Electric Motor Rotor Angle Limits for Static Battery Heating

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Solution Overview

Problem

Existing methods for heating electric vehicle battery packs using the vehicle's electric motor risk generating knocking sounds and jerking due to unintended torque production, and separate heating elements add space and cost.

Innovation Solution

Determine rotor angle limits by applying brake torque-limited currents to an electric motor, monitoring rotor rotation angles, and adjusting currents to prevent torque production during static heating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a separate heating element is provided for the battery pack, then the battery pack can be heated reliably, but the vehicle design takes up space and adds cost and weight

Engineering Contradiction:

Improvebattery heating reliabilityVSAvoidvehicle weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The electric motor is designed to perform multiple functions: propulsion during vehicle operation and heating during stationary charging. The motor's stator and rotor structures are utilized for heating purposes, eliminating the need for a dedicated heating element and reducing overall vehicle weight and space requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The battery pack heating is achieved using the vehicle's own electric motor rather than an external or separate heating system. The motor converts electrical energy to heat through controlled current application, allowing the vehicle system to serve its own heating needs without additional components.

Inventive Principle:

Principle #25Self-service

2Device complexity

If the vehicle's electric motor is used to heat the battery pack, then space and cost are reduced, but knocking sounds and vehicle jerking may occur during stationary heating

Engineering Contradiction:

Improveheating system complexityVSAvoidknocking sounds and vehicle jerking

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

Before initiating the heating process, the system applies a brake to the wheel to prevent any unintended rotor movement. This preliminary action counteracts potential harmful effects by ensuring the rotor remains stationary throughout the heating process, eliminating knocking sounds and vehicle jerking that would otherwise occur.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system continuously monitors the rotor angle during static heating and compares it against predefined angle limits. When the rotor angle approaches these limits, the control system adjusts the current application to prevent exceeding the limits, thereby preventing unintended torque production and associated harmful effects.

Inventive Principle:

Principle #23Feedback

3Temperature

If current is applied to the electric motor for static heating, then the battery pack can be heated, but unintended torque production may occur causing vehicle jerking

Engineering Contradiction:

Improvebattery pack temperatureVSAvoidunintended torque

Core Design Contradiction:

TemperatureVSForce

Solution Approach 1:

The system applies a brake to the wheel before and during the heating process to counteract any unintended torque that may arise from rotor movement. This preliminary counter-action prevents the torque from causing vehicle jerking while allowing the heating current to be applied effectively.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The control system dynamically adjusts the current magnitude and direction applied to the motor windings based on real-time rotor angle measurements. By changing current parameters in response to rotor position, the system maintains heating effectiveness while preventing the torque thresholds that would cause vehicle jerking from being exceeded.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Prevents unintended torque generation during static heating, eliminating vehicle jerking and knocking, while optimizing space and cost by avoiding separate heating elements.

Implementation Method 1

providing a current to the electric motor for static heating

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS12558970B2Rotor angle limit for static heating of electric motor

Publication Date: 2026.02.24 ATIEVA INC(US)

AI summary

A method of determining rotor angle limits for static heating of an electric motor comprises: applying a brake to a wheel of a vehicle, wherein the vehicle has an electric motor; while the brake is applied, providing a first current to the electric motor to generate first torque not exceeding a brake torque limit of the brake; while the brake is applied, providing a second current to the electric motor to generate second torque, the second current being opposite, and about equal, to the first current; determining a first rotor rotation angle associated with the first current, and a second rotor rotation angle associated with the second current; and setting the first and second rotor rotation angles as first and second rotor angle limits, respectively, for static heating of the electric motor.