Hybrid Transmission Torque Control for Transition Speed Stability
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Solution Overview
Problem
Existing hybrid vehicle powertrain control systems face issues with temporary speed increases due to double counting of torque converter losses during transitions between coupled and decoupled states, which are difficult to address through conventional logic changes or additional message exchanges between controllers.
Innovation Solution
A powertrain control module (PCM) adjusts the feedforward torque value to include torque converter losses, allowing the hybrid powertrain control module (HPCM) to maintain e-motor torque within predefined bounds without requiring changes to the HPCM, thereby minimizing speed spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the feedforward torque value includes torque converter losses and the PID controller also compensates for torque converter losses, then the e-motor torque should accurately match engine torque, but temporary speed increases occur during transitions between coupled and decoupled states due to double counting of losses
Solution Approach 1:
The system performs preliminary action by setting the feedforward torque value to include torque converter losses before the transition occurs. This preliminary inclusion of loss compensation in the FF term prepares the system to maintain accurate speed matching while avoiding the need for the PID controller to add additional loss compensation during the transition, thereby preventing double counting and speed instability.
2Stability of the object's composition
If logic changes are made to both PCM and HPCM to prevent double counting of conversion losses, then speed stability during transition improves, but system complexity and development time increase
Solution Approach 1:
The solution extracts the torque converter loss compensation from the PID controller's feedback mechanism and places it entirely in the feedforward torque value calculated by the PCM. This extraction eliminates the need for coordinated logic changes in both controllers and removes the double counting issue by ensuring loss compensation occurs only once in the FF term.
3Measurement precision
If additional messages are communicated between PCM and HPCM to coordinate loss compensation, then double counting is prevented, but network communication complexity and implementation time increase
Solution Approach 1:
The solution merges the torque converter loss compensation function into the feedforward torque calculation performed by the PCM. By combining the loss compensation with the existing FF term calculation, the system eliminates the need for separate communication messages between controllers, reducing network complexity while maintaining accurate torque coordination.
Data Source
AI summary
Methods and systems are provided for operating a powertrain of a vehicle. In one example, the powertrain may include a first torque source, a second torque source, and an automatic transmission. The powertrain may further include a first controller configured to control the first torque source and a second controller configured to control the second torque source. The second controller stores instructions in non-transitory memory that when executed cause the second controller to command the first controller to control a torque of the first torque source via a feedforward torque value of the second torque source calculated at the second controller which is adjusted based on a degree of difference between a proximity term and a difference between the torque of the first torque source and a first torque source limit, the first torque source limit calculated at the second controller.