Hybrid Propulsion Torque Slew Rate Control
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Solution Overview
Problem
Hybrid electric vehicles face drivability issues due to lash crossings in the driveline, which cause undesirable noise, vibration, and harshness (NVH) due to sudden changes in torque output from multiple prime movers, making it challenging to manage lash events across powertrain components.
Innovation Solution
A vehicle propulsion system with an engine, electric motor, and integrated starter generator, controlled by a controller that sets torque slew rates to prevent simultaneous lash crossings across transmission, motor gearbox, and final drive units, ensuring each component undergoes lash at different times to manage torque allocation and minimize driveline excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multiple prime movers (engine and electric motor) are used to satisfy driver torque demand, then system efficiency and fuel economy are improved, but drivability deteriorates due to lash crossings causing noise, vibration, and harshness
Solution Approach 1:
The control system proactively manages torque slew rates before lash crossings occur by detecting lash conditions and adjusting torque allocation in advance. The controller monitors driveline state and preemptively modulates torque changes to prevent simultaneous lash crossings, thereby eliminating NVH issues before they manifest while maintaining the benefits of multiple prime movers
Solution Approach 2:
The system dynamically changes torque slew rate parameters based on detected lash conditions. When a lash crossing is detected in one prime mover, the controller adjusts the slew rate parameter of the other prime mover to prevent simultaneous lash events. This parameter modulation allows the system to maintain fuel efficiency while eliminating driveline excitation and associated NVH problems
2Object-affected harmful factors
If torque allocation changes suddenly to manage lash events, then drivability improves by reducing NVH, but system responsiveness to driver demands deteriorates
Solution Approach 1:
The control system dynamically adjusts torque slew rates in real-time based on detected lash conditions while maintaining overall responsiveness. Rather than using fixed torque allocation strategies, the controller continuously modulates torque changes adaptively, allowing rapid response to driver demands while preventing NVH-causing simultaneous lash crossings through dynamic slew rate management
3Stability of the object's composition
If torque slew rate is limited to prevent simultaneous lash crossings, then driveline excitation is reduced, but torque delivery speed deteriorates
Solution Approach 1:
The control system applies preliminary cushioning by detecting lash conditions and preemptively adjusting torque slew rates before simultaneous lash crossings occur. This advance intervention prevents driveline instability and NVH issues while maintaining acceptable torque delivery speed, as the system prepares torque modulation in advance rather than reacting to already-established instability
Data Source
AI summary
A vehicle propulsion system configured to generate wheel torque includes an engine arranged to output a first propulsion torque to a transmission and an electric motor arranged to output a second propulsion torque downstream of the transmission. The vehicle propulsion system also includes a controller programmed to, in response to detecting a lash crossing associated with one of the electric motor and the transmission, set a torque slew rate of the other one of the electric motor and transmission such that each of the electric motor and transmission undergoes lash crossings at different points in time.