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To quantify the intensity of automobile brake creep groan, both experimental and analytical studies are innovatively conducted on the friction-induced vibration and noise of the disc brake in this paper. Experimentally, three factors, brake disc initial temperature, terrain, and gear position, are comprehensively contemplated to design six different test conditions, based on which a creep groan vehicle road test is conducted. Depending on the subjective evaluation and statistical analysis of the annoyance degree caused by vibration and noise in the starting and braking process under different test conditions, the influence of each factor on creep groan intensity is obtained. By processing the brake caliper and lower suspension arm acceleration and the interior sound pressure signals acquired in the test, the occurrence conditions and transient dynamic characteristics of creep groan are explored. One of the creep groan vibration modes is triggered by the rapid removal of the force exerted on the brake pedal when the vehicle starts at an extremely low speed, which presents intermittent impact and chaotic characteristics. The other vibration mode shows periodic harmonic characteristics, whose energy is concentrated on specific frequencies in the form of frequency doubling. This vibration mode occurs when continuously maintaining a low brake oil pressure or slowly releasing the force exerted on the brake pedal during the vehicle low-speed starting process, the velocity-displacement phase-plane portrait of which shows a stable limit cycle of stick-slip motion. Analytically, four vibration indexes and four noise indexes are established to evaluate the intensity of creep groan, the validity of which is verified by linear regression analysis. Finally, by combining all effective indexes, multiple linear regression analysis is performed, based on which the mapping relationship between the subjective evaluation of creep groan and effective indexes is obtained. The results demonstrate that the combination of the logarithmic vibration dose value of maximum brake caliper acceleration pulse and the loudness of interior noise can accurately describe the annoying degree caused by creep groan. The regression model can quantify and predict creep groan intensity of the test vehicle under different test conditions, which has guiding significance for engineering applications.

Environmental perception is a key technology for Advanced Driver Assistance Systems (ADAS) and Autonomous Vehicles, and thus a crucial prerequisite for traffic situation assessment and reasonable decision making. Sensor fusion can make full use of the characteristics of multi-sensors to achieve complementary advantages to improve the target recognition precision in various weather conditions. In this paper, a robust target detection algorithm based on millimeter wave (MMW) radar and camera fusion is proposed. Firstly, the images captured by the camera with low visibility in foggy weather are defogged. Then, the effective target is filtered by MMW radar, and mapped to the camera image to obtain the corresponding regions of interest (ROIs). Finally, the method of weighted is used to combine camera vision network recognition results with the radar target estimation results, and obtain the final result of the ROIs. The simulation results indicates that the detection precision through fusion of MMW radar and camera significantly outperforms that of single sensor.

The brake system of a passenger car is a complex system composed of an assembly of mechanical parts, such as springs and rubber parts, and structures filled with gas and other liquids. In order to predict the brake pedal feel of a passenger car, a dynamic model of a brake system during application of the brake pedal was proposed; this considered and modelled the physical structures and the working processes of the key components. The model takes into account not only the spring preloads and the frictional forces in the booster and the master cylinder but also the reaction disc features and the variation in the bulk modulus of the brake fluid. When the pedal travel is regarded as the input, the boundary conditions for the dynamic equations of the brake system components are strictly defined. Also, bench experiments for the booster and the master cylinders were designed for parameter identification; the effectiveness of the component models was validated under conditions including with and without vacuum assist and with and without brake fluid. On the basis of these experiments, the static and dynamic characteristics of the brake pedal feel were simulated using the static model and the dynamic model of the brake system. Then, vehicle road experiments were carried out. With the assessment index of a three-quadrant diagram covering the pedal travel, the pedal force and the master cylinder pressure, as well as a four-quadrant diagram covering the pedal travel, the pedal force, the master cylinder pressure and the longitudinal deceleration of the vehicle, the results from the simulations and the experiment were compared and analysed. We conclude that this novel model of a brake system can accurately predict the brake pedal feel characteristics of passenger cars and can be used for brake system design and adjustment.