Electric Differential Drive Torque Control for Wheel Slip Limits

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Solution Overview

Problem

Existing differential drive arrangements in electric vehicles struggle to manage wheel slip effectively, particularly in uneven friction conditions, leading to potential wheel spin and reduced maneuverability.

Innovation Solution

A control unit with wheel slip control modules for each driven wheel determines obtainable torque based on current wheel state, adjusts torque requests to match the smallest obtainable torque, and employs service brakes to maintain wheel slip within limits, avoiding differential locking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a differential is used to allow different rotational speeds at driven wheels, then maneuverability during turns is improved, but wheel slip occurs on low friction surfaces reducing traction control

Engineering Contradiction:

Improvemaneuverability during turnsVSAvoidtraction control on low friction surfaces

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces the traditional mechanical differential locking system with an electrical control system. The control unit monitors wheel speeds and friction conditions, then selectively applies braking torque to specific wheels via service brakes to simulate differential locking behavior only when needed, eliminating the need for a mechanical differential lock while maintaining maneuverability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system dynamically changes the braking torque parameter applied to individual wheels based on real-time detection of friction conditions and wheel speed differentials. When low friction is detected on one side, the control unit increases braking torque on that wheel to prevent slip, while allowing normal differential operation under high friction conditions.

Inventive Principle:

Principle #35Parameter changes

2Power

If electric machines generate significant torque at low speeds, then propulsion capability is improved, but severe wheel slip occurs reducing stability

Engineering Contradiction:

Improvepropulsion capability at low speedsVSAvoidvehicle stability

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The control unit continuously monitors wheel speed, vehicle acceleration, and friction conditions to detect wheel slip. When slip is detected, the system provides feedback by reducing the torque request to the electric machine or applying service brake torque to the slipping wheel, thereby maintaining stability while preserving propulsion capability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary detection of wheel slip conditions and applies counteracting braking torque before severe slip occurs. By monitoring wheel acceleration and friction conditions in advance, the control unit can prevent wheel spin by applying brake torque to the affected wheel before loss of traction becomes significant.

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If differential locking arrangement is used to prevent wheel slip, then traction control is improved, but device complexity increases

Engineering Contradiction:

Improvetraction controlVSAvoiddifferential locking mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent eliminates the mechanical differential locking arrangement entirely and replaces it with an electrical control system that uses service brakes to achieve differential torque control. This substitution reduces mechanical complexity while maintaining or improving traction control through electronic monitoring and selective braking.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The service brake system acts as an intermediary between the control unit and the driven wheels. Instead of directly modifying the differential mechanism, the control unit uses the service brakes as a mediating component to apply corrective torque to wheels experiencing slip, thereby achieving traction control without complex mechanical modifications.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This approach efficiently manages wheel slip, enhances vehicle stability and maneuverability, and prevents wheel spin in varying friction conditions without the need for differential locking.

Implementation Method 1

Each service brake is controlled by a respective wheel end module to maintain wheel slip below a configured wheel slip limit

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS12576727B2Differential electrical drive arrangement for heavy duty vehicles

Publication Date: 2026.03.17 VOLVO TRUCK CORP

AI summary

A control unit for a heavy duty vehicle. The vehicle includes an electric machine connected to first and second driven wheels via an differential. The control unit includes a first wheel slip control module associated with the first driven wheel, and a second wheel slip control module associated with the second driven wheel, where each wheel slip control module is arranged to determine an obtainable torque by the respective wheel based on a current wheel state, wherein the control unit is arranged to determine a required torque to satisfy a requested acceleration profile by the vehicle, and to request a torque from the electrical machine corresponding to the smallest torque out of the obtainable torques for each driven wheel and the required torque.