EV Direction-Change Torque Control During Gear Shifting

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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 with regenerative braking to maintain a constant total braking torque by individually controlling the braking torques of each motor, allowing smooth gear shifts without mechanical brakes, ensuring the most suitable gear is used in each direction.

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 it causes unwanted stand still period and torque loss

Engineering Contradiction:

Improvevehicle stopping speedVSAvoidstand still period

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The patent replaces the mechanical braking system with an electrical braking system using electric motors. The electric motors are controlled to provide braking torque through electrical means, eliminating the need for mechanical brake engagement and the associated standstill period. This substitution allows for smoother deceleration and eliminates torque loss during the transition phase.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements dynamic control of electric motor braking torque during the direction change process. The control system continuously adjusts the braking torque of individual motors based on real-time vehicle state, enabling smooth deceleration without complete stop. This dynamic adjustment allows the vehicle to transition from forward to reverse motion without a full standstill, reducing the time loss.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If the vehicle shifts gear during direction change, then the appropriate gear can be selected for each direction, but it requires the vehicle to stand still for approximately 1 second

Engineering Contradiction:

Improvegear selection for different directionsVSAvoidgear shifting time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The control system performs preliminary gear shifting actions while the vehicle is still moving at low speed, rather than waiting for a complete stop. By anticipating the direction change and initiating gear shifts during the deceleration phase, the system eliminates the 1-second standstill requirement. The electric motor braking allows precise speed control during this transition, enabling seamless gear changes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent maintains continuous useful action by keeping the electric motors in braking mode throughout the entire direction change process, including during gear shifts. Instead of stopping the vehicle completely, the motors continue to provide controlled braking torque, allowing gear shifts to occur during motion. This continuity eliminates idle time and maintains vehicle momentum control throughout the maneuver.

Inventive Principle:

Principle #20Continuity of useful action

3Loss of energy

If the vehicle uses regenerative braking for deceleration, then kinetic energy can be recuperated into batteries, but the braking torque control becomes more complex

Engineering Contradiction:

Improvekinetic energy recuperationVSAvoidbraking torque control

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent divides the braking function into separate controllable units - individual electric motors. Each motor can be independently controlled to provide or absorb braking torque, allowing flexible distribution of braking load. This segmentation simplifies the overall control strategy by treating each motor as an independent braking unit that can be activated or deactivated based on real-time requirements, making the complex regenerative braking system more manageable.

Inventive Principle:

Principle #1Segmentation

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 mechanical brake wear, provides a smooth direction transition, and enables kinetic energy recuperation into batteries, enhancing the driving experience and vehicle performance.

Implementation Method 1

setting the first and second electric motors to regenerative braking mode

Methodology Applied

Scientific EffectRegenerative braking: Electromagnetic Induction

Data Source

PatentEP4644163A1Control system and method for avoiding torque loss during changing moving direction of electrical vehicle

Publication Date: 2025.11.05 VOLVO TRUCK CORP

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Figure 3(a)~3(b)

AI summary

A control system (110) and method for controlling torque and gear shifting during changing moving direction of an electrical vehicle (100) are provided. The control system (110) determines that a change of direction is requested and gear shifting is needed when the vehicle (100) changes direction. The control system (110) sends a control signal to a motor controller (130) for decelerating the vehicle (100) 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 (Tt1). When the speed of the vehicle (100) has been reduced to a predetermined speed, the control system (110) sends control signals to the motor controller (130) for controlling one motor (121, 122) 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.