Hybrid Powertrain Torque Control for Engine Start Reserve

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Solution Overview

Problem

Hybrid powertrains face challenges in maintaining an adequate battery power reserve and torque capability to ensure smooth engine starts without significant reduction in output torque, particularly in charge-depleting and charge-sustaining modes.

Innovation Solution

A method of controlling the hybrid powertrain that determines the available battery power for tractive torque, calculates a power-based maximum output torque, and adjusts it based on stored test data and current operating conditions to minimize torque sag during engine starts, using a control system with a processor to manage the reduction in output torque.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If battery power is used to start the engine, then the engine can be started, but the available power for tractive torque is reduced

Engineering Contradiction:

Improveengine start capabilityVSAvoidavailable power for tractive torque

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The control system performs preliminary assessment of battery power reserve before engine start is initiated. It calculates the power required for engine start and compares it with available battery power, making preparatory decisions about torque reduction timing and magnitude to ensure sufficient power remains for both starting and tractive purposes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the output torque based on real-time battery power availability and engine start requirements. The torque reduction is not fixed but adapts to current operating conditions, allowing optimal power distribution between engine starting and vehicle propulsion at different moments.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If engine is started in charge-depleting mode, then powertrain can operate in electric-only mode, but battery power level decreases

Engineering Contradiction:

Improveelectric-only operating capabilityVSAvoidbattery power level

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The control system continuously monitors battery power level and uses this feedback to determine when engine starting should occur and how much torque reduction is appropriate. The feedback loop ensures that electric-only mode operation is maintained as long as sufficient battery power exists, while automatically transitioning to engine start when power thresholds are approached.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8565949B2Method of controlling a hybrid powertrain to ensure battery power and torque reserve for an engine start and hybrid powertrain with control system

Publication Date: 2013.10.22 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A method includes determining an amount of power currently available from a battery for tractive torque as an amount of power stored in the battery less an amount of power required to power other vehicle components, and less an amount of power required to start the engine. An output torque limit when torque is provided only by the motor and power required to provide the output torque limit are determined based on test data. A maximum output torque is calculated by multiplying the amount of power determined to be currently available for tractive torque by a ratio of the output torque limit to the amount of power required to provide the output torque limit. The current output torque may be reduced at a predetermined rate until within a predetermined range of the lesser of the maximum output torque and the output torque limit if an engine start is requested.