Vehicle Behavior Control Device Understeer Suppression
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Solution Overview
Problem
Conventional vehicle behavior control devices fail to accurately control vehicle behavior during strong understeer tendencies caused by increased gross vehicle weight or tire aging degradation, as they do not account for these factors when adjusting driving force, leading to reduced cornering force and increased understeer occurrence.
Innovation Solution
A vehicle behavior control device that reduces and then increases driving force based on the understeer-causing state, specifically considering gross vehicle weight and tire aging degradation, to moderate the cornering force of front road wheels and suppress understeer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the driving force is increased to reduce load on front road wheels, then the cornering force is reduced and vehicle responsiveness improves, but understeer occurs more frequently when gross vehicle weight increases or tires age
Solution Approach 1:
The control device changes the parameter of driving force adjustment by introducing an understeer-causing state correction coefficient. When understeer is detected (through steering wheel angle change rate, lateral acceleration, or yaw rate), the system modifies the driving force reduction amount by multiplying with a correction coefficient greater than 1, thereby increasing the driving force more aggressively to counteract understeer while maintaining normal responsiveness when understeer is not present
Solution Approach 2:
The system implements feedback control by continuously monitoring understeer-causing states (steering wheel angle change rate, lateral acceleration, yaw rate) and adjusting the driving force accordingly. The correction coefficient is dynamically updated based on the detected understeer condition, creating a closed-loop control system that responds to actual vehicle behavior and prevents understeer occurrence
2Speed
If the driving force is reduced according to yaw rate-related quantity, then vehicle deceleration is generated quickly and turn-in ability improves, but the cornering force of front road wheels is reduced
Solution Approach 1:
The system dynamically adjusts the driving force reduction strategy based on real-time vehicle conditions. By introducing the understeer-causing state correction coefficient, the system makes the driving force adjustment dynamic rather than fixed, allowing the cornering force to be maintained or increased when understeer conditions are detected, while still enabling quick turn-in ability when normal conditions prevail
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 device effectively reduces cornering force in response to increased gross vehicle weight or tire aging degradation, thereby accurately realizing the intended vehicle behavior and suppressing understeer occurrences.
Implementation Method 1
a load is quickly applied to the front road wheels to cause an increase in frictional force between each of the front road wheels and a road surface and thus an increase in cornering force of the front road wheels
Data Source
AI summary
The vehicle behavior control device is designed to control a behavior of a vehicle having steerable front road wheels. The vehicle behavior control device comprises a PCM configured to perform control to reduce a torque for the vehicle according to a steering speed of the vehicle, and acquire an understeer-causing state of the vehicle which is a factor causing understeer, wherein the PCM is further configured to perform control to, after reducing the torque, increase the torque at a change rate decided based on the understeer-causing state of the vehicle acquired by the PCM.