Torque Converter Clutch Feed Forward Pressure Control
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Solution Overview
Problem
Existing torque converter control systems face challenges in efficiently managing slip between the engine and transmission, particularly during rapid throttle changes, leading to reduced fuel efficiency and undesirable drivability due to the limitations of feedback control methods which introduce lag and unpredictability.
Innovation Solution
A method that combines feed forward and feedback control to regulate torque converter slip by determining a feed forward torque converter clutch pressure command based on turbine torque, engine torque, and a TCC gain, using models like the Kotwicki model to predict and adjust slip, thereby reducing reliance on feedback control and minimizing excessive slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control methods are used to regulate torque converter clutch pressure, then the system can respond to slip conditions, but the control response is delayed and unpredictable due to inherent lag
Solution Approach 1:
The patent implements feed forward control that calculates and applies torque converter clutch pressure adjustments before slip conditions fully develop. By using a lookup table pre-calculated from torque converter models and current operating conditions (engine speed, turbine speed, throttle position), the system proactively compensates for anticipated slip rather than reacting to it, eliminating control lag and improving response reliability.
2Ease of operation
If torque converter clutch slip is allowed to increase during rapid throttle changes, then drivability is improved, but fuel efficiency deteriorates due to excessive slip
Solution Approach 1:
The patent dynamically adjusts the target slip value based on current operating conditions and throttle change rate. During rapid throttle changes, the system temporarily allows higher slip to maintain drivability, then quickly transitions to lower slip values for fuel efficiency. This dynamic adaptation is achieved through the feed forward control algorithm that continuously updates pressure commands based on real-time sensor inputs and pre-calculated lookup tables, optimizing the trade-off between drivability and fuel efficiency throughout the transient event.
3Measurement precision
If torque converter clutch pressure is rapidly adjusted to control slip, then slip control is improved, but the control system becomes unstable and may cause runaway slip
Solution Approach 1:
The patent incorporates damping and rate-limiting logic in the feed forward control algorithm to cushion against rapid pressure adjustments. The lookup table provides pre-calculated pressure commands that inherently smooth transitions, and the control algorithm applies incremental changes rather than abrupt jumps. This beforehand cushioning prevents control instability and runaway slip by anticipating and mitigating oscillations before they occur, maintaining both precision and stability during transient conditions.
Data Source
AI summary
A powertrain includes a torque generative device and a torque converter having an impeller, a turbine and a torque converter clutch. A method to control torque converter slip includes monitoring a reference slip and a turbine speed of the torque converter, determining a turbine torque based upon the reference slip and the turbine speed, determining a feed forward torque converter clutch pressure command based upon the turbine torque, a torque generative device torque, and a TCC gain, and controlling the torque converter clutch based upon the feed forward torque converter clutch pressure command.