Differential Limiting Control for Four-Wheel Drive Turning
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Solution Overview
Problem
In four-wheel drive vehicles, differential limiting between front and rear wheels can lead to under-steering and reduced turning performance due to increased rotational speed differences caused by slipping, which existing technologies fail to adequately address.
Innovation Solution
A differential limiting control apparatus that corrects the rotational speed difference between front and rear wheels based on the difference between target and actual rotational speed differences, specifically subtracting half of the rotational speed difference between the right and left wheels to minimize the influence of slipping on differential limiting, thereby optimizing power distribution and preventing under-steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If differential limiting force is increased between front and rear wheels to restrain slipping, then slipping restraint is improved, but under-steering is furthered and turning performance lowers
Solution Approach 1:
The patent dynamically adjusts the differential limiting force applied between front and rear wheels based on the detected rotational speed difference between right and left wheels. When a large rotational speed difference is detected (indicating slipping), the control device reduces the differential limiting force between front and rear wheels to prevent under-steering, while simultaneously increasing the differential limiting force between right and left wheels to restrain slipping. This parameter change resolves the contradiction by adapting the force distribution to the specific slipping condition.
2Reliability
If differential limiting force is applied between right and left wheels to restrain inner wheel slipping, then slipping restraint is improved, but rotational speed difference between front and rear wheels increases causing under-steering
Solution Approach 1:
The patent applies a counteracting control strategy where the increase in differential limiting force between right and left wheels is compensated by a corresponding reduction in differential limiting force between front and rear wheels. This counterbalancing approach ensures that the harmful effect of increased rotational speed difference (under-steering) is offset by reduced front-rear limiting force, while the beneficial effect of slipping restraint is maintained through enhanced right-left limiting force.
Data Source
AI summary
Restraining torque TF of an electronic controlled front limited slip differential (5) arranged between right and left front wheels is controlled in accordance with controlling right-left wheel rotational speed difference ΔNF, which is the rotational speed difference between the right and left front wheels, while restraining torque TC of an electronic controlled coupling (8) arranged between the front and rear wheels is controlled in accordance with controlling front-rear wheel rotational speed difference ΔNC obtained by subtracting ½ of the rotational speed difference between the right and left wheels (|ΔNF|/2) from the rotational speed difference (ΔNCT−ΔNCD) between the front and rear wheels.