Rear-Wheel Drive Torque Control for Front Wheel Load

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Solution Overview

Problem

Rear-wheel-drive vehicles do not achieve improved responsiveness and linear feeling in vehicle behavior when applying deceleration-based control methods, as the force transmission through the suspension causes a tilt that reduces load on front road wheels, unlike front-wheel-drive vehicles.

Innovation Solution

A vehicle control system and method that adjusts torque settings based on steering angle and pedal mode, increasing incremental torque during steering to enhance load on front road wheels, and differentiates torque settings between acceleration and deceleration modes to maintain responsiveness and linear feeling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If deceleration-based control is applied to rear-wheel-drive vehicles, then vehicle stability is improved, but responsiveness and linear feeling of vehicle behavior deteriorate

Engineering Contradiction:

Improvevehicle stabilityVSAvoidresponsiveness of vehicle behavior

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The patent inverts the conventional deceleration-based control approach by applying acceleration-based control to rear-wheel-drive vehicles. Instead of reducing driving torque to improve stability, the system increases driving torque in response to steering input, which generates an instantaneous force that tilts the vehicle body forward and increases load on front road wheels, thereby improving both stability and responsiveness simultaneously.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the control parameter from deceleration to acceleration. The control device calculates a target acceleration based on steering angle and adds this acceleration to the vehicle's current acceleration, thereby adjusting the driving torque to produce the desired vehicle body tilt and improve steering responsiveness in rear-wheel-drive vehicles.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If driving torque for rear road wheels is reduced to give deceleration, then vehicle stability is improved, but load on front road wheels is reduced

Engineering Contradiction:

Improvevehicle stabilityVSAvoidload on front road wheels

Core Design Contradiction:

Stability of the object's compositionVSForce

Solution Approach 1:

Instead of reducing driving torque to improve stability, the patent increases driving torque in response to steering input. This generates an instantaneous force that tilts the vehicle body forward, thereby increasing the load on front road wheels and improving steering responsiveness while maintaining stability.

Inventive Principle:

Principle #13The other way round (Inversion)

3Speed

If incremental torque is increased to improve responsiveness, then load on front road wheels is increased, but energy consumption increases

Engineering Contradiction:

Improveresponsiveness of vehicle behaviorVSAvoidenergy consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The patent applies partial action by calculating incremental torque based on steering angle and adding it to the basic torque only when steering input is detected. The control device determines a target acceleration proportional to the steering angle and applies this acceleration-based torque adjustment selectively, rather than continuously maximizing torque, thereby improving responsiveness while controlling energy consumption.

Inventive Principle:

Principle #16Partial or excessive action

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

The system effectively improves responsiveness and linear feeling in rear-wheel-drive vehicles by increasing load on front road wheels through incremental torque adjustments, even in single pedal mode operations, ensuring better cornering performance and vehicle control.

Implementation Method 1

a force is instantaneously transmitted from the rear road wheels to a vehicle body via a suspension such that it causes the vehicle body to be tilted forwardly

Methodology Applied

Scientific EffectForce transmission: Mechanical Force

Implementation Method 2

when the driving torque for the rear road wheels is increased to give an acceleration to the vehicle, an inertial force causing the vehicle body to be tilted rearwardly is generated

Methodology Applied

Scientific EffectInertial force: Inertia

Data Source

PatentUS11198471B2Vehicle control method and system

Publication Date: 2021.12.14 MAZDA MOTOR CORP

AI summary

The present invention provides a method of controlling a vehicle (1) in which rear road wheels (2b) are driven. The method includes: a step of selecting a first pedal mode in which an acceleration is set based on a depression amount of an accelerator pedal, or a second pedal mode in which the acceleration and a deceleration are set; a step of setting a basic torque based on a driving state of the vehicle; a step of setting an incremental torque to allow the basic torque to be increased in accordance with an increase in steering angle; and a step of generating a torque which is determined by adding the incremental torque to the basic torque, wherein the incremental torque setting step includes setting the incremental torque to different values between when the first pedal mode is selected and when the second pedal mode is selected.