Powertrain Torque Control for Smooth Transmission Shifts
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Solution Overview
Problem
Existing powertrain systems face challenges in accurately matching engine speed and torque with transmission speed and torque during shifts, leading to potential sag in vehicle speed or torque output and clutch slippage, due to inaccuracies in predicting and managing crankshaft torque requests.
Innovation Solution
A powertrain system that activates an immediate response mode during transmission shifts, controlling engine torque and motor torque of the torque machine to achieve a predicted engine torque command, determining an arbitrated predicted motor torque, and operating the transmission based on a possible crankshaft torque to ensure smooth shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If known control systems reduce engine torque during upshift to minimize clutch wear, then clutch wear is reduced, but engine speed matching accuracy deteriorates causing transmission shift inaccuracies
Solution Approach 1:
The system calculates a target engine torque value in advance based on the current transmission gear ratio and the target gear ratio before the shift occurs. This pre-calculated torque value guides the torque reduction process during the upshift, ensuring that engine speed matches the transmission output speed at the target gear ratio, thereby maintaining both clutch protection and shift accuracy
Solution Approach 2:
The control system continuously monitors actual engine torque and compares it with the target engine torque during the upshift process. Based on this feedback, the system adjusts the engine torque in real-time to achieve accurate engine speed matching with the transmission, preventing both excessive clutch wear and shift inaccuracies
2Power
If known control systems increase engine torque at completion of upshift to achieve constant axle torque, then axle torque constancy is improved, but transmission shift smoothness deteriorates due to torque management inaccuracies
Solution Approach 1:
The system pre-calculates the target engine torque value based on the relationship between current and target gear ratios before the upshift completes. This advance preparation ensures that when the shift occurs, the engine torque can be smoothly adjusted to maintain constant axle torque, preventing rough shifts and improving transmission shift smoothness
Solution Approach 2:
The control system uses feedback from actual engine torque measurements to continuously adjust torque management during and after the upshift. This real-time adjustment ensures smooth transition while maintaining constant axle torque, resolving the contradiction between power delivery and shift smoothness
3Speed
If known driver interpretation systems use immediate crankshaft torque requests for fast actuator control, then response speed is improved, but torque control accuracy deteriorates due to disabled immediate requests under most driving situations
Solution Approach 1:
The system pre-calculates the target engine torque value based on transmission shift parameters and gear ratio relationships before the upshift occurs. This pre-computed torque target serves as an accurate reference that enables both fast response through immediate torque requests and high precision through the pre-planned torque trajectory
Solution Approach 2:
The system dynamically adjusts the torque control strategy by transitioning between different torque request modes during the upshift process. Immediate crankshaft torque requests are used during critical shift phases for fast response, while predicted torque requests are used for steady-state control, optimizing both response speed and control accuracy throughout the shift event
Data Source
AI summary
A method for operating a powertrain system including a torque machine coupled to an internal combustion engine that is coupled to a transmission includes, upon commanding a shift in a transmission operating range, activating an immediate response mode to effect the shift. Activating the immediate response mode includes controlling the engine to achieve a predicted engine torque command, and controlling motor torque of the torque machine in response to a difference between an actual engine torque and an immediate crankshaft torque for shift command. An arbitrated predicted motor torque is determined. A possible crankshaft torque is determined in response to the arbitrated predicted motor torque and the predicted engine torque command. Operation of the transmission at the end of the shift event is commanded in response to the possible crankshaft torque. A predicted response mode is activated to complete the shift in the transmission operating range.