HEV Torque Band Management for Transient Fuel Economy

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Solution Overview

Problem

Hybrid electric vehicle (HEV) powertrains face challenges in managing rapid power demand changes, leading to adverse effects on fuel economy due to transient responses that deviate from optimal engine operation, and existing energy management strategies struggle to incorporate transient dynamics into calculations.

Innovation Solution

A method and system for managing transient operation in HEV powertrains, which includes determining a torque band for efficient engine operation across a range of speeds and generating an engine torque command. This system modifies the torque command to stay within the torque band, using a torque band determination unit and an arbitrator to ensure efficient operation during transients.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the powertrain operates in steady-state optimal settings, then fuel economy is optimized, but the system cannot respond to rapid power demand changes

Engineering Contradiction:

Improvefuel economyVSAvoidresponse speed to power demand changes

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The system pre-calculates and stores optimal engine torque values in lookup tables for various operating conditions. During transient operations, the controller quickly retrieves pre-computed optimal torque values based on current speed and power demand, avoiding the need for real-time optimization calculations while maintaining near-optimal fuel economy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts engine torque commands during transient operations by combining steady-state optimal torque from lookup tables with transient compensation terms. The control strategy adapts torque commands based on the rate of change of power demand, allowing the engine to respond rapidly while staying close to optimal operating points.

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If the engine torque command is strictly confined along a steady-state optimal path, then fuel economy is maximized, but control complexity increases and electrical re-circulation losses increase

Engineering Contradiction:

Improvefuel economyVSAvoidcontrol complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

Instead of strictly confining the engine to the optimal torque path, the system allows partial deviations from the optimal path during transient operations. The controller applies torque commands that are close to optimal but not necessarily exact, accepting small temporary efficiency losses to avoid complex real-time optimization and excessive electrical re-circulation.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system uses simple lookup tables with pre-computed torque values rather than complex real-time optimization algorithms. This approach sacrifices some precision in exchange for computational simplicity and faster response, effectively using 'cheap' pre-calculated solutions instead of 'expensive' real-time optimization.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Use of energy by moving object

If real-time optimization calculations are performed to determine global-optimal engine torque, then fuel economy is maximized, but computational intensity becomes extremely high

Engineering Contradiction:

Improvefuel economyVSAvoidcomputational power required

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

The system performs the computationally intensive optimization calculations offline before vehicle operation. Optimal torque values for various operating conditions are pre-computed and stored in lookup tables. During actual vehicle operation, the controller simply retrieves pre-computed values based on current speed and power demand, requiring minimal real-time computation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of performing real-time optimization calculations, the system uses copies of pre-computed optimal torque values stored in lookup tables. The controller retrieves these copied values based on current operating conditions, avoiding the need for expensive real-time mathematical optimization while maintaining near-optimal fuel economy.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS8473133B2Transient operation energy management strategy for a hybrid electric vehicle powertrain

Publication Date: 2013.06.25 FORD GLOBAL TECH LLC

AI summary

A method and system for providing a dynamic torque band for hybrid electric vehicle (HEV) transient management includes determining a torque band indicative of an engine torque operation region representing efficient operation of the powertrain across a range of engine speeds. An engine torque command based on an actual speed of the engine is generated. The engine torque command is outputted to the engine if the engine torque command is within the torque band. The engine torque command is modified to be within the torque band if the engine torque command is out of the torque band and the modified engine torque command is outputted to the engine.