Push-Button Shifter Redundant Switch State Logic
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Solution Overview
Problem
Conventional shift-by-wire transmission systems face challenges in accurately determining the state of push-buttons without mechanical linkages, leading to potential errors in transmission range selection due to rare switch closure patterns or transient electrical faults.
Innovation Solution
A push-button shifter assembly with redundant switches and a controller that determines the 'pressed', 'released', or 'unknown' state of each button by monitoring the temporal coincidence of switch closures and openings within calibrated intervals, using analog-to-digital converters to process switch signals and execute control actions based on determined states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple redundant switches are used in each push-button, then reliability of button state determination is improved, but device complexity increases
Solution Approach 1:
The controller continuously monitors the state of multiple redundant switches and uses feedback logic to determine the actual button state. The system evaluates whether switches closed within a calibrated time interval and adjusts the determined state based on this feedback, resolving contradictions between using fewer switches and maintaining reliability.
Solution Approach 2:
The system changes the parameter of time by introducing a calibrated time interval threshold. This allows the controller to distinguish between legitimate simultaneous switch closures (indicating a pressed state) and sequential closures (indicating potential faults), thereby maintaining reliability without requiring all redundant switches to be identical in behavior.
2Measurement precision
If all redundant switches must close simultaneously to indicate a pressed state, then measurement precision is improved, but reliability decreases due to transient electrical faults
Solution Approach 1:
The system prepares for potential switch failures by having multiple redundant switches and pre-programmed fault tolerance logic. When one switch fails to close due to a transient fault, the remaining switches provide a cushion that allows the system to still correctly identify the pressed state through temporal correlation analysis.
Solution Approach 2:
The system accepts that not all redundant switches need to close perfectly simultaneously. By requiring only a majority or plausible temporal correlation of switch closures within a calibrated interval, the system uses partial action (not all switches must succeed) while still achieving reliable detection.
3Measurement precision
If a calibrated time interval is used to determine simultaneous switch closure, then button state determination accuracy is improved, but loss of time increases
Solution Approach 1:
The controller continuously and periodically samples the state of all redundant switches at high frequency. This periodic monitoring allows the system to detect switch closures and their temporal relationships rapidly, minimizing the time penalty associated with using a calibrated interval for accuracy.
Data Source
AI summary
A vehicle or other system includes an actuator assembly operable to achieve a selected operating state of the system in response to an electronic state selection signal, a push-button shifter assembly, and a controller. The shift assembly includes push-buttons, each including at least three redundant switches. A binary open/closed state of each switch defines the electronic state selection signal. The controller is in by-wire communication with the actuator and push-button shifter assemblies, and receives the electronic state selection signal. The controller determines a pressed, released, or unknown button state of each push-button by determining, in response to the electronic state selection signal, if all of the redundant switches have closed. If all of the redundant switches have not closed, the controller determines whether fewer than all of the switches have closed and opened within a calibrated time interval of each other.