Hybrid Engine Start Torque Pulse Cancellation
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Solution Overview
Problem
Hybrid powertrain systems experience objectionable vibrations and noise during engine start due to compression torque pulses, which overwhelm feedback damping control systems and disturb engine output torque.
Innovation Solution
A method that monitors operator torque requests, determines output torque commands, estimates cylinder pressure, predicts cylinder pulse torque, and controls motor torque output from a second torque machine to cancel the predicted pulse torque, thereby reducing vibrations and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the internal combustion engine is started in a hybrid powertrain system, then the engine can provide torque to the transmission, but compression torque pulses generate objectionable vibrations and noise that overwhelm feedback damping control systems
Solution Approach 1:
The control system applies preliminary anti-action by commanding the torque machine to generate a cancellation torque that is equal in magnitude and opposite in direction to the predicted compression torque pulse before the pulse occurs. This proactive counteracting torque neutralizes the harmful vibrations and noise generated during engine compression strokes, allowing the engine to provide power while eliminating the harmful effects.
Solution Approach 2:
The control system employs feedback by continuously monitoring engine crank angle, estimating cylinder pressure based on crank angle, predicting compression torque pulses, and adjusting the torque machine's cancellation torque in real-time. This closed-loop feedback mechanism ensures the cancellation torque accurately counteracts the varying compression pulses throughout engine operation.
2Object-affected harmful factors
If feedback damping control systems are used to reduce vibrations, then some vibration mitigation is achieved, but the compression torque pulses are sufficiently great to overwhelm the feedback damping control systems
Solution Approach 1:
The control system performs preliminary action by calculating and applying the cancellation torque before the compression torque pulses occur. By anticipating the pulse timing based on engine crank angle and preparing the appropriate counteracting torque in advance, the system prevents the harmful vibrations from occurring in the first place, rather than attempting to dampen them after they occur.
3Object-generated harmful factors
If the engine is operated unfueled during spinning, then combustion is avoided, but compression torque pulses are still generated that disturb engine output torque
Solution Approach 1:
The control system converts the harmful compression torque pulses into a beneficial situation by using the torque machine to both spin the unfueled engine and simultaneously generate cancellation torque. The engine compression process, which would normally create harmful vibrations, becomes an opportunity to demonstrate the effectiveness of the active cancellation system while the engine prepares for fueled operation.
Data Source
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AI summary
A hybrid powertrain system includes an internal combustion engine (14) operatively connected to a second torque machine (72) to transmit torque to an output member (64). A method for operating the hybrid powertrain system includes monitoring an operator torque request, determining an output torque command based upon the operator torque request, commanding a transition between an engine-off state and an engine-on state, monitoring an engine crank angle, spinning the engine unfueled, estimating cylinder pressure based upon the engine crank angle during the spinning of the engine (14), predicting a cylinder pulse torque based upon the cylinder pressure, determining a cancellation torque for the second torque machine (72) based upon the predicted cylinder pulse torque, and controlling motor torque output from the second torque machine (72) based upon the cancellation torque and the output torque command.