Engine Torque Control for Automatic Transmission Upshifts
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Solution Overview
Problem
Existing automatic transmission upshift control strategies face challenges in coordinating engine torque reduction and on-coming clutch pressure, leading to noticeable sag in engine torque and poor shift quality due to the timing mismatch between these events.
Innovation Solution
The use of an inverse dynamic model of the transmission to coordinate engine output torque and on-coming clutch pressure, achieving a desired output torque trajectory by determining engine torque commands and clutch pressure commands that produce the required input acceleration trajectory, with adaptive feedback adjustments to ensure accurate clutch pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a step engine torque reduction occurs before the on-coming clutch gains capacity, then the engine torque sag is avoided, but a noticeable sag in engine torque would be felt by the operator
Solution Approach 1:
The control system calculates and commands an initial on-coming clutch pressure in advance to ensure the clutch gains capacity at the precise moment needed for torque reduction, preventing both torque sag and operator-felt disruptions
Solution Approach 2:
The system uses closed-loop control to monitor clutch capacity development and engine torque, dynamically adjusting the torque reduction timing based on real-time feedback to achieve optimal coordination between clutch engagement and torque reduction
2Ease of operation
If the on-coming clutch is commanded to gain capacity prior to the step torque reduction, then shift quality is improved, but tie-up between the on-coming clutch and the off-going clutch occurs
Solution Approach 1:
The system pre-calculates the exact timing when the on-coming clutch will gain sufficient capacity and schedules the torque reduction to occur at that precise moment, preventing both premature torque reduction and clutch tie-up conditions
Solution Approach 2:
The control system dynamically adjusts the torque reduction timing based on real-time clutch pressure development, transitioning from fixed timing to adaptive timing that responds to actual clutch engagement conditions
3Ease of operation
If larger step torque reductions are used to produce smoother shifts, then shift quality improves, but the likelihood of tie-up between clutches increases
Solution Approach 1:
The closed-loop system continuously monitors clutch pressure and engine torque, using feedback to precisely control the timing and magnitude of torque reduction, ensuring smooth shifts without exceeding the threshold that would cause clutch tie-up
Solution Approach 2:
The system dynamically adjusts torque reduction parameters (timing, magnitude, rate) based on clutch engagement state and vehicle operating conditions, optimizing the balance between shift smoothness and clutch protection
Data Source
AI summary
An improved control for an automatically shiftable transmission upshift, wherein the engine output torque and on-coming clutch pressure are coordinated during the shift based on an inverse dynamic model of the transmission to achieve a desired output torque trajectory. At the initiation of an upshift, the engine torque is commanded to decrease in a ramp-like or sloping fashion to and engine output torque value calculated using the dynamic model. This ramp-like or sloping decrease provides smooth shifting, while reducing the likelihood of tie-up between on-coming and off-going clutches within the automatically shiftable transmission.