Automated Transmission Prepositioning for Shift Timing
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Solution Overview
Problem
Existing methods for controlling automated transmissions with discrete ratios in motor vehicle powertrains do not allow for permanent optimal preselection of the next gear change, leading to inefficient and delayed gear shifts.
Innovation Solution
A method that continuously calculates a Boolean variable indicating the expected direction of the next gear change, using inputs such as accelerator setpoint, current transmission ratio, and vehicle acceleration, to preposition operating parameters like gear engagement and hydraulic pressures, enabling early preparation for gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gear preselection is delayed until vehicle speed reaches a threshold, then the system waits for optimal conditions, but gear change response time increases
Solution Approach 1:
The system performs preliminary action by continuously calculating the Boolean variable and prepositioning the inactive shaft to the anticipated next gear ratio in advance, before the actual gear change decision is made. This allows the mechanical preselection to be ready beforehand, reducing the time required when the gear change actually needs to occur.
Solution Approach 2:
The system dynamically adjusts the prepositioning strategy based on real-time vehicle conditions by continuously recalculating the Boolean variable at a frequency that depends on computer operation. This dynamic approach allows the system to adapt to changing driving conditions while maintaining optimal prepositioning readiness.
2Measurement precision
If the system waits for gear change conditions to be met before preselection, then preselection accuracy improves, but the frequency and magnitude of operations during actual gear changes increases
Solution Approach 1:
By continuously calculating the Boolean variable and prepositioning the inactive shaft in advance, the system prepares the gear change beforehand. This reduces the operational workload and magnitude of actions required at the moment of actual gear change, improving efficiency while maintaining accuracy through continuous monitoring.
Solution Approach 2:
The Boolean variable is recalculated periodically in a continuous manner, ensuring that the prepositioning information is always up-to-date. This continuous calculation approach maintains high prediction accuracy while enabling smooth, efficient gear changes without sudden large-magnitude operations.
3Speed
If the inactive shaft engages a gear in advance, then gear change speed increases, but the system complexity increases due to continuous Boolean variable calculation
Solution Approach 1:
The control system uses existing input data (accelerator setpoint, transmission ratio, vehicle acceleration) that are already being processed by the vehicle's control systems. By utilizing these existing data streams to calculate the Boolean variable, the system achieves fast gear changes without adding significant complexity, as it leverages data that is already available in the vehicle's control architecture.
Data Source
Figure 1
Figure 2~3
AI summary
A device for controlling an automated transmission with discrete gear ratios of a motor vehicle power plant able to preposition at least one transmission system operating parameter as a function of the next gear change to be performed, comprises a means (1) of estimating the gradient (P) of the road surface along which the vehicle is running, and comprises a stored map (9) linking the accelerator instruction, the gradient (P) of the road surface, and the sign of the actual acceleration of the vehicle. The device comprises a logic processor (3) which continuously delivers a Boolean upshift variable signalling a forthcoming upshift or downshift in transmission ratio, as a function of which Boolean variable the said operating parameter is prepositioned.