Dual-Motor Braking Torque Control During EV Direction Changes

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Solution Overview

Problem

Electric vehicles experience torque loss and an unwanted standstill period during direction changes, especially when shifting gears on hills, due to the need for mechanical braking and mismatched gear requirements in different directions.

Innovation Solution

A control system and method that utilizes two electric motors for regenerative braking, individually controlling their braking torques to maintain a constant total braking torque during gear shifts, allowing smooth direction changes without mechanical brakes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the vehicle uses mechanical brakes for stopping during direction change, then the vehicle can be braked to stop, but torque loss occurs and an unwanted standstill period is created

Engineering Contradiction:

Improvevehicle stopping speedVSAvoidtorque loss

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent replaces the mechanical braking system with an electrical braking system using the electric motor as a generator. The motor converts kinetic energy into electrical energy during deceleration, eliminating the need for mechanical friction brakes and preventing torque loss through regenerative energy recovery.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent converts the harmful effect of kinetic energy dissipation during braking into a beneficial effect by using the electric motor to generate electricity from the vehicle's motion. This regenerative braking process transforms energy that would normally be lost as heat into usable electrical energy for the vehicle's battery system.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Adaptability or versatility

If the vehicle shifts gear during direction change, then the appropriate gear can be selected for the new direction, but a standstill period of approximately 1 second is required

Engineering Contradiction:

Improvegear selection for directionVSAvoidstandstill period

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent performs gear shifting operations during the deceleration phase before the vehicle comes to a complete stop. By initiating gear changes while the vehicle is still moving and maintaining rotational momentum, the system prepares the transmission for the new direction without requiring a full standstill, thereby reducing the time loss.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent maintains continuous rotational motion of the electric motor throughout the direction change process. By keeping the motor spinning and the transmission engaged during gear shifts, the system eliminates idle standstill periods and ensures uninterrupted useful action, allowing smooth transition between directions.

Inventive Principle:

Principle #20Continuity of useful action

3Ease of operation

If the vehicle uses the same gear for forwards and rearwards motion, then direction change can be done smoothly without standstill, but different gears are needed for optimal performance on hills

Engineering Contradiction:

Improvesmooth direction changeVSAvoidperformance on hills

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The patent implements dynamic gear shifting during the direction change process. Instead of being locked into a single gear for both directions, the system automatically selects and shifts to the most appropriate gear based on real-time conditions such as slope, speed, and power requirements, enabling both smooth operation and optimal performance.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the gear ratio parameter during direction change to optimize performance. By adjusting the transmission ratio according to the specific driving conditions (such as hill gradients and speed requirements), the system achieves both smooth directional transitions and high productivity on varied terrain.

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

This approach avoids torque loss and standstill periods, enabling efficient kinetic energy recuperation and improving the driving experience by using the most suitable gear in each direction.

Implementation Method 1

setting the first and second electric motors to regenerative braking mode

Methodology Applied

Scientific EffectRegenerative braking: Electromagnetic Induction

Data Source

PatentUS20250340129A1Control system and method for avoiding torque loss during changing moving direction of electrical vehicle

Publication Date: 2025.11.06 VOLVO TRUCK CORP

AI summary

A control system and method for controlling torque and gear shifting during changing moving direction of an electrical vehicle are provided. The control system determines that a change of direction is requested and gear shifting is needed when the vehicle changes direction. The control system sends a control signal to a motor controller for decelerating the vehicle and controlling a braking torque of each electric motor individually to a level such that a total braking torque is at a first predetermined level. When the speed of the vehicle has been reduced to a predetermined speed, the control system sends control signals to the motor controller for controlling one motor at a time to ramp down braking torque to shift gear, and the other electric motor ramp up braking torque such that the total braking torque is maintained constant during gear shifting.