Vehicle Transmission Control for Deceleration Tie-Up Prevention
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Solution Overview
Problem
Vehicle transmissions face challenges in accurately determining deceleration forces, leading to potential tie-ups where a clutch is partially applied when it should not be, causing unintended deceleration, as existing systems only consider measured longitudinal deceleration without accounting for other forces like engine torque, braking, aerodynamic drag, and road load.
Innovation Solution
A transmission control system that estimates longitudinal acceleration based on engine torque, braking force, aerodynamic drag, and road load force, and adjusts transmission fluid pressure to shift to neutral or a predetermined gear ratio when measured deceleration is negative and the estimated deceleration is greater, identifying and correcting tie-ups by actuating control valves to manage clutch engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the transmission control system only considers measured longitudinal deceleration, then the control system is simple, but it cannot accurately determine deceleration forces leading to tie-ups where clutch is partially applied
Solution Approach 1:
The patent segments the deceleration force determination into multiple independent components: engine torque force, braking force, aerodynamic drag force, and road load force. Each component is calculated separately based on specific parameters (engine torque, brake pressure, vehicle speed, vehicle mass) and then summed to obtain the total estimated deceleration force. This segmentation improves measurement precision while keeping each individual calculation simple and manageable.
Solution Approach 2:
The control system performs multiple functions using the same control module: it calculates engine torque force from engine torque signals, determines braking force from brake pressure and vehicle speed, computes aerodynamic drag from vehicle speed, calculates road load from vehicle mass and speed, and compares measured versus estimated deceleration. This multi-functionality approach improves measurement precision without proportionally increasing device complexity.
2Reliability
If the system shifts to neutral during coasting, then unwanted clutch engagement is prevented, but transmission control complexity increases
Solution Approach 1:
The control system performs preliminary calculation of estimated deceleration force by summing all deceleration components (engine torque, braking, aerodynamic drag, road load) before making the gear shift decision. This preliminary action allows the system to accurately predict whether the vehicle is coasting without actual driver braking intent, enabling reliable distinction between coasting and braking conditions before executing the neutral shift, thereby improving clutch engagement accuracy.
Solution Approach 2:
The system continuously compares the measured longitudinal deceleration (from sensors) with the estimated deceleration (calculated from vehicle parameters and forces). This feedback mechanism provides reliable verification of coasting conditions, ensuring that neutral shifts occur only when appropriate, thereby improving clutch engagement accuracy while using a straightforward comparison logic that does not excessively increase control complexity.
Data Source
AI summary
A transmission control system of a vehicle includes an estimated acceleration module and a pressure control module. The estimated acceleration module determines an estimated longitudinal acceleration of the vehicle based on a force at axles of the vehicle corresponding to engine torque, a braking force imposed by mechanical brakes of the vehicle, an aerodynamic drag force of the vehicle, and a road load force imposed on the vehicle by contact between tires of the vehicle and a road surface. The pressure control module, when a measured longitudinal acceleration of the vehicle is negative and the estimated longitudinal acceleration is greater than the measured longitudinal acceleration of the vehicle, adjusts transmission fluid pressure applied to one or more clutches of the transmission and shifts the transmission to neutral.