Hybrid Vehicle Creep Control via Torque Converter Feedforward

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Solution Overview

Problem

Hybrid-electric vehicles face challenges in replicating the immediate propulsion associated with conventional vehicles' creep control, as they typically turn off the electric machine when stopped, leading to delays in spin-up to turbine-stall speed, which affects the driving experience due to jerky torque and noticeable delays.

Innovation Solution

Implementing a control strategy that combines feedforward and feedback components to control the torque applied to the impeller, using predetermined feedforward torques adjusted by feedback torque based on the difference between target and actual speeds to quickly and accurately spin-up the impeller to idle speed, reducing delays and jerky torque.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the electric machine is turned off when stopped to preserve battery state of charge, then energy consumption is reduced, but the spin-up delay and jerky torque occur affecting driving experience

Engineering Contradiction:

Improvebattery state of chargeVSAvoidspin-up delay

Core Design Contradiction:

Use of energy by moving objectVSLoss of time

Solution Approach 1:

The system applies a predetermined feedforward torque to the impeller before the vehicle actually needs to move, preparing the torque converter in advance. When creep control is requested, the impeller is already primed and can spin up immediately without delay, eliminating the spin-up lag while still allowing the electric machine to remain off during complete stops.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control system continuously monitors the difference between actual and target impeller speeds, applying a feedback torque component that adjusts the feedforward torque in real-time. This feedback mechanism ensures the impeller reaches the target speed accurately and smoothly, eliminating jerky torque while maintaining rapid response.

Inventive Principle:

Principle #23Feedback

2Use of energy by moving object

If the electric machine is turned off when stopped, then energy consumption is reduced, but the driving experience deteriorates due to jerky torque

Engineering Contradiction:

Improvebattery state of chargeVSAvoiddriving experience

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The feedback component continuously monitors the speed difference between actual and target impeller speeds, adjusting the torque application in real-time to eliminate jerky behavior. This ensures smooth torque delivery and natural-feeling creep control while keeping energy consumption low.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts the torque application based on real-time conditions, transitioning from a static on/off control to a dynamic feedforward-feedback control system that adapts to the specific operating conditions, providing smooth and natural driving experience.

Inventive Principle:

Principle #15Dynamics

3Speed

If conventional creep control is implemented in hybrid vehicles, then immediate propulsion is achieved, but it compromises battery state of charge

Engineering Contradiction:

Improvepropulsion response speedVSAvoidbattery state of charge

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

By applying predetermined feedforward torque to the impeller in advance, the system prepares the torque converter for immediate propulsion when needed, achieving conventional creep control response characteristics without requiring the electric machine to remain continuously on during stops.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system replaces the traditional mechanical engine idle torque with an electrically-controlled feedforward torque system, allowing precise control of impeller torque without the continuous energy consumption associated with keeping the electric machine running during stops.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach reduces the delay in achieving hydrodynamic coupling and provides a smoother driving experience by quickly accelerating the impeller to turbine-stall speed, mimicking conventional creep control without compromising the battery state of charge.

Implementation Method 1

an electric machine configured to provide drive torque to the impeller

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Implementation Method 2

achieving hydrodynamic coupling

Methodology Applied

Scientific EffectHydrodynamic coupling:

Data Source

PatentUS10308138B2Hybrid electric vehicle creep control

Publication Date: 2019.06.04 FORD GLOBAL TECH LLC

AI summary

A vehicle includes an engine, and a transmission including a torque converter having an impeller. The vehicle further includes an electric machine configured to provide drive torque to the impeller. The impeller is selectively coupled to the engine via a clutch. At least one vehicle controller is configured to, in response to the engine being OFF, the transmission being in DRIVE, a vehicle speed being zero and a brake pedal being released beyond a threshold position, command the electric machine to provide a torque to the impeller. The torque is a predetermined feedforward torque adjusted by a feedback torque that is based on a difference between measured and calculated speeds. The speeds may be the speeds of the electric machine.