EPB Hill Holding Control for Motor Output Derating

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Solution Overview

Problem

Electric vehicles face challenges in maintaining a hill holding state due to output derating of the inverter, leading to potential backward rolling and safety hazards, particularly on steep inclines, where the temperature increase of IGBT components limits motor output and requires complex control over oil pressure characteristics.

Innovation Solution

Implementing a brake cooperation control using an electronic parking brake (EPB) to manage hill holding conditions, comparing motor output with incline and temperature conditions, and applying EPB control to prevent backward rolling by limiting motor output and notifying the driver through a cluster lamp.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If output limitation is applied to restrain IGBT temperature increase, then the temperature of IGBT is protected from damage, but output derating occurs which may cause insufficient motor output for hill holding

Engineering Contradiction:

ImproveIGBT temperatureVSAvoidmotor output

Core Design Contradiction:

TemperatureVSPower

Solution Approach 1:

The patent introduces an electronic parking brake (EPB) as an intermediary system to assist hill holding when motor output is insufficient due to inverter output limitation. The EPB provides additional braking force to compensate for the reduced motor output, enabling the vehicle to maintain position on steep inclines without exceeding IGBT temperature limits.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If brake cooperation control using oil pressure is implemented for hill holding, then vehicle stability is improved, but control complexity increases due to difficulty in managing oil pressure reaction speed and request amount

Engineering Contradiction:

Improvevehicle stabilityVSAvoidcontrol system complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent replaces the traditional hydraulic oil pressure-based brake cooperation control with an electronic parking brake (EPB) system. The EPB uses an electric motor to generate braking force, eliminating the need for complex oil pressure management. This substitution simplifies the control system while maintaining vehicle stability during hill holding operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If motor output is limited due to inverter temperature constraints, then IGBT damage is prevented, but the vehicle may roll backward on steep inclines due to insufficient output

Engineering Contradiction:

ImproveIGBT reliabilityVSAvoidhill holding stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent merges the motor braking capability with the electronic parking brake (EPB) system to create a cooperative control mechanism. When inverter output limitation occurs, the EPB activates to provide additional holding force, ensuring the vehicle remains stable on steep inclines while the motor output is constrained to protect IGBT reliability.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS9463800B2Control method for motor-driven vehicle and control system thereof

Publication Date: 2016.10.11 HYUNDAI MOTOR CO LTD

AI summary

A control method for a motor-driven vehicle includes comparing a motor output with a hill holding condition on an inclined road. A hill holding fail safe is performed through a brake cooperation control when the motor output is less than the hill holding condition. Since the brake cooperation control for the hill holding fail safe is implemented by an electronic parking brake (EPB) motor control on a hill holding condition, convenience is provided without difficulty of control according to an oil pressure.