduces rear wheel speed as an intermediary parameter to mediate between motor speed and engine speed during TCS operation. Instead of directly comparing engine speed with motor speed (which changes suddenly), the system uses rear wheel speed as a stable reference that is not affected by TCS-induced motor speed fluctuations, thereby maintaining engagement stability while enabling timely engagement control
Solution Approach 2:
The patent extracts the destabilizing factor (motor speed changes during TCS operation) from the engagement control decision process. By separating the engagement control logic from direct motor speed dependency and using rear wheel speed instead, the system removes the source of speed difference and engagement instability while preserving the ability to respond to TCS operation conditions
2Reliability
If motor torque is reduced in response to TCS-demanded torque request, then torque reduction control is achieved for stable travel, but motor speed changes suddenly due to reduced frictional force, causing difference between engine speed and motor speed
Solution Approach 1:
Rear wheel speed serves as an intermediary reference that decouples the engine clutch engagement control from direct motor speed variations. During TCS operation when motor torque is reduced and motor speed changes suddenly, the rear wheel speed provides a stable benchmark that maintains the perceived speed synchronization between engine and motor, preventing the speed difference that would otherwise occur
Solution Approach 2:
Instead of using the affected parameter (motor speed) for engagement control, the patent inverts the approach by using the unaffected parameter (rear wheel speed) as the control basis. This inversion allows the system to maintain speed synchronization relationships despite motor speed changes caused by TCS torque reduction
Data Source
AI summary
A system and method of controlling engine clutch engagement during TCS operation of a hybrid vehicle are provided. The method includes determining whether a TCS is operating and upon determining that the TCS is operating, determining a compensation value for early engagement of an engine clutch during the TCS operation based on a difference between a front wheel speed and a rear wheel speed and a slip amount of front wheels. Additionally, the method includes determining whether engagement of the engine clutch is capable of being started based on the compensation value and starting the engine clutch engagement. Since the engagement of the engine clutch is controlled based on the speed of non-drive wheels during TCS operation, the engagement stability of the engine clutch is improved and the amount of time required to engage the engine clutch is decreased.