Introduction

In recent years, vehicle stability control systems have become one of the most important safety technologies in modern automobiles. Among these systems, Electronic Stability Control (ESC) is one of the most widely recognized technologies. By intelligently applying braking forces to individual wheels, ESC helps the vehicle remain on the driver’s intended path and prevents skidding or loss of control, particularly during cornering and sudden maneuvers. This research investigates the performance of ESC based on this intelligent braking strategy.

In contrast, Active Front Steering (AFS) improves vehicle stability without using brakes by automatically adjusting the steering angle. One of the main advantages of this approach is that it does not reduce vehicle speed. However, when tire-road adhesion approaches its physical limit, the effectiveness of active steering becomes increasingly limited.

Therefore, researchers have focused on developing solutions that allow these two technologies to operate together, ensuring that each system intervenes at the appropriate moment and provides the best possible performance in terms of vehicle stability, handling, and driving comfort.

The Main Challenge: When Should Steering or Braking Intervene?

When both active steering and electronic stability control systems are installed on a vehicle, the most important question is determining when each system should take action.

In many previous approaches, this decision was based on fixed control parameters. As a result, the system sometimes activated braking too early, causing unnecessary vehicle speed reduction and discomfort for passengers. On the other hand, delaying braking intervention too much could result in insufficient vehicle stability during critical situations.

Some studies have attempted to improve this decision-making process; however, many existing methods still cannot accurately determine whether steering correction or braking intervention is more effective at a specific moment. Consequently, the coordination between these two systems is not always optimized.

Proposed Research Approach

This research proposes a new control strategy based on Model Predictive Control (MPC).

The main idea behind this approach is straightforward: as long as active steering alone can maintain vehicle stability, braking intervention is unnecessary.

The decision is made based on the remaining force capacity of each tire. In simple terms, the system evaluates how much additional force each tire can still generate to maintain vehicle balance and stability.

If sufficient tire force capacity remains, only active steering is used. However, when this capacity approaches its limit, the system intelligently introduces braking assistance.

This strategy ensures that braking is applied only when it is truly required. In addition to improving vehicle stability, it prevents unnecessary speed reduction and provides smoother and more comfortable driving performance.

To accurately simulate tire behavior under realistic driving conditions, the advanced UniTire model was used for vehicle dynamic analysis.

Control System Operation

In this method, the system first calculates the expected vehicle trajectory and behavior based on the driver’s steering input.

The controller then determines how much path correction should be achieved through active steering and, when necessary, how much braking force should be applied to each individual wheel.

These calculations are performed continuously in real time within fractions of a second, allowing the vehicle to remain in the most stable condition possible.

The main objective of the controller is to ensure that the vehicle follows the driver’s intended path precisely, without causing sudden or uncomfortable changes in steering or braking behavior.

Simulation Results

The researchers evaluated the performance of this approach using MATLAB/Simulink and CarSim under three different driving scenarios.

The results demonstrated that as long as active steering alone was capable of maintaining vehicle stability, the system avoided unnecessary braking. Only when the driving conditions became more critical did braking assistance become active.

Compared with conventional control methods, the proposed controller achieved:

• Improved vehicle stability and path tracking performance
• Prevention of unnecessary braking interventions
• Reduced vehicle speed loss
• Smoother steering response
• Reduced vehicle oscillations during aggressive maneuvers

In a sudden lane-change test, the vehicle equipped with this control strategy showed significantly better handling performance compared with both vehicles without stability control and vehicles using conventional control methods.

Conclusion

The results of this research demonstrate that improving vehicle stability does not only depend on the simultaneous use of active steering and intelligent braking systems. More importantly, it depends on accurately determining the appropriate timing for activating each system.

The proposed approach evaluates the remaining tire force capability in real time and decides whether active steering alone is sufficient or whether braking intervention is also required.

This strategy not only enhances vehicle stability but also reduces unnecessary speed loss, improves handling performance, and increases passenger comfort.

However, the authors emphasize that this method has so far only been validated through simulation environments. Further experimental testing on real vehicles is required to confirm its practical effectiveness.

Reference

New Integrated Vehicle Stability Control of Active Front Steering and Electronic Stability Control Considering Tire Force Reserve Capability
DOI: 10.1109/TVT.2021.3056560