Hybrid Vehicle Virtual Gear Ratio Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hybrid electric vehicles with continuously variable transmissions lack the ability to provide discrete gear ratios and associated torque multiplication, making it difficult for drivers to manually control engine speed and torque, unlike vehicles with discrete ratio transmissions.
Innovation Solution
A hybrid vehicle control strategy that implements four operating modes, including simulating discrete ratio transmission by controlling engine and traction motor speed to maintain preselected virtual gear ratios, allowing drivers to manually command powertrain speed and acceleration through shift selectors, and transitioning between continuously variable and discrete ratio modes based on driver input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a continuously variable transmission is used in a hybrid vehicle, then the transmission provides continuous speed variation and smooth operation, but it cannot provide discrete gear ratios with associated torque multiplication
Solution Approach 1:
The patent creates virtual gear ratios by controlling the engine and traction motor speeds to maintain predetermined speed ratios, copying the functional effect of discrete gear ratios without physical gear changes. This allows the CVT to simulate manual transmission behavior while maintaining continuous variability.
Solution Approach 2:
The system changes the operational parameters of the engine and traction motor to create different virtual gear ratios. By adjusting the speed ratios between these components, the system provides discrete-like gear effects while maintaining the flexibility of continuous variable transmission.
2Adaptability or versatility
If the transmission does not mechanically impose a strict relationship between engine speed and vehicle speed, then the hybrid vehicle gains operational flexibility, but the driver loses direct manual control over engine speed like in manual transmissions
Solution Approach 1:
The controller continuously monitors vehicle speed, engine speed, and traction motor speed, and adjusts the engine and motor operations to maintain the selected virtual gear ratio. This feedback mechanism enables the driver to control engine speed indirectly through vehicle speed control, similar to manual transmission behavior.
Solution Approach 2:
The system combines the benefits of both CVT (continuous variability) and discrete ratio transmissions (manual control) by implementing multiple operating modes including normal mode and select shift mode, allowing the transmission to function in different ways depending on driver preference.
3Productivity
If the controller automatically determines gear ratio or engine speed, then optimal fuel economy and performance are achieved, but drivers cannot override the controller for manual-like operation
Solution Approach 1:
The system dynamically switches between normal operating mode (automatic control for optimization) and select shift mode (manual-like control for driver preference). This dynamic adaptability allows the vehicle to optimize fuel economy when needed while providing driver control when desired.
Solution Approach 2:
The control system is divided into distinct operating modes with different control strategies. The normal mode handles automatic optimization, while the select shift mode handles manual-like operation, allowing each mode to excel at its specific function without compromise.
Data Source
AI summary
A hybrid vehicle and method of control are disclosed wherein the ratio of engine speed to vehicle speed varies continuously in some operating conditions and is controlled to be one of a finite number of preselected ratios in other operating conditions. The transition from continuously variable mode to discrete ratio mode includes selecting a virtual gear number and increasing the engine speed to the corresponding ratio to vehicle speed. Once in a discrete ratio mode, the virtual gear number can vary automatically in response to changes in vehicle speed or in response to driver activation of shift selectors.