Shift-by-wire Transmission Voting Strategy for Mode State Accuracy
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Solution Overview
Problem
Shift-by-wire transmission systems face challenges in accurately determining the mode state of a transmission upon restart, leading to potential false entries or exits from Neutral Hold or Neutral Tow modes, resulting in unwanted vehicle movement or battery drainage during towing.
Innovation Solution
A voting strategy is implemented using a controller with multiple memories to write and read remembered mode states, ensuring that the transmission enters a consistent mode state upon restart by comparing the states from different control modules, and optionally entering Assembly mode or disabling the automatic return to Park feature when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single control module is used to determine mode state, then device complexity is reduced, but reliability deteriorates due to potential false entries or exits from Neutral Hold or Neutral Tow modes
Solution Approach 1:
Each control module independently maintains its own memory of the mode state with identical functionality, allowing each module to operate autonomously and reliably determine mode state without relying on other modules, thus resolving the contradiction between device complexity and reliability
Solution Approach 2:
The control system is divided into multiple independent control modules, each with its own memory for storing mode state. This segmentation allows parallel operation and cross-verification of mode state determinations, improving reliability while maintaining manageable complexity through modular design
2Reliability
If multiple memories are used to store mode states, then reliability is improved through voting strategy, but device complexity increases
Solution Approach 1:
Each control module independently manages its own memory and performs self-verification of mode state without requiring complex external coordination. The voting strategy emerges naturally from independent module operations, reducing overall system complexity while maintaining high reliability
Solution Approach 2:
Multiple control modules with identical functionality are combined in parallel, each contributing its mode state determination to a voting process. This merging approach distributes the reliability burden across modules while the voting logic remains simple, balancing reliability improvement with acceptable complexity
3Object-affected harmful factors
If automatic return to Park feature is always active, then safety is improved by preventing unwanted vehicle movement, but adaptability deteriorates during towing operations when Neutral mode is required
Solution Approach 1:
The automatic return to Park feature is made dynamic through the voting strategy: it remains active when two or more modules indicate Normal mode, but automatically deactivates when modules indicate Neutral Hold or Neutral Tow mode. This dynamic adjustment allows the system to adapt to different operational requirements, resolving the contradiction between safety and adaptability
Solution Approach 2:
The system changes the operational parameter of the automatic return to Park feature based on mode state determination. When Neutral Hold or Neutral Tow mode is detected through voting, the feature parameter switches from active to inactive, enabling towing operations while maintaining safety during normal operation
Data Source
AI summary
A voting strategy is used to determine the mode state of a transmission when a vehicle is restarted. The transmission includes a return to park feature and a controller including at least three memories. The controller is configured to write a remembered mode state into each memory. The remembered mode state is one of a Normal mode state that allows the transmission to automatically shift to Park, a hold mode state that causes the transmission to remain in Neutral and not automatically shift to Park upon detecting a triggering event or other mode states. The controller reads each memory and, when at least two of the remembered mode states are the same mode state, causes the transmission to enter a mode state corresponding to the same mode state.