Electric Vehicle Creep Cutoff Control Device

Solution Overview

Problem

Existing creep cutoff control devices for electric vehicles unexpectedly reduce creep torque to zero, causing unintended torque reduction and discomfort for drivers when adjusting vehicle speed at low speeds, due to unconditional execution of creep cutoff based on predetermined conditions.

Innovation Solution

A creep-cutoff control device that prohibits creep cutoff when the vehicle speed is within a predetermined low-speed region, using a creep-cutoff-prohibiting speed-region judging means and a timer to prevent torque reduction unrelated to driver manipulation, ensuring creep torque continues to be outputted even if creep-cutoff permitting conditions are met.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If creep cutoff is executed unconditionally when predetermined conditions are satisfied, then power consumption is suppressed and creep torque is reduced to zero, but unintended torque reduction occurs causing driver discomfort when adjusting vehicle speed at low speeds

Engineering Contradiction:

Improvepower consumptionVSAvoiddriver comfort

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The patent applies local quality by distinguishing between different low-speed regions: a first low-speed region (0 to first threshold) where creep cutoff is prohibited to maintain driver comfort, and a second low-speed region (below second threshold) where creep cutoff is permitted for power savings. This localized differentiation resolves the contradiction by applying different control strategies to different speed ranges.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the control parameter (creep cutoff execution) based on the vehicle speed parameter. By monitoring vehicle speed and comparing it against threshold values, the system dynamically adjusts whether creep cutoff is executed, thereby balancing power consumption reduction with driver comfort across different operating conditions.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If creep cutoff is prohibited in low-speed region, then driver comfort is maintained by preventing unintended torque reduction, but power consumption is increased compared to unconditional creep cutoff

Engineering Contradiction:

Improvedriver comfortVSAvoidpower consumption

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent applies local quality by distinguishing between different low-speed regions: a first low-speed region (0 to first threshold) where creep cutoff is prohibited to maintain driver comfort, and a second low-speed region (below second threshold) where creep cutoff is permitted for power savings. This localized differentiation resolves the contradiction by applying different control strategies to different speed ranges.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the control parameter (creep cutoff execution) based on the vehicle speed parameter. By monitoring vehicle speed and comparing it against threshold values, the system dynamically adjusts whether creep cutoff is executed, thereby balancing power consumption reduction with driver comfort across different operating conditions.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If creep cutoff is executed when braking force satisfies predetermined condition, then creep torque is reduced to zero for power savings, but torque reduction occurs unrelated to driver manipulation causing feeling of strangeness

Engineering Contradiction:

Improvepower consumptionVSAvoidcontrol predictability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies local quality by distinguishing between different low-speed regions: a first low-speed region (0 to first threshold) where creep cutoff is prohibited to maintain driver comfort, and a second low-speed region (below second threshold) where creep cutoff is permitted for power savings. This localized differentiation resolves the contradiction by applying different control strategies to different speed ranges.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses feedback by continuously monitoring vehicle speed and using this information to determine whether creep cutoff should be executed. The speed feedback mechanism ensures that creep cutoff only occurs when it will not conflict with driver intentions, thereby maintaining control predictability while still achieving power savings when appropriate.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP2589509B1Creep cut-off control device for electric vehicle

Publication Date: 2019.04.17 NISSAN MOTOR CO LTD

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AI summary

A vehicle speed VSP enters a creep-cutoff-prohibiting speed region lower than V1 with a forward creep torque being outputted (t1), and then this state continues for a time duration set corresponding to a timer value NTM1 (t2). At this time, a creep cutoff is prohibited by setting a creep-cutoff-prohibition flag NFLAG at "1". A braking force becomes larger than or equal to a creep-cutoff-permitting braking-force value to satisfy a creep-cutoff permitting condition related to the braking force (t3) while a creep-cutoff permitting condition related to the vehicle speed has been satisfied because of almost zero of the vehicle speed VSP. In response thereto, the creep-cutoff permitting flag FLAG is set at 1 at t4. However, the creep toque continues to be outputted also after t4 without the creep cutoff, so that a torque reduction accompanied with strangeness feeling can be prevented from occurring due to an execution of the creep cutoff at t4.