Torque Request Rate Limiting for Driveline Clunk Mitigation
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Solution Overview
Problem
Conventional vehicle control systems fail to effectively mitigate powertrain and driveline clunk caused by accelerator pedal tip-in and tip-out events, as they often resort to spark retardation, which increases exhaust gas temperature and negatively affects emissions and fuel economy.
Innovation Solution
A control system that utilizes a pedal position sensor and controller to detect pedal events and gradually transition the torque generating system's output torque, employing variable valve control or individual cylinder open-loop fuel control to minimize abrupt gear contact, thereby reducing clunk without harming the catalytic converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spark retardation is used to reduce engine torque and generate torque reserve, then clunk mitigation is achieved, but exhaust gas temperature increases causing negative effects on catalytic converter life, emissions, and fuel economy
Solution Approach 1:
The patent changes the control parameter from spark retardation to direct torque request rate limiting. By controlling the rate of change of the torque request signal rather than using spark timing adjustment, the system achieves clunk mitigation during pedal tip-in/tip-out events without increasing exhaust gas temperature, thereby preserving catalytic converter life and fuel economy while reducing harmful vibrations and noises
Solution Approach 2:
The patent replaces the combustion-based torque control mechanism (spark retardation) with an electrical control signal approach (torque request rate limiting). By substituting the mechanical/thermal control method with an electrical signal control method, the system achieves the same clunk mitigation effect without the harmful thermal side effects on the exhaust system
2Speed
If instantaneous torque request is commanded in response to pedal tip-in or tip-out events, then responsiveness is improved, but clunk is caused due to abrupt gear teeth contact
Solution Approach 1:
The patent implements dynamic control of the torque request signal by adjusting its rate of change based on detected pedal tip-in or tip-out events. The controller dynamically limits the slope of torque request changes during these specific transient conditions, allowing rapid torque response under normal operation while preventing abrupt changes that cause clunk during pedal transitions
Solution Approach 2:
The patent detects pedal tip-in or tip-out events in advance and preemptively applies torque request rate limiting before abrupt gear teeth contact occurs. By identifying the pedal transition event and pre-applying the control strategy, the system prevents clunk before it happens rather than reacting after the damage is done
Data Source
AI summary
A control system and method for a vehicle having a powertrain comprising a torque generating system and an automatic transmission each utilize a pedal position sensor configured to measure a position of an accelerator pedal of the vehicle and a controller configured to, based on the accelerator pedal position, detect a pedal tip-in or tip-out event and, in response to detecting the pedal tip-in or tip-out event: (i) determine a desired output torque for the torque generating system corresponding to the pedal tip-in or tip-out event and (ii) command the torque generating system to gradually transition, over a period, from its current output torque to the desired output torque to mitigate clunk caused by abrupt contact between gear teeth of the torque generating system shaft and the automatic transmission shaft.