Hybrid Vehicle Creep Torque Modeling for Gradient Consistency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hybrid vehicles experience inconsistent vehicle creep behavior when transitioning between engine-driven and electric-driven modes, affecting driver control and anticipation, especially on gradients.
Innovation Solution
A control system that uses a mathematical model of engine creep torque, simulated torque converter characteristics, and a synthetic vehicle creep function to control the electric traction motor, ensuring consistent vehicle behavior across modes by replicating torque converter behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the vehicle uses engine-driven torque converter creep, then the vehicle moves forward at constant speed on level ground, but the creep behavior varies on gradients and the vehicle may stall on up-slopes
Solution Approach 1:
The patent replaces the purely mechanical torque converter creep system with a hybrid system that uses an electric traction motor to supplement or replace engine torque. The controller monitors vehicle speed, engine torque, and gradient conditions to determine when electric motor assistance is needed, thereby maintaining consistent creep behavior across varying gradient conditions while preserving the natural torque converter creep characteristics on level ground.
Solution Approach 2:
The patent dynamically adjusts the torque contribution from the electric traction motor based on operating conditions such as gradient, vehicle speed, and engine torque availability. By changing the torque parameter of the electric motor in response to external conditions, the system maintains consistent creep speed and prevents stalling on up-slopes while preserving natural behavior on level ground.
2Use of energy by moving object
If the vehicle uses electric traction motor for creep, then fuel consumption and emissions are reduced, but the vehicle creep behavior differs from engine-driven creep
Solution Approach 1:
The patent uses the electric traction motor to copy or replicate the creep behavior characteristics of the engine-driven torque converter system. The controller is programmed to provide electric motor torque that mimics the torque curve and speed characteristics of natural torque converter creep, thereby maintaining consistent and predictable vehicle behavior that drivers can anticipate, while achieving the energy efficiency benefits of electric propulsion.
3Use of energy by moving object
If the torque path between engine and wheels is disconnected, then fuel efficiency is improved, but vehicle creep cannot be provided
Solution Approach 1:
The patent makes the electric traction motor universal by enabling it to perform multiple functions: it serves as the primary propulsion motor during electric driving mode, and simultaneously functions as a creep-providing device when the engine torque path is disconnected. The controller manages the electric motor to provide low-level torque sufficient for creep movement, thereby maintaining vehicle movement capability while preserving fuel efficiency benefits of disconnection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves vehicle composure and maintains consistent behavior regardless of the operating mode, allowing for smooth transitions and accurate replication of torque converter behavior, including automatic slowing or speeding on slopes.
Implementation Method 1
control the electric traction motor to provide tractive torque to a second set of vehicle wheels to automatically move the vehicle to provide electric vehicle creep
Implementation Method 2
The turbine and the impeller are coupled together by a fluid coupling. During engine idling with the vehicle on level ground, a lock-up clutch for eliminating slip between the impeller and the turbine is generally open. Therefore, the impeller rotates at engine idle speed, and the turbine is allowed to rotate at a slower speed or not rotate at all. The fluid coupling causes the engine-speed-dependent rotation of the impeller to impart a dragging torque on the turbine.
Data Source
Figure 1~2
Figure 3A~4
Figure 5A~5B
AI summary
The present invention relates to a control system and a method for controlling movement of a vehicle to provide vehicle creep, the vehicle comprising an engine and an electric traction motor, the control system comprising one or more controllers, wherein the control system is configured to: while a torque path between the engine and a first set of vehicle wheels is disconnected, control the electric traction motor to provide tractive torque to a second set of vehicle wheels to automatically move the vehicle to provide electric vehicle creep, wherein the electric vehicle creep is controlled by a mathematical model of engine creep torque that would be provided by the engine when the torque path between the engine and the first set of vehicle wheels is connected.