Vehicle Torque Shaping for Driveline Backlash Mitigation
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Solution Overview
Problem
Vehicle drivetrains experience disturbances such as clunk and shuffle due to backlash and lash transitions, which existing technologies fail to mitigate effectively, leading to noise, vibration, and harshness issues.
Innovation Solution
A control system that shapes driver-demanded torque by using a multivariate switched control system, switching between contact and lash modes, and applying specific torque profiles to manage transitions and reduce abrupt torque changes, incorporating a pre-compensator and feedback controller to optimize drivetrain responsiveness and reduce noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If driver-demanded torque is applied directly to the actuator, then the vehicle responds quickly to driver input, but clunk and shuffle disturbances occur due to backlash and lash transitions in the drivetrain
Solution Approach 1:
The controller applies preliminary torque shaping actions before the drivetrain exits lash mode. When the drivetrain is detected to be in lash mode, the controller commands a first torque to the actuator that is less than the driver-demanded torque, then upon exiting lash mode, commands a second torque greater than driver-demanded torque to create a temporary overshoot. This preliminary action prevents the abrupt torque changes that cause clunk and shuffle while maintaining quick response.
Solution Approach 2:
The controller dynamically adjusts the torque command based on the drivetrain's operating mode (lash mode vs. contact mode). The system switches between different torque shaping strategies: during lash mode, it applies reduced torque to avoid impact, and upon exiting lash mode, it applies increased torque to compensate for the delay and maintain responsiveness. This dynamic adaptation resolves the contradiction between quick response and disturbance mitigation.
2Object-generated harmful factors
If torque is reduced during lash mode transitions, then clunk and shuffle are mitigated, but drivetrain responsiveness to driver input is reduced
Solution Approach 1:
The controller implements periodic torque adjustment with three distinct phases: (1) during lash mode, command reduced torque to mitigate disturbances; (2) upon exiting lash mode, command increased torque to create temporary overshoot; (3) after the overshoot duration, command torque equal to driver-demanded torque. This periodic action sequence ensures both disturbance mitigation and maintained responsiveness.
Solution Approach 2:
The controller continuously monitors drivetrain operating conditions to detect when the drivetrain enters or exits lash mode. Based on this feedback, it dynamically adjusts the torque command strategy. The feedback mechanism enables the system to know when to apply reduced torque versus when to apply the compensating overshoot torque, ensuring responsiveness is maintained while disturbances are mitigated.
3Object-generated harmful factors
If complex torque shaping control is implemented, then clunk and shuffle are effectively reduced, but control system complexity increases
Solution Approach 1:
The controller acts as an intermediary between the driver's torque demand and the actuator. It introduces a torque shaping layer that processes the driver-demanded torque through predefined shaping logic based on drivetrain mode detection. This intermediary approach effectively reduces clunk and shuffle by modifying the torque profile without requiring complex hardware changes or sophisticated control algorithms, thus managing complexity while achieving disturbance mitigation.
Data Source
AI summary
A vehicle includes an actuator, a drivetrain configured to receive mechanical power from the actuator, an accelerator pedal position sensor configured to output a driver-demanded torque, and a controller in electric communication with the sensor and the actuator. The controller is programmed to receive the driver-demanded torque and output a shaped torque command to mitigate driveline disturbances caused by backlash and shaft compliance.