Hybrid EV Speed Limit Control to Prevent Shift Overshoot
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Solution Overview
Problem
Hybrid electric vehicles experience unnecessary shifting and overshoot when applying a speed limit function due to the selective application of shifting patterns with different efficiency characteristics, making it difficult to maintain the target speed and satisfy assessment criteria like those of EURO NCAP.
Innovation Solution
A method for controlling the speed limit in hybrid electric vehicles involves determining a virtual vehicle speed and virtual APS value, transitioning between modes based on expected changes in these values, and adjusting transmission gear positions using specific shifting patterns to prevent excessive shifting and overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If shifting patterns are selectively applied based on driving modes in hybrid electric vehicles, then fuel efficiency is improved, but unnecessary shifting and overshoot occur when speed limit function is applied
Solution Approach 1:
The control method performs preliminary actions by determining whether mode transition is expected before it actually occurs. When the controller predicts that a mode transition will happen, it proactively determines a gear position based on the current shifting pattern rather than waiting for the transition to occur, thereby preventing unnecessary shifting and overshoot while maintaining fuel efficiency benefits of selective shifting pattern application.
2Power
If mode transition is performed in hybrid electric vehicles, then power performance is improved, but frequent shifting occurs making it difficult to maintain target speed
Solution Approach 1:
The control method implements feedback by continuously monitoring the relationship between virtual accelerator position sensor values and actual accelerator position sensor values to detect expected mode transitions. When such transitions are detected, the system adjusts gear position determination accordingly, providing feedback control that prevents frequent shifting and enables accurate maintenance of target speed while preserving power performance benefits.
Data Source
AI summary
Controlling a speed limit includes determining a virtual vehicle speed as being a lower one of a vehicle speed and a target limit speed, determining a virtual APS value as being a larger one of a first APS value and a second APS value, transitioning to a second mode at a point in time at which an actual APS value and the second APS value become different, when it is expected to transition to the second mode, among a first mode for sustaining a SOC of a battery at the target limit speed and the second mode for depleting the SOC, and determining a transmission gear position by applying the determined virtual vehicle speed and the determined virtual APS value to one of a first shifting pattern and a second shifting pattern.