Driveline Lash Control via Torque Rate Limiting
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Solution Overview
Problem
In hybrid vehicles, controlling driveline lash during torque changes is complex due to multiple prime movers and varying operational modes, leading to disturbances for the driver, such as noise, vibration, and reduced fuel efficiency.
Innovation Solution
A control system that adjusts traction motor torque and driveline input torque to limit the rate of change of output torque during torque reversals, using a ramp or filter function to manage lash zones, with the engine and electric machine controlled based on operational mode and torque direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a slow ramp on engine torque is used when crossing the lash zone, then driveline lash is reduced, but response time and productivity deteriorate
Solution Approach 1:
The torque control is segmented into different phases: a first torque level is applied before crossing the lash zone, a second reduced torque level is applied during lash zone crossing, and a third torque level is applied after crossing. This segmentation allows the system to reduce lash effects during the critical transition period while maintaining faster overall response compared to a uniform slow ramp approach.
Solution Approach 2:
The controller dynamically adjusts the torque level based on the real-time position relative to the lash zone. By detecting when the driveline enters and exits the lash zone and adjusting torque accordingly, the system achieves effective lash control with improved response time compared to static or uniformly slow torque application.
2Object-affected harmful factors
If spark retard within the engine is used to reduce lash, then driveline lash is reduced, but fuel efficiency deteriorates and torque loading increases
Solution Approach 1:
The controller preliminarily reduces the torque level before and during the lash zone crossing event, preventing the need for spark retard. This preliminary torque reduction achieves lash control while avoiding the fuel efficiency penalties and increased torque loading associated with spark retard methods.
3Object-affected harmful factors
If traction motor torque is controlled through a region surrounding vehicle wheel torque reversal, then driveline lash is reduced, but device complexity increases
Solution Approach 1:
The controller uses feedback from wheel torque reversal detection to dynamically adjust traction motor torque. By monitoring the torque reversal event and automatically responding with appropriate torque levels, the system achieves effective lash control through a relatively simple feedback-based control logic rather than complex open-loop scheduling.
Data Source
AI summary
A hybrid electric vehicle has a traction motor, a driveline connected to a vehicle wheel, and a controller. The controller is configured to control motor torque through a region surrounding vehicle wheel torque reversal, control driveline input torque during torque reversal of driveline output torque to limit rate of change of driveline output torque, and control motor torque during a torque reversal of at least one driveline component to limit rate of change of the torque applied to the driveline component. A method for controlling a vehicle having a traction motor includes controlling the traction motor torque through a region surrounding a vehicle wheel torque reversal, controlling driveline input torque during torque reversal of driveline output torque to limit rate of change of output torque, and controlling traction motor torque during a torque reversal of a powertrain component to limit rate of change of the torque applied to the component.