Abstract
For passengers, the most common feeling during running on the bumpy road is continuous vertical discomfort, and when the vehicle is braking, especially the emergency braking, the instantaneous inertia of the vehicle can also cause a strong discomfort of the passengers, so studying the comfort of the vehicle during the braking process is of great significance for improving the performance of the vehicle. This paper presented a complete control scheme for vehicles equipped with the brake-by-wire (BBW) system aiming at ensuring braking comfort. A novel braking intention classification method was proposed based on vehicle braking comfort, which divided braking intention into mild brake, medium comfort brake, and emergency brake. Correspondingly, in order to improve the control accuracy of the vehicle brake system and to best meet the driver’s brake needs, a braking intention recognizer relying on fuzzy logic was established, which used the road condition and the brake pedal voltage and its change rate as input, output real-time driver's braking intention, and braking intensity. An optimal brake force distribution strategy for the vehicle equipped with the BBW system based on slip rate was proposed to determine the relationship between braking intensity and target slip ratio. Combined with the vehicle dynamics model, improved sliding mode controller, and brake force observer, the joint simulation was conducted in Simulink and CarSim. The cosimulation results show that the proposed braking intention classification method, braking intention recognizer, brake force distribution strategy, and sliding mode control can well ensure the braking comfort of the vehicle equipped with the BBW system under the premise of ensuring brake safety.
Highlights
Ride comfort is an important factor for the design of autonomous vehicles and intelligent transportation systems
As the future form of the brake system, the mechanical links between the brake pedal and the brake actuator are eliminated in the BBW system, which are substituted by electronic signals and control units. erefore, the BBW system has the characteristics of efficient and steady brake response, which is easy to integrate the advantages of other functional modules [4]. is advantage lays the structure foundation for improving vehicle safety and ride comfort
Because the change rule of four-wheel slip rate is the same, just taking the right-front wheel as an example, the wheel slip rate of the electromechanical brake (EMB) vehicle is steadily controlled by the sliding model algorithm at a specified value no matter which kind of road surface the vehicle is on, while the wheel slip rate of the ABS vehicle could not follow the road optimal slip rate. e acceleration of the EMB vehicle suddenly increases to − 0.58 g when the vehicle is on the dry asphalt pavement, which means it already has brought the mild discomfort feeling to the passenger
Summary
Ride comfort is an important factor for the design of autonomous vehicles and intelligent transportation systems. Ride comfort is affected by various factors, for example, vibration, sound, temperature, visual stimuli, and vehicle structure design. A great number of research studies have been conducted to improving ride comfort, in the field concerning ride uncomfortable feeling caused by vertical vibration, and a great deal of active and passive suspension control algorithms was put forward to improve the vertical vibration [1, 2]. We only concern one of the factors that influenced ride comfort in this paper, which is related to vehicle longitudinal dynamics. With the development of electronic control technology, the type of brake system is changing. As the future form of the brake system, the mechanical links between the brake pedal and the brake actuator are eliminated in the BBW system, which are substituted by electronic signals and control units. erefore, the BBW system has the characteristics of efficient and steady brake response, which is easy to integrate the advantages of other functional modules [4]. is advantage lays the structure foundation for improving vehicle safety and ride comfort
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