Generator Lash Crossing Control in Hybrid Powersplit Vehicles
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Solution Overview
Problem
In hybrid powersplit vehicles, the transition of generator torque from negative to positive can cause backlash and clunk due to mechanical play in mating parts, which is challenging to address effectively due to complex power flows and multiple power inputs.
Innovation Solution
A method for managing lash crossing by limiting the increase in engine speed when generator torque approaches zero during selected conditions, applying an inertia-based rate clip to the engine speed command, thereby reducing the incidence of clunk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engine speed is increased rapidly to meet torque demand, then the power delivery response is improved, but generator lash crossing causes backlash and clunk due to mechanical play in mating parts
Solution Approach 1:
The control system performs preliminary detection of generator torque approaching zero and preemptively limits engine speed increase before lash crossing occurs. This preventive action avoids the harmful clunk and backlash effects by maintaining negative generator torque during driver tip-in conditions, rather than allowing the generator to cross into positive torque where mechanical play causes noise.
2Object-affected harmful factors
If torque shaping is applied to minimize clunk during lash crossing, then mechanical noise is reduced, but the complex power flows in powersplit powertrains make it difficult to identify the source and apply effectively
Solution Approach 1:
The invention extracts and addresses only the generator torque component as the source of lash crossing, rather than attempting to control all torque sources in the complex powersplit powertrain. By focusing specifically on maintaining negative generator torque during tip-in conditions, the solution simplifies the control approach while effectively reducing clunk, avoiding the complexity of comprehensive torque shaping across multiple power inputs.
Solution Approach 2:
The control strategy applies a localized solution by limiting engine speed increase specifically during conditions when generator torque approaches zero, rather than applying uniform torque shaping across all operating conditions. This targeted approach addresses the lash crossing problem in the specific region where it occurs (during driver tip-in with low engine torque) without complicating the overall powertrain control system.
3Object-affected harmful factors
If the generator torque is maintained negative during driver tip-in, then lash crossing is prevented, but engine speed increase is limited until more engine torque becomes available
Solution Approach 1:
The control system applies periodic or conditional limitation of engine speed increase only during the specific period when generator torque approaches zero, rather than continuously limiting engine speed. Once more engine torque becomes available and generator torque moves away from the zero-crossing region, the limitation is removed and normal engine speed increase resumes, providing a temporary controlled action rather than continuous restriction.
Data Source
AI summary
Methods and systems are provided for managing lash crossing in a hybrid powersplit vehicle. In one aspect, the method comprises, limiting an increase in engine speed in response to generator torque approach zero generator torque during selected conditions. In one example, the selected conditions comprise less than threshold driver pedal operation, non-engine startup conditions, emissions control, and greater than threshold battery state of charge.