Automatic Transmission Shift Control Torque Share Constraint
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Solution Overview
Problem
Existing shift control methods for automatic transmissions face challenges in determining control operation amounts when there are three control operation amounts for two shift target values, leading to difficulties in achieving desired shifts, particularly in handling torque exchanges between engagement devices and maintaining drivability.
Innovation Solution
A shift control device and method that uses a predetermined shift model to determine control operation amounts by setting shift target values based on output shaft torque and input shaft speed variation, and torque capacities of engaged and released engagement devices, with torque shares between these devices serving as a constraint condition to manage torque exchanges during gear shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If shift model control is used to determine control operation amounts, then shift precision and drivability are improved, but when there are three control operation amounts for two shift target values, the equation of motion cannot be solved uniquely
Solution Approach 1:
The patent changes the parameter representation from absolute torque values to torque share ratios. By expressing the relationship between engaged-side and released-side clutch torques as a ratio (torque share), the system transforms an unsolvable system with 3 unknowns and 2 equations into a solvable system where the torque share serves as an additional constraint parameter, enabling unique determination of all control operation amounts.
2Object-generated harmful factors
If hydraulic pressure of released-side engagement device is gradually decreased and then temporarily increased to cancel inertia torque, then inertia torque is canceled, but shift completion is delayed and drivability deteriorates
Solution Approach 1:
The patent changes the control parameter from hydraulic pressure manipulation to direct torque control through the shift model. By calculating the required torque values based on the equation of motion and torque shares, the system can cancel inertia torque through precise torque modulation without the time-consuming hydraulic pressure adjustments, thereby reducing shift completion time while maintaining drivability.
3Object-generated harmful factors
If engine torque reduction control is executed separately from shift model control to cancel inertia torque, then inertia torque is canceled, but the overall shift model control collapses and requires re-solving the equation of motion
Solution Approach 1:
The patent merges engine torque reduction control with shift model control into a unified control framework. By incorporating the engine torque as one of the three control operation amounts to be determined by the shift model (along with engaged-side and released-side clutch torques), the system eliminates the need for separate control loops and maintains continuous equation of motion validity throughout the shift process.
4Stability of the object's composition
If torque shares between engagement devices are controlled, then torque exchange during shifting is managed smoothly, but additional control parameters increase computational complexity
Solution Approach 1:
The patent introduces torque share ratios as a simplified parameter representation for torque exchange control. Instead of independently controlling multiple torque parameters, the system uses torque shares (ratios between engaged-side and released-side clutch torques) to manage torque exchange. This parameter transformation reduces computational complexity by providing a direct relationship between control inputs and torque distribution, making the control system more manageable despite the additional degree of freedom.
Data Source
AI summary
Torque shares that express an exchange of torque are set as a constraint condition of an equation of motion of an automatic transmission, so it is suitable to control an exchange of torque between engagement devices, which is difficult in shift control, and it is possible to solve the equation of motion. In other words, it is possible to handle any shift pattern with the use of a predetermined shift model. Furthermore, at the time of a shift in which two elements are released and two elements are engaged, a first shift and a second shift in each of which one element is released and one element is engaged are carried out, so three control operation amounts are used in each of the first shift and the second shift, with the result that it is possible to solve the equation of motion.