Automatic Transmission Abnormality Judgment During Slip Control

The abnormality judgment method dynamically adapts based on the operational state of the frictional engagement element. When slip control is detected (through slip ratio calculation), the judgment criteria switch from comparing actual gear ratio directly to comparing corrected gear ratio (where input revolution speed is adjusted by subtracting slip revolution speed). This dynamic adaptation resolves the contradiction by allowing higher input speeds during slip control while maintaining accurate abnormality detection through state-dependent judgment logic.

The invention changes the parameter used for abnormality judgment based on the operational state. During slip control, instead of using the raw input revolution speed, the system calculates a corrected input revolution speed by subtracting the slip revolution speed from the actual input revolution speed. This parameter transformation allows the system to maintain accurate gear ratio monitoring even when the input speed intentionally exceeds the output speed multiplied by the gear ratio.

The system dynamically switches between two judgment modes based on the operational state. When slip control is active (detected through slip ratio calculation exceeding a threshold), the system uses corrected gear ratio judgment. When slip control is inactive, it uses standard actual gear ratio judgment. This dynamic mode switching enables the system to maintain both slip control functionality and judgment reliability by adapting the criteria to the current operational context.

The invention introduces an intermediary correction step in the judgment process. When slip control is detected, the system calculates a corrected input revolution speed by subtracting the slip revolution speed from the actual input revolution speed before computing the gear ratio. This intermediary correction value serves as a mediator that bridges the gap between the intentional speed difference during slip control and the normal gear ratio expectations, preventing false abnormality detection while maintaining slip control functionality.

The system implements feedback by continuously monitoring the slip ratio (calculated from input and output revolution speeds and gear ratio) and using this information to adjust the abnormality judgment criteria. When the slip ratio exceeds a predetermined threshold, the system switches to corrected gear ratio judgment mode. This feedback mechanism enables the system to automatically adapt its judgment logic based on real-time operational conditions, improving detection accuracy without requiring overly complex external control systems.

The judgment logic dynamically adapts its complexity based on operational needs. During normal operation, the system uses simple actual gear ratio comparison. During slip control (detected through slip ratio calculation), it automatically switches to the more sophisticated corrected gear ratio comparison. This dynamic adjustment of logic complexity ensures high detection accuracy during critical slip control periods while maintaining simplicity during normal operation, balancing the trade-off between complexity and precision.