Variable Transmission Shift Hunting Control via Synchronous Point Detection
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Solution Overview
Problem
Shift hunting in variable transmissions leads to inefficient and annoying oscillations, potentially decreasing the useful life of drive trains and engines, as existing solutions like lock-out timers can result in rough transitions.
Innovation Solution
A method and system that control a transmission with a variator and contiguous operating ranges, using a controller to detect speed ratios and acceleration thresholds to prevent shifts between ranges, holding the current speed ratio at or near synchronous points to avoid oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a lock-out timer is used to prevent shift hunting, then shift oscillations are reduced, but transitions become rough and delayed
Solution Approach 1:
The controller proactively identifies potential shift hunting conditions by monitoring when the transmission ratio is approaching a synchronous point before oscillations actually occur. By detecting the trend toward instability and preemptively adjusting shift timing or holding the current ratio, the system prevents oscillations from developing in the first place, avoiding the need for reactive lock-out timers that cause rough transitions.
2Productivity
If shifts are executed at synchronous points, then transmission efficiency is improved, but drive train oscillations occur near shift points
Solution Approach 1:
The controller continuously monitors the transmission ratio and its rate of change, comparing actual values against target synchronous points. When approaching a synchronous point, the system adjusts shift timing based on real-time feedback about the transmission's state and trends, allowing shifts to occur at optimal moments that maintain both efficiency and stability without triggering oscillations.
Data Source
AI summary
A method of controlling a transmission (100) for a machine is disclosed. The transmission includes a variator (104). The transmission is operated in a first operating range (301). It is determined whether a current speed ratio is within a first predetermined range of a speed ratio associated with a first synchronous point (304) lying between the first operating range (301) and the second operating range (302). A desired speed ratio is determined and it is determined if the desired speed ratio is within a second predetermined range of the speed ratio. A shift between the first and second operating ranges (301, 302) is prevented and the variator (104) is controlled to hold the current speed ratio if the desired speed ratio is within the second predetermined range or the rate of acceleration of the machine is below the threshold acceleration.