Vehicle Shift Control via LIN Backup During CAN Failure
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Solution Overview
Problem
When CAN communication fails between the transmission control unit (TCU) and the gear actuator, vehicle shifting becomes impossible, preventing emergency driving.
Innovation Solution
The proposed shift control method utilizes a local interconnect network (LIN) communication line to allow the TCU to drive the gear actuator, enabling vehicle shifting by sensing communication failures and controlling the motor controller to engage target gear stages through LIN communication, using distinct forces for gear engagement and feedback mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CAN communication is used for controlling gear actuator, then communication speed and reliability are improved, but system complexity and cost increase due to additional communication lines and protocols
Solution Approach 1:
The communication system is segmented into two layers: CAN communication for normal high-speed operation and LIN communication as a backup for failure scenarios. This segmentation allows the system to maintain high reliability through protocol diversity while managing complexity by separating communication paths based on operational needs.
Solution Approach 2:
The system dynamically changes communication parameters by switching between CAN and LIN protocols based on detected failure conditions. When CAN communication fails, the system transitions to LIN communication with adjusted baud rates and message formats, allowing adaptive response to communication degradation while managing system complexity through parameter adjustment rather than complete system redesign.
2Adaptability or versatility
If LIN communication is added as backup, then system adaptability and emergency driving capability are improved, but device complexity increases due to dual communication systems
Solution Approach 1:
The LIN communication line is pre-configured and tested during system initialization to ensure it is ready for emergency use. Failure detection mechanisms are also established in advance, allowing the system to quickly switch to LIN mode without complex real-time decision-making, thereby improving adaptability while managing complexity through advance preparation.
Solution Approach 2:
The control unit acts as an intermediary that manages both CAN and LIN communication systems, routing commands appropriately based on system state. This centralized mediation simplifies the overall system architecture by providing a single point of control for dual communication paths, reducing the complexity that would otherwise arise from distributed control of multiple communication protocols.
3Ease of manufacture
If gear actuator is controlled through LIN communication, then ease of manufacture and cost are improved, but communication speed and response time deteriorate
Solution Approach 1:
The system dynamically adjusts communication protocols based on operational requirements. During normal operation, high-speed CAN communication is used for rapid response. In emergency situations, the system transitions to LIN communication, accepting reduced speed in exchange for improved manufacturability and cost-effectiveness. This dynamic adaptation allows the system to optimize performance based on real-time conditions.
Solution Approach 2:
The system uses LIN communication with enhanced parameters (higher baud rate, optimized message structure) to provide sufficient speed for emergency gear shifting, even though it doesn't match CAN performance. This partial action approach accepts that LIN is inherently slower but optimizes it to provide adequate response time for safety-critical operations, balancing cost benefits with acceptable performance.
Data Source
AI summary
A shift control method for a vehicle when CAN communication fails is provided to make a transmission control unit communicate with a motor controller via an LIN communication line. The shift control method includes: a failure sensing step of sensing, by the transmission control unit, whether the CAN communication fails; a shift stage sensing step of sensing, by the transmission control unit, whether a target shift stage is changed when the CAN communication failure is sensed as a performance result of the failure sensing step; and a gear engaging step of controlling, by the transmission control unit, the motor controller to drive a gear actuator through an LIN communication line so as to engage a target stage gear when the target shift stage is changed as the performance result of the shift stage sensing step.