Traction Motor Torque Limiting Before Brake Release Launch

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Solution Overview

Problem

Electric traction motors and associated power electronics are susceptible to overheating during vehicle launches due to high torque demands, particularly in hybrid or electric-only vehicles, which can lead to thermal de-rating and reduced performance.

Innovation Solution

A controller is implemented to limit torque generation by the traction motor before a vehicle launch, determining torque demand while the brake is applied, and removing the limit upon brake release, using pre-launch thresholds to prevent overheating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If high torque is applied by the traction motor during vehicle launch, then faster acceleration is achieved, but the traction motor and power electronics overheat

Engineering Contradiction:

Improveacceleration speedVSAvoidtraction motor temperature

Core Design Contradiction:

SpeedVSTemperature

Solution Approach 1:

The controller proactively limits torque generation by the traction motor before the vehicle launch condition is fully established (i.e., before the brake is released). By detecting when the brake is applied and torque demand increases, the controller preemptively applies a torque limit to prevent overheating, rather than reacting after thermal conditions deteriorate.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The controller applies a counteracting torque limit to prevent the harmful thermal effect before it occurs. By limiting the torque generation in advance during the brake-applied state, the system prevents the accumulation of excessive heat that would otherwise occur during high-torque stall launch conditions.

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If torque generation is limited before launch, then overheating is prevented, but acceleration performance is reduced

Engineering Contradiction:

Improvethermal protectionVSAvoidacceleration performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The torque limit is not applied continuously but dynamically activated only under specific conditions: when the brake is applied and torque demand increases. The controller dynamically adjusts the torque generation based on the operational state, removing the limit when the brake is released to restore full acceleration performance while maintaining thermal protection during the critical pre-launch phase.

Inventive Principle:

Principle #15Dynamics

3Duration of action of moving object

If high stall torque is held for long duration, then vehicle launch is achieved, but thermal de-rating activates reducing motor capability

Engineering Contradiction:

Improvelaunch preparation timeVSAvoidtraction motor power

Core Design Contradiction:

Duration of action of moving objectVSPower

Solution Approach 1:

The controller performs preliminary torque limiting during the brake-applied phase to prevent thermal conditions from reaching de-rating thresholds. By managing torque generation in advance, the system enables longer safe hold durations without triggering thermal protection that would reduce power capability during the actual launch.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12528366B2Control of vehicle traction motor torque before stall launch

Publication Date: 2026.01.20 JAGUAR LAND ROVER LTD

AI summary

A method for controlling torque generated by at least one traction motor of a vehicle before a vehicle launch includes: determining that torque demand increases while simultaneously at least one brake of the vehicle is in an applied state; in dependence on the determination, limiting torque generation by the traction motor in response to torque demand; and removing the limit in dependence on release of the at least one brake.