Adaptive Driveline Lash Estimation for Hybrid Powertrains
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Solution Overview
Problem
Hybrid vehicle powertrains experience clunks and jerks due to driveline lash, which affects vehicle operation and durability, as existing technologies fail to accurately estimate and manage driveline lash variations caused by build variations and wear over time.
Innovation Solution
A method and apparatus for determining driveline lash in hybrid vehicle powertrains, involving monitoring driver commanded torque and transmission output acceleration to calculate the total lash estimate, updating the adaptive lash estimate based on time differences, and managing lash closure rates to prevent harsh take-ups and clunks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If driveline lash is allowed to exist for build variation and thermal expansion, then component durability is improved, but clunks and jerks occur during torque transitions
Solution Approach 1:
The control system performs preliminary action by anticipating torque transitions and proactively managing driveline lash before clunks occur. The system monitors torque sign changes and pre-adjusts torque application to minimize impact when gears re-engage after passing through the zero torque point, thereby preventing harmful clunks while maintaining necessary lash for durability
Solution Approach 2:
The system implements feedback by continuously monitoring driveline torque, transmission output acceleration, and lash state. This feedback loop enables real-time detection of lash take-up events and allows the control system to dynamically adjust torque management strategies to minimize clunks and jerks while maintaining appropriate lash clearance
2Device complexity
If fixed driveline lash estimates are used, then control simplicity is maintained, but accuracy deteriorates due to build variations and wear over time
Solution Approach 1:
The system applies dynamics by transitioning from fixed, static driveline lash estimates to dynamic, adaptive estimates that evolve over time. The control system continuously updates lash estimates based on observed driveline behavior, acceleration patterns, and torque transitions, allowing the system to adapt to build variations and wear while maintaining reasonable control complexity through algorithmic automation
Solution Approach 2:
The system implements self-service by automatically monitoring and updating its own driveline lash estimates without requiring external calibration or manual adjustment. The control system uses its existing sensors and processors to autonomously learn and adapt to the specific driveline characteristics of each vehicle, eliminating the need for complex external calibration procedures
3Speed
If driveline lash is taken up quickly during torque reversal, then response time is improved, but harsh impacts and clunks increase
Solution Approach 1:
The system applies periodic action by using oscillatory torque modulation during lash closure events. When driveline lash is detected, the control system applies periodic torque variations that gradually close the lash gap through controlled oscillations rather than abrupt single-action closure, reducing impact severity while maintaining acceptable response time
Solution Approach 2:
The system implements beforehand cushioning by applying damping torque before driveline components impact during lash take-up. The control system detects approaching lash closure and pre-applies cushioning torque to reduce the relative velocity and impact force when gears re-engage, thereby minimizing harsh clunks while maintaining reasonable lash closure speed
Data Source
AI summary
An improved method and apparatus for estimating driveline lash in a vehicle powertrain is provided herein. The method includes: determining if the powertrain is transitioning through driveline lash, e.g., driver commanded torque value changes sign, and then stays between a minimum and maximum commanded torque threshold for a calibrated time; if the powertrain is transitioning through driveline lash, determining when the driveline lash is taken up, e.g., when the transmission output acceleration exceeds a threshold minimum output acceleration, and thereafter changes sign; determining when the estimated lash state changes from neutral to a positive or negative state, which may be inferred from the axle torque estimate behavior; determining the time difference between when the driveline lash is taken up and when the estimated lash state changes from neutral to a positive or negative state; and updating the adaptive lash estimate if the aforementioned time difference is not equal to zero.