Feed Forward Torque Control for Engine Idle Speed Stability
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Solution Overview
Problem
Maintaining a stable engine idle speed during a garage shift in automatic transmission systems is challenging due to the varying and significant load applied by the transmission, which conventional methods, such as closed-loop feedback systems and calibrated timing, often fail to anticipate accurately, leading to engine speed sag or flare.
Innovation Solution
A feed forward control method that determines turbine speed changes and generates a torque command to adjust engine output torque based on these changes, ensuring a stable engine speed by identifying the moment the transmission load is applied and compensating before an engine speed sag occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional closed-loop feedback systems are used to maintain engine idle speed, then the system can respond to speed changes, but it fails to anticipate the transmission load accurately, leading to engine speed sag or flare
Solution Approach 1:
The system performs preliminary action by detecting turbine speed changes and generating feedforward torque commands before the transmission load is fully applied to the engine. The controller monitors turbine speed and predicts the impending load event, allowing the engine to prepare compensatory torque in advance, thus preventing speed sag before it occurs.
Solution Approach 2:
The system uses feedback by continuously monitoring turbine speed and comparing it to reference values. The detected turbine speed changes serve as feedback signals that trigger the feedforward control response, creating a closed-loop monitoring system that enables accurate detection and response to transmission load events.
2Reliability
If calibrated timing methods are used to anticipate transmission load, then the system can prepare in advance, but it requires extensive calibration and cannot adapt to varying conditions accurately
Solution Approach 1:
The system performs self-service by using the turbine speed sensor already present in the transmission system to detect load events. Rather than requiring external calibration inputs or additional complex sensing systems, the existing turbine speed data is utilized to trigger the feedforward control, making the system self-sufficient and eliminating extensive calibration requirements.
Solution Approach 2:
The system applies parameter changes by using real-time turbine speed measurements as the triggering parameter for feedforward control. Instead of relying on pre-calibrated timing schedules, the actual turbine speed parameter dynamically determines when compensation should be applied, allowing the system to adapt to varying operating conditions without recalibration.
3Reliability
If feed forward control based on turbine speed changes is implemented, then the system can anticipate transmission load and maintain stable engine speed, but it requires precise detection of turbine speed changes
Solution Approach 1:
The turbine speed acts as an intermediary parameter that mediates between the transmission load event and the engine control system. Rather than directly sensing engine load or speed changes, the system uses turbine speed as an intermediate indicator that precedes and predicts the actual load application, enabling early detection and feedforward compensation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively maintains a stable engine idle speed during garage shifts by precisely detecting the transmission load event and adjusting engine torque, reducing the need for calibration and preventing engine speed fluctuations.
Implementation Method 1
a hydraulic torque converter coupled between the internal combustion engine and the automatic transmission. The hydraulic torque converter includes a housing, a turbine, and an impeller or pump. The pump includes fins that are attached to the housing. The fluid is directed by the fins radially outwardly into fins on the turbine, which causes the turbine to spin.
Data Source
AI summary
A method of maintaining a substantially stable engine speed after a garage shift of an automatic transmission includes identifying a moment when a load from the automatic transmission is applied to an engine via a torque converter during the garage shift based on a first turbine speed change with respect to a reference engine speed change and a second turbine speed change with respect to an actual engine speed change. The method further includes generating a feed forward torque command based on a turbine speed decrement after identifying the moment when the load from the automatic transmission is applied to the engine, and controlling the engine based on the feed forward torque command to maintain a substantially stable engine speed after the garage shift.