Hybrid Driveline Torque Shaping Across the Lash Zone
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Solution Overview
Problem
Hybrid electric vehicles experience vibrations and oscillations due to additional lash in the driveline, which reduces performance and comfort, and existing torque control methodologies introduce delays and non-linearities that are not suitable for electric vehicles.
Innovation Solution
A model-based control technique using a linear quadratic gaussian formulation, linear-switching model, and linear quadratic integral controller with gain scheduling, which estimates system states and generates torque commands to prevent oscillations, while minimizing computational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional torque control methodologies are used in hybrid electric vehicles, then the system structure is simple, but vibrations and oscillations occur due to additional driveline lash
Solution Approach 1:
The controller proactively identifies the lash zone in advance and requests motor torque to cross it before oscillations occur. This preliminary action prevents the harmful vibrations by addressing the root cause (lash) before it manifests as problematic oscillations, rather than reacting after the fact.
Solution Approach 2:
The control system dynamically adjusts torque commands based on real-time driveline state. The controller modifies torque requests to account for varying lash conditions, stiffness characteristics, and operating parameters, enabling adaptive suppression of vibrations across different driving scenarios.
2Object-affected harmful factors
If torque commands are shaped to cross the lash zone, then vibrations are reduced, but response time increases due to additional control processing
Solution Approach 1:
The controller pre-identifies the lash zone and prepares torque commands to cross it efficiently. By anticipating the lash zone location and preparing appropriate torque commands in advance, the system minimizes the time required to cross the lash zone while still preventing oscillations.
Solution Approach 2:
The control system adjusts torque command parameters dynamically based on driveline conditions. By modifying torque magnitude, rate of change, and timing parameters according to real-time lash and stiffness conditions, the system achieves rapid response while maintaining vibration suppression.
3Adaptability or versatility
If multiple electric motors are used in the driveline, then power distribution flexibility increases, but driveline lash and stiffness issues become more complex
Solution Approach 1:
The control system divides the driveline into separate controllable segments, with independent torque control for each electric motor. This segmentation allows the controller to manage lash and stiffness issues in each motor's torque path independently, simplifying the overall control complexity despite having multiple motors.
Solution Approach 2:
The controller applies a unified lash compensation strategy that works across multiple electric motors and different operating modes. The same fundamental control principles are used regardless of which motor is active or how torque is distributed, providing a universal solution that handles complexity through consistency.
Data Source
AI summary
An electrified powertrain that generates and transfers drive torque to a driveline of a hybrid electric vehicle includes a first electric motor, a second electric motor and a controller. The first electric motor includes a first electric motor output. The second electric motor includes a second electric motor output. The controller is configured to: receive a driver torque request; determine an open loop motor torque command based on the driver torque request; and determine a shaped torque command based on the open loop motor torque command, including identifying a lash zone, requesting motor torque from at least one of the first and second electric motors to cross the lash zone, and, subsequent to crossing the lash zone, providing motor torque to meet the driver torque request.